The propulsion system for the “Ludion” one-man hopper: An Anglo-French rocket engine cooperation 40 years ago

Abstract

The Ludion was a French concept for a military one-man rocket-powered “hopper” aimed at giving troopers the ability to cross rivers or trenches. Sud Aviation was awarded in 1965 the development contract together with Bertin (for the jet pumps) and SEPR was to develop the rocket propulsion system. The propulsion system selected for the “Ludion” was based on the British extensive experience in handling and using isopropyl nitrate as a way of obtaining large amounts of gas able to drive jet engines at start. The idea was to use such a fluid as monopropellant for the propulsion system's gas generator. SEPR integrated this system with pipes and Bertin ejector nozzles and developed a thermally insulated generator able to fulfil all requirements. The main challenges laid in the successful integration of all components and the management of a multi-partners programme and in the design of a highly efficient thermal insulation protecting both generator and pilot from the intense heat generated by the thermal decomposition of isopropyl nitrate (used as a propellant). The first ground test of a Ludion with its rocket propulsion system took place on January 24, 1968, on the test airfield of Villaroche. After 59 tethered and five free flights, the programme was abandoned. It was deemed to be too impractical due to its size, the noise generated and changes in tactical considerations in favour of helicopters and amphibious transports. The first prototype is now displayed at the Paris Le Bourget Air & Space Museum.