View source for Lockheed X-7

{{Short description|Experimental aircraft to test ramjet engines and missile guidance technology}}
{{Infobox aircraft
  |name =X-7
  |image =X-7 USAF.jpg
  |caption =
  |type = [[Experimental aircraft]]
  |manufacturer = [[Lockheed Corporation]]
  |designer = 
  |first_flight = April 26, 1951
  |introduction =
  |retired = 1960
  |status = 
  |primary_user = [[United States Air Force]]
  |more_users =
  |produced =
  |number_built = 
  |unit cost =
  |program cost = 
  |developed_from=
  |variants =
  |developed_into= [[AQM-60 Kingfisher]]
}}
[[File:Lockheed X-7.jpg|alt=The black and yellow missile sits on display overlooking desert and mountains of New Mexico|thumb|A Lockheed X-7 on public display in New Mexico]]
The '''Lockheed X-7''' (dubbed the "Flying Stove Pipe") is an American unmanned test bed of the 1950s for [[ramjet]] engines and [[missile guidance]] technology. It was the basis for the later Lockheed [[AQM-60 Kingfisher]], a system used to test American air defenses against nuclear missile attack.

==Early development==
Development of the Kingfisher was first initiated in December 1946. The X-7 was called into production by the United States Air Force requirement for the development of an unmanned ramjet test plane with a top speed of at least {{convert|3|Mach|altitude_ft=40000}}.<ref name=":13">{{Cite web|url=http://www.designation-systems.net/dusrm/m-60.html|title=Lockheed AQM-60 Kingfisher|website=www.designation-systems.net|access-date=2017-04-09}}</ref>

The X-7 project was developed under the AMC designator MX-883 and was given in the Lockheed in-house designation L-171. The L-171 was initially designated the '''PTV-A-1''' by the USAF but was later designated the X-7 in 1951.<ref name=":13" />  Despite its first launch being a failure, after re-development of the original ramjet, following test flights were successful.<ref name=":06">{{Cite web|url=http://www.456fis.org/LOCKHEED_X-7.htm|title=The Lockheed X-7|website=www.456fis.org|access-date=2017-04-09|archive-date=2018-05-19|archive-url=https://web.archive.org/web/20180519003015/http://www.456fis.org/LOCKHEED_X-7.htm|url-status=usurped}}</ref> A total of 130 X-7 flights were conducted from April 1951 to July 1960.<ref name=":06"/>

==Purpose==
The X-7 laid the foundation for the AQM-60 Kingfisher.<ref name=":13" />  Being the testbed for several yearlong projects, the X-7 underwent many structural changes to adapt more closely for its intended purpose.<ref name=":13" />  The Kingfisher was put up against three surface to air missiles designed to test the capabilities of the X-7; SAM-A-7/[[MIM-3 Nike Ajax|MIM-3 ''Nike Ajax'']], SAM-A-25/[[Nike Hercules|MIM-14 ''Nike Hercules'']], and [[CIM-10 Bomarc|IM-99/CIM-10 ''Bomarc'']] were the missiles used in the tests.<ref>Facing the Heat Barrier: A History of Hypersonics, T. A. Heppenheimer, P.65</ref>  During the testing of the SAMs, the X-7 outperformed the missiles and a very small number of critical hits were achieved.<ref name=":06" />  Due to pressure and embarrassment of the military, the X-7 project was terminated in the mid-1960s.<ref name=":06" />

Besides the surface to air missile tests, the X-7 project was also used to test communication equipment for acceleration tests, testing aerodynamics, booster propellants, thermodynamics, and parachutes.<ref name=":06" />
[[File:X-7_Prepared_for_Loading.jpg|thumb|Lockheed X-7A-1 being prepared for loading and test flight. The white section is the booster. (B-50 seen in background)]]

==Construction==
The X-7 was constructed from steel, unlike its successors such as the A-12 and YF-12 which used titanium. These X-7 planes had wings constructed from stainless steel and a fuselage made from a nickel alloy. The use of steel was due to the inability of aluminum to endure air friction heating at hypersonic speeds, years before the widespread introduction of titanium.

The engines developed for the X-7/AQM-60 were designed to operate for a short time, to test the design for the [[CIM-10 Bomarc]]. They were redesigned with better materials for use on the hypersonic [[Lockheed D-21]] drone launched from the back of a [[Lockheed M-21]], a derivative of the [[Lockheed A-12]], or from under the wing of a [[Boeing B-52 Stratofortress]].<ref>Goodall and Goodall 2002, p. 106.</ref>

==Launch and recovery==
[[File:X-7a-3_Recovery.jpg|thumb|Lockheed X-7 buried nose down in the desert]]
The X-7 was launched at speed release from the underside of either a B-29 or B-50 carrier plane.<ref>{{Cite web|url=http://www.boeing.com/history/products/b-29-superfortress.page|title=Boeing: Historical Snapshot: B-29 Superfortress|website=www.boeing.com|access-date=2017-04-10}}</ref> The jet would then take over and build up speed to its top speed of {{convert|1000|mph|disp=flip|abbr=on}}, but was later redesigned to push {{convert|4.3|Mach|altitude_ft=100000}}.<ref name=":13" />

The recovery method of the X-7 rocket plane was a new and simple design for a test plane of its kind but functioned as designed. A multi-stage parachute was deployed after the jet had exhausted its fuel, slowing its descent.<ref name=":06" />  Once it had reached the ground, the long metal rod on the end of the nose penetrated the ground, keeping the plane upright and preventing damage to the structure of the X-7. 

In 1954, the modified X-7 underwent significant changes and was renamed the X-7A-3.<ref name=":13" />  The wing shape was altered, and two small boosters were added to the plane, one under each wing. Due to these alterations, the drop method previously used was changed. The previous version was a complicated, bulky under-wing system, while the new design allowed for a simple fuselage-mounted dropping system. This system was used until its final flight in July 1960.<ref name=":13" />

== Surviving aircraft ==
* X-7 on display at the [[Aviation Unmanned Vehicle Museum]] in [[Caddo Mills, Texas]].<ref>{{cite web |title=BGM-34B ATTACK & MULTI-MISSION RPV |url=http://auvm.net/drone-exhibits |website=AUVM |access-date=12 October 2020 |archive-date=27 October 2020 |archive-url=https://web.archive.org/web/20201027171616/https://auvm.net/drone-exhibits |url-status=dead }}</ref>
[[File:X-7a Lockheed.jpg|thumb|X-7A on display at the Aviation Unmanned Vehicle Museum]]

==Specifications of X-7A-1==
* Length: {{convert|32|ft|9|in|disp=flip|abbr=on}}
* Wingspan: {{convert|12|ft|disp=flip|abbr=on}}
* Height: {{convert|7|ft|disp=flip|abbr=on}}
* Diameter: {{convert|20|in|disp=flip|abbr=on}}
* Weight: {{convert|8000|lb|disp=flip|abbr=on}}
* Speed: {{convert|2800|mph|disp=flip|abbr=on}} (Maximum speed: {{convert|4.31|Mach|altitude_ft=106000}}<ref name=":06" />)
* Ceiling: {{convert|106000|ft|disp=flip|abbr=on}}
* Range: {{convert|130|mi|disp=flip|abbr=on}}
* Booster: Alleghany Ballistics Lab. X202-C3 solid- fuel rocket; 467&nbsp;kN for 4 seconds.
* Sustainer: Ramjet

== Specifications of X-7A-3==
* Length: {{convert|37|feet|disp=flip|abbr=on}}
* Wingspan: {{convert|10|feet|disp=flip|abbr=on}}
* Height: {{convert|7|feet|disp=flip|abbr=on}}
* Diameter: {{convert|20|in|disp=flip|abbr=on}}
* Weight: {{convert|8000|lb|disp=flip|abbr=on}}
* Speed: {{convert|2800|mph|disp=flip|abbr=on}}
* Ceiling: {{convert|106000|ft|disp=flip|abbr=on}}
* Range: {{convert|130|mi|disp=flip|abbr=on}}
* Booster: X-7A-3/XQ-5: 2x Thiokol XM45 (5KS50000) solid-fuel rocket; 222&nbsp;kN (50000&nbsp;lb)
* Sustainer: Ramjet

==See also==
{{aircontent|
|related=
* [[Lockheed AQM-60 Kingfisher|Q-5 Kingfisher]] (based on the X-7 A-3)
|similar aircraft=
* [[CIM-10 Bomarc|Bomarc]]
|lists=
|see also=
}}

==References==
{{Reflist|refs="Boeing: Historical Snapshot: B-29 Superfortress". www.boeing.com. Retrieved 2017-04-10.

"Lockheed AQM-60 Kingfisher". www.designation-systems.net. Retrieved 2017-04-09.

"Lockheed X-7A-1(Marquardt MA20)". planes.axlegeeks.com. Retrieved 2017-04-10.
Journals, World Journals, Database of Academic Research. 
}}

==External links==
{{Commons category}}
* [http://www.designation-systems.net/dusrm/m-60.html Q-5/AQM-60]
* [https://books.google.com/books?id=Ci0DAAAAMBAJ&dq=popular+science+1930&pg=PA142 "Ramjet test missile takes off on supersonic flight."] ''Popular Science'', pp.&nbsp;142–143.
* [https://auvm.net/drone-history Lockheed X7-A] {{Webarchive|url=https://web.archive.org/web/20190929145701/https://auvm.net/drone-history |date=2019-09-29 }} – X7-A on display at [https://www.auvm.net/ Aviation Unmanned Vehicle Museum] outside Dallas, Texas, United States.

{{Lockheed aircraft}}
{{X-planes}}
{{USAF early missiles}}
{{USAF system codes}}
{{Authority control}}

[[Category:Lockheed aircraft|X-007]]
[[Category:1950s United States experimental aircraft|X-07, Lockheed]]
[[Category:Unmanned military aircraft of the United States]]
[[Category:Single-engined jet aircraft]]
[[Category:Mid-wing aircraft]]
[[Category:Ramjet-powered aircraft]]
[[Category:Aircraft with auxiliary rocket engines]]
[[Category:Aircraft first flown in 1951]]