Scramjet Future
The reason scramjets are piquing the interest of scientists world-wide is that while very difficult to implement, they offer a couple distinct advantages over the current means of propulsion.
At this point I see the use of scramjets in missiles and satellite rockets is much more realistic than in aircraft. A missile can be fairly easily accelerated by a gun system, but it would be highly difficult to accelerate an aircraft to hypersonic speeds so that the scramjet can take over. Even if a way could be found to accelerate an aircraft, the design shape necessary to handle hypersonic speeds is not suited for subsonic speeds necessary for landings. The craft could be slowed by a system of parachutes, but seems highly uneconomical and impractical for a craft subject to regular use. The other alternative is the development of a hybrid engine that could be switched between subsonic jet operation, to ramjet, and finally scramjet configurations. In the future this may become a viable possibility, but first it will require years of research and testing of scramjet behavior.
- They operate at higher speeds and altitudes than conventional jet engines. It is believed that they should be able to function over the range of Mach 5 to 20. By contrast, the fastest ramjet plane, the SR-71 Blackbird operated about Mach 3.5.
- Rockets can easily achieve these speeds, but they are much more expensive to operate. Rockets achieve their great thrust by carrying the fuel as well as the oxygen needed to burn the fuel. A considerable amount of the weight of the rocket is taken up by the oxygen (or oxygen-rich compounds in solid fuel rockets) they carry on board, so that much of the fuel is needed solely to transport this additional weight. Scramjets can operate much more efficiently by comparison, since they derive all the oxygen for combustion out of the atmosphere. This reduces the cost of operational costs as well as the size and weight of the craft.
