A major component of the X-33 advanced technology demonstrator -- one of its twin composite liquid hydrogen fuel tanks -- soon will undergo a series of pressure and stress tests at NASA's Marshall Space Flight Center in Huntsville, Ala.
Tests are to begin this week on the first of two 4,600-pound graphite epoxy tanks, each designed to carry approximately 29,000 gallons of rocket fuel -- liquid hydrogen -- at -423 degrees Fahrenheit. The twin hydrogen tanks form the flanks of the X-33 vehicle and comprise roughly half its airframe.
The X-33 is being developed in a partnership between NASA and the Lockheed Martin Skunk Works, Palmdale, Calif. The vehicle is a half-scale, sub-orbital technology demonstrator of a proposed future reusable launch vehicle Lockheed Martin calls "VentureStarTM." Managed for NASA by the Marshall Center, the X-33 program is designed to demonstrate advanced technologies that will dramatically increase launch vehicle reliability and safety, while lowering the cost of putting a pound of payload into space from $10,000 to $1,000.
The first 29-foot tank has been placed into a structural test facility in the West Test Area at the Marshall Center where it will receive cryogenic, or very low temperature, propellant and structural loads and pressure cycles over a four to six-week period. External loads also will be applied to the tank to simulate pre-takeoff, takeoff, ascent, return and landing conditions.
"These are the largest composite cryogenic tanks ever built," said Cleon Lacefield, Lockheed Martin Skunk Works vice president for X-33/VentureStarTM. "Not only will they hold the super-cold liquid hydrogen, but they also will provide the structural strength of the vehicle and are shaped to conform to the X-33's body. Obviously, designing and assembling these tanks was quite a challenge, and our NASA and industry team did a great job."
"Being able to build key vehicle systems and tanks out of lightweight yet strong composites is an enormous step toward getting us launch vehicles that will support routine and low-cost access to space," said Gene Austin, NASA X-33 program manager, of the Marshall Center. "Short of the flight series, this month's testing of the hydrogen tanks and also our aerospike engines marks the most significant and exciting stage of the X-33 program."
Before testing the tank with liquid hydrogen, it will be partially filled with liquid nitrogen and then pressurized to test its structural integrity. Once nitrogen testing is complete, Marshall engineers will fill the tank with liquid hydrogen to simulate internal pressure loads.
Crews have completed assembly of the X-33's second liquid hydrogen tank. The tank is expected to arrive at Marshall in early October, with testing to begin later this year.
When the Marshall Center tests are complete, the tanks will be shipped to Lockheed Martin Skunk Works' X-33 assembly facility in Palmdale, Calif., where they will be installed into the vehicle.
Alliant Techsystems in Clearfield, Utah, fabricated the composite components for the tanks. A joint Lockheed Martin-Alliant team assembled the tanks in an enormous autoclave at Lockheed Martin Missiles and Space, Sunnyvale, Calif.
The vehicle is scheduled to conduct flight tests beginning in summer 2000. It will fly faster than 13 times the speed of sound and at an altitude of 60 miles to prove its technologies and systems.
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