Move the ISS to the Moon!

[Travis]

As a purely intellectual exercise, what would it take to move the International Space Station into a Lunar orbit? Could this be done? Would the station be able to withstand the rigors of accelerating to an escape velocity and then decelerating to enter Lunar orbit? Would there be adequate shielding to protect inhabitants once there? Could it be used as a refueling and refitting waystation for some craft like the DC-X to make repeated trips to the Lunar Surface? Is there any merit to the idea from either a scientific or economic standpoint?

In case you're wondering I was talking to a friend about possible unorthodox means of exploring the Moon should Obama and Congress decided to gut the Constellation Program and this just came up.

 

[R.Mackey]

As a purely intellectual exercise, what would it take to move the International Space Station into a Lunar orbit? Could this be done?

No. For control reasons if nothing else.

Would the station be able to withstand the rigors of accelerating to an escape velocity and then decelerating to enter Lunar orbit?

There are some remarkably low thrust orbital designs out there these days. It would take a long time to get there, but I'm sure a transfer orbit could be found that would preserve the structure.

Getting the propulsion up there to move it, however, would be no picnic. Delta-V from LEO to LTO is about 4 km/s, times 400 tons station mass, is a heck of a lot of total impulse. Electric would be the way to do it, but even so you're talking about a lot of upmass to make it move.

Would there be adequate shielding to protect inhabitants once there?

No. Astronauts would be vulnerable to solar weather, just like they were in the Apollo program. However, if we're shipping up many many tons of thruster, we could also ship a radiation shelter, I suppose.

Could it be used as a refueling and refitting waystation for some craft like the DC-X to make repeated trips to the Lunar Surface? Is there any merit to the idea from either a scientific or economic standpoint?

The ISS is not currently equipped to handle fuels. In general, the idea is feasible, though the current architecture would probably be cost-prohibitive to retrofit under any scenario.

In case you're wondering I was talking to a friend about possible unorthodox means of exploring the Moon should Obama and Congress decided to gut the Constellation Program and this just came up.

I assume you've read the Augustine Commission Report? It treats exactly this kind of question in detail, albeit one with its own strong opinions and biases.

The ISS is and has been useful in its own right, among other things to teach us how to build and manage large structures in space. It's an enormous problem all its own. If you've ever let your garage get cluttered or had a hard time editing your software registry, you can probably appreciate how stupendously difficult this kind of enterprise really is. However, for lunar expeditions, it isn't clear how valuable ISS would be -- that's not what it was designed for. It certainly gives us some possible abort / lifeboat modes in case of off-nominal crew launches from Earthside, but once outside LEO it's just another point of light.

Disclaimer, all opinions are mine alone and do not represent NASA or any other agency in any way; also it's all off the top of my head.

 

[shadron]

I assume you've read the Augustine Commission Report? It treats exactly this kind of question in detail, albeit one with its own strong opinions and biases.

I'll add my support to Mackey's opinions; you'd probably have to reinforce it to accelerate it enough to get there within ten years, and keeping it on course would be a real hummer. Cheaper to build something there, or build it in Leo with the boost being part of the design from the start.

Gees, Norm's looking old. I knew him (from afar, for sure) when I was working on Viking and he was a department manager. Then again, I don't suppose I look very young myself these days.

 

[Aitch]

There are some remarkably low thrust orbital designs out there these days. It would take a long time to get there, but I'm sure a transfer orbit could be found that would preserve the structure.

Why not build a second ISS in lunar orbit? Send the parts, unmanned, in advance. Then send a team of builders.

That way, you'd have two stopping off points on the way to the moon. You'd probably have to modify the current ISS. And extend it, but...

No. Astronauts would be vulnerable to solar weather, just like they were in the Apollo program. However, if we're shipping up many many tons of thruster, we could also ship a radiation shelter, I suppose.

Would it be beyond the wit of man to put it in an orbit that always put it behind the Moon, wrt the Sun? Or would such an orbit be unstable?

 

[Travis]

Thanks for the link Mackey. I haven't read the report, only heard of it.

I'll add my support to Mackey's opinions; you'd probably have to reinforce it to accelerate it enough to get there within ten years, and keeping it on course would be a real hummer. Cheaper to build something there, or build it in Leo with the boost being part of the design from the start.

Which is kinda what we ended up assuming as well. So what merit might there be to running Moon missions from a space station in lunar orbit as opposed to building a surface base?

 

[BenBurch]

I seriously don't think people can live in space outside of the earth's magnetic field for the long term. Not unless we come up with some nearly miraculous means to do radiation shielding. ON the moon, or rather IN the moon is feasible - enough lunar material on top of you and the radiation isn't a concern. But you are not going to lift that much stuff into orbit to make a sufficiently-thick shield.

 

[R.Mackey]

Why not build a second ISS in lunar orbit? Send the parts, unmanned, in advance. Then send a team of builders.

Well, there's two reasons. One is that the current ISS required a projected 35 Shuttle flights to assemble and staff, plus numerous flights of Soyuz, Progress, etc. to staff and resupply. We currently have no way to do this above LEO, not to move the pieces there, not to assemble them, not to rotate crews or provide escape options. The architecture is vastly more complicated outside of LEO, and vastly more expensive.

The other is that the ISS design is not nearly the right one for a Lunar resupply hub, or to direct Lunar surface operations. In fact, Delta-V from Lunar surface to orbit is low enough that we may be better served doing all of those ops on the surface. Particularly if ISRU (In-Situ Resource Utilization, viz. making fuel and air from Lunar materials) works out. Given the recent discovery of water by the LCROSS team, ISRU is looking better.

Would it be beyond the wit of man to put it in an orbit that always put it behind the Moon, wrt the Sun? Or would such an orbit be unstable?

Such an orbit would be unstable. There are Lagrange points in the Earth-Sun and Earth-Moon systems, notably L2 which is opposite the primary body, and this one is stable. But there are no stable Sun-Moon Lagrange points. The orbit you would need is a following orbit, basically balanced right at the turnover point between Earth and Moon, and this is by definition unstable. It is also too far out from Moon to provide any meaningful shielding.

Not to mention, if one is shielded from solar weather, one is shielded from solar energy as well. Going to be rather cold and dark on that station.

There are plans to use the Sun-Earth L2 point for orbiting observatories, where cold and dark are virtues, but there won't be anyone on board.

 

[Wolrab]

Wouldn't it be better to build on/in the Moon, then (if available) use lunar resources to build a lunar orbiting station? The fuel needed to go from the lunar surface to orbit has got to be orders of magnitude less than from Earth to lunar orbit.

Would a hollowed out, captured asteroid (when feasible) offer better shielding than anything we could send up to be assembled?

 

[dasmiller]

Would a hollowed out, captured asteroid (when feasible) offer better shielding than anything we could send up to be assembled?

The capture part is pretty tricky. If I have a little time, I'll see if I can find a suitable asteroid, but offhand I think we'll be lucky to find one that requires only a few km/s delta-V. If you're using chemical propulsion, it's hard to have a specific impulse (Isp) much better than 400; with an Isp of 400 and 3 km/s, your fuel would weigh as much as the asteroid. You'd be better off simply using the tanks of fuel as shielding and letting the asteroid sail on past.

Electric propulsion is far more efficient, of course, but the thrust levels are very, very low (think high-powered flashlight) and, without running the numbers, I suspect it's decades (and maybe centuries) to capture a decent-sized rock.

If you can run some sort of hybrid, getting the reaction mass from the asteroid itself, using electric power to throw the mass off at some modest Isp (low Isp allows higher thrust), then the numbers are probably less awful but still not good. I think Pournelle did an article about this, maybe in the early 80s.

 

[Toke]

Hollowing out an asteroid sounds cool, it just seems so much more in line with current stone quarry technologies to turn it into rubble and use bags of it for radiation shielding on a spaceship/station skeleton.

 

[BenBurch]

Hollowing out an asteroid sounds cool, it just seems so much more in line with current stone quarry technologies to turn it into rubble and use bags of it for radiation shielding on a spaceship/station skeleton.

Most of them can be expected to be rubble anyway.

 

[geni]

the capture part is pretty tricky. If i have a little time, i'll see if i can find a suitable asteroid, but offhand i think we'll be lucky to find one that requires only a few km/s delta-v.

2002 aa₂₉?

 

[dasmiller]

Hollowing out an asteroid sounds cool, it just seems so much more in line with current stone quarry technologies to turn it into rubble and use bags of it for radiation shielding on a spaceship/station skeleton.

If we can live with the asteroid in whatever orbit it's already in, some of the problems get much easier. Of course, some get harder.

 

[dasmiller]

2002 aa29?

The quick back-of-the-envelope (which is getting pretty covered with scribbles) gives it a little over 3 km/s relative to Earth, so if we want to keep it in the Earth-Moon vicinity, that's what we'll have to apply.

I thought about doing a clever slingshot using the moon, but even if that works, I don't think we can get the required delta-v under 2.5 km/s.

Someone should check my math . . .

 

[Travis]

Might we one day preferentially put orbiting observatories that will require multiple servicing missions in lunar orbit instead in order to take advantage of the lower delta-v required to get from the lunar surface to the platform? Granted we would need a pretty sophisticated lunar surface presence to do so.

 

[geni]

Might we one day preferentially put orbiting observatories that will require multiple servicing missions in lunar orbit instead in order to take advantage of the lower delta-v required to get from the lunar surface to the platform? Granted we would need a pretty sophisticated lunar surface presence to do so.

No. If you have to service the things you might as well put them on the moon. otherwise you go for L2.

 

[BenBurch]

No. If you have to service the things you might as well put them on the moon. otherwise you go for L2.

Being on the moon makes some problems of pointing much easier for a telescope.

 

[shadron]

The L1, L2 and L3 Lagrangian points are stable in all directions except along the line connecting them to their primary bodies. In general, if something at any of these points moves away from the point, forces will act to recenter it unless it's movement is directly toward or away from the nearest primary body. There are, however, stable orbits close around these points that require little station keeping. Other bodies perturbance, however, might have to be countered; mainly the influence of the sun in an earth-moon L point.

The L4 and L5 points are stable, and the kidney bean shaped orbits around thise points are good.

The wiki article on the Lagrangian Point^WPs is very good.

 

[JJM]

As a purely intellectual exercise, what would it take to move the International Space Station into a Lunar orbit? ...

Since the ISS is a waste of time and money (wherever it is), your "intellectual exercise" begets the question of why not pitch it into the Pacific Ocean, or somewhat more safely, into deep space. Anywhere else you send it will just continue to waste more time and money that would be more productive in just about any field of research.

If you bring home the people and make it robotic, you might be able to justify the expense- the people on the ISS aren't doing anything that robots don't need to do- except, repairing the toilet.

 

[arthwollipot]

What a depressingly short-sighted perspective.