Zero-length launch

The zero-length launch system or zero-length take-off system (ZLL, ZLTO, ZEL, ZELL) is a PTOL method whereby jet fighters and attack aircraft could be launched using rocket motors 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 missiles 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. 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 superpowers, thus the ability to remove this dependence upon lengthy runways and airbases was highly attractive.