...Rocstar couples multiple domain-specific simulation packages and disparately discretized domains and provides several simulation-supporting services including conservative and accurate data transfer, surface propagation, and parallel I/O. Rocstar is MPI parallel and routinely executes large simulations on massively parallel platforms. Rocstar was originally developed at the University of Illinois Center for Simulation of Advanced Rockets (CSAR) under Department of Energy ASCI funding. Ongoing development of Rocstar is conducted by Illinois Rocstar LLC with company IR&D and continued DOE SBIR funding.