gas turbine engines on land, sea and air. Turbochargers are used on piston engines. Gas turbines have very high power densities (i.e. the ratio of power to mass, or power to volume) because they run at very high speeds. The Space Shuttle main engines used turbopumps (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen) into the engine's combustion chamber. The liquid hydrogen turbopump is slightly larger than an automobile engine (weighing approximately 700 lb) with the turbine producing nearly 70,000 hp (52.2 MW). Turboexpanders are used for refrigeration in industrial processes. See also Balancing machine Euler's pump and turbine equation Helmholtz's theorems Rotordynamics Rotor–stator interaction Secondary flow Segner wheel Turbo-alternator Turbodrill Turbofan Turbojet Turboprop Turboshaft Turbine-electric transmission Notes Further reading Layton, Edwin T. "From Rule of Thumb to Scientific Engineering: James B. Francis and the Invention of the Francis Turbine," NLA Monograph Series. Stony Brook, NY: Research Foundation of the State University of New York, 1992. External links Turbines Jet engines Power engineering Gas technologies