Moon Is Stepping Stone, Not Alternative to Mars, NASA Chief Says
scientificamerican.com
scientificamerican.com
"Each Apollo mission increased the mass of the lunar atmosphere by about 30%, and it took several weeks for the atmosphere to return to its natural state. Highly sensitive measurement or communication instruments may be affected by the additional atmospheric particles." [1]
"Studies have also revealed that the balance is very delicate. At present, the solar wind sweeps the lunar atmosphere into space very efficiently, limiting its density to that of a collisionless gas (an exosphere). If the atmosphere were, however, a factor of just 1000 denser, this process would invert itself and the atmosphere would remain stable for tens of thousands of years. Just the Apollo missions to the Moon increased the atmospheric density by a factor of 10 with rocket exhaust (mostly CHON compounds). Large scale human activity on the Moon could push the total mass over the limit and create an artificial atmosphere, pushing the Exobase off the surface and creating a stable, if highly tenuous atmosphere which could threaten precisely the most important asset that the Moon can offer us: its sterility and almost atmosphereless nature." [2]
[1] http://www.tsgc.utexas.edu/tadp/1995/spects/environment.html
[2] https://web.archive.org/web/20050214155703/http://www.iac.es...
Zubrin's 'The Case For Mars' (which on reading, it's obvious SpaceX have based a lot of their strategy on) is categorically against going back to the Moon and using it as a 'stepping stone'.
Zubrin's 'Mars Direct' architecture shows quite plainly that it is possible using current technology readiness levels and funding to send a significant scientific mission to Mars directly, without the need for huge orbital infrastructure or Moon Bases.
I had a similar feeling when SpaceX announced their #DearMoon project. I truly hope the Moon doesn't distract them from their true goal: the timely establishment of a permanent human presence on Mars.
We've been to the Moon. We don't need to go back. We need to aim higher.
He's obviously still pro-Mars, but in that interview he seemed less anti-Moon than he was in the past (but emphatically against certain approaches).
In an absolute sense, we don't need to do either.
I believe the Moon will support the first permanent population of humans outside Earth.
It remains to be seen if there is any meaningful physiological difference between 1/6 G and 1/3 G. If not, the experience of living on either will be more similar than not. My gut feeling is that there will have to be centrifugal "gravity" available on both the Moon and Mars.
I think the Moon has one thing that Mars does not - it is an attractive spot for heavy industry producing goods shipped to Earth, with abundant solar energy to boot. There is no issue with nuclear power there either.
For example, spacex wants to test the BFS. They could send it on a wide orbit 2 days away, or they could orbit around the moon instead. Going for the moon is probably only slightly different (ie different orbit insertion) but other than that it would be the same, except awesome pics/video.
Mars has 1/3rd of the gravity and 0.6% of the pressure.
Those 2 factors make them very similar to each other and the distance makes the moon the clear candidate for a first step.
Earth LEO 9.3 km/s
LEO escape 3.22 km/s
escape MTO 0.6 km/s
MTO MCO 0.9 km/s
MCO LMO 1.4 km/s
LMO Mars 4.1 km/s
-----
19.5
Earth LEO 9.3 km/s
LEO LLO 4.04 km/s
LLO Moon 1.87 km/s
-----
15.2
Moon LLO 1.87 km/s
LLO escape 1.40 km/s
escape MTO 0.6 km/s
MTO MCO 0.9 km/s
MCO LMO 1.4 km/s
LMO Mars 4.1 km/s
-----
10.3
(Earth -> Moon -> Mars = 25.5 km/s)
30% of delta-V but much more than 30% more fuel used (etc) since "compound interest" applies as you're using fuel to ship fuel out of orbit and then much of that fuel again to change your orbit to mars, etc.
Similarly, Napoleon came up against the limits of using horses to pack hay for horses invading Russia - compound interest; you can only do so much.
PS - that 30% assumes a path that I don't, and no solar power used to catapult oxygen off the moon. I'd go for a Lagrange point you're ignoring.
PPS - you've assumed Mars, not, say, near-earth asteroids or trojans with a very different, far lower delta-V. Vastly different problem.
I didn't forget the Lagrange libration points, but decided not to include them because they were not relevant to the parent comment, and they would still require some mechanism to get propellant mass up to them. They're currently almost empty, and won't be very useful until the Moon itself has launch capacity to get water up there. Again, I was mainly responding to the parent post.
The rocket equation is indeed a bear. As delta-V scales linearly, fuel requirements scale up exponentially. One way to manage it is to use stages. Another is to refuel and assemble vehicles higher up in the gravity well. As it happens, shipping tanks of fuel and propellant up to LEO separately means that missions to Mars starting fully fueled from LEO would require only 0.9 km/s more than missions starting from the lunar surface. Measuring by delta-V, LEO is at about the halfway point for an Earth-Mars mission.
But it's also worth noting that the surface of the Moon is closer to LEO than the surface of the Earth. Shipping fuel and propellant from the Moon to LEO, to rendezvous with and refuel a vehicle coming up from Earth, is even cheaper than shipping up the resupply mass from Earth.
The Moon is not practice for Mars. It's a waste of time for political posturing.
Some of the most difficult challenges have to do with maintaining life support long term. The Moon isn't a bad place for that. If we're able to deal with operations in conditions dealing with vacuum, that experience is still applicable. Also, the human side of the procedures for preventing lunar dust and grit from entering the living space will be important and applicable to Mars. Mars soil isn't as bad, but some of it you don't want in your living space either.
Ah jeez. That's what I get for commenting right after rolling out of bed.
> ... the most difficult challenges have to do with maintaining life support long term. The Moon isn't a bad place for that.
The moon is a bad place for that because now you have to carry all that extra fuel for landing/etc. Low earth orbit is just fine for figuring out life support as has been done on the ISS already. Why do it again in some place there's no reason to go to? There's no nitrogen available on the moon.
The dust thing is applicable but minor.
Entirely false. On the Moon, we can exploit in-situ resources for life support. Regolith can be used for radiation shielding and the extraction of oxygen. We can even harvest water in certain locations. Crops can be grown using hydroponics. Doing these things while maintaining a spaceport on another world isn't going to be nothing. Getting experience doing ground based operations is going to be valuable. It's not just "dust." It's probably literally tens of thousands of things we will have to learn through hard won experience.
Ground-based operations. Better to get the experience where help is only 3 days away.
I think that might be outweighed by the fact that the transit time is a few days compared to months, and launch windows are plentiful. It's better to test with all the benefits we can initially, IMO, as failure has such a high cost (in all aspects. How long do you think it would take for the public to get over their distaste of manned missions or colinization efforts after a big failure?).
It's probably worse, since Martian soil has perchlorates, which are toxic and cause thyroid problems at low concentrations.
There is also something to be said for sending humans to a place where humans have never been able to go before. To many people, that's an end goal in and of itself.
And Mars in particular is better left pristine until we've had a really good look for signs of life.
Example: FB events for my shows have, in the description of the event, the location/date/time/cover charge/ticket link. All of that information is present well above that, but people will STILL post on the event wall asking where/when/how much if I don't do that. shrug
- Are we largely constrained in our ship design since everything has to be structurally capable of handling launch and re-entry from earth's gravity well?
- How would our ship designs change if they were just meant to transport heavy loads and never actually re-enter a major gravity well? Similar to the Gateway hand-off mentioned in the article
- Wouldn't asteroid mining, resource harvesting be easier from a semi-permanent base that's still reasonably close to earth?
- Doesn't "Moon Base" just sound really freakin' cool?
https://www.quora.com/profile/Robert-Walker-5
Specific answer to why moon first:
> I think we are best not rushing into space, there’s no hurry about that. Let’s find out about space first, explore, learn, learn about our own capabilities too, [...]
Exactly the same argument can be made then.
> [...] have settlements in space when and where they are acutally needed, as the needs arise.
By then it will be too late. The idea is that we learn by doing.
> All this is hugely expensive and Earth would have to foot the bill. Because there is no way that they are going to turn a profit on Mars.
All this is hugely expensive and UK would have to foot the bill. Because there is no way that they are going to turn a profit in America.
> Not many peopole could afford a $200,000 spacsesuit.
"640K ought to be enough for anybody"
The most convincing part of his argument is weeks-long Martian dust storms.
So let assume they can make oxygen, water, maybe even calories. Great. Self supporting base.
But other than that. Everything will have to be trucked in. Pipes, electrical wires, valves, medical supplies, antennas, plastics, etc.
Will any of these be manufactured on-site in say 2050 ?!
With plenty of space and plenty of resources at hand, long term there's no reason a mars colony could not be self sustaining.
Whether that could be true as early as 2050 would depend, of course!
But launching a human is still more expensive than launching several robots.
Right now, launching humans is getting cheaper every year. Space missions are projected to become more profitable over time as people start space mining and later space fabrication.
So I agree with you that launching robots right now has a higher ROI than launching robots.
I think we also agree there's a crossover point.
Where I think we disagree on is when that crossover point might. You say 100 years; I think with current trends it could be under 50 years, maybe under 25 years.
Why do you think it'll take 100 years to hit crossover?
In about 200 years or so, I wouldn't be at all surprised if there were more people off earth than on it.
I really wish for you to be right, but with population growth slowing down, and possibility of building floating cities or terraforming Sahara, building large orbital stations or going to mars in large numbers may be economically not viable, unless we invent something radically new.
Even the most automated of robotic factories on earth still have a number of humans in an oversight role, where they make themselves quite useful.
The same would be true of any space industry. People would be hired on for a tour in space, and they'd be paid sufficient salary to make it worth their while.
And sadly, I would expect the end result of this sentiment to be fewer probes rather than cooler projects.