But once there, a scramjet-powered aircraft should be able to zoom away to speeds unattainable by a turbojet.

ECONOMIST: Jet propulsion

After separating from the booster, the scramjet engine was ignited, accelerating the aircraft to Mach 5.1 at 60, 000 feet.

NPR: Experimental Air Force Aircraft Goes Hypersonic

Only then will the booster be jettisoned and the scramjet ignited.

ECONOMIST: Hypersonic aviation

The sleek, missile-shaped WaveRider was released from a B-52 bomber 50, 000 feet above the Pacific and was initially accelerated by a rocket before the scramjet kicked in.

NPR: Experimental Air Force Aircraft Goes Hypersonic

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

The X-51A WaveRider flew for more than three minutes under power from its exotic scramjet engine and hit a speed of Mach 5.1, or more than five times the speed of sound.

NPR: Experimental Air Force Aircraft Goes Hypersonic