May 20, 2019

Delta 4 rocket’s launch timeline with WGS 10


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A United Launch Alliance Delta 4 rocket will deliver the U.S. Air Force’s tenth Wideband Global SATCOM communications satellite to a supersynchronous transfer orbit around 37 minutes after lifting off from Cape Canaveral.

Liftoff is scheduled during a launch window opening at 6:56 p.m. EDT (2256 GMT) Friday. The window extends to 9:05 p.m. EDT (0105 GMT).

See our Mission Status Center for live updates on the countdown and flight.

T+00:00:00 — Liftoff

The United Launch Alliance Delta 4 rocket takes off powered by an Aerojet Rocketdyne RS-68A main engine and four solid rocket boosters built by Northrop Grumman Innovation Systems. The hydrogen-burning main engine ignites at T-minus 5 seconds, following by ignition of the four boosters at T-minus 0, the release of four hold-down bolts and retraction of the launch pad’s three swing arms.

T+00:00:47.2 — Max-Q

Heading east from Cape Canaveral with a launch azimuth of 93.46 degrees, the Delta 4 experiences the most extreme aerodynamic pressures at this point in the mission.

T+00:01:40.0 — Solid Rocket Motor Separation

The Delta 4’s four GEM-60 solid rocket boosters are jettisoned in two pairs around seven seconds after consuming all their propellant.

T+00:03:19.0 — Payload Fairing Jettison

The Delta 4’s composite bisector fairing jettisons from the rocket once the launcher reaches a safe altitude above the dense lower layers of Earth’s atmosphere.

T+00:03:55.8 — Booster Engine Cutoff

The Delta 4’s RS-68A main engine shuts down after burning its supply of super-cold liquid hydrogen and liquid oxygen.

T+00:04:02.3 — Stage Separation

The Delta 4’s Common Booster Core separates from the rocket’s second stage.

T+00:04:15.3 — First Second Stage Ignition

The Delta 4’s second stage Aerojet Rocketdyne RL10B-2 engine ignites and powers up to 24,750 pounds of thrust in the first of its two firings to place the WGS 10 satellite into a supersynchronous transfer orbit.

T+00:19:29.6 — First Second Stage Engine Shutdown

The second stage’s RL10B-2 engine shuts down after placing the WGS 10 satellite in a preliminary parking orbit, beginning a 10-minute coast before the engine reignites.

T+00:29:29.6 — Second Stage Engine Restart

The RL10B-2 second stage engine ignites again to send WGS 10 into a higher, elliptical supersynchronous transfer orbit.

T+00:32:50.0 — Second Stage Engine Shutdown

After a burn lasting nearly three-and-a-half minutes, the RL10B-2 second stage engine shuts down to end its second firing on the WGS 10 mission.

T+00:36:50.0 — WGS 10 Separation

The Boeing-built WGS 10 communications satellite separates from the Delta 4 rocket’s second stage in a targeted orbit ranging between 269 miles (433 kilometers) and 27,536 miles (44,315 kilometers) in altitude, with an inclination of 27 degrees to the equator. WGS 10 will use its on-board propulsion system, using a liquid-fueled main engine and plasma thrusters, to maneuver into a circular geostationary orbit around four months after launch, where it will begin final checkouts and enter service for the U.S. Air Force. The Delta 4’s RL10B-2 engine will reignite at T+plus 1 hour, 12 minutes, for a 10-second firing to aim for a destructive re-entry over the Pacific Ocean around 12 hours after liftoff.

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