Gemini VIII docks with its Agena Target Vehicle
|Mission type||Docking test|
|Mission duration||10 hours, 41 minutes, 26 seconds|
|Distance travelled||293,206 kilometers (158,319 nautical miles)|
|Launch mass||3,789 kilograms (8,353 lb)|
|Members||Neil A. Armstrong
David R. Scott
|Start of mission|
|Launch date||March 16, 1966, 16:41:02UTC|
|Rocket||Titan II GLV, s/n 62-12563|
|Launch site||Cape Canaveral LC-19|
|End of mission|
|Landing date||March 17, 1966, 03:22:28UTC|
|Regime||Low Earth orbit|
|Perigee||261 kilometers (141 nmi)|
|Apogee||270 kilometers (150 nmi)|
|Epoch||March 16, 1966|
|Docking with GATV-5003|
|Docking date||March 16, 1966, 22:14 UTC|
|Undocking date||March 16, 1966, ~22:45 UTC|
|Time docked||~30 minutes|
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 kilometers (54 nautical miles)). 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). Armstrong had resigned his commission in the United States Naval Reserve in 1960. The Soviet Union had launched the first civilian, Valentina Tereshkova (also the first woman) aboard Vostok 6 on June 16, 1963.
|Command Pilot||Neil A. Armstrong
|Pilot||David R. Scott
|Command Pilot||Charles Conrad, Jr.|
|Pilot||Richard F. Gordon, Jr.|
- Mass: 3,789 kilograms (8,353 lb)
- Perigee (min): 159.8 kilometers (86.3 nautical miles)
- Apogee (max): 298.7 kilometers (161.3 nautical miles)
- Inclination: 28.91°
- Period: 88.83 min
March 16, 1966
- Docked: 22:14 UTC
- Undocked: ~22:45 UTC
Gemini VIII had two major objectives, of which it achieved one. The two objectives were:
- accomplish a space rendezvous and the first docking with a target vehicle, and
- accomplish an extended extra-vehicular activity.
An emergency condition encountered during the docking resulted in premature use of the reentry control system, after which an immediate landing was required by Gemini safety rules, resulting in cancellation of the planned EVA and other activities.
Agena Target Vehicle
Five months earlier, NASA had tried to launch an Agena Target Vehicle for Gemini 6, but the Atlas-Agena vehicle blew up before reaching orbit, and the Gemini 6 mission was replanned. 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 launched into a 160 by 272 kilometer orbit by a modified Titan II on March 16, 1966 (coincidentally the 40th anniversary of the launch of the world's first liquid-fueled rocket by Dr. Robert H. Goddard), at 10:41:02 a.m. EST.
|Gemini 8 Agena Info|
|Mass||3,175 kilograms (7,000 lb)|
|Launch date||March 16, 1966|
|Launch time||15:00:03 UTC|
|1st Perigee||299.1 kilometers (161.5 nmi)|
|1st Apogee||299.7 kilometers (161.8 nmi)|
|Reentered||September 15, 1967|
Rendezvous and docking
Their first course adjustment was made at one hour and 34 minutes into the mission, when the astronauts lowered their apogee slightly with a five second Orbit Attitude and Maneuvering System (OAMS) thruster burn. The second adjustment was made near apogee of the second orbit, and raised both the apogee and perigee by adding 49 feet per second (15 m/s) to their speed. The third adjustment was made over the Pacific Ocean, a southward orbital plane change, made with an 59 feet per second (18 m/s) sideways thruster burn. When they were over Mexico, Jim Lovell, the Houston capsule communicator, told them they needed one last correction, a 2.6 feet per second (0.79 m/s) speed addition.
The rendezvous radar acquired the Agena Target Vehicle at a distance of 179 nautical miles (332 km). At 3 hours, 48 minutes and 10 seconds into the mission they performed another burn that put them in a circular orbit 15 nautical miles (28 km) below the Agena. They first sighted it when they were 76 nautical miles (141 km) away, and at 55 nautical miles (102 km) they gave the computer automatic control.
After several small burns they were 151 feet (46 m) 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 to move towards the Agena at 3.15 inches (8 centimeters) per second. 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," Scott radioed to the ground.
There was some suspicion on the ground that the Agena's attitude control 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 OAMS thrusters to stop the roll, but after the roll stopped, it immediately started again. Gemini 8 was out of range of ground communications at this time.
Armstrong reported that the OAMS fuel had dropped to 30%, indicating that the problem could be on their own spacecraft. They decided to undock from the Agena so they could analyze the situation. Scott switched the Agena control back to ground command, while Armstrong struggled to stabilize the combined vehicle enough to permit undocking. Scott then hit the undock button, and Armstrong fired a long burst of translation thrusters to back away from the Agena.
Without the added mass of the Agena, the Gemini's rate of spin began to accelerate quickly. Soon after this, they came in range of the ground communications ship Coastal Sentry Quebec. By now the spin rate had reached one revolution per second, giving the astronauts blurred vision, and putting them in danger of loss of consciousness. Armstrong decided to shut down the OAMS and used the Re-entry Control System (RCS) thrusters to stop the spin. After steadying the spacecraft, they tested each OAMS thruster in turn and found that Number 8 had stuck on. Almost 75 percent of the reentry maneuvering fuel had been used to stop the spin, and mission rules dictated that the flight be aborted once the RCS was fired for any reason. Gemini 8 immediately prepared for an emergency 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. Three hours after splashdown, the Mason had the spacecraft on board.
For several days after the Gemini reentry, the Agena vehicle was tested by a variety of maneuvers initiated 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, spacecraft designs were changed so each thruster would have an isolated circuit.
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. 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." 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 McDonnell engineers in Houston for the entire mission.
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.
- McDowell, Jonathan. "SATCAT". Jonathan's Space Pages. Retrieved March 23, 2014.
- Hacker, Barton C.; Grimwood, James M. (September 1974). "Chapter 11 Pillars of Confidence". On the Shoulders of Titans: A History of Project Gemini. NASA History Series. SP-4203. NASA. p. 239. With Gemini IV, NASA changed to Roman numerals for Gemini mission designations.
- "Civilians in Space".
- "Space.com Joseph A Walker".
- "Valentina Vladimirovna Tereshkova". Retrieved 2010-05-04.
- "Gemini 8". National Space Science Data Center. National Aeronautics and Space Administration.
- Gatland, Kenneth (1976), Manned Spacecraft (2nd revision ed.), New York: MacMilan, p. 176, ISBN 0-02-542820-9
- "Gemini8 Crew and PJs". Retrieved 2010-06-15.
- Seamans, Jr., Robert C. (2005), Project Apollo: The Tough Decisions, Monographs in Aerospace History (Washington, D.C.: NASA) 37, SP-2005-4537
- Dr. Robert C. Seamans, Jr. (April 5, 1967). "NASA Management Instruction 8621.1 April 14, 1966". Apollo 204 Review Board Final Report. NASA. Retrieved March 7, 2011.
- "On The Shoulders of Titans - Ch13-6". Retrieved 2011-05-04.
|Wikimedia Commons has media related to Gemini 8.|
- 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 https://usspaceobjectsregistry.state.gov/Pages/Home.aspx
- Gemini 8 Docks with Agena Video
- "Gemini 8, This is Houston Flight" NASA Documentary: http://www.youtube.com/watch?v=fmD73uyNxvY