Agreed, but I'm concerned that humans being humans, we'll have the entire solar system to blow ourselves over.
In The Expanse (which I highly recommend), they give a new lease on life to that quote attributed to Einstein "I know not with what weapons World War III will be fought with, but World War IV will be fought with sticks and stones" - hurling asteroids towards a planet. I really hope humanity's real future will play out in accordance with some of the more optimistic elements in The Expanse.
It's always funny seeing people pretend they live in a world where small issues like land or food don't affect them, even though they only have that privilege because a larger military says they should.
Stage 1 sucessfully caught. That was pretty incredible. I remember watching the Falcony Heavy launch when both boosters landed in sync.
It's hanging pretty high in the air, I assume so the engines do less damage to the pad. One wonders how they're going to get it down. Do the chopsticks lower on the tower?
Yes, the chopsticks lower and raise. They will lower the tower onto a transport vehicle and send it back to the bay for examination, and then possible reflight.
They'll lower it to the launch mount... the catch arms are effectively a crane. But I wonder if it's more "toasty" than they were expecting? There were some fires going at catch (those look out, at least on external camera views) and the engines are still a bit.... smokey. Don't know if that's normal... or if they were expecting it.
My hunch is that they don't put it down for awhile. If there's still an issue were there are fires lingering inside, my hunch is they want that as far from the ground infrastructure as possible.
The fire I mostly saw was coming from the quick disconnect ports and related plumbing. Also, there was fire on the other side, close to where there was part of a chine was clearly missing. There were a couple other things, too.
Wasn't perfect, some things to work out... but still pretty damn good.
Remember on the first launch when, on the way up, there were hydraulic units exploding off the side and the engines started exploding taking out more hydraulic units? Heh that and all the concrete flying up on ignition was like watching a heavy metal music video.
There was a lot of smoke coming out of the bottom after the catch. I was worried about an internal fire but it’s since stopped. The glow from the engine mount on re-entry was amazing. The fire on landing had me worried too I was expecting it to grow but put itself out eventually.
An additional advantage is that it’s theoretically possible to make fuel for Starship on Mars. The Luna lander will need to bring enough fuel for the return trip.
I'm just so happy to see this level of progress. This another big step for opening up space. To think that one day this will be considered normal. 150 Metric tons sent on a fully reusable rocket.
Is that 150t of payload or total? What’s the cost in fuel alone (let’s ignore maintenance and operations costs for now)? I’m trying to get a feel for the relative scale compared to today’s commercial flight.
They previously threw around a number of around $1M per flight, as mostly fuel costs.
Also, while 150t is the target payload capacity, the current test vehicles are closer to 50t in payload capacity, there are revisions in the pipeline based on data from these test flights which will bring it up to 150t.
To put this in perspective: at 150t/launch, if a launch is $1M, then for the cost of an SLS launch (at least $2B) Starship could launch 300,000 tons, about the mass of three Nimitz-class nuclear aircraft carriers.
None of the vehicles have demonstrated any payload capacity yet. 50 tons is the on-paper capacity only, and seems quite high given how little fuel is left when the bring an empty starship to orbital altitude. I assume that as the engines and launch procedures get more efficient, they will start being able to bring stuff to orbit (and quite a bit of stuff, too).
They've actually been having to dump propellant in order to more accurately test what a Starship in orbit would be like, given they're not flying with a payload that would consume that propellant on ascent, but that they still want to launch with a full tank.
The dumping of this excess propellant actually caused an explosion and loss of vehicle on the second test flight.
That's what they said about the second test flight (and the third), but the webcast recordings looked a lot more like fuel leaks to me, and that is in line with Starship and early Falcon's past issues. I'm going to press X to doubt that the dumping narrative is the truth, since a nice face-saving white lie is in every corporation's handbook.
That's a weak rebuttal. It's not disputed except by the lunatic fringe - starship has carried a payload (although not quite to orbit, very close to).
Whatever that means is what it means, the ship was out of control and I don't know whether or not the mission requiring that payload was successful, but the fact is that it did carry the payload.
Methane is about 900-1500$ / ton. About 1000 tons is used for the launch in addition to 3600 tons of lox. That should be a bit cheaper than methane per ton. Ballpark, the propellant might cost around 2M$.
A modern airliner on a long flight might burn around 80 tons of kerosene. It's slightly cheaper than methane. Call it 75-80K$.
Indeed. You sometime see an argument that launch to space is expensive because of the propellant and therefore energy required. And as you note this argument is utterly wrong.
Am I mistaken, or are there distance/payload combinations for which Starship is cheaper per pound on a point-to-point basis than air transport, even setting aside 30 minutes versus 12 hours? Isn't that the non-intuitive outcome of ballistic trajectories?
No. But it gets within an order of magnitude, which is remarkable. Economy class on starship could be priced similar to first class tickets on transoceanic flights.
There are no dollars in the laws of physics. It's connected ultimately to productivity of all the activities involved, and there's no obvious upper bound to productivity.
Just the current market price for fossil methane, which of course goes up and down. But I'm assuming SpaceX gets their methane on the open market.
It's quite possible that SpaceX has access to some cheaper methane source. Texas produces a lot of it.
And SpaceX has speculated about eventually switching to some renewable source by e.g. synthesizing methane. In which case that would boil down to cost of electricity and carbon. I don't see that becoming cheaper short term but that could happen long term.
So, reusable is supposed to reduce the cost. But the space shuttle was reusable and it has been shutdown because it was too expensive. What is the differences between the two?
Beyond the fact that they eventually did quit, the shuttle program was the public face of the US space program, and part of having more than one way to launch military stuff.
The military rapidly gave up on the Shuttle after the first accident. No shuttle was ever launched from the pad on the west coast at Vandenberg (plenty of F9s have been, though.)
They were but the cost of refurbishment was almost more than just building new boosters. Thats why SLS is currently using Shuttle Derived Boosters but not worrying with reuse.
Percentage of reusability: boosters of shuttle cannot be reused, maintenance of shuttle itself is also very expensive (heat shields were pricey). whereas the starship stack has higher reuse percentage and allegedly cheaper to maintain.
The shuttle was not even reusable by any modern metric, the main tank was always expended, the boosters had to be recovered, fully disassembled and cleaned.
I'm not even sure the SRM case segments could be easily reused, given the tremendous stress. They were made of a very high strength steel (maraging steel, with a yield stress of something like 250,000 psi) operated with a safety factor of 1.4.
the space shuttle was "reusable". It had to be taken apart and meticulously cleaned and tested and basically had to be rebuilt after each flight, in a process called turnaround. SpaceX's rockets are much closer to what you'd consider reusable.
I wonder how much of that difference is because the space shuttle was human rated from the start: F9 eventually got there, but only after plenty of "testing in production" with disposable payloads.
The other big difference, an elephant in the room grade difference I think, is that SpaceX reliability was developed with memories of a reusable vehicle failing mostly due to turnaround costs and risks on everyone's minds. That clearly wasn't the case when the space shuttle was designed, they were the first and enjoyed the privilege of making all the beginner mistakes.
I had an email exchange with Homer Hickam, before SpaceX existed, where I remarked that the shuttle design looked like a giant kludge, and a winged reentry vehicle was a fundamentally bad design, for various reasons which I enumerated elsewhere in this thread.
He emailed back that he agreed with my reasons and had argued that case with NASA in the early stages of the shuttle program.
I was under the impression tha they also thought this themselves but got "persuaded" with the prospect of more money if it could handle certain payloads of use for defense?
The case for the Shuttle was so marginal they needed every prospective customer they could get. The military was dragged into it unwillingly, but did give their requirements when forced to commit. They backed out as quickly as possible after the Challenger disaster.
Think of the word ‘reusable’ in this case as less a binary descriptor but more of a scale of reusability.
Yes, both systems are reusable, but there are key differences in the refurbishment of the systems that partly explains the cost difference. It took more labor, resources and time to refurbish the shuttle. Also consider rapid reusability was a stretch goal when it was being designed, but we have come a loooong way since, spacex in particular has had it as a driving competitive differentiator for years now.
Another big difference is that NASA post Cold War was a skilled jobs program, with an incentive to do distributed, high overhead work to appease their bosses (congress), while SpaceX has the opposite.
> Yes, both systems are reusable, but there are key differences in the refurbishment of the systems that partly explains the cost difference. It took more labor, resources and time to refurbish the shuttle.
Starship uses essentially the same ceramic heat shield tiles as the Space Shuttle, so the fact the Shuttle had so much trouble with refurbishment doesn't mean that SpaceX has solved these refurbishment issues with the Starship upper stage.
Though the Starship lower stage, which contains the most expensive engines, doesn't have this problem. Since it doesn't need a heat shield. So partial reusability should be pretty realistic.
Shuttle's tiles were each unique. Starship is mostly clad with identical hexagonal tiles which can be mass produced and eventually refurbished by machine. A robot already welds on the tile fittings.
More of an ignorant assumption. I asked ChatGPT now, and got this:
> In terms of shapes, the tiles were not uniform. In fact, there were over 17,000 different shapes used to fit specific areas of the shuttle's body. Each tile had to be individually manufactured and shaped to fit a precise location due to the complex curvature of the shuttle's surface. The unique shapes were necessary to ensure that every part of the shuttle received the proper protection against the extreme temperatures during re-entry.
Please don't cite LLMs for factual questions. They are prone to confabulation. Why not type the question "How many heat shield tiles did the Space Shuttle use?" into Google?
Since I mentioned I got the info from ChatGPT, people can decide for themselves how much they trust it.
Note that the question here is how many uniquely shaped tiles there was, not the total number.
This is interesting because if you have to manufacture and keep in stock 17,000 separate tile shapes, that will be vastly more expensive than SpaceX who, from what I hear, only uses a singe hex shaped tile everywhere.
The tiles are very similar; the attachment system is very different (a big part of why Shuttle's were a pain to maintain) and Starship's simple shape means most of the tiles are the same (the ridiculous number of SKUs was another factor in Shuttle TPS costs).
The main difference is that this is built by a private corporation who can't afford to throw money away, while the Space Shuttle was build by the government, and moreover it had to fulfill a number of conflicting requirements, and commercial profit was not one of them.
But on a more technical level. I think the vertical landing is the main difference. Vertical landing was obviously known and done by NASA, this is how the lunar modules landed on the Moon. But doing it on Earth, with vehicles weighing hundreds of times more, I don't think the world had that technical readiness a few decades ago, when the space shuttle was designed.
And another major difference is the mass manufacturing idea. From the start SpaceX planned for getting to mass manufacture its rockets. The Falcon rockets are much cheaper than any other alternatives even if you remove the reusability.
Then it's the methane burning engines. This was pure old fashioned engineering progress. SpaceX's engines are miracles of rocket engineering. Aside from that, the fuel choice is extremely smart. Methane is better than all other fuels, except for hydrogen. Hydrogen was the fuel of the space shuttle, but it's very tricky to work with. It has very low volumetric density, so the tank of the space shuttle was absolutely humongous. Hydrogen needs to be stored at an absurdly low cryogenic temperature, so this adds to the complexity. And that tank was not reusable, so it adds to the cost.
Spacex might be a private company, but this project is funded by NASA, meaning the American taxpayer. Approved by a person whose last act was this approval before leaving NASA and joining Spacex (effectively putting money in their own pocket).
It is also yet to be seen how Starship will ever be profitable (outside of spending government money), who is going to pay for those launches and for what purpose. Other than Starlink, of course.
The problem is that launch costs went down fast but satellite costs haven't gone down as fast and still have long development timelines. The other problem is the market for satellite services hasn't developed as fast as anticipated, except for starlink.
Starlink for all intents and purposes is the market for satellites now. All the other launches are nice to have extras.
Now personally I’m looking forward to NASA, ESA and JAXA to launch outer solar system probes like new horizons but with tons of fuel left in the tank to safely make orbit around there.
Having enough lift capacity to take a shot at putting a pair of telescopes out far enough to exploit solar gravitational lensing to resolve exo-planet surfaces would be a hell of a thing. Orbital refueling would mean we could reasonably build something big enough to be able to boost out that far (would still take decades to arrive).
Things can only be cheap if you mass produce them. That tends to require standardization of components, and inevitably standardized components are a compromise between requirements, where up until now, saving mass was a critical requirement. If you don't have to care nearly so much about mass and volume, then that opens up many avenues for much cheaper standard satellite components.
The whole design process for them is based around launches being expensive and taking a long time to plan. It will be very interesting to see what happens when the whole process gets used to launches being relatively cheap and frequent. No need to spend years making sure the design is perfect and will definitely last a long time if you can launch a new one in a week if you make a mistake.
Partially. They have a fixed-price contract to land humans on the Moon, and notably got that contract because they severely undercut the other bids and were the only bid that actually fit within the available budget: they bid $2.94B, while Blue Origin bid $5.99B and Dynetics $9.08B.
That 3 billion is also much less than what they're spending on the project.
Exactly. Private companies like space X would not exist if NASA didn't deliberately make the market for Private space companies. That's what governments do, make markets.
With a payload volume of 8m diameter by 22m height you could fit a James Webb size telescope inside with minimal folding. The sunshield (21.2 m by 14.2m) would only need to fold along one axis and the mirror (6.6 m) could be monolithic instead of having to fold, probably only requiring the mounting points for the primary and secondary to be hinged. This shouldn't be discounted because it makes telescope design much simpler and less expensive.
It also allows for launching individual space station modules that have almost the same volume as the entire ISS in one launch.
Their plans for refuelling on orbit with tanker versions of the starship open up the entire solar system to unmanned missions with much shorter timelines and much higher payload size and weight.
The fact the entire system is re-usable will make it both cheaper and faster to use than any other launch system.
All of this combined mean that it won't just be countries and space programs bidding for space on launches, it puts space within reach of many corporations and some private individuals. This isn't conjecture, it's already happening with the Falcon 9. Starship will make it even more accessible.
Just park the starship as the sun shield. Or two starship, or an origami starship that unfolds for more surface area, your own personal sun umbrella made from a starship.
About 10% funded by NASA. Starship is a >$10B program; SpaceX is getting $3B for Artemis of which >2/3 is for operational tasks and moon-specific stuff that SpaceX aren't relevant for SpaceX's goals of LEO and Mars.
Its high cost would (should!) have killed it regardless, but its low reliability was going to be a huge problem too, and arguably it's the lack of reliability that finally killed it.
The high cost should have killed the project before it ever flew, but that's not how governments behave.
In order to land as a glider, you'll need wings, landing gear, doors, rudder, stabilizer, flight controls, streamlining, all the structure needed to support it, and a heat shield for all of it. All that complexity has to work reliably, too.
All of that adds tremendous weight, complexity, and cost.
I did the math, and the impact is not negligible. One single launch releases the equivalent of 5000 tons of CO2. Elon wants to get to the point where there are thousands of Starships, each doing a few trips to orbits per day. That would be more than one millions launches per year, or more than 5 GT of CO2-equivalent. That's about 10% of the worldwide emissions today.
One million launches per year seems to be adequate trade for 10% global emissions. This level of technology implies we are able to reduce emissions elsewhere.
I think it’s ludicrously optimistic to think that this would substitute for reductions elsewhere. What possible
mechanism could reduce 10% of global co2 emissions when many of these launches will be tourists and starlinks?
1 million launches per year implies at least a decade or two of development. There is a lot that can change in that time - for example energy production can move towards renewable and nuclear. Few decades more and we might get fusion too.
The limiting effect for Starship launches won't be CO2 (direct air capture could counter that), it's injection of water into the stratosphere. Ballpark I think the limit would hit at about 100,000 launches/year.
Yeah, methane is kind of second best (or worse) in many parameters, but most importantly, it's cheap, abundant, and easily and safely storable and transportable, and it does the job.
And while not the reason, also on Venus! Venus seems like a very interesting colonization target - gravity almost like on Earth, and there is a place in Venus atmosphere where temperature is around 30 degrees Celsius and pressure is 1 atmosphere (Earth); and human air is a lifting gas in Venus atmosphere. As a bonus, interaction of Venus atmosphere with the Sun produces a magnetic shield.
Staying in orbit means risk of catastrophic failure on puncture and doesn't provide access to the heat of lower layers of Venus atmosphere that can be used as energy source or carbon source. You also have to think about heat management - big colony means gigantic radiators. And most importantly no gravity and no magnetic shield - these make Venus imho better colonization target than Mars.
On Venus, a puncture doesn't immediately destroy anything - because of equal pressure on each sides of the balloon wall. You have more than enough time to put on a protective coat and fix it.
And building more living space is much easier + you could source the material (carbon) on site.
It is a very daunting problem no doubt, maybe the hardest one, but I also don't doubt that the end form of Starship will require way, way less than 20 000 man-hours per turnaround (as the Space Shuttle required) to refurbish the heat shield. They simply cannot afford that.
Manufacture and maintenance contracts for the Shuttle were deliberately spread out across many companies and states, especially in key congressional districts. It was a jobs programme; waste was a feature not a bug.
More fundamentally, there were contracts. SpaceX does things itself; there's no legal friction internally. This gets back to the "Theory of the Firm" for why firms exist in the first place (transaction costs).
The need to codify what work is to be done in contacts is antithetical to SpaceX's rapid development processes.
SpaceX builds vehicles. The Shuttle was “reusable” because they needed a term between the default for transportation capital expenditures (e.g. trains, planes, cars and ships) and the modified missiles that defined post-War spaceflight. “Reusable” in the Shuttle’s context meant months of specialist overhaul time and the cost of a Falcon 9 launch in SRB booster replacements alone [0].
At the end of the day, in 2010, “the incremental cost per flight of the Space Shuttle was $409 million, or $14,186 per kilogram” [1]. ($591mm and $20,512 in 2024 dollars, respectively [2].) SpaceX’s prices per kg are around $3,170 on Falcon 9 [3] and $1,520 for Falcon Heavy [4]. Starship should bring those costs below $1000.
It might, but it's also at a scale where people can dust off the old plans for orbital rings and ask if this time the economics work out.
(My guess is the economics are fine, but the politics would kill it on earth, so the moon or mars will get one, but that's just an interested amateur opinion).
IIRC, above something like geostationary they tend to decay upwards? Though the old orbital ring white paper wasn't suggesting anything like that, this was an alternative to needing to go so high in the first place.
(I may be misremembering or getting confused with a thing specific to tidal locking?)
I wonder if they could have an orbit high enough to move away from earth with some kind of drag cables dangling from them into low orbit to counter the outward movement. Would that work?
These orbits have vastly different speeds though. Consider a high geosynchronous orbit vs. something like ISS which goes around the Earth in an hour or two.
but you are towing the cable and you'd only get so far down for the counteraction of force from gravity to pull on the cable. Would speed or friction on a cable be a problem.
That is indeed what you get with tidal forces - bodies closer than geostationary orbit lose angular momentum and decay inward, bodies further out steal angular momentum from Earth and move outward.
I suppose the same effect is there with satellites much smaller than the moon, but it would be tiny.
Term of art for this is "design for demise", i.e. make everything of pieces small enough and materials ablative enough that there's less than 1 in 10k chance that any debris will survive to the surface.
Presuming it’s in LEO. When and if we ever get around to building these things they probably won’t be in LEO at least not for long. Some of them might not even be constructed from materials launched from Earth.
The Shuttle consisted of the shuttle (orbiter) itself, the external tank (not reusable), and the two boosters which could be reused after ocean recovery. The orbiter itself was slow and expensive to reuse since (among other things) all the heat shield tiles were inspected and 30-100 replaced between each launch. I don't know how much work was done to the engines between launches, but SpaceX's parts and cost reduction on the Raptor engine have to give it an advantage there.
StarShip consists of the Super Heavy booster that we saw "caught" today, and the StarShip (orbiter) itself. Having the booster return to launch site vs requiring ocean recovery should potentially increase cadence and reduce cost of reuse. StarShip is also meant to be reusable, although it remains to be seen how that will pan out. On the previous flight there was burn through from inadequate heat shielding - maybe we'll see an improvement with today's vehicle. I'd expect SpaceX to iteratively arrive at a quicker and more cost effective orbiter reuse procedure than NASA had with the shuttle, but how quick remains to be seen. Of course they are planning many of these to go on one-way trips to Mars rather than being reused.
> The orbiter itself was slow and expensive to reuse since (among other things) all the heat shield tiles were inspected and 30-100 replaced between each launch.
Worth noting that Starship's heat shield is very similar to the one of the Shuttle. They actually got the manufacturing method from NASA.
That's why I remain very skeptical about the easy refurbishing of Starship. Initially, way back around 2016, the plan was to vent liquids to create a cushion around the ship. That sounded more easily reusable.
Yeah. I think they originally planned to use ceramic tiles only for certain spots and still transpiration cooling for the rest. Then they fully switched to ceramic tiles. In an interview with Everyday Astronaut on YouTube, if I recall correctly, Elon Musk said they first believed the ceramic tiles to be lighter.
Falcon 9 has already proven that partial reusability is economical. SpaceX has dominated the entire worldwide launch industry and their competitors are nation states with no need to make a profit.
The difference is that they have already proven to be the lowest cost and most reliable launcher due to reuse. This is them lapping the industry with second stage reusability.
Shuttle itself was refurbishable, but not rapidly re-usable. It was also incredibly expensive to build and refurbish. A shuttle launch also utilized boosters that were not re-usable.
Starship is supposed to be (and clearly well on the way to being) fully rapidly re-usable. That means all stages (in this case two) are re-usable, and that the capital and time required to get either stage flight ready again after a flight should be minimal.
Said another way – it is cheaper for SpaceX to build an entirely new Starship + Booster than it was to refurbish a Shuttle between flights, by a factor of about 4x ($90M for a Starship+Booster / $400m for Shuttle refurb).
The boosters for the Shuttle were reusable, but it turned out the cost of refurbishing them was similar if not higher than simply building new ones. Plus it contributed to the Challenger crash, see "Mr. Feynman Goes to Washington", https://calteches.library.caltech.edu/3570/1/Feynman.pdf
You've got a lot of responses on the difference of reusability, but the shuttle was also more expensive because it had to carry a lot of capabilities with it every time. If you were launching a satellite, you were carrying along the crew compartment and a couple astronauts. If you were bringing a few astronauts to the space station, you brought a cargo bay. And in either circumstance, you brought big wings. Starship can be filled with all cargo. And if you're just changing crew on the ISS, you could... not use Starship and launch a Falcon 9 instead. One of the mission profiles required by the Air Force for the shuttle was that it be able to rendezvous with a satellite, put it in the cargo bay, and return to Earth, all under 2 orbits and along a path that avoided flying over the Soviet Union, which required a rather large turn in-atmosphere to make it back to landing on the west coast.
One of the drivers was the need to Abort Once Around on a polar orbit launch from Vandenberg. The launch site rotates to the east during the orbit so cross range was needed. No such polar orbit launch (abort or otherwise) ever occurred, though.
To answer this oversimplified question with a simple answer, the Space Shuttle couldn't be a more different vehicle than this one. It truly is a comparison between apples and oranges.
Let's start with the fact that it was designed in the 1970's. If you had a Cadillac DeVille from 1970 it would get 8-12 miles per gallon. Just the mere fact that the design is about 70 years old makes that vehicle too expensive to operate, and that's before we even start talking about other issues with the design (performance, safety, reliability, etc).
The Space Shuttle was not fully reusable as the biggest single part, the orange tank, was destroyed every time. But more importantly, the orbiter and boosters needed 2+ months of refurbishment/rebuilding after every flight.
One of the design goals of Starship is for the booster and ship to relaunch with zero refurbishment. To literally land over the launchpad, refuel, and go back to orbit within hours without people even approaching them. The heat shield is the biggest risk to that goal IMO, and we saw today that it definitely sustained serious damage despite improvements. But if they ever get there then per-launch costs will be a tiny fraction of the Shuttle with 6x the payload.
The majority of damage to shuttle's TPS apparently came from foam strikes from the external fuel tank. Superheavy's optimized profile certainly helps here, since there are no large cryogenic tanks hanging ominously over the TPS while being shaken violently by solid rocket boosters.
No one has answered with one of the biggest issues with the shuttle: each one was extremely custom. Every single heat shield tile was unique to a specific position and a specific shuttle. There were probably over a hundred million individual components in the Shuttle, and with many critical ones being custom, the time to refurbish it for a new launch was much longer.
This is in contrast to something like the falcon, which has a very standardized mfg process and components, which allows for really rapid iteration
The shuttle wasn't fully reusable, just for starters. The boosters were reusable with a lot of refurbishment work. The center tank was expended every time. It was very expensive. Only five shuttles were ever made, which means that no effort was put into automation of production of engines etc., everything was custom, and everything required great care to save the sunk costs.
Because people are reflexively averse to government spending unless there's a billionaire making profits on the way through thanks to 100 years of academic capture by Austro-libertarian economists.
Reusability increases costs if you don't reuse often enough.
The shuttle would have been much, much, cheaper per launch if it had flown more often. The expected costs for the shuttle included a range based on how often it flew which turned out to be reasonably accurate. They were much worse at predicting which end of the range they would be flying in. At the rate they ended up flying they had the extra costs of reusability without any of the benefits.
Starship is ludicrously expensive, but still much cheaper than even the best case for the Shuttle, and it has a guaranteed source of launches to help it benefit from resuability.
The turnaround time for Shuttle was 2-3 months, while building a brand new rocket takes like 1-2 years. Although for the cost of Shuttle, we could have built a whole bunch of expendable rockets, pipelined with a regular launch cadence, and probably also gotten some cost savings through economies of scale.
Estimated costs of the fully loaded cost of the shuttle program ended up at $600 million to $1 billion per flight. The refurbishment costs per flight and man hours/staffing were astronomical.
It actually would have been a lot cheaper if they had gone for serialized, mass assembly line production of Saturn V class disposable rockets to launch piece of space stations, satellites and manned missions into low earth orbit.
The main thing is... Space shuttle wasn't all that reusable. It had to be launched with a massive rocket and two massive boosters that just fall into the ocean.
SpaceX took advantage of tech from both the US and Russia, including the experience with the Space Shuttle. They have better computers, better metallurgy, advanced 3D printing and their own experience with the Falcon 9.
There is no guarantee that it will reduce the costs that much, but will all that experience, the chances are success are higher than with the Space Shuttle.
One big issue that isn't talked about much and that SpaceX takes very seriously is simply a lack of demand. There is only so much stuff you want to put in space. Satellites are expensive, and even with disposable rockets, the launch is only a smaller fraction of the cost. It is already a problem with the Falcon 9 as they have a bunch of rockets and not much to do with them. Starlink, orbital refueling, and crazy ideas like earth to earth transport are all ways to address this problem.
It was a problem for the Space Shuttle too, they couldn't achieve the economies of scale they planned it for. It was supposed to fly for routine maintenance missions but it didn't work out.
Falcon 9 is still the most advanced rocket flying real missions to date. The only thing close to it is Blue Origin, which didn't even have their maiden flight yet.
Is their timeline too optimistic? Yeah, but if the industry still catches up with F9 and they are close to having something a lot more advanced it really doesn't matter.
Even without reusability nothing comes close to Starship's cargo capacity. If you don't have to put a lot of engineering into getting things as small and light as possible you can put things in space a lot faster.
And, eventually, if it becomes cheap enough to put people in space for the task, you can plan to actually maintain things there rather than design for extreme reliability.
That was crazy, 50% of me thought as it was coming in, especially as it pitched towards the tower, "they've overcompensated and are going to bring the whole tower down" but they absolutely nailed it.
Even without the catch step, I always feel like their boosters are coming down way too fast way too late, with engines reigniting startlingly close to surface. Never ceases to surprise me.
Yeah, it also always catches me off guard how late they reignite, while at the same time I'm always surprised by how slow the liftoff is even though all the boosters are on full throttle. Of course both things make sense given the respective mass at both points in the process, but given that it looks like the same rocket from the outside, a bit unintuitive.
I have the same feeling watching Starship when the telemetry on the bottom right of the screen showing “0km” but landing burn hasn’t started. Later did I know that it was meant to start the burn only a few hundreds _meters_ from the ground
Prior to today the only landings you've seen are Falcon 9, which has to do a "hoverslam" because it can't throttle low enough to actually hover.
Even just one engine in minimum thrust would make the rocket go up when empty.. so the computer lights the engine at the precise right moment so it will have 0 velocity at 0 altitude, then it cuts off the engine. "Hoverslam".
The Starship booster is different, it can actually hover.
Every moment your engines are burning at anything less than maximum thrust, you are wasting fuel. You want to relight as late as possible with as high thrust as possible for maximum efficiency. But that it actually works is nuts.
The higher the thrust, the lower the gravity losses. Gravity losses go down as you approach orbital speed but they aren't zero until you're in orbit. And when boosting out of orbit, the higher you are the less benefit you get from the Oberth Effect, so you want to do the burn before you rise too much, which implies sufficient thrust.
Exactly. In addition, by delaying the relight as long as possible you're giving drag as much time as possible to do the work for you (assuming you're not at terminal velocity, so not applicable for the ship.)
The math is pretty intuitive; every second you're burning is another 9.8 m/s of delta V you have to spend counteracting gravity instead of slowing the craft down (minus air friction) so minimizing deceleration time cuts your fuel expenditure massively. It also means you have to carry less fuel so you weigh less and you spend less fuel for the same acceleration. It's the inverse of the rocket equation really, less mass is easier to slow down and you waste less energy (ie fuel mass) decelerating faster.
I remember playing KSP, I had used some mod to program a moon lander to do a suicide burn, a maximum thrust burn to land. I did the maths myself and when it actually came to the landing I was 100% certain I had either a bug in my code or did the math wrong because I was coming in way too fast, or so it seamed, but to my surprise the thing slowed down in time!
Mind you ksp is way simpler than the real world and the spaceship could handle some… error, the landing was hard but successful
Point is it always seems like you’re coming in too fast
Naive question: I obviously expect there to be flames from the engines, but there were flames on the lower sides for quite a while after the catch – is that expected?
There’s a bunch of people crapping on you who clearly haven’t been through a flight test campaigns.
100% with you. The teams I’ve worked with would be celebrating and trying to figure out what’s burning at the same time. And especially trying to figure out if there’s anything that they need to do to collect evidence for that investigation (eg zooming the remote PTZ cameras in on specific areas or things like that)
Just to be clear, I never suggest that the teams actually working on this wouldn't look into it. I was talking about people who were watching and were happy.
Isn’t this a forum of hackers caring about the news? Everyone seems excited here and that excitement naturally leads into curiosity for many who identify as hackers.
It does look like venting, but on the Everyday Astronaut video feed it also looked like a COPV inside one of the strakes looked like it exploded as well.
If not an intended vent, probably some methane leak. Given that they have the first stage intact, they will know exactly what happened very soon. Yet another advantage of having the rocket returned instead of sinking it in the ocean.
It is common for Starship prototypes to have uncontrolled fires, but it is obviously not a good thing.
For example, prototype number 10 exploded 8 minutes after landing [1] because of a seemingly insignificant fire at the bottom.
After today's flight there was a long lasting fire in the engine section, with occasional flaming pieces of plumbing raining down from the rocket. Examining the aftermath should help SpaceX to understand what improvements need to be made to prevent this from happening.
This highlights another thing I love about watching SpaceX's unprecedented rate of progress. They're managing the complex balance of risk, learning, time and budget extremely well. I'm not an expert in the relevant domains but even I've noticed and appreciated that the typical SpaceX development test always manages to get big chunks of new data, while still having some notable things not quite working.
It's an object lesson in rapid engineering development. If everything goes perfectly in a development test, it's a sign you're not moving fast enough (meaning not taking enough risk per increment to maximize learning). As valuable as Falcon, Starlink and Starship are, the biggest near-term value of SpaceX may be providing such a clear demonstration of well-executed "fail fast, learn fast" engineering that even politicians and bureaucrats can understand it.
Maybe the flare on the side started as purposeful. But there was also a fire inside, between the engines, with flaming pieces of some pipes or cables raining down from the rocket. You can see one example of this just after this timestamp: https://youtu.be/YC87WmFN_As?t=12928
They have mission goals which were achieved (booster was caught). Goals that they didn't think they could do (Starship being within the buoys). While there was flames and those could be dangerous you judge the mission based on the planned outcomes but they will try to eliminate the anomalies to improve the next mission while still achieving the goals.
The thing is that no one is judging the mission based on this imperfection. It's just intellectual curiosity, which is a good thing. The comments that are getting down voted are all assuming some negative motive that just isn't present.
It looked to me like the fire was on the fuel intake valves and if you watch carefully that area was scoured by the nozzle output when it was first slowing down so it probably blew through the shutoff valves or something
I wonder what will happen when they get to 99% reliability? They clean up and rebuild the Mechazilla every once a hundred catches, on that occasion that one fails?
I suspect there's already a whole "refurbishment" process for the crane even for non-reusable launches, and once it's working darn reliably, they can just have a bunch of them ready to go, and cycle once in a while.
The booster aims towards the shore until the landing burn starts, only then does it swing towards the tower. So, for the most part, failures should mean that the booster safely crashes into the water.
It's difficult to overstate how important the milestone of catching the booster is. Now we have a reusable rocket an order of magnitude larger than anything we've had before, and the cost of kg to orbit just nosedived.
I'm not sure how critical "catching" the booster is to reusability, but it does save weight by not needing legs for landing, and perhaps the booster suffers less stress this way?
Note that the booster is not really being "caught" although this is the word it seems we're stuck with. It's really more like landing on the arms, since it throttles to a hover at that point.
I think saving weight is definitely one of the main issues, see those proportionally large legs on Falcon-9, I guess it simply doesn't scale on bigger vehicles like Starship / Heavy booster. Also, by catching the booster on site, they can even save the transportation and do the refurbishing on site, so even shorter turnaround time I guess.
> I'm not sure how critical "catching" the booster is to reusability
Not necessarily for reusability, but it helps significantly for rapid reusability: it eliminates the need to transport the booster from the landing site to the launch site. Given that it's 9m x 70m and weighs 270 tonnes, that's not an easy process.
Second stage reuse seems the far more challenging problem. Other companies should have reusable boosters soon but if significant amounts of Starship continue to ablate on the way down they could be faced with a disposable Starship competing with smaller and cheaper second stages that are well sized for typical payloads. We already knew boosters can be flown back to launch sites reliably with high accuracy. We don't know if it is possible to make rapidly reusable thermal protection systems that can operate on an orbital vehicle of Starship's size until it is demonstrated.
Didn’t they look at all kinds of ideas earlier like squirting some propellant or water out over the skin on the way down, and wasn’t steel chosen for its thermal robustness? Did they get into the problem and realize it’s a lot harder and abandon those things for tiles?
Maybe they will have to sacrifice more payload mass for active or passive shielding or more fuel for powered deceleration. That would yield a less impressive lifter but with full reusability.
Yeah for rapid reusability tiles aren’t going to work, too fragile. Iirc it was with a lot of reluctance they went with tiles and will have to make breakthroughs on the heat shielding to get where they want to be.
They already plan refueling infrastructure in orbit. That would include stuff to "squirt" on the way down if necessary. If they can use one extra launch to reuse 5-10 starships that might be interesting. Noone knows yet if it's actually needed.
Interestingly, the inside surface of a rocket nozzle is covered with tiny holes. Fuel is circulated in a jacket around the nozzle both to pre-heat the fuel and to cool the nozzle. Additional cooling of the nozzle comes from fuel leaking into the combustion chamber through those holes, carrying away the heat so it doesn't melt the nozzle. It's called boundary layer cooling.
It was one of the technological breakthroughs of von Braun's team with the V2.
> Other companies should have reusable boosters soon
You're way too optimistic. Starship will deliver commercial payloads, with SpaceX phasing out Falcon 9 outside of ISS launches, before anyone has a reusable Falcon 9 equivalent.
It pains me to say this, but SpaceX is in a class all its own.
SpaceX couldn’t manage the first Falcon 9 landing until 2015. The first Falcon 9 reuse wasn’t until 2018, so 3 years to achieve reusability. The Chinese prototype hasn’t yet succeeded at sub-orbital landing. I wouldn’t be surprise if it’d take them longer than 3 years to have a reusable rocket. Starship would have been routine at that time.
Blue Origin plans to launch New Glenn in a month, with landing planned. They are a wild card.
I’m not saying they stole the plans through industrial espionage, I’m just wiggling my eyebrows suggestively while glancing in the direction of the suspiciously similar looking booster.
I promise you the fancy technology is in the electronics, software, and implementation, and not the fact that the cylinder with legs looks like another cylinder with legs
Chinese startups have historically been the only ones to be able to move as fast as Musk. One very underrated ability of Tesla is they can develop new products in 2-3 years from conception to market. The only other car companies to do it at scale is BYD, Nio and Xpeng. The company he is talking about is probably LandSpace. They got from conception to hop test in what seems to be 5, maybe 4 years. SpaceX took 7.
I think China has about 5 companies working on reusable launch and it is part of a national government strategy. People can argue about the timeline but it is inevitable.
New Glenn finally has flight hardware undergoing pre-flight testing. I think they're pretty likely to manage to fly in early/mid 2025, and they do aim to recover the booster in their first try.
I think it pains some of us to say it because of the person Musk has turned out to be, which is the opposite direction I think many of us were hoping his character development would take him.
It was more than a slight. Biden pointedly ignored Tesla when conducting an EV summit and handing out subsidies. Then there was the FCC fiasco where the FCC snubbed Starlink.
> Then there was the FCC fiasco where the FCC snubbed Starlink.
You mean that time that the FCC removed Starlink from the broadband problem when they couldn't deliver the speeds that they had committed to, as defined very explicitly in the program?
Musk has never, no matter what he claims, ever a progressive democrat. He would be at best, someone who believed in the liberalization of certain drug policies. His economic beliefs have always been max pro business (aka, hands off, anti labor). He solidly fits under libertarian like the rest of the tech billionaires. Republicans, if it weren't partly driven by Christian fundamentalists, would be libertarian. The conservative GOP party of the 70's hasn't existed in decades.
I think that is only part of it. Musk gave an interview where he talked about how the woke medical establishment trans'd one of his kids. They falsely told him to do the transition or his child's death was a near certainty. European countries are now restricting this "treatment" for children. The US has been slow to follow. There is a lot of money and political pressure from the left to keep the medical intervention industry alive.
Are you aware of what you're doing: you're removing agency from that person who transitioned. They're abundantly public about how their transition was appreciated and needed. Do you ultimately care more about the feelings of your own dad over yours?
Trump may well win this election. But there’s no scenario under which he’s going to also win the popular vote while doing it, at least none that I’ve heard of. If you have credible information that says otherwise I would be interested in reading it.
Absolutely false.
Trump got 74M votes in last election in 2020. US population was 330 millions.
Today US population is ~340M.
I seriously doubt that more than 170M people support a convicted felon for president.
I bet that he will get less than 170M votes in less than a month.
Do you want to take the other side of the bet to back up your provably wrong assertion?
Using ableist language on Hacker News, however, is alright? I dislike Elon too, but this comment feels a little out of place and date, especially for the point it's trying to make
Someday in a land far away people would be mature enough to spot complexity instead of judging people as purely "right" or "wrong". I think the best way to explain Elon is... he is a complicated individual and has some really good parts and some really not so good parts. And you know what, that is just fine.
This manufactured, polarized "us vs them" thing on the internet is toxic corrosive goop. People are complex and that is fine.
A few things that I (as someone who doesn't follow Twitter) have heard about from anecdotes and from the news about why people dislike him:
- He called some guy who worked for him a pedo for no reason, which he was sued over
- Took over Twitter and promoted right wing tweets to everybody, unbanned far right accounts and sued critics who said he did so
- Started promoting far right ideas, like when he retweeted "Interesting" to some tweet of a 4chan post saying that high-status, high-testosterone males are the only ones who can think freely and should be the only ones who can vote
- Took the side of the right-wing rioters who attacked mosques in the UK, saying civil war is inevitable
- Just seems to insult companies for little reason - advertisers who leave him, and Apple
There has been kind of a slow back and forth. Some people who liked him were miffed about the pedo thing, but they didn't hate him. But he has just kept doing things that some people hate.
> Took the side of the right-wing rioters who attacked mosques in the UK, saying civil war is inevitable
Leave out the part where the riots were started because someone with an immigrant background killed a bunch of kids at a Taylor Swift concert and police were withholding the identity. Along with your other 'anecdotes', can you make your political position any more transparent?
I see I accidentally came off implying that I'm disaffected and take no sides - most of the time, right wing politics seems abhorrent to me. Those are the main things I remember because left-wing spaces tend to hate him, and I dislike him because of those things, but no more than CEOs of companies like Nestle, which has engaged in things like slavery and child trafficking.
> because someone with an immigrant background killed a bunch of kids at a Taylor Swift concert and police were withholding the identity.
It might be somewhat justified if they burnt the house down of the murderer, or those who assisted him. They didn't - they burnt down houses, shops, and mosques, because they wrongly assumed the guy was Muslim and decided that was just cause to target any Muslim. His identity was hidden because he was a minor at the time of the attack.
No it isn't. It might be soon in some early way: "the first launch is expected to take place no earlier than November 2024", "The booster for the flight is named So You’re Telling Me There’s a Chance, alluding to the difficulty of landing a reusable booster on the first attempt." -- https://en.wikipedia.org/wiki/New_Glenn
I found Jeff’s Bezos interview with everyday astronaut really illuminating on this topic.
Supposedly they’re working on both a reusable and cost optimised non-reusable second stage at the same time. And they don’t really know yet which one will end up being cheaper.
You also see this kind of thinking with Rocket Labs neutron rocket. Where they focus on making the reusable booster do more, while making the second stage smaller, cheaper and simpler.
I think if it wasn’t for the rocket engine this wouldn’t be a question at all. The tank doesn’t have much value. It’s just a thin shell and probably a fraction of the cost of the fuel.
So I’m thinking, perhaps the optimal solution is something like this: the bottom part of the second stage with the engines separates, and a small engine and fuel tanks places the engines in a stable orbit. The tank itself is deorbited and burns up.
At some point later something like the Starship collects several second stage engines and deorbits them safely to be reused.
Or perhaps just the engines can be immediately deorbited with an inflatable heat shield and parachutes.
> Second stage reuse seems the far more challenging problem.
Sure, SpaceX has been doing first stage reuse for a long time now. But they have demonstrated landing the second stage successfully at sea twice now with the same sort of smoothness that they demonstrated once for the booster before they then caught the booster on the first real try.
A partial list of unbelievably hard things that SpaceX has so far made seem easy:
- building a rocket from scratch
- landing Falcon 9 boosters
- landing Falcon 9 boosters *reliably*
- 3x weekly launch cadence (Falcon)
- the bellyflop manoeuver
- mass manufacturing(!) a rocket engine
- catching the booster
- simulated landings of the ship
Catching the booster is really just like landing a Falcon 9 booster w/o legs, but clearly much harder.
Anyways, if they can do all those things then it's pretty clear that they can catch-land the ship.
There's still a huge list of crazy-difficult things that SpaceX say they want to do that are hard to believe are possible, except for the fact that SpaceX has already done so many unbelievably difficult things already.
I would say they are there. Sure, they're having some burn through on the flaps, but they managed to hit their virtual landing spot anyways, and if they caught a slightly damaged ship they could study that damage better, repair it, and refurbish the ship.
But I imagine that by IFT6 they'll have nailed the flap burn through problem.
They can't have burn through like that and achieve the kind of rapid reuse Starship needs to be useful outside low to mid Earth orbit, to go outside of there it requires a large number of flights to refuel the one Starship that will go on to Moon/Mars. Without the ability to refuel for Moon or beyond trips Starship is trapped in LEO/MEO because it's hauling around so much extra mass for it's own reusability.
IMO a better use for it might be to ferry up large pieces of purpose built craft with less excess dry weight. A single reusable Starship launch can put the entire mass of the Apollo craft needed to make it from LEO to the Moon and back into LEO. Put a craft in two launches and dock it in orbit and you've got a huge capability to put a lot of mass onto the moon and still use the cheap cost to orbit Super Heavy gives.
They have a history of pursuing solvable problems and abandoning those that were not working out or had better alternatives. Parachute recovery of the booster was abandoned in favor of propulsive landings. Catching fairings was abandoned for water proofing. Proposed Falcon and Dragon variants were abandoned as was Dragon propulsive landing. They abandoned carbon fiber construction and multiple concepts for Starship/Heavy.
The tiles in combination with ablative materials and the insane robustness of a steel vehicle is sufficient to get Starship through re-entry and soft land in the ocean. We know ceramic thermal tiles worked on Shuttle and X37B and presumably will on Dreamchaser so while the success was an awesome achievement it wasn't unlikely given time to refine their methods.
SpaceX are limited by the properties of real materials, not their ambitions, and we still don't know if rapidly reusability is possible with ceramic tiles or if their fragility will require inspections and refurbishment. They can't do it with ablatives and there aren't many other options. I am optimistic but also realistic about the difficulties of what they are attempting. Sometimes risky projects run into brick walls and you don't know what is possible until you try.
If the ceramic tiles aren't working out, I think they could try transpiration cooling (previously planned for Starship) or a metallic heat shield (was planned for VentureStar). Or some combination. There seem to be quite a few options.
They landed an earlier version of the second stage on the ground a few times as well. It's the atmospheric reentry from orbital velocity that currently necessitates the safety of a splashdown: they're not going to risk bringing a damaged and potentially uncontrollable vessel down over land, even if they could nail the landing with an undamaged ship.
They're still having some significant burn through problems on the upper stage fins during reentry it looks like. Way better than last time but the top part of the fin was glowing far a while after the main reentry finished.
Maybe. Kind of impossible to know until we see launch costs but you could make a much cheaper upper stage than they have if you wanted disposable. Trick with that is you need a payload heavy enough to justify it. Has SpaceX talked much about a disposable upper stage version of the system?
Nothing could have prepared me for how that catch looked. I was sure the rocket was careening into the tower at the last second before it straightened out. The control algorithms must be incredible for the landing system to work within those small tolerances.
I certainly can explain it, I'm just not sure I can do it in a way that you could understand. If you yell me what's one of the greatest things you have seen and why, I might be able to better relate.
Very cool :) I got a good enough score in the basic scenario by playing around a bit but it would be cool if you could link some kind of tutorial (e.g. to a digital PID video or something like that).
MIMO and nonlinear control theories are probably some of the hardest topics in all of engineering. SpaceX control system also has to compensate for the fuel moving inside their rockets so the control algorithms probably involve some kind of fast numerical fluid simulation.
Another interesting thing SpaceX is doing is to use consumer-grade chips in triple redundancy configurations instead of using $100,000+ radiation-hardened aerospace/defense grade chips.
I always thought the liquid sloshing would be one of the hardest to simulate (considering how chaotic fluid mechanics is). Interestingly, I think this caused the 2nd Falcon launch to fail (the LOX sloshing).
It is difficult, but there are modeling approaches that work, such as VoF (https://en.wikipedia.org/wiki/Volume_of_fluid_method). Basically, in addition to velocity, pressure, temperature, etc., you store an additional scalar in each cell of your computational mesh representing the liquid's volume fraction. Then, you solve an additional equation to transport that scalar.
Solving the Navier-Stokes equations numerically in 3D is very time-consuming, even on HPC clusters, not to mention the additional modeling required for multiphase flows. Your answer implies that the solutions are obtained almost instantaneously, which is not the case.
Maybe the tank is just not a large hollow structure but contains fins/compartments/whatever to restrict the sloshing motion and it's not that big a contribution to the overall motion.
If it's no stronger than a sudden wind gust, it's just something the controller has to be able to take care of without a heads-up.
I remember a very similar anecdote about Von Braun & the early Juno/Jupiter rockets - with someone pointing out issues with sloshing on a press conference & Von Braun brushing it off as insignificant.
Then the next launch crashed due to slosh induced oscillation - and the one rocket after that had anti-slosh baffles. ;-)
I think the reason these kind of simulations are fast enough is because they are very coarse and approximate. Don't think of asking how exactly the foam swirls around the individual longerons, more like a very rough estimation of which side of the tank the liquid is slumped to. Remember it doesn't have to be "exact" just close enough to be useful.
By their very nature model predictive controllers operate in a world where not everything is perfectly modelled. Engineers do their best and whatever is left is the "error" the controller is trying to deal with.
Maybe they don't need to model the fluid dynamics, they just need to detect the mass movement / acceleration forces caused by it, and use those sensor inputs to inform a picture that's fed into their correction thursting.
Sort of like how you can balance a few pitchers of beer on a tray in your hand by remaining aware of the weight, even when people remove one! hahaha :)
Still if there indeed is "free" mass moving about, you need to make sure your control inputs don't make it slosh harder, so you compensate for that, so it sloshes even harder, etc - basically avoiding oscilation. :)
They don't need to solve the Navier-Stokes equations, they don't care how the fluid is actually behaving, they just need to approximate how the mass is moving within a margin of error that the control system can handle.
Oh no, apologies if that was the impression I gave!! I actually perform CFD simulations in HPC clusters, and in fact I'm an admin of the small cluster at my research institute =)
These are indeed heavy computations. What I meant is that VoF is one additional equation to be solved besides the N-S equations (either filtered as in LES or Reynolds-averaged as in RANS), the energy equation, your turbulence model equations, and so on. Certainly, not instantaneous at all, but simply an additional "simple" model that we can hook into our current way of doing CFD.
So, my point was, sloshing is a problem that we know how to simulate, although certainly you need HPC resources. Though, looking at those 100k NVIDIA H100 Elon has, I guess they have them! :P
It really depends on the problem to be solved (domain size, complexity of physical phenomena such as turbulence model, heat transfer, acoustics, multiphase flows, combustion, etc., number of time steps required...). In our case we perform for instance simulations of turbomachinery acoustics that can take 3-4 weeks running in a few hundreds of CPU cores, combustion acoustics simulations that can take a week or two running in 1k-2k cores...
I think some Kerbel Space Program players have attempted to approximate the liquid sloshing as an inverted single or double pendulum problem inside the rocket that the control algorithm has to take into consideration in addition to the primary control of the rocket.
At least for the retro-propulsive landing burn, I think the modeling problem is probably aided by the high G-forces that must keep the fuel very close to the bottom of the tank. Even before re-light the booster is falling near terminal velocity (I think?), so the fuel is likely sitting at the bottom.
I think it's a huge problem when re-lighting the engines in orbit, though.
Also IIRC the massive main tanks in Super Heavy should be basically empty at landing & the landings propelants come from a set of small header tabks that are near the central axis of the vehicle & arr completely full. This should reduce or even fully remove sloshing issues at landing time.
Has it been considered to spin the fuel via some centrifuge mechanism as a way to remove sloshing from the equation, or is that more complex/expensive/error-prone than just predicting it via simulation?
I'm thinking we will eventually end up with "active fuel management" techniques like this for in space vehicles.
Bug tanks make sense there & they might not be always full. So I can imagine all kind of interesting ways you can work with the fuel in zero go to avoid not only slosh but also the need for ullage thrusters. Eq. some programmable nozzles using in-tank gas to nudge liquid fuel blobs to move in the right direction. Or even some nets or bags that herd in the fuel in the middle of the tank + prevent it from directly touching the side, reducing boil-off or refrigeration requirements. :)
Less than 5% of a full load. Any extra fuel you brought to the edge of space and back is lost performance, so substantial efforts are made to minimize this lost mass fraction.
I never thought of using fluid dynamics in the rocket stabilization algorithm—maybe it's something that could be useful to prevent many of the accidents involving liquid-transport trucks
Interestingly cheap redundancy is also how life does things for the most part. Most biological organisms just replicate a lot to guarantee success, so it's clearly a good strategy and an efficient use of energy.
> Another interesting thing SpaceX is doing is to use consumer-grade chips in triple redundancy configurations instead of using $100,000+ radiation-hardened aerospace/defense grade chips.
This has been known in the high availability and safety systems industry for a while and a good book to learn these reliability engineering techniques is "Reliability Evaluation of Engineering Systems".
One downside of using non-rad hard parts is degradation from TID (gamma) and latch up effects. You can have chips monitoring other chips to reset whenever they latch up but TID is mostly permanent. The good thing is that TID in LEO, where SpaceX mostly operates, is relatively lower than GEO so they can get by with mostly commercial parts. It's not like the big defense contractors haven't figured out the same thing, they do fly stuff using commercial parts as well, they are just slower to adopt the same culture. SpaceX and the companies that built components using commercial parts are building the new-space industry.
You don't need to block gamma radiation completely to increase the electronics reliability :)
Maybe you could improve the system availability considerably by a bit of gamma radiation protection combined with some more parallelism of the components ..
The point is that shielding turns a single high energy particle that would otherwise strike and probably destroy a single transistor, into a veritable spray of lower energy particles causing bit flips or worse all over the circuit. This spray of particles can be stopped... with 1.3 feet of lead shielding.
A box with 1.3’ walls seems doable, actually, depending on how small the chips are. Might still be cheaper and more effective than specialized chips. But I know nothing, so am probably wrong.
If the only thing that effectively shields these processors from radiation is lead, concrete etc (per earlier comments), what design changes / quality improvements can compensate?
Hah, beat me to the nerd snipe. Moreover, that sphere would cost $10k to make and, at a launch price of $1500/kg, cost $4.5 million to launch into orbit.
The aim for the launch price of the entire rocket is to be around 5 million (once it's fully re-usable and in production). Basically the price of fuel and maintenance.
So something might be off with your assumption of 1500 usd / kg.
Yes, it's based in the real world. This was the Falcon 9 launch price that I could come up with in the amount of time I was willing to spend on a shitpost. I agree that launch prices will continue to come down, but launchers will always be mass-constrained and launching lead spheres into orbit will never be a practical solution.
IIRC the CPUs are much less susceptible to damage when powered-off ? So have a bunch of them in cold standby or even as additional pluggable modules on missions with humans on board & swap to good ones when needed? :)
No, that's correct. Of course there's still some level of reduction beyond which the gamma rays don't matter, but where you want to place it is somewhat arbitrary.
High energy gammas have a relatively low cross section, most are going to pass right through the chip. If you add a too little shielding, or don’t layer shielding appropriately you are going to stop more gammas but produce lower energy x-rays from the shielding, which have a higher cross section, potentially increasing your chip dose.
Would it be possible to create a "skip" EM shield that does the opposite - increasing the energy of the gamma rays thereby reducing the likelihood of stopping them?
No idea how. Energies of most chemical bonds / electrons around atoms are not very high, not sufficient to emit proper gamma rays AFAICT. High-energy gamma rays are produced in nuclear reactions. While "clean" nuclear reactions that emit only gamma rays and not neutrons do exist, they are very high-energy and thus hard to initiate, and I don't think it would be easy to capture the energy of incoming gamma efficiently enough.
But would using redundant systems separated in space connected with each other not offset the chance that they all would be affected at the same time? This is actually not rocket science .. just hard engineering and hardware/software design for redundant systems which is also usable on the ground.
"Hollman also found that creativity got him a long way. He discovered, for example, that changing the seals on some readily available car wash valves
made them good enough to be used with rocket fuel."
I have seen some people who decide to keep moving forward with whatever they have at the time. Sure what they produce is way less than perfect, but what they produce is way ahead of what everybody else is doing.
Perhaps the key is to be relentless, and resourceful.
Considering the political views of Elon Musk, it might be worth noting that his biographer is not the same Vance who is currently running for election as vice-president of the USA!
But it turns out, it doesn't matter how many redundant backup diesel generators you've got if a 45-foot wave comes along and they're all left underwater.
From an article for this I remember one more interesting side effects of this approach - the flight computer ends up as a generic x86/ARM board that the engineers can just have on their desk during development. Previously the dev boards would use the same rad hard chips and would be as expensive and scarse as flight hardware, resulting in much harder development & engineers having much less experience with the real hardware.
Just as a note, Space Engineers has a mod that accounts for fuel in the tanks and also various orbital mods. If one feels inclined to try it for themselves ;)
as someone who absolutely loves SE -- please don't.
the orbital and planetary mechanics kind of suck. They're meant to provide a decent 'arcade realism' for the sake of player/player interactions and pvp/pve.
if you want to experience fuel slosh/weight during a vertical ascent/descent go with kerbal. It models a lot of that stuff without mods -- and mods can make the model even more accurate.
I know MPC takes a LOT of compute power. It's not like a finely tuned PID loop or even a cascade of PID loops, computationally.
Does anyone know (or have educated speculation on) what kind of hardware is running these algorithms? Like, do they have a linux machine that's running the control loops? Are we talking megabytes, gigabytes of SRAM?
I would think no -- you would definitely need hard real time for something like this. But my only experience with real time systems is in tiny MCUs with kb of SRAM. That's definitely too small for a controller like this.
MPC doesn't need to take a ton of compute power. It all comes down to how sophisticated the underlying model is. You can have a MPC with 20 variables and run it at multiple kilohertz on a tiny microcontroller.
When you build something like this, you're torn between having a big model that represents everything and a smaller model that is easier to validate and reason about. Based on simulation, you might go for a smaller model that "knows" to stay away from operating areas where hidden variables (like really complicated tank slosh) invalidate the small model.
I doubt the actual control loop is too much processing, but it's certainly possible to build controllers with SDRAM, millions of variables of state, and hard realtime processing, though I wouldn't build it on top of preempt-rt. ;)
I have been told by people who worked on them that you get radiation hardened aerospace/defence grade chips by backing off the clock speed about 20% to give signal stabilization slightly longer time. I can understand the population being confused about this but industry being confused seems to have more to do with regulatory capture and beaurocratic moats which SpaceX does seem to be bypassing.
You also have to add massive amounts (relatively) of static sink by approaches like ‘silicon on insulator’ to prevent energetic electrons from hopping into the transistor layer.
People don't realize how powerful applied math (especially in the areas you've mentioned) has become. Same tools can be applied to people in the ad tech/social media.
>probably involve some kind of fast numerical fluid simulation
Sometimes even a simple approach can work. On Apollo they developed (at the time cutting-edge) passive RC filter networks, to avoid the control system "exciting" the rocket at frequencies of the slosh/bend/torsion modes.
> control system also has to compensate for the fuel moving inside their rockets
My stepfather worked as a programmer on the Apollo program, and the thing he always talked about as his biggest accomplishment was working on the "slosh problem" -- so yeah, props to the SpaceX team for managing that landing. And props to my stepdad for managing it on hardware that was... a billion times less capable? :-)
I might be misremembering but I think slosh was the failure cause for one of the three failed Falcon 1 flights. It was number 11 out of a pre-flight list of top 10 most likely failure scenarios. Definitely a difficult problem.
"instead of using $100,000+ radiation-hardened aerospace/defense grade chips"
Well, that makes perfect sense considering that both the spaceport infrastructure, and the booster need to do their calculation on the ground level instead of the highly radiated environment that is space. However, for the rockets themselves, which happen to reach that harsh environment, they may use more resilient and expensive hardware in the future, after passing over the current "let it splash in the Indian Ocean" development and testing phases.
> SpaceX control system also has to compensate for the fuel moving inside their rockets so the control algorithms probably involve some kind of fast numerical fluid simulation.
Surely this isn't necessary with a small enough sensor granularity or whatever the terminology is. You can have very dumb software if it reacts quickly enough to changes in perception.
(Not an engineer either) My understanding is that it's been done before on smaller scales but having a giant piston in the tank requires a good seal, railings to keep it straight, and overall way too much mass and rigidity. Consider that the tank walls are only a few millimeters thick.
Instead, it's more common to use gasses injected at the top of the tank to push the liquid to the bottom. Falcon 9 uses helium. Starship uses https://en.wikipedia.org/wiki/Autogenous_pressurization as well as small header tanks for the landing propellants.
When Musk first proposed this, I thought he was crazy. It seemed like something a school boy would draw up. Now I think this will become routine and forgettable after a few more successes. Is there a word for that - something out of fiction becoming mundane?
I thought it was plausible given the accuracy of F9 landings, though I still wonder how it will work at scale if one failure destroys the landing site. That could ruin the cost benefits.
Where his vision hit a lot of speed bumps is second stage reusability. Starship is a beautiful second stage to throw in the ocean. They’ll probably get it landing but the heat tiles will require a lot of refurbishment between flights. They’re going to have to figure something else out.
I really don’t think it will ruin the cost benefit as much as you suggest, especially when they have multiple sites and multiple locations. It wound be catastrophic, but they are presumably building Tower like the rest of their hardware, and every time they launch it represents a $100M saving compared to the competition.
It took months to more than a year to repair shuttle’s heatshield in some cases. SpaceX replaced the entirety of the heatshield with a new design and a new ablative underlayment in a matter of weeks. I suspect they will be able to do it even quicker with design and process improvements. Small scale repairs of the heatshield between flights probably wont be all that big of a deal.
The fact that Starship is unmanned probably helps expedite the change process quite a bit vs. the manned Space Shuttle. If you want to "just try something" the most you can lose is money, and not create a national political scandal.
I think the problem with shuttle was more fundamental. most of the tiles for Shuttle were custom cut to fit exactly one spot on one orbiter. I've read that NASA replaced about 75 tiles per mission, and that 2/3rds of the cost of refurbishing a shuttle after flight was the TPS. so the cost of trying something out was massive.
I'm expecting that SpaceX will have lots of towers, not just one (currently) or 3 or 4 (under way). It won't just be for redundancy. The duty cycle of a tower might simply not allow for the cadence that SpaceX wants to maintain. With Falcon 9 they currently have a 3x weekly launch cadence (which is unbelievable enough). With full reusability they might be able to get to daily and better cadence, so if the duty cycle of one tower does not support that (I assume right now it does not) then they'll need more towers.
A flight to Mars is currently going to require 10 tanker flights just to get enough fuel into orbit for 1 Starship trip. Containing liquid fuel for long in orbit will not be easy.
This likely means they are targeting 10 flights in a day at least. They've mentioned 1000 trips to Mars during one transit window, which means ~10000 Earth launches within 3 months, or >100 per day.
This happened with LLMs in a big way. Basically humanity surpassed some kind of AI milestone and we zoomed past the turing test in a big way. But thanks to social media everyone is sort of rolling their eyes at it.
2 related expressions:
1. Creeping Determinism - the idea that even magical leaps forward were somehow inevitable and were anticipated.
2. Nihil Admirari - the idea that wisdom is anticipating every possible thing that could happen, therefore a wise person would never be surprised.
But I lump both these together as the *"Wiseass Movable Feast"*
The booster was falling at 4500 Km/h 30 seconds before the catch with 2-3% fuel left. How is that amount of fuel remotely enough to stop the downward momentum?
The atmosphere does its bit to slow down the booster as well. It’d be interesting to see a plot of the power output over time on reentry but I’ve always assumed the motors aren’t doing a lot of work other than keeping the booster stable, until the very end.
Yes, for most of the booster return it’s ‘gliding’ with the rocket engines completely shut down.
They ignite a subset of engines just a few seconds before landing for the final slowdown and maneuvering.
Edit: here is a video from further away that shows the rocket gliding in under control of the grid fins before the engines light and execute the final landing maneuver:
Super heavy probably makes certain aspects (unrelated to the tower catching the booster) of landing much easier, by virtue of its greater mass. Timing with the Falcon 9 was always essential, because the minimum thrust (with one motor, throttled all the way back) of one of the engines was enough that if you left the motor running, the booster would start to rise. Time the beginning of the final burn incorrectly and you had a real problem, with the booster either crashing or rising at the end and... then crashing, but with Super Heavy, it might simply be a matter of having to compute a slightly different sequence for shutting off the engines.
Super Heavy is easier to control on landing because it's using 3 engines so has better directional control, and it can throttle those engines down into a sustained hover, which is what it does before being "caught" by the arms.
Surprising to see this work first time though - I don't recall them doing any hover and lateral movement tests, but I assume they must have done.
What's also wild is that the booster isn't being caught/supported by those giant grid fins, but rather by small lifting pins just below them, and seems to only have two of these (one on either side), so it also has to get it's rotational position right so those pins engage with (are supported by) the arms.
> Yes, for most of the booster return it’s ‘gliding’ with the rocket engines completely shut down.
Watching the video, it looked like the bottom of the rocket was glowing hot, but the engines were cool. I imagine that means they were probably running some amount of methane through the engine bells to cool them.
Yeah, but even without fuel the booster weighs 200 tons. It's pretty wild to have 200 tons of steel incoming at supersonic speed, then nailing a gentle pinpoint landing like that !
Yeah if the engines didn’t light and it hit the launch facility that whole place would be a crater. The whole thing was shocking to me but how fast it was coming down was extra shocking haha. I wonder what deceleration forces were at play because when the engines lit the booster slowed down very fast.
It weighs about 10% of what it did at liftoff, but half of the engines fire to slow it down.
Also I don't think the telemetry on the feed is that accurate, so with all of the atmospheric braking, it was probably going a bit slower than the 1200km/h at engine reignition.
First off, the booster was going about 1250 km/h when it started its landing burn, it relied purely on drag to get it slowed down to that speed.
Going by the telemetry of the seconds before the landing burn and noting the speed vs time, it seems drag was around 40 m/s^2 when it was going at around 3000 km/h. Since drag depends on velocity squared though, it had reduced to just above 10 m/s^2 just before the engines lit at 1250 km/h, and so would quickly become negligible once the engines lit.
Going by Wikipedia, the Super Heavy[1] has 3400000 kg of fuel at launch, so 3% of that is about 102000 kg. For the landing burn, it used 13 Raptor v3 engines[2] to scrub speed. Each Raptor flows about 650 kg/s max, so 3% fuel is enough for about 12 seconds for the 13 engines.
The empty mass of the Super Heavy is about 275000 kg, so about 377000 kg before the landing burn with 3% fuel.
Using the sea-level vs vacuum performance of the Raptor v2 engines, one can estimate that each Raptor v3 produces about 2.45 NM of force at sea-level. So 13 of them would produce about 31.85 MN of force.
Using Newton's second law, F=ma, this gives an initial deceleration of about 84 m/s^2 and about 104 m/s^2 when empty. If we do a rough spreadsheet integration, we get that a burn of roughly 4 seconds is needed to scrub the speed assuming no other forces.
Now, comparing this with reality, the full 13 engines were lit for a little over 5 seconds.
In my simplified calculations I was assuming full throttle the whole way, which obviously isn't realistic, and I also assumed 3% fuel. So over all I think that's a pretty decent estimation.
Methane has 28% more energy per kg than kerosene and also produces slightly less CO2 (2.75kg CO2/kg burned vs 3.00 for kerosene) when burned [1]. SpaceX uses a 78:22 LOX to CH4 ratio, so for 34M kg of fuel burned, 20.57M kg of CO2 are produced (34×0.22×2.75).
Somewhat tangential, but as far as rocket fuels go energy per volume is also an important metric to consider. It's one of the (several) reasons hydrogen isn't quite as good for rockets in practice as it is in theory - while hydrogen has tons of energy per unit mass (120-142 MJ/kg for hydrogen vs. 50-55 MJ/kg for methane and 43.1-46.2 MJ/kg), it has a far lower density (70.85 kg/m3 vs. 422.8 kg/m3 for liquid methane and 820 kg/m3 for kerosene). As a result, you need quite a bit more tankage for a given amount of energy from hydrogen compared to what methane/kerosene requires.
IIRC there's a tradeoff between efficiency and thrust as well. Heavier fuels aren't quite as energy-efficient, but it's easier for them to develop a lot of thrust, which is important for the initial stages of launch. If I'm remembering events described in Ignition! correctly this led to "thrust density" being something that was optimized for - to the point that there were experiments with mixing mercury into the fuel!
Just a programmer, though been interested in physics since I was a teen and did take a bachelor degree in simulation (mainly physics).
Long ago though so rusty, $dayjob doesn't involve any advanced math at all.
edit: To expand, the "rough spreadsheet integration" was just the Euler method[1] assuming a constant acceleration. So
v(t+dt) = v(t) + a * dt
The acceleration comes from F=ma as mentioned, where F is the force of the engines (Newtons), m is the mass of the rocket (kg) and a is the acceleration (m/s^2). Solving for a we get a = F/m and we get
v(t+dt) = v(t) + F/m(t) * dt
To make things easy I assumed the weight of the rocket was constant at each timestep, but if we take dt to be small enough it's a decent enough approximation. For each timestep I also updated the mass using the estimated mass flow:
m(t+dt) = m(t) - 650 * dt
I started with m(0) = 377000 kg, v(0) = 1250 km/h = 347 m/s, and a constant -31850000 N force from the engines.
Using dt = 0.1 seconds, I got almost exactly 4 seconds until the velocity reached zero.
Newton's laws of mechanics are high-school physics IIRC; my son studied them at 8th grade or so. They are really simple; an evening with Wikipedia or 3blue1brown or whatever floats your boat will let you get sufficient understanding, provided you're also comfortable with high-school math.
That's excellent work, only nit is I think these were not the v3 raptors. I think they're just now starting production of those, so they still have a bunch of earlier ones they need to use up in these early test flights. This actually makes your calculation more accurate, as earlier versions will need a slightly longer burn time.
Ah, good catch, I must have misread the Wikipedia page. I misread that they were included in the rocket in August. Reading the Raptor page more closely I also see that the 2.75 MN of the Raptor V3 are supposed to be at sea-level.
Anyway, plugging in the Raptor V2 thrust numbers the approximation increases to 4.25 seconds. This is in line with the thrust I used for the V3 being ~8% higher than the V2 thrust figures.
Note that the energy of 3% of the propellant (~100 GJ) could theoretically get the empty booster (100,000 kg) to a little over 5000 km/h if properly applied.
I thought the same, screamed out "ouch that doesn't look good!" right before the catch.
The last part of the live stream they showed footage from a different angle and there it didn't look too bad though! For sure controlled.
Scott Manley put out a tweet that they went down towards a non-tower position until they were at three engine controlled burn, and only then did the side shift.
If I had to bet, I would bet against it. Boston Dynamics for example, for the longest time, didn't use anything other than Model-Predictive Control. Only recently have they started using RL
I know the control algorithms are the mind-blowing part here but,
does anyone have any literature about how the Rocket localized itself with respect to the chopstick arms? It must've been some combination of GPS and Radar pings to the arms?
And then the onboard IMU to make sure it hits it straight.
From the control point of view, isn't this exactly the same as F9 landing on a pad, except the pad is virtual, floating in between the chopsticks and the ground? Or course one difference is that the approach needs to be from the correct direction.
I seems to remember some article mentioning the Falcon 9 using radar (+ presumably other sensors) & even having a landing site map uploaded (mainly for the return to launch site scenarios) with prioritized exclusion zones in case of a landing failure.
A major difference is that F9 (landing on a wide flat pad) had a quite wide acceptable horizontal error, 10 meters or more, whereas I think this (landing between two chopsticks) needs like ~1 meter accuracy in the radial direction.
Great question! Could just be Real-Time Kinematic (RTK) GPS like someone mentioned. Essentially the landing arms know their position very precisely and they measure the tiny errors in GPS data, and send that correction data live to the rocket in real-time as it's landing. Once the rocket gets very very close it could also just be using vision systems to zero-in on exactly where the chopsticks are.
To speculate more, they could also be using something like ultra-wide band positioning. This relies on the same time-of-flight principle as GPS but instead of using satellites in orbit to provide the precise time information you rely on various nearby ground stations. Would only be useful right at the final approach, the last couple hundred meters, but it's another way they could get very very precise position information. (fun fact: Ultra Wide band positioning is also how iPhones can locate AirTags with centimeter accuracy)
Why bother with GPS or other "absolute" coordinate systems? Once the rocket's in close, all that matters is relative position and orientation of the rocket with respect to the landing apparatus. Eg, if you had many sensors in known locations on the rocket and many sensors in known locations on the landing apparatus, and you could measure relative positions between all pairs of these sensors, you could get extremely precise relative position/orientation information without beaming information to satellites or whatever.
That's amazing footage, and you're right about the perspective: from the official feed the distances seem compressed compared to what we see in this footage.
Yes, indeed. But I will add that the sheer size of the rocket helps in this regard. I think it is rather hard to appreciate the massive scale of the feat by watching videos.
A clip from some news program popped up on YouTube, just a two minutes clip of the catch, I was convinced that it was reversed. The fact that this is possible, that they made it work is nothing short of amazing.
Uuuh the first stream on YouTube was Musk giving a speech, so I was waiting for the launch but turns out it was on another stream? So I just missed the whole thing, great.
Youtube is an incompetent organization. I've seen it take them nearly 48 hours to restore channels stolen by scammers to their rightful owners (all the while allowing the crypto scammers to continue streaming.)
There used to be a Twitter AppleTV app and I recently saw an X app for TV platforms has been brought back, but I don’t know if the AppleTV version is out yet.
Of course I’d rather they just stream to YouTube in 4K.
Removing their YouTube account was part of the strangeness. Even if you own a social media company you really need the YouTube account to squat your brand and redirect
Could you please stop posting unsubstantive comments and flamebait? You've unfortunately been doing it repeatedly. It's not what this site is for, and destroys what it is for.
Personal attacks in particular will get you banned here, so please don't post like this.
Improvements that make space flight more sustainable are welcome ... unless that means an order of magnitude more pollution in a less controllable form, like emissions. [Due to more frequent flights]
Daily trips to space likely also mean more debris in space and falling to earth.
I hope there is a balance that includes the lives of people near these sites and all of us sharing the same atmosphere.
SpaceX proposed it but I doubt there is any chance of this architecture ever achieving the airliner-level reliability needed for people to accept routine Earth-to-Earth passenger service. That's several levels beyond what you'd need to fly astronauts.
Maybe a future architecture with more redundancy could get there someday.
> Considering the safety and prosperity that can be brought online from 1,000 launches / 150,000 tons in orbit, that’s the deal of the century.
Regardless of the (in)accuracy of ChatGPT, you're assuming a lot can be accomplished with those flights. I strongly suspect 600K cars getting people where they need to go has far more utility than 1K flights of anything into / out of NEO.
> Debris is an absolutely non-issue.
Astronomers probably don't want 1000x (or even 10x) as many satelites obstructing their view.
> There is zero environmental downside, only Luddite foot stomping.
Name calling isn't going to help your cause. And the luddites had a good point, they didn't mind innovation. They minded being cut out of the benefits of innovation without any say in the matter.
Please avoid tit-for-tat spats on HN—they're nasty and boring. And please don't post in the flamewar style to HN—it's not what this site is for, and destroys what it is for.
Please avoid tit-for-tat spats on HN—they're nasty and boring. And please don't post in the flamewar style to HN—it's not what this site is for, and destroys what it is for.
1,467 comments
[ 2.8 ms ] story [ 383 ms ] threadIn The Expanse (which I highly recommend), they give a new lease on life to that quote attributed to Einstein "I know not with what weapons World War III will be fought with, but World War IV will be fought with sticks and stones" - hurling asteroids towards a planet. I really hope humanity's real future will play out in accordance with some of the more optimistic elements in The Expanse.
It's always funny seeing people pretend they live in a world where small issues like land or food don't affect them, even though they only have that privilege because a larger military says they should.
It's hanging pretty high in the air, I assume so the engines do less damage to the pad. One wonders how they're going to get it down. Do the chopsticks lower on the tower?
My hunch is that they don't put it down for awhile. If there's still an issue were there are fires lingering inside, my hunch is they want that as far from the ground infrastructure as possible.
Either way incredible progress.
Wasn't perfect, some things to work out... but still pretty damn good.
What an amazing morning!
Earth to moon without Aerobraking is a delta v of around 13k/s, mars is 13.3
Thats like a 747 to space.
No idea about the other costs.
Also, while 150t is the target payload capacity, the current test vehicles are closer to 50t in payload capacity, there are revisions in the pipeline based on data from these test flights which will bring it up to 150t.
The dumping of this excess propellant actually caused an explosion and loss of vehicle on the second test flight.
Whatever that means is what it means, the ship was out of control and I don't know whether or not the mission requiring that payload was successful, but the fact is that it did carry the payload.
A modern airliner on a long flight might burn around 80 tons of kerosene. It's slightly cheaper than methane. Call it 75-80K$.
Am I mistaken, or are there distance/payload combinations for which Starship is cheaper per pound on a point-to-point basis than air transport, even setting aside 30 minutes versus 12 hours? Isn't that the non-intuitive outcome of ballistic trajectories?
https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
It's quite possible that SpaceX has access to some cheaper methane source. Texas produces a lot of it.
And SpaceX has speculated about eventually switching to some renewable source by e.g. synthesizing methane. In which case that would boil down to cost of electricity and carbon. I don't see that becoming cheaper short term but that could happen long term.
They did [1].
[1] https://en.m.wikipedia.org/wiki/Space_Shuttle_retirement
Material: stainless steel is much cheaper
Percentage of reusability: boosters of shuttle cannot be reused, maintenance of shuttle itself is also very expensive (heat shields were pricey). whereas the starship stack has higher reuse percentage and allegedly cheaper to maintain.
The other big difference, an elephant in the room grade difference I think, is that SpaceX reliability was developed with memories of a reusable vehicle failing mostly due to turnaround costs and risks on everyone's minds. That clearly wasn't the case when the space shuttle was designed, they were the first and enjoyed the privilege of making all the beginner mistakes.
He emailed back that he agreed with my reasons and had argued that case with NASA in the early stages of the shuttle program.
So NASA was aware of this at the time.
Yes, both systems are reusable, but there are key differences in the refurbishment of the systems that partly explains the cost difference. It took more labor, resources and time to refurbish the shuttle. Also consider rapid reusability was a stretch goal when it was being designed, but we have come a loooong way since, spacex in particular has had it as a driving competitive differentiator for years now.
Another big difference is that NASA post Cold War was a skilled jobs program, with an incentive to do distributed, high overhead work to appease their bosses (congress), while SpaceX has the opposite.
Starship uses essentially the same ceramic heat shield tiles as the Space Shuttle, so the fact the Shuttle had so much trouble with refurbishment doesn't mean that SpaceX has solved these refurbishment issues with the Starship upper stage.
Though the Starship lower stage, which contains the most expensive engines, doesn't have this problem. Since it doesn't need a heat shield. So partial reusability should be pretty realistic.
> In terms of shapes, the tiles were not uniform. In fact, there were over 17,000 different shapes used to fit specific areas of the shuttle's body. Each tile had to be individually manufactured and shaped to fit a precise location due to the complex curvature of the shuttle's surface. The unique shapes were necessary to ensure that every part of the shuttle received the proper protection against the extreme temperatures during re-entry.
https://www.google.com/search?client=firefox-b&sca_esv=11e08...
This gives a direct answer (24,300) while citing a NASA source.
Note that the question here is how many uniquely shaped tiles there was, not the total number.
This is interesting because if you have to manufacture and keep in stock 17,000 separate tile shapes, that will be vastly more expensive than SpaceX who, from what I hear, only uses a singe hex shaped tile everywhere.
But on a more technical level. I think the vertical landing is the main difference. Vertical landing was obviously known and done by NASA, this is how the lunar modules landed on the Moon. But doing it on Earth, with vehicles weighing hundreds of times more, I don't think the world had that technical readiness a few decades ago, when the space shuttle was designed.
And another major difference is the mass manufacturing idea. From the start SpaceX planned for getting to mass manufacture its rockets. The Falcon rockets are much cheaper than any other alternatives even if you remove the reusability.
Then it's the methane burning engines. This was pure old fashioned engineering progress. SpaceX's engines are miracles of rocket engineering. Aside from that, the fuel choice is extremely smart. Methane is better than all other fuels, except for hydrogen. Hydrogen was the fuel of the space shuttle, but it's very tricky to work with. It has very low volumetric density, so the tank of the space shuttle was absolutely humongous. Hydrogen needs to be stored at an absurdly low cryogenic temperature, so this adds to the complexity. And that tank was not reusable, so it adds to the cost.
It is also yet to be seen how Starship will ever be profitable (outside of spending government money), who is going to pay for those launches and for what purpose. Other than Starlink, of course.
Now personally I’m looking forward to NASA, ESA and JAXA to launch outer solar system probes like new horizons but with tons of fuel left in the tank to safely make orbit around there.
Partially. They have a fixed-price contract to land humans on the Moon, and notably got that contract because they severely undercut the other bids and were the only bid that actually fit within the available budget: they bid $2.94B, while Blue Origin bid $5.99B and Dynetics $9.08B.
That 3 billion is also much less than what they're spending on the project.
So was the space shuttle, so that's not a difference between the launch costs of the two vehicles.
It also allows for launching individual space station modules that have almost the same volume as the entire ISS in one launch.
Their plans for refuelling on orbit with tanker versions of the starship open up the entire solar system to unmanned missions with much shorter timelines and much higher payload size and weight.
The fact the entire system is re-usable will make it both cheaper and faster to use than any other launch system.
All of this combined mean that it won't just be countries and space programs bidding for space on launches, it puts space within reach of many corporations and some private individuals. This isn't conjecture, it's already happening with the Falcon 9. Starship will make it even more accessible.
Of course, that means you could also fit a James Webb-folded telescope except make it a lot bigger :-)
My favorite related thing is that the Starship itself could serve as a large space or moon station.
About 10% funded by NASA. Starship is a >$10B program; SpaceX is getting $3B for Artemis of which >2/3 is for operational tasks and moon-specific stuff that SpaceX aren't relevant for SpaceX's goals of LEO and Mars.
Now taxpayers have a 10x return on investment.
But it's high cost was the end of it.
The high cost should have killed the project before it ever flew, but that's not how governments behave.
All of that adds tremendous weight, complexity, and cost.
There are better fuels in terms of Isp and density. They have some downsides such as being corrosive or having highly toxic exhaust.
https://x.com/ToughSf/status/1453391050681327622
And unbreathable and full of sulphuric acid. You may as well just stay in orbit.
On Venus, a puncture doesn't immediately destroy anything - because of equal pressure on each sides of the balloon wall. You have more than enough time to put on a protective coat and fix it.
And building more living space is much easier + you could source the material (carbon) on site.
a. Cheaper, more durable material (stainless steel).
b. Cheaper, easier to manufacture engines.
c. Easier to use fuel (methane is much "tamer" than hydrogen).
d. Standardized heat shield with much smaller requirements for manual work.
We'll have to see how it works out.
Contrast that to the Space Shuttle which required a human crew to flight test anything.
Same thing for SLS.
The need to codify what work is to be done in contacts is antithetical to SpaceX's rapid development processes.
https://en.wikipedia.org/wiki/Theory_of_the_firm
SpaceX builds vehicles. The Shuttle was “reusable” because they needed a term between the default for transportation capital expenditures (e.g. trains, planes, cars and ships) and the modified missiles that defined post-War spaceflight. “Reusable” in the Shuttle’s context meant months of specialist overhaul time and the cost of a Falcon 9 launch in SRB booster replacements alone [0].
At the end of the day, in 2010, “the incremental cost per flight of the Space Shuttle was $409 million, or $14,186 per kilogram” [1]. ($591mm and $20,512 in 2024 dollars, respectively [2].) SpaceX’s prices per kg are around $3,170 on Falcon 9 [3] and $1,520 for Falcon Heavy [4]. Starship should bring those costs below $1000.
[0] https://forum.nasaspaceflight.com/index.php?topic=51959.0
[1] https://en.m.wikipedia.org/wiki/Space_Shuttle_program
[2] https://www.usinflationcalculator.com/
[3] https://www.spacex.com/media/Capabilities&Services.pdf LEO
[4] https://en.m.wikipedia.org/wiki/Falcon_Heavy LEO, theoretical
It might even bring the costs below $100/kg.
(My guess is the economics are fine, but the politics would kill it on earth, so the moon or mars will get one, but that's just an interested amateur opinion).
(I may be misremembering or getting confused with a thing specific to tidal locking?)
I suppose the same effect is there with satellites much smaller than the moon, but it would be tiny.
https://commons.wikimedia.org/wiki/File:Orbital_Debris_Lifet...
But yes, eventually things decay.
https://www.esa.int/Enabling_Support/Space_Engineering_Techn...
StarShip consists of the Super Heavy booster that we saw "caught" today, and the StarShip (orbiter) itself. Having the booster return to launch site vs requiring ocean recovery should potentially increase cadence and reduce cost of reuse. StarShip is also meant to be reusable, although it remains to be seen how that will pan out. On the previous flight there was burn through from inadequate heat shielding - maybe we'll see an improvement with today's vehicle. I'd expect SpaceX to iteratively arrive at a quicker and more cost effective orbiter reuse procedure than NASA had with the shuttle, but how quick remains to be seen. Of course they are planning many of these to go on one-way trips to Mars rather than being reused.
Worth noting that Starship's heat shield is very similar to the one of the Shuttle. They actually got the manufacturing method from NASA.
The difference is that they have already proven to be the lowest cost and most reliable launcher due to reuse. This is them lapping the industry with second stage reusability.
Starship is supposed to be (and clearly well on the way to being) fully rapidly re-usable. That means all stages (in this case two) are re-usable, and that the capital and time required to get either stage flight ready again after a flight should be minimal.
Said another way – it is cheaper for SpaceX to build an entirely new Starship + Booster than it was to refurbish a Shuttle between flights, by a factor of about 4x ($90M for a Starship+Booster / $400m for Shuttle refurb).
Let's start with the fact that it was designed in the 1970's. If you had a Cadillac DeVille from 1970 it would get 8-12 miles per gallon. Just the mere fact that the design is about 70 years old makes that vehicle too expensive to operate, and that's before we even start talking about other issues with the design (performance, safety, reliability, etc).
One of the design goals of Starship is for the booster and ship to relaunch with zero refurbishment. To literally land over the launchpad, refuel, and go back to orbit within hours without people even approaching them. The heat shield is the biggest risk to that goal IMO, and we saw today that it definitely sustained serious damage despite improvements. But if they ever get there then per-launch costs will be a tiny fraction of the Shuttle with 6x the payload.
This is in contrast to something like the falcon, which has a very standardized mfg process and components, which allows for really rapid iteration
The shuttle would have been much, much, cheaper per launch if it had flown more often. The expected costs for the shuttle included a range based on how often it flew which turned out to be reasonably accurate. They were much worse at predicting which end of the range they would be flying in. At the rate they ended up flying they had the extra costs of reusability without any of the benefits.
Starship is ludicrously expensive, but still much cheaper than even the best case for the Shuttle, and it has a guaranteed source of launches to help it benefit from resuability.
It actually would have been a lot cheaper if they had gone for serialized, mass assembly line production of Saturn V class disposable rockets to launch piece of space stations, satellites and manned missions into low earth orbit.
More than 40 years and many lessons learned.
SpaceX took advantage of tech from both the US and Russia, including the experience with the Space Shuttle. They have better computers, better metallurgy, advanced 3D printing and their own experience with the Falcon 9.
There is no guarantee that it will reduce the costs that much, but will all that experience, the chances are success are higher than with the Space Shuttle.
One big issue that isn't talked about much and that SpaceX takes very seriously is simply a lack of demand. There is only so much stuff you want to put in space. Satellites are expensive, and even with disposable rockets, the launch is only a smaller fraction of the cost. It is already a problem with the Falcon 9 as they have a bunch of rockets and not much to do with them. Starlink, orbital refueling, and crazy ideas like earth to earth transport are all ways to address this problem.
It was a problem for the Space Shuttle too, they couldn't achieve the economies of scale they planned it for. It was supposed to fly for routine maintenance missions but it didn't work out.
What this also means is that if you want to get into the space economy, work on things to do in space, not yet another launch vehicle startup.
https://en.m.wikipedia.org/wiki/ʻOumuamua
Is their timeline too optimistic? Yeah, but if the industry still catches up with F9 and they are close to having something a lot more advanced it really doesn't matter.
Even without reusability nothing comes close to Starship's cargo capacity. If you don't have to put a lot of engineering into getting things as small and light as possible you can put things in space a lot faster.
Even just one engine in minimum thrust would make the rocket go up when empty.. so the computer lights the engine at the precise right moment so it will have 0 velocity at 0 altitude, then it cuts off the engine. "Hoverslam".
The Starship booster is different, it can actually hover.
Point is it always seems like you’re coming in too fast
> Mechazilla has caught the Super Heavy booster!
https://x.com/spacex/status/1845442658397049011
Obviously the primary mission was successful, in spite of anomalies (good system design!), but people are and should be curious about this aspect.
100% with you. The teams I’ve worked with would be celebrating and trying to figure out what’s burning at the same time. And especially trying to figure out if there’s anything that they need to do to collect evidence for that investigation (eg zooming the remote PTZ cameras in on specific areas or things like that)
https://news.ycombinator.com/newsguidelines.html
I bet SpaceX does. They've solved the big problems, now it's time to solve the small problems and make reuse a reality.
The vent out the side before touchdown didn’t look right, though. Something blew, but non-critically.
For example, prototype number 10 exploded 8 minutes after landing [1] because of a seemingly insignificant fire at the bottom.
After today's flight there was a long lasting fire in the engine section, with occasional flaming pieces of plumbing raining down from the rocket. Examining the aftermath should help SpaceX to understand what improvements need to be made to prevent this from happening.
[1] https://youtu.be/XOQkk3ojNfM?t=38346
It's an object lesson in rapid engineering development. If everything goes perfectly in a development test, it's a sign you're not moving fast enough (meaning not taking enough risk per increment to maximize learning). As valuable as Falcon, Starlink and Starship are, the biggest near-term value of SpaceX may be providing such a clear demonstration of well-executed "fail fast, learn fast" engineering that even politicians and bureaucrats can understand it.
Historic viewing :)
https://www.youtube.com/watch?v=YC87WmFN_As&t=3h25m14s
> Holy flying fuck, look at that thing!
Gold.
[1] https://x.com/Cosmo_556/status/1845554958604657051
Note that the booster is not really being "caught" although this is the word it seems we're stuck with. It's really more like landing on the arms, since it throttles to a hover at that point.
Not necessarily for reusability, but it helps significantly for rapid reusability: it eliminates the need to transport the booster from the landing site to the launch site. Given that it's 9m x 70m and weighs 270 tonnes, that's not an easy process.
That was the exact reason they went this way.
Maybe they will have to sacrifice more payload mass for active or passive shielding or more fuel for powered deceleration. That would yield a less impressive lifter but with full reusability.
It was one of the technological breakthroughs of von Braun's team with the V2.
You're way too optimistic. Starship will deliver commercial payloads, with SpaceX phasing out Falcon 9 outside of ISS launches, before anyone has a reusable Falcon 9 equivalent.
It pains me to say this, but SpaceX is in a class all its own.
Blue Origin plans to launch New Glenn in a month, with landing planned. They are a wild card.
SpaceX is one of the greatest, if not the greatest, private technology company in history.
Musk is getting something from Trump: most likely protection from some legal issue.
You mean that time that the FCC removed Starlink from the broadband problem when they couldn't deliver the speeds that they had committed to, as defined very explicitly in the program?
Trump may well win this election. But there’s no scenario under which he’s going to also win the popular vote while doing it, at least none that I’ve heard of. If you have credible information that says otherwise I would be interested in reading it.
Even when millions are suckers for it and think others will be the ones to suffer.
This manufactured, polarized "us vs them" thing on the internet is toxic corrosive goop. People are complex and that is fine.
- He called some guy who worked for him a pedo for no reason, which he was sued over
- Took over Twitter and promoted right wing tweets to everybody, unbanned far right accounts and sued critics who said he did so
- Started promoting far right ideas, like when he retweeted "Interesting" to some tweet of a 4chan post saying that high-status, high-testosterone males are the only ones who can think freely and should be the only ones who can vote
- Took the side of the right-wing rioters who attacked mosques in the UK, saying civil war is inevitable
- Just seems to insult companies for little reason - advertisers who leave him, and Apple
There has been kind of a slow back and forth. Some people who liked him were miffed about the pedo thing, but they didn't hate him. But he has just kept doing things that some people hate.
Leave out the part where the riots were started because someone with an immigrant background killed a bunch of kids at a Taylor Swift concert and police were withholding the identity. Along with your other 'anecdotes', can you make your political position any more transparent?
> because someone with an immigrant background killed a bunch of kids at a Taylor Swift concert and police were withholding the identity.
It might be somewhat justified if they burnt the house down of the murderer, or those who assisted him. They didn't - they burnt down houses, shops, and mosques, because they wrongly assumed the guy was Muslim and decided that was just cause to target any Muslim. His identity was hidden because he was a minor at the time of the attack.
and coincidentally he makes cars and rockets too!
Supposedly they’re working on both a reusable and cost optimised non-reusable second stage at the same time. And they don’t really know yet which one will end up being cheaper.
You also see this kind of thinking with Rocket Labs neutron rocket. Where they focus on making the reusable booster do more, while making the second stage smaller, cheaper and simpler.
I think if it wasn’t for the rocket engine this wouldn’t be a question at all. The tank doesn’t have much value. It’s just a thin shell and probably a fraction of the cost of the fuel.
So I’m thinking, perhaps the optimal solution is something like this: the bottom part of the second stage with the engines separates, and a small engine and fuel tanks places the engines in a stable orbit. The tank itself is deorbited and burns up.
At some point later something like the Starship collects several second stage engines and deorbits them safely to be reused.
Or perhaps just the engines can be immediately deorbited with an inflatable heat shield and parachutes.
Sure, SpaceX has been doing first stage reuse for a long time now. But they have demonstrated landing the second stage successfully at sea twice now with the same sort of smoothness that they demonstrated once for the booster before they then caught the booster on the first real try.
A partial list of unbelievably hard things that SpaceX has so far made seem easy:
Catching the booster is really just like landing a Falcon 9 booster w/o legs, but clearly much harder.Anyways, if they can do all those things then it's pretty clear that they can catch-land the ship.
There's still a huge list of crazy-difficult things that SpaceX say they want to do that are hard to believe are possible, except for the fact that SpaceX has already done so many unbelievably difficult things already.
They could do the same thing with S2 recovery here.
But I imagine that by IFT6 they'll have nailed the flap burn through problem.
IMO a better use for it might be to ferry up large pieces of purpose built craft with less excess dry weight. A single reusable Starship launch can put the entire mass of the Apollo craft needed to make it from LEO to the Moon and back into LEO. Put a craft in two launches and dock it in orbit and you've got a huge capability to put a lot of mass onto the moon and still use the cheap cost to orbit Super Heavy gives.
The tiles in combination with ablative materials and the insane robustness of a steel vehicle is sufficient to get Starship through re-entry and soft land in the ocean. We know ceramic thermal tiles worked on Shuttle and X37B and presumably will on Dreamchaser so while the success was an awesome achievement it wasn't unlikely given time to refine their methods.
SpaceX are limited by the properties of real materials, not their ambitions, and we still don't know if rapidly reusability is possible with ceramic tiles or if their fragility will require inspections and refurbishment. They can't do it with ablatives and there aren't many other options. I am optimistic but also realistic about the difficulties of what they are attempting. Sometimes risky projects run into brick walls and you don't know what is possible until you try.
Truly incredible. A day for the history books.
Had flashbacks to playing Jupiter Landing on the C64!
https://en.m.wikipedia.org/wiki/Jupiter_Lander
Edit: SpaceX should create a simple 'catch' the rocket game. Play in browser style. Just for kicks and marketing.
there is, it was discussed in the FAA thread.
https://news.ycombinator.com/item?id=41821220
lunar.unnecessarymodification.com
They did: https://starshipthegame.spacex.com/
Another interesting thing SpaceX is doing is to use consumer-grade chips in triple redundancy configurations instead of using $100,000+ radiation-hardened aerospace/defense grade chips.
If it's no stronger than a sudden wind gust, it's just something the controller has to be able to take care of without a heads-up.
Then the next launch crashed due to slosh induced oscillation - and the one rocket after that had anti-slosh baffles. ;-)
More fluid dynamics
By their very nature model predictive controllers operate in a world where not everything is perfectly modelled. Engineers do their best and whatever is left is the "error" the controller is trying to deal with.
Sort of like how you can balance a few pitchers of beer on a tray in your hand by remaining aware of the weight, even when people remove one! hahaha :)
Which is why we use wind tunnels, for example.
These are indeed heavy computations. What I meant is that VoF is one additional equation to be solved besides the N-S equations (either filtered as in LES or Reynolds-averaged as in RANS), the energy equation, your turbulence model equations, and so on. Certainly, not instantaneous at all, but simply an additional "simple" model that we can hook into our current way of doing CFD.
So, my point was, sloshing is a problem that we know how to simulate, although certainly you need HPC resources. Though, looking at those 100k NVIDIA H100 Elon has, I guess they have them! :P
I think it's a huge problem when re-lighting the engines in orbit, though.
See also: https://en.wikipedia.org/wiki/Ullage_motor
Bug tanks make sense there & they might not be always full. So I can imagine all kind of interesting ways you can work with the fuel in zero go to avoid not only slosh but also the need for ullage thrusters. Eq. some programmable nozzles using in-tank gas to nudge liquid fuel blobs to move in the right direction. Or even some nets or bags that herd in the fuel in the middle of the tank + prevent it from directly touching the side, reducing boil-off or refrigeration requirements. :)
Even a real-time simulation should have some measurements to self correct to some degree. Otherwise it'll diverge.
http://cse.lab.imtlucca.it/~bemporad/publications/papers/ecc...
They used trios of regular consumer grade disks/servers etc as a cluster and it looked like a single node.
They had to replace a LOT of hardware but this was still cheaper than big iron industrial grades servers.
This has been known in the high availability and safety systems industry for a while and a good book to learn these reliability engineering techniques is "Reliability Evaluation of Engineering Systems".
The book is available on amazon: https://a.co/d/1nH824K
https://www.epa.gov/radiation/radiation-basics#:~:text=Gamma....
Maybe you could improve the system availability considerably by a bit of gamma radiation protection combined with some more parallelism of the components ..
A second layer blockage for the secondary particles wouldn't have to be as dense or am I missing important physics?
(I guess a lot of gamma radiation would still reach this second layer so please ignore my question :)
https://www.wolframalpha.com/input?i=+lead+cube+with+side+le...
So something might be off with your assumption of 1500 usd / kg.
I can't decide if I'm joking or not.
(Though likely not of course ;)
But would using redundant systems separated in space connected with each other not offset the chance that they all would be affected at the same time? This is actually not rocket science .. just hard engineering and hardware/software design for redundant systems which is also usable on the ground.
"Hollman also found that creativity got him a long way. He discovered, for example, that changing the seals on some readily available car wash valves made them good enough to be used with rocket fuel."
"Elon Musk" by Vance pg 123
I doubt any Lowes parts made it to space, but you know some went into test articles
Perhaps the key is to be relentless, and resourceful.
The Fukushima and Deepwater Horizon disasters show that this knowledge has not penetrated other industries.
But it turns out, it doesn't matter how many redundant backup diesel generators you've got if a 45-foot wave comes along and they're all left underwater.
the orbital and planetary mechanics kind of suck. They're meant to provide a decent 'arcade realism' for the sake of player/player interactions and pvp/pve.
if you want to experience fuel slosh/weight during a vertical ascent/descent go with kerbal. It models a lot of that stuff without mods -- and mods can make the model even more accurate.
Algorithms can be faulty as well.
Which was never claimed.
That paper is a little bit about Erlang and a whole lot about OTP and other methodology and design technique.
It is still, very much "the paper" for distributed systems, though its applicability to this particular problem is limited.
Does anyone know (or have educated speculation on) what kind of hardware is running these algorithms? Like, do they have a linux machine that's running the control loops? Are we talking megabytes, gigabytes of SRAM?
I would think no -- you would definitely need hard real time for something like this. But my only experience with real time systems is in tiny MCUs with kb of SRAM. That's definitely too small for a controller like this.
Really curious about the nuts and bolts of this.
When you build something like this, you're torn between having a big model that represents everything and a smaller model that is easier to validate and reason about. Based on simulation, you might go for a smaller model that "knows" to stay away from operating areas where hidden variables (like really complicated tank slosh) invalidate the small model.
I doubt the actual control loop is too much processing, but it's certainly possible to build controllers with SDRAM, millions of variables of state, and hard realtime processing, though I wouldn't build it on top of preempt-rt. ;)
https://ntrs.nasa.gov/api/citations/19700023342/downloads/19... (search for "slosh" or "shaping network")
My stepfather worked as a programmer on the Apollo program, and the thing he always talked about as his biggest accomplishment was working on the "slosh problem" -- so yeah, props to the SpaceX team for managing that landing. And props to my stepdad for managing it on hardware that was... a billion times less capable? :-)
I am curious but clueless about these problems, can you expand more?
Well, that makes perfect sense considering that both the spaceport infrastructure, and the booster need to do their calculation on the ground level instead of the highly radiated environment that is space. However, for the rockets themselves, which happen to reach that harsh environment, they may use more resilient and expensive hardware in the future, after passing over the current "let it splash in the Indian Ocean" development and testing phases.
Surely this isn't necessary with a small enough sensor granularity or whatever the terminology is. You can have very dumb software if it reacts quickly enough to changes in perception.
Instead, it's more common to use gasses injected at the top of the tank to push the liquid to the bottom. Falcon 9 uses helium. Starship uses https://en.wikipedia.org/wiki/Autogenous_pressurization as well as small header tanks for the landing propellants.
Where his vision hit a lot of speed bumps is second stage reusability. Starship is a beautiful second stage to throw in the ocean. They’ll probably get it landing but the heat tiles will require a lot of refurbishment between flights. They’re going to have to figure something else out.
This likely means they are targeting 10 flights in a day at least. They've mentioned 1000 trips to Mars during one transit window, which means ~10000 Earth launches within 3 months, or >100 per day.
"Is there a word for that - something out of fiction becoming mundane?"
Musking?
But I lump both these together as the *"Wiseass Movable Feast"*
Fuel is the vast majority of the vehicle weight at launch, kind of like an empty vs full can of soda.
They ignite a subset of engines just a few seconds before landing for the final slowdown and maneuvering.
Edit: here is a video from further away that shows the rocket gliding in under control of the grid fins before the engines light and execute the final landing maneuver:
https://x.com/shaunmmaguire/status/1845444890764644694
They sure made it look easy...
Surprising to see this work first time though - I don't recall them doing any hover and lateral movement tests, but I assume they must have done.
What's also wild is that the booster isn't being caught/supported by those giant grid fins, but rather by small lifting pins just below them, and seems to only have two of these (one on either side), so it also has to get it's rotational position right so those pins engage with (are supported by) the arms.
Watching the video, it looked like the bottom of the rocket was glowing hot, but the engines were cool. I imagine that means they were probably running some amount of methane through the engine bells to cool them.
Also I don't think the telemetry on the feed is that accurate, so with all of the atmospheric braking, it was probably going a bit slower than the 1200km/h at engine reignition.
Going by the telemetry of the seconds before the landing burn and noting the speed vs time, it seems drag was around 40 m/s^2 when it was going at around 3000 km/h. Since drag depends on velocity squared though, it had reduced to just above 10 m/s^2 just before the engines lit at 1250 km/h, and so would quickly become negligible once the engines lit.
Going by Wikipedia, the Super Heavy[1] has 3400000 kg of fuel at launch, so 3% of that is about 102000 kg. For the landing burn, it used 13 Raptor v3 engines[2] to scrub speed. Each Raptor flows about 650 kg/s max, so 3% fuel is enough for about 12 seconds for the 13 engines.
The empty mass of the Super Heavy is about 275000 kg, so about 377000 kg before the landing burn with 3% fuel.
Using the sea-level vs vacuum performance of the Raptor v2 engines, one can estimate that each Raptor v3 produces about 2.45 NM of force at sea-level. So 13 of them would produce about 31.85 MN of force.
Using Newton's second law, F=ma, this gives an initial deceleration of about 84 m/s^2 and about 104 m/s^2 when empty. If we do a rough spreadsheet integration, we get that a burn of roughly 4 seconds is needed to scrub the speed assuming no other forces.
Now, comparing this with reality, the full 13 engines were lit for a little over 5 seconds.
In my simplified calculations I was assuming full throttle the whole way, which obviously isn't realistic, and I also assumed 3% fuel. So over all I think that's a pretty decent estimation.
[1]: https://en.wikipedia.org/wiki/SpaceX_Super_Heavy#Engines
[2]: https://en.wikipedia.org/wiki/SpaceX_Raptor
So, 34M kg of fuel has to be burned (in this booster alone) to facilitate a flight ... and I see that the propellant is CH4 / LOX[1].
Burning methane is much, much better than simply releasing methane but the release becomes CO2 instead ...
What is the back-of-the-envelope conversion of 34M kg CH4 vs., for instance, 34M kg of kerosene/JP ?
[1] https://en.wikipedia.org/wiki/SpaceX_Super_Heavy#Engines
[1] https://www.engineeringtoolbox.com/co2-emission-fuels-d_1085... [2] https://x.com/elonmusk/status/1298426245991063554?lang=en
IIRC there's a tradeoff between efficiency and thrust as well. Heavier fuels aren't quite as energy-efficient, but it's easier for them to develop a lot of thrust, which is important for the initial stages of launch. If I'm remembering events described in Ignition! correctly this led to "thrust density" being something that was optimized for - to the point that there were experiments with mixing mercury into the fuel!
[0]: https://world-nuclear.org/information-library/facts-and-figu...
[1]: https://en.wikipedia.org/wiki/Kerosene
Long ago though so rusty, $dayjob doesn't involve any advanced math at all.
edit: To expand, the "rough spreadsheet integration" was just the Euler method[1] assuming a constant acceleration. So
The acceleration comes from F=ma as mentioned, where F is the force of the engines (Newtons), m is the mass of the rocket (kg) and a is the acceleration (m/s^2). Solving for a we get a = F/m and we get To make things easy I assumed the weight of the rocket was constant at each timestep, but if we take dt to be small enough it's a decent enough approximation. For each timestep I also updated the mass using the estimated mass flow: I started with m(0) = 377000 kg, v(0) = 1250 km/h = 347 m/s, and a constant -31850000 N force from the engines.Using dt = 0.1 seconds, I got almost exactly 4 seconds until the velocity reached zero.
[1]: https://en.wikipedia.org/wiki/Euler_method
That should of course be 13 * 650 * dt.
Anyway, plugging in the Raptor V2 thrust numbers the approximation increases to 4.25 seconds. This is in line with the thrust I used for the V3 being ~8% higher than the V2 thrust figures.
The last part of the live stream they showed footage from a different angle and there it didn't look too bad though! For sure controlled.
Scott Manley put out a tweet that they went down towards a non-tower position until they were at three engine controlled burn, and only then did the side shift.
Check Steve Brunton youtube channel, he is one of the leaders in this area: https://youtu.be/gb_C9LcjDSI?si=xUjqUZ9-0MIFohX6
does anyone have any literature about how the Rocket localized itself with respect to the chopstick arms? It must've been some combination of GPS and Radar pings to the arms?
And then the onboard IMU to make sure it hits it straight.
https://www.youtube.com/watch?v=tVSPCPoc8hs&t=373
To speculate more, they could also be using something like ultra-wide band positioning. This relies on the same time-of-flight principle as GPS but instead of using satellites in orbit to provide the precise time information you rely on various nearby ground stations. Would only be useful right at the final approach, the last couple hundred meters, but it's another way they could get very very precise position information. (fun fact: Ultra Wide band positioning is also how iPhones can locate AirTags with centimeter accuracy)
In the wide open sky, I’m guessing it’s pretty reliable.
Vision systems would be pretty useless with the low visibility of the smoke and fire. So I thought maybe it was some kind of radar configuration.
Anyways, I’d pay a lot of money to pick the brain of the GNC team here.
https://x.com/shaunmmaguire/status/1845444890764644694
Absolutely impressive accuracy and precision.
Of course I’d rather they just stream to YouTube in 4K.
It’s intentional
It's like a rite of passage, I imagine most people looking for a SpaceX launch fell for it once
Personal attacks in particular will get you banned here, so please don't post like this.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.
Here. Or try Space Affairs on YouTube
The older we get, the likelihood that we get scammed approaches one. Be weary.
Daily trips to space likely also mean more debris in space and falling to earth.
I hope there is a balance that includes the lives of people near these sites and all of us sharing the same atmosphere.
Maybe a future architecture with more redundancy could get there someday.
Regardless of the (in)accuracy of ChatGPT, you're assuming a lot can be accomplished with those flights. I strongly suspect 600K cars getting people where they need to go has far more utility than 1K flights of anything into / out of NEO.
> Debris is an absolutely non-issue.
Astronomers probably don't want 1000x (or even 10x) as many satelites obstructing their view.
> There is zero environmental downside, only Luddite foot stomping.
Name calling isn't going to help your cause. And the luddites had a good point, they didn't mind innovation. They minded being cut out of the benefits of innovation without any say in the matter.
https://news.ycombinator.com/newsguidelines.html
https://news.ycombinator.com/newsguidelines.html