| X-7 | |
|---|---|
 | |
| Role | Experimental aircraft |
| Manufacturer | Lockheed Corporation |
| First flight | April 26, 1951 |
| Retired | 1960 |
| Primary user | United States Air Force |
| Developed into | AQM-60 Kingfisher |
The Lockheed X-7 (dubbed the "Flying Stove Pipe") was 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.
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 Mach 3 (3,200 km/h; 2,000 mph). [1]
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. [1] Despite its first launch being a failure, after re-development of the original ramjet, following test flights were successful. [2] A total of 130 X-7 flights were conducted from April 1951 to July 1960. [2]
The X-7 laid the foundation for the AQM-60 Kingfisher. [1] Being the testbed for several yearlong projects, the X-7 underwent many structural changes to adapt more closely for its intended purpose. [1] 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, SAM-A-25/MIM-14 Nike Hercules, and IM-99/CIM-10 Bomarc were the missiles used in the tests. [3] During the testing of the SAMs, the X-7 outperformed the missiles and a very small number of critical hits were achieved. [2] Due to pressure and embarrassment of the military, the X-7 project was terminated in the mid-1960s. [2]
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. [2]
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. [4]
The X-7 was launched at speed release from the underside of either a B-29 or B-50 carrier plane. [5] The jet would then take over and build up speed to its top speed of 1,600 km/h (1,000 mph), but was later redesigned to push Mach 4.3 (4,680 km/h; 2,910 mph). [1]
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. [2] 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. [1] 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. [1]
Related development
Aircraft of comparable role, configuration, and era
The Boeing CIM-10 Bomarc was a supersonic ramjet powered long-range surface-to-air missile (SAM) used during the Cold War for the air defense of North America. In addition to being the first operational long-range SAM and the first operational pulse doppler aviation radar, it was the only SAM deployed by the United States Air Force.
A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around Mach 3 and can operate up to Mach 6.
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion, but whereas a ramjet decelerates the air to subsonic velocities before combustion using shock cones, a scramjet has no shock cone and slows the airflow using shockwaves produced by its ignition source in place of a shock cone. This allows the scramjet to operate efficiently at extremely high speeds.
The NASA X-43 was an experimental unmanned hypersonic aircraft with multiple planned scale variations meant to test various aspects of hypersonic flight. It was part of the X-plane series and specifically of NASA's Hyper-X program developed in the late 1990s. It set several airspeed records for jet aircraft. The X-43 is the fastest jet-powered aircraft on record at approximately Mach 9.6.
The Lockheed D-21 is an American supersonic reconnaissance drone. The D-21 was initially designed to be launched from the back of an M-21 carrier aircraft, a variant of the Lockheed A-12 aircraft. The drone had maximum speed in excess of Mach 3.3 at an operational altitude of 90,000 feet. Development began in October 1962. Originally known by the Lockheed designation Q-12, the drone was intended for reconnaissance deep into enemy airspace.
The North American SM-64 Navaho was a supersonic intercontinental cruise missile project built by North American Aviation (NAA). The final design was capable of delivering a nuclear weapon to the USSR from bases within the US, while cruising at Mach 3 at 60,000 feet (18,000 m) altitude. The missile is named after the Navajo Nation.
The AQM-35 was a supersonic target drone produced by the Northrop Corporation.
The DARPA FALCON Project is a two-part joint project between the Defense Advanced Research Projects Agency (DARPA) and the United States Air Force (USAF) and is part of Prompt Global Strike. The first part of the project aims to develop a Small Launch System (SLS) capable of accelerating hypersonic gliding weapons as well as launching small satellites into Earth orbit. The second part of the project aims to develop Hypersonic Weapon Systems (HWS): a short term high performance hypersonic gliding weapon previously named the X-41 Common Aero Vehicle (CAV) that could be launched from Expendable Launch Vehicles (ELV), Reusable Launch Vehicles (RLVs), Hypersonic Cruise Vehicles (HCV), or Space Maneuvering Vehicles (SMP), and a long term hypersonic cruise aircraft named the Hypersonic Cruise Vehicle (HCV). This two-part program was announced in 2003 and continued into 2006.
The Boeing X-51 Waverider is an unmanned research scramjet experimental aircraft for hypersonic flight at Mach 5 and an altitude of 70,000 feet (21,000 m). The aircraft was designated X-51 in 2005. It completed its first powered hypersonic flight on 26 May 2010. After two unsuccessful test flights, the X-51 completed a flight of over six minutes and reached speeds of over Mach 5 for 210 seconds on 1 May 2013 for the longest duration powered hypersonic flight.
Scramjet programs refers to research and testing programs for the development of supersonic combustion ramjets, known as scramjets. This list provides a short overview of national and international collaborations, and civilian and military programs. The USA, Russia, India, and China (2014), have succeeded at developing scramjet technologies.
The AQM-60 Kingfisher, originally designated XQ-5, was a target drone version of the USAF's X-7 ramjet test aircraft built by the Lockheed Corporation. The aircraft was designed by Kelly Johnson, who later created the Lockheed A-12 and its relatives, such as the Lockheed SR-71 Blackbird and Lockheed YF-12.
Hypersonic flight is flight through the atmosphere below altitudes of about 90 km at speeds greater than Mach 5, a speed where dissociation of air begins to become significant and high heat loads exist. Speeds over Mach 25 have been achieved below the thermosphere as of 2020.
The Marquardt RJ43-MA was a ramjet engine used on the CIM-10 Bomarc missile, the D-21 drone, and the AQM-60 drone. They were engineered and built by the Marquardt Corporation.
The MA-31 was a conversion of the Kh-31, an anti-ship missile developed by the Soviet Union during the 1980s, for use as a target drone by the United States Navy. Although the missile proved successful in this role, political complications resulted in the type being only an interim solution, and only a small number of the missiles were acquired.
The MQM-42 was a supersonic target drone developed by North American Aviation. Developed in two subvariants, Redhead and Roadrunner, it was used by the United States Army in the 1960s and 1970s.
The AQM-127 Supersonic Low-Altitude Target (SLAT) was a target drone developed during the 1980s by Martin Marietta for use by the United States Navy. Derived from Martin Marietta's work on the cancelled ASALM missile, SLAT proved to have severe difficulties in flight testing, and the project was cancelled during 1991.
Hypersonic Technology Vehicle 2 (HTV-2) is an experimental hypersonic glide vehicle developed as part of the DARPA Falcon Project designed to fly in the Mach 20 range. It is a test bed for technologies to provide the United States with the capability to reach any target in the world within one hour using an unmanned hypersonic bomber aircraft.
The Ground-to-Air Pilotless Aircraft (GAPA) was a short-range surface-to-air missile (SAM) developed in the late 1940s by Boeing for the United States Army Air Forces, and then the United States Air Force after 1948. It was given the reference number SAM-A-1, the first Surface-to-Air Missile (SAM) in the 1947 tri-service designation system. By 1950, over 100 test rockets had been launched using a variety of configurations and power plants, with one launch in 1949 setting the altitude record for a ramjet powered vehicle at 59,000 ft (18,000 m).
The Lockheed Martin SR-72, colloquially referred to as "Son of Blackbird", is an American hypersonic UAV concept intended for intelligence, surveillance and reconnaissance (ISR) proposed privately in 2013 by Lockheed Martin as a successor to the retired Lockheed SR-71 Blackbird. In 2018, company executives said an SR-72 test vehicle could fly by 2025 and enter service in the 2030s.
