Determining an effective structural design of a launch vehicle is critical to both mission success and crew safety. In order to evaluate the adequacy of a launch vehicle's structural design, the ascent loads experienced by the vehicle must be determined. Computation of the ascent loads is a complex, multi-disciplined undertaking that involves an assessment of both natural and induced environments. Currently, ascent loads are calculated primarily using a somewhat restrictive constant Mach number squatcheloid approach. A method to compute the ascent loads of a launch vehicle through a direct coupling of the six-degree-of-freedom trajectory simulation with a time correlated flexible body simulation of the structure is proposed. Load dispersions due to the statistical uncertainties associated with both environmental effects (e.g., winds) as well as vehicle uncertainties (e.g., thrust misalignment) may be assessed directly from a set of Monte Carlo runs of the synchronized trajectory and loads simulations. The Phase I research is directed at developing the necessary algorithms and providing a proof-of-concept simulation. During Phase II, a complete modular computational framework will be developed that will integrate the 6DOF trajectory tools with the loads prediction software, allowing for a more accurate and unified loads analysis of the vehicle. POTENTIAL COMMERCIAL APPLICATIONS (LIMIT 150 WORDS) The most obvious non-NASA application for this technology is the commercial satellite launch industry. Proposed commercial reusable launch vehicles have the potential to dramatically lower payload-to-orbit costs. This proposed analytical process could enhance such vehicles by producing more optimal structural designs and reducing the potential for launch failure. The proposed technology could also be adapted to augment existing simulations of various mobile military assets such as a planes, tanks, or guided missiles, thus increasing the fidelity of the computed loads for these systems as well. POTENTIAL NASA APPLICATIONS (LIMIT 150 WORDS) If the proposed computational approach for ascent loads is fully developed, NASA will gain an important tool for the accurate prediction of launch vehicle loads. Clearly, NASA?s 2nd Generation RLV design must be structurally efficient in order to meet program goals. This will require accurate knowledge of vehicle loads in order to eliminate excess conservatism without jeopardizing safety. Similarly, if the Shuttle is to continue flying for many years into the future, more precise knowledge of the dynamic loads which occur during ascent may be required for future fracture and reliability analyses of the vehicle.
