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I Moon vs Earth for launch to Mars

  1. Jan 3, 2018 #21

    stefan r

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    I am not seeing how you put that together from anything I wrote. You suggested $1 trillion.

    There are many versions of experiments demonstrating oxygen extraction from moon rock. Here is one article.
    At 10W/kg you need 450 kg of solar panels. Proof of concept would be to launch a little bit of oxygen from the moon. That should be closer to the billion dollar price range, less if it is attached to some other project. Producing a 8.6 x 109 kg of LOx and launching it would require a lot of infrastructure. Oxygen needs to be delivered to L1 for around than $10 per kg.

    Where are the parts, fuel, and equipment coming from? If all of it comes from Earth then why not launch an assembled ship?

    The plan according to spacex is to refuel the spacecraft while orbiting earth. For one trip to Mars there will be around 8 launches of the BFR. 1 launch for the spacecraft and 5 fuel launches. The BFR to mars uses 1100 tons of propellant (CH4, O2), 250 tons cargo(150 tons reusable), 85 tons spaceship. The propellant is 78% oxygen. There is no reason we could not break that down into 1 spacecraft, 1 methane launch, 1 mixed fuel, and 5 oxygen deliveries. If you have Oxygen in space it can easily cut out half of the launches to LEO.

    If you are going to Mars you need to have well developed radiation shields that do not depend on Earth. On the moon shielding is easy. Pile lunar regolith on top of the habitat modules, build with heavy masonry, or live underground.

    Earth's magnetic field does not protect against x-rays, gamma rays, meteoroids, or neutral particles.
     
  2. Jan 3, 2018 #22

    Al_

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  3. Jan 3, 2018 #23
    The same place where they would originate if we built a moon base. It isn't like we are going to start building manufacturing facilities on the moon. We are going to build everything we need on Earth and then send it into space. The whole idea behind having a space construction facility is so we can make numerous trips into LEO in order to construct this craft over a period of time. We do not have to construct everything on the surface of Earth and go (like we have been), and we don't need to do that on the moon either.

    SpaceX's plan makes a lot of sense. That is a lot of launches.

    You are right about the radiation shielding. It is the primary reason we have not had a manned-mission beyond LEO since 1973. According to the Curiosity probe, it registered ~300 millisieverts (3,000 millirems) of radiation on the trip to Mars.

    Dartmouth College has some interesting ideas with regard to radiation shielding for spacecraft and NASA published a technical report on the subject several years ago. We should not even be contemplating a manned-mission to Mars until we can ensure at least minimal protection against solar and cosmic radiation. I mean the purpose of the mission is to bring the astronauts home alive, right?

    Sources:
    Spacecraft Shielding - Thayer School of Engineering, Dartmouth College
    Revolutionary Concepts of Radiation Shielding for Human Exploration of Space - NASA Technical Report, March 1, 2005
     
  4. Jan 3, 2018 #24

    russ_watters

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    $10^6 is a million dollars. I'm asking you if That's a typo or if you really think it is possible to mine and process any amount of fuel on the moon for a million dollars.
    Yes. I think you number - if it wasn't a typo - is off by itself squared.
     
  5. Jan 3, 2018 #25

    stefan r

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    Modern concrete:
    4.5/65 = 6.9%

    So dry concrete on a hot summer day has about an order of magnitude more water than the "wet" parts of the moon.
     
  6. Jan 3, 2018 #26

    Al_

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    Well, for many years after the Apollo program, we thought the Moon was as dry as a dinosaur bone in a dessicator.
    Maybe ten years have passed since we learned differently, and many private and govt projects are in the pipeline.
    So give it time! I think we'll see some Lunar activity pretty soon!
     
  7. Jan 3, 2018 #27

    Al_

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    Yes, but it's bound chemically. You can't just melt or separate it out.
     
  8. Jan 3, 2018 #28

    russ_watters

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    1. It is a stretch to say these projects are "in the pipeline".
    2. Colonization is not step 1, exploration is. You're suggesting building a massive and absurdly expensive infrastructure to support a need that doesn't exist and can't exist until after the exploration.
     
  9. Jan 3, 2018 #29

    stefan r

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    Elon Musk is suggesting a colony of 1 million colonists. If you spend on $billion on anything then it is $1000 per person or $100,000 per flight. A $1 trillion infrastructure on the moon that has no purpose other than launching colonists to Mars would cost $1 million per passenger if we assume Musk's plans. What I meant in post #16 was that you could get oxygen for lower prices per passenger.
     
  10. Jan 3, 2018 #30

    PeroK

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    You haven't said whether you are signed up yet. Do you personally fancy a life on Mars?
     
  11. Jan 3, 2018 #31

    Al_

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    There are lots of news reports, from many countries. Not just the US. The EU, China, Japan, etc.
    http://www.newsweek.com/china-plans-far-side-moon-landing-2018-world-first-768519

    It's the least cost route to the outer solar system. Sooner or later someone is going to take that route.
    Maybe they will overtake some others who took a less efficient route?
     
  12. Jan 3, 2018 #32

    stefan r

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    Lunar Prospector was using neutron spectroscopy. It detected neutrons slowed down by Hydrogen ions. Do you have any reason to believe Lunar Prospector would get a different result passing over modern concrete. Is there some reason to believe that water molecules are not bound.

    You can heat portland cement and get water and CO2 out. Not really "melting" it is "thermal decomposition".
     
  13. Jan 3, 2018 #33

    russ_watters

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    Got it; you meant you could get the fuel from the moon for $1 million per passenger. You left out the "per passenger" part! And that exactly bridges the gap between your million and my trillion.
     
  14. Jan 3, 2018 #34

    Al_

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    I don't understand this. I'm answering the question of how best to get to Mars, and mentioning the outer solar system as well.

    Btw, I agree with some of the posts that launch from orbit or a lagrange point is better than either Moon or Earth - rocket assembly and fueling there too.
    Robots that do this can be controlled from Earth, or semi-autonomous.
    Colonisation of the Moon is not needed for this. Just robotic mining.

    But - why go to Mars when you could find all the resources you want in low-g places like asteroids and small moons, and transport them much more easily from there. IMHO Mars is a dead-end gravity well!
     
  15. Jan 3, 2018 #35

    Al_

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    I refer you to the reference in my previous post.
     
  16. Jan 3, 2018 #36

    russ_watters

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    That's a little lunar research "plan". It doesnt have anything to do with the subject of the thred other than having the word "moon" in it.
    Says who? We haven't even done lunar mining much less human travel to the outer solar system; there is no way to accurately make that judgement.
    So let's build a trillion dollar fuel depot now in hopes they do it sooner?
    So, let's build a trillion dollar fuel depot, because "maybe"? C'mon. I'm having trouble believing you are serious.
     
  17. Jan 3, 2018 #37

    russ_watters

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    Yes. The question is an open-ended "what benefits are there of launching from the moon?", which unfortunately has instigated Star Trek style fantasies about such benefits. That's a problem for the longevity of this thread. Even open ended questions have to have discussions constrained to reality.
     
  18. Jan 3, 2018 #38

    Al_

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    Do you think it will cost a trillion? That seems high, when considering other robotic missions.
     
  19. Jan 3, 2018 #39

    stefan r

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    I do not have $500,000. I have strong aversions to becoming an indentured servant. I'm not sure how rational that is. I have to work here anyway and I like working. The illusion of freedom has some appeal. They need to establish a legal framework and clarify bankruptcy law.

    Habitats in space might allow greater freedom of motion. Going out for a walk on Mars would still be inside of a bubble. I do not believe there is a long term motive to set up a Mars colony.

    Working in a high technology green house does have a lot of appeal. Would have repetitive aspects that are "boring" but probably much less so than typical days in the last 5 years.

    I am married to someone who is afraid when we travel by airplanes, will not ride roller coasters, and does not want to move out of the Northeastern USA because she wants to be close to her family. That complicates any plans to leave Earth. If I was married to someone interested in going I would sign up.
     
  20. Jan 3, 2018 #40

    Al_

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    Fair enough, I should have been more cautious.
    How about this: It seems to me that getting fuel from the Moon is a smarter way to proceed, and the problems of mining seem soluble.
     
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