I was thinking about the issues raised on another thread about the lack of elements on the moon that are required to grow food. Carbon, nitrogen, and some others will have to be imported on a large scale in order to create the farms that will be essential to colonizing the moon.

While I was thinking about this I remembered the most recent episode of Astronomy Cast - Space Junk, and wondered why more care isn't made to simply create a garbage dump in space. We waste so much money and energy getting the stuff up there in the first place, why not leave it there? Eventually we can send all that junk off to the moon where it could be used. All the waste from human missions that is carefully collected and brought home should be left in orbit. All the dead satellites, rocket boosters, and anything else could be collected into a mass in orbit around the Earth waiting for a day when we can strap some rockets onto the mess and send it to the moon.

I had a few ideas about how this could be done but I'm not sure any of them are very practical. Obviously some kind of space station would be required, something like a barge that could steer the junk around when needed, and when new stuff comes in, such as a left over booster, a robot or human could go out and weld the thing to the growing pile. All the stuff that can decompose, such as waste from manned missions in orbit, could be collected into some kind of fermentation chamber and used to produce methane to power the rockets that will move the mess. (I doubt enough methane would be produced, but it's a thought).

I hope to get a good discussion going on the practicalities of this idea. If we focused on sending reusable materials up, with a mind toward eventually using the stuff on the moon, we could get quite a bit of usable mass up there without wasting a ton of extra money.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast

I can think of two problems for the practicality.

One is the cost and energy involved. Ferrying space junk to some location would require an enormous amount of energy. It would seem more efficient to simply launch a spaceship with lots of carbon on board, if that's what you need.

A second consideration: isn't space junk mostly metal, which is not needed? I wonder how much carbon and nitrogen there is among the space junk. Sure, there's plastic, but is there really enough to make it efficient?

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As above, so below

But that's the point. We could intentionally use materials that would be useful. Why not make greater use of carbon fiber composites or plastics high in carbon? I'm sure with a little imagination almost everything that is sent up could be reusable.

As for the junk ferrying problem, as mentioned in the show, NASA is already planning on building robots and such to help remove debris from orbit and fetch satellites for repair. There's too much stuff in orbit now, the junk needs to be cleaned up. A space dump would make sense.

Oh, and just because metals are available on the moon doesn't mean they'll be easier to mine, refine, and forge than it would be to recycle materials that have already been made.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast

Space Junk:

There is no easy answer on space junk, since all of the items would have to be collected somehow. The majority of space junk lacks and propulsion system that would allow the object to reduce it's orbital velocity so that it would fall and burn up in a controlled reentry into the atmosphere.

One recent suggestion almost made sense, a giant stickyball type of spacecraft that would sweep entire areas of junk and then deorbit. But the drawback is that the big stickyball would also sweep up active satellites that were still in use.

Moon Resources:

As for resources on the Moon, any resources missing would have to be delivered. If there is ice frozen in the crater shadows at the poles, it would make human settlement much easier. If there is no water there, it has to be brought from Earth or manufactured on site with atomic oxygen and hydrogen.

It may take less energy to mine the asteriods for material than to lift it out of the Earth's gravity well. If we could capture a small comet, that would provide a lot of water, too. We could attach an ion propulsion module on it and crash it on the moon.

A quick search yields cost estimates for launching things into space on the shuttle starting around $10000 per pound and rising from there. Obviously there are cheaper ways to launch raw materials, such as on the top of unmanned rockets, but even if it was a quarter of that price it will still be extremely expensive.

We have a dual problem of too much junk in orbit and a need for materials on the moon, it seems to make sense to try to both collect the existing junk and to carefully plan what other junk we'll send so that it is more useful on the moon. As mentioned before, I wonder if carbon composite materials could be used in place of other materials. I also wonder if many of the materials used for satellites or disposable spacecraft parts could be made from useful alternatives that contain high amounts of carbon, nitrogen or other elements necessary on the moon.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast

And how much technology (masswise) would be needed to convert that resource to a reasonable form?
While I do agree that re-usability should be considered, it just doesn't sound like it's all that practicle.
Planning or studying? There's a big difference, and the context is important. Since I haven't seen it, I'd like a bit more information before I dispute this.
Deorbiting space junk is much simpler than moving it. No matter what method you use, you still need to rendezvous. That's going to be expensive.
It takes a relatively small delta-v to bring an orbiting object into a low enough orbit for re-entry. It takes a huge delta-v to send it off to the moon. So now that solution has just added a whole lot of fuel to to the equation.

Before we even talk about converting or recycling material to a useable form, what about actual construction using that material. At this point it's easier to construct it here and send it.

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That's a valid question, and obviously some sort of facility would be required on the surface of the moon to do something with the materials. I haven't thought my way through all this stuff so I have few answers and probably most of those are bad.

The point of the topic is not whether or not the methods I suggest are feasible, but whether or not creating a space dump could be a practical alternative to two problems.

I'd invite anyone with ideas to suggest possible methods to process materials on the moon. For starters you have lots of mostly raw sunlight to work with; would a solar furnace work? That doesn't seem like a huge technological feat to me. Is it?

Excellent point, and you are right, the distinction is an important one and I must confess I do not know, so let's go with studying until we learn otherwise.

Yes, deorbiting junk is probably the easiest solution. But it seems to be a waste.

As for the efforts involved in trajectory changes, wouldn't you have to do the same with anything you send to the moon? This argument seems to only apply if I simply asked "send junk to the moon or let it burn up in Earth's atmosphere?".


That may be true to start with, but once facilities are in place, scrap material could be processed. I'm not suggesting the first lunar citizens live in a spent rocket booster and sit around with hammers beating on scrap metal all day. The point is to think ahead. Why waste material when it's already been put into orbit. Send it to the moon. It will probably be useful eventually.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast

I'm not quite sure what you are referring to, but I was responding to the existing stuff you mentioned in Earth orbit, and anything in a similar situation that would normally remain in Earth orbit.

For discarded items that are already headed for the moon. I would agree that deorbiting them to a common area on the moon makes sense. Even if theres no (near term) future practical use for it, at least it wouldn't be cluttering up many areas of the moon.

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Numbers are not case sensitive. (me)

Have you seen how materials are recycled on good old terrafirma ? The amount of equipment needed would be way beyond what anyone could afford.

Lets take a wild stab at some numbers.

1. Lunar scrap truck with hoist. 3 tons
2. Lunar shredder. 5 tons
3. Lunar smelter. 10 tons

It’s was stated the cost to LEO is $10,000/lb. So lets “guess” $50,000/lb to the lunar surface. That’s 18 tons (conservative) at $50,000/lb which equals 1.8 billion dollars to make ingots of titanium. Which on Earth sell for under $10/lb.

That doesn’t count the numerous other things required to run all of that stuff.
And don’t forget the Lunar scrap workers union!

The whole idea is the closest thing to “Ain’t NEVER EVER EVER gonna happen” I can think of.
Even the most eco friendly space nut would take the same money and dump a few more boosters in orbit for a few more exploration missions. It’s easier to avoid the junk than to do something about it. Face it the worst thing about polluting space is the impact hazard.

You don’t get tumors from space junk!

To build a colony on the moon you will need a lot of heavy equipment. It makes sense to me that sending equipment that would allow you to build things from raw materials on the moon would be the most economical way of handling things. But until serious mining operations were underway it would probably make sense to recycle everything possible.

On the moon, recycling would have to be an art form. Things we take for granted here will not be up there unless we boost them off of Earth and fly them there. A small foundry with refining capabilities would probably be much cheaper than replacing every used thing that breaks.

Perhaps it would be practical to discuss what is necessary for a moon base first and then see what need there might be for space junk. But I would think that with the extreme lack of an element like carbon which is essential for life that any source of it would be welcome.

On the other hand, perhaps grabbing asteroids would be more practical large scale sources of needed elements, but as far as I know we don't have the capability of going to the asteroid belt to start diverting material toward the moon. I have no doubt we could do it if we needed to, but how much would that effort cost? Would it be worth it?

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast

When you send things to the moon, do you send them on a straight line from Earth or do you orbit the planet a few times before flinging off toward the moon?

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast

It is essentially a figure eight. You send the craft in a highly elliptical orbit. If the moon were not there, that ellipse would be over 3/4 of the way there (SWAG value, probably not close, but enough to visualize).

It is far enough that the moon's gravity is stronger than Earths gravity. Therefore, the ellipse is further elongated from that effect, and the stronger gravity eventually takes over and brings it toward the moon (again into a highly elliptical orbit).

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Numbers are not case sensitive. (me)