Glenn Impacts Main Engine Design
Pioneering work at NASA's Glenn Research Center paved the way for today's space shuttle main engine.
The first firing of a hydrogen/oxygen rocket engine occurred in 1953 at NASA Lewis Flight Propulsion Laboratory (now NASA Glenn Research Center). It demonstrated that such a source of power could be controlled. That early work in chemical propulsion eventually led to the space shuttle main engine, the first reusable chemical propulsion engine.
Image right: An engineer works on the Space Shuttle Main Engine Technology Program at NASA Lewis (now NASA Glenn) in the 1980s. Credit: NASA
The engine's gas turbines drive turbopumps that move hydrogen and oxygen at temperatures as low as -400 deg. F and at pressures as high as 7,000 pounds per square inch -- about 10 times the pressure achieved by most fire department pumpers. These turbopumps were designed using many concepts developed at NASA Glenn in the 1950s and 1960s for jet engines.
NASA Glenn scientists also established design principles for the numerous seals used in the space shuttle main engines and conducted extensive bearing investigations. The results were incorporated into the design of the special bearings that support the engine's turbine shaft.
The injector in the main combustion chamber uses a unique concept called a coaxial injector element, which was developed and patented by NASA Glenn engineer Samuel Stein. As a result of coaxial injector testing performed at NASA Glenn, the main engine's combustor can achieve greater than 99 percent combustion efficiency, the highest of any rocket engine.
The main injector uses cooled baffle elements, developed at Glenn in the 1960s to control pressure waves that could destroy the engine. Pressure waves in the space shuttle main engine combustion chamber are also controlled by acoustic cavities. Testing by Glenn engineers determined the most effective size and location of these cavities, which act somewhat like cavities in acoustic ceilings.
NASA Glenn engineers also conducted tests that provided the heat-transfer data necessary to design the proper wall thickness for the combustion chamber where temperatures reach 6,000 deg. F, approximately twice the melting point of steel.
Early efforts at Glenn to develop the electroforming process provided the basis for fabrication methods used to manufacture the space shuttle main engine thrust chambers. Electroforming is similar to the process used to plate chrome onto car bumpers. Nickel is electroformed onto the copper material of the thrust chamber to provide the required combination of strength and heat-transfer characteristics.
Testing of variously shaped nozzles in NASA Glenn's high altitude chambers provided data for determining the best length and shape of the space shuttle main engine nozzle. A delicate balance must be achieved between a short nozzle, which is desirable when the engine first fires on the launch pad, and a long nozzle and larger exit area, required when the engines are operating in the vacuum environment of space. NASA Glenn tests supplied the data engineers needed to choose the right nozzle size.