Zero length launch

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F-100D-60-NA (sn 56-2904) in trial of zero-length-launch system. Pilot is Maj. R. Titus. (usaf photo)

The zero length launch system or zero length take-off system (ZLL, ZLTO, ZEL, ZELL) was a system whereby jet fighters and attack aircraft were intended to be placed upon rockets attached to mobile launch platforms. Most zero length launch experiments took place in the 1950s, during the Cold War.

The primary advantage of a zero length launch system is the elimination of the need for a vulnerable airfield for takeoffs. In the event of a sudden attack, air forces could field credible air defenses and launch airstrikes even with their own airbases destroyed. Although launching aircraft using rocket boosters proved to be relatively trouble-free, zero length launch systems still required a conventional runway if the aircraft was expected to land. Bulky mobile launching platforms also proved to be expensive to operate and difficult to transport. Security would also have been an issue with mobile launchers, especially if equipped with nuclear-armed strike fighters.

The United States Air Force, Luftwaffe, and Soviet Air Force all conducted experiments in zero length launching. All works upon ZLL aircraft were abandoned due to logistical concerns and the increasing efficiency of guided missiles.

Manned Aircraft Involved in ZLL Testing

Republic F-84D Thunderjet
North American F-100D Super Sabre
Lockheed F-104 Starfighter
Mikoyan-Gurevich MiG-19 "Farmer"
North American XF-108 Rapier - (aircraft program cancelled)

The desire to field combat aircraft without depending on vulnerable landing strips also motivated development of aircraft capable of vertical (VTOL) or short (STOL) takeoffs or landings. Examples of these include the Hawker Siddeley Harrier and the McDonnel Douglas F-15S/MTD.