Flight tests of a powerful US military scramjet prototype able to exceed Mach 4 while burning ordinary jet fuel have been scheduled for December, according to reports. Aviation Week reports today that the X-51 "WaveRider" scramjet will now fly in December. The X-51 will be released from a B-52 bomber mothership operated by NASA above southern California. A modified missile booster rocket will accelerate the test stack past Mach 4, after which the 25-foot-long X-51 will ignite using ethylene lighter fluid, easier to get burning in a very fast airstream. The purpose of scramjets is to beat the speed limitations of ordinary ramjets, which slow their internal air intake stream down to subsonic speeds. Unfortunately this produces unacceptable levels of drag and fuel consumption above Mach 3 to 4, hence the desire for a supersonic-combustion ramjet - a scramjet.