Launch events timeline

Posted: March 4, 2003

T-00:05.5 Engine start
The Rocketdyne RS-68 main engine begins to ignite as the liquid hydrogen fuel valve is opened, creating a large fireball at the base of the rocket. The engine powers up to the 101 percent level of thrust for a computer-controlled checkout before liftoff.
T-00:00.0 Liftoff
The hold-down bolts are released and the second flight of Delta 4 is underway from Cape Canaveral's pad 37B. The three umilical swing arms extending from the launch pad tower retract from the rocket at T-0 seconds.
T+01:30.6 Max-Q
The vehicle experiences the region of maximum dynamic pressure. The RS-68 liquid hydrogen/liquid oxygen engine continues to fire as the vehicle heads downrange, arcing over the Atlantic.
T+03:36.8 Begin engine throttling
With engine shutdown coming up and the axial acceleration reached, the RS-68 powerplant starts throttling down from 101 percent. It will achieve a 58 percent throttle at T+3 minutes, 41.8 seconds.
T+04:19.9 Main engine cutoff
The first large all-American rocket engine developed in a quarter-century completes its second launch as the RS-68 shuts down.
T+04:30.9 Stage separation
The Common Booster Core first stage and the attached interstage are separated in one piece from the Delta 4's upper stage. The upper stage engine's extendible nozzle drops into position as the first stage separates.
T+04:44.4 Second stage ignition
The upper stage begins its job to place the DSCS A3 spacecraft into space with the first of two firings. The stage and its Pratt & Whitney RL-10B-2 liquid hydrogen/liquid oxygen engine is basically identical to the Delta 3 upper stage flown previously.
T+04:54.5 Jettison payload fairing
The four-meter diameter composite payload fairing that protected the DSCS cargo atop the Delta 4 during the atmospheric ascent is no longer needed, allowing it to be jettisoned in two halves.
T+14:13.4 Upper stage shutdown
The RL-10 upper stage engine shuts down to complete its first firing of the launch. The rocket and attached satellite reach a parking orbit of 100.0 by 216.7 nautical miles with an inclination of 29.20 degrees.
T+26:03.0 Restart upper stage
After a 12-minute coast period, the upper stage is reignited to finish the task of boosting DSCS into the intended orbit.
T+30:11.2 Upper stage shutdown
The powered phase of the Delta 4's mission to loft W5 concludes. The targeted geosynchronous transfer orbit is 125.8 by 19,323.5 nautical miles with an inclination of 25.50 degrees.
T+30:41.2 Maneuver to deploy attitude
The upper stage uses its thrusters to maneuver into the proper orientation for release of W5. This attitude maneuver will last until T+32 minutes, 1.2 seconds.
T+37:51.2 Begin spin-up
The next step in preparing for deployment of the payload is spinning up the stage like a top to 4.6 rpm.
T+42:01.7 Spacecraft separate
The Air Force's Defense Satellite Communications System A3 spacecraft is released into space from the Delta 4 rocket, completing the U.S. military's first Evolved Expendable Launch Vehicle mission.

Image and data source: Boeing.

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