In the late 1980s, the launch community was investigating ways to provide heavy-lift capability with low launch costs and fast responsiveness. To help identify the factors that would achieve these goals, Aerospace developed the Operations Design Model.
Based on detailed studies of U.S. and international launch systems, the Operations Design Model used algorithms to estimate the recurring operations requirements, staffing needs, and cost for any particular expendable launch vehicle design. Inputs to the model included the size and mass of the vehicle, the kinds of subsystems involved, the safety factors to be implemented, planned level of certification testing, and other parameters related to design and development. The introduction of the model helped replace the "soft" analyses that were typical of the time with a more scientifically based methodology.
Later, during the National Aerospace Plane program, the Operations Design Model was upgraded to make estimates for reusable launch systems. Many in the program believed that because the plane would be a one-stage, runway-based vehicle that used air-breathing engines, it would have short turnaround times and relatively little maintenance between flights—similar to airliners or jet fighters. In fact, the Operations Design Model demonstrated that factors such as operating margins, thoroughness of certification testing, and technology maturity were far more significant than vehicle configuration and take-off mode.
The Operations Design Model has since become a critical piece of Aerospace's launch vehicle design methodology and was most recently used in the Operationally Responsive Spacelift Analysis of Alternatives for Air Force Space Command.