Asteroid Missions May Replace Lunar Base Plans

An anonymous reader alerts us to a story about efforts to modify the United States' space exploration plans to focus on asteroid missions rather than a lunar base. Scientists, astronauts, and former NASA division directors will be meeting next month to develop an alternative to the Bush administration's Vision for Space Exploration. We have previously discussed the possibility of a manned asteroid mission. Quoting: "Numerous planetary managers told Aviation Week & Space Technology they now fear a manned Moon base and even shorter sorties to the Moon will bog down the space program for decades and inhibit, rather than facilitate, manned Mars operations--the ultimate goal of both the Bush and alternative visions. The first lunar sortie would be flown by about 2020 under the Bush plan. If alternative-vision planners have their way, the mission could instead be flown to an asteroid in about 2025."

A great idea

[Phil Karn]

If true, this is very good news. Asteroids, the smaller and more numerous ones being undifferentiated bodies, have considerably more scientific value than the moon. It's actually much easier to rendezvous with and return from many asteroids than to land softly on the moon and return. The moon is relatively large, with a big gravity well, and without an atmosphere, aerobraking is impossible. Landing from lunar orbit and takeoff to orbit each require delta Vs greater than 2000 m/sec. Entering and leaving lunar orbit takes even more. Asteroids require earth escape, but that is only slightly more than reaching the moon's high altitude (400,000 km). The velocity change required to rendezvous with the asteroid could be minimized by careful choice of asteroid and launch window.

Asteroids would take much more time to reach, and a mission could not be quickly aborted in an emergency. The communications lag would also be significant; real time conversations would be impossible and communications might even be blocked entirely by solar conjunction for a few days at a time. These are challenges for human space flight, but not insurmountable ones.

Good!

[bug]

Good, I hope that they succeed in changing that strategy. For any colony to actually be useful and self-sustaining, there has to be some hope of an economic return on investment. The driest deserts and coldest tundras here on Earth are like tropical paradises compared with anything outside our planet, whether that's the moon, Mars, or a space station floating around the asteroid belts. Any space colony would be heavily dependent upon imports for survival (e.g., food, clothing, natural resources, manufactured goods, etc.). That will require a roughly equal amount of exports to balance trade, probably in the forms of valuable minerals and manufactured goods that are best made in microgravity environments. That becomes rather difficult to accomplish if you're stuck in a gravity well like a planet or relatively large moon, because lifting those items back out would be prohibitively expensive. We need to stop obsessing over planets and moons, just because we happen to be bipedal and live on a planet now. Asteroids are the way to go.

Re:A little sad

[damburger]

A robot is not a scientist. The result of each experiment informs scientists how to construct the next experiment. This is easy if they live on the moon, it can take a decade if they don't.

Re:A great idea

[luzr]

Well, if you want to see human settlements off this planet, you definitely should be happy about this direction. The Moon is the most stupid place to settle. The real settlements are much better on orbit and asteroids are much better way how to obtain resources to build them. The idea that we should be living on Moon or Mars is the most stupid one. Why, once we leave that deep gravity well, should we bound ourselves to another one? All resources we need are sun for energy and matter from asteroids. Also, if you do want to have any chance of long term settlement, Moon or Mars are bad too - too low gravity, say bye bye to bones and muscles. Which is much more easily solved on orbit again...

Case For Mars

[usul294]

In the book, "The Case for Mars" the author, also the creator of the Mars Direct Plan, argues skipping the moon all-together and go straight to Mars. This is because Mars is full of resources that could be used to make a self sustaining colony, whereas a Lunar base requires everything to come from Earth. Differences between a Lunar Base and the ISS? The Lunar base is on the Moon, and on the Moon you can do geology and astronomy particularly well; on ISS, there's not much useful science.

I'm not sure cruising to asteroids is the answer, but at least there are probably lots of interesting and diverse resources, and the missions could be made lightweight(no lander required). The geology of Asteroids is probably alot different than the Moon's because there was no volcanic past or differentiation. But my opinion is, cut to the chase, go to Mars, its the most interesting thing out there.

Re:A great idea

[jc42]

In contrast, a moderate sized asteroid has almost no gravity, but can be hollowed out, filled with air, and spun to provide the illusion of gravity relatively easily.

Actually, that's a rather poor engineering approach. Few if any asteroids are likely to have the tensile strength to be reliable when spun up to the 1/2 g or so that you'd want. Once you were settled down, suddenly the whole thing would bust up and go flying off in all directions. Actually, you probably wouldn't get a chance to settle down; filling it with air would probably produce a catastrophic failure before you even moved in.

The practical approach would be to mine an asteroid for raw materials, and use them to construct the sort of artificial "habitat" that sci-fi writers have been describing for decades. They'd probably be similar in size and shape to a lot of asteroids, but they'd be structurally sound.

Actually, some writers have suggested a sort of compromise: hollow out an asteroid, construct a structurally-sound habitat in the interior, and leave a few meters of rock as shielding from cosmic rays, incoming meteoroids, etc. But this is really just the same. The asteroid would contribute nothing to the structure except shielding. You could do the same by constructing the habitat, and then bolting on a thick layer of the leftover slag from the mining operation. The result would look like an asteroid, but wouldn't be one in any meaningful sense.

But you don't want to just hollow out an asteroid and start it spinning. You want to live in a habitat with a strong, solid structure. And that won't be found in nature; we'll have to build it.

(Others have suggested that it'd be better to mine comets. They tend to have lots of ice and gases, and those are very useful if you want to grow food. The problem is that the inner solar system has lots of asteroids but not very many comets. And the visiting comets tend to be in orbits that are expensive to get to. The closest asteroids with ice are around Jupiter.)

Re:A great idea

[rufty_tufty]

Well I'm not American and therefore not paying for this, but that aside:

I want humans to leave this rock, I think the only way to do it is to make space profitable. As soon as there is profit to be had, good luck stopping people from doing it. Once we're out there doing something profitable en-mass I think the other goals that people have of scientific research and romantic notions of colonisation will follow. I believe however that the quality of life can be best enhanced by making a profit from space rather than abstract research or having a dozen or so people on the moon. I can see several ways we *might* be able to make a profit in space in the foreseeable future:

* Asteroid Mining
* Space Tourism
* He3 (or other fantasy) moon mining
* Power Satellites

Going to Mars or a long term moon base may be very romantic, but we can't really turn them into a sustainable long term option with our current technology. I believe therefore the best thing to do is accept this and search for something else we can do that is just about within our grasp and would lead to a long term sustainable industry.
I'm assuming here of course that a moon base will be a sink of money and not a source. I'm also assuming that people's lives have most been improved by space projects like communications satellites and GPS rather than Hubble or the space shuttle.