The Aug. 14 launch of the Atlas V carrying the AEHF was nominal. But the liquid apogee engine (LAE) on the spacecraft failed during two firing attempts, one each on Aug. 15 and 17. This system, which was to provide 100 lb. of thrust, is useless for the journey 22,000 mi. into orbit.
The first AEHF satellite was expected to reach its testing position at 90 deg. W. Long. in geosynchronous orbit in November, three months after launch, says Dave Madden, director of the Air Force’s military satellite communications program office. Now, however, a series of engine burns will be required and it will not reach position for 10-12 months, Madden says.
The LAE was to be burned three times, raising the orbit from 230 km. (143 mi.) to 19,000 km. six days after launch. The Hall Current Thrusters (HCT), xenon-fueled electric thrusters producing 0.6 lb. of thrust and designed for in-orbit station-keeping and maneuvers, were to be used for about 90 days to reach the test position.
Now Air Force officials plan a four-phased orbit-raising strategy. First, they will increase the satellite’s perigee to reduce drag on the spacecraft from the Earth’s atmosphere.
For this phase, which began Aug. 29, the Air Force is using the third propulsion system on the satellite, a reaction engine assembly (REA), which has six 5-lb. and 12 0.2-lb. thrusters. This system was designed for use in maintaining yaw attitude control and for in-orbit operations. The goal is to reach an intermediate “parking” orbit of 950 km.
“Satellite performance before, during and after this burn was nominal,” Madden says of the first 40-min. firing.
In the next three phases of the orbit-raising plan, more REA apogee burns will be conducted to better than double the current perigee. HCTs will then be used at apogee and to conduct continuous maneuvers to reach the final orbital slot.
Madden says he expects no impact to the satellite’s planned design life of 14 years. The satellite’s design allows for the RAE to tap into the LAE’s hydrazine fuel store, Madden says. “We basically got lucky,” he says. “We put enough fuel onboard to pretty much fire those thrusters continuously. We [will] optimize the burns to only fire them when it is most effective in orbit-raising.”
So far, the Air Force will not have to tap into fuel for on-orbit station-keeping or maneuvers to meet operators’ needs. “They may be willing to give up life to get there faster, and then there are some things we can do differently,” Madden says. Air Force Space Command chief Gen. Robert Kehler says the Milstar constellation “is still in good shape, [so] it doesn’t much trouble me that it will take a little bit longer to get to orbit.”
It is unclear how this will impact Lockheed Martin. The company is on a cost-plus-incentive-fee contract, originally a $2.9-billion deal for the first two AEHF satellites and a ground system. Northrop Grumman is the primary payload provider. The contract was amended to include a third satellite and overruns incurred by poor government management in developing cryptographic equipment for the satellite. Cost was added, too, when a second round of thermal vacuum testing was required because a faulty set of reaction wheels was installed initially on the satellite. The contract’s current scope is estimated at $4.8 billion, but Lockheed Martin’s estimate at completion was $6.5 billion, before the recent in-orbit mishap.