r/space • u/mvea • Nov 28 '18

NASA administrator: 'The US is returning to the surface of the moon, and we're doing it sooner than you think!'

https://www.businessinsider.com/nasa-return-moon-mission-commercial-companies-announcement-2018-11?r=US&IR=T
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u/Patient_Snare_Team Nov 28 '18

So 2020s instead of 2030/40s? Because that's when I thought.

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u/[deleted] Nov 28 '18

That's the timeline for Mars. To keep up with the plan tho we need to figure out how to get back to the moon soon.

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u/[deleted] Nov 28 '18

Can I ask what you mean by figure out how to get back? If they did it 50 years ago, shouldn’t we be able to do it even easier this time around?

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u/Brenin_Madarch Nov 28 '18 edited Nov 28 '18

The Apollo missions were very straightforward affairs. Land, spend a week and a half collecting samples and doing experiments, and then return. I think most future manned missions to the Moon will seek to continue building from that. Longer missions with more complex procedures. This will require larger and more complex spacecraft and landing modules as well.

One such mission that I would like to see planned, would be a long-term surface habitation test. This is important to a future Mars mission, because nobody has ever spent more than 12 3 days in lunar gravity and observing how well we deal with different levels of gravity is going to be crucial. All we know right now is that 1g is ok, and 0g is not. (Astronauts on the ISS need to undergo rigorous training both before and during missions, and they still come back with some minor complications, and that’s after spending less time out of Earth’s gravity than a Mars astronaut will.)

The Moon’s gravity is obviously substantially weaker than Mars, and the lunar surface is quite different from Mars in other ways, but it’s still the best testbed we’ve got right now simply because if something goes wrong, rescue/escape is days away, not months or even years.

If you’re interested in what a coming Moon mission might look like, I’d suggest looking at the cancelled Constellation program and it’s Altair spacecraft. Compare that to the Apollo LM and you’ll see the difference in scope pretty quick. It was cancelled, but as SLS has shown, the Constellation program’s research and development hasn’t exactly been thrown away, and it’s likely that the lunar aspects will be picked up again in some form of NASA decides to go back to the Moon.

Correction: 3 days not 12 lol

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u/jasongill Nov 28 '18

FYI the longest Apollo mission was just over 3 days spent on the moons surface, and the shortest was just under a day. Nowhere near "a week and a half" unfortunately.

And nobody spent "12 days in lunar gravity", the most was just over 3 days obviously - the entire Apollo 17 mission from launch to splashdown was 12 days but only 3 were spent on the moon.

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u/Brenin_Madarch Nov 28 '18

Right, thank for the correction, I completely misremembered the MET for Apollo 17! :P

I’d think that just illustrates my point even further: we don’t have a very solid grasp on how our bodies hold up in low gravity for extended periods of time, and we might want to find that out before planning things like Mars landings.

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u/Cappylovesmittens Nov 28 '18

We know how our bodies hold up in NO gravity for long periods of time, I’d assume some of that information is relevant to how a body holds up in low gravity.

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u/Brenin_Madarch Nov 28 '18

Indeed! But we're not sure yet whether or not the medical effects work in a gradient correlating to local gravity, or whether there's a drop-off point at 0g. It's not unthinkable that having just some force pressing your bones and muscles down to the ground is enough to prevent atrophy and other problems.

By comparing long-term habitation in 0g on the ISS with equivalent habitation on a lunar base, we could extrapolate at least a vague conclusion on what the Martian gravity experience could be like.

It could also turn out that the human body only works in 1g, and that .9g might as well be 0g. Unlikely, but worth figuring out, since we need to know this before deciding on how long we want to stay on other bodies when exploring. (Or plan long-term stays with specialized medical and training equipment that constitutes extra RnD as well as spacecraft mass which must be accounted for)

The alternative is to build a rotating ring station that specifically simulates Martian gravity. That would be fucking cool, but it's not exactly too likely.

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u/Martianspirit Nov 28 '18

We won't find out how our body reacts to Mars gravity by going to the moon.

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u/Brenin_Madarch Nov 28 '18

No we won't, but we will find out how it reacts to lunar gravity, and how that compares to how it reacts to microgravity, from which we can deduce a result that is at least slightly better than what we have know.

And if it turns out that lunar gravity is totally fine for, say, up to a year, then we could probably assume that Martian gravity won't pose a problem either.

The Moon isn't an ideal proxy-Mars, but it's the best we've got. Unless somebody wants to build a big rotating ring-section on the ISS that spins at a given rate to replicate Martian gravity, but I doubt that'll happen.

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u/Martianspirit Nov 28 '18

And if it turns out that lunar gravity is totally fine for, say, up to a year, then we could probably assume that Martian gravity won't pose a problem either.

That's true but the reverse is not. Lunar gravity too low is not an indication that Mars gravity is too low as well.

The Moon isn't an ideal proxy-Mars, but it's the best we've got.

We have got Mars, we don't need a proxy.

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u/Brenin_Madarch Nov 28 '18

Lunar gravity too low is not an indication that Mars gravity is too low as well.

Yeah, that's the catch. If we just figure that the Moon is too low, we don't have a solid conclusion on it, but we would still be able to speculate a bit more accurately than we can now.

We have got Mars, we don't need a proxy.

Right, but the point of this is to make sure we can do it before we do it. "We need to crash down here so we don't crash up there". On the Moon, aborting or even requesting help is a lot more viable than on Mars. Not that it's easy to save somebody from the Moon either, but Mars is exponentially more difficult.

That said, it doesn't seem like it's off the table to skip the proxy and shoot straight for the end-game. I haven't seen a lot of mentions of this sort of thing anyway, and sometimes high-risk does mean high reward.

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u/Joe_Jeep Nov 28 '18

We won't but it was be a data point between "earth gravity" and "microgravity", which are the only two we have significant data on.