Rocket sled. Which, Wikipedia writes, “is a test platform that slides along a set of rails, propelled by rockets.
“As its name implies, a rocket sled does not use wheels. Instead, it has sliding pads, called ‘slippers,’ which are curved around the head of the rails to prevent the sled from flying off the track. The rail cross-section profile is that of a Vignoles rail, commonly used for railroads.
“A rocket sled holds the land-based speed record for a vehicle, at Mach 8.5.”
(Rock ATE en shlit ten.)