Thursday, July 16, 2009

Lunar Exploration

What if a NASA's lunar budget hadn't been axed in 1967? That's the question an article in New Scientist asks and answers.

It's July 2009, and in Johnson City, America's permanent colony on the moon - named after Lyndon B. Johnson, the president who authorised it - they are celebrating the third generation of lunar Americans: the first child born to parents themselves born on the moon. With just 5000 inhabitants, "city" is perhaps too grandiose a term.

(I guess that would make it too small to qualify in CNN's Best Places to Live database. But I digress.)

The New Scientist article is a wonderful fantasy. It's what all us space nuts - and I certainly am one - wished for when we read Heinlein and Clarke as kids. But is it remotely realistic? What the article keeps in very soft focus is any talk of whether money is being made out there in space.

There's talk of a trade in mined helium-3 for use in fusion reactors on Earth - if fusion technology ever gets established on the mother planet.

Cool. But even in this rose-tinted alternate history we still don't have fusion technology, much less a technology specifically based on helium-3. So there's merely "talk".

Shipping costs of material from Earth are still astronomical, and local extraction of water and oxygen is a boom business.

Right now, the cost to lift a kilogram into Low Earth Orbit is about $10,000. That goes up if you used man-rated vehicles, which presumably they've used a lot of if there are 5,000 people on the Moon. And it goes up even more when you realize that it's much more costly to go to the Moon that to LEO. Getting to the Moon requires about 40% more delta-v just to reach a transfer orbit, plus another chunk of delta-v for landing on the Moon. The Apollo mission did this in three stages: the whole Command Module/Lunar Excursion Module stack performed a translunar orbit insertion burn, then the LEM undocked and performed a deorbit burn, and finally the LEM used braking rockets to reach the surface at a survivable speed. The lack of a Lunar atmosphere, while a boon to launching from there, is a problem for landing: you can't aerobrake or use parachutes. So while the Apollo Command Modules could get back to Earth essentially unpowered ("essentially" because they reserved a little maneuvering fuel to make sure they were in the right window for re-entry), a Lunar lander has to use big engines the whole way in.

Adding delta-v adds tremendously to cost, because the rocket equation is exponential. Staging helps, of course - that's how Apollo did it. But the cost of lifting one kilogram from Earth to the Lunar surface would still be factors more than $10,000.

But let's say for the sake of argument that in the New Scientist scenario, rocket technology has improved enough that cost to LEO is $1,000/kg and cost to the Moon is $10,000/kg. How much would Lunarville cost to resupply? The ISS has a current crew of 6, is resupplied about 2.5 times a year, and the average resupply mission brings in 2.5 metric tonnes of supplies (this all comes from Wikipedia, so take with the appropriate amount of salt, but I trust the numbers are close enough for our back-of-napkin calculation). That's about 1 metric tonne per person per year. Lunarville, then, would require about 5,000 metric tonnes per year. At $10,000/kg, that's about $50 billion per year. Even if we assume that the Loonies are highly efficient recyclers, mine much of their own water locally, etc., just the resupply cost is still going to be huge.

Granted, a mere $50 billion/year may seem like chump change compared to the kinds of numbers bandied about today, but it's worth noting that NASA's peak budget - in 1965 - was only $33.5 billion (2007 dollars). So this scenario proposes that the popularity of a Lunar base would be so high that merely resupplying it at an annual cost higher than NASA's entire budget, when NASA was as popular as it ever was, would be politically feasible for 40+ years. And this does not factor in the rest of the scenario about Mars missions and the like. I find this unlikely, to say the least.

I wish that we'd gone into space as much as the next guy. Maybe more. I can even give you sociological reasons to go (more on this another time). I just don't see how either the science or the politics works out, though. Maybe if we do develop He-3 fusion technology on Earth, we can make Lunar mining of it profitable. But even if that were to happen, I think it's more likely we'd end up with a mostly-automated mining outpost than a full-fledged city.

What would induce people to actually emigrate in large numbers to outer space? It would have to make more sense (in cost, in political will, in scientific value, etc.) to go in person than to send robots. Or the cost would have to drop so far that other factors come into play - for example, it doesn't make "sense" by any of the above factors for my family to travel to London for a week, but we might do it anyway just for the fun and the experience. There's some indication that some forms of space flight might be in this range for the super-rich in the near future. But these short hops are a far cry from emigration.

We space nuts have to keep hoping for some game-changing technology, I think. We won't see large-scale manned space flight otherwise.

No comments:

Post a Comment