Fuel woes force end to mission

LOS ANGELES – A NASA robotic spacecraft located a Pentagon satellite in space without any help from human controllers, but the mission ended early when the computer-driven craft detected a fuel problem, the mission manager said Saturday.

The experimental DART spacecraft – short for Demonstration of Autonomous Rendezvous Technology – had moved to within 300 feet of the satellite orbiting 472 miles above the Earth but backed off late Friday, about 11 hours into the mission, manager Jim Snoddy said.

The spacecraft was supposed to have maneuvered around the satellite, getting as close as 15 feet, for another 12 hours. After the problem arose, the 800-pound craft began coasting; it will eventually disintegrate in orbit.

“When we started doing precise maneuvers, we started seeing excessive propellant consumption. … It went south pretty quickly,” Snoddy said. “The mission as designed, when it runs out of gas, completes itself.”

There were some navigation errors but no indication of a fuel leak, he said in a conference call. A NASA investigation board will search for the cause of the problem.

Snoddy called the mission a partial success because it demonstrated that an entirely computer-controlled craft could find a satellite in space.

“We’ve done what nobody’s ever tried to do before,” he said. “A lot of things worked well on the ground. The real truth is you have to be perfect in space. … There was obviously something we didn’t model.”

The $110 million mission, classified as high-risk because of its automated controls and relatively low budget, was intended to help lay the groundwork for future projects like robotic delivery of cargo to space shuttles and automated docking and repair between spacecraft in orbit.

The main instrument on the craft was a next-generation combination of optics and electronics called an advanced video guidance sensor. The sensor, which was to have been used to steer DART closer to the satellite, is a more sophisticated version of one tested during space shuttle flights.

The company that built the craft, Dulles, Va.-based Orbital Sciences Corp., said it was disappointed in the outcome but pleased with the first part of the mission.