Gemini 8

Gemini 8 (officially Gemini VIII) was the sixth manned spaceflight in NASA's Gemini program. The mission conducted the first docking of two spacecraft in orbit, but suffered the first critical in-space system failure of a U.S. spacecraft which threatened the lives of the astronauts and required immediate abort of the mission. The crew was returned to Earth safely. The only other time this happened was on the flight of Apollo 13.

It was the twelfth manned American flight and the twenty-second manned spaceflight of all time (including X-15 flights over 100 kilometres (62 mi)). Command pilot Neil Armstrong's flight marked the second time a U.S. civilian flew into space (Joseph Albert Walker became the first US civilian on X-15 Flight 90^[1][2]). Armstrong had retired from the United States Navy in 1960. The Soviet Union had launched the first civilian, Valentina Tereshkova (also the first woman) aboard Vostok 6 on June 16, 1963.^[3]

Crew

Backup crew

Mission parameters

• Mass: 3,789 kilograms (8,350 lb)
• Perigee: 159.9 kilometres (99.4 mi)
• Apogee: 271.9 kilometres (169.0 mi)
• Inclination: 28.91°
• Period: 88.83 min

Agena docking

March 16, 1966

• Docked: 22:14 UTC
• Undocked: ~22:45 UTC

Objectives

Gemini VIII had two major objectives, of which it achieved one. The two objectives were:

• accomplish an in-orbit rendezvous and docking, and
• accomplish an extended extra-vehicular Activity.

Flight

Agena

It was five months since NASA had tried to launch an Agena and Gemini. This time everything worked perfectly. The Agena put itself into a 298-kilometer circular orbit and oriented itself to the correct attitude for the docking. The Gemini spacecraft itself was put into a 160 by 272 kilometer orbit by its modified Titan II ICBM.

Rendezvous and docking

Their first burn was at 1 hour and 34 minutes into the mission, when they lowered their apogee with a 5 second burn. The second burn was at apogee of the second orbit. This time they raised their perigee by adding 15 meters per second to their speed. Their third burn made sure that they were in the same orbital plane. This time they were turned 90° from their direction of travel and made a burn of 8 meters per second while they were over the Pacific. They then had to make an 0.8 meter per second burn after the ground controller realised that they were slightly off due to problems with the thrusters not shutting off properly.

They found that at 332 kilometres (206 mi) from the Agena that the radar had acquired the target. At 3 hours, 48 minutes and 10 seconds into the mission they performed another burn that put them in a circular orbit 28 kilometres (17 mi) below the Agena. They first sighted it when they were 140 kilometres (87 mi) away and at 102 kilometres (63 mi) they turned the computer onto automatic.

After several small burns they were 46 meters away and with no relative velocity. After 30 minutes of visually inspecting the Agena to make sure that it had not been damaged by the launch, they were given the go for docking. Armstrong started slowly (8 centimeters per second) to move towards the Agena. In a matter of minutes, the Agena's docking latches clicked and a green light indicated that the docking had been successfully completed. "Flight, we are docked! Yes, it's really a smoothie," Armstrong radioed to the ground.

Emergency

There was some suspicion on the ground that the Agena attitude system was acting up and might not have the correct program stored in it (this suspicion was subsequently found to be incorrect). Just before they went off contact with the ground, the crew of Gemini 8 were informed that if anything strange were to happen, they were to turn off the Agena.

After the Agena began execution of its stored command program, which instructed the Agena to turn the combined spacecraft 90° to the right, Scott noticed that they were in a roll. Armstrong used the Gemini's Orbit Attitude and Maneuvering System (OAMS) to stop the roll, but the moment he stopped using the thrusters, it started again. They immediately turned off the Agena and this seemed to stop the problem for a few minutes. Then suddenly it started again.

Scott noticed that the Gemini attitude fuel had dropped to 30% indicating that it was a problem on their own spacecraft. They would have to undock. 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.

It was at that point that the Gemini spacecraft began to roll even faster, and approached one revolution per second. The astronauts were now in danger of impaired vision and loss of consciousness due to the violent motion. At this point Armstrong shut down the OAMS and used the Re-entry Control System reaction control system (RCS) to stop the spin. After steadying the spacecraft, they tested each OAMS thruster in turn and found that Number 8 had stuck on. Mission rules dictated that the flight be terminated once the RCS had been fired for any reason, so Gemini VIII prepared for an emergency landing.

Landing

It was decided to let the spacecraft reenter one orbit later so that it could land in a place that could be reached by the secondary recovery forces. The original plan was for Gemini 8 to land in the Atlantic, but that was supposed to be three days later. So USS Leonard F. Mason started to steam towards the new landing site 800 kilometers east of Okinawa and 1,000 kilometers south of Yokosuka, Japan.

Most of the reentry occurred over Asia, beyond the range of NASA tracking stations.

Planes were also dispatched and the pilot of one (Captain Les Schneider, USAF), managed to see the spacecraft as it descended precisely on time and target. Three pararescuers jumped from the plane and attached the flotation collar to the capsule. The three pararescuers (Air Force PJs) were A/2C Glenn M. Moore; A/1C Eldridge M. Neal; and S/Sgt Larry D. Huyett.^[4] Three hours after splashdown, the Mason had the spacecraft on board.

Had Gemini 8 landed in the western Atlantic Ocean (the scheduled recovery area) as planned, it would have been recovered by the U.S. Navy Atlantic Recovery Fleet's prime recovery ship, the carrier USS Boxer. During this time the Wasp (the usual Atlantic Fleet Gemini recovery carrier) was in dry dock for repairs.

For several days after the Gemini reentry, the Agena vehicle was tested by a variety of maneuvers instigated by NASA ground control in Houston until its fuel and power were exhausted.

The Gemini 8 mission was supported by the U.S. Department of Defense with 9,655 personnel, 96 aircraft, and 16 ships.

Cause and outcome

No conclusive reason for the thruster malfunction was found. The most probable cause was determined to be an electrical short, most likely due to a static electricity discharge. Power still flowed to the thruster, even when it was switched off. To prevent recurrence of this problem, the system was changed to allow isolation of each thruster.

The Deputy Administrator of NASA, Dr. Robert Seamans, was attending a celebratory dinner sponsored by the Goddard Space Flight Center, at which Vice President Hubert Humphrey was the guest speaker, when the problem arose.^[5] The incident inspired Seamans to review NASA's problem investigation procedures, modeled after military crash investigations, and on April 14, 1966, to formalize a new procedure in Management Instruction 8621.1, Mission Failure Investigation Policy And Procedures. This gave the Deputy Administrator the option of performing independent investigations of "major failures", beyond those failure investigations for which the various Program Office officials were normally responsible. It declared: "It is NASA policy to investigate and document the causes of all major mission failures which occur in the conduct of its space and aeronautical activities and to take appropriate corrective actions as a result of the findings and recommendations."^[6] Seamans first invoked this new procedure immediately following the fatal Apollo 1 spacecraft fire on January 27, 1967. It was also invoked after the next critical in-flight failure, which occurred on the Apollo 13 lunar mission in April 1970.

McDonnell Aircraft Corporation, the Gemini spacecraft prime contractor, also changed its procedures. Prior to the accident, McDonnell's top engineers would be at Cape Kennedy for the launch, then fly to Mission Control in Houston, Texas for the rest of the mission. The problem occurred while they were en route, so it was decided to keep engineers in Houston starting at launch.^[7]

Insignia

The flight patch for the mission shows the whole spectrum of objectives that were hoped to have been accomplished on Gemini 8. The text at the bottom is composed of the zodiacal symbol for Gemini, , and the Roman numeral for eight, VIII. The two stars are Castor and Pollux, which are in the constellation of Gemini, and are refracted through a prism to provide the spectrum. Armstrong and Scott both designed the flight patch.

Spacecraft location

The spacecraft is on display at the Neil Armstrong Air and Space Museum, Wapakoneta, Ohio.

See also

• Agena Target Vehicle
• Splashdown

References

External links

• NASA Gemini 8 press kit - Mar 11, 1966
• On The Shoulders of Titans: A History of Project Gemini: http://www.hq.nasa.gov/office/pao/History/SP-4203/cover.htm
• A site about the U.S.S. Leonard F. Mason (DD-852) http://www.west.net/~ke6jqp/dd852.htm
• U.S. Space Objects Registry http://usspaceobjectsregistry.state.gov/search/index.cfm
• Gemini 8 Docks with Agena Video
• "Gemini 8, This is Houston Flight" NASA Documentary: http://www.youtube.com/watch?v=fmD73uyNxvY