Lockheed's Advanced Extreme High Frequency Satellite To Reach Intermediate Orbit Within Weeks After One Of Two Propulsion Systems Fails

AEHF To Reach Intermediate Orbit In Weeks
Aug 30, 2010

By Amy Butler 
Over the next few weeks, the U.S. Air Force plans to use one of two thruster systems still functioning on a protected military communications satellite built by Lockheed Martin to reach an intermediate orbit after failure of a liquid apogee engine on the spacecraft.

The Aug. 14 launch of the Atlas V carrying the first Advanced Extremely High Frequency (AEHF) satellite, estimated to cost more than $2 billion, toward geosynchronous orbit was nominal. But the spacecraft’s liquid apogee engine (LAE) failed prematurely, and this system has been rendered useless for the 22,000-mi. journey into its proper orbit (Aerospace DAILY, Aug. 27).

Engineers at the Air Force Space and Missile Systems Center — which oversees AEHF procurement — Lockheed Martin and The Aerospace Corp. are “assessing a modification to the original orbit-raising strategy that would use the other two healthy propulsion systems” on the satellite, according to the Air Force’s Military Satellite Communication Office. These are the reaction engine assembly (REA) and Hall Current Thruster (HCT) electric propulsion systems.

The REA, which will be used to raise the satellite into the intermediate orbit, is not as powerful as the LAE, “so the operation is anticipated to take longer than the original orbit-raising plan,” the Milsatcom officials say. “This activity to move to the intermediate orbit should be accomplished in the next few weeks.”

Once that orbit is reached, the Milsatcom officials say they will then head to GEO. They declined to say how, specifically. “It is going to take longer to get AEHF-1 to GEO, but it will get there,” one Air Force official says. “The final plan will have to use a combination of the smaller 5- and 0.2-lb. thrusters in conjunction with the Hall Current Thrusters to reach GEO.”

The alternate propulsion strategy, however, will require tapping into the satellite’s hydrazine tanks for fuel; this is on the spacecraft for station-keeping. “We’re still examining the net fuel required for this [journey to GEO], the time required and the steps to get there,” the Air Force official says. “But in the end, we expect a nominal mission duration,” meaning the operation should not significantly lessen the useful life.

Once Air Force officials determine the root cause of the LAE failure on the first AEHF, the “implication to other satellites with similar propulsion systems will be analyzed and addressed,” the Milsatcom officials say. The AEHF core is built from Lockheed Martin’s A2100 satellite design, as will be the upcoming GPS III.

One Response to “Lockheed's Advanced Extreme High Frequency Satellite To Reach Intermediate Orbit Within Weeks After One Of Two Propulsion Systems Fails”
  1. any latest update regarding the satellite.

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