Investigators prepare to OK next Pegasus rocket launch

Posted: June 13, 2001

CAPE CANAVERAL, Fla. -- NASA's $85 million HESSI mission designed to study solar flares could be launched next Thursday if engineers can finish their investigation to prove the satellite's ride to space -- an Orbital Sciences Pegasus rocket -- is fit to fly.

File image of Pegasus rocket being carried to launch zone by Orbital Sciences' L-1011 jet. Photo: Spaceflight Now/NASA TV
Launch of the High Energy Solar Spectroscopic Imager has been on hold since the June 2 failure of a modified Pegasus first stage rocket booster that was carrying NASA's X-43A hypersonic test aircraft. The rocket began coming apart and went out of control just seconds into flight.

While the space agency conducts its inquiry into the X-43A launch accident, other engineers have been examining the data collected during the botched flight to see if it is safe to proceed with the HESSI mission.

Investigators are trying to determine if the failure was caused by aerodynamic stresses or something else specific to the combined Pegasus and X-43A vehicle, which would not doom the HESSI launch.

For the X-43A test, only the winged first stage of the Pegasus rocket was used. The stage also featured modifications to its thermal protection, plus a new guidance system and repackaged avionics.

The Pegasus that will loft HESSI is a full three-stage version of the small satellite launcher. The air-launched Pegasus will be dropped from the belly of Orbital Sciences' L-1011 "Stargazer" aircraft 39,000 feet above the Atlantic Ocean about 60 miles east of the Florida coastline. It will take less than 10 minutes to propel HESSI into a planned 373-mile orbit above the planet.

Although NASA won't say what the investigation has uncovered so far, officials appear optimistic they can clear HESSI's Pegasus rocket for launch next week.

On Wednesday, NASA requested a launch date of June 21 on the Air Force-controlled Eastern Range, which provides tracking, communications and safety services for all Cape Canaveral launches.

"We can see the light at the end of the tunnel," NASA spokesman George Diller said. "Based on that, we can at least establish a launch date to plan to. But the caveat is there are still some things that need to be understood."

A series of senior-level meetings is planned at NASA Headquarters, Kennedy Space Center and Dryden Flight Research Center on Monday and Tuesday to review the data and decide whether or not to proceed to a Thursday launch.

Next Thursday's scheduled launch time is 5:00 a.m. EDT (0900 GMT), which comes in the middle of an available window of 4:00 to 5:39 a.m. EDT (0800-0939 GMT), Diller said.

The time is a radical change from the mid-morning window planned on June 7 -- the original launch date. Officials were forced to alter the launch time as a compromise to objections raised by European air traffic control, which had refused to clear a stretch of the Atlantic Ocean for the rocket's second stage to impact.

The controllers said clearing the airspace at that time of the day would adversely affect airline flights to the Azores island chain.

By shifting the launch earlier in the morning, the controversy was averted, NASA said.

Officials had discussed moving the launch to around 2:05 p.m. EDT, but later changed their minds.

Launch managers are facing a June 23 deadline to launch HESSI or else postpone the mission indefinitely to return the Pegasus to its home base of Vandenberg Air Force Base in California for servicing. When another attempt at flight would be available isn't clear given NASA's jam-packed summer launch schedule.

Flight data file
Vehicle: Pegasus XL
Payload: HESSI
Launch date: June 21, 2001
Launch time: 0900 GMT (5:00 a.m. EDT)
Staging site: Cape Canaveral Air Force Station, Florida