Another one for the "project cancelled" bin - the Mach 4 aircraft Burt Rutan's Scaled Composites was designing for Space Launch under DARPA's RASCAL (Responsive Access, Small Cargo, Affordable Launch) programme. The aircraft was called the MIPCC Powered Vehicle (MPV) because the four F100 engines were to be modified with "mass injection pre-compressor cooling", or MIPCC. This injected water and/or liquid oxygen into the inlet duct to cool the compressor and add massflow, fooling the engine into thinking it was flying at lower altitude in thicker air and maintaining its thrust to higher altitude and Mach number. This was intended to allow the MPV to zoom-climb out of the atmosphere, deploy a rocket-powered upper stage and satellite, and fire its reaction-control motors to turn round and re-enter.
MIPPC was tested on the ground, and worked, but RASCAL proved too "DARPA hard". Space Launch is still trying to get the concept off the ground using a modified F-4 (http://www.spacelaunch.com/products.asp)
MIPPC was tested on the ground, and worked, but RASCAL proved too "DARPA hard". Space Launch is still trying to get the concept off the ground using a modified F-4 (http://www.spacelaunch.com/products.asp)