The US Army has tested a hypersonic missile, which travels six times faster than the speed of sound. It is part of a larger plan to have the capability to strike any place on the planet within an hour. The missile, called the Advanced Hypersonic Weapon (AHW), was launched from Hawaii on Thursday, the Pentagon reported. A rocket delivered it to suborbital altitude, after which the glider went for its target on the Marshall Islands, some 3,700 kilometers away. It hit less than 30 minutes later, which means its speed was at least 7,400 kilometer per hour, or about Mach 6. An aircraft must be able to fly faster than Mach 5, to qualify as hypersonic. A Mach number is used to describe the speed of an object or a fluid in comparison to the speed of sound in that medium. Mach 1 means the object travels at the same speed as sound. However the speed of sound may vary depending on such conditions as temperature and composition, so the speed expressed in Mach number is also variable. The now-retired Concorde supersonic passenger planes used to fly at a cruising speed of about Mach 2. The test was aimed at gathering data on “aerodynamics, navigation, guidance and control, and thermal protection technologies,” the Pentagon said. The AHW is one of several projects of the Prompt Global Strike program. It is aimed at developing several weapons which can be launched from American territory and reach their destinations within an hour. On August 11 the US Air Force tested another hypersonic glider called the HTV-2. It is faster than the AHW, with speeds reaching 27,000 kilometer per hour. But unlike the Army’s vehicle, it does not work well – the test was aborted due to a technical failure. The Soviet Union developed ramjet engines capable of hypersonic locomotion and even tested one design, which successfully reached Mach 5.7. The work was stalled by the collapse of the USSR, and no weapon using this technology was ever produced.