The XP-21 Firebird 1 was the first gas turbine automobile ever to be built and tested in the United States. Designed strictly as an engineering and styling exercise, Firebird 1 was intended to determine whether the gas turbine could be used as an efficient and economical powerplant for future vehicles.

The idea for Firebird 1 originated with Harley J. Earl, the legendary GM Styling Vice President, who also designed the car's aircraft-inspired fiberglass-reinforced plastic body. The engine, termed "Whirlfire Turbo-Power," was developed under the direction of Charles L. McCuen, then general manager of GM Research Laboratories Division.

Unlike a jet airplane, which develops thrust through the action of exhaust gas through a tailcone, the Whirlfire Turbo-Power engine propelled the Firebird 1 through a power turbine acting on the rear wheels via a transmission. The engine was capable of 370 hp at a power turbine speed of 13,000 rpm.

source: wiki.gmnext.com

By 1953, the research team had produced the Firebird XP-21, later referred to as the Firebird I, which was essentially a jet airplane on wheels. It was the first gas turbine powered car tested in the United States. The design is entirely impractical, with a bubble topped canopy over a single seat cockpit, a bullet shaped fuselage made entirely of fiberglass, short wings, and a vertical tail fin. It has a 370 hp (280 kW) Whirlfire Turbo Power gas turbine engine, which has two speeds, and expels jet exhaust at some 1,250 °F (677 °C). The entire weight of the car is 2,500 lb (1,134 kg).

At first, Conklin was the only person qualified to drive it, and he tested it up to 100 mph (160 km/h), but upon shifting into second gear the tires lost traction under the extreme engine torque and he immediately slowed down for fear of crashing. The car was later test driven at the Indianapolis Speedway by race car driver Maury Rose. The car was never actually intended to test the power or speed potential of the gas turbine, but merely the practical feasibility of its use. The braking system differs from standard drum systems, in that the drums are on the outside of the wheels to facilitate fast cooling, and the wings actually have aircraft style flaps for slowing from high speed.

source: Wikipedia