NASA Langley News Release 97-104a
August 29, 1997

With a loud snap, NASA Langley deliberately "broke" a 22-foot-by-10-foot part being developed for NASA's next-generation launch vehicles to validate the design, fabrication and analysis tools used in its construction.

Langley conducted the tests Aug. 28 on the full-scale technology segment of a composite intertank structure for the Advanced Space Transportation program.

Dr. Wayne Sawyer of the Thermal Structures Branch said that a full-scale cylindrical section of an intertank reusable launch vehicle (RLV) shell, including five ring frames, was selected as the test component. The test article is 10 feet long, about 22 feet wide and represents a nearly 90-degree section of an RLV intertank. The shell and ring frames are made from an advanced high-temperature graphite/bismaleimide composite. The test article was designed and fabricated by industry teams in cooperation with NASA.

The article was tested by subjecting it to uniform compression loads to simulate the vehicle critical loading condition experienced during launch. One end of the test article was attached to the NASA Langley vertical test support structure that served as a stiff reaction surface. The other end received a uniform pressure load applied by 21 hydraulic jacks equally spaced along the circular arc of an aluminum ring frame of the test article.

The ring frame acted as a test fixture to properly introduce the loads into the composite structure. Each load jack was individually controlled to provide equal loads to the test article. The whole structure was supported from the floor by stiff frames attached to the ring frames and the test fixture.

"Although the test component failed at a lower load than expected - at 500,000 pounds rather than at 800,000 pounds - we learned a lot from the test," said Sawyer. "We learned of some shortcomings and improvements needed in the fabrication and of the need to continue to look at the attachment of stiffeners to the skin. This is one of the steps in coming up with a better structural part."

For the United States to remain competitive in launching spacecraft, it is necessary to develop a launch system that is lightweight, robust, requires little maintenance or inspection, and has low-cost operations as part of its design features. Future launch systems must also greatly reduce the cost required per pound to put a pound of payload into orbit. The Advanced Space Transportation Program is developing various ways of achieving that goal.

Studies have shown that composite primary structures are a necessary part of the development required and composite intertanks are an important part of that development.

Considerable advancements have been made in composite primary structures for the design of an RLV through cooperative agreements between NASA and several industry teams. In these agreements, unique technical issues have been addressed for the major structural components of an RLV --- intertank, wing and thrust structure.