T-9 minutes and holding This is the final built-in hold, and varies in length depending on the mission. Final launch window determination Activate flight recorders Final "go/no-go" launch polls conducted by NASA Test Director, Mission Management Team and launch director T-9 minutes and counting Start automatic ground launch sequencer Retract orbiter access arm (T-7 minutes, 30 seconds) Start auxiliary power units (T-5 minutes, 0 seconds) Arm solid rocket booster range safety safe and arm devices (T-5 minutes, 0 seconds) Start orbiter aerosurface profile test, followed by main engine gimbal profile test (T-3 minutes, 55 seconds) Retract gaseous oxygen vent arm, or "beanie cap" (T-2 minutes, 55 seconds) Crew members close and lock their visors (T-2 minutes, 0 seconds) Orbiter transfers from ground to internal power (T-50 seconds) Ground launch sequencer is go for auto sequence start (T-31 seconds) Activate launch pad sound suppression system (T-16 seconds) Activate main engine hydrogen burnoff system (T-10 seconds) Main engine start (T-6.6 seconds) T-0 Solid rocket booster ignition and liftoff!