Operations Agena target vehicle

an atlas launch vehicle launches gatv-5006 orbit gemini 11 mission.

each atv consisted of agena-d derivative upper rocket stage built lockheed aircraft , docking adapter built mcdonnell aircraft. agena launched cape kennedy s launch complex 14 on top of atlas booster built convair division of general dynamics. agena first burn occur shortly after shroud jettison , separation atlas on atlantic ocean. on ascension island, second burn place agena low circular orbit.

the mcdonnell gemini spacecraft launched launch complex 19, 90 minutes later. both countdowns proceed in parallel , required close synchronization. gemini rendezvous , dock agena gemini s first orbit toward end of program.

the gemini astronauts fly combined spacecraft in stabilized mode , perform number of experiments:

using agena s attitude control system stabilize combination, saved gemini s propellants
extra-vehicular activity perform practice work on tool panel. required installing handrails on later flights prevent excessive astronaut exertion.
refiring agena engine raise spacecraft s apogee. gemini 11 reached record of 739.2 nautical miles (1,369.0 km). modified bell 8247 engine qualified 15 restarts.
undocking, unreeling 50-foot (15 m) nylon tether between capsule , agena , flying in dumbbell configuration agena below astronauts, check gravitational effect on formation stability in uncontrolled mode. technique known gravity-gradient stabilization.
using similar tether , few thruster bursts rotate 2 craft around each other test of artificial gravity.
after rendezvous own atv, gemini 10 performed second rendezvous atv gemini 8.

after gemini capsule separated last time, agena remained in orbit short time , used verify command system.

the first gemini-agena target vehicle (gatv) launched on october 25, 1965, while gemini 6 astronauts waiting on pad. while atlas performed normally, agena s engine exploded during orbital injection. since rendezvous , docking primary objective, gemini 6 mission scrubbed, , replaced alternate mission gemini 6a, rendezvoused (but not dock) gemini 7 in december.

an investigation failure concluded caused design modifications gatv versus standard agena d stage. agena d designed have engine restarted once while gatv need restarted 5 times. while standard agena d pumped oxidizer combustion chamber first , followed fuel, gatv modified reverse because normal start method had tendency leak oxidizer. while not problem agena d single restart, multi-restart gatv lose of oxidizer before stage s operating life (which last weeks instead of hours) completed. unfortunately, pumping fuel combustion chamber first caused engine backfire , rupture mechanical shock. found out lockheed engineers did not test gatv root out problem (it had been tested @ simulated altitude of 21 miles when actual agena engine start occur @ around 75 miles up). solution problem switching normal oxidizer-first engine start , testing gatv in appropriate conditions. bell aerosystems, manufacturer of agena s engine, instructed perform further ground-level tests.