The Sud-Aviation Ludion SA-610 is a French ultra-light rocket-lift VTOL aircraft first displayed at the 1967 Paris Air Show. The Ludion was designed to carry a single person with personal equipment and a payload of 30 kg at a height of 200 meters for a distance of 600 meters at a speed of 100 km/h.

AEROSPATIALE LUDION SPECIFICATIONS

• Engine : SA-610 "SEPR"
• Type : S178
• Thrust : 180 daN
• Gas Pressure : 18-30 bar
• Speed max.: 100 km/h
• Altitude max.: 600 m
• Autonomy : 30 min
• Fuel : Isopropyl Nitrate
• Width: 1,485 mm
• Length: 1,950 mm
• Height: 1,600 mm
• Weight: ~ 90 kg

The Ludion operated with a monopropellant fuel of the family of n-propyl nitrates, an up-and-coming monopropellant studied during the space race of the 1960s, with propulsion performance and characteristics slightly higher than hydrogen peroxide. However, even though it was safer to handle and transport (it was classified as a flammable, similar to gasoline), it was not a reliable monopropellant to use in a rocket motor, as it suffered from what is called "compression deflagration".

This anomality, is a behavior some combustible liquids exhibit, whereby they become flammable or detonate when suddenly compressed to 2 - 5 times its previous pressure state. Hence, as long as the pressure of the n-propyl nitrate was kept constant, not matter what value, nothing happened, provided it was pressurized very gently. If the liquid experienced a sudden (pulse) presurization, as when a valve is shut off, it spontaneously detonated.

The Ludion also made use of multi-nozzle design exploiting the benefits of lift augmentation through the use of large diffuser or eductor, converting the low-mass, high-velocity of gases to high-mass, low-velocity impulse.