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Delta IV - Generic Countdown Timeline
Launch Vehicle Overview
Picture
Photo: ULA
Picture
Photo: ULA
T- Event
L-08:00:00 Countdown Initiation
L-08:00:00 Mobile Service Tower Retraction Weather Briefing
L-08:00:00 Mobile Service Tower Retraction Start
L-05:30:00 Launch Pad Evacuation, Road Blocks Set
L-05:00:00 Blast Danger Area Clear
L-05:00:00 Tanking Weather Briefing
04:15:00 Countdown Clock Initialization
HOLDING Countdown Initiation
  Countdown Briefing
L-04:33:00 Go/No GO for Propellant Loading
04:15:00 Redundant Inertial Flight Control Assembly Activation
4:15:00 Cryogenic Tanking begins
4:15:00 Common Booster Core LH2 Tank Chilldown
3:55:00 Common Booster Core LH2 Loading in Slow Fill
3:45:00 CBC LH2 Load Transitions to Fast Fill
3:45:00 Common Booster Core LOX Tank Chilldown
3:35:00 Common Booster Core LOX Loading in Slow Fill
3:30:00 CBC LOX Load Transition to Fast Fill
3:20:00 C-Band Beacon Checkouts, GPS Verifications
3:10:00 Delta Cryogenic Upper Stage LH2 Tank Chilldown
  Guidance System Activation
2:55:00 CBC LH2 Topping - Fill & Drain Valve Checks
2:50:00 DCSS LH2 Loading
2:40:00 CBC LOX Topping - Fill & Drain Valve Checks
2:30:00 Delta Cryogenic Upper Stage LOX Tank Chilldown
  Launch Weather Briefing
2:20:00 DCSS LOX Loading
1:45:00 DCSS LH2 Topping
1:20:00 DCSS LOX Topping
1:10:00 Radio/Telemetry Link Checks, FTS Checks
0:55:00 Command Receiver Decoder Testing
0:50:00 RS-68 Engine Spin Start Pressurization
  RS-68 Gimbal Steering Checks
0:45:00 Flight Termination System Testing complete
0:15:00 Weather Briefing
0:08:00 Launch Pad Ordnance Armed
T-4 Minutes & HOLDING (Variable Hold & Recycle Point)
L-0:09:30 Delta IV Ready for Spacecraft to Internal Power
L-0:07:00 Final Status Polls
L-0:06:00 Launch Director GO/No GO; Range Clear
L-0:05:00 Confirm Solar Weather is Go for Launch
L-0:05:00 Delta IV Swingarm Lockpins pulled for Rapid Retract
0:04:00 Delta IV to internal Power
0:04:00 Arm Safe and Arm Switches
0:04:00 DCSS Tank Propellant Securing
0:03:30 Transfer to Internal complete
0:03:30 Common Booster Core Propellant Tank Securing
0:03:15 CBC Pre-Press
0:03:00 Common Booster Core LOX secure at Flight Level
0:03:00 Common Booster Core LH2 secure at Flight Level
0:03:00 Vehicle Ordnance Arming
0:03:00 CBC LOX at Flight Level and Flight Pressure
0:02:00 Master Script Running
0:02:00 Second Stage LOX Securing
0:02:00 Hydraulic System to Flight Pressure
0:01:45 CBC LH2 at Flight Level and Flight Pressure
0:01:30 Second Stage LOX secured at Flight Level
0:01:20 Second Stage LH2 Securing
0:01:20 LOX Ground Support Equipment secured
0:01:00 Range Verification
0:00:50 Second Stage LH2 secure at Flight Level
0:00:45 Launch Enable
0:00:45 Main Power Off
0:00:25 Green Board
0:00:15 Launch Vehicle Igniters armed
0:00:14 Radially Outward Firing Initiators Ignition
0:00:10 Terminal Countdown Sequencer in Control
0:00:05.5 RS-68 LH2 Valve Open
0:00:02.0 S-68 LOX Valve Open
0:00:02.0 RS-68 Main Engine to Full Thrust Level - 102%
0:00:00.04 Launch Commit
0:00:00.04 Booster Ignition Command
0:00:00.00 Hold-Down Release
0:00:00.00 LIFTOFF