The Explorers' Club, № DCCLXXXVIII

Operation AXIOM: The Space Race—The 55th Anniversary of Gemini VI-A, Part I
12 December 1965: Schirra & Stafford boarded their Gemini capsule atop a Titan II G.L.V. for the second time, their revised mission to rendezvous with Gemini VII redesignated Gemini VI-A; the rockets fired, but cut off seconds later; launch abort mission rules called for the crew to use their ejection seats, a risky manuever, but the pilots knew they hadn't lifted off, stood by, & disembarked.

Commentary: The Gemini ejection seats had never been tested in simulated launch conditions: a cabin full of pressurized pure oxygen. The best case scenario if Schirra & Stafford had ejected is that their capsule would have been destroyed & rendezvous with Gemini VII would have been impossible; worse case scenario, in Stafford's words, "we… would have been two Roman candles going out." The false liftoff signal was sent by an umbilical that came unpluged prematurely. This turned out to be fortunate, however, since technicians found a plastic dust cover inside the Titan launch vehicle that would have severely limited the thrust from one of the two engines.

Bonus! Space Race Song o' Gemini VI-A
Less Than Jake, "Help Save the Youth of America from Exploding" from Hello Rockview (Space Cadet Mike Papa Whiskey)