Delta IV Countdown Timeline

Time Event
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
HOLDING Countdown Briefing
L-04:33:00 Go/No GO for Propellant Loading
04:15:00 Redundant Inertial Flight Control Assembly Activation
04:15:00 Cryogenic Tanking begins
04:15:00 Common Booster Core LH2 Tank Chilldown
03:55:00 Common Booster Core LH2 Loading in Slow Fill
03:45:00 CBC LH2 Load Transitions to Fast Fill
03:45:00 Common Booster Core LOX Tank Chilldown
03:35:00 Common Booster Core LOX Loading in Slow Fill
03:30:00 CBC LOX Load Transition to Fast Fill
03:20:00 C-Band Beacon Checkouts, GPS Verifications
03:10:00 Delta Cryogenic Upper Stage LH2 Tank Chilldown
03:10:00 Guidance System Activation
02:55:00 CBC LH2 Topping – Fill & Drain Valve Checks
02:50:00 DCSS LH2 Loading
02:40:00 CBC LOX Topping – Fill & Drain Valve Checks
02:30:00 Delta Cryogenic Upper Stage LOX Tank Chilldown
02:30:00 Launch Weather Briefing
02:20:00 DCSS LOX Loading
01:45:00 DCSS LH2 Topping
01:20:00 DCSS LOX Topping
01:10:00 Radio/Telemetry Link Checks, FTS Checks
00:55:00 Command Receiver Decoder Testing
00:50:00 RS-68 Engine Spin Start Pressurization
00:50:00 RS-68 Gimbal Steering Checks
00:45:00 Flight Termination System Testing complete
00:15:00 Weather Briefing
00:08:00 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
00:04:00 Delta IV to internal Power
00:04:00 Arm Safe and Arm Switches
00:04:00 DCSS Tank Propellant Securing
00:03:30 Transfer to Internal complete
00:03:30 Common Booster Core Propellant Tank Securing
00:03:15 CBC Pre-Press
00:03:00 Common Booster Core LOX secure at Flight Level
00:03:00 Common Booster Core LH2 secure at Flight Level
00:03:00 Vehicle Ordnance Arming
00:03:00 CBC LOX at Flight Level and Flight Pressure
00:02:00 Master Script Running
00:02:00 Second Stage LOX Securing
00:02:00 Hydraulic System to Flight Pressure
00:01:45 CBC LH2 at Flight Level and Flight Pressure
00:01:30 Second Stage LOX secured at Flight Level
00:01:20 Second Stage LH2 Securing
00:01:20 LOX Ground Support Equipment secured
00:01:00 Range Verification
00:00:50 Second Stage LH2 secure at Flight Level
00:00:45 Launch Enable
00:00:45 Main Power Off
00:00:25 Green Board
00:00:15 Launch Vehicle Igniters armed
00:00:14 Radially Outward Firing Initiators Ignition
00:00:10 Terminal Countdown Sequencer in Control
0:00:05.5 RS-68 LH2 Valve Open
0:00:02.0 RS-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