NASA's Lunar Escape System (LESS)

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jqavins

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To this armchair rocket design quarterback, it doesn't look realistic.
  • Sure, lunar gravity is only 1/6 of a gee, and yes, there's no drag. But still, could a booster small enough that we don't see it in the video possibly get two guys in space suits up to the CSM's altitude? I doubt it. And match the CSM's orbital speed? I very much doubt it.
  • What about attitude control and guidance?
  • Does the CSM have any EVA capability? It's not like picking up a hitchhiker.
 

CalebJ

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To this armchair rocket design quarterback, it doesn't look realistic.
  • Sure, lunar gravity is only 1/6 of a gee, and yes, there's no drag. But still, could a booster small enough that we don't see it in the video possibly get two guys in space suits up to the CSM's altitude? I doubt it. And match the CSM's orbital speed? I very much doubt it.
  • What about attitude control and guidance?
  • Does the CSM have any EVA capability? It's not like picking up a hitchhiker.
Who needs orbital speed when you could design a Fulton recovery system for the vacuum of space? (sarcasm)
 

bad_idea

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To this armchair rocket design quarterback, it doesn't look realistic.
  • Sure, lunar gravity is only 1/6 of a gee, and yes, there's no drag. But still, could a booster small enough that we don't see it in the video possibly get two guys in space suits up to the CSM's altitude? I doubt it. And match the CSM's orbital speed? I very much doubt it.
  • What about attitude control and guidance?
  • Does the CSM have any EVA capability? It's not like picking up a hitchhiker.
Delta V of 1.7km/s without an atmosphere and with only 1/6 of the gravity loss of an Earth launch should make for a fairly small vehicle. It looked fairly realistic to me, even before I found the Wikipedia article, which has some good details: Lunar escape systems. GNC was evidently very stick-and-rudder. The CSM did have EVA capability, BTW, and it was used on at least the last three lunar missions to retrieve experiments from the service module during the ride home.

If I had ever heard of LESS, I'd long forgotten about it. Thanks @lakeroadster for mentioning it! I'm glad it was never used, but I'm kind of sad it was never built or tested.
 

Blast it Tom!

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( I started this and then had to take my father-in-law to the hospital. I'm on my phone, so my apologies if this has become old news.)

Well, the CSM certainly had EVA capability, especially on the last 3 missions where it was required to retrieve a film magazine from a mapping camera in the service module. And there was a rescue orbit capability for the CSM as well. But yeah, it seems to me that unless one of those globes held life support, they'd either suffocate or bake before the could get to the CSM. Those takeoffs obviously had to be timed pretty close!
 

jqavins

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I'm still having trouble with the motor size. I haven't done any calculation myself, but assuming bad_idea has a source and/or calculated it right (and I have no reason to suppose otherwise)...
Delta V of 1.7km/s without an atmosphere and with only 1/6 of the gravity loss of an Earth launch should make for a fairly small vehicle.
No, supposing that each astronaut masses 100 kg including his suit, and the LESS itself masses another 100 kg (which feels low) that means it needs total impulse of 1.7 km/s × 300 kg = 510,000 Ns, which is a middling S motor. Of course theses are not solid fuel motors, and one of the proposals was to have as many as eight ACS thrusters. But still, the available impulse depends mainly on the amount of fuel available. I just don't see enough volume there for an S motor's worth of fuel.

Is the 1.7 km/s figure based on the in-orbit specific energy, or the substantially greater figure from the Tsiolkovsky equation?
 

bad_idea

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I haven't done any calculation myself, but assuming bad_idea has a source and/or calculated it right (and I have no reason to suppose otherwise)...
You give me too much credit. :)
Is the 1.7 km/s figure based on the in-orbit specific energy, or the substantially greater figure from the Tsiolkovsky equation?
Found in one of several charts of delta V from surface to orbit of various bodies. Could well be wrong or misinterpreted on my part.
 

GlenP

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Blast it Tom!

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I'll crank some numbers a little later. Also...
I hope he's OK.
Thanks; we don't know how much longer he has, but if they can't get his heart back into rhythm the prognosis is not good. And they can't shock him for fear of knocking a clot loose, which my daughter tells me is due to turbulence around the valves due to the afib, which is short for something I have to google.
 

Sandy H.

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Praying for you and your family.

Sandy.
 

Blast it Tom!

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Thanks, Sandy. If he makes it, they'll celebrate their 25th anniversary next months. Both of their spouses had passed away some time before. He was 92 last April.
 
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