The now-defunct
Rocket Racing League utilized a highly modified Velocity XL FG airframe and an
Armadillo Aerospace 2,500 pound thrust
liquid oxygen (LOX) and
ethanol rocket engine in both its Mark-II X-Racer and Mark-III X-Racer demonstration vehicles. The Mark-II utilized a standard fixed-gear Velocity XL airframe, modified for rocket propulsion. The Mark-III airframe was more extensively customized during manufacture, explicitly for rocket racing, with a canopy top, center seat and control stick and other enhancements, in addition to the rocket propulsion added to the Mark-II. ==Specifications (XL-RG)==