The trade publication High-Performance Composites offers this news about the development of SpaceShipTwo:
Advanced Composites Group Ltd. (ACG, Heanor, Derbyshire, U.K.) will supply a new generation of out-of-autoclave prepregs for the project, featuring MTM45-1, a variable-cure temperature, high-performance, toughened epoxy matrix developed for resin film infusion and prepreg processing. It was designed for low-pressure vacuum bag processing and, in addition to resin film and prepreg formats, is available in partially or selectively impregnated formats to reduce layup time, surface defects and internal voids. After a freestanding postcure, the system is capable of 150°C (302°F) wet Tg and reportedly exhibits good damage tolerance. Initial cure can be as low as 80°C/176°F, which ACG says allows for the use of lower cost tooling materials.
But you all knew that already.