Delta 4 Rocket Launches Air Force’s 10th WGS Broadband Satellite

March 26, 2019 | Source: spaceflightnow.com, Spaceflight Now, Stephen Clark, 16 March 2019

United Launch Alliance placed a new satellite in orbit with a fiery Friday night blastoff from Cape Canaveral, using a version of the Delta 4 rocket that is nearing retirement to supplement a U.S. military network relaying signals from drones and battlefield commanders.

After ground teams cleared several technical hurdles with the rocket and a satellite tracking network, the 218-foot-tall (66-meter) Delta 4 launcher’s hydrogen-fueled RS-68A main engine flashed to life with an orange burst of flame moments before liftoff.

Five seconds later, four solid rocket motors ignited, and hold-down bolts released at 8:26 p.m. EDT Friday (0026 GMT Saturday) as the Delta 4 rapidly climbed away from Cape Canaveral’s Complex 37B launch pad with 1.8 million pounds of thrust.

The main engine and booster nozzles vectored their thrust to guide the Delta 4 east over the Atlantic Ocean, sending the U.S. Air Force’s tenth Wideband Global SATCOM communications satellite toward its final operating position more than 22,000 miles (nearly 36,000 kilometers) over the equator in geostationary orbit.

The Delta 4’s solid rocket boosters, built by Northrop Grumman, burned out and jettisoned in two pairs around 1 minute, 40 seconds, into the mission. Once above the dense lower layers of the atmosphere, the Delta 4 released its nose cone to reveal the WGS 10 satellite.

The Aerojet Rocketdyne RS-68A main engine fired nearly four minutes until the first stage released to fall into the Atlantic Ocean. An upper stage RL10B-2 engine, also supplied by Aerojet Rocketdyne, ignited two times to loft the WGS 10 spacecraft into an elliptical transfer orbit ranging as high as 27,500 miles (44,300 kilometers) above Earth.

The Boeing-built WGS 10 satellite separated from the Delta 4’s upper stage at T+plus 36 minutes, 50 seconds, extending the company’s streak of successful missions to 133 since its formation in 2006.

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