NASA News Release 96-122
A full-scale segment of a graphite-composite wing designed for a reusable launch vehicle (RLV) was successfully "tested to failure" to determine the maximum load that the wing-box would carry and its mode of failure. Tested at NASA's Langley Research Center, Hampton, Va., the wing broke at twice the design load limit. "Load" is defined as the forces that a component of the vehicle experiences during take-off, landing, and conducting various maneuvers. Design limit load is the maximum load that a component is expected to experience one time during the life of the vehicle. Knowing at what load and how a structural component fails is essential to being able to design a vehicle that will be safe at all expected flight conditions. This is the first structural test of a full-scale component designed and fabricated to validate the use of graphite-composite primary structure for the RLV. The test results validated the design, analysis and fabrication procedure with excellent agreement obtained between the predicted results and the experimental results. The wing-box test component, six feet wide by 10 feet long by three-and-one-half feet deep, was designed and fabricated by a Rockwell International/Northrop-Grumman industry team using a high-temperature graphite bismaleimide composite material. The use of graphite-composites for the primary structure, like the wings, the thrust structure which connects the engines to the vehicle and the intertank which connects the fuel tanks of the RLV together, is essential for a cost-effective launch system that can also meet the weight requirements for a single-stage-to-orbit vehicle. Reusable launch vehicles are being tested by NASA as future spacecraft that can be used in the commercial market as well as for scientific research. It is hoped that RLVs of the future will be designed to lower the costs of research and manufacturing in space. Structural health monitoring sensors were also installed on the test component to verify their use for the RLV. A health monitoring system is one that monitors and records wing-box deflections, strain, temperature, etc. An effective health monitoring system would reduce the need for physical inspections of certain critical components such as the wings or the fuel tanks, and could significantly reduce operation costs and improve launch reliability. Langley responded to requests by its industry partners, Rockwell International and Northrup-Grumman, to accelerate the tests by four months, advancing the time of testing from eleven months to seven months. Langley researchers at the Hampton, Va., Center successfully conducted the above tests ahead of schedule so that the industry partners could include the results in their reusable launch vehicle Phase II X-33 proposal. Three companies are presently bidding on Phase II of NASA's RLV program. NASA will announce the winner of the RLV Phase II competition by July 1.