Spaceflight Now Home

Mission Reports

For 12 years, Spaceflight Now has been providing unrivaled coverage of U.S. space launches. Comprehensive reports and voluminous amounts of video are available in our archives.
Space Shuttle
Atlas | Delta | Pegasus
Minotaur | Taurus | Falcon


Sign up for our NewsAlert service and have the latest space news e-mailed direct to your desktop.

Enter your e-mail address:

Privacy note: your e-mail address will not be used for any other purpose.


Space Books

WGS 4 launch timeline
Updated: January 14, 2012

Bookmark and Share

T-00:05.5 Engine start
The 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 full throttle for a computer-controlled checkout before liftoff.
T-00:00.0 Liftoff
The rocket's four 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+00:50.1 Max-Q
The vehicle experiences the region of maximum dynamic pressure. The solid motors and the RS-68 liquid hydrogen/liquid oxygen engine continue to fire as the vehicle heads downrange, arcing over the Atlantic along a 101-degree flight azimuth.
T+01:40.0 Jettison two solid motors
Having used up all their solid-propellant and experienced burnout six seconds ago, the two strap-on boosters with fixed nozzles are jettisoned from the Delta's first stage.
T+01:42.4 Jettison two solid motors
The pair of strap-on boosters with steerable nozzles are jettisoned from the Delta's first stage and fall into the ocean.
T+03:27.0 Jettison payload fairing
The five-meter diameter composite payload fairing that protected the WGS 4 cargo atop the Delta 4 during the atmospheric ascent is no longer needed, allowing it to be jettisoned in two halves.
T+03:59.9 Begin engine throttling
With the maximum axial acceleration reached, the RS-68 powerplant starts throttling down in preparation for finishing its firing.
T+04:06.9 Main engine cutoff
The hydrogen-fueled RS-68 rocket engine completes its burn and shuts down to complete the first stage of flight.
T+04:14.0 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+04:27.0 Second stage ignition
The upper stage begins its job to place the WGS 4 satellite into space with the first of two firings by the RL10B-2 liquid hydrogen/liquid oxygen engine.
T+20:42.9 Upper stage shutdown
The RL10 upper stage engine shuts down to complete its first firing of the launch. The rocket and attached satellite reach a parking orbit of approximately 100 by 3,714 nautical miles with an inclination of 25.59 degrees.
T+28:27.5 Restart upper stage
After a short coast period, the upper stage is reignited to raise the orbit to the planned altitude for deploying the payload.
T+31:35.8 Upper stage shutdown
The powered phase of the Delta 4's mission to loft WGS 4 concludes. The second burn will reach the planned supersynchronous orbit 237 by 36,108 nautical miles with an inclination of 24 degrees.
T+40:42.0 Separate spacecraft
The Wideband Global SATCOM 4 military communications satellite is released into space from the Delta 4 rocket. The Boeing-built satellite will use its onboard propulsion to reach geostationary orbit where it will match Earth's rotation and appear fixed above the equator to cover the Middle East and Southeast Asia.

Data source: Air Force/ULA