Author Topic: Utilizing the moon  (Read 10374 times)

Offline Warren Platts

Re: Utilizing the moon
« Reply #20 on: 10/20/2015 03:00 AM »
Found this on phys.org (from Oct. 14, 2015)

To save on weight, a detour to the moon is the best route to Mars

Launching humans to Mars may not require a full tank of gas: A new MIT study suggests that a Martian mission may lighten its launch load considerably by refueling on the moon.
 
Previous studies have suggested that lunar soil and water ice in certain craters of the moon may be mined and converted to fuel. Assuming that such technologies are established at the time of a mission to Mars, the MIT group has found that taking a detour to the moon to refuel would reduce the mass of a mission upon launch by 68 percent.

The group developed a model to determine the best route to Mars, assuming the availability of resources and fuel-generating infrastructure on the moon. Based on their calculations, they determined the optimal route to Mars, in order to minimize the mass that would have to be launched from Earth—often a major cost driver in space exploration missions.

They found the most mass-efficient path involves launching a crew from Earth with just enough fuel to get into orbit around the Earth. A fuel-producing plant on the surface of the moon would then launch tankers of fuel into space, where they would enter gravitational orbit. The tankers would eventually be picked up by the Mars-bound crew, which would then head to a nearby fueling station to gas up before ultimately heading to Mars.



Based on article in Journal of Spacecraft and Rockets
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Offline sdsds

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Re: Utilizing the moon
« Reply #21 on: 10/20/2015 05:43 AM »
Hi Warren. I saw this too, and was encouraged. But then:
Quote
they determined the optimal route to Mars, in order to minimize the mass that would have to be launched from Earth—often a major cost driver in space exploration missions

So if what you're minimizing is mass launched from Earth it seems no surprise at all that an architecture "wins" when it launches almost all its propellant from some body other than Earth....
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Online Archibald

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Re: Utilizing the moon
« Reply #22 on: 10/20/2015 06:35 AM »
use of space resources was considered for the Strategic Defense Initiative. http://www.wired.com/2015/02/strategic-defense-military-uses-moon-asteroid-resources-1983/
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Offline Warren Platts

Re: Utilizing the moon
« Reply #23 on: 10/20/2015 06:46 PM »
Hi Warren. I saw this too, and was encouraged. But then:
Quote
they determined the optimal route to Mars, in order to minimize the mass that would have to be launched from Earth—often a major cost driver in space exploration missions

So if what you're minimizing is mass launched from Earth it seems no surprise at all that an architecture "wins" when it launches almost all its propellant from some body other than Earth....

Well, that's because they said that mass launched from Earth is often a major cost driver....

use of space resources was considered for the Strategic Defense Initiative. http://www.wired.com/2015/02/strategic-defense-military-uses-moon-asteroid-resources-1983/

Now this is fascinating. I had not heard of the 1983 workshop before. I have done a little historical research on whether SDI had explicitly considered using Lunar resources, and could find little historical evidence to directly back that up. But the workshop would clinch that at least early on. Of course the song "Clementine" was not just about getting lost and gone forever--it was about about a miner 49er excavating for a mine...
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."--Leonardo Da Vinci

Offline spacenut

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Re: Utilizing the moon
« Reply #24 on: 10/20/2015 07:05 PM »
From what I understand, lox weighs more than liquid hydrogen, far more.  If you get oxygen out of the moon regolith (sand), and make lox, launch it to an L1 location.  Ship from earth will launch from earth and arrive at L1 empty of lox and refuel there.  They could refuel with methane in LEO, then go to L1 to pick up the lox.  It takes twice as much lox and methane for combustion so the weight is lox.  Launching tankers to and from the moons surface would be cheaper than from earth to L1 with lox.  So and MCT could launch from earth.  Refuel enough lox and fully with methane and go to L1 to load up with lox, then fire on to Mars.  They can refuel both on Mars for return.  Makes sense. 

Offline Kansan52

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Re: Utilizing the moon
« Reply #25 on: 10/20/2015 07:41 PM »
Welcome Quixote1.

You strike a cord for me because most questions ask 'either or'. Like moon base OR space station. But we should do both and more.

The simple answer is money. That leads to you to who doles out the money which, in America's case, is Congress. Presidents, lobbyists, voters, ect are all part of the mix. Lowering costs is exciting because it stretches what is available. IMHO, more government money should be spent on these endeavors.

One side bar I find interesting is robotic heavy equipment on the Moon. NASA has spent money with Caterpillar to prepare Cats for the Moon. Maybe others.

When India struck the Moon, the ejecta not only proved there was water ice but also gold. One group proposed a gold depository on the Moon. It would be built by robotic equipment then mine and fill it. The idea is people that own gold often have it in an Earth depository, virtual ownership not physical. That hasn't seemed to proceed much.

However, harvesting ice and preparing LOX could be robotic. I prefer the old approach of solar powered mass drivers. These are large electromagnet rails that 'fling' payloads from the Moon surface to where the payload is needed. If memory serves, Kevlar could not be used for a lunar space elevator but carbon fiber tech could. Mass drivers seem quicker and less expensive with the little info I have.

But yes, even with all the minuses, a Moon base as well as a space station as well as Mars seems the best to me.

Offline JasonAW3

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Re: Utilizing the moon
« Reply #26 on: 10/20/2015 08:27 PM »
Crazy idea here;

     Is it possible to arrange an orbit far enough from the moon, yet not heavily influenced by Earth's gravity, so that whatever is positioned in said orbit, stays permantely in the Moon's shadow?

     I imagine that such an orbit is likely to fall too close to Earth to maintain, but if not, then that could be a solution for cryostorage of propellants.  (Of course it might also be too costly in fuel to be able to use, even launching from the moon or L-1).
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Offline Phil Stooke

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Re: Utilizing the moon
« Reply #27 on: 10/20/2015 08:42 PM »
I don't think that is possible, but it doesn't need to be.  Anything that casts a shadow will do the job.  So the storage facility can use its own sunshade, the way the JWST will do.

Offline Kansan52

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Re: Utilizing the moon
« Reply #28 on: 10/20/2015 08:44 PM »
L-2 with a halo orbit should do but Phil's point seems like it would be much easier.

Offline JasonAW3

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Re: Utilizing the moon
« Reply #29 on: 10/20/2015 09:18 PM »
I don't think that is possible, but it doesn't need to be.  Anything that casts a shadow will do the job.  So the storage facility can use its own sunshade, the way the JWST will do.

      Well, the reason I was thinking about it was that it likely would be much easier in the long run to maneuver a NEO comet, using a remote control thruster system, (using the mass of the comet itself, of course) to both slow down and redirect a comet into the moon's shadow.  This would make an excellent source of reation mass, coolants and consumables in general.

      Obviously, you'd want to use gravity to slow the comet as much as possible, so a flyby of Jupiter, Venus and the Sun, would likely be the best bets on the actual decelleration, so long as they are in the right positions.

      This would be a job of more finese than of brute force, but I suspect that it may be possible to do.  Again though, you'd want to make sure that you have the beast under control, or at least have enough control to redirect it into the moon itself if things go sideways.
« Last Edit: 10/20/2015 09:20 PM by JasonAW3 »
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Offline Warren Platts

Re: Utilizing the moon
« Reply #30 on: 10/21/2015 09:18 AM »
There's no stable orbit that's permanently in the Earth's shadow, let alone the Moon. Length of Earth's shadow = ~1.4e6 km; distance to Sun-Earth L2 point = ~1.5e6 km
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Offline Proponent

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Re: Utilizing the moon
« Reply #31 on: 10/21/2015 09:43 AM »
It's true that Earth L2 lies outside the Earth's umbra (the region where Earth completely blocks out the sun), but it is within the penumbra, meaning that Earth blocks part of the sun.  At L2, the Earth's angular (apparent) diameter is (12,700 km)/(1,500,000 km) = 0.0085 radians, while the sun's is (1,400,000 km)/(149,600,000 km + 1,500,000 km) = 0.0093 radians.  Hence, right at L2, Earth blocks (0.0085 rad/0.0093 rad)2 = 84% of the sun's disk, and maybe a bit more of the sun's light, since Earth fully blocks the inner, hotter region of the sun.

However, maintaining a large amount of blocking would require staying close to the Earth-sun line, "close" meaning much less than Earth's radius.  I would guess that's probably pretty tough to do.

Offline Warren Platts

Re: Utilizing the moon
« Reply #32 on: 10/21/2015 12:28 PM »
That is interesting. So, it may turn out that SEL-2 could be a better place for a passively cooled propellant depot--and hence to launch a Mars mission from--than EML-2. The delta v difference between the two is only ~50 m/s.

The station keeping itself probably wouldn't be a big deal--the boiloff would be more than enough to handle it I'd guess.

Wonder if you could get a double Oberth effect from SEL-2, by slingshotting off both the Moon and the Earth when heading to Mars that would be greater than launching from EML-2?

Radiation environment there might be bad.
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Offline Proponent

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Re: Utilizing the moon
« Reply #33 on: 10/22/2015 11:05 AM »
To my knowledge, neither WMAP nor JWST makes use of Earth as a sunshade, yet both need to stay very cool.  There must be a reason for this, and that drives my suspicion that staying near the center of the penumbra raises station-keeping requirements substantially above those needed anyway for station-keepling along the Earth-sun line (since L2 is not stable in that direction).  It could be, as you suggest, that a hydrogen depot would have enough boil-off to render the concern moot, but I'd like to know more about the problem.

I don't see why radiation would be significantly worse at Earth L2 than lunar L2: the latter is many lunar radii from the moon, so the moon won't provide much shielding.

A disadvantage of Earth L2 as a staging point is the long transit time from Earth.  If we approximate the trip as half of a 300-by-1,500,000-km elliptical orbit, it's going to take 35 days to get there.  And, if I recall correctly, DSCOVR took quite a bit longer than that to reach Earth L1.

Just thinking out loud about departure trajectories.....

First, a little terminology.  I'll define a slingshot as a close fly-by to change trajectory without application of thrust.  If thrust is applied at periapsis, I'll call it a Heinlein maneuver.

I see two things one could do.  One is to slingshot off the moon on the inbound leg and execute a Heinlein maneuver near Earth.  The lunar slingshot might reduce the delta-V needed at L2 to approach Earth.  But that delta-V is probably small anyway, so I would guess the inbound lunar slingshot is of little if any benefit.

Another option is a Heinlein near Earth followed by a slingshot off the moon.  You might even go all WSB and use multiple outbound lunar slingshots.

Offline muomega0

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Re: Utilizing the moon
« Reply #34 on: 10/22/2015 01:53 PM »
Well, the reason I was thinking about it was that it likely would be much easier in the long run to maneuver a NEO comet, using a remote control thruster system, (using the mass of the comet itself, of course) to both slow down and redirect a comet into the moon's shadow.  This would make an excellent source of reation mass, coolants and consumables in general.

      Obviously, you'd want to use gravity to slow the comet as much as possible, so a flyby of Jupiter, Venus and the Sun, would likely be the best bets on the actual decelleration, so long as they are in the right positions.
Where do you look for water on the moon?  In craters.
How did the craters appear?  asteroids and comets.
What brought water to the moon? asteroids. "a large asteroid can deliver more water to the lunar surface than the cumulative fall of comets over a billion year period"

Where are most of the asteroids?  Most asteroids are between Mars and Jupiter 
Why not extract the resources "in-situ"? and avoid the gravity wells, as recommended by Griffin and many others.

To my knowledge, neither WMAP nor JWST makes use of Earth as a sunshade, yet both need to stay very cool.  There must be a reason for this, and that drives my suspicion that staying near the center of the penumbra raises station-keeping requirements substantially above those needed anyway for station-keepling along the Earth-sun line (since L2 is not stable in that direction).  It could be, as you suggest, that a hydrogen depot would have enough boil-off to render the concern moot, but I'd like to know more about the problem.

I don't see why radiation would be significantly worse at Earth L2 than lunar L2: the latter is many lunar radii from the moon, so the moon won't provide much shielding.

A disadvantage of Earth L2 as a staging point is the long transit time from Earth.  If we approximate the trip as half of a 300-by-1,500,000-km elliptical orbit, it's going to take 35 days to get there.  And, if I recall correctly, DSCOVR took quite a bit longer than that to reach Earth L1.
You could use power for attitude control, just like on the LEO depot and Mars depot.
If one used the earth to block the sun, then this depot would be different from the LEO and Mars Depots.
If one uses power for attitude control, then one has power for coolers, similar to the LEO and Mars depot.
If one harvests propellant from the lunar surface, then one needs coolers and power ==>LEO/Mars Depots.
If one had power and coolers, would the boiloff problem be considered moot?

If for some reason the boiloff technology is not matured (intentionally?), then one could resort to large sun shields in the proper orbit, likely using power for attitude control and the "sun shield" could be a portion of a solar array.  All zero boiloff depots start with a sun shield. 

The advantage of L2 (vs L1) of course is that
     For a trip to and from L1, CEV will need ~700 m/s      to get in and out of L1:  1400 m/s.
     For a trip to and from L2 using lunar powered swingbys, CEV would only need ~330 m/s each time: 700 m/s.

Here are Farquhar's transfer times of 3 to 6 days if transit time is of concern.
« Last Edit: 10/22/2015 01:57 PM by muomega0 »

Offline Proponent

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Re: Utilizing the moon
« Reply #35 on: 10/22/2015 09:38 PM »
What do you mean by "power" for attitude control?  Electricity?

Offline denis

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Re: Utilizing the moon
« Reply #36 on: 10/22/2015 10:58 PM »
To my knowledge, neither WMAP nor JWST makes use of Earth as a sunshade, yet both need to stay very cool.  There must be a reason for this, and that drives my suspicion that staying near the center of the penumbra raises station-keeping requirements substantially above those needed anyway for station-keepling along the Earth-sun line (since L2 is not stable in that direction).  It could be, as you suggest, that a hydrogen depot would have enough boil-off to render the concern moot, but I'd like to know more about the problem.

I think you are right that trying to maintain something very close to L2 requires much more propellant than just maintaining it in a large Halo or Lissajous orbit (with typical size of a few hundred thousand kilometers).

However, the main reason not to keep a spacecraft in the penumbra is that you need electrical power. The orbits for such missions are usually designed to avoid any eclipse from the Sun by the Earth during the whole mission duration, to ensure both availability of solar power and maintaining a stable environment.

Offline MattMason

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Re: Utilizing the moon
« Reply #37 on: 10/23/2015 09:33 PM »
I've mentioned this notion in related threads, and I'll do so here in brief, although I think someone added bits of this idea, too.

I concur that going to the moon right now for any government is hardly a priority, and the current vibe is that leaving for Mars from Earth is more time and cost efficient than using the moon as a waypoint or fuel station.

So how would anyone now utilize the moon? As a commercial venture. Not for mining but for recreation. Basically, moon-based habitats, be they hotels or even permanent residences. A home for the elderly would be awesome for aged bones and muscles in 1/6 Earth gravity. Sports would be incredible. Swimming would be weird. Medicine might be fascinating. The view, incredible.

But this requires an infrastructure only the Mariotts and Hiltons may want, but they would want the sports leagues and food and supply services to also come. All that requires reliable transport, but before that, a place to go to in the first place.

Private space enterprise is just cutting its baby teeth in LEO and the most consistent it's got are cargo ships, with no commercial waystation to begin a moon construction project. We have a company with the habitat tech, but no buyers just yet. I think it will come because someone like Jeff Bezos is hellbent on "human space transportation," and he's of the tourist mindset. But he can't do it alone and we're still lacking the "push" to get others to want it, too. Technology is like that, or you'd have your HD-DVD player or other technology that just didn't get to a critical mass of interest.

But I feel that once the privateer space barons get their rails and trains completed and going to somewhere often and safely, this will follow--maybe faster than going to Mars. But SpaceX is a separate quotient, apart from any interest on the moon for now.
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Offline Coastal Ron

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Re: Utilizing the moon
« Reply #38 on: 10/27/2015 06:22 PM »
So how would anyone now utilize the moon? As a commercial venture. Not for mining but for recreation. Basically, moon-based habitats, be they hotels or even permanent residences. A home for the elderly would be awesome for aged bones and muscles in 1/6 Earth gravity. Sports would be incredible. Swimming would be weird. Medicine might be fascinating. The view, incredible.

I think one way to try to imagine what type of use we could make of the Moon, would be to do a thought exercise.

What if transportation to and from the Moon were free?  No matter how many times you travel between Earth and the Moon?  And perceived to be very safe too.

Everything else would cost the same, but transportation costs would be free.

How would that change the perception of what the Moon could be used for?
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline sdsds

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Re: Utilizing the moon
« Reply #39 on: 10/27/2015 07:32 PM »
[...] a thought exercise.

What if transportation to and from the Moon were free?  No matter how many times you travel between Earth and the Moon?

I like the idea of a thought experiment that simplifies reality, as a first approximation at least. In your magically simplified world, is just human transportation free and safe, or material goods too?
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