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A lunar outpost is a good idea as a platform for staging deep space missions. Launching from the Moon is much cheaper than launching from Earth (in terms of del

A lunar outpost is a good idea as a platform for staging deep space missions. Launching from the Moon is much cheaper than launching from Earth (in terms of delta-V) if you can build out in-situ fuel production, plus more novel launch mechanisms like space elevators and mass drivers are more feasible on the Moon than on Earth. The far side of the Moon is also an interesting platform for astronomy. We'd also learn a lot about a Mars mission by being on the moon, such as proving out safe long-term habitats at a distance where rescue missions are feasible, studying the effects of low (rather than zero) gravity in the long term, etc.

Retric 9y ago
No it's currently vastly more expensive in terms of delta-V because you need to get the fuel to the moon at the cost of delta-V. Saying we could mine the moon at some point in the future is great, but why not just move an comet into earth orbit and mine that. It's about as feasible in theory, but does not require you to get out of the moon's gravity well. PS: If you really want rail guns, you can also get free delta-v from solar sails and use them maintain a launch platform's orbit.
- Sir_Cmpwn 9y ago
  >why not just move an comet into earth orbit This is probably substantially more difficult than establishing a moon colony and mining there. Comets have lots of orbital speed you have to overcome, and are generally pretty big. Edit: >PS: If you really want rail guns, you can also get free delta-v from solar sails and use them maintain a launch platform's orbit. Solar sails cannot maintain the orbit of an orbital rail gun launch platform -_- All of your ideas are more of a moonshot than an actual moonshot.
  - Retric 9y ago
    Solar sails provide free delta v if you are already in orbit and willing to wait. It's not useful for moving people around the solar system, but a rock that takes 100 years to get somewhere is not a big deal. On that timescale they can move literal mountains.
    - Sir_Cmpwn 9y ago
      Free delta-V, yes, but not much - certainly not enough to maintain the orbit of a mass driver.
      - Retric 9y ago
        As you just want station keeping you can ignore the mass of the sail and mass driver, all of the delta-v from the sail get's transfers to what the mass driver launches. Thus you can actually use a fairly thick sail without issue. The problem is because the station is staying still you are effectively limited to the square root of a sails acceleration. Still ~7 newtons per km^2 adds up and you avoid the delta v deficit from being on the moon in the first place.
        Sir_Cmpwn 9y ago
        You don't just need station keeping. Every launch takes energy away from the orbit of the launch platform. Consecutive launches basically deorbit the launch platform. To maintain the orbit, the solar sails must generate an equal amount of orbital energy as the launch platform imparts upon vehicles launched. In other words, you could just launch stuff with its own solar sail to the same effect. This happens on the moon, too, but the moon is basically a limitless supply of orbital energy.
        Retric 9y ago
        I think you misunderstood what I meant by station keeping. The sail is used to return the platform to it's orbit after launch. You probably want something else for normal station keeping. Anyway, I was wrong about the square root thing. It's 1:1. A 1km2 sail represents 7m/s/s for 1 kg of stuff. Normally the sail eats into that and you quickly get far from the sun, but that's not the case here. Fire a 100kg object at 20,000 m/s and a 10km/10km sail can return the station to orbit in around 50 minutes. Granted if you are in earth orbit it's a little more complex. But you probably want to be in a fairly high orbit anyway to maximize delta v.
- yread 9y ago
  You could use nuclear rocket engines on the Moon though with much fewer risks
nickik 9y ago
Sure if you make up some stuff that does not exist then its better. But if you actually want to talk about reality where we don't have a moon base that produces in-situ fuel, we don't have mining to get that, we don't have reusable lauchers to carry it into moon orbit and we don't have even a plan on how to store and use that fuel. Even if that was your goal to devlop, then a moon orbit station would be a bad idea. If you want to build a moon mining base, it is much smarter to go to the moon directly and have the capability to deliver massive payloads there. All that NASA is planning to do it establishing a small outpost and that will take at least 10 years. SLS/Orion/DSG are all very expensive and you can't even deliver anything to the actual moon. So you need another reusable laucher component that is not even in the budget. SpaceX architecture is also far, far cheaper. One booster, one ship that can land on the moon or on mars. Its far cheaper, simpler and more capable architecture. > plus more novel launch mechanisms like space elevators and mass drivers are more feasible on the Moon than on Earth Yes, but those are extremly far in the future and the DSG will not get us there. > The far side of the Moon is also an interesting platform for astronomy. Agree, but NASA is not planning on using that. Building a Space station near the moon will not help that effort. In fact, the money NASA is using to build SLS/Orion/DSG is cutting away money that could be used for such a telescope (as it already does for current missions). > We'd also learn a lot about a Mars mission by being on the moon, such as proving out safe long-term habitats at a distance where rescue missions are feasible, studying the effects of low (rather than zero) gravity in the long term, etc. Of course you can learn many things from the moon. But its also extremly different then Mars in many other ways. If your eventual goal for humans is mars, then using earth, orbit and mars itself is a far better investment.

Retric 9y ago

No it's currently vastly more expensive in terms of delta-V because you need to get the fuel to the moon at the cost of delta-V. Saying we could mine the moon at some point in the future is great, but why not just move an comet into earth orbit and mine that. It's about as feasible in theory, but does not require you to get out of the moon's gravity well. PS: If you really want rail guns, you can also get free delta-v from solar sails and use them maintain a launch platform's orbit.

Sir_Cmpwn 9y ago
>why not just move an comet into earth orbit This is probably substantially more difficult than establishing a moon colony and mining there. Comets have lots of orbital speed you have to overcome, and are generally pretty big. Edit: >PS: If you really want rail guns, you can also get free delta-v from solar sails and use them maintain a launch platform's orbit. Solar sails cannot maintain the orbit of an orbital rail gun launch platform -_- All of your ideas are more of a moonshot than an actual moonshot.
- Retric 9y ago
  Solar sails provide free delta v if you are already in orbit and willing to wait. It's not useful for moving people around the solar system, but a rock that takes 100 years to get somewhere is not a big deal. On that timescale they can move literal mountains.
  - Sir_Cmpwn 9y ago
    Free delta-V, yes, but not much - certainly not enough to maintain the orbit of a mass driver.
    - Retric 9y ago
      As you just want station keeping you can ignore the mass of the sail and mass driver, all of the delta-v from the sail get's transfers to what the mass driver launches. Thus you can actually use a fairly thick sail without issue. The problem is because the station is staying still you are effectively limited to the square root of a sails acceleration. Still ~7 newtons per km^2 adds up and you avoid the delta v deficit from being on the moon in the first place.
      - Sir_Cmpwn 9y ago
        You don't just need station keeping. Every launch takes energy away from the orbit of the launch platform. Consecutive launches basically deorbit the launch platform. To maintain the orbit, the solar sails must generate an equal amount of orbital energy as the launch platform imparts upon vehicles launched. In other words, you could just launch stuff with its own solar sail to the same effect. This happens on the moon, too, but the moon is basically a limitless supply of orbital energy.
        Retric 9y ago
        I think you misunderstood what I meant by station keeping. The sail is used to return the platform to it's orbit after launch. You probably want something else for normal station keeping. Anyway, I was wrong about the square root thing. It's 1:1. A 1km2 sail represents 7m/s/s for 1 kg of stuff. Normally the sail eats into that and you quickly get far from the sun, but that's not the case here. Fire a 100kg object at 20,000 m/s and a 10km/10km sail can return the station to orbit in around 50 minutes. Granted if you are in earth orbit it's a little more complex. But you probably want to be in a fairly high orbit anyway to maximize delta v.
yread 9y ago
You could use nuclear rocket engines on the Moon though with much fewer risks

nickik 9y ago

Sure if you make up some stuff that does not exist then its better. But if you actually want to talk about reality where we don't have a moon base that produces in-situ fuel, we don't have mining to get that, we don't have reusable lauchers to carry it into moon orbit and we don't have even a plan on how to store and use that fuel. Even if that was your goal to devlop, then a moon orbit station would be a bad idea. If you want to build a moon mining base, it is much smarter to go to the moon directly and have the capability to deliver massive payloads there. All that NASA is planning to do it establishing a small outpost and that will take at least 10 years. SLS/Orion/DSG are all very expensive and you can't even deliver anything to the actual moon. So you need another reusable laucher component that is not even in the budget. SpaceX architecture is also far, far cheaper. One booster, one ship that can land on the moon or on mars. Its far cheaper, simpler and more capable architecture. > plus more novel launch mechanisms like space elevators and mass drivers are more feasible on the Moon than on Earth Yes, but those are extremly far in the future and the DSG will not get us there. > The far side of the Moon is also an interesting platform for astronomy. Agree, but NASA is not planning on using that. Building a Space station near the moon will not help that effort. In fact, the money NASA is using to build SLS/Orion/DSG is cutting away money that could be used for such a telescope (as it already does for current missions). > We'd also learn a lot about a Mars mission by being on the moon, such as proving out safe long-term habitats at a distance where rescue missions are feasible, studying the effects of low (rather than zero) gravity in the long term, etc. Of course you can learn many things from the moon. But its also extremly different then Mars in many other ways. If your eventual goal for humans is mars, then using earth, orbit and mars itself is a far better investment.