Editing NASA X-43 (section)

==Operational testing==
[[Image:X-43A (Hyper - X) Mach 7 computational fluid dynamic (CFD).jpg|thumb|[[Computational fluid dynamics|CFD]] image of the X-43A at Mach 7]]
[[Image:B-52B with X43.jpg|thumb|right|The X-43A being dropped from under the wing of a [[Boeing B-52 Stratofortress|NB-52B Stratofortress]]]]

NASA's first X-43A test on June 2, 2001 failed because the Pegasus booster lost control about 13 seconds after it was released from the B-52 carrier. The rocket experienced a control oscillation as it went [[transonic]], eventually leading to the failure of the rocket's [[starboard]] [[elevon]]. This caused the rocket to deviate significantly from the planned course, and it was destroyed as a safety precaution. An investigation into the incident stated that imprecise information about the capabilities of the rocket as well as its flight environment contributed to the accident. Several inaccuracies in data modeling for this test led to an inadequate control system for the particular Pegasus rocket used, though no single factor could ultimately be blamed for the failure.<ref name=Bentley2008>Bentley, Matthew A. ''Spaceplanes: From Airport to Spaceport'' (Astronomers' Universe). New York: Springer, 2008. {{ISBN|978-0-38776-509-9}}, p. 110–111.</ref>

In the second test in March 2004, the Pegasus fired successfully and released the test vehicle at an altitude of about {{convert|29000|m|ft}}. After separation, the engine's air intake was opened, the engine ignited, and the aircraft then accelerated away from the rocket reaching {{cvt|6.83|Mach|altitude_ft=29000}}. Fuel was flowing to the engine for 11 seconds, a time in which the aircraft traveled more than {{cvt|24|km|mi}}. Following Pegasus booster separation, the vehicle experienced a small drop in speed but the scramjet engine afterward accelerated the vehicle in climbing flight.<ref name=Bentley2008/> After burnout, controllers were still able to maneuver the vehicle and manipulate the flight controls for several minutes; the aircraft, slowed by air resistance, fell into the ocean. With this flight the X-43A became the fastest free-flying [[Airbreathing jet engine|air-breathing]] aircraft in the world.

NASA flew a third version of the X-43A on November 16, 2004. The Pegasus rocket booster separated from its B-52 carrier at 40,000 feet and its solid rocket took the combination to Mach 10 at 110,000 feet.<ref name=Heppenheimer2007/> The X-43A split away at Mach 9.8 and the engine was started at Mach 9.65 for 10–12 seconds with thrust approximately equal to drag, and then glided to the Pacific Ocean after 14 minutes.<ref name=Heppenheimer2007/> Dynamic pressure during the flight was {{cvt|1,050|psf|bar}}.<ref name=Heppenheimer2007>{{cite web |author= Thomas A. Heppenheimer |url= http://www.dept.aoe.vt.edu/~mason/Mason_f/NASASP2007-4232Hypersonics.pdf |archive-url= https://web.archive.org/web/20110720112614if_/http://www.dept.aoe.vt.edu/~mason/Mason_f/NASASP2007-4232Hypersonics.pdf |url-status= dead |archive-date= 2011-07-20 |title= Facing the Heat Barrier: A History of Hypersonics |page= 277 |publisher= NASA History Division |date= September 2007}}</ref> It reached Mach 9.68,<ref name=PAW>{{cite web |url= http://www.pwrengineering.com/dataresources/AIAA-2005-3256-Paper-R-Kazmar-25071.pdf |archive-url= https://web.archive.org/web/20071021082342if_/http://www.pwrengineering.com/dataresources/AIAA-2005-3256-Paper-R-Kazmar-25071.pdf |url-status= dead |archive-date= 2007-10-21 |title= Airbreathing Hypersonic Propulsion at Pratt & Whitney – Overview |author= Richard R. Kazmar |publisher= American Institute of Aeronautics and Astronautics |year= 2005 }}</ref><ref name=X43>{{cite conference |url= http://www.aiaa.org/Participate/Uploads/AIAA_DL_McClinton.pdf |title= X-43: Scramjet Power Breaks the Hypersonic Barrier |author= Charles McClinton |publisher= NASA Langley Research Center |conference= 44th AIAA Aerospace Sciences Meeting and Exhibit |date= 9 Jan 2006|archive-url= https://web.archive.org/web/20110724231440/http://www.aiaa.org/Participate/Uploads/AIAA_DL_McClinton.pdf |archive-date= 2011-07-24 }}</ref> {{cvt|6,755|mph|sigfig=4}} at 109,440&nbsp;ft (33,357 m),<ref>{{cite web |url= https://www.guinnessworldrecords.com/world-records/fastest-aircraft-air-breathing-engine |title= Fastest aircraft, air-breathing engine: X-43 |date= 16 Nov 2004 |work= Guinness World Records}}</ref> and further tested the ability of the vehicle to withstand the heat loads involved.<ref name=NASA040>{{cite web |url= http://www.nasa.gov/centers/dryden/news/FactSheets/FS-040-DFRC.html |title= NASA "Hyper-X" Program Demonstrates Scramjet Technologies |publisher= NASA |date= Aug 7, 2017}}</ref>

===Replacements===
In January 2006 the USAF announced the [[DARPA Falcon Project|Force Application and Launch from Continental United States]] or FALCON scramjet reusable missile.<ref>[http://space.com/businesstechnology/060126_darpa_falcon.html "Falcon."] ''space.com.'' Retrieved: August 1, 2011.</ref>
In March 2006, it was announced that the Air Force Research Laboratory (AFRL) supersonic combustion ramjet "WaveRider" flight test vehicle had been designated as X-51A. The USAF [[Boeing X-51]] was first flown on May 26, 2010, dropped from a B-52.