Ground Contact Modeling for the Morpheus Test Vehicle Simulation

Luis Cordova L-3 Communications, Houston, TX 77004 Luis Cordova Morpheus Simulation Technical Lead L-3 STRATIS Division NASA JSC Engineering Directorate Software, Robotics, and Simulation Division Spacecraft Software Systems Engineering Branch The Morpheus vertical test vehicle is a robotic lander being developed at the NASA Johnson Space Center (JSC) to test autonomous landing and hazard detection technology. The existing ground contact simulation model for this project was not very realistic and needed improvement. The first development cycle added capability to define vehicle contact points (CP) and to keep track of their states in the lander reference frame (LFRAME). These states are used with a spring damper model to compute a CP contact force. The lateral force is then overwritten, if necessary, by the Coulomb static or kinetic friction force. The second development cycle added capability to use the PolySurface class as the contact surface. The class can load terrain data in STL (Stereo Lithography) format for use in line of sight (LOS) intercept computations. A polygon frame (PFRAME) is computed from the intercept facet normal and used to convert the CP state to PFRAME. Two flat plane tests validate the transitions from kinetic to static and vertical impact. The hazard terrain test and a graphical display program were used to visually validate the model. The improved model is numerically inexpensive, robust, and produces results that are reasonable.