Exploring the Unknown: Selected Documents in ... - The Black Vault

Exploring the Unknown
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It was perhaps the flight of Gemini VIII in the spring of 1966 that demonstrated
more clearly than any other mission the capability of the program to accomplish
rendezvous and docking in orbit. Gemini VIII had two major objectives, but was
able to complete only one of them. The first objective involved completing the
first ever on-orbit rendezvous and docking. Second, the crew was to accomplish
an extended EVA. After launch on 16 March 1966, the crew of Neil Armstrong
and David Scott approached their Agena target vehicle without difficulty. The
crew then docked with it as had been planned. While undertaking maneuvers
when attached to the Agena, the crew of Gemini VIII noticed that for some unexplained
reason the spacecraft was in a roll. Armstrong used the Gemini’s orbital
maneuvering system to stop the roll, but the moment he stopped using the thrusters,
it started again. They then turned off the Agena and this seemed to stop the
problem for a few minutes. Then suddenly it started again. Scott then realized
that the problem was with the Gemini capsule rather than the Agena. After transferring
control of the Agena back to the ground, they undocked and with a long
burst of translation thrusters moved away from the Agena. At that point, Gemini
VIII began to roll about one revolution per second. They decided to turn off
the orbital maneuvering system and try to regain control of the spacecraft with
its reentry control system. If they failed to do so the accelerating rotation would
eventually cause the crew to black out and for the mission to the lost, perhaps
with loss of life. Even so, the use of the reentry control system would require
Armstrong and Scott to return to Earth as soon as possible so as not endanger
the mission any further. After steadying the spacecraft they tested each thruster
in turn and found that Number 8 had stuck on. This had caused the roll. The
mission then returned to Earth one orbit later so that it could land in a place that
could be reached by the Navy.
There was no question that astronauts Armstrong and Scott had salvaged the
mission, even if they did have to return to Earth earlier than expected. A review
of the incident found no conclusive reason for the thruster sticking as it did.
But it was obvious that the crew’s presence allowed the diagnosis of the anomaly.
Reviewers believed it was probably caused by an electrical short that caused a
static electricity discharge. Even if the switch to the thruster was off, power could
still flow to it. To prevent reoccurrence of this problem, NASA changed the system
so that each thruster could be isolated (I-70). 148
of the Symposium on Space Rendezvous, Rescue, and Recovery, Volume 16, Part 2, American Astronautical
Society, Edwards Air Force Base, CA, 10–12 September 1963, pp. 173–176.
148. “Gemini VIII Technical Debriefing,” 21 March 1966. Folder 18674, NASA Historical
Reference Collection, NASA History Division, NASA Headquarters, Washington, DC; S.R.
Mohler, A.E. Nicogossian, P.D. McCormack, and S.R. Mohler Jr., “Tumbling and Spaceflight:
The Gemini VIII Experience,” Aviation and Space Environmental Medicine 61 (January 1990):
pp. 62–66; Bo J. Naasz, “Classical Element Feedback Control for Spacecraft Orbital Maneuvers,” M.S.
thesis, Virginia Polytechnic Institute and State University, Blacksburg, VA, 2002, pp. 1–2; M. E. Polites,
An Assessment of the Technology of Automated Rendezvous and Capture in Space (Huntsville, AL: NASA/
TP—1998–208528, 1998), pp. 3–9; H. J. Ballard, “Agena Target Vehicle for Gemini,” Proceedings of
the Symposium on Space Rendezvous, Rescue, and Recovery, Volume 16, Part 2, American Astronautical
Society, Edwards Air Force Base, CA, 10–12 September 1963, pp. 177–187.