United Launch Alliance has successfully launched the MUOS-5 for the US Navy, with the mission beginning with an on time launch on 24th June 2016. The launch window opened at 10:30am EDT (14:30 UTC). This mission took around 3 hours before an announcement of success was made . This is the first Atlas V mission since the near miss, but successfully executed mission deployment of the OA-6 mission sending Orbital ATK’s Cygnus to the ISS. The Atlas V launched in the 551 configuration, a 5-meter fairing, 5 solid rocket boosters and single upper-stage engine, and was the 7th time United Launch Alliance had used this configuration. The first was the launch of New Horizons back in 2006.
This mission was poised to launch the U.S. Navy’s fifth Mobile User Objective System (MUOS-5), which was built by Lockheed Martain. According to Gunter’s Space Page, the stated mass of the MUOS satellites are 6740 kg, and are built on the A2100M bus configuration. The MUOS constellation provides the U.S. Navy a network of orbiting satellites which are able to provide secure and communications for the troops who are in war zones and those who are a part of the mobile military forces. Before this launch, four MUOS satellites in orbit providing communications for troops, and with the filth satellite heading towards its slot in Geostationary Orbit, this satellite will provide a backup communications link for the four orbiting satellites currently at their station keeping points.
MUOS-5 however was originally scheduled for launched on May 5th 2016, but subsequently delayed to today. The delayed was caused by a RD-180 anomaly on the mission which was ahead of this launch campaign. The previous mission, a Resupply Mission heading towards the International Space Station, booked by Orbital ATK, to ferry up the company’s Cygnus spacecraft with science and supplies for the crew at station. The OA-6 mission to the station was a near mission failure due to the shortfall of the RD-180 burn of the first stage flight of the mission, resulting in a 6 second shortfall on the burn. However the mission was saved by the Centaur Upper Stage flight computer acknowledging the shortfall and burning up to a minute longer than planned, a few seconds before fuel depletion.
After the anomaly was noted by United Launch Alliance, management stood down Atlas V from further mission until data and a fix for the issue was made. It was recognised that the anomaly came from the Atlas V’s main propulsion system, the RD-180, and the investigation found that a fuel control valve was at fault on the OA-6 mission. A fix has now been applied to the RD-180 which is set to take MUOS-5 to a Geostationary Orbit (GSO), and all RD-180 engines which the Atlas V will use in upcoming and future missions.
The following was the Mission Highlights for the MUOS-5 launch:
This mission marked Atlas V’s 63rd launch since its inaugural launch in August 2002. United Launch Alliance is also celebrating it’s 108th mission without failure, a feat which no other aerospace company has yet to reach. The next Atlas V launch is tentatively scheduled for late July carrying the NROL-61 in 421 configuration.