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Falcon 9 countdown timeline
Posted: May 15, 2012

NOTE: All times approximate

T-minus 7 hours, 30 minutes Power Vehicle
Launch controllers power up the Falcon 9 rocket for countdown operations.
T-minus 3 hours, 50 minutes Begin LOX Loading
Liquid oxygen begins flowing into the Falcon 9 rocket's first and second stages.
T-minus 3 hours, 40 minutes Begin RP-1 Loading
Highly-refined kerosene - a product called RP-1 - begins flowing into the Falcon 9 rocket's first and second stages.
T-minus 3 hours, 15 minutes Fueling Complete
The Falcon 9's propellant tanks are full. Cryogenic liquid oxygen will continue to be replenished until the final minutes of the countdown.
T-minus 13 minutes Final Readiness Poll
The launch team is polled for their "go" or "no go" for entering the terminal countdown.
T-minus 10 minutes Begin Terminal Countdown
The terminal countdown sequence begins.
T-minus 8 minutes Dragon Internal Power
The Dragon spacecraft is transitioned to internal power.
T-minus 6 minutes Align Flight Computer
The Falcon 9's flight computer is aligned for flight.
T-minus 5 minutes Falcon Internal Power
The Falcon 9 rocket is transitioned to internal power.
T-minus 3 minutes Terminate LOX Loading
The liquid oxygen replenishment to the rocket's first and second stages ends and the system is readied for liftoff.
T-minus 2 minutes, 30 seconds SpaceX Reports GO
The SpaceX launch director confirms the Falcon 9 is "go" for launch.
T-minus 2 minutes Air Force Range Reports GO
The U.S. Air Force range safety officer verifies "go" for launch.
T-minus 1 minute Flight Computer in Start-Up Mode
The Falcon 9 flight computer is commanded to start-up mode, and the launch pad's Niagara and deck water systems are activated.
T-minus 50 seconds First Stage Steering Check
The thrust vector control, or gimbal, system on the first stage's Merlin engines is checked for launch.
T-minus 40 seconds Pressurize Propellant Tanks
The Falcon 9's first and second stage propellant tanks are pressurized for flight.
T-minus 3 seconds Start Engine Ignition Sequence
The engine controller commands the Falcon 9's nine Merlin 1C first stage engines to ignite, followed by a computer health check to verify the engines are healthy before liftoff.

Data source: SpaceX