NASA’s Glenn Research Center (Cleveland, OH) and Boeing employees have won the 2008 NASA Software of the Year Award for the development of a general-purpose program used to perform trajectory optimization and performance studies for a wide variety of vehicles including aircraft, rockets, satellites, and interplanetary vehicles. The Software of the Year Award recognizes developers of exceptional software created for or by NASA and owned by NASA.
The team developed Optimal Tra - jectories by Implicit Sim ulation, version 4 (OTIS4), which utilizes state-of-the-art numerical integration and optimization technologies to predict how a vehicle will perform or to determine how best to fly it. Data generated by the program allows a variety of studies to be accomplished including vehicle and sub-system design trades, guidance studies, error analyses, and mission planning.
With OTIS4, users can seamlessly generate optimal trajectories and parametric vehicle designs simultaneously. Flight paths can be generated with respect to any of the major bodies in the solar system. In addition, OTIS4 can be used to solve non-aerospace continuous time optimal control problems.
OTIS4 simulates the trajectory performance of a wide variety of vehicles. Primarily a point mass, three-degree-of-freedom (3DOF) simulation program, OTIS4 has options that allow six-degree-of-freedom (6DOF) simulations. The user inputs the vehicle models; there are no embedded, vehicle-specific aerodynamic or propulsion models. OTIS4 allows progressively more detailed simulations as the vehicle and mission design advance.
OTIS4 provides two general modes of operation: explicit trajectory integration, and optimization using either explicit or implicit integration. A calculator that recognizes commonly used mathematical functions, operators, and precedence rules enables the user to compute new quantities needed to resolve a specific trajectory problem. An innovative method for constructing constraints between phases of a simulation greatly expands the range of problems that OTIS4 can solve and eliminates a major source of user error by creating a mathematically correct implementation of transphase constraints.