Apollo Discussions > The Reality of Apollo

Ascent module acceleration

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Peter B:
It's just occurred to me that the acceleration of the LM ascent stage at lift-off was a little over 2G, and this would have increased as propellant was burned.

Seeing as the astronauts were standing during launch, was any testing performed (for example in a centrifuge) to confirm that the crews could continue to stand and operate controls during launch?

Thank you!

JayUtah:
How are you getting 2 g acceleration at liftoff? The limiting case is nominal thrust applied to dry mass. 15.600 kN thrust against 2400 kg dry mass is approximately 6.5 m s-2 for a maximum of about 0.66 g.

Peter B:

--- Quote from: JayUtah on January 10, 2025, 11:03:24 AM ---How are you getting 2 g acceleration at liftoff? The limiting case is nominal thrust applied to dry mass. 15.600 kN thrust against 2400 kg dry mass is approximately 6.5 m s-2 for a maximum of about 0.66 g.

--- End quote ---

I thought it was as simple as dividing engine thrust (3500 lbf) by the ascent stage's gross weight in lunar gravity (10,300 pounds / 6).

I think I'm about to learn how wrong I am...   :D

bknight:
Think dimensional units a is l/t^2, v is l/t, and s =l.  Good start

PDI-11:

--- Quote from: Peter B on January 11, 2025, 04:31:59 PM ---I thought it was as simple as dividing engine thrust (3500 lbf) by the ascent stage's gross weight in lunar gravity (10,300 pounds / 6).

I think I'm about to learn how wrong I am...   :D

--- End quote ---

10,300 pounds is the weight on Earth. Mass = weight/gravity, so mass = 10,300 lb/(32.2 ft/sec^2) = 320 lb*sec^2/ft. (If I remember correctly, that would be 320 slugs, but call it whatever you want as long as the units are consistent.  :) )

Since F=m*a, a=F/m = 3500 lb/(320 lb*sec^2/ft) = 10.9 ft/sec^2. In G's, that is 10.9 ft/sec^2/(32.2 ft/sec^2) = 0.34 G's.

Ironically, that is about 2 Moon G's, but we want to know the Earth G's.

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