The latest release of the Optimal Trajectories by Implicit Simulation (OTIS4) allows users to simulate and optimize aerospace vehicle trajectories. With OTIS4, one can seamlessly generate optimal trajectories and parametric vehicle designs simultaneously. New features also allow OTIS4 to solve non-aerospace continuous time optimal control problems.

The inputs and outputs of OTIS4 have been updated extensively from previous versions. Inputs now make use of object-oriented constructs, including one called a metastring. Metastrings use a greatly improved calculator and common nomenclature to reduce the user’s workload. They allow for more flexibility in specifying vehicle physical models, boundary conditions, and path constraints. The OTIS4 calculator supports common mathematical functions, Boolean operations, and conditional statements. This allows users to define their own variables for use as outputs, constraints, or objective functions.

The user-defined outputs can directly interface with other programs, such as spreadsheets, plotting packages, and visualization programs.

Internally, OTIS4 has more explicit and implicit integration procedures, including high-order collocation methods, the pseudo-spectral method, and several variations of multiple shooting. Users may switch easily between the various methods. Several unique numerical techniques, such as automated variable scaling and implicit integration grid refinement, support the integration methods.

OTIS4 is also significantly more user friendly than previous versions. The installation process is nearly identical on various platforms, including Microsoft Windows, Apple OS X, and Linux operating systems. Cross-platform scripts also help make the execution of OTIS and post-processing of data easier.

OTIS4 is supplied free by NASA and is subject to ITAR (International Traffic in Arms Regulations) restrictions. Users must have a Fortran compiler, and a Python interpreter is highly recommended.

This work was done by John P. Riehl, Waldy K. Sjauw, and Robert D. Falck of Glenn Research Center and Stephen W. Paris of Boeing Phantom Works. For more information, download the Technical Support Package (free white paper) at under the Software category.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center
Innovative Partnerships Office
Attn: Steve Fedor
Mail Stop 4–8
21000 Brookpark Road
Ohio 44135.

Refer to LEW-18319-1.

NASA Tech Briefs Magazine

This article first appeared in the April, 2010 issue of NASA Tech Briefs Magazine.

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