Hypersonic rocket engines are really cool.

The article discusses the development of reusable rocket engines powerful enough to fly a suborbital space plane from London, England to Sydney, Australia in four hours. Topics include the development and testing of a hydrogen-and-air-burning engine, called Sabre, by Reaction Engines of Culham in Oxfordshire, England, Sabre's key technological features, such as a chiller that processes air to burn with hydrogen, and advances in pulse jet engine technology.