Monday, August 30, 2010

Air Force confident satellite will reach final orbit, eventually


A $2 billion military communications satellite will take about three times longer than planned to reach its final orbit because of a premature engine shutdown, and the problem could delay launches of follow-on spacecraft, the Air Force said today.

Backup plans to raise the first Advanced Extremely High Frequency satellite to geosynchronous orbit have already begun using smaller thrusters.

Air Force officials are confident those thrusters and an electronic propulsion system will get the spacecraft where it needs to go without shortening its 14-year design life.

"I'm extremely confident that we're going to be able to do it," said Dave Madden, program director for the Space and Missile Systems Center's Military Satellite Communications Systems Wing in Los Angeles.

The satellite known as AEHF-1, built by Lockheed Martin Corp. and Northrop Grumman, launched Aug. 14 atop a United Launch Alliance Atlas V rocket and separated without trouble.

The first of three burns by the spacecraft's liquid apogee engine (LAE) was attempted the next day, but the engine shut down after failing to reach the proper acceleration, Madden told reporters in a teleconference today.

A second attempt two days later achieved the same result. The engine, which burns hydrazine and nitrazine tetroxide, is designed to produce 100 pounds of thrust.

"We believe the LAE is unusable, and at this point we have no plans to fire that engine again," Madden said.

The Air Force on Saturday began a series of burns using six smaller, five-pound thrusters to raise the spacecraft to an intermediate parking orbit of about 590 miles, reducing atmospheric drag and the chance of debris collisions.

The Air Force now expects AEHF-1 to take 10 or 11 months, instead of three months, to reach its final orbit more than 22,000 miles above Earth. Once there, another three to four months of system tests will follow.

Launch of the $6.5 billion AEHF program's second spacecraft was targeted for February, but that won't occur until a root cause of the engine shutdown is determined, Madden said. Its hoped the cause could be confirmed in three to four weeks.

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