This is a model of the rocket ram proposed by the early 15th century Italian military engineer Giovanni da Fontana in his sketchbook finished in 1420. The ram, or rocket car, was made of wood and was meant to help break down or breach the walls or gates of enemy fortifications. It ran on rollers and was propelled by a rocket.
Da Fontana apparently never built the device. The model was built especially for the National Air and Space Museum and was donated to the Museum in 1976 by the George Marsden Design Company.
George Marsden Design