OA-6 ascent anomaly causes delay of MUOS-5 mission

Jason Rhian

CAPE CANAVERAL, Fla. — The launch of the MUOS-5 satellite has been delayed a week from May 5 until May 12 pending the outcome of the investigation revolving around the in-flight anomaly encountered on the OA-6 mission on March 22. It is hoped that the extra week will provide engineers with the time needed to ensure the issues encountered on Tuesday’s flight are not part of a larger problem.

Meanwhile, the MUOS-5 spacecraft is secure at the payload processing facility as it awaits integration with the Atlas V 551 launch vehicle at the Vertical Integration Facility outside SLC-41.

“The ULA engineering team is reviewing the data to determine the root cause of the occurrence. The first stage cut-off occurred approximately 6 seconds early; however, the Centaur was able to burn an additional approximately 60 seconds longer and achieve mission success, delivering Cygnus to its required orbit,” Lyn Chassagne with ULA told SpaceFlight Insider.

On Tuesday, an Atlas V 401 rocket lifted the S.S. Rick Husband Cygnus cargo freighter on its way to the International Space Station orbiting some 265 miles (426 kilometers) above Earth.

It appears that the first stage encountered a velocity deficit on ascent.

As was reported on SpaceFlight Now, the rocket’s Centaur upper stage burned for a little more than one minute longer than the originally planned 14 minutes that it was supposed to. In so doing, it compensated for the shortfall in velocity and placed the spacecraft on the correct orbital path.

The Centaur upper stage is powered by a single Aerojet Rocketdyne RL10C-1 engine. A statement issued by the company shortly after the OA-6 launch served to underscore the situation.

“Aerojet Rocketdyne has a long, successful history of delivering payloads to their destination, and our propulsion on this critical resupply mission continued to live up to that legacy,” said Peter Cova, acting vice president of Space Launch Systems at Aerojet Rocketdyne. “Our hardware performed exactly as expected, and all those who worked to ensure 100 percent mission success should be proud of their hard work and dedication. It wouldn’t happen without you.”

The first stage of the Atlas V utilizes the Russian-made RD-180 rocket engine. Produced by NPO Energomash, the RD-180 has become a lightning rod in political circles since Russia’s military actions in Ukraine in 2014.

The fact that the Cygnus spacecraft and its payload of crew supplies, cargo, and experiments brought Atlas’ burden to some 16, 500 lbs (7,484 kg) was not the issue. A similar Atlas V 401 achieved the same goal in December of last year – with no issues.

In fact, for those on the ground, Tuesday’s launch looked to be a textbook Atlas flight with ground controllers ticking-off nominal events all the way uphill. The rocket and its precious cargo left the pad at SLC-41 at the very opening of a roughly 30-minute launch window at 11:05 p.m. EDT (03:05 GMT).

At present, everything appears to be continuing on schedule, with the Cygnus spacecraft set to be berthed to the space station on Saturday, March 26. When it arrives, the Expedition 47 crew will use the station’s Canadarm2 to grapple the soda can-shaped vessel and berth it to the ISS.

When it does take its spot on orbit, MUOS-5 will complete the planned constellation of the U.S. Navy’s Mobile User Objective System as an on-orbit spare.

Colorado-based United Launch Alliance has a busy year currently on schedule for 2016, with 14 flights total set to take place between now and the end of 2016. The flight of OA-6 was the second of two planned flights of Cygnus on the Atlas V. Orbital ATK is now working to have the spacecraft be delivered by the newly re-engined “enhanced” Antares rocket.