This is fascinating, but I can’t believe he didn’t really address the elephant in the room (for me anyway). The instant the payload is launched, the launching mechanism will still be rotating at several hundred RPM but will no longer be balanced. I don’t see how it wouldn’t proceed to immediately and spectacularly tear itself apart. So they must have figured out how to rebalance it almost immediately. THAT is what I’d really like to hear about; that seems like the hardest aspect of the whole process.
Yeah, I didn't see any explanation for that either. With that much kinetic energy around I wonder if it's designed to simultaneously launch a portion of the counterweight.
It's got a lower lever so the overall momentum might be low enough to make that recoverable. Maybe if it's 10% of the rocket's momentum, going into... yeah, it's hard to imagine that being recoverable but maybe it's just weights and that's good enough.
He mentioned it toward the end, but did not describe the solution. I'm thinking the counterweight on the other end would need to move a very precise distance in effectively zero time.
EDIT: hmm, or a supplemental weight on the payload side, moving outward the right distance as the payload releases.
It seems like you'd generally want the non-payload rotating bits to vastly outmass the payload, so its release perturbs the whole system to the least amount possible. And then you use regenerative braking to reclaim the energy .
You could slam a blast door closed behind the exiting projectile. It should be possible to place it in the exit tunnel so that it is fully closed before the inrushing atmosphere gets to it.
I wonder why they don't just have an inert concrete mass on the other side and an exit port that opens into a sand bunker, sure it's a lot of energy but they don't have to contain it, only limit back splash from the mass hitting the sand. Doesn't even need to be enough sand to stop the mass completely, just enough to catch fragments, the mass can continue into the earth with no consequences
What I came up with was this: the launch arm has a second mass inside it, that will move (via centrifugal force) away from the center, in the same moment the payload is released.
Of course, just having two payloads launch in opposite direction as you propose maybe has much less implementation problems (though I wonder how you stop that second dummy payload in a way that does not cause an earthquake or explosion :)
Scott Manley talked on youtube about the centrifugal force on the wheel being around 10 thousand g (in the full sized version). So how do you build something that touches a tunnel at hypersonic velocity with many thousand tons of force without disintegrating? It's not like you can just add wheels or skates to your ejected mass (or the tunnel).
If you take the simplest design then the second object would be launching into the ground, which is basically what they're doing with the counterweight.
Alternatively you could have a contrarotating system, but I'd then be worried about two high speed objects travelling close together.
The best solution would probably be a metal counterweight, so that you can regeneratively decelerate it from it's exit port.
You got me curious, so I dug up their patent. This is as close as they come to addressing it.
> Although not shown in the previous figures, the circular mass accelerator structure 150 may comprise a second exit port directly opposite the exit port 115 to capture the counterweight 135 that is released simultaneously with the launch vehicle 105 to minimize an imbalance on the motor at the time of release. The counterweight 135 may be a solid material, or a liquid such as water.
The use of a liquid is a curious idea. Perhaps it could be dispersed in such a way as to spread the force of the counter weight being released across a wide surface area? Like a small explosive forces the liquid out in all directions?
Whether liquid or not, running the formula for kinetic energy of the counterweight, I'm getting something around 1 GJ (gigajoule) for a weight of 1 ton at 1500 m/s [1].
According to this site [2] that's equivalent to around 200 kg of TNT. Even with the counterweight being mostly water, that's quite a lot of energy to disperse. How does one evenly spread out the water to a surface the size of a football field? Would that even be enough area to prevent a shock wave being reflected back at the launch equipment?
There's a slide in Manley's video that says gross vehicle weight is 11,000 kg. And 450 RPM @ 100 m diameter, so 2 km/s. Kinetic energy for vehicle is 22 GJ. Equivalents:
* 5 metric tons TNT
* 1/3000 Little Boy atomic bomb
* 4 barrels of crude oil (!)
* Boil 2,300 gallons of water
* 0.25 mg of matter converted to energy
* Enough energy to melt two 11,000 kg iron counterweights, with 2 GJ left over
Build the thing on a sea platform. Launch the counterweight into water. Make it sharp-nosed like the payload, so it could potentially survive impact with water and be recovered.
I was guessing, its water in a container with bomb bay like doors, when the payload is released the doors open and the water goes into some complex structure that takes the energy out of the water. but only a guess.
I wonder how much lower the g forces would come than from 10k if the radius was larger. The high energy particle accelerator at cern comes to mind. It wouldn't need to be vertical either just at a slight tilt since to go to orbit you need to travel horizontally most of the time.
I don't see how this is viable as an earth launch system. You have all this complexity and payload restrictions, just to go from a two stage launch system to... a two stage launch system.
However, I think this technology will be extremely valuable for launching material from the moon.
So kudos for investing for this. And I think it will even end up being a profitable investment. Just not for the intended purpose.
I'm having trouble understanding how practical this could be. Do you know what tests they've done to find out what kinds of things can survive the extreme acceleration? Do you know what the force from impacting the atmosphere upon leaving the spin chamber is?
Cool to see some new ideas here. Saturn V burned nearly 200 tons of propellant by the time it cleared the launch tower. Tsiolkovsky got us to the moon but he won't get us to the stars.
It's enticing because what if you could use this to put fuel and/or parts into orbit to assemble a second stage rocket for interplanetary travel? That'd be sick.
I suppose it partly depends on how high you can reach (LEO?) with this method and whether your spun rocket can carry a fuel payload itself.
The launch mechanism doesn’t have to point straight up; it could point at an angle. Of course that will lengthen the distance traveled through the atmosphere, but maybe it could still work if the launch vehicle can withstand enough heat.
Doesn't matter what angle you throw it. An object in orbit always returns to its starting point. When the object is released, its orbit intersects the ground (unless it reaches escape velocity). If you want to change the orbit so it no longer intersects the ground, you must impart a huge velocity change to the object after it clears the atmosphere, and the only practical way to do that is to include a rocket engine and propellant and avionics in the payload.
That's a very clear argument. Can the effect of air resistance usefully change this, since it's a force acting on the object after it's released? It seems like it's quite bad that the force always points directly opposite the velocity, and I imagine there's a straightforward argument that this can't "improve" the orbit, but I'm not sure offhand how to incorporate that into the analysis.
I think you might be right, the atmosphere might be able to help you a little. However, any orbit you obtained by interaction with the atmosphere would still intersect the atmosphere, and so would decay rapidly. You'd still need a rocket to boost up afterward. Maybe it could reduce the amount of propellant necessary.
Air resistance applies a force opposite to the direction of travel (retrograde). At any given instant, the effect is to not change your direction of movement, but decrease your speed of movement. A retrograde force will always lower every point of your orbit (except the exact point where the force was applied, which would remain on your orbit). Since your orbit already has a point that intersects the surface of the planet, your new orbit must also intersect the surface.
One minor complication: Technically, air resistance applies a retrograde force relative to the direction of the wind. At low speeds this might actually increase your orbital velocity. However, the speeds where this is relevant are so small that they are not worth consideration.
Just did some quick stubby pencil work, a 2 foot diameter pipe would have to be pumping the propellant at around 70 mph in order to move that much liquid.
Just the lateral deceleration of the liquid slowing down in the tank would probably provide a couple tons of thrust.
Why not just build couple extra O’Neil cylinders on orbit, run checkouts while populating them over 2-3 generations, and shoot it out? No reasons the majority of interstellar crews has to be Earth born.
Solid rockets had more carrying capacity at one sixth the cost of Saturn 5 at the time. Is the ultimate launch system rated human-safe a combination of spinlaunch, solid rocket boosters to reach highspeed for airbreathing ram/scramjets and lastly transition from airbreathers to liquid propellants?
is this really more efficient than just launching the rocket normally with chemicals?
the article doesn't really go into detail but alludes to the answer to my question being "yes".
I guess the idea is:
you can spin a smaller rocket which requires energy EnergySml. Alternatively you could have a larger rocket which requires EnergyLrg to get out of the atmosphere.
So EnergySml + Fuel in rocket to leave atmosphere << EnergyLrg (which is launch + leave atmosphere)?
---
other questions I had were:
- wouldn't the rocket being spun have to be heavier than the equivalently sized chemical rocket because it has to be able to survive being flung around in a centrifuge?
the important thing I think is that your energy-consuming device (the spinny part) can be huge and heavy and remain on the ground, so it doesn't need to be designed like a rocket first stage. Even if it's actually really inefficient in terms of watt-hours used to spin the thing, doesn't matter.
You don't have to lift the fuel. A huge proportion of the fuel in a rocket's first stage is used to lift the fuel in the first stage off the ground for the first few hundred metres of flight. It's almost diabolically inefficient.
Using a really big cannon, not entirely unlike in the Jules Verne novel, has been investigated seriously. It has similar efficiency benefits. Some limits on what can survive the acceleration though: https://en.m.wikipedia.org/wiki/Project_HARP
I knew this would come up in here. Gerard Bull was an amazing character. Unfortunately he was screwed by few governments and at the end he was assassinated (presumably by Mossad).
Makes me wonder about the military uses of such tech. Remember Gerald Bull and his quest to launch a satellite with an artillery piece? He later was embroiled in a project for Iraq to create a supergun that could potentially provide ICBM tech to a country without rocket tech.
I wonder how big it would have to be to even consider putting people on it, albeit sleeping ones. A younger me would look up the required velocity and do the math. A slightly older me is going to sleep soon and will dream that one day he gets to get into the space flinger.
Arthur C Clarke proposed the idea in 1950 in a paper, and wrote a rather excellent short story about the concept (and a wild escape from a launch failure) called "Maelstrom II".
In Clarke's story, the launch system is located on the Moon rather than Earth; the lower escape velocity and lack of atmosphere makes the fictional engineering a lot simpler (and allows the climax of the story, which I won't spoil).
When I was younger those devices were called “mass drivers”.
The idea was crude materials would be cut up from moons and asteroids, and launched using maglev rails towards civilization centrals. Or it can also be used for recovery, so long that the landing spacecraft can successfully mate the train.
Above is portrayed first, in cases with Sci-Fi novels, then of course something terrible would occur, and the story starts to ramp up. A shivering refugee is found inside, one of containers suspiciously veer off course, the crucial docking latch breaks, etc.
This is a hard part (which sounds impossible to me): since all acceleration needs to be done in a spinner, you need to get to 7900 m/s (even assuming no braking from the atmosphere).
And a = v^2 / r will turn living things into a paste for sane r. :(. I would love to be refuted.
"Braking" will commence immediately after exiting the spinner apparatus though. And commence rather unceremoniously. I don't think this is going to carry humans in the foreseeable future.
Really big. Escape velocity is 11km/s. Acceleration in a circle is velocity squared divided by radius. Assuming you can withstand 10g with proper gear and drugs that's a radius of a thousand kilometers.
What about putting up something heavier, like a counterweight and a cable? Suppose the radius of the spool is a lot bigger than the launcher, and there's some kind of clutch / synchro to bring it to speed when it engages...
So you will only be able to send payloads that can handle such immense G-force pressures, I imagine? Humans can be ruled out then unless you want hominoid scrambled eggs in space
Perhaps this can also be used to send a continuous stream of supplies, such that we could have a true, inhabitable space station, where all the components required for space travel are manufactured and assembled in orbit.
I wonder if this could be used in a rifle type design, where the "spinner" would carry an impactor that would push against the space-bound rocket/projectile, to avoid (some) of the high g-forces?
Yes there would definitely be quite a bit of force at impact time, but the projectile wouldn't have to experience an hour of high g-forces, just a few moments.
You can build something like this, but much bigger, and with no external casing, on the Moon or anywhere with little or no atmosphere.
Professor James Longuski and his students at Purdue University have done quite a bit of research on this idea over the years. They call it a tether sling. To keep the tip acceleration (v^2)/r low, you want a large r. Some papers:
The LHC uses electric and magnetic fields to accelerate charged particles to near the speed of light inside a circular vacuum tube.
To picture a tether sling, imagine a lighthouse on the Moon with a giant arm sticking out of its side, and the arm can revolve around the lighthouse like a merry-go-round. The thing to be launched goes at the end of the arm. Just spin up the arm and let go!
Sorry I meant for a solution that would work on earth. Couldn't we use magnets to accelerate the ship like a maglev train inside a version of LHC with wider tubes?
IIRC, Alastair Reynolds describes something very much like this in his novel Blue Remembered Earth, which is set on a future Earth about 140 years from now.
I am no scientist, I just used to play in playground as a kid and watched allot of figure skating.
When something is rotating as you said, their mass is away from the rotation point, you can increase the rotation speed by moving the mass closer to the rotation point.
When the skater spins with their hands open they gain rotation speed by just gather their hand around the body.
When the kids spin on the round game, they get closer to the center to gain speed and away to slow down.
Is this a thing? Does this actually translates to increased centripetal force? Why they didnt get more speed by using this method?
In principle this would work. If they had a spinning mass, then moved the mass closer to the center of rotation, its speed would increase. The reason they do not do this is that it is just not that useful in this context.
One of the major limitatinos of the SpinLaunch approach is the g-forces. As it is, objects launched by SpinLaunch experience a g-force on the order of 10,000G. For a constant velocity, this force goes up as the inverse of the radius. As a result, you want the mass to be as far away from the center as possible so that the g-force experienced is minimal.
The other problem is that this approach is not actually an efficient way of gaining speed. Conservation of energy is still a thing. The rotating mass experiences an apparent centrifugal force pushing it away from the center of rotation (the 10,000Gs that I mentioned above). In order to move move the mass closer to the center, you must counteract this apparent force. At that point, you are likely better off taking the energy you would spend pulling the mass towards the center and simply apply it directly towards increasing the rotational speed.
> In principle this would work. If they had a spinning mass, then moved the mass closer to the center of rotation, its speed would increase.
Actually it wouldn't speed up. The speed of the mass traveling on it's circular path around the center remains the same. The orbit just becomes smaller and thus the path becomes shorter. The mass now makes more rounds in the same time. It is thus spinning faster around the center but traveling at the same speed on its path around it.
It is a common and understandable error to assume that the linear velocity should remain constant.
If the object goes in a circle, the radial force always acts perpendicular to the direction of motion, and cannot change the linear velocity of the object. The centripetal force does not do any work, the energy of the rotating body remains fixed.
But there is a subtle difference when one does pull the object closer to the axis. First, it is easy to notice that one does expend work. This energy must go somewhere, and there is nowhere else for it to go except into the kinetic energy of the moving object.
But how exactly is this energy transferred? If you think about it, when the object is pulled in, it no longer goes in a circle, but follows a spiral. Its velocity is no longer strictly perpendicular to the direction of the force. If you integrate this seemingly small effect, this is precisely what makes pulling on the sting to increase the velocity of the object.
Ignoring the mechanism, a formal calculation, from conservation of angular momentum or conservation of energy would immediately tell how much the linear velocity of the object would increase when it is pulled closer to the axis.
If you were on the moon you would only need to match spinlaunch's launch velocity of 8000 km/h and you wouldn't even need rocket fuel. You would only need a $200 battery and a $200 solar panel to fling 1 kg into space every hour of the day, assuming 100% efficiency.
I was quite surprised to discover how cheap it is to fling chunks of the moon into space. I mean... I'm not sure why you'd bother, but still, it interested me.
(My working: 2380 m/s escape velocity, 0.5 * 2380^2 energy in Joules required, convert to kWh, googled battery and solar panel costs, totally didn't consider efficiency anywhere)
now you have me imagining some strange field of lunar rock flingers, ejecting mass into space ceaselessly until the sun stops, all for a very motivated PhD student's thesis
I would be very carefull with any climate intervention where there is no easy way to adjust the effect. Preferably whatever we do should be part of a designed-in feedback loop to stabilize the climate.
You wouldn’t bash in a window at work if the office is too hot. It is super easy to see that that is a hard to undo intervention you might regret later. The climate of a whole planet is much more complex than that, much less well understood and we only have one. Be suspicious of any plan which doesn’t have “knobs” we can adjust as we learn more.
Also we now maybe have the tech to make moon trebuches to fling dirt to shade our planet. Do we have the tech to clean it up too if it blows back in our face? Will we always have the tech? Civilization is not a straight linear progression. Even if we could do the adjustment now who knows maybe thousands of years from now humanity won’t be able to do the same. So it is better if we design our interventions such that they are making the climate stable even without continous tweeking by a technologically advanced civilization. I don’t know how this would be possible without properly designed feedback loops. And I don’t know what feedback system a dust cloud could have.
> I was quite surprised to discover how cheap it is to fling chunks of the moon into space. I mean... I'm not sure why you'd bother, but still, it interested me
Mass drivers are powerful weapons. Haven't you read the classic "The Moon is a Harsh Mistress"?
If your goal is a weapon system, there are far, far better options. Like rods from god and orbital nuke launchers, it just has too many limitations to be practical.
How about liquid oxygen and aluminum tanks made from high-temperature electrolysis of regolith? Now you have rocket propellant and parts. 90% of the propellant mass that Starship uses is oxygen. If you could refuel Starship in space this way, it would reduce the number of launches needed from 10 to 1 (well, maybe 2 if the lower-density liquid methane is too bulky for one launch).
Wouldn't something like a rail gun be simpler? Its basically just a maglev train than carriers a spacecraft. Admittedly a large spinning wheel may be simpler to aim than a few hundred meters of track though.
The tricky thing about using a rail gun is that you need to deliver all the power very quickly which is hard and expensive. With this launch system you can spin it up slowly by feeding in energy and then release the projectile once you're up to speed.
That first part is correct; gravity is measured in units of acceleration.
But I have no idea what you mean by "velocity squared". If you mean the ordinary sense, of multiplying something by itself, you're wildly wrong. Acceleration is the derivative of velocity with respect to time, dv/dt, and it is measured in units of velocity over time, not units of velocity squared. Its magnitude is unrelated to the magnitude of velocity.
This is probably a silly question, but for the test run, did they launch the rocket straight up? From my limited understanding of gravity, I’d expect it to come straight down if anything went wrong, and it looked like there were quite a few things for it to come down on.
Edit: looking at the video closer, it looks like there is a slight angle to the launch, tilting away from the building next to it, which makes sense.
You're not throwing the ball high enough in a car that the difference in radius from the center of the Earth makes a difference that you can detect.
For objects above the earth's surface, the radius of the 'orbit' around the center of earth increases, and thus the 'forward' component of the velocity has to increase in order to stay over the same point on the earth. If you shoot something high enough straight up, it will land to the West of the point it was launched from. (This does ignore effects of wind and such, but I believe so did your argument).
It's nothing like throwing a ball up from a running car. Look up the physics of rotating reference frames. I'm sure others can explain it better than I can.
I think that requirement of “high enough” is why I was surprised, given that a) it was a 1/3 scale model, b) it was a trial run, and c) things frequently go wrong. I guess sitting below it shows their confidence in its ability to get things up there!
Edit: that being said, it does look like there is a slight angle.
I did see that, and that’s what I would expect for the full version (much like launching rockets over the Atlantic from Cape Canaveral). Just a little surprised to see it looking a little more vertical for the trial run.
It most likely has a self-destruct sequence. It's basically the same as firing a missile so I wouldn't be surprised if the same type of persuasions were taken as when military drills take place.
This video is really weird because usually a launch video that has all the theatrics of a Hollywood production (all white launch room with dramatic lighting and shallow depth of field cinematography) would usually be done by trust-fund startup LARPers, but they actually built this shit and launched it which is not characteristic of a LARPer.
This is getting pretty close to science fiction. I wonder how much crazier future science fiction writers can get. They're running out of imaginary ideas that hasn't turn out to be real.
If one's spacecraft missed the skyhook on arrival, it could not decelerate and would fly off into space. The thought is terrifying. The film Aniara deals with this scenario. Spacecraft relying on skyhooks for deceleration would need lifeboats that can decelerate and return to the destination after a missed skyhook rendezvous.
This is quite interesting, recently I watched video explaining similar rail-gun/cannon concept, end explanation what would it take to work for human payload.
What kind of training is there to survive 38G for 0.5s? Maybe the body can become habituated to accelerations over time or something, but what would you be training to actually do before or during those 0.5s?
Physical training I guess, trying different G's for long time, exercising breathing under elevated G's ... I do not know, I just wrote what author said in video.
Not without problems though. He "sustained a fracture of his right wrist during the runs on two separate occasions, also broke ribs, lost fillings from his teeth and bleeding into his retinas that caused temporary vision loss".
This is during short periods (of deceleration), so very different from SpinLaunch's launches.
Yeah, that's probably the right take. They are removing a stage though, the implied third stage, but SpaceX is already doing that with better rocket engineering.
Compare the SpinLanch rocket specs [1] to Electron in [2].
Payload: 200kg vs 300kg
Height: 6m (est) vs 18m
Wet mass: 11t vs 13t
Stage 1 thrust: 75kN vs 230kN
Stage 2 thrust: 5kN vs 26kN
Engines: Pressure fed vs Electric pump fed
The SpinLaunch rocket dumps its shell before turning on its engines, and presumably has much lower gravity losses, so despite shockingly similar wet masses, the rocket and its engines can be greatly downsized.
I don't have any solid opinion about the concept, but it does seem like “smaller tanks” is maybe not the best description of what is a fairly significant design change. You do shed a lot of complexity from the propulsion systems, but I'm far from sure the stuff you add is any cheaper.
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[ 2.4 ms ] story [ 159 ms ] threadhttps://www.youtube.com/watch?v=xAfdSak2fs8
It's got a lower lever so the overall momentum might be low enough to make that recoverable. Maybe if it's 10% of the rocket's momentum, going into... yeah, it's hard to imagine that being recoverable but maybe it's just weights and that's good enough.
I'd love to see a real explanation.
EDIT: hmm, or a supplemental weight on the payload side, moving outward the right distance as the payload releases.
It seems like you'd generally want the non-payload rotating bits to vastly outmass the payload, so its release perturbs the whole system to the least amount possible. And then you use regenerative braking to reclaim the energy .
What I came up with was this: the launch arm has a second mass inside it, that will move (via centrifugal force) away from the center, in the same moment the payload is released.
Of course, just having two payloads launch in opposite direction as you propose maybe has much less implementation problems (though I wonder how you stop that second dummy payload in a way that does not cause an earthquake or explosion :)
> Although not shown in the previous figures, the circular mass accelerator structure 150 may comprise a second exit port directly opposite the exit port 115 to capture the counterweight 135 that is released simultaneously with the launch vehicle 105 to minimize an imbalance on the motor at the time of release. The counterweight 135 may be a solid material, or a liquid such as water.
The use of a liquid is a curious idea. Perhaps it could be dispersed in such a way as to spread the force of the counter weight being released across a wide surface area? Like a small explosive forces the liquid out in all directions?
https://patents.google.com/patent/US10202210B2/en
According to this site [2] that's equivalent to around 200 kg of TNT. Even with the counterweight being mostly water, that's quite a lot of energy to disperse. How does one evenly spread out the water to a surface the size of a football field? Would that even be enough area to prevent a shock wave being reflected back at the launch equipment?
[1] https://calculator.academy/joule-calculator/#f1p1|f2p0
[2] https://www.convert-me.com/en/convert/energy/tntkg.html?u=tn...
* 5 metric tons TNT
* 1/3000 Little Boy atomic bomb
* 4 barrels of crude oil (!)
* Boil 2,300 gallons of water
* 0.25 mg of matter converted to energy
* Enough energy to melt two 11,000 kg iron counterweights, with 2 GJ left over
* A magnitude 3.7 earthquake [1]
[1] https://www.volcanodiscovery.com/earthquakes/energy.html
Doubtful even if pointy. Water is way denser than atmosphere
Little joke
However, I think this technology will be extremely valuable for launching material from the moon.
So kudos for investing for this. And I think it will even end up being a profitable investment. Just not for the intended purpose.
I suppose it partly depends on how high you can reach (LEO?) with this method and whether your spun rocket can carry a fuel payload itself.
One minor complication: Technically, air resistance applies a retrograde force relative to the direction of the wind. At low speeds this might actually increase your orbital velocity. However, the speeds where this is relevant are so small that they are not worth consideration.
Just the lateral deceleration of the liquid slowing down in the tank would probably provide a couple tons of thrust.
Maglev trains aren't science fiction anymore.
the article doesn't really go into detail but alludes to the answer to my question being "yes".
I guess the idea is:
you can spin a smaller rocket which requires energy EnergySml. Alternatively you could have a larger rocket which requires EnergyLrg to get out of the atmosphere.
So EnergySml + Fuel in rocket to leave atmosphere << EnergyLrg (which is launch + leave atmosphere)?
---
other questions I had were:
- wouldn't the rocket being spun have to be heavier than the equivalently sized chemical rocket because it has to be able to survive being flung around in a centrifuge?
Using a really big cannon, not entirely unlike in the Jules Verne novel, has been investigated seriously. It has similar efficiency benefits. Some limits on what can survive the acceleration though: https://en.m.wikipedia.org/wiki/Project_HARP
That could be extremely complex, unless (perhaps) the rocket using solid boosters, in which case, you are spinning a highly volatile mega bomb.
http://www.youtubemultiplier.com/618f3abec89ec-you-spin-me-r...
https://en.wikipedia.org/wiki/Supergun_affair
have seen it described as the "canadian iraqi space gun", which causes some people to do a double take
[1] https://en.wikipedia.org/wiki/The_Fist_of_God
Edit: and not come out as human paste
I do wonder how a Hyperloop kind of long tunnel, vacuumed out would be a less-G substitute.
In Clarke's story, the launch system is located on the Moon rather than Earth; the lower escape velocity and lack of atmosphere makes the fictional engineering a lot simpler (and allows the climax of the story, which I won't spoil).
The idea was crude materials would be cut up from moons and asteroids, and launched using maglev rails towards civilization centrals. Or it can also be used for recovery, so long that the landing spacecraft can successfully mate the train.
Above is portrayed first, in cases with Sci-Fi novels, then of course something terrible would occur, and the story starts to ramp up. A shivering refugee is found inside, one of containers suspiciously veer off course, the crucial docking latch breaks, etc.
This is a hard part (which sounds impossible to me): since all acceleration needs to be done in a spinner, you need to get to 7900 m/s (even assuming no braking from the atmosphere).
And a = v^2 / r will turn living things into a paste for sane r. :(. I would love to be refuted.
The payload would have a rocket stage after reaching a certain altitude to further accelerate.
"Braking" will commence immediately after exiting the spinner apparatus though. And commence rather unceremoniously. I don't think this is going to carry humans in the foreseeable future.
Professor James Longuski and his students at Purdue University have done quite a bit of research on this idea over the years. They call it a tether sling. To keep the tip acceleration (v^2)/r low, you want a large r. Some papers:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=long...
Note 1: Professor Longuski was my PhD advisor, but I never did any research on tether slings myself.
Note 2: Others have also researched tether slings. The papers linked above give many citations to related research.
To picture a tether sling, imagine a lighthouse on the Moon with a giant arm sticking out of its side, and the arm can revolve around the lighthouse like a merry-go-round. The thing to be launched goes at the end of the arm. Just spin up the arm and let go!
When something is rotating as you said, their mass is away from the rotation point, you can increase the rotation speed by moving the mass closer to the rotation point.
When the skater spins with their hands open they gain rotation speed by just gather their hand around the body.
When the kids spin on the round game, they get closer to the center to gain speed and away to slow down.
Is this a thing? Does this actually translates to increased centripetal force? Why they didnt get more speed by using this method?
One of the major limitatinos of the SpinLaunch approach is the g-forces. As it is, objects launched by SpinLaunch experience a g-force on the order of 10,000G. For a constant velocity, this force goes up as the inverse of the radius. As a result, you want the mass to be as far away from the center as possible so that the g-force experienced is minimal.
The other problem is that this approach is not actually an efficient way of gaining speed. Conservation of energy is still a thing. The rotating mass experiences an apparent centrifugal force pushing it away from the center of rotation (the 10,000Gs that I mentioned above). In order to move move the mass closer to the center, you must counteract this apparent force. At that point, you are likely better off taking the energy you would spend pulling the mass towards the center and simply apply it directly towards increasing the rotational speed.
Actually it wouldn't speed up. The speed of the mass traveling on it's circular path around the center remains the same. The orbit just becomes smaller and thus the path becomes shorter. The mass now makes more rounds in the same time. It is thus spinning faster around the center but traveling at the same speed on its path around it.
If the object goes in a circle, the radial force always acts perpendicular to the direction of motion, and cannot change the linear velocity of the object. The centripetal force does not do any work, the energy of the rotating body remains fixed.
But there is a subtle difference when one does pull the object closer to the axis. First, it is easy to notice that one does expend work. This energy must go somewhere, and there is nowhere else for it to go except into the kinetic energy of the moving object.
But how exactly is this energy transferred? If you think about it, when the object is pulled in, it no longer goes in a circle, but follows a spiral. Its velocity is no longer strictly perpendicular to the direction of the force. If you integrate this seemingly small effect, this is precisely what makes pulling on the sting to increase the velocity of the object.
Ignoring the mechanism, a formal calculation, from conservation of angular momentum or conservation of energy would immediately tell how much the linear velocity of the object would increase when it is pulled closer to the axis.
I was quite surprised to discover how cheap it is to fling chunks of the moon into space. I mean... I'm not sure why you'd bother, but still, it interested me.
(My working: 2380 m/s escape velocity, 0.5 * 2380^2 energy in Joules required, convert to kWh, googled battery and solar panel costs, totally didn't consider efficiency anywhere)
It is easier to send something to low Earth orbit from the Moon than from Earth.
Raw material for space station construction.
You wouldn’t bash in a window at work if the office is too hot. It is super easy to see that that is a hard to undo intervention you might regret later. The climate of a whole planet is much more complex than that, much less well understood and we only have one. Be suspicious of any plan which doesn’t have “knobs” we can adjust as we learn more.
Also we now maybe have the tech to make moon trebuches to fling dirt to shade our planet. Do we have the tech to clean it up too if it blows back in our face? Will we always have the tech? Civilization is not a straight linear progression. Even if we could do the adjustment now who knows maybe thousands of years from now humanity won’t be able to do the same. So it is better if we design our interventions such that they are making the climate stable even without continous tweeking by a technologically advanced civilization. I don’t know how this would be possible without properly designed feedback loops. And I don’t know what feedback system a dust cloud could have.
Mass drivers are powerful weapons. Haven't you read the classic "The Moon is a Harsh Mistress"?
Hmm. The Moon Is a Harsh Mistress builds a compelling case to do so.
After acceleration, you have 'jerk' V^3, which is commonly used, and then 'snap, crackle, and pop' which are less commonly used.
https://en.wikipedia.org/wiki/Jerk_(physics)
V^4 is also called jounce, and I know some vehicles have jounce bars, but I don't know if those are truly related.
That first part is correct; gravity is measured in units of acceleration.
But I have no idea what you mean by "velocity squared". If you mean the ordinary sense, of multiplying something by itself, you're wildly wrong. Acceleration is the derivative of velocity with respect to time, dv/dt, and it is measured in units of velocity over time, not units of velocity squared. Its magnitude is unrelated to the magnitude of velocity.
Edit: looking at the video closer, it looks like there is a slight angle to the launch, tilting away from the building next to it, which makes sense.
For objects above the earth's surface, the radius of the 'orbit' around the center of earth increases, and thus the 'forward' component of the velocity has to increase in order to stay over the same point on the earth. If you shoot something high enough straight up, it will land to the West of the point it was launched from. (This does ignore effects of wind and such, but I believe so did your argument).
There's a point at which you can no longer ignore the rotation of the earth.
Maybe the effect still isn't huge at the scales we're talking about but it's not straight up and straight down.
Edit: that being said, it does look like there is a slight angle.
The idea is, I think, to use this as a first stage. The second stage is a rocket that takes the projectile to orbit.
great video: https://youtu.be/dqwpQarrDwk
here it can be lifeboats, backup hooks, spacecraft with backup thrusters, separate mechanisms for moving people vs stuff, and potentially many more
https://www.youtube.com/watch?v=Rb6sxy3f7VE
Well train human can survive:
38G for 0.5s
9G for 2min
7.5G for 5min
https://www.youtube.com/watch?v=-4lVfrTcr0c
Not without problems though. He "sustained a fracture of his right wrist during the runs on two separate occasions, also broke ribs, lost fillings from his teeth and bleeding into his retinas that caused temporary vision loss".
This is during short periods (of deceleration), so very different from SpinLaunch's launches.
Payload: 200kg vs 300kg
Height: 6m (est) vs 18m
Wet mass: 11t vs 13t
Stage 1 thrust: 75kN vs 230kN
Stage 2 thrust: 5kN vs 26kN
Engines: Pressure fed vs Electric pump fed
The SpinLaunch rocket dumps its shell before turning on its engines, and presumably has much lower gravity losses, so despite shockingly similar wet masses, the rocket and its engines can be greatly downsized.
I don't have any solid opinion about the concept, but it does seem like “smaller tanks” is maybe not the best description of what is a fairly significant design change. You do shed a lot of complexity from the propulsion systems, but I'm far from sure the stuff you add is any cheaper.
[1] https://player.vimeo.com/video/573539093#t=26s [2] https://en.wikipedia.org/wiki/Rocket_Lab_Electron