Supersonic Transport - Hypersonic Transport

Hypersonic Transport

While conventional turbo and ramjet engines are able to remain reasonably efficient up to Mach 5.5, some ideas for very high-speed flight above Mach 6 are also sometimes discussed, with the aim of reducing travel times down to one or two hours anywhere in the world.

These vehicle proposals very typically either use rocket or scramjet engines; pulse detonation engines have also been proposed.

There are many difficulties with such flight, both technical and economic.

Rocket-engined vehicles, while technically practical (either as ballistic transports or as semiballistic transports using wings), would use a very large amount of propellant and operate best at speeds between about Mach 8 and orbital speeds. Rockets compete best with air-breathing jet engines on cost at very long range; however, even for antipodal travel, costs would be only somewhat lower than orbital launch costs.

Scramjets currently are not practical for passenger-carrying vehicles.

Precooled jet engines are jet engines with a heat exchanger at the inlet that cools the air at very high speeds. these engines may be practical and efficient at up to about Mach 5.5, and this is an area of research in Europe and Japan.