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Space soldiers save satellite from FLAMING DEATH

The little engine that could rescues $2bn military bird

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Enter the unrehearsed understudies

The team then sealed up the LAE's tanks, which had the advantage of safety but which also kept about 1,000 pounds of oxidizer bottled up, adding to the vehicle's weight.

With the LAE unusable, Madden and his team turned to the two other thrusters available to them: hydrazine-fueled reaction engines (REAs) and extremely low-thrust xenon-fueled Hall Current Thrusters (HCTs), which pumped out a miniscule 0.05 pounds of push.

If the comparatively powerful REAs could get the vehicle out of its unstable orbit relatively quickly, the HCTs – weak as they may be – had one tremendous advantage that could save the mission: they could be fired for thousands of hours with no ill effects.

The team needed to work fast, seeing as how the vehicle was losing about three miles of altutude per day, and its 140-mile-or-so perigee took it through a band of dangerous orbiting space junk. "That's a pretty nasty area," says Madden.

SV-1 orbital adjustments

What a long, strange trip it's been (credit: Air Force Magazine – click to enlarge)

On August 29, the team fired up the REAs – which had been intended to stabilize the satellite, not change its orbital location – and by early September the vehicle had been nudged into a far safer perigee of 600 miles. By September 22, the perigee had risen to over 2,900 miles.

It was then the HTCs turn. One problem, however: the HTCs require electricity to operate, and at this altitude the vehicle was encountering radiation from the Van Allen Belts, radiation that could damage the satellite's solar-power panels, source of the HTCs' needed electricity.

The team plotted a course to get through the Van Allen Belts as quickly as possible – and they made it with little or no damage to the solar panels, which would be needed to power the AEHF satellite during its 14-year planned mission.

The HTCs continued firing, modifying the vehicle's orbit for 10 to 12 hours per day from October until the next June. Since they had never been intended for such use, Madden and his team continued to learn about their peccadilloes. "They're like a finicky old car," he said, "one that you’ve got to constantly adjust to get it to optimize. There’s no instruction manual for how to do that. It’s basically an art."

After boosting the perigee, the final step was to nudge the apogee down from its top altitude of 32,145 miles while continuing to boost the perigee up to the required geosynchronous altitude. The perigee reached its geosynchronous-altitude goal in early August, and the apogee matched it in on October 24.

At that point, the AEHF satellite was released from the SV-1, and an extensive "How y'doing?" checkout period of all its systems began. The Air Force now says that the communications satellite will be operational this March.

"All of the telemetry we're getting on the vehicle says we didn't violate any parameters," Madden says. "Our solar panels are doing great. We didn’t do any damage that would hurt us in full operation. We've got a full mission life planned for this vehicle."

SV-2 is planned for launch this April. Needless to say, there has been quite a bit of investigation of its LAE design since the SV-1's choked on August 17, 2010. ®

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