The Gemini 6 Agena Target Vehicle (vehicle GATV 5002) was launched from Cape Canaveral on 25 October 1965 at 10:00:04 a.m. EST (15:00:04 UT) on an Atlas-Agena D rocket. At 10:05:12 a.m., 5:08 after launch the Agena separated from the Atlas successfully and all signals were normal, but 376 seconds after launch, at initiation of Agena target vehicle primary propulsion system firing for Earth orbit insertion, telemetry and radar beacon track were lost and all attempts to reestablish contact or radar track with the vehicle failed. Just before loss of contact telemetry showed a marked rise in pressure in both propellant tanks. Shortly afterwards radar at Patrick AFB reportedly "picked up 5 pieces" of debris at the point in space the Agena was supposed to be. The Gemini 6 launch, scheduled to occur 101 minutes later, was cancelled. Later investigation concluded the most likely cause of the failure was a hard start and explosion caused by fuel preceding oxidizer into the thrust chamber during ignition.
