X-43A mishap investigation update

The board investigating the June 2 X-43A mission loss is
continuing to meet at the Orbital Sciences Corp. facility in
Chandler, Ariz., where the Pegasus-derived booster rocket used with
the X-43A was built.

The X-43A mission, first in a series of three, was lost
moments after the X-43A and its booster rocket were released from the
wing of the B-52 carrier aircraft. Following booster ignition, the
combined booster and X-43A experienced a structural failure and
deviated from its flight path. The mission was then deliberately
terminated.

Robert W. Hughes, the board chairman from Marshall Space
Flight Center, has said that the root cause of the mishap is still to
be determined. The mishap investigation team includes representatives
from five NASA centers including Dryden, Langley, Marshall, Goddard
and Kennedy, as well as the primary X-43A mission contractors,
Orbital Sciences Corp. and Microcraft.

Hughes stressed that the investigation team was working to
fully understand the causal relationship and emphasized that the
solution might involve several contributing causes rather than a
single cause. He also pointed out that when a single cause for a
mishap is not forthcoming, the difficulty of the investigation
becomes significantly more complex because interrelationships of many
events and data must be firmly understood to assure that all of the
initiating causes are understood. Hughes also emphasized that the
investigation team “is composed of the brightest and best experts in
their fields” and that he has the highest confidence that a probable
cause will be found.

To date, the team has established a fault tree of several
hundred possible or contributing causes that are being systematically
investigated. Approximately 70 percent of these faults have been
eliminated from consideration. The majority of the remaining faults
are in the booster vehicle control arena, Hughes explained.

The X-43A is designed to be the first scramjet-powered
vehicle, capable of attaining speeds as high as Mach 10. NASA’s
Langley Research Center at Hampton, Va., leads the X-43A program,
with flight operations conducted by NASA Dryden, Edwards, Calif.
Micro Craft, Inc., of Tullahoma, Tenn., built the 12-foot-long X-43A
vehicle.