Abstract : This report documents a collaborative research effort among Caltech, the CALSPAN Research Center at SUNY at Buffalo, the University of Minnesota, and Virginia Tech., spanning from June 2004 to May 2009, under AFOSR sponsorship, with program management by Dr. J. Tishkoff. The work focused on fundamental issues related to and derived from the design, performance, and operation of efficient ramjet/scramjet combined-cycle hypersonic propulsion. The work combined experiments in a variety of facilities; numerical simulations employing large-eddy simulations with subgrid-scale (LES-SGS) modeling, detached eddy simulations (DES), and, where appropriate, Reynolds-averaged Navier-Stokes (RANS) simulations; modeling; and diagnostics-/instrumentation-development efforts. Significant accomplishments include quantitative measurements of molecular mixing in scramjet-like flows ranging from high subsonic to supersonic Mach numbers, grid-converged validated LES-SGS of such flows, the development of highly efficient hybrid RANS-DES-LES simulations of non-reacting and reacting scramjet-combustor flows that correctly capture flow behavior; unique experimental data on scramjet combustors and propulsion-mode switching in fully simulated hypersonic flows; and the development of new diagnostics such as arrayed micro-probe, heat-flux, and skin-friction sensors.