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.
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
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 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.