Software or hardware changes?

"We're finding that there are small things all along the line that contributed to what happened. There's not a single, total event," said Robert Hughes, who chairs the X-43A Mishap Investigation Board now looking into the failed flight. He is from NASA's Marshall Space Flight Center in Huntsville, Alabama.

Hughes told SPACE.com that he hopes the X-43A mishap findings, including "where-to-go-from-here" recommendations, can be wrapped up in late December or early January. A formal report might be released in late January, he said.

"When you go into a failure investigation, you are hoping that you'll find something gross -- like somebody taking a picture with a lens cap still on the camera. And that is something that we didn't see," Hughes said.

Vincent Rausch, program manager for the Hyper-X Program here at NASA's Langley Research Center, said a second X-43A vehicle is at NASA's Dryden Flight Research Center at Edwards, California. A third craft is in production. Given the mishap board's findings and recommendations, the second craft could fly in 2002, he said.

Rausch said that he hoped a return to flight would be possible making software changes as opposed to a hardware fix. A different launch altitude, release speed, and trajectory is likely to be part of the second test hop of an X-43A. Doing so "would buy back less risk in the boost" phase of the flight, he told SPACE.com.

Intricate investigation

Hughes has been involved in more than 20 different failure investigations, including the Challenger shuttle tragedy in January 1986. The X-43A mishap team has been busy at work for over 25 weeks -- a task that the board leader first envisioned might take on the order of 120 days. The mishap investigation team includes representatives from a number of NASA centers and industry contractors.

"Putting the pieces together on this -- this is probably one of the more intricate and a little more difficult investigations that I've been on," Hughes said. "It has been a long haul."

Good data was received from both the well-instrumented booster and X-43A research vehicle prior to destruction and ocean impact.

Many witnesses of the June X-43A flight point to the Pegasus XL-derived booster as the clear culprit of the failure.

Significant changes were made to the Pegasus to meet the unique requirements of the Hyper-X program by the booster's builder -- Orbital Sciences Corporation (OSC) of Chandler, Arizona.

For example, the rocket's second and third stages were eliminated, as was the fairing, which is normally used to protect satellite payloads. The X-43A research vehicle and its adapter rode atop the front end of a specially configured first stage solid rocket motor.

Additionally, a newly developed thermal protection system protected the Pegasus composite structures against severe heating loads associated with low-altitude hypersonic operations. Other modifications were made in upgrading first stage guidance hardware and repackaging avionics gear to assure stability of the rocket as it sped toward hypersonic flight conditions.

Open and shut case

But given that pieces broke off the Pegasus, why not an open and shut case?

"We would have loved to say that," Hughes said. What caused the pieces to fall off in the first place has become tough to pin down, he added.

"The launch vehicle was not considered to be the higher risk element. The higher risk element, of course, was the Hyper-X vehicle. So there was not as much depth put on the launch vehicle. But there wasn't inattention. And that's what we're finding. It is not inattention. It's things that you have to really weed way down to find," Hughes said.

Rausch said that there was difference enough between the standard Pegasus and the rocket attached to the X-43A that OSC "treated [their booster] as a first flight article."

"There are significant differences, and there are significant similarities as well. To the casual observer it looks like an identical vehicle. When you get to the details, it's not identical," Rausch said.

Common threads

Testing at Langley has been underway, Rausch said, to go back and validate the aerodynamics of the Pegasus/X-43A "stack" - especially during the transonic portion of the flight. Transonic refers to the aerodynamic flow or flight conditions at speeds near the speed of sound.

Drawing upon on his past investigations, Hughes said there are common threads in why things fail. "Communications could always be better. There has to be lateral and vertical communications between people in a project. It has to go both ways," he said.

Other common threads deal with funding, and decisions that are based on monies available. Also, not having the right people at the right time can make a difference, Hughes said.

Rausch said that the reasons behind the loss of the X-43A were not obvious. "What we're finding is pretty obtuse," he said.

Mach trial

The X-43A is one of a trio of test vehicles to be flown within NASA's $185 million Hyper-X program. The three vehicles are being provided by Micro Craft, Inc., of Tullahoma, Tennessee.

The June test was to fly the X-43A to a blistering mach 7 (seven times the speed of sound), or almost 5,000 miles (8,045 kilometers) per hour. The craft carried a supersonic-combustion ramjet engine, also tagged as a scramjet. As initially scripted, the Hyper-X program calls for the second X-43A to also reach the same speed, while a third craft would zip to mach 10.

Sucking in the atmosphere as it goes, the X-43A combines that blast of air with a small amount of hydrogen carried onboard. The hydrogen, blended with the incoming oxygen, is then combusted and pushes the vehicle to high-mach speeds.

NASA's Hyper-X program is geared to help build future generation space launchers. These next generation boosters are designed to lower the cost and decrease the operational headache of accessing Earth orbit.

"We continue to learn that when you push the boundaries of flight, you get surprises," Rausch said. "We're all disappointed that we had a failure. But sometimes you learn more from failures than you do from successes," he added.

"It's an exciting program and we're going to fix this bugger and go out and fly it again," Rausch said.