X-43A, which is pilotless, four metres long, and has a nose made of solid tungsten, will be the first working aircraft to be powered by a scramjet a supersonic-combustion ramjet.
ECONOMIST: Jet propulsion
2.
Unlike the more familiar turbojet, which uses a turbine-powered fan to compress the incoming air before it is mixed with fuel, a ramjet compresses air by forcing it down an ever-narrowing funnel.