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Falcon 9 countdown timeline
Posted: September 18, 2014

NOTE: All times approximate

T-minus 26 hours Power Dragon Vehicle
Launch controllers power up the Dragon spacecraft for countdown operations.
T-minus 10 hours Power Falcon 9 Vehicle
Launch controllers power up the Falcon 9 rocket for countdown operations.
T-minus 4 hours 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, 20 minutes Begin LOX Loading
Liquid oxygen 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 Terminal Countdown Autosequence Start
The computer-controlled terminal countdown automatic sequence begins at T-minus 10 minutes.
T-minus 9 minutes Begin Merlin Engine Chilldown
Pre-valves open to allow super-cold liquid oxygen to flow into the Falcon 9's nine first stage Merlin 1D engines to condition the engine turbopumps for ignition.
T-minus 8 minutes Dragon Internal Power
The Dragon spacecraft is transitioned to internal power.
T-minus 6 minutes Initiate Dragon Autosequence
The Dragon spacecraft's terminal countdown automatic sequence is started.
T-minus 6 minutes Align Flight Computer/Internal Power
The Falcon 9's flight computer is aligned for flight, and the rocket is transitioned to internal power supplies.
T-minus 3 minutes Terminate LOX Loading/FTS Internal Power
The liquid oxygen replenishment to the rocket's first and second stages ends and the system is readied for liftoff. And the rocket's flight termination system is switched to internal power.
T-minus 2 minutes 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 1D 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 1D first stage engines to ignite, followed by a computer health check to verify the engines are healthy before liftoff.

Data source: SpaceX