Story first posted at 1:21 p.m. EDT

"I don't see any indication of either NASA's side or Lockheed Martin's side to withdraw from the program," said Gene Austin, the X-33 program manager. "We're going to learn from it and move on."

NASA issued a report today outlining likely causes for a composite tank's failure during a test in November.

Austin said a decision whether to press ahead with composite tanks or to switch to an aluminum version should be made by the end of the year. Whether either tank is used, the first flight will likely slip to 2002 at the earliest. The first test flight was originally scheduled for 1999.

Explore the X 33 Virtual 3D Model.
     

Composite fuel tanks would have reduced the weight of the craft, which will be vital later on in single-stage craft attempting to reach Earth orbit.

The wedge-shaped X-33 uses lifting-body technology developed by NASA and the U.S. Air Force in the 1960s and 1970s. Instead of wings, a lifting body uses the shape of the vehicle to provide lift and control. Other design features include an advanced thermal-protection system using metallic tiles and internal structures, such as the fuel and oxidizer tanks, to form the fuselage.

The pilotless X-33 is designed to take off vertically like a rocket, ascend to an altitude of up to 60 miles (97 kilometers) at speeds more than 13 times the speed of sound and land like a conventional aircraft.

So far, NASA has sunk about $912 million and Lockheed Martin about $286 million. A 1999 GAO report cautioned that delays in the X-33 and VentureStar program could delay NASA's decision on whether to upgrade the current shuttle fleet or rely on new launch vehicles. Expensive upgrades to the shuttles could see them flying well beyond 2025.

Austin said work on the craft continues at Lockheed Martin's famed Skunk Works in Palmdale, California. and at Marshall Space Flight Center (MSFC) in Huntsville, Alabama.

"The assembly program is continuing," he said. "We're working on wiring, plumbing and powering up the avionics as if we were further along than we were."

Today's report cites five factors which may have contributed to the failure: liquid hydrogen seeping between the layers of the tank; liquid-nitrogen purge gas pressure; manufacturing flaws; reduced bonding and strength of adhesives; higher-than-expected pressures inside the tank.

"This was a design that pushed the limit of technology and it created a fairly highly complex technical and manufacturing system," said Bob Ryan, the report's lead investigator. "This investigation was an encouraging lesson and it added understanding to our use of composites."

A chain of events that began with the tank's manufacturing process, along with a piece of Teflon tape left inside, led to the adhesive coming undone, thus allowing the layers of the carbon-based tanks to peel like an onion. Microscopic cracks also developed due to the strain placed on the composite material that allowed the liquid hydrogen to penetrate the three layers.

~

Ryan said the time frame for the adhesive's application -- from when it was bonded to the composite material to the time it was cured in an oven -- was too long. The lag caused the adhesive to lose about 50 percent of its bonding power. The piece of tape inadvertently left in the tank also caused the adhesive to come undone.

The 162-page report issued today makes no recommendations about how the project should proceed. It added that current problems with composite tanks do not rule them out for future use in spacecraft.

Also cited in the report was a lack of communication between the space agency and Lockheed Martin during the design and manufacturing process.

"The communication problem was a two-way one," Ryan said. "You have to understand what is being communicated up and down the chain."

Ryan characterized it as a breakdown in communication while working with extremely technical and complicated design processes.

"We're going to make sure we pay a great deal of attention to get the comm. Problems identified and rectified," Austin said. "We'll make every attempt to assure ourselves we don't have the same problems again.

Despite delays and problems with technology associated with the X-33, Austin said the flight-test program would seek the same results of numerous flights with rapid turnaround to prove the system.

Tests will wring out the capabilities of the metallic thermal tiles and the two-aerospike engines powering the craft.

"Our objective remains to fly two times in seven days," Austin said. "I don't see any impact on the flight program whether we go with aluminum or composite tanks."

Current plans call for the X-33 to launch from Edwards Air Force Base in California and land about 450 miles (720 kilometers) away at Dugway Proving Grounds in Utah. Eventually the craft will venture about 950 miles (1,520 kilometers) to land in Montana for more extensive tests of the X-33's systems.