Pegasus XL (modified)
Launch vehicle Pegasus XL (modified)
Launch site (Edwards Air Force Base, California, USA)
Date/Time 2001-06-02
Description First stage total failure
Cause n/a
Payload X-43A (experimental plane, NASA)
Desired orbit n/a (suborbital)

October 2001: The board studying the loss of the first X-43A mission on 2 June 2001 expects to find more than one factor responsible for the loss, said Robert W. Hughes, the board chairman from NASA’s Marshall Space Flight Center (MSFC).

"The bulk of the board effort remaining revolves around fully understanding the critical elements of the control system and vehicle aerodynamics," Hughes said. Extensive wind tunnel testing with the vehicle model and functional testing of the launch vehicle control system has begun. Major analytical assessments have been completed and others are in process to provide and assess the collected data.

The team has closed all but one branch of the more than 600-element fault tree that was developed to assist in the investigation of the mishap. The remaining branch deals with the launch vehicle control system, aerodynamics and control elements, Hughes said.

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

The launch vehicle was one of three Pegasus-derivative rockets built by Orbital's Launch Systems Group for the NASA's Hyper-X programme.

In this specialised application, the Pegasus rocket's second and third stages have been eliminated, as has the payload fairing, which is normally used to protect satellite payloads. Instead of being encapsulated in a payload fairing, the X-43A research vehicle and its adapter ride atop the front of a specially configured Pegasus first-stage solid rocket motor.

A newly developed thermal protection system protects the Pegasus composite structures against severe heating loads associated with lower-altitude hypersonic operations. Other modifications to Pegasus include upgraded first stage guidance and an avionics repackaging that permits ballasting of the booster for hypersonic flight conditions up to Mach 10.

Launch Failures Chronology