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Thread: Could the LEM return to Earth orbit from the Moon surface?

  1. #1
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    Could the LEM return to Earth orbit from the Moon surface?

    A theoretical question: could the descent stage Grumman engine of a fully fueled LEM have enough power to be able to take off from the lunar surface, break away from its gravity, and be able to get its two astronauts in to Earth orbit, if necessary separating and using as well the Bell engine of the Ascent Stage?

  2. #2
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    Quote Originally Posted by wd40 View Post
    A theoretical question: could the descent stage Grumman engine of a fully fueled LEM have enough power to be able to take off from the lunar surface, break away from its gravity, and be able to get its two astronauts in to Earth orbit, if necessary separating and using as well the Bell engine of the Ascent Stage?
    Yes. But not LEO.

    Combined delta-V of LM descent and ascent engines ~ 4.7km/s
    Delta-v from lunar surface to GEO ~ 4.7km/s
    Delta-v from lunar surface to LEO ~ 5.7km/s

    (Sources differ, and to some extent that's because the orbital inclinations, and LEO altitude, are unspecified.)

    Grant Hutchison
    Last edited by grant hutchison; 2019-Aug-29 at 10:17 PM. Reason: brackets

  3. #3
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    The lander from MOON ZERO TWO almost looks capable--were it real
    http://www.davidsissonmodels.co.uk/M...20Part%201.htm

  4. #4
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    Quote Originally Posted by publiusr View Post
    The lander from MOON ZERO TWO almost looks capable--were it real
    Not the topic of this thread.
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  5. #5
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    I was wondering if a stretch LEM could be viable....

  6. #6
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    If you can aerobrake at Earth, you only need something like 2.7km/s to reach Earth from the surface of the Moon. (I'm speaking from memory of a calculation I once did for a science fiction story I never sold.) The LM is not a good aerodynamic way to shed 12km/s, unfortunately.

    Grant Hutchison

  7. #7
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    You would likely shed 12 km/s and most of the LEM's structure as well.
    With sufficient thrust, water towers fly just fine.

  8. #8
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    But not taking a huge heat-shield could save some on weight. It wouldn't be how I might go.

    Imagine a stretch LEM, launched atop a rocket with two small MOOSE/bailout blisters to either side--not much more than ejection seats--no need for a huge escape tower.

    Hydrogen upper stage gets you there--acts as a crasher.

    The LEM lands, and you return to Earth. There, you dock with a craft that does have a heat-shield. The LEM is left in a looping orbit--to be refueled and sent back.

    EOR--but coming back.

    That save you any on mass?

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