Rocket Problem Delays Test Flight of NASA Hypersonic Aircraft

Feb. 18–EDWARDS AIR FORCE BASE, Calif. — The flight test of the unmanned hypersonic X-43A is being delayed a few weeks to repair damage to its booster rocket and to improve its piloting software.

Originally looking to conduct the test this month, the X-43A team said the test will occur no earlier than late March or early April to allow time for autopilot improvements and to replace a damaged rudder actuator on the booster rocket that will carry the experimental aircraft.

“The flight of NASA’s X-43A has been delayed approximately one month due to autopilot software changes,” said Joel Sitz, X-43A project manager at the NASA Dryden Flight Research Center. “During recent hardware testing required to confirm the final autopilot modifications, a flight actuator was inadvertently damaged and will be replaced. A spare flight actuator is being prepared for integration into the booster.”

The actuator was damaged during hardware testing last Wednesday at Orbital Science Corp.’s Chandler, Ariz. plant. Orbital is modifying one of its Pegasus space boosters to carry the X-43A to its test speed of approximately 4,900 mph and its test altitude of 95,000 feet.

Although the actuator may still function normally, it will have to be replaced, officials of the National Aeronautics and Space Administration said. A joint government/contractor incident investigation is under way to determine the cause and corrective actions, a NASA statement said.

The program is testing the ultra-high-speed, ultra-high-altitude scramjet engine, which could be used in future space launch vehicles and for high-speed military and civilian aircraft.

Scramjets pull oxygen for combustion from the atmosphere rather than carry the extra weight of its own oxygen as a rocket does. By not having to carry oxygen, a spacecraft can save fuel weight and carry more equipment.

During its test flight, the Pegasus booster/X-43A stack will be released over the Pacific Ocean by a modified B-52 bomber. After a brief free fall, the Pegasus booster engine will ignite and push the X-43A to its test speed and altitude.

As the booster engine burns out, the X-43A will separate and fire its scramjet engine for about 10 seconds. The engine will then shut down and the craft will perform a set of preprogrammed maneuvers before crashing into the ocean.

The X-43A will not be recovered.

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