The world’s first hypersonic air-breathing free-flight vehicle is no longer just a paper airplane. The first of three experimental
vehicles, designated X-43A, recently arrived at NASA’s Dryden Flight Research Center, Edwards, Calif., to prepare for flight in
May 2000.
Flight of the X-43 vehicles will be the culmination of over 20 years of scramjet (supersonic combustible ramjet) research and the
first time a non-rocket engine has powered vehicles at hypersonic speeds.
Built by Micro Craft, Inc., Tullahoma, Tenn., for NASA’s Hyper-X program, the 12-foot-long, unpiloted X-43 vehicles will
significantly expand the boundaries of air-breathing aircraft. Three flights are planned — two at Mach 7 and one at Mach 10. The
flight tests will be conducted within the Western Test Range off the coast of southern California.
The Hyper-X program will build a technology bridge to reusable and recoverable vehicles with larger engines. Program managers
hope to demonstrate hydrogen-powered, air-breathing propulsion systems that could ultimately be applied in vehicles from
hypersonic aircraft to reusable space launchers.
Hypersonic speed is reached when velocity is above Mach 5 — equivalent to about one mile per second, or 3,600 miles per hour at
sea level. The highest speed reached by NASA’s rocket-powered X-15 was Mach 6.7. Currently, NASA’s SR-71 is the world’s
fastest air-breathing aircraft, soaring slightly above Mach 3, or three times the speed of sound.
Unlike a rocket that must carry its own oxygen for combustion, an air-breathing aircraft scoops air from the atmosphere, making
the aircraft lighter and enabling it to carry more cargo/payload than rocket-powered propulsion vehicles. The X-43 will use the
body of the aircraft itself to form critical elements of the engine with the forebody acting as the intake for the airflow and using the
aft section as the nozzle.
“This is high-risk technology. It’s exactly the type of flight research that NASA’s Office of Aero-Space Technology should be
doing,” said Joel Sitz, Dryden’s X-43A project manager. “NASA, working with industry, must answer the mail on developing a
feasible, efficient design.”
“We have the best-performing engine in the last 30 or 40 years here at Langley,” said Vincent Rausch, Hyper-X program manager.
“We are excited that we have a vehicle at Dryden, but there is a lot of hard work and testing yet to be done.”
Each Hyper-X vehicle will ride atop a booster rocket from Orbital Sciences Corp., Dulles, Va., and will be air-launched by
Dryden’s B-52 airplane. After being launched from the B-52, the X-43 will separate from the rocket at a predetermined altitude
and velocity, then fly a pre-programmed trajectory, conducting aerodynamic and propulsion experiments, before it impacts into the
Pacific Ocean.
NASA’s Langley Research Center, Hampton, VA, where the X-43’s engine — scramjet — is being wind-tunnel tested, manages the
Hyper-X program. Dryden is responsible for vehicle fabrication and flight tests.
