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I Moon vs Earth for launch to Mars

  1. Dec 31, 2017 #1
    Problem - we have to use large amounts of fuel/propellant to exit the earths atmosphere to enter earth orbit, the moon or other planets....

    Solution - would it not make sense to launch from a base on the moon?

    Problems I see, potentially....
    1) Is the moon’s orbit around earth problematic for trajectory calculations ? (Earth orbit around sun plus moons orbit around earth, and Mars orbit around sun)
    2) Are there less opportunities to launch from the moon to reach Mars? (Planetary alignment for shortest duration of travel)
     
  2. jcsd
  3. Dec 31, 2017 #2

    PeroK

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    There's the small matter of getting to the moon and building a rocket and launch site there.
     
  4. Dec 31, 2017 #3
    Getting to the moon I don’t see as a problem. Trump has already signed documents allowing for more funds to go to our space program. Also Space X is planning on orbiting the moon with two people by 2020.
     
  5. Dec 31, 2017 #4

    PeroK

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    If getting to the Moon isn't a problem, how come getting to Mars is? Can't Trump just sign up to that as well?
     
  6. Dec 31, 2017 #5
    I am not an expert but If I compare the needed fuel to launch from moon-mars and earth-mars I think moon is better option. Even we need to make some adjustments for orbital motion or etc. the needed fuel will be much less then the current one.
     
  7. Jan 1, 2018 #6

    stefan r

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    If the petro-chemical industry, air separation plants (equipped with air) and rocket manufacturing industries were located on the moon then launching from Earth surface to Mars surface would be much harder. Establishing industries on the moon is something to think about. IMO best to start with something easier like a telescope on the pole.

    Launching from lagrange 1 or 2 has advantages. Low lunar orbit would be worth considering. If the equipment/people/methane are coming from earth then landing them on the moon certainly does not help with getting to Mars. You can make a case for extracting Oxygen from lunar soil. Also if the Mars transport is using soil to grow food then bulking up with lunar dust might help. Certainly need to test growing food in space a lot before depending on it. There has been research on extracting aluminum and iron from lunar regolith. An ingot of pig iron is not a spaceship.

    If there is enough extractable water we could get the reducer from the moon too. Oxygen is most of the mass of a rocket so getting reducer makes much less of a difference. That would still be just the fuel tanks. The occupied cabins and equipment would still launch from earth and rendezvous with the fuel in space. If you build a lunar industrial complex there is a good chance it will import hydrocarbons.

    A fun idea to think about is the cis-lunar tether transport system. You can take the moon's momentum and use it from an orbit close to Earth. Phobos is in a good location. It is much easier to launch off of Phobos.

    That might be work instead of entertainment. An undergraduate should be able to do it for an upper level course project. It does not need to be exact. The main rocket burn will likely be near earth to maximize the Oberth effect. There will be a short correction burn after leaving LEO space whether it was a flyby or started in LEO.
     
  8. Jan 2, 2018 #7
    POTUS can only direct NASA to change its priorities _within budget_ approved by Congress.

    Some of NASA programs are also part of US laws, and thus can not be changed by POTUS. For example, SLS is whimsically called "Senate Launch System" exactly for the reason that Congress specifically directed NASA to build a heavy-lift launch vehicle using Shuttle-like components.

    IOW: POTUS alone can't do much to improve US space program.

    Thankfully, with SpaceX US space program is now gradually slipping out of government planning.
     
  9. Jan 2, 2018 #8

    Al_

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    There is water ice at the poles of the Moon.
    Once we have done the research and development of robot mining machines and H2 and O2 fuel producing plant, and sent them up there and started them working, we can go anywhere in the Solar System for much less cost than anyone else.

    Who mines the moon, owns all the moons.
     
  10. Jan 2, 2018 #9
    We'll just adapt our Earthly robotic mining machines and H2 and O2 fuel producing plants... oh wait. We don't even have those.

    Seriously though.
    You are, of course, right. Something along those lines would work.
    Creating Moon bases and then industrial infrastructure is the main, and quite non-trivial task. One which makes Apollo program look easy-ish.
     
  11. Jan 2, 2018 #10
    The point of the Moon is that it has raw materials (as a minimum, for fuel production). A space station/refueling depot does not.

    It might make sense to construct spacecraft there (if it's too fragile and benefits from zero-G, for example), but all fuel, materials and components need to come from somewhere.
     
  12. Jan 2, 2018 #11

    PeroK

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    It seems to me that once you propose/assume the technological capability of full mining and construction operations on the Moon, you may as well propose/assume sufficient advances in rocket technology to make launch from Earth equally feasible.
     
  13. Jan 2, 2018 #12

    russ_watters

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    I wouldn't. Launch technology has essentially stagnated for 50 years after fully maturing in 10. What is needed isn't "advances", but a totally new and radically better launch technology materializing out of thin air. Meanwhile, computers/robotics have advanced by leaps and bounds over the past 50 years and show little sign of stopping.

    Don't get me wrong; I don't think robotic lunar mining is on the foreseeable horizon as something we WILL do, but it at least it is foreseeable as something we CAN. do.
     
  14. Jan 2, 2018 #13

    russ_watters

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    Has this shown to be a real problem? It sounds to me like a Star Trek problem.

    Using some made-up numbers to illustrate: if we built a totally autonomous mining and fuel depot on the moon for a cost of a trillion dollars and it reduced the cost of manned trips to Mars from a hundred billion dollars to eighty billion dollars apiece, how many trips to Mars would we need to make in order to break even on the cost of the lunar facility?
     
  15. Jan 2, 2018 #14

    stefan r

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    There is water on the surface of the moon in the same sense that dry concrete has water on a clear summer day. Except that dry pavement has more. The equator has energy. You need power to mine, to refine ore into metals and oxygen.

    Solar power can run the mass driver(s) that move product into orbit. A tether from Lagrange 1 or Lagrange 2 is shorter and simpler if it runs to the equator.

    Sure. And some of the moons have surfaces made of water.

    I think it more likely that hydrogen (or hydrocarbons) will be routed back to the moon. You already invested over a trillion and you can multiply production if you reinvest a little more. Bagging volatile gas from asteroids/comets does not require sophisticated mining equipment. You may be able to use the same heat source you use for propulsion.
     
  16. Jan 2, 2018 #15

    rbelli1

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    That depends strongly what portion of the $1T is intended for Mars launch. It is a fair assumption that the lunar infrastructure would be useful for other endeavors.

    BoB
     
  17. Jan 2, 2018 #16

    stefan r

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    We can still do some calculations. Earth surface to earth escape has a delta V of about 12.2 km/s. Lunar surface to earth escape has delta-v around 2.6 km/s.

    We could ball park estimate the cost change by cutting the boost to low earth orbit. Suppose half of the mass launched to Mars comes from Luna and half from Earth. How much mass launched to LEO would cost $2 x1012? The money put into the Mars program would need to be larger. SpaceX is hoping to send 106 colonists to Mars for $5 x 105

    I believe we could extract O2 from the moon for much less than $106.
     
  18. Jan 2, 2018 #17

    russ_watters

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    Since it's my scenario, let's say all of it. If you want to build a luxury hotel or low-g hospice center, spend your own trillion dollars.
    I don't actually believe that, particularly since there is virtually no overlap at all between this refueling station idea and any other lunar base purpose. But either way it doesn't have any impact on my scenario, since ridiculously expensive, infeasible and pointless divided by 2 is pretty much still ridiculously expensive, infeasible and pointless.

    I'm at least as entitled to play Star Trek Pessimist (if not moreso) as others are to play Star Trek Optimist considering I'm reflecting on the reality of why none of this stuff, which is technically possible(except for the Star Trek Propulsion Fantasy), has happened yet. There's a pretty obvious reason for it!
     
  19. Jan 2, 2018 #18

    russ_watters

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    What this is telling us is that 80% of the energy required to escape earth has to come from Earth. In other words, there isn't much benefit to launching from the moon unless we're building the spacecraft on the moon too.
    Elon Musk is rich, but that doesn't make his "hope" impress me. I'm convinced he's going to crash and burn.
    So can I, but not enough to launch a spaceship! All kidding aside, unless I'm misreading, you're saying you can extract O2 from the moon for a million dollars and put colonists on Mars for $500,000 (each?). Please tell me these were typos, because they are far beyond fantasy.
     
  20. Jan 3, 2018 #19
    All politics aside (this is a physics forum, remember?), if a manned-mission to Mars is the objective, would not building a facility in low-Earth orbit where astronauts still have some protection from solar and cosmic radiation be more practical and cost effective?

    We do not have to go all the way to the moon to assemble, fuel, and equip a spacecraft for a manned-mission to Mars. Some sort of spacecraft construction facility in low-Earth orbit would seem to be the most practical and cost effective means of constructing and sending a spacecraft to Mars. Upon its return the spacecraft could dock with the space port and be used for future manned-missions. The astronauts could return to Earth like they do now from the ISS. Perhaps the ISS could be re-tasked for such a purpose, with more modules added as required.
     
  21. Jan 3, 2018 #20

    PeroK

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    Have you signed up then?
     
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