Editing Zero-length launch

{{Short description|Method of launching military aircraft}}
{{Redirect|ZELL||Zell (disambiguation){{!}}Zell}}
[[File:F-100 zero-length-launch trial.jpg|thumb|upright=1.14|A USAF F-100D Super Sabre using a zero-length-launch system]]

The '''zero-length launch system''' or '''zero-length take-off system''' (ZLL, ZLTO, ZEL, ZELL) is a [[PTOL]] method whereby [[jet aircraft|jet]] [[fighter aircraft|fighters]] and [[attack aircraft]] could be near-vertically launched using [[rocket motor]]s to rapidly gain speed and altitude, in particular for [[point-defence]] roles. Such rocket boosters were limited to a short burn duration, were typically solid-fuel and suitable for only a single use. They were intended to drop away once expended.

The majority of ZELL experiments, which including the conversion of several front-line combat aircraft for trialing the system, occurred during the 1950s amid the formative years of the [[Cold War]]. As envisioned, the operational use of ZELL would have employed mobile launch platforms to disperse and hide aircraft, reducing their vulnerability in comparison to being centralised around established airbases with well-known locations. While flight testing had proved such systems to be feasible for combat aircraft, no ZELL-configured aircraft were ever used operationally. The emergence of ever-capable [[missile]]s had greatly reduced the strategic necessity of aircraft for the [[nuclear strike]] mission, while questions over practicality had also played a role.

==History==
During the second world war, Germany experimented with the [[Bachem Ba 349]], but development was cut short by the end of the war.

According to aviation author Tony Moore, the concept of the ''zero-length launch system'' became popular amongst military planners and strategists during the early years of the [[Cold War]].<ref name = "moore 72"/> Conventional aircraft, reliant on large and well-established airbases, were thought to be too easily destroyed in the opening hours of a major conflict between the [[superpower]]s, thus the ability to remove this dependence upon lengthy runways and airbases was highly attractive.<ref name = "moore 72"/> During the 1950s, various countries began experimenting with a diverse range of methods to launch armed fighter jets, typically using some arrangement of [[rocket motor]]s. In some concepts, such a fighter could be launched from a trailer from virtually any location, including those that could be [[camouflage]]d or otherwise concealed up until the moment of launch.<ref name = "moore 72">Moore 2008, p. 72.</ref>

The primary advantage of a zero-length launch system is the elimination of the historic dependence on vulnerable [[airfield]]s for air operations.<ref name = "Khurana 147"/> In the event of a sudden attack, air forces equipped with such systems could field effective air defenses and launch their own airstrikes even with their own airbases having been destroyed by an early [[nuclear attack]].<ref name = "moore 72"/> Although launching aircraft using rocket boosters proved to be relatively trouble-free, a runway was still required for these aircraft to be able to land or else be forced to ditch.<ref name = "Khurana 147"/> The mobile launching platforms also proved to be expensive to operate and somewhat bulky, typically making them difficult to transport. The security of the mobile launchers themselves would have been a major responsibility in and of itself, especially in the case of such launchers being equipped with [[nuclear weapons|nuclear]]-armed strike fighters.<ref name = "Khurana 147"/>

[[File:F-84 Thunderjet ZELL.jpg|thumb|left|F-84 during ZELL testing]]
The [[United States Air Force]], the ''Bundeswehr's'' [[German Air Force|Luftwaffe]], and the Soviet [[Soviet Air Force|VVS]] all conducted experiments in zero-length launching. The first manned aircraft to be ZELL-launched was an [[F-84G]] in 1955.<ref>[https://books.google.com/books?id=fNwDAAAAMBAJ&dq=1954+Popular+Mechanics+January&pg=PA108 "Fighter Plane Launched Like Missile From Truck Platform."] ''Popular Mechanics'', March 1955, p. 108.</ref> The Soviets' main interest in ZELL was for point defense-format protection of airfields and critical targets using [[MiG-19]]s. The American tests with the F-84s started with using the [[Martin MGM-1 Matador]] solid-fuel boost motor of some {{convert|240|kN|lb(f)|adj=on}} thrust output, which burned out seconds after ignition and dropped away from the manned fighter a second or two later.<ref name = "holder 138">Holder 2007, p. 138.</ref><ref>Norman and Norris 2009, p. 32.</ref> Tests of the larger F-100 Super Sabre and SM-30 (MiG-19) (with the SM-30 using the Soviet-design PRD-22R booster unit) used similar short-burn solid fueled boost motors, albeit of a much more powerful {{convert|600|kN|lb(f)|adj=on}} thrust-class output levels.<ref>[https://web.archive.org/web/20140319163404/http://www.airvectors.net/avzel.html Greg Goebel's Air Vectors' "The Zero-Length Launch Fighter" page]</ref><ref name = "Khurana 126">Khurana 2009, p. 126.</ref>

Testing proved that the F-100 was capable of a ZELL launch even while carrying both an external fuel tank and a single [[nuclear weapon]] mounted on its [[hard point]]s.<ref name = "moore 72"/> The conceived mission profile would have been for the pilot to have launched a retaliatory nuclear strike against the attacker before attempting to return to any available friendly airbase, or having to eject from the aircraft if a safe landing site could not be reached.<ref name = "moore 72"/> Despite the extremely high thrust generated by the rocket motor, the F-100 reportedly subjected its pilot to a maximum of 4&nbsp;g of acceleration forces during the takeoff phase of flight, reaching a speed of roughly {{cvt|300|mph|kph|order=flip|sigfig=1}} prior to the rocket motor's depletion.<ref name = "moore 723">Moore 2008, pp. 72-73.</ref> Once all fuel had been exhausted, the rocket motor was intended to slip backwards from its attachment points and drop away from the aircraft. However, testing revealed that this would sometimes fail to detach or cause minor damage to the aircraft's underside when doing so.<ref name = "moore 734">Moore 2008, pp. 73-74.</ref> Despite such difficulties, the F-100's ZELL system was considered to be feasible, but the idea of its deployment had become less attractive as time went on.<ref name = "moore 745">Moore 2008, pp. 74-75.</ref>

Eventually, all projects involving ZELL aircraft were abandoned, largely due to logistical concerns, as well as the increasing efficiency of [[guided missile]]s having rendered the adoption of such aircraft to be less critical in the eyes of strategic planners.<ref name = "Khurana 147"/> Furthermore, the desire to field combat aircraft that lacked any dependence upon relatively vulnerable landing strips had motivated the development of several aircraft capable of either vertical takeoff and landing ([[VTOL]]) or short takeoff and landing ([[STOL]]) flight profiles; such fighters included production aircraft such as  British [[Hawker Siddeley Harrier]] and the Soviet [[Yak-38]], as well as experimental prototypes such as the American [[McDonnell Douglas F-15 STOL/MTD]].<ref name = "Khurana 147">Khurana 2009, p. 147.</ref>

== ZELMAL (zero-length launch mat landing)==

The ZELMAL program investigated the possibility of a zero-length landing. The program was conducted 1953 and 1954. It involved a Republic {{nowrap|F-84}} aircraft and an inflatable rubber mat. The aircraft would perform a zero-length landing by catching an arrester cable with a tailhook, similar to an aircraft carrier landing. The aircraft would then drop onto the rubber mat. A number of unmanned tests were performed before two piloted ZELMAL tests in 1954. In both cases the pilots suffered spinal injuries. The program was not continued after that.<ref>{{Cite book |last=Markman |first=Steve |url=https://www.worldcat.org/oclc/46790785 |title=Straight up : a history of vertical flight |date=2000 |publisher=Schiffer Pub |others=William G. Holder |isbn=0-7643-1204-9 |location=Atglen, PA |pages=147–149 |oclc=46790785 |quote=By the early 1950s, short ramps were used routinely to launch early cruise missiles. Engineers figured that perhaps this concept would work just as well for manned aircraft. But eliminating the runway for launch only solved half of the problem... one still would be needed for landing. But perhaps not. Thus was born the ZELMAL (ZEro-length Launch and MAt Landing) program. A rocket would be used to launch a fighter aircraft, then use an inflatable rubber mat, an arresting cable, and a tailhook for the landing. The mat they came up with measured 80 x 400 feet, was 30 inches thick, and had a slick surface coated with a lubricant to assure a smooth landing. [...] The first mat landing was performed on June 2, 1954, but was unsuccessful. The aircraft, S/N 51-1225, was piloted by a Martin Aircraft test pilot. The tailhook missed the arresting cables and tore through the mat surface, tearing open three air cells. Apparently the test pilot was not aware that the F-84 had a tail-hook/airplane flap interconnect system that automatically retracted the flaps when the tail hook contacted the arresting cable, or that he had a manual override switch. The momentary contact between the tail hook and the mat was enough to cause the flaps to retract and the aircraft to settle on the mat too quickly. Complicating the problem was the slow engine response to the pilot's full throttle command. The F-84 bounced off the mat, skidded across the lakebed, and was damaged beyond economical repair. The pilot received back injuries that grounded him for several months.}}</ref>

==Manned aircraft involved in ZELL testing==
[[File:Lockheed F-104G DA 102 ZELL tests Edwards AFB 1963 (mfr LA 3183 via RJF) (16929987577).jpg|thumb|A Lockheed F-104G during tests at Edwards Air Force Base]]

* [[Republic F-84G Thunderjet]]
* [[North American F-100D Super Sabre]]
* [[Lockheed F-104 Starfighter]]
* [[Mikoyan-Gurevich MiG-19]] SM-30
* [[Avro Canada CF-105 Arrow]]<ref>{{Cite web|url=http://central.bac-lac.gc.ca/.redirect?app=fonandcol&id=4824318&lang=eng|title=Collection search - Rocket Geometry Zero Length Launch CF-105 Arrow [architectural: technical drawing]}}</ref>

==See also==
* [[Index of aviation articles]]
* [[Bachem Ba 349]]—World War II vertical launch rocket interceptor
* [[JATO]]
* [[CAM ship]]
* [[VTOL]]
* [[Aircraft catapult]], a device used to launch aircraft from [[aircraft carrier|aircraft carriers]]

==References==
===Citations===
{{Reflist}}

===Bibliography===
{{refbegin}}
* Holder, William G. ''Lost fighters: a history of U.S. jet fighter programs that didn't make it''. SAE, 2007. {{ISBN|0-7680-1712-2}}.
* Khurana, K.C. ''Aviation Management: Global Perspectives''. Global India Publications, 2009. {{ISBN|9-3802-2839-2}}.
* Moore, Tony. ''X-Plane Crashes: Exploring Experimental, Rocket Plane, and Spycraft Incidents, Accidents and Crash Sites''. Specialty Press, 2008. {{ISBN|1-5800-7222-4}}.
* Polmar, Norman and Robert Stan Norris. ''The U.S. Nuclear Arsenal: A History of Weapons and Delivery Systems Since 1945''. Naval Institute Press, 2009. {{ISBN|1-5575-0681-7}}.
{{refend}}

==External links==
{{Commons category|Zero length launch}}
* {{cite web |title=The Zero-Length Launch Fighter |url=http://www.vectorsite.net/avzel.html |publisher=Greg Goebel's AIR VECTORS |url-status=usurped |archive-url=https://web.archive.org/web/20120422093446/http://www.vectorsite.net:80/avzel.html|archive-date=22 April 2012 }}
* {{cite web |title=Martin Matador and Mace missiles |url=http://www.mace-b.com/38TMW/Missiles/History.htm |publisher=38th Tactical Missile Wing, tribute site}}
* {{cite web |title=Cape Canaveral Air Force Station. Launch Complex 21 |url=http://community.livejournal.com/abandonedplaces/1344348.html?#cutid1 |date=2 June 2008}} Recent photos (out of use, but well preserved) of the hard-site test buildings for Mace
* [https://www.youtube.com/watch?v=SabWGCETDN0 Video of MiG-19 performing a ZELL-style launch]

{{Types of take-off and landing}}

[[Category:Types of take-off and landing]]