Linear Coupled Loads Analysis

Accurate determination of a structural component’s dynamic response in a coupled system subject to external forces requires what is commonly known as a coupled loads analysis (CLA). For launch vehicle/payloads, CLAs are utilized in design assessments and in the final structural certification for flight. These analyses entail the prediction of payload response due to transient and quasi-static forces including main engine thrust and side-loads, ground winds, solid rocket motor thrust build-up, ignition over-pressure pulses, vehicle pad separation, aerodynamic loads, gusts, buffet, staging, and transients due to engine startups and shutdowns.

ASD engineers have extensive experience with linear CLAs, beginning with the early development of the Space Shuttle Orbiter cargo integration function and inclusive of multiple expendable launch vehicles. All ASD CLAs are executed utilizing NASA/industry accepted system level component modal synthesis techniques and time history integration methods. All component time history recoveries are performed via the accurate “modal acceleration” method. ASD has the capability of incorporating multiple forms of damping, from system modal level definition of damping, component level definition of damping, through hybrid and/or combinations for the damping definition.

ASD CLA experience and expertise have been incorporated into our commercially available ASD/CLAS software tool. ASD/CLAS has set the industry standard for efficient, accurate, and fast turnaround linear and nonlinear CLAs and is licensed by major contractors. For example, Lockheed Martin which has utilized ASD/CLAS on linear, nonlinear, and variational (parametric) design and mission critical loads cycles, including the Space Shuttle Program.

ASD has conducted well over 2000 linear CLAs for our clients which include large scale variational (parametric/sensitivity) coupled loads analyses each involving 100s of individual CLAs in order to characterize payload environments as a function of payload's mass, C.G., and frequencies. (see Minotaur under Case histories)