Astronomy

The next Destination for NASA Astronauts



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Obama's revised plan for NASA eliminated all plans for the next trip to the moon, while preserving the future of Orion as an escape vehicle in low-Earth orbit. In a sense, this was the worst of all "ambitious" plans: most veteran space program watchers had already assumed the moon program was on the rocks, and building Orion simply as an escape pod for the International Space Shuttle means duplicating the cheaper but proven Soyuz spacecraft, currently built by Russia. Still, keeping Orion alive, even in this reduced role, means it's still important to debate where NASA astronauts should go next.

When we talk about the next destination for NASA astronauts, it's generally assumed that we are talking about somewhere ambitious. In other words, the next destination for NASA astronauts is a long-term goal, not simply a short-term reference to a few more trips into low-Earth orbit, where the International Space Station resides. We have the technology and, despite the current economic problems, the resources to think much bigger. In essence, there are three major, plausible destinations for NASA astronauts in the next couple of decades: the Moon, an asteroid, or Mars. Which of these should be the next destination for NASA astronauts depends on what, in the end, we want space travel to be about. Are we going into space just to see how far we can travel, or are we going into space because we have a vision for supporting human life, long-term, off this planet?

- Mars: The Ambitious Approach -

The ambitious approach - the one that brought humans to the Moon in 1969, knowing full well that we had no real plans for staying there for any length of time - says we should aim to send NASA astronauts to Mars. This could not happen in 2011 or even 2015; indeed, before landing on Mars, there would have to be several long-distance space voyages first, probably (if the Apollo history is any indication) possibly including a test flight to a nearby asteroid and one or more flights to Mars which simply orbit the red planet, attempting no landing.

There's no question that going to Mars poses formidable difficulties. The most obvious problems involve landing on that planet. Because of its thin atmosphere but relatively strong gravity, this is a much more complex task than landing on the Moon (less gravity makes it easier to maneuver a landing craft) or on the Earth (a strong atmosphere is a natural brake during re-entry). Current unmanned probes have to use a variety of innovative approaches that simply wouldn't work for a large, manned spacecraft, like bouncing along the ground cocooned in massive airbags (the method of choice for the Spirit and Opportunity probes).

More serious than Mars itself, however, is the journey in between. Far out from Earth, the astronauts would be at risk from greater solar radiation, for example. It might be possible to get around this by building a thickly shielded spacecraft - but that goes against all of the basic rules of spacecraft design, which say that all material must be as lightweight as possible to hold down the launch costs. Plus, they would need to learn to live together, without any other human contact, for perhaps one year.

The difficulties are immense, but the problems are probably not insurmountable. The real question is, where would we go next? A manned mission to Mars would test humanity's knowledge of space almost to the breaking point, and the astronauts would come back, realistically, with probably only a little more scientific knowledge than we could have gleaned from a series of far cheaper unmanned probe missions. The real benefit of going to Mars would be to see just how far into space we could send a human being. This is a little more important than a mere ego trip, but it does not necessarily give us much vision for where we would go from there.

- Back to the Moon: Baby Steps -

Going back to the Moon has another set of benefits and drawbacks. On the one hand, most importantly, we know we can do it - because we've been there before. A new lunar expedition, designed today and launched in a decade, would be far more capable than the comparatively primitive Apollo spacecraft of the 1960s and early 1970s. Even the first of the new lunar expeditions would probably be expected to operate for one or more weeks on the surface of the Moon (Apollo 16 was there for just three days).

On the other hand, there is an understandable sense that the Moon is a little bit boring, for the very same reason: we've been there before. Any technology that comes out of a new race for the Moon is going to be incremental, not revolutionary. (In other words, there probably won't be any 2010 equivalent of the invention of velcro.) Astronauts would probably land at a new site, and definitely would perform some experiments their counterparts in 1969 never dreamed of, but the basic formula for the first Orion mission would be pretty much the same: land, drive around in a buggy, collect soil samples, and head home.

However, going back to the Moon first does hold out one real benefit if we approach the subject from another direction. Instead of looking for scientific discoveries (which can usually be achieved more cheaply with robotic spacecraft) or simply pushing out as far as we can, as quickly as we can (which is what the Mars mission would be), it may finally be time to start looking out into space as humanity's next home. Even if the Earth can sustain us indefinitely (and the climate scientists, for one, are saying that it might not), one big asteroid is all that stands between us and extinction. To get around that, humans need to start living in space, and on other planets.

And if the goal of space travel is to achieve life in space, then the Moon is definitely the best next destination for NASA astronauts. Our relative familiarity with the Moon means there's at least a meaningful chance that we could begin designing the building blocks of a long-term outpost there. This would survive partially on material sent from Earth, and partially by processing raw materials on the Moon's surface. (It's believed, for example, that the Moon has sizeable amounts of helium-3, which could be used in next-generation power systems.) If we want to go to Mars to stay one day, then first we have to go to the Moon to stay.

Living on another planet, or even just on the Moon, would be phenomenally expensive to begin with. Nevertheless, if we look at space travel as an investment in humanity's future, and not just as a race to see how far away we can push a human craft, then going to the Moon may be the wisest choice for NASA today. It's less ambitious than Mars, but it offers us the best, closest test area for the skills and technology we will one day need to send future generations of astronauts to Mars and beyond.

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