Microscopic cracks in a spun graphite tank designed to carry liquid hydrogen fuel in the X-33 rocket plane led to the failure of the tank, built by Utah's Alliant Techsystems, says a NASA report.
A contributing factor in the setback can be summed up in the words of a classic Paul Newman movie, "Cool Hand Luke": "What we've got here is failure to communicate."
The X-33 was to be a half-scale prototype for a vehicle NASA hoped would launch payloads into space at a much reduced cost. Eventually, if all went well, NASA and civilian partners hoped the full-scale version, VentureStar, would replace the Space Shuttle.
The fuel tanks were spun with special machinery at Alliant Techsystems' Clearfield plant, in a project by Alliant and Lockheed Martin. Another Utah connection was that many of the X-33 test flights were to launch from California and land at Dugway Proving Ground in the state's western desert.
According to the General Accounting Office, cost of the X-33 was pegged at about $1.23 billion to the federal government, while industry would pay around $125.4 million. However, the figures might not be as high if the project is not completed because of the tank failure
When the first of two liquid hydrogen fuel tanks was tested on Nov. 3, 1999, it began to come apart. Since then, a team of experts has been investigating the cause. The team includes NASA and Lockheed officials and independent consultants.
Their report, dated May 2000, was released Thursday. An inner sheet in the tank had "microcracking" that let hydrogen infiltrate into the core, leading to the failure, it says.
Attempting to assess the cause of the failure, it concludes:
"A design of this complexity requires high levels of communication, both internal and external to the involved organizations; such communication did not occur in this case."
The design should have been pursued through a building-block design approach, accompanied by an in-depth analysis of risk. "The building-block design approach used did not adequately address the complexity of the system," says the report.
However, the program and the investigation did provide insight into the challenges of building this kind of tank, and provided lessons.
Mark Messick, the Alliant Techsystems program manager for the liquid hydrogen tank program, said the aerospace company remains "very interested" in the technology developed for the spun graphite tanks.
With expertise gained from the X-33 and a prior program, he said, "we have more experience than anyone out there" in the process, and Alliant Techsystems wants to share it with industry.
Asked whether the X-33 is still a viable project, he quoted a NASA manager who thinks the rocket plane will go forward. However, nobody knows whether it will be with the same tank design or with aluminum tanks.
"We overcame so many obstacles and hurdles, we truly pushed the state of the art forward for the whole industry," he said. A developing technology is bound to have problems, Messick said.
"Alliant did not design the tanks. Our role was a build-to-prints relationship," he said. That means Lockheed Martin provided the designs and Alliant used the blueprints to make the tanks.
In the end, he said, both sides would say a lot of design lessons were learned, and Alliant learned about making composite tanks. "This knowledge is an asset," Messick said.
The investigative report bears out that attitude. "The results of the investigation do not invalidate the use of composite materials for cryogenic (super-cold) tanks," the report adds.
"The lessons learned from building and testing the tank and the incident investigation, if applied to composite cryogenic tank technology, should advance the technology and aid in the successful use of composites for cryogenic tanks."
E-mail: bau@desnews.com