The Integrated Systems Test of an Airbreathing Rocket (ISTAR) project was a flight demonstration project initiated to advance the state of the art in Rocket Based Combined Cycle (RBCC) propulsion development. The primary objective of the ISTAR project was to develop a reusable air breathing vehicle and enabling technologies. This concept incorporated a RBCC propulsion system to enable the vehicle to be air dropped at Mach 0.7 and accelerated up to Mach 7 flight culminating in a demonstration of hydrocarbon scramjet operation. A series of component experiments was planned to reduce the level of risk and to advance the technology base. This paper summarizes the status of a full scale direct connect combustor experiment with heated endothermic hydrocarbon fuels. This is the first use of the NASA GRC Hypersonic Tunnel facility to support a direct-connect test. The technical and mechanical challenges involved with adapting this facility, previously used only in the free-jet configuration, for use in direct connect mode will be also described. Lee, Jin-Ho and Krivanek, Thomas M. Glenn Research Center NASA/TM-2005-213432, AIAA Paper 2005-0611, E-14966 WBS 22-794-50-20 ROCKET-BASED COMBINED-CYCLE ENGINES; SYSTEMS INTEGRATION; FULL SCALE TESTS; WIND TUNNEL TESTS; COMBUSTION CHAMBERS; HYDROCARBON FUELS; EXPERIMENT DESIGN; SUPERSONIC COMBUSTION RAMJET ENGINES; FLAME PROPAGATION; COMBUSTION PHYSICS; HYPERSONIC COMBUSTION; HYDROCARBON COMBUSTION; COMBUSTION STABILITY