Rudder Actuator Blamed

The flight of NASA's X-43A has been postponed, due to an incident with the rudder actuator on the booster. On Feb 11, during setup at Orbital Sciences Corporation for testing of the rudder and its actuator, an anomaly caused the actuator to go hard over and hit its mechanical stop, exceeding the torque to which the units were qualified.

Although the actuator may still function normally, it will have to be replaced. A joint government/contractor incident investigation is under way to determine the cause and corrective actions.

Before this incident, the program was considering a delay of the flight to late March to retune the booster autopilot, to optimize its performance based on the latest test data. With the requirement for a replacement actuator, the two activities will now be done in parallel. Planning is now focused on a late-March to early-April flight.

The stack, consisting of the X-43A and its modified Pegasus booster, will be air-launched by NASA's B-52 carrier aircraft at 40,000 feet altitude. The booster will accelerate the experimental vehicle to Mach 7 at approximately 95,000 feet altitude. At booster burnout, the X-43 will separate and fly under its own power on a preprogrammed path. The flight will take place over a restricted Navy Pacific Ocean test range off the coast of Southern California.

NASA admits the X-43A is a high-risk, high-payoff flight research program. Designed to fly at seven and 10 times the speed of sound, and use scramjet engines instead of traditional rocket power, the agency claims the small, 12-foot-long X-43A could represent "a major leap forward toward the goal of providing faster, more reliable and less expensive access to space."

FMI: www.nasa.gov