Bell Aerosystems began development of a rocket pack which it called the "Bell Rocket Belt" or "man-rocket" for the US Army in the mid 1950s. It was demonstrated in 1961 but 5 gallons of hydrogen peroxide as fuel for 21 seconds of flight time did not impress the army and development was cancelled. This concept was revived in the 1990s and today these packs can provide powerful, manageable thrust. This rocket belt's propulsion works with superheated water vapour. A gas cylinder contains nitrogen gas, and two cylinders containing highly concentrated hydrogen peroxide. The nitrogen presses the hydrogen peroxide onto a catalyst, which decomposes the hydrogen peroxide into a mixture of superheated steam and oxygen with a temperature of about 740 °C. This was led by two insulated curved tubes to two nozzles where it blasted out, supplying the propulsion. The pilot can vector the thrust by altering the direction of the nozzles through hand-operated controls. To protect from resulting burns the pilot had to wear insulating clothes.