Posts: 891
From: Vancouver, WA, USA
Registered: Feb 2012

posted 08-03-2018 12:22 PM               

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When a Gemini mission was done, the crew ejected the equipment module which had batteries/fuel cells, propellant and oxygen. Then the retrorockets were fired.

What if the retros did not fire? Were they screwed? After all they just got rid of the lion's share of their life-supporting goodies. The re-entry module life-support supplies had to be minimal, at best.

I do not believe the RCS system on the re-entry module had the capability to de-orbit them. So were they stuck in orbit until their onboard supplies ran out?

Posts: 1624
From: Bethpage, N.Y.
Registered: Jul 2002

Posts: 342
From: Houston, Texas, USA
Registered: Jun 2004

posted 08-04-2018 09:44 AM            

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The possibility of a failure in the Gemini retrorockets became a serious concern to NASA managers after the publication of "Marooned" by Martin Caidin. That story about the failure of retrorockets on a Mercury capsule to fire alarmed NASA about that possibility on Gemini.

Procedures were modified very late before Gemini 3 to deorbit using the thrusters in the equipment module before it was jettisoned, then to fire the retrorockets too. This was done on Gemini 3 and 4. At that point, everyone decided that the retrorockets were reliable enough to depend on, and the two-step deorbit was discontinued.

Posts: 891
From: Vancouver, WA, USA
Registered: Feb 2012

posted 08-04-2018 11:53 AM               

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Thanks John.

I did not realize that Gemini 4 used the two-step de-orbit procedure like Gemini 3.

I seem to recall that the fourth retro-rocket on Gemini 5 fired noticeably late. Do you know if an explanation was ever developed for that?