posted 09-02-2018 10:40 PM
I was reading my Apogee books copy of the Gemini 12 mission report again, and I noticed on the countdown timeline there is listed an OAMS (Orbit Attitude and Maneuvering System) test at T-20 minutes.
Was this done on all flights? It seems strange to me that this was done.
David C Member
Posts: 1039 From: Lausanne Registered: Apr 2012
posted 09-03-2018 05:12 AM
Yes it was. If you think of the analogy with airplane flying, seems like a good idea to test your controls before committing. Of course there were other considerations on later spacecraft. The Gemini III transcript (bottom of page 4, top of 5) is a good example.
space1 Member
Posts: 861 From: Danville, Ohio Registered: Dec 2002
posted 09-03-2018 06:30 AM
Originally I thought these tests were started with Gemini IX as a result of the Gemini VIII thruster problem. But apparently they were done on all Gemini launches.
However, in the case of Gemini III the Reentry Control System (RCS) thrusters were also tested. Normally the RCS would not be activated until shortly before reentry to ensure integrity of the system regarding pressure or propellant leaks. But with Gemini III being such a short mission it was safe to test these thrusters before launch.
Headshot Member
Posts: 891 From: Vancouver, WA, USA Registered: Feb 2012
posted 09-03-2018 08:39 AM
I distinctly recall seeing the puffs of smoke around the Gemini spacecraft adapter section when the thrusters were being fired for this test during television coverage of several launches. If the wind was "strong," they dissipated very quickly and were hard to see.
posted 09-04-2018 06:31 PM
Thanks for the info. It's amazing how much more there is to learn about our past missions. I watched several Gemini launches as a boy but I certainly wasn't looking for an OAMS test.
Space Cadet Carl Member
Posts: 225 From: Lake Orion, Michigan Registered: Feb 2006
posted 09-05-2018 10:52 AM
Fascinating. I was fortunate to have a color console television to watch all the Gemini flights in '65 and '66. Don't recall seeing any thruster tests happening in the final minutes before launch, but I really wasn't looking for it either.
LM-12 Member
Posts: 3324 From: Ontario, Canada Registered: Oct 2010
posted 09-05-2018 12:01 PM
Somewhat related: the RCS thrusters on the LM were tested (hot-fired) before lunar liftoff. The RCS test on Intrepid (Apollo 12) knocked over the S-band antenna that was deployed on the lunar surface.
Similarly, the S-band antenna blew over on Apollo 14 after that RCS test.
ManInSpace Member
Posts: 134 From: Brooklin, ON Canada Registered: Feb 2018
posted 09-05-2018 03:27 PM
Like many of you, I grew up in the Gemini/Apollo era; but was unaware of the pre-launch thruster tests.
My thanks to all the posters on this issue and also to LM-12 for the RCS information, another procedure that I wasn't aware of.
tlifan2 Member
Posts: 49 From: Palm Coast, Florida Registered: Feb 2014
posted 09-05-2018 06:54 PM
If you look at the following video of Gemini V starting at 3:55, you can see what I think is the OAMS thruster testing. See if you agree. (Ignore the audio).
moorouge Member
Posts: 2458 From: U.K. Registered: Jul 2009
posted 09-06-2018 12:17 AM
Is this it -
space1 Member
Posts: 861 From: Danville, Ohio Registered: Dec 2002
posted 09-06-2018 09:00 AM
Thanks for the video. I do recall the testing of the LM's RCS on the moon.
Headshot Member
Posts: 891 From: Vancouver, WA, USA Registered: Feb 2012
posted 09-06-2018 10:02 AM
That sure looks like the OAMS testing (if that is indeed what it is) that I recall, but in this case (Gemini V) it is much more visible than what I remember. I believe the visibility of the puffs depended on wind speed, lighting conditions and camera angle (having that red umbilical tower behind the puffs helped provide contrast). Good job in locating that video.
LM-12 Member
Posts: 3324 From: Ontario, Canada Registered: Oct 2010
posted 09-06-2018 11:12 AM
Here is some 16mm footage taken of the LM liftoff on Apollo 14. Look closely at the first few seconds. In the first scene, you see the S-band antenna shadow. In the second scene, you don't. The RCS test must have taken place between the two scenes. Notice also how the flag has moved.
LM-12 Member
Posts: 3324 From: Ontario, Canada Registered: Oct 2010
posted 10-04-2018 11:00 PM
There is this entry in Volume IV of "The Apollo Spacecraft - A Chronology" for October 28, 1968:
MSC Apollo Spacecraft Program Office Manager George M. Low deleted the requirement for a short static-firing of the Apollo 8 service module reaction control system on the pad before launch (the so-called "burp" firing). He took this move in line with a recommendation from NASA Apollo Program Director Samuel C. Phillips and in light of the nominal performance of the RCS during the Apollo 7 flight. By thus eliminating the burp firings — and not allowing any contact of the system's hypergolic propellants — the spacecraft could be maintained in a loaded condition through the December and January launch windows and gain the maximum launch flexibility for the Apollo 8 flight. (Decisions not to static-fire the RCS systems on spacecraft following 103 had been made some time earlier.)
LM-12 Member
Posts: 3324 From: Ontario, Canada Registered: Oct 2010
posted 11-12-2018 02:41 PM
The Apollo 7 Press Kit has a "spacecraft RCS static fire" test at T-20 minutes in the countdown events. From the PAO transcript:
This is Apollo Saturn Launch Control at T-21 minutes and counting. T-21, at this time the commander of the Apollo 7 Spacecraft, Wally Schirra, has gone through a series of checks with the reaction control system on the Apollo 7 Spacecraft. We have a total of some 16 reaction control system engines on the service module of the Apollo 7. They're located in four quadrants around the service module and each of the engines is capable of generating some 100 lbs. of thrust. Astronaut Schirra fired these thrusters and the report from the Spacecraft Test Conductor is the static firing went very well. We actually did fire several of the thrusters during this test and the report was that the test went well. In the meantime we completed some final checks of the range safety destruct system aboard the Saturn lB launch vehicle. These are checks between the launch crew and the Air Force Eastern Test Range. Those checks also went very well, and the count is continuing. We have just passed the 20 minute mark. We are now at T-19 minutes, 54 seconds and counting. This is Launch Control.
posted 09-02-2018 10:40 PM
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