Gemini 8

Backup crew

Mission parameters

  • Mass
    Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

    3789 kilograms (8,353.3 lb)
  • Perigee
    Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...

    159.9 kilometres (99.4 mi)
  • Apogee: 271.9 kilometres (169 mi)
  • Inclination
    Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...

  • Period
    Orbital period
    The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...

    88.83 min


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.


It was five months since NASA had tried to launch an Agena
Agena Target Vehicle
The Agena Target Vehicle was an unmanned spacecraft used by NASA during its Gemini program to develop and practice orbital space rendezvous and docking techniques and to perform large orbital changes, in preparation for the Apollo program lunar missions.-Operations:Each ATV consisted of an Agena-D...

 and Gemini. This time everything worked perfectly. The Agena put itself into a 298-kilometer circular orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

 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
Titan II GLV
The Titan II GLV or Gemini-Titan was an American expendable launch system derived from the Titan II missile, which was used to launch twelve Gemini missions for NASA between 1964 and 1966...


Gemini 8 Agena Info
Agena GATV-5003
NSSDC ID: 1966-019A
Mass 3175 kilograms (6,999.7 lb)
Launch site LC-14
Launch date March 16, 1966
Launch time 15:00:03 UTC
1st Perigee 299.1 kilometres (185.9 mi)
1st Apogee 299.7 kilometres (186.2 mi)
Period 90.47 m
Inclination 28.86
Reentered September 15, 1967

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 (206.3 mi) from the Agena
RM-81 Agena
The RM-81 Agena was an American rocket upper stage and satellite support bus which was developed by Lockheed initially for the canceled WS-117L reconnaissance satellite program...

 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 (17.4 mi) below the Agena. They first sighted it when they were 140 kilometres (87 mi) away and at 102 kilometres (63.4 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.


There was some suspicion on the ground that the Agena
RM-81 Agena
The RM-81 Agena was an American rocket upper stage and satellite support bus which was developed by Lockheed initially for the canceled WS-117L reconnaissance satellite program...

 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
Reaction control system
A reaction control system is a subsystem of a spacecraft whose purpose is attitude control and steering by the use of thrusters. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow...

 (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.


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
USS Leonard F. Mason (DD-852)
USS Leonard F. Mason was a in the United States Navy, She was named for Private First Class Leonard F. Mason USMC , who was posthumously awarded the Medal of Honor for his heroism during the Battle of Guam.Leonard F...

 started to steam towards the new landing site 800 kilometers east of Okinawa
Okinawa, Okinawa
is the second-largest city in Okinawa Prefecture, Japan, following Naha, the capital city. It is located in the central part of the island of Okinawa, about 20 km north of Naha....

 and 1,000 kilometers south of Yokosuka
Yokosuka, Kanagawa
is a city located in Kanagawa, Japan. As of 2010, the city had an estimated population of 419,067 and a population density of 4,160 people per km². It covered an area of 100.62 km²...

, Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...


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
Les Schneider
Leslie George Schneider, born December 13, 1939, grew up in Woodstock & Staten Island, New York. He and his younger brother Wayne were raised by their grandmother and grandfather...

, 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.

Had Gemini 8 landed in the western Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 (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
USS Boxer (CV-21)
USS Boxer was one of 24 s built during World War II for the United States Navy. She was the fifth US Navy ship to bear the name, and was named for a British ship captured by the Americans during the War of 1812...

. During this time the Wasp
USS Wasp (CV-18)
USS Wasp was one of 24 s built during World War II for the United States Navy. The ship, the ninth US Navy ship to bear the name, was originally named Oriskany, but was renamed while under construction in honor of the previous , which was sunk 15 September 1942...

 (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
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...

 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
Robert Seamans
Robert Channing Seamans, Jr. was a NASA Deputy Administrator and MIT professor.-Birth and education:He was born in Salem, Massachusetts to Pauline and Robert Seamans. His great-great-grandfather was Otis Tufts...

, was attending a celebratory dinner sponsored by the Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...

, at which Vice President Hubert Humphrey
Hubert Humphrey
Hubert Horatio Humphrey, Jr. , served under President Lyndon B. Johnson as the 38th Vice President of the United States. Humphrey twice served as a United States Senator from Minnesota, and served as Democratic Majority Whip. He was a founder of the Minnesota Democratic-Farmer-Labor Party and...

 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
Apollo 1
Apollo 1 was scheduled to be the first manned mission of the Apollo manned lunar landing program, with a target launch date of February 21, 1967. A cabin fire during a launch pad test on January 27 at Launch Pad 34 at Cape Canaveral killed all three crew members: Command Pilot Virgil "Gus"...

 spacecraft fire on January 27, 1967. It was also invoked after the next critical in-flight failure, which occurred on the Apollo 13
Apollo 13
Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, at 13:13 CST. The landing was aborted after an oxygen tank exploded two days later, crippling the service module upon which the Command...

 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
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...

 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.


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
Gemini (constellation)
Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century astronomer Ptolemy and it remains one of the 88 modern constellations today. Its name is Latin for "twins", and it is associated with the twins Castor and Pollux in Greek mythology...

, , and the Roman numeral for eight, VIII. The two stars are Castor
Castor (star)
Castor is the second brightest star in the constellation Gemini and one of the brightest stars in the night sky. Although it has the Bayer designation "alpha", it is actually fainter than Beta Geminorum...

 and Pollux
Pollux (star)
Pollux is an orange giant star approximately 34 light-years from the Earth in the constellation of Gemini . Pollux is the brightest star in the constellation, brighter than Castor...

, 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
Wapakoneta, Ohio
Wapakoneta is a city in and the county seat of Auglaize County, Ohio, United States with a population of 9,474 as of the 2000 U.S. census. It is the principal city of and is included in the Wapakoneta, Ohio Micropolitan S A, which is included in the Lima-Van Wert-Wapakoneta, Ohio CSA...


External links

  • NASA Gemini 8 press kit - Mar 11, 1966
  • On The Shoulders of Titans: A History of Project Gemini:
  • A site about the U.S.S. Leonard F. Mason (DD-852)
  • U.S. Space Objects Registry
  • Gemini 8 Docks with Agena Video
  • "Gemini 8, This is Houston Flight" NASA Documentary:
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