Human Spaceflights

International Flight No. 18

Gemini 8



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Launch, orbit and landing data

Launch date:  16.03.1966
Launch time:  16:41:02.389 UTC
Launch site:  Cape Canaveral
Launch pad:  LC-19
Altitude:  156 - 265 km
Inclination:  28.91°
Landing date:  17.03.1966
Landing time:  03:22:28 UTC
Landing site:  25° 13.8' N, 136° 0' E

walkout photo

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alternate crew photo

alternate crew photo

alternate crew photo


No.   Surname Given names Position Flight No. Duration Orbits
1  Armstrong  Neil Alden  Command Pilot 1 10h 41m 26s  6,5 
2  Scott  David Randolph  PLT 1 10h 41m 26s  6,5 

Crew seating arrangement

1  Armstrong
2  Scott

Backup Crew

No.   Surname Given names Position
1  Conrad  Charles, Jr. "Pete"  Command Pilot
2  Gordon  Richard Francis, Jr. "Dick"  PLT

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alternate crew photo


Launch from Cape Canaveral; landing 800 km southeast of Okinawa in the Pacific Ocean.

The Gemini spacecraft was a cone-shaped capsule consisting of two components, a reentry module and an adaptor module. The adaptor module made up the base of the spacecraft. It was a truncated cone 228.6 cm high, 304.8 cm in diameter at the base and 228.6 cm at the upper end where it attached to the base of the reentry module. The re-entry module consisted of a truncated cone which decreased in diameter from 228.6 cm at the base to 98.2 cm, topped by a short cylinder of the same diameter and then another truncated cone decreasing to a diameter of 74.6 cm at the flat top. The reentry module was 345.0 cm high, giving a total height of 573.6 cm for the Gemini spacecraft.
The adaptor module was an externally skinned, stringer framed structure, with magnesium stringers and an aluminum alloy frame. The adaptor was composed of two parts, an equipment section at the base and a retrorocket section at the top. The equipment section held fuel and propulsion systems and was isolated from the retrorocket section by a fiber-glass sandwich honeycomb blast shield. The retrorocket section held the re-entry rockets for the capsule.
The reentry module consisted mainly of the pressurized cabin which held the two Gemini astronauts. Separating the reentry module from the retrorocket section of the adaptor at its base was a curved silicone elastomer ablative heat shield. The module was composed predominantly of titanium and nickle-alloy with beryllium shingles. At the narrow top of the module was the cylindrical reentry control system section and above this the rendezvous and recovery section which holds the reentry parachutes. The cabin held two seats equipped with emergency ejection devices, instrument panels, life support equipment, and equipment stowage compartments in a total pressurized volume of about 2.25 cubic meters. Two large hatches with small windows could be opened outward, one positioned above each seat.
Attitude control was effected by two translation-maneuver hand controllers, an attitude controller, redundant horizon sensor sytems, and reentry control electronics, with guidance provided via an inertial measuring unit and radar system. The orbital attitude and maneuver system used a hypergolic propellant combination of monomethylhydrazine and nitrogen tetroxide supplied to the engines by a helium system pressurized at 2800 psi. Two 95 lb translation thrusters and eight 23 lb attitude thrusters were mounted along the bottom rim of the adaptor, and two 79 lb and 4 95 lb thrusters were mounted at the front of the adaptor. Power was supplied by 3 silver-zinc batteries to a 22- to 30-volt DC two-wire system. During reentry and post-landing power was supplied by four 45 amp-hr silver-zinc batteries.
Voice communications were performed at 296.9 MHz with an output power of 3 W. A backup transmitter-receiver at 15.016 MHz with an output power of 5 W was also available. Two antenna systems consisting of quarter-wave monopoles were used. Telemetry was transmitted via three systems, one for real time telemetry, one for recorder playback, and a spare. Each system was frequency-modulated with a minimum power of 2 W. Spacecraft tracking consisted of two C-band radar transponders and an acquisition-aid beacon. One transponder is mounted in the adaptor with a peak power output of 600 W to a slot antenna on the bottom of the adaptor. The other is in the reentry section, delivering 1000 W to three helical antennas mounted at 120 degree intervals just forward of the hatches. The acquisition-aid beacon was mounted on the adaptor and had a power of 250 mW.
At the time of reentry, the spacecraft would be maneuvered to the appropriate orientation and equipment adaptor section would be detached and jettisoned, exposing the retrorocket module. The retrorockets consisted of four spherical-case polysulfide ammonium perchlorate solid-propellant motors mounted near the center of the reentry adaptor module, each with 11,070 N thrust. They would fire to initiate the spacecraft reentry into the atmosphere, with attitude being maintained by a reentry control system of 16 engines, each with 5.2 N thrust. The retrorocket module would then be jettisonned, exposing the heat shield at the base of the reentry module. Along with the ablative heat shield, thermal protection during reentry was provided by thin Rene 41 radiative shingles at the base of the module and beryllium shingles at the top. Beneath the shingles was a layer of MIN-K insulation and thermoflex blankets. At an altitude of roughly 15,000 meters the astronauts would deploy a 2.4 meter drogue chute from the rendezvous and recovery section. At 3230 meters altitude the crew releases the drogue which extracts the 5.5 meter pilot parachute. The rendezvous and recovery section is released 2.5 seconds later, deploying the 25.6 meter main ring-sail parachute which is stored in the bottom of the section. The spacecraft is then rotated from a nose-up to a 35 degree angle for water landing. At this point a recovery beacon is activated, transmitting via an HF whip antenna mounted near the front of the reentry module.

The Gemini Agena Target Vehicle (GATV) was designed to be launched into Earth orbit prior to a Gemini mission and used for rendezvous and docking practice. The GATV had a docking cone at the forward end into which the nose of the Gemini spacecraft could be inserted and held with docking latches. The GATV was a 6 meter long cylinder with a diameter of 4.9 meters. The primary and secondary propulsion systems were at the back end of the target vehicle with the attitude control gas tanks and the main propellant tanks. The docking cone was connected to the front end by shock absorbing dampers. Acquisition running lights and target vehicle status display indicators were situated on the front end. A 2.1 meter long retractable L-band boom antenna extended from the side of the cylinder near the front. Tracking and command of the GATV were also aided by a rendezvous beacon, two spiral L-band antennas, two tracking antennas (C-band and S-band), two VHF telemetry antennas, and a UHF command antenna. Micrometeoroid packages and other experiments could also be mounted on the GATV.
The Gemini 8 Agena Target Vehicle (GATV-8) was launched from Cape Canaveral using an Atlas-Agena D rocket on March 16, 1966 at 15:00:03.127 UTC into a near circular 300 km orbit.

The main goals of this mission were, to accomplish a rendezvous and the first docking with the prelaunched Agena Target Vehicle (GATV 8) and to perform again a spacewalk.

Gemini 8 was launched from Complex 19 at 16:41:02.389 UTC on March 16, 1966 and inserted into a 159.9 x 271.9 km orbit at 17:47:36 UTC.

Their first course adjustment was made at one hour and 34 minutes into the mission, when the astronauts lowered their apogee slightly with a 5 second Orbit Attitude and Maneuvering System (OAMS) thruster burn. The second adjustment was made near apogee of the second orbit, and raised both 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 a 59 feet per second (18 m/s) sideways thruster burn. 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.

The first orbital docking was accomplished without any problems (at 23:14:18 UTC), but then the Gemini capsule with the docked GATV 8 began rolling uncontrolled and continuously because of problems with the spacecraft control system (thrusters sticking probably of an electrical short). That problem was never faced in a simulation, so the crew was forced to undock, but the problems continued and were serious. After separation at 23:56:13 UTC, loosing the mass of the Agena, the Gemini spacecraft began to roll even faster. It reached one revolution per second. The only thing to do was turn off the OAMS and switch to the reentry control system, which prompted in an early landing only one orbit later. Meanwhile Neil Armstrong had reported that the OAMS fuel had dropped to 30%. So the planned EVA was not performed. Neil Armstrongs calm headedness and his ability to recover from an extremely dangerous space emergency saved the crew.

Mission control decided to let the spacecraft reenter one orbit later so that it could land in a place and by daylight 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. A possible landing in the Atlantic Ocean hat the same orbit would have resulted a night landing. 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.

The crew was recovered by the USS Leonard F. Mason. Three hours after landing the Mason had the spacecraft on board.

Photos / Graphics

Gemini spacecraft


Last update on May 09, 2016.