Introduction
Since 1945, NASA Glenn has been a pioneer in rocket engine and propellant technology. This early research resulted in the development of the Centaur upper stage, one of NASA Glenn's most significant achievements. The technology made significant contributions to the Apollo program, enabling the massive payloads to support human missions to the Moon. Likewise, NASA Glenn has been a pioneer in low-gravity research. This web site documents some of the major contributions to NASA Space Shuttle program.
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Microgravity Science and Applications Experiments
The Microgravity Science program includes experiments performed at reduced gravity that help us to understand the role of gravity on fundamental physical and chemical processes. The NASA Glenn program, which concentrates on the areas of combustion science, materials science and fluids physics and dynamics utilizes the unique reduced-gravity environment of the orbiting Space Shuttle as well as ground-based drop towers and suborbital aircraft flights.
To date, over 40 shuttle missions have carried a total of more than 143 experiments in one or more of several locations including middeck lockers, payload bay carriers (such as the Materials Science Laboratory), Get-Away-Special canisters (GAS Can) and Spacelab. Spacelab, carried in the Shuttle bay, provides a shirt-sleeve environment for the Shuttle crew to perform microgravity experiments. Eleven NASA Glenn experiments were conducted on the Microgravity Science Laboratory (MSL-1) Spacelab mission.
One instrument, the Space Acceleration Measurement System (SAMS), is a versatile system developed to monitor, characterize and record the low-gravity acceleration environment aboard Shuttle. This acceleration data is to be used for correlation with the physical and chemical processes studied in the microgravity experiments. It is planned to be used on all Shuttle flights and in all locations where microgravity experiments are to be flown. Another version was the longest-flying US hardware on the Russian Mir space station. A new unit is aboard the International Space Station.
The NASA Glenn microgravity program is structured around an orderly process that is initiated with ground-based science definition efforts, that may include drop tower and/or aircraft low-gravity experiments, and proceeds to the development of Shuttle experiments where justified. These experiments will lead to the utilization of the International Space Station and commercially developed space facilities which will eventually be mainstays in the microgravity program.
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Space Shuttle Main Engines/Glenn Technology
Pioneering work at NASA's Glenn Research Center paved the way for today's Space Shuttle Main Engines (SSME). The first firing of a hydrogen/oxygen rocket engine occurred some 45 years ago at NASA Glenn and demonstrated that such a source of power could be controlled. That early work in chemical propulsion resulted in the SSME, the first reusable chemical propulsion engine.
Future cyclic testing will determine the effects of repeated firings of the SSME engines to establish the necessary data on engine life. By determining how much distortion the chamber will stand, the point at which the engine should be removed to avoid failure in flight can be determined. These tests will be focused to understand the design tools required and to establish a data base for designing improved reusable engines. The goal is to extend engine life to 50 flights.
The SSME gas turbines, similar to those that power jet aircraft, drive turbopumps that move hydrogen and oxygen at temperatures as low as -400 deg. F and at pressures as high as 7,000 psi, which is about 10 times the pressure achieved by most fire department pumpers. These turbopumps were designed using many concepts developed in the 1950s and 1960s for jet engines.
NASA Glenn scientists established design principles for the numerous seals used in the SSME, and conducted extensive bearing investigations, the results of which were incorporated into the design of the special bearings that support the SSME 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 the coaxial injector testing, the SSME combustor is able to achieve greater than 99% combustion efficiency, the highest of any rocket engine. The main injector assembly also uses cooled baffle elements, developed in the 1960s, to control pressure waves which could destroy the engine.
Pressure waves in the SSME combustion chamber are also controlled by acoustic cavities. Previous testing determined the most effective size and location of these cavities, which act somewhat the same as cavities in acoustic ceilings.
NASA Glenn engineers conducted tests that provided the heat transfer data necessary to design the proper wall thickness (.030 inches or the thickness of ten sheets of paper) for the combustion chamber where temperatures reach 6,000 deg. F, approximately twice the melting point of steel.
Early efforts in developing the electroforming process provided the basis for fabrication methods used to manufacture the SSME 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 SSME 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.
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Space Shuttle Model Wind Tunnel Tests
Verifying design and performance is a key aspect of the Space Shuttle program. As part of this effort, NASA Glenn's Abe Silverstein Supersonic Wind Tunnel (10x10) has been used over the years for a variety of shuttle performance testing. This unique facility, with a total drive power of 275,000 horsepower, provides continuous simulation of high speed atmospheric flight. The 10-foot square by 40-foot long test section can accommodate large scale models including operating jet engines and rocket propulsion systems at speeds ranging from twice to three and one-half times the speed of sound (Mach 2.0 - 3.5) and at altitudes of 50,000 to 150,000 feet.
Shuttle tests performed in the Abe Silverstein Supersonic Wind Tunnel (10x10):
- (1) aerodynamic data on a 2.1% scale model of the solid rocket boosters after their deployment at 140,000 feet
- (2)aerodynamic pressure data on a 3 1/2% scale model of the complete takeoff configuration
- (3) air speed and angle-of-attack on a scale model orbiter forebody
- (4) base heating studies of a 2.25% scale model of the entire takeoff configuration
- (5) engine out loads study on 2.25% scale model.
The engine out loads study in 1988 used a 2.25% scale model (about 6 feet long) complete with operating hydrogen/oxygen fueled main engines, and boosters burning a specially designed gaseous fuel. Tests ran over the full Mach number range and measurements were made with various combinations of the main engines and boosters in operation. These studies provided information about the structural loads encountered on all components of the vehicle (orbiter, external tank, and boosters) with a non-burning engine during the initial launch phase due to existing "wind shear" in the launch pad area. This information helped to determine if the vehicle could be cleared for launch under the existing "wind shear" conditions in case of an engine failure at some point during the liftoff and ascent. This test was considered a "launch constraint" test and was required, along with many others, prior to the launch of a fully loaded shuttle as NASA prepared the shuttle fleet for their return to operational service flights.
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New Electrode for Orbiter Fuel Cell
Fuel Cells Used in Orbiter fuel cell powerplants provide all of the electrical needs of the Shuttle orbiter.There are three fuel cell powerplants on the orbiter and each fuel cell powerplant consists of three stacks of 32 fuel cells.
One of the most important materials used in alkaline fuel cells is the fine metallic powders, called catalysts, which cover the electrode structures. Catalysts made from platinum and palladium had been used in the past. However, fuel cell performance slowly degraded due to sintering (growing together of the particles) which resulted in a loss of surface area. Also short circuits occurred within the fuel cell due to the movement of the metal from one side of the cell to the other when placed in a stack.
In the early 1970s NASA Glenn started to search out a catalyst which would work more efficiently. The catalyst selected was gold alloyed with 10 to 20 percent platinum, resulting in improved performance and service life between overhauls.
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Solar Cell Development for a Power Extension Program
The Power Extension Package (PEP) was designed to be a reusable fold-up solar cell array for use with the Space Shuttle flights requiring extra electrical power. The PEP was to supply 32 kilowatts of electricity allowing the Shuttle to remain in orbit for longer periods of time. In spite of significant technology developments, PEP was never built.
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Shuttle Upgrades for Improved Safety and Performance
NASA is committed to continually improving the safety, reliability and performance of the space shuttle fleet. Glenn is uniquely qualified to contribute in many areas. The following are several improvements under consideration. If implemented, these technologies could double the Shuttle's safety in the next 5-10 years:
- Better Main Engines
- Advanced Health Monitoring System is one of several methods for improving the engines.
- Safer Hydraulic Power
- Electric motors, powered by a bank of lightweight batteries will be developed to power the Shuttle's hydraulic system to provide greater reliability for astronauts in flight and to provide a safer workplace for ground crews. Glenn's advancements in Auxiliary Power Units have been key in this effort.
- Nontoxic Orbital Maneuvering System
- Glenn's work in LOX/Ethanol Torch igniter hardware and Ethanol Critical heat Flux test samples with short explanation aided in research that created nontoxic propellant alternatives. This will reduce ground-processing hazards.
Mission Coverage
NASA Glenn pioneered coverage of each shuttle mission via the Internet as a part of its regular NASA Television Coverage on CU-SeeMe. You can also follow the missions via amateur radio.
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