Ten years ago yesterday, the NASA X-43A scramjet-powered flight research vehicle reached a record speed of over 6,600 mph (Mach 9.68). In doing so, the X-43A broke its own record speed of Mach 6.83 (4,600 mph) and became the fastest airbreathing aircraft of all time.
In 1996, NASA initiated a technology demonstration program known as HYPER-X. The central 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 close to 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 third and final flight of the HYPER-X program took place on Tuesday, 16 November 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 21:08 UTC. The aircraft then headed for the Pacific Ocean launch point located just west of San Nicholas Island.
At 22:34:43 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 75 seconds to reach a speed of slightly over Mach 10.
Following rocket motor burnout and a brief coast period, the HXRV (X-43A) successfully separated from the Pegasus booster at 109,440 feet and Mach 9.74. The HXRV scramjet was operative by Mach 9.68. Supersonic combustion and thrust production were successfully achieved. Total scramjet engine power-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 850 nautical miles due west of its launch location. Total flight time was approximately 15 minutes.
The HYPER-X Program was now history. Supersonic combustion and thrust production of an airframe-integrated scramjet had indeed been 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 several Guinness World Records for its efforts.
As a footnote to the X-43A story, the HYPER-X Flight 3 mission would also be the last for NASA’s fabled B-52B mothership. The aircraft that launched many of the historic X-15, M2-F2, M2-F3, X- 24A, X-24B and HL-10 flight research missions, and all three HYPER-X flights, would take to the air no more. In tribute, B-52B (S/N 52-0008) now occupies a place of honor at a point near the North Gate of Edwards Air Force Base.