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The moon has 1/6th of Earth's gravity and 0% of our atmospheric pressure. Mars has 1/3rd of the gravity and 0.6% of the pressure. Those 2 factors make them ve

The moon has 1/6th of Earth's gravity and 0% of our atmospheric pressure. 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.

superkuh 8y ago
It really doesn't though. Descent, entry and landing on the moon is completely different than Mars. You have you use entirely propulsive breaking to get rid of your orbital velocity. On Mars for very large payloads propulsive breaking is needed but aerobreaking is a huge part of it too. The Moon is not practice for Mars. It's a waste of time for political posturing.
- stcredzero 8y ago
  "Braking," not breaking. 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.
  - superkuh 8y ago
    > "Braking," not breaking. 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.
    - kbenson 8y ago
      > The moon is a bad place for that because now you have to carry all that extra fuel for landing/etc. 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?).
    - stcredzero 8y ago
      Low earth orbit is just fine for figuring out life support as has been done on the ISS already. 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.
    - quacked 8y ago
      ECLSS designs for a moon base would be very, very different from the ISS, there's no "we've already figured out life support" in LEO. The ISS is frequently restocked with consumables, which is less of an option for a moon base and not an option for Mars base, requiring an entirely different top-down design.
  - maxxxxx 8y ago
    I agree. Having a permanent station on the Moon would be a great prep for a Mars station. In case there is a problem you have a reasonable chance to send repair material or a rescue whereas on Mars one single failure will be the end of it. I think a Moon station should be routine before we go any further.
  - aaron_m04 8y ago
    > Mars soil isn't as bad, but some of it you don't want in your living space either. It's probably worse, since Martian soil has perchlorates, which are toxic and cause thyroid problems at low concentrations.
    - stcredzero 8y ago
      Some Martian soil may have hexavalent chromium, which can cause cancer and birth defects at low concentrations.
NickM 8y ago
A thin atmosphere is still very different from no atmosphere. If you have access to CO2 you can break it apart to get breathable oxygen, or use it as in ingredient to make methane to fuel a return trip. If you have no atmosphere to draw on at all, then it seems like it's a lot harder to become fully self-sustaining. 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.
logfromblammo 8y ago
Transport between bodies in space is measured by kilometers per second as delta-V, not kilometers. 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) In order for the Moon to be a stepping stone, it would have to be a refueling station where most of the mass involved ultimately comes from the Moon, rather than Earth. As it is now, the Lunar industrial plant produces 0 Mg of rocket fuel annually. For 30% more delta-V, a rocket from Earth can just go to Mars directly.
- Nomentatus 8y ago
  Thanks for the numbers. 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.
  - logfromblammo 8y ago
    Going directly from low orbit to a transfer orbit to the second body will usually save some delta-V over going to escape orbit first and then going to transfer orbit. I didn't have the numbers for low lunar orbit to Mars transfer orbit, so I changed the Earth to Mars path for a fairer comparison. 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.
cjensen 8y ago
The Moon also has far better solar energy potential. If you're going to have to live underground, better to do it someplace with lots of energy and close to help.

superkuh 8y ago

It really doesn't though. Descent, entry and landing on the moon is completely different than Mars. You have you use entirely propulsive breaking to get rid of your orbital velocity. On Mars for very large payloads propulsive breaking is needed but aerobreaking is a huge part of it too. The Moon is not practice for Mars. It's a waste of time for political posturing.

stcredzero 8y ago
"Braking," not breaking. 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.
- superkuh 8y ago
  > "Braking," not breaking. 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.
  - kbenson 8y ago
    > The moon is a bad place for that because now you have to carry all that extra fuel for landing/etc. 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?).
  - stcredzero 8y ago
    Low earth orbit is just fine for figuring out life support as has been done on the ISS already. 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.
  - quacked 8y ago
    ECLSS designs for a moon base would be very, very different from the ISS, there's no "we've already figured out life support" in LEO. The ISS is frequently restocked with consumables, which is less of an option for a moon base and not an option for Mars base, requiring an entirely different top-down design.
- maxxxxx 8y ago
  I agree. Having a permanent station on the Moon would be a great prep for a Mars station. In case there is a problem you have a reasonable chance to send repair material or a rescue whereas on Mars one single failure will be the end of it. I think a Moon station should be routine before we go any further.
- aaron_m04 8y ago
  > Mars soil isn't as bad, but some of it you don't want in your living space either. It's probably worse, since Martian soil has perchlorates, which are toxic and cause thyroid problems at low concentrations.
  - stcredzero 8y ago
    Some Martian soil may have hexavalent chromium, which can cause cancer and birth defects at low concentrations.

NickM 8y ago

A thin atmosphere is still very different from no atmosphere. If you have access to CO2 you can break it apart to get breathable oxygen, or use it as in ingredient to make methane to fuel a return trip. If you have no atmosphere to draw on at all, then it seems like it's a lot harder to become fully self-sustaining. 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.

logfromblammo 8y ago

Transport between bodies in space is measured by kilometers per second as delta-V, not kilometers. 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) In order for the Moon to be a stepping stone, it would have to be a refueling station where most of the mass involved ultimately comes from the Moon, rather than Earth. As it is now, the Lunar industrial plant produces 0 Mg of rocket fuel annually. For 30% more delta-V, a rocket from Earth can just go to Mars directly.

Nomentatus 8y ago
Thanks for the numbers. 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.
- logfromblammo 8y ago
  Going directly from low orbit to a transfer orbit to the second body will usually save some delta-V over going to escape orbit first and then going to transfer orbit. I didn't have the numbers for low lunar orbit to Mars transfer orbit, so I changed the Earth to Mars path for a fairer comparison. 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.

cjensen 8y ago

The Moon also has far better solar energy potential. If you're going to have to live underground, better to do it someplace with lots of energy and close to help.