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Seven years ago this week, the NASA X-43A scramjet-powered flight research vehicle reached a record speed of over 4,600 mph (Mach 6.83).  The test marked the first time in the annals of aviation that a flight-scale scramjet accelerated an aircraft in the hypersonic Mach number regime.  

NASA initiated a technology demonstration program known as HYPER-X in 1996.  The fundamental goal of the HYPER-X Program was to successfully demonstrate sustained supersonic combustion and thrust production of a flight-scale scramjet propulsion system at speeds up to Mach 10.

Also known as the HYPER-X Research Vehicle (HXRV), the X-43A aircraft was a scramjet test bed.  The aircraft measured 12 feet in length, 5 feet in width, and weighed nearly 3,000 pounds.  The X-43A was boosted to scramjet take-over speeds with a modified Orbital Sciences Pegasus rocket booster.

The combined HXRV-Pegasus stack was referred to as the HYPER-X Launch Vehicle (HXLV).  Measuring approximately 50 feet in length, the HXLV weighed slightly more than 41,000 pounds.  The HXLV was air-launched from a B-52 mothership.  Together, the entire assemblage constituted a 3-stage vehicle.

The second flight of the HYPER-X program took place on Saturday, 27 March 2004.  The flight originated from Edwards Air Force Base, California.  Using Runway 04, NASA’s venerable B-52B (S/N 52-0008) started its take-off roll at approximately 20:40 UTC.  The aircraft then headed for the Pacific Ocean launch point located just west of San Nicholas Island.

At 21:59:58 UTC, the HXLV fell away from the B-52B mothership.  Following a 5 second free fall, rocket motor ignition occurred and the HXLV initiated a pull-up to start its climb and acceleration to the test window.  It took the HXLV about 90 seconds to reach a speed of slightly over Mach 7.

Following rocket motor burnout and a brief coast period, the HXRV (X-43A) successfully separated from the Pegasus booster at 94,069feet and Mach 6.95.  The HXRV scramjet was operative by Mach 6.83.  Supersonic combustion and thrust production were successfully achieved.  Total engine-on duration was approximately 11 seconds.

As the X-43A decelerated along its post-burn descent flight path, the aircraft performed a series of data gathering flight maneuvers.  A vast quantity of high-quality aerodynamic and flight control system data were acquired for Mach numbers ranging from hypersonic to transonic.  Finally, the X-43A impacted the Pacific Ocean at a point about 450 nautical miles due west of its launch location.  Total flight time was approximately 15 minutes.

The HYPER-X Program made history that day in late March 2004.  Supersonic combustion and thrust production of an airframe-integrated scramjet were achieved for the first time in flight; a goal that dated back to before the X-15 Program.   Along the way, the X-43A established a speed record for airbreathing aircraft and earned a Guinness World Record for its efforts.

Posted in Aerospace, History

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