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NSSDCA/COSPAR ID: 1965-024A

Description

Gemini 3 was the first crewed Earth-orbiting spacecraft of the Gemini series. It was piloted by astronauts Virgil 'Gus' Grissom and John Young, with the primary objective of demonstrating the crewed qualifications of the Gemini spacecraft including evaluation of the two-man Gemini design, the worldwide tracking network, the orbit attitude and maneuver system (OAMS), the control of reentry flight path and landing point, spacecraft systems, and spacecraft recovery. Secondary objectives included evaluation of flight crew equipment and effects of low level launch vehicle oscillations (POGO) on the crew, performance of three experimants, and to obtain photographic coverage from orbit.

Mission Profile

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Gemini 3 was launched from Complex 19 at 9:24 a.m. EST (14:24:00.064 UT) and inserted 5 minutes 54 seconds later (9:29:54 a.m. EST) into a 161.2 x 224.2 km (87 x 121 nautical mile) orbit with a period of 88.3 minutes. At the end of the first orbit Grissom effected the first orbital maneuver, which lowered the orbit to a near-circular 158 x 169 kms. On the second orbit Grissom altered the spacecraft inclination by 0.02 degrees. Near the end of the third orbit, at 4:21:23 ground elapsed time, or GET (1:45:23 p.m. EST) the perigee was lowered to 84 km to allow the orbit to decay naturally in case of retrorocket failure. Reentry began at the end of the third orbit and was manually controlled with retrofire at 4:33:23 GET (1:57:23 p.m. EST). At an altitude of 90 km about 7 kg of water were injected into the ionized plasma sheath resulting in improved communications during the blackout period.

Splashdown occurred in the Atlantic in the vicinity of Grand Turk Island, at 22.43 N, 70.85 W, at 4:52:31 GET (2:16:31 p.m. EST). Due to less-than-expected spacecraft lift during reentry, the spacecraft landed 111 km short of the target point. Both astronauts became seasick, removed their suits, and left the spacecraft at about 3:00 p.m. EST. They were picked up by helicopter and taken to the recovery ship U.S.S. Intrepid at 3:28 p.m. EST, where they were found to be in good condition. The Gemini capsule was recovered at 5:03 p.m. EST. Two of the three experiments were performed successfully, the third, sea urchin egg growth in zero-G, was not due to a mechanical failure. The photography objective was only partially achieved because of an improper lens on the 16 mm camera. All other mission objectives were achieved.

Spacecraft and Subsystems

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.

Control, Propulsion, and Power

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.

Communications

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.

Reentry

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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.

Gemini Program

The Gemini program was designed as a bridge between the Mercury and Apollo programs, primarily to test equipment and mission procedures in Earth orbit and to train astronauts and ground crews for future Apollo missions. The general objectives of the program included: long duration flights in excess of of the requirements of a lunar landing mission; rendezvous and docking of two vehicles in Earth orbit; the development of operational proficiency of both flight and ground crews; the conduct of experiments in space; extravehicular operations; active control of reentry flight path to achieve a precise landing point; and onboard orbital navigation. Each Gemini mission carried two astronauts into Earth orbit for periods ranging from 5 hours to 14 days. The program consisted of 10 crewed launches, 2 uncrewed launches, and 7 target vehicles, at a total cost of approximately 1,280 million dollars.

Alternate Names

• 01301
• Gemini3

Facts in Brief

Keykey 2 1 – typing tutor practice. Launch Date: 1965-03-23
Launch Vehicle: Titan II
Launch Site: Cape Canaveral, United States
Mass: 3236.9 kg

Funding Agency

• NASA-Office of Manned Space Flight (United States)

Disciplines

• Life Science
• Human Crew
• Earth Science

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Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams

Personnel

Selected References

• Gemini midprogram conference including experimental results, NASA, SP-121, 1966. (Papers Presented at the Manned Spaceflight Center, Houston, Feb. 23-25, 1966)
• Gemini summary conference, NASA, SP-138, Wash, DC, Feb. 1967.
• Grimwood, J. M., et al., Project Gemini technology and operations - A chronology, NASA, NASA SP-4002, Wash., DC, 1969.

Diagram of the Gemini capsule. (Courtesy of NASA History Office.)

Gemini Books Online

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Gemini Home Page
Chronology of U.S. Astronaut Missions - Mercury, Gemini, and Apollo

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