The X-43A will then fire its specialized engine -- called a scramjet -- and fly under its own power for 10 seconds, covering about 17 miles (27 kilometers). It will then coast to an impact in the water.
The plane should reach speeds approaching mach 7 during its fleeting flight, besting the mach 6.7 record set by the rocket-powered X-15 in 1967.
Although a rocket will bump the X-43A to its initial velocity, it will rely on an air-breathing engine while flying independently. The plane will carry a small amount of hydrogen for fuel, but scoop oxygen out of the atmosphere to combust it. Conventional rockets must carry both fuel and an oxidant.
The flight will mark the first time an air-breathing plane flies at hypersonic speeds, or faster than mach 5.
The $185 million experimental project aims to fly three of the planes over the next 18 months. Although none of the planes will be recovered, data collected during the flights will be used to build future planes perhaps 200 feet (60 meters) in length. The first piloted prototypes may fly by 2025.
Backers of the technology say air-breathing hypersonic propulsion could help space travel by reducing the need to carry an oxidant aboard, freeing up room for extra cargo.
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