September 20, 2019

Timeline: Delta 4/GSSAP launch events


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Follow the unclassified portion of the Delta 4 rocket’s ascent to space from Cape Canaveral’s Complex 37 launch pad with the U.S. Air Force’s two Geosynchronous Space Situational Awareness Program, or GSSAP, satellites. Launch is scheduled for Friday at 12:47 a.m. EDT (0447 GMT).

T-0:00:05.0: Ignition sequence start
d1
The RS-68A 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 full throttle for a computer-controlled checkout before liftoff.

T+0:00:00.0: Liftoff
d2
The rocket’s two strap-on solid rocket motors are lit, the four hold-down bolts are released and the Delta 4 lifts off from Cape Canaveral’s pad 37B. The pad’s three swing arms retract at T-0 seconds.

T+0:00:43.8: Mach 1 and Max Q
d3
The Delta rocket achieves Mach 1 some 44 seconds into the flight, then passes through the region of maximum dynamic pressure at 57 seconds with both solid motors and the RS-68A liquid hydrogen/liquid oxygen engine continue to fire as the vehicle heads downrange.

T+0:01:40.1: Solid Rocket Booster Separation
d4
Having used up all their solid-propellant and experienced burnout six seconds ago, the two strap-on boosters are jettisoned from the Delta’s first stage. The spent casings fall into the ocean.

T+0:03:57.7: Main Engine Cutoff
ascent5
The liquid hydrogen-fueled RS-68A rocket engine throttles down to its minimum power level and then shuts down to finish the first stage burn.

T+0:04:05.1: Stage Separation
ascent6
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+0:04:19.6: Upper Stage Ignition No. 1
ascent7
The upper stage begins its job to place the Geosynchronous Space Situational Awareness Program satellites into space with the first firing by the RL10B-2 liquid hydrogen/liquid oxygen engine.

T+0:04:30.1: Nose Cone Jettison
ascent8
The two-piece, 13-foot-diameter composite payload fairing that protected the GSSAP craft during the atmospheric ascent is separated to reveal the satellites to space.

News Blackout
upperstage
The Delta 4 rocket flies into a pre-arranged news blackout, conducting its engine firings and maneuvers in secrecy. As such, the timeline beyond the point of payload fairing jettison is not available.

See earlier Delta 375 coverage.

Our Delta archive.


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