Monday, April 16, 2018

ULA Notches Another Successful Mission with Flight of USAF Payloads on AFSPC-11

United Launch Alliance sent the AFSPC-11 mission on its way to orbit on Saturday, March 14, 2018 at the very opening of a four-hour long launch window that opened at 7:13 p.m. ET. Photo Credit: Mike Deep / SpaceFlight Insider

Amidst scattered clouds, United Launch Alliance (ULA) notched its fourth successful flight of 2018. The April 14, 2018, AFSPC-11 mission was a classified one, however, carried out on behalf of the United States Air Force.

The Colorado-based company’s AV-079 Atlas V lifted off at 7:13 p.m. EDT (23:13 GMT) from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida to deliver two U.S. Air Force payloads to a geostationary Earth orbit (GEO).

The workhorse of ULA‘s stable of launch vehicles, the Atlas V used for this mission was set up in its 551 configuration, signifying that it utilized a 5-meter payload fairing, five supplemental Aerojet Rocketdyne AJ-60A solid rocket boosters, and a single-engine Centaur stage.

It was the eighth launch of this configuration of the 205-foot (62.5-meter) Atlas V with one of the most notable payloads having been sent aloft being NASA’s Juno spacecraft, which began its mission to Jupiter in August of 2011.

Following the startup of the Russian-built RD-180 main engine, the vehicle quickly leapt off the pad with the ignition of the five supplemental solid rocket boosters and rose into the evening sky. Booster separation occurred nearly two minutes after liftoff, with the spent motors falling away to splash down in the Atlantic Ocean below.

Once above the thick atmosphere, the 16.4-foot (5-meter) wide payload fairing, no longer needed, was jettisoned approximately 3.5 minutes into the flight. Unlike the 13.1-foot (4-meter) fairing used on the Atlas V 400-series, the larger diameter protects both the payload and Centaur stage from launch and aerodynamic stresses, rather than simply protecting the payload as is the case with its smaller sibling.

Indeed, any time four, or more, solid rocket boosters are needed on a flight, the larger diameter fairing is used regardless of the dimensions of the payload.

Continuing its ascent, the RD-180 continued to power the core stage for nearly another minute before booster engine cutoff (BECO), followed shortly by stage separation.

Ten seconds later, the Aerojet Rocketdyne RL10C-1 engine on the Centaur ignited, firing for more than six minutes until its first cut off at 10 minutes, 50 seconds after liftoff. The vehicle then coasted for more than 12 minutes before being re-ignited for a second burn of nearly six minutes, cutting off more than 28 minutes after leaving Florida.

With the AFSPC-11 mission profile requiring a direct-to-GEO, rather than a more common geostationary transfer orbit—where the spacecraft uses its onboard propulsion to reach its final orbit—the RL10 fired for a third time after a coast of more than five hours. This burn, lasting for slightly less than three minutes, circularized the orbit at about 24,498 miles (39,426 kilometers) above the equator.

At the completion of the third firing of the RL10, a one-hour window opened for spacecraft deployment. Perched in the top position, the Continuous Broadcast SATCOM (CBAS) was the first to deploy. This was followed by the Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA) Augmented Geosynchronous Laboratory Experiment (EAGLE). According to the mission profile, the spacecraft are expected to take up their position in GEO somewhere over the island of Borneo.

This mission was the 77th overall of the Atlas V line. When combined with the company’s Delta IV series of launch vehicles, the company has had 113 launches since its inception in 2006—without a mission failure.

“Today’s launch is a testament to why the ULA team continually serves as our nation’s most reliable and successful launch provider for our nation’s most critical space assets,” said Gary Wentz, ULA vice president of Government and Commercial Programs via a company-issued release. “I want to thank the entire ULA team, and the phenomenal teamwork of our mission partners.”

Written by: Curt Godwin
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