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  Mercury - Gemini - Apollo
  Apollo SPS engine use SPS outside lunar orbit

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Author Topic:   Apollo SPS engine use SPS outside lunar orbit
rasorenson
Member

Posts: 78
From: Santa Clara, CA, USA
Registered: Nov 2009

posted 04-22-2012 09:36 PM     Click Here to See the Profile for rasorenson   Click Here to Email rasorenson     Edit/Delete Message   Reply w/Quote
If Apollo 8 had missed it's lunar orbit insertion burn, or if any Apollo ended up in an abnormal orbit, whether lunar or far flung earth orbit, there must have been a set of parameters for the outside capabilities of the service module's SPS engine to make course corrections for a return trajectory.

Wonder how much fuel and ability the Service Propulsion System (SPS) would have had to respond to misguided orbits or trajectories around the moon/earth system?

ilbasso
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Posts: 1494
From: Greensboro, NC USA
Registered: Feb 2006

posted 04-22-2012 10:37 PM     Click Here to See the Profile for ilbasso   Click Here to Email ilbasso     Edit/Delete Message   Reply w/Quote
It must have been a pretty healthy fuel supply, if you can believe what I heard as one of the abort scenarios they were initially considering for Apollo 13. I read somewhere that you could theoretically turn the stack end-forward and fire the SPS to send you back to Earth without looping around the Moon first. I've never seen that procedure formally documented in a NASA publication, though.

The process would be easier at some points in the Earth-Moon trip than others. It would be a lot easier to "turn around" when you were approaching the point where the Moon's and Earth's gravity were in equilibrium than it would be when you were just starting to speed away from Earth at 25,000 mph after the S-IVB shutdown.

Go4Launch
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Posts: 400
From: Bethesda, MD
Registered: Jul 2003

posted 04-22-2012 10:42 PM     Click Here to See the Profile for Go4Launch   Click Here to Email Go4Launch     Edit/Delete Message   Reply w/Quote
That engine had significant capability. Two of them could slow down the shuttle to drop out of orbit. It was also used for a Delta II upper stage.

SpaceAholic
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Posts: 3023
From: Sierra Vista, Arizona
Registered: Nov 1999

posted 04-23-2012 05:39 AM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Go4Launch:
Two of them could slow down the shuttle to drop out of orbit..

A single 21K Pound (97.5KN) AJ10-137 Apollo Service Propulsion Engine produced more thrust then the two shuttle AJ10-190 OMS engines combined. Only one would have been required for de-orbit.

quote:
It was also used for a Delta II upper stage.

The AJ10-118K was used - it was a derivative of the SPS main engine but capable of generating less then half the rated thrust of the Apollo varient (about 9000 pounds).

Go4Launch
Member

Posts: 400
From: Bethesda, MD
Registered: Jul 2003

posted 04-23-2012 09:52 PM     Click Here to See the Profile for Go4Launch   Click Here to Email Go4Launch     Edit/Delete Message   Reply w/Quote
Exactly. Bigger engine than people realize.

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