The Gemini escape system provided a means for safe escape of the astronauts through use of the ejection seats while the vehicle is still on the launch pad, during boost and after spacecraft reentry. Actual usage is determined by the altitude, the type of emergency, the system condition, the mission phase, and the astronaut evaluation of the problem. The Gemini Escape System was qualified for use up to a maximum altitude of 70,000 feet. Above that altitude the astronauts would stay with the spacecraft and/or use its main parachute system for recovery. Subcontractor for the ejection system is Weber Aircraft.
Two ejection seats are provided in the Gemini Spacecraft for emergency escape. These seats include seat structural assembly, a backboard assembly and egress kit assembly. The seats are arranged side-by-side facing the small end of the crew compartment. They are constructed to be compatible with crew members wearing fully inflated pressure suits. The escape system incorporates a survival kit containing water, food, life raft, fishing gear, a radio transmitter and a machete, all packed into the seat.
The ejection seats function as one complete system. Should the need to abort arise, the decision to eject is made by the astronauts themselves. Once it is determined to eject, either man can pull the escape D-ring located between his knees, ejecting both astronauts. Only when manually initiated by an astronaut will the ejection sequence occur.
When the system has been actuated, the remainder of the operation is fully automatic. First, both hatches of the Gemini Spacecraft are opened simultaneously, then the rocket-catapult powered escape seats are propelled out of the vehicle.
Then, 1.1 seconds after ejection, the seats and men separate; 2.3 seconds later, a drogue gun fires, extracting a pilot and 28-foot diameter main parachute from the astronaut's back pack. A full canopy is achieved less than two seconds later.
In a pad abort, just 10 seconds after leaving the Gemini Spacecraft, both astronauts descend to a safe landing. After reentry the astronauts will have the option of riding the spacecraft to water impact beneath a Northrop-Ventura ringsail parachute or ejecting themselves and landing much like a paratrooper.
In most instances the latter method will not be used unless the spacecraft enters the Earth's atmosphere at a point where a dry landing must be performed (a highly improbable scenario).
The Gemini rocket catapult, furnished Rocket Power, Inc., has a total impulse of 2650 pound seconds. Burning time for the rocket is approximately 1/4 second. Rocket ignition occurs 0.2 seconds after catapult ignition. The astronauts would be subjected to maximum ejection acceleration of 16g. Note: 24 g is the upper limit of human tolerance.
Trajectories that could be expected for "off-the-pad'' ejections would land the astronauts at least 500 feet from the launch vehicle. Tests indicate that the landing point would actually be closer to 800 feet from the launch site. The height of trajectories on ' off-the-pad' tests is approximately 350 feet above the terrain when launched from 150-foot height.
Escape systems testing was begun at the U.S. Naval Ordnance Test Center, China Lake, California, in 1962, using the 150-foot-high tower at Randsburg Wash. The 150-foot tower was used to simulate escape from the spacecraft while still on the pad. During the field testing operation, environmental studies were conducted on the system's related components, including harnesses, back pack, straps and pyrotechnics to determine component reaction under extreme heat, cold, humidity, shock, and vacuum.
High speed track tests were conducted with a full-scale Gemini boilerplate spacecraft mounted on a rocket powered sled. During sled tests, every possible escape condition was simulated by firing each seat at different attitudes to determine how the system would perform under adverse conditions. The sled was accelerated to 550 mph and the escape system actuated, causing the seats to be ejected out and away from the vehicle to qualify the system for high speed ejections. High altitude tests were conducted at the Naval Parachute Facility, El Centro, California, utilizing an F-106 supersonic fighter flying at Mach 1.75 and 40,000 feet. More than 100 studies and tests were conducted in the laboratory and field before the system was man-rated as operational Gemini equipment.
If the returning astronauts use their ejection seats at high altitude, the ejection sequence will function as in a pad abort situation with one exception. At altitudes above 7,500 feet a device called a ballute will be employed. Designed and built by Goodyear, the ballute will stabilize and decelerate the ejected astronauts during the free fall before parachute deployment.
The ballute, a contraction for balloon-parachute, is a stabilizing device included as part of the ejection system. The ballute is packaged in the ejection seat and is utilized during high altitude aborts to achieve desired stabilization of the astronaut.
The ballute is a balloon-shaped device looking much like a child's spinning top. It is constructed of inflatable rubberized fabric and is packaged in a deflated condition in the ejection seat during flight. The inflated ballute is approximately 48 inches in diameter and 54 inches long. The astronauts can use the ballute at heights up to 14 miles. When an altitude of approximately 5700 feet is reached and after the ballute has been jettisoned, the personal parachute will open automatically and bring the astronaut safely down to Earth.