Forgive me for my ignorance, since my knowledge of advanced physics and orbital mechanics are limited to KSP, can't we build something like this on orbit, thus saving a lot of headache from landing and constructing on the moon?
A stable polar orbit is easier to get to and return from the moon.
yeah my fault;
I interpreted the question as 'hey sounds difficult to do that, can't we make it easier?' in sense of the person asking without knowing the JWST exists.
The core of it is a liquid mirror which is harder to do in space because to shape it into a parabola you need spin and a down which would require constant acceleration since it want's to look at a single point in space. Also long duration attitude holding is harder in space than it is on the ground.
If we wanted to build something similar in space it's essentially a 5x larger James Webb Space Telescope which is having some trouble last I heard with it's folding mechanism so building one 5 times larger to fit into a faring is a big task.
OTOH in zero g a mirror needn't support its own weight. A shade would eliminate temperature fluctuation. Naively I'd expect it should be practical for a very large, very lightweight telescope mirror to be built in situ in space instead of trying to launch and unfold one built on Earth.
I guess the big problem for that right now is that for humans to do the building, it'd have to be in low orbit, a less-than-ideal environment for a long-lived scientific instrument. (Just kibbitzing, am not a rocket scientist.)
I mean the construction can be done on low earth orbit, then the satellite telescope can do a transfer to a higher orbit. Again, forgive my ignorance :)
We've only built a tiny number of things in orbit and haven't yet built something that then gets sent off somewhere like a shipyard. It's all been stations that are then left basically where they [0] are so we don't really have the experience of how to do that yet. Also that takes a long time because it's just slow to move around in space.
It does need to support it's own mass through during maneuvering and pointing operations as well so it can't be completely flimsy. Also you'd want to get further from the earth to avoid all that drag from a huge mirror in LEO.
I was fantasizing some form of active control, without the speed demand of in-atmosphere adaptive optics. This might be needed anyway after micrometeoroid damage.
Normally liquid mirror telescopes depend on having some amount of gravity to work correctly (the liquid needs to pool in a certain way). There's workarounds to do this in space but it gets really complicated.
Other issues with space based telescopes:
They need fuel + thrusters to go where you want them to be (or just to maintain their orbit!)
Heat dissipation is a big problem. Being able to use the whole moon as a thermal flywheel could help out a lot. In space you can use things like cryocoolers to regulate temps, but they cause vibrations which can be problematic if you need your telescope to remain steady. If this requires refrigeration, you can put the vibrating parts far enough away from the telescope that they don't move it. Putting the thing in a crater probably helps regulate temps too (less direct sun)
Humanity in general is better at building and maintaining things on solid ground. If you drop a bolt on the moon, you lean over and pick it up. If you drop a bolt in orbit, you have to worry about it damaging your spacecraft at the next conjunction.
It's hard to imagine how this could be easier or cheaper than just launching another space telescope. I see from the article that it uses a spinning liquid mirror, so yes, that would require gravity to work, but how many extra launches would it take to get the telescope to the moon and also the lander equipment.
I assume (its a shame the article didn't go into this) that the telescope would basically be a big fabric structure and it and the liquid mirror can be easily transported and set up without humans.
The magnification of the 100M mirror make up for the lack of being able to point it anywhere at a much reduced cost than a 'traditional' space telescope.
Yeah, well, right now a mining and manufacturing operation on Earth weighs more than the entirety of everything humankind has ever lifted into space, by at least an order of magnitude, probably several orders of magnitude. And it still relies on a worldwide transportation network to move materiel. We could build 10 JWST and still come in well under budget compared to developing that tech.
Just turning asteroid material to below average 3D printer feed could be a big and useful first step - just overengineer everything by a factor of 3+ and you can build a big part of your mining operation in place from local resources, to refine/proces/manufacture from the good stuff.
>Without an independent infrastructure in place at a lunar pole, it would likely be impossible to construct and operate a large liquid-mirror telescope.
Mercury does still have a vapor pressure and evaporates at room temperature so it could evaporate some but it would be in the shade so it would need warming to remain liquid more than cooling so the evaporation rate could be controlled and would probably be very very slow around it's freezing point.
It can't be in sunlight, or the telescope would be useless.
The problem would be more in choosing a material that has low enough melting point so that making up for the radiative loss to keep it melted wouldn't be a big issue and at the same time vapor losses can be managed. Which is why they propose separate materials for the mirror body and its surface I guess.
I think this might have been posted on HN recently. To me this is a far more appealing project. It could require very little payload weight, and it achieves something that is only really possible on the moon.
I would like this to be the project that really drives future human presence on the lunar surface.
Could we? I assumed the whole point was to use a crater as a ready-made, almost-parabolic dish, meaning that only the receiver and suspension wires would have to be sent over -- vastly reducing the required payload vs constructing an entire 1km diameter dish in space.
A crater isn't a dish, you need to line with with antennae. The extra material to support those antenna in free fall is minor.
But the cost difference in landing anything on the moon is massive. Every kilogram of payload sent to low earth orbit takes roughly 15 Kg of fuel. To land a Kg of payload on the moon requires roughly 80 kg of fuel.
It makes a sphericalcap reflector and shields from radio from the Earth and Sun. You may get something similar by putting a satellite in earth syncro orbit on the dark side of the moon.
Particularly – "Astronomers grouped stars in the order they were observed, so Pop I stars are present-day stars, with Pop II stars being one generation older. Pop III stars are the hypothesized oldest stars in existence."
SpaceX is purportedly at some point going to be able to put 100 tons in LEO for around 100M. I'll roughly assume with a second launch full of fuel, a purchaser with the right gear could put close to 100 tons on the lunar surface for 200M or so, once they get the kinks out and the price down.
So why not just pre-purchase 20 of these for your favorite lunar project, such as the ULT? If they bring prices down you get a cool lunar base. If they don't, you don't pay. That much payload delivered to the moon for $4B would be an incredible bargain, and it also serves to further incentivize SpaceX.
I'm sure I have something about the economics wrong, but I don't know what. Seems to me like we should be very close to a lot of back-burner space projects getting off the drawing boards.
The cost of rocket launches is not the largest part of creating a lunar base, designing and manufactoring all the landers, base, electronics, software etc. is the larger part of it.
If I recall correctly, for the apollo program about 30% was for the launch vehicle.
It seems like this would be somewhat of an interrelated valuation.
If launch costs decrease by an order of magnitude, reliability of payload can be relaxed, and therefore costs of payload engineering and manufacture decrease.
If mass reduction is no longer super critical, you can use heavier but cheaper materials that provide the needed strength.
There could be other knock off effect of cheaper and more frequent space launch - you can send multiple versions and see which works the best, ship prototypes back for extensive evaluation, send robots or people to fix broken things.
A lot of things are done differently if you have just a couple super expensive shots per decade & everything needs to work without external help at the first time.
I would assume engineering and building one of these things is non-trivial, and there may also be certain aspects tailored to the specific launch vehicle, so it’s not like as soon as SpaceX proves they can do what they plan to do that you can just pop a telescope on a rocket and go.
Launch providers list the characteristics of their vehicle and the customer has to ensure to stay within the constraints.
SpaceX is special (or used to be special, maybe others have followed suit by now?) in that they make this information public. See here what loads, accelerations or vibrations the payload has to withstand during a launch on a Falcon 9 or Falcon Heavy launch vehicle:
Imagine the same project (Lunar base? Moon telescope? Rocket fuel harvester?) but in the Sahara. Now add the constraint that you want it there, but without ever having any humans on site.
That is what needs addressing. That level of automatisation is the hard part about space.
Indeed. Slightly tangential, but when you start thinking about a Mars colony -- but here on Earth -- a self-sufficient hermetically-sealed environment somewhere underground -- it really starts to drive the scope of the problem home.
We don't really know how to create a self-contained ecosystem here on Earth, with everything on-hand. And the residents won't even all die if someone accidentally pokes a hole in the wall in the Antarctic prototype base.
Indeed. If we're going to be serious about extraterrestrial colonies we should be workshopping our solutions right now here at home where the problems and consequences are orders of magnitude lesser.
"Steve Bannon left Biosphere 2 after two years, but his departure was marked by an 'abuse of process' civil lawsuit filed against Space Biosphere Ventures by the former crew members who had broken in.[70] Leading managers of Biosphere 2 from the original founding group stated both abusive behaviour by Bannon and others, and that the bankers’ actual goal was to destroy the experiment."
Really more of a PR spectacle than a worthwhile experiment.
Including humans seems to have caused most of the problems there. If you actually wanted to experiment with closed biological systems in a useful way then I'd recommend doing a bunch of trials with a less cantankerous species of large omnivorous mammal, like the goat.
Biosphere 2 was originally meant to demonstrate the viability of closed ecological systems to support and maintain human life in outer space[0]
>including humans seem to have caused most of the problems
I chuckled a bit at your reply hvd.
The hardest, seemingly intractable problems in the world aren't engineering problems, they are human ones. If we want to level up as a species those are the ones we will need to figure out how to solve.
There was still some very cool engineering that went into making what it was supposed to be. Check out this video on the 'south lung' youtube.com/watch?v=Wind4fjbt_k
Because they didnt want air going in or out of the biosphere they had to figure out a way to account for the massive change in volume as the air temperature inside changes between super hot days and cold nights, otherwise you'd blow the windows out of the thing during the day.
I don’t know if I’d call it a total failure. There’s a pretty cool documentary about it an Apple TV+. I think if they had communicated the caveats better and more honestly then it would have been a success on the grounds of being a baby step towards the direction of the more ultimate case. I’d say the biggest success was showing that even with all the resources on earth available, this problem is non-trivial.
I don't see it as a failure? The first attempt needed a relatively small amount of oxygen injection (which is very much achievable for a Mars mission). The second achieved self-sufficiency.
Of course we have reason to do so (to test whether we can do it) and projects like Biosphere 2 suggest that while it's not impossible, it is for the time being unsolved.
One approach is to not try to make our colonies self-sufficient. Instead send a study stream of cargo missions to resupply them.
At first, that seems completely impractical due to the enormous fuel costs but it turns out that if you are in this for the long term there is a way around that.
Getting around the solar system is expensive if you are in a hurry, but if you can take your time it can be cheap.
It is not just actual planetary bodies that a spacecraft can orbit. It turns out there are also orbits around Lagrange point. Some stable, some unstable.
If you want to get from planet A to planet B cheaply and aren't in a hurry, what you can do is first put your cargo container in an orbit around an appropriate A/Sun Lagrange point, then nudge it into a carefully chosen unstable orbit.
The unstable orbit gets farther and farther away from the Lagrange point. At some point, it crosses an unstable B/Sun Lagrange orbit, with a low enough delta-V between the two that a nudge can move it from the former to the later.
It then gets closer and closer to that B/Sun Lagrange point, until you reach a point where another nudge can move it into the same orbit as B, just ahead or behind. Another nudge gets it to B.
How long this takes depends on A and B, and it is all over the place. Some combinations take a decade or two. Some take hundreds of years. Some take thousands.
This then is a plan for a long term thinking civilization to colonize their solar system (I'm going to assume that they also call their planet "Earth" and a major moon of it "Moon"). First, get yourself a serious presence in Earth orbit and Moon orbit, and maybe also on the Moon. Anything you can make in one of those places that is needed for your deep space missions is a win because you won't have to get it out of Earth's gravity well.
When you've got to the point that you can produce a steady stream of unmanned space cargo containers loaded with non-perishable items in Earth orbit or Moon orbit, you can start moving them to appropriate Lagrange points, and nudging them into appropriate unstable orbits for the places you want to colonize.
It will take a long time, but when you have a good number of shipments accumulated at a place you want to colonize, you then send your colonists using the fast, expensive route. Note that your colonists only need to take enough supplies for the trip itself. (And they don't need to take return fuel if not everyone is going to stay, as that can be included in the pre-sent cargo).
There is a saying that once you reach the orbit (here, on Earth), you are halfway to anywhere.
Lifting objects from Earth's gravity well is expensive. There would be a better case for building extensive industrial base on the Moon, with its 0.16g gravity, and supplying all the distant bases from there.
You can, for example, plausibly build a space elevator on the Moon [1] with contemporary materials (even Kevlar would suffice), thus lowering the price tag enormously.
Sure it does — you shuttle humans up to LEO at the current SpaceX Dragon cost, and instead of docking to the ISS they dock to the full-size replica of the Enterprise that an eccentric billionaire 3D printed out of Moon rock and filled with space-grown food, plants, and spandex costumes.
Is robotics (longterm) a solution here, and if so, what level of autonomy do we need?
Latency between Earth and the Moon is just enough to make realtime command a bit too rough to use I'd imagine, so I imagine we'd need at least low level autonomous tasks of "move resources from landing pad to storage" and "prepare build site" with enough intelligence to detect when these tasks hit an exception.
On top of that, I suspect we'd need enough robotic automation to be able to build, maintain and run whatever the thing is. That probably means several specialized robots (packing dirt for a foundation, deploying construction pieces, a crane) as well as some general robots for when things do go off script (haul away a broken robot, right a fallen pylon, remove debris).
Does this feel like something achievable in the next decade or two? Are there large pieces we're missing?
Except for abrasive soil, all the challenges exist on the orbit as well. And various satellites seem to cope.
If attrition of the robots turns out to be a factor, it could still be solved like this: expect that an average robot can survive 6 months on the lunar surface. So send twenty of them to the remote base, build a cave for the reserve robots and "burn" through the reserve slowly. Every 4-5 years, send a human crew to replace or repair the dead robots.
So let's assume Musk nails it and can do this for $10M. Instead of my 20, imagine 200 100-ton landings of cargo on the moon, say over the period of ten years.
Instead of everybody sitting on Earth, trying to design-session-out the perfect lunar base, why not just keep regularly-delivering supplies, then learn how to build a lunar base while on the moon, figuring it out as you go? After all, just like SpaceX, we're not trying to build a lunar base. We're trying to build a factory for constructing lunar bases, eventually hundreds of them. Solving the modular/generic problem is what we want to do, not build another Space Shuttle.
Perhaps I'm wrong, but it seems like most of the people here, indeed most of the aerospace industry, naturally prefer these big, lumbering, paperwork-heavy, long-lasting bureaucratic programs. But without enough regularly-arriving supplies, why try to solve something up-front, all-at-once, and perhaps years or decades ahead of time when you can just figure out the bare minimum of things you need just as you need them?
But like I said, I'm probably missing something. I've been saying for 20+ years that our real problem is cost-to-LEO. Now that we're just barely beginning to address that, the next problem very well may likely be changing the way we think of large space-based programs. That could very well end up being a bigger problem than cost over the long run.
ADD: Seems to me that the Starship is a solution to delivering humans to space. We need reusable heat shields, booster packs, and payload capsules, along with an Earth-based mass-driver, to truly drive down cargo rates another 100x. At that point we'll begin seriously talking about becoming a space-faring species.
> So let's assume Musk nails it and can do this for $10M. Instead of my 20, imagine 200 100-ton landings of cargo on the moon, say over the period of ten years.
That cost is predicated on rapid relaunch, with multiple launches /per-day/. It wouldn't be ten years, more like two to four :)
Fully fuel requires at least 8 tanker launches IIRC. Fully fueled Starship weighs 1,200 tons, 1,100 tons of fuel over 8 launches is nearly 150 tons per launch.
But seriously, the "dark side" of the moon is the side we can never see from earth. It isn't literally dark so much as just unseen. Consider similar usages like "dark energy" or "a shot in the dark".
Isn't it true that the far side is darker? The near side will be illuminated either by the sun directly or by light bouncing off the earth. The far side is also, of course, intermittently illuminated by the sun. But when it isn't, wouldn't it be much darker?
Almost all the lunar maria, which are very dark, are on the near side. So, in those places, you get some extra light from the Earth, but less of it is going to be reflected from the ground towards your eyes.
The far side is mostly highlands, with albedo twice as high.
Are you putting them on the dark side to reduce light pollution from Earth? It's going to complicate communication since you'll need a relay to bounce signals off of when talking with it.
I think it would be a nice idea to have several more normal telescopes on the moon with an internet site that would allow you to rent time and operate them remotely somehow. And maybe one or two really big visible light ones.
This would theoretically provide a superior level of clarity versus ground telescopes. And it would allow for viewing of the earth.
It might still be, creating a disk of 100m in diameter on the moon would need all the help you can get. There aren't exactly alot of bulldozers on the moon.
"There is some urgency in establishing a lunar far-side radio-quiet reserve before we get the burgeoning problem we have in Earth orbit with optical interference from communications satellites. We are already concerned about the Chinese communications satellites—so this needs to be a global consensus now!" -- Dr. Pete Worden, the Chairman Breakthrough Prize Foundation and the former director of NASA's Ames Research Center
> To study the first stars, it would stare at the same patch of sky continuously, to collect as much light from them as possible
I hate to be the one to spoil the party, but the moon rotates. The main problem with a rotating liquid mirror is that you don't get to choose the axis of the parabola, and that axis rotates as the moon orbits the Earth.
You may be able to get a decent view of stars drifting through the view, and with enough orbits you could build up a decent picture, but that's different from staring "at the same patch of sky continuously".
As others have pointed out, this was considered. Here is the relevant excerpt from the paper:
> To avoid an articulating mount, the telescope would be placed at the lunar pole, constantly pointing at the
zenith. [...] The limit on exposure time is then given by the precession of the moon, and is of the order of several days. This can only be extended by the addition of some active tracking facility, for example a moving prime focus platform.
My biggest problem is with the outdated concept of optics used in telescopes today. There is usually a large mirror and lenses which should be redundant.
A NN trained on the physics simulation of a wobbling droplet of e.g. mercury should be able to use this "predictable, deterministic" partial mirror, to glimps everything needed to see. If a ferro-fluid with electromagnetic actuators is used-the shape of the mirror could be even modified by the observer NN in realtime, to sharpen, or block parts of the mirror.
If this would be acceptable to the astronomic community - we could mass produce Hubbles.
Would it? With no wind, the sand mostly stays on the ground. When it does get kicked up by something, it goes right back down since there's no atmosphere.
US astronauts found that static charge made the regolith stick to everything that came near it. Basically anything that moved across the surface got quickly coated. And because there is no weathering on the moon, the particles could be extremely small and sharp, which made it difficult to exclude or expel them. Apollo suits at the Smithsonian are still gray with embedded regolith. Conservators try to minimize flexing as the embedded sharp particles chew up the fabric fibers over time.
I've thought for a long time that this would be a great science mission for a manned lunar landing or a series of them. This is probably something too complex and large to robotically assemble on the Moon, and a human mission could also use in-situ lunar resources (e.g. lunar concrete) to help build such a thing. You could build a massive telescope up there that would be able to outperform anything we currently have by many factors.
Even better would be an array of them precisely positioned and bound together.
I wonder how big you'd have to go to actually see exoplanets? Wow.
A common question seems to be: why not put such a telescope in Earth orbit? This is a spinning, liquid mirror telescope that uses centripetal acceleration to turn a pool of liquid mercury into a parabolic mirror. Orbit does not provide the gravity to continuously 'cast' the mirror into a parabola. The parabolic shape is necessary to focus light to a point. A few prototypes have been carried out on Earth, notably one by the University of British Columbia. The main advantage is that a 100m (one hundred meters!) aperture with near optical perfection can be transported in a compact reservoir in liquid form.
There are other ideas for large optical telescopes in space like 'painting' part of a balloon with a reflective material. The disadvantages are that these produce spherical rather than parabolic surfaces and would require complex re-imaging optics (like Arecibo). The other is that to observe optical and near-ultraviolet light the surface must be very accurate with deviations less than 15 times the wavelength of the light (so in the 20 nanometer regime). The technology has not been demonstrated for this with a space balloon, but there are plans to use this scheme for far infrared or microwaves where the surface accuracy constraints are less severe.
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[ 3.3 ms ] story [ 175 ms ] threadA stable polar orbit is easier to get to and return from the moon.
If we wanted to build something similar in space it's essentially a 5x larger James Webb Space Telescope which is having some trouble last I heard with it's folding mechanism so building one 5 times larger to fit into a faring is a big task.
I guess the big problem for that right now is that for humans to do the building, it'd have to be in low orbit, a less-than-ideal environment for a long-lived scientific instrument. (Just kibbitzing, am not a rocket scientist.)
It does need to support it's own mass through during maneuvering and pointing operations as well so it can't be completely flimsy. Also you'd want to get further from the earth to avoid all that drag from a huge mirror in LEO.
[0] Beyond periodic small orbit boosting burns
Another problem: a very large mirror is a significant target for micrometeoroids. It'd need to be made able to keep going after losing little patches.
https://www.nasa.gov/content/hubbles-mirror-flaw
I was fantasizing some form of active control, without the speed demand of in-atmosphere adaptive optics. This might be needed anyway after micrometeoroid damage.
Other issues with space based telescopes:
They need fuel + thrusters to go where you want them to be (or just to maintain their orbit!)
Heat dissipation is a big problem. Being able to use the whole moon as a thermal flywheel could help out a lot. In space you can use things like cryocoolers to regulate temps, but they cause vibrations which can be problematic if you need your telescope to remain steady. If this requires refrigeration, you can put the vibrating parts far enough away from the telescope that they don't move it. Putting the thing in a crater probably helps regulate temps too (less direct sun)
Humanity in general is better at building and maintaining things on solid ground. If you drop a bolt on the moon, you lean over and pick it up. If you drop a bolt in orbit, you have to worry about it damaging your spacecraft at the next conjunction.
The magnification of the 100M mirror make up for the lack of being able to point it anywhere at a much reduced cost than a 'traditional' space telescope.
The JWST is not exactly going smoothly, and telescopes of that size will not be powerful enough to study the era of the first stars.
>Without an independent infrastructure in place at a lunar pole, it would likely be impossible to construct and operate a large liquid-mirror telescope.
They need to find a solid that does not just sublimates when heated in the void.
The problem would be more in choosing a material that has low enough melting point so that making up for the radiative loss to keep it melted wouldn't be a big issue and at the same time vapor losses can be managed. Which is why they propose separate materials for the mirror body and its surface I guess.
Of course it should probably never point at the sun unless they want to melt their sensors.
I would like this to be the project that really drives future human presence on the lunar surface.
But the cost difference in landing anything on the moon is massive. Every kilogram of payload sent to low earth orbit takes roughly 15 Kg of fuel. To land a Kg of payload on the moon requires roughly 80 kg of fuel.
https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...
https://arxiv.org/abs/2007.02946
For the sort of telescope which they propose to use, they reference:
https://iopscience.iop.org/article/10.1086/588034
Particularly – "Astronomers grouped stars in the order they were observed, so Pop I stars are present-day stars, with Pop II stars being one generation older. Pop III stars are the hypothesized oldest stars in existence."
SpaceX is purportedly at some point going to be able to put 100 tons in LEO for around 100M. I'll roughly assume with a second launch full of fuel, a purchaser with the right gear could put close to 100 tons on the lunar surface for 200M or so, once they get the kinks out and the price down.
So why not just pre-purchase 20 of these for your favorite lunar project, such as the ULT? If they bring prices down you get a cool lunar base. If they don't, you don't pay. That much payload delivered to the moon for $4B would be an incredible bargain, and it also serves to further incentivize SpaceX.
I'm sure I have something about the economics wrong, but I don't know what. Seems to me like we should be very close to a lot of back-burner space projects getting off the drawing boards.
What don't I understand?
If I recall correctly, for the apollo program about 30% was for the launch vehicle.
If launch costs decrease by an order of magnitude, reliability of payload can be relaxed, and therefore costs of payload engineering and manufacture decrease.
There could be other knock off effect of cheaper and more frequent space launch - you can send multiple versions and see which works the best, ship prototypes back for extensive evaluation, send robots or people to fix broken things.
A lot of things are done differently if you have just a couple super expensive shots per decade & everything needs to work without external help at the first time.
SpaceX is special (or used to be special, maybe others have followed suit by now?) in that they make this information public. See here what loads, accelerations or vibrations the payload has to withstand during a launch on a Falcon 9 or Falcon Heavy launch vehicle:
https://www.spacex.com/media/Falcon_Users_Guide_082020.pdf#p...
That is what needs addressing. That level of automatisation is the hard part about space.
We don't really know how to create a self-contained ecosystem here on Earth, with everything on-hand. And the residents won't even all die if someone accidentally pokes a hole in the wall in the Antarctic prototype base.
https://en.wikipedia.org/wiki/Biosphere_2
Shocking ...
Including humans seems to have caused most of the problems there. If you actually wanted to experiment with closed biological systems in a useful way then I'd recommend doing a bunch of trials with a less cantankerous species of large omnivorous mammal, like the goat.
>including humans seem to have caused most of the problems
I chuckled a bit at your reply hvd.
The hardest, seemingly intractable problems in the world aren't engineering problems, they are human ones. If we want to level up as a species those are the ones we will need to figure out how to solve.
Because they didnt want air going in or out of the biosphere they had to figure out a way to account for the massive change in volume as the air temperature inside changes between super hot days and cold nights, otherwise you'd blow the windows out of the thing during the day.
I fully support such activities.
At first, that seems completely impractical due to the enormous fuel costs but it turns out that if you are in this for the long term there is a way around that.
Getting around the solar system is expensive if you are in a hurry, but if you can take your time it can be cheap.
It is not just actual planetary bodies that a spacecraft can orbit. It turns out there are also orbits around Lagrange point. Some stable, some unstable.
If you want to get from planet A to planet B cheaply and aren't in a hurry, what you can do is first put your cargo container in an orbit around an appropriate A/Sun Lagrange point, then nudge it into a carefully chosen unstable orbit.
The unstable orbit gets farther and farther away from the Lagrange point. At some point, it crosses an unstable B/Sun Lagrange orbit, with a low enough delta-V between the two that a nudge can move it from the former to the later.
It then gets closer and closer to that B/Sun Lagrange point, until you reach a point where another nudge can move it into the same orbit as B, just ahead or behind. Another nudge gets it to B.
How long this takes depends on A and B, and it is all over the place. Some combinations take a decade or two. Some take hundreds of years. Some take thousands.
This then is a plan for a long term thinking civilization to colonize their solar system (I'm going to assume that they also call their planet "Earth" and a major moon of it "Moon"). First, get yourself a serious presence in Earth orbit and Moon orbit, and maybe also on the Moon. Anything you can make in one of those places that is needed for your deep space missions is a win because you won't have to get it out of Earth's gravity well.
When you've got to the point that you can produce a steady stream of unmanned space cargo containers loaded with non-perishable items in Earth orbit or Moon orbit, you can start moving them to appropriate Lagrange points, and nudging them into appropriate unstable orbits for the places you want to colonize.
It will take a long time, but when you have a good number of shipments accumulated at a place you want to colonize, you then send your colonists using the fast, expensive route. Note that your colonists only need to take enough supplies for the trip itself. (And they don't need to take return fuel if not everyone is going to stay, as that can be included in the pre-sent cargo).
Here are a few articles on this [1][2][3].
[1] http://www.gg.caltech.edu/~mwl/publications/papers/IPSAndOri...
[2] https://en.wikipedia.org/wiki/Interplanetary_Transport_Netwo...
[3] http://www.dept.aoe.vt.edu/~sdross/papers/AmericanScientist2...
Lifting objects from Earth's gravity well is expensive. There would be a better case for building extensive industrial base on the Moon, with its 0.16g gravity, and supplying all the distant bases from there.
You can, for example, plausibly build a space elevator on the Moon [1] with contemporary materials (even Kevlar would suffice), thus lowering the price tag enormously.
[1] https://en.wikipedia.org/wiki/Lunar_space_elevator
Latency between Earth and the Moon is just enough to make realtime command a bit too rough to use I'd imagine, so I imagine we'd need at least low level autonomous tasks of "move resources from landing pad to storage" and "prepare build site" with enough intelligence to detect when these tasks hit an exception.
On top of that, I suspect we'd need enough robotic automation to be able to build, maintain and run whatever the thing is. That probably means several specialized robots (packing dirt for a foundation, deploying construction pieces, a crane) as well as some general robots for when things do go off script (haul away a broken robot, right a fallen pylon, remove debris).
Does this feel like something achievable in the next decade or two? Are there large pieces we're missing?
If attrition of the robots turns out to be a factor, it could still be solved like this: expect that an average robot can survive 6 months on the lunar surface. So send twenty of them to the remote base, build a cave for the reserve robots and "burn" through the reserve slowly. Every 4-5 years, send a human crew to replace or repair the dead robots.
Can be done, the main question is the price tag.
Do you have to put money down like with Tesla Full Self Driving?
https://twitter.com/elonmusk/status/1328770804222468097
(I've heard some ad hominem attacks that this will never happen, but haven't seen any actual evidence that it's impossible.)
So let's assume Musk nails it and can do this for $10M. Instead of my 20, imagine 200 100-ton landings of cargo on the moon, say over the period of ten years.
Instead of everybody sitting on Earth, trying to design-session-out the perfect lunar base, why not just keep regularly-delivering supplies, then learn how to build a lunar base while on the moon, figuring it out as you go? After all, just like SpaceX, we're not trying to build a lunar base. We're trying to build a factory for constructing lunar bases, eventually hundreds of them. Solving the modular/generic problem is what we want to do, not build another Space Shuttle.
Perhaps I'm wrong, but it seems like most of the people here, indeed most of the aerospace industry, naturally prefer these big, lumbering, paperwork-heavy, long-lasting bureaucratic programs. But without enough regularly-arriving supplies, why try to solve something up-front, all-at-once, and perhaps years or decades ahead of time when you can just figure out the bare minimum of things you need just as you need them?
But like I said, I'm probably missing something. I've been saying for 20+ years that our real problem is cost-to-LEO. Now that we're just barely beginning to address that, the next problem very well may likely be changing the way we think of large space-based programs. That could very well end up being a bigger problem than cost over the long run.
ADD: Seems to me that the Starship is a solution to delivering humans to space. We need reusable heat shields, booster packs, and payload capsules, along with an Earth-based mass-driver, to truly drive down cargo rates another 100x. At that point we'll begin seriously talking about becoming a space-faring species.
That cost is predicated on rapid relaunch, with multiple launches /per-day/. It wouldn't be ten years, more like two to four :)
But seriously, the "dark side" of the moon is the side we can never see from earth. It isn't literally dark so much as just unseen. Consider similar usages like "dark energy" or "a shot in the dark".
Almost all the lunar maria, which are very dark, are on the near side. So, in those places, you get some extra light from the Earth, but less of it is going to be reflected from the ground towards your eyes.
The far side is mostly highlands, with albedo twice as high.
This would theoretically provide a superior level of clarity versus ground telescopes. And it would allow for viewing of the earth.
Quite a small one, but first of its kind. :)
1. NASA STMD study with robotic assembly: https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...
2. Article on the basics + decadal survey paper: https://phys.org/news/2020-10-moon-seti.html
3. Recent lecture on the "FARSIDE" mission concept at Caltech: https://kiss.caltech.edu/lectures/2020_Hallinan.html
"There is some urgency in establishing a lunar far-side radio-quiet reserve before we get the burgeoning problem we have in Earth orbit with optical interference from communications satellites. We are already concerned about the Chinese communications satellites—so this needs to be a global consensus now!" -- Dr. Pete Worden, the Chairman Breakthrough Prize Foundation and the former director of NASA's Ames Research Center
I hate to be the one to spoil the party, but the moon rotates. The main problem with a rotating liquid mirror is that you don't get to choose the axis of the parabola, and that axis rotates as the moon orbits the Earth.
You may be able to get a decent view of stars drifting through the view, and with enough orbits you could build up a decent picture, but that's different from staring "at the same patch of sky continuously".
> To avoid an articulating mount, the telescope would be placed at the lunar pole, constantly pointing at the zenith. [...] The limit on exposure time is then given by the precession of the moon, and is of the order of several days. This can only be extended by the addition of some active tracking facility, for example a moving prime focus platform.
A NN trained on the physics simulation of a wobbling droplet of e.g. mercury should be able to use this "predictable, deterministic" partial mirror, to glimps everything needed to see. If a ferro-fluid with electromagnetic actuators is used-the shape of the mirror could be even modified by the observer NN in realtime, to sharpen, or block parts of the mirror.
If this would be acceptable to the astronomic community - we could mass produce Hubbles.
Presumably the stuff required to move stuff to make the scope will disturb at least some sand
Ergo, ultra fine dust will fall to the moon's surface at the same rate as a boulder.
Dust will stick with static electricity however much better on the moon - so your point has an even better justification.
https://www.businessinsider.com/moon-dust-is-toxic-2012-7
(I’m not a materials scientist, this is a question not a suggestion)
Even better would be an array of them precisely positioned and bound together.
I wonder how big you'd have to go to actually see exoplanets? Wow.
There are other ideas for large optical telescopes in space like 'painting' part of a balloon with a reflective material. The disadvantages are that these produce spherical rather than parabolic surfaces and would require complex re-imaging optics (like Arecibo). The other is that to observe optical and near-ultraviolet light the surface must be very accurate with deviations less than 15 times the wavelength of the light (so in the 20 nanometer regime). The technology has not been demonstrated for this with a space balloon, but there are plans to use this scheme for far infrared or microwaves where the surface accuracy constraints are less severe.