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I Moon vs Earth for launch to Mars

  1. Jan 6, 2018 #61

    sophiecentaur

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    If people aren't careful, I can see Elon Musk becoming the 21st century version of Nicola Tesla in the minds of the public. I agree that he could very likely crash and burn because a space project would not be important enough or 'too big to fail'. Many of Musk's competitors would just be laughing up their sleeves (or out loud).
     
  2. Jan 6, 2018 #62
    What are you talking about? With his prices and accelerating launch rate, Musk is already killing Proton and ULA. Arianespace is next to the chopping block. What "crash and burn"?
     
  3. Jan 6, 2018 #63

    stefan r

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    I was hoping this thread could include more orbital dynamics. We have samples of rocks that got here from Mars.
    During the late heavy bombardment both the earth and the moon were hit by many asteroids. There must be both terrestrial and lunar meteorites on Mars. Can we estimate the ratio? Most of this happened 3 to 4 billion years ago. It is nice that we are not likely to see a major comet impact in out lifetimes. We can still talk hypothetically about the relative probability of a surface chunk making the trip instead of falling back down.
     
  4. Jan 7, 2018 #64

    sophiecentaur

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    Have they actually launched a Mars Project yet? Crash and burn doesn't only imply a financial fail. How many fails (or lost lives) will regular investors fund? The market doesn't have the same attitude to projects that JFK managed to instil into a whole nation.
     
  5. Jan 7, 2018 #65
    That was not my point. You said "many of Musk's competitors would just be laughing".

    As things go now, there *won't be* "many Musk competitors". At best, a few foreign launch providers will be surviving by subsisting on launching their governments' payloads. In US, NASA and ULA are becoming not viable as launch providers - the price gap is scary. Also, SpaceX success spurred a few private copycats, notably Bezos' Blue Origin looks technically promising (and it is backed by Bezos' $80B!). Even if SpaceX somehow fails, it already have shown the way how to make space much more accessible. Someone else will succeed.
     
  6. Jan 7, 2018 #66

    sophiecentaur

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    You are making the assumption that Space X will actually succeed. Fact is, to most people, it makes little difference whether or not it succeeds and the "competitors" I referred to will not necessarily cease to exist. They may have failed or just withdrawn from the field when they see they are not going to get any immediate returns
     
  7. Jan 7, 2018 #67
    They succeeded (wildly) as a launch provider. And fingers crossed, they may launch their first 64ton-to-LEO Falcon Heavy this month, making their rocket the largest, by the factor of 2.5, operational launcher in the world. For the price of one Ariane-5 launch!

    Cost of launch was the largest obstacle for all of humanity's space efforts, Moon/Mars programs included. SpaceX dramatically lowered that. Now, even if SpaceX magically disappears right this day, it would not matter: now we _know_ how to make launch much cheaper.

    I'm not emotionally attached to SpaceX per se. If someone else builds the Mars base, it's fine with me.
     
  8. Jan 7, 2018 #68

    sophiecentaur

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    I think the big difference between a Launch and an Expedition is who would pay for it. Customers will be queuing up for their satellites to be taken into orbit at a good price. Who is prepared to invest private funds in a project with a totally unknown return? How long term do investors, other than nations, work?
     
  9. Jan 7, 2018 #69

    Chronos

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    Looking at it from a purely physics standpoint, a launch from the moon is much easier than a launch from earth. The escape velocity from the moon is just over 2 km/sec whereas from earth you need over 11 km/sec The problem is in getting all the llaunch resources from earth to the moon. If the raw materials needed are already present on the moon. problem solved. [mostly].
     
  10. Jan 7, 2018 #70

    mfb

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    There are two companies working on this radically better launch technology, and two more are looking into it. Or should I say "landing technology"?
    Reusing rocket components is something we do now. SpaceX recovered the first booster just two years ago, now they have reflown a couple of them, reflown two Dragon spacecraft, and they seem to recover the fairings at least partially. Reusing the full rocket is something we can do in maybe 5-10 years. That is a leap as large as from expendable aircraft to reusable aircraft.
    Exactly: There were never expendable aircraft. No one built them because they would have been ridiculously expensive. With rockets there was a market even for expendable rocket. Imagine how large the market can be if we can use the rockets like airplanes.
    BFR can go to the Moon and back with a lot of in-orbit refueling - with something like 2000-3000 tons of fuel launched from Earth. It can bring back something like 200 tons of payload from the Moon, maybe twice that amount if it gets refueled on the surface. Using that payload for fuel wouldn't make any sense even if we would have free and unlimited tanks on the Moon.


    From LEO you need 4.3 km/s to reach Mars. From the surface of the Moon you need about 3.5 km/s. If you want to mate a rocket from Earth with fuel from the Moon the fuel from the Moon needs 5.7 km/s delta_v just to reach LEO (3.2 of it can be done with aerobraking) and 5.7 km/s more if you want the system back on the Moon for the next trip - for a sum of 8.2 km/s for a Moon<->LEO shuttle. That is nearly what you need from Earth to LEO. And producing 1 ton of oxygen on Earth is much easier than producing it on the Moon. With chemical rockets, as long as you build the rocket on Earth and don't have a lunar space elevator or similar, it makes no sense to bring fuel from the Moon.
    If we consider lunar space elevators, we can also consider concepts like the StarTram which can potentially launch things to space at basically the electricity costs once it runs. If LEO launches are as cheap as an airplane flight, there is no point in a Moon-based propellant production, you just launch more from Earth.
    None of them will cease to exist. The US government wants to have two launch providers, Russia and the EU want to have their own rocket for government satellites. SpaceX will probably get an even larger share of the commercial market.
     
  11. Jan 7, 2018 #71

    stefan r

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    The rendevous in LEO might work poorly. Earth-moon Lagrange 1 looks a lot better. From EML1 it takes 1.2 km/s to reach mars. The launch from lunar surface to EML1 needs 2.5 km/s. Getting to EML 1 from LEO requires 3.8 km/s. So the astronauts, rocket, and luggage (and methane?) lose 0.7 km/s when they make a detour to EML1.
    The worst part would be landing the methane needed to lift oxygen.

    If we go solar the electricity costs are lower on the moon. No clouds or atmosphere to block sunlight. The StarTram itself would work much better on the moon. The magnetic sled does not need to leave the surface so magnetic breaks can recycle the electricity. There is no need for a heat shield. The cargo does not hit an atmosphere. The ship does not have to fit into a tube. A lunar StarTram would not need to be elevated so there is no active support structure. Refrigerating kilometers of niobium-titanium conductor drains a lot of power. I have not seen a suggestion for magnetic launch Earth direct to Mars would likely be thousands of km.

    Anything that makes launch to LEO cheap or easier will also make establishing lunar colonies/depots cheaper or easier.
     
  12. Jan 8, 2018 #72

    sophiecentaur

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    Actually, there were several occasions during WW2 when troops and equipment were landed by (non-reusable) gliders. It made sense at the time, on an Engineering basis. Link.
    There can always be a use for a non-reusable craft.
     
  13. Jan 8, 2018 #73

    Al_

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    Interestingly, Deimos has a 30hr rotation. This means that people and plants might be able to adapt to the day-night cycle.
    Plenty of dust for shielding. A spacecraft that rotates for simulated gravity on the journey to Deimos would be able to continue rotating there, even with added shielding. Super low gravity means takeoff might be possible even with ion drives! Possibility that the interior contains water ice, and the low-g makes digging easier. From Diemos, it would be possible to control robots exploring the surface of Mars in real-time, virtual realty style.
     
  14. Jan 8, 2018 #74

    Al_

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    I think not. Elon Musk seems much more hard-headed than Tesla. His degree, if I recall, was Economics and Physics.
     
  15. Jan 8, 2018 #75

    Vanadium 50

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    That's not setting the bar all that high.
     
  16. Jan 8, 2018 #76

    sophiecentaur

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    I wasn't comparing the men so much as comparing the public reaction to them. I reckon Musk would stand every chance of the post of POTUS and would have members of both parties vote for him.
     
  17. Jan 8, 2018 #77

    Al_

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    Nice video!
    But, it looks like all the materials have to be launched from Earth. That's a lotta launches, and a load of money, even at Musk prices.
    It mentions using extraterrestrial materials, but only after the gateway is built.
    I think if we put 5% of the effort into Lunar mining, we'd reduce the costs of this station greatly.
    Then, once it's built, with Lunar materials and robots controlled from Earth by virtual reality telemetry, this would be a great construction location and launch location for any Mars mission or further out. Although, as said, the Lagrange points might make more sense in terms of delta-V
     
    Last edited: Jan 8, 2018
  18. Jan 8, 2018 #78

    Al_

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    Can't wait to see prospecting on the Moon. What if there are Lunar hydrocarbon deposits? Well, why not, there are primordial hydrocarbons on Earth?
    Looks like there are - https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1425.pdf
    And if not, well, we can use a H2 / O2 rocket.
     
  19. Jan 8, 2018 #79

    sophiecentaur

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    Very different from prospecting (and refining) on Earth. Getting there could be a minor problem, in comparison I think.
     
  20. Jan 8, 2018 #80

    mfb

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    They lose 0.5 km/s when they are nearly there. You need about 9 km/s to go to LEO and 3.8 km/s more to go to EML 1. At that point you are nearly at TMI already. Refueling at EML saves your rocket the last 0.7 km/s only.
    Installation costs are orders of magnitude higher. Yes, that is a plural.
    The same applies to all fixed launch installations.
     
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