Supporting Space Testing
Written by Colonel Arthur F. Huber II
Long before man made it to the moon or the Patriot missile became known as the “scud buster,” these systems occupied the wind tunnels, arc heaters and ranges of AEDC. Located on 4,000 acres of the 40,000-acre Arnold Air Force base in South Central Tennessee, AEDC has been on the cutting edge of space and missile technology for more than 50 years.
AEDC has an unprecedented capability for testing and evaluating rocket engines under simulated altitude conditions, testing more than 3,000 engines from small STAR motors to large liquid engines like the Saturn IIB. Additionally, missile systems like air-launched cruise missiles (ALCM) and submarine launched ballistic missiles (SLBM) saw numerous hours in both the wind tunnel and engine test facilities. Other systems like the Pershing, Sergeant Missile, Snark and Nike have also spent time in the center’s test cells.
In 1994, the J-6 rocket test facility came online and significantly expanded the center’s capability to test the large and detonable solid rocket motors that will extend the life of the existing intercontinental ballistic missiles (ICBM) force through 2020.
To meet the growing test requirements resulting from increased use of liquid-propellant space boosters, the center returned to testing large liquid storable and cryogenicpropellant rocket engines after a hiatus of nearly 20 years.
The center played a key role in keeping the Titan IV, America’s only expendable, heavy-lift launch vehicle, from being grounded by qualification testing a new Stage II engine and has tested the next generation RL-10 engine.
In the spring of 2007, the center conducted its 27th test on the Peacekeeper Stage III rocket engine to determine the effect of age on the performance of the solid rocket motor.
Part of America’s nuclear deterrent force from 1986 to 2005, the center conducted a variety of testing on the Peacekeeper including development, flight proof, qualification, production quality assurance, and aging and surveillance programs.
AEDC expanded its use of teaming agreements with rocket developers, resulting in a greater range of services and increased responsiveness. For example, a teaming arrangement between AEDC, the Air Force Space and Missiles Systems Center, Lockheed Martin, Aerojet, TRW, Brown & Root and a host of smaller contractors accomplished the complex facility preparations and test program for the Titan IV engine test program. Similarly, the first test program using the new cryogenic propellant system also involved similar teamwork. In each case, the teaming arrangement allowed its members to contribute their expertise and resources to ensure a more comprehensive, faster test program to fit the customer’s needs.
True to AEDC’s vision of being the center of knowledge for simulated rocket testing, center employees have completed a number of initiatives to improve the scope and quality of the products available to users. These include statistical analysis of aging trends in solid rocket motors, hosting the Minuteman Propulsion System Rocket Engine database, advancements in liquid rocket engine health monitoring, and improved test information handling, storage and retrieval.
Since the late 1950s, AEDC supported the nation’s space exploration programs beginning with Discoverer, Pioneer, Mariner and Surveyor, and continuing with manned spaceflight programs, including Mercury, Gemini, Apollo and the Space Shuttle.
AEDC has supported the development and integration of technologies into operational space systems by simulating the expected operational environment and assessing design performance using a variety of test cells— wind tunnels, thermal vacuum chambers and rocket altitude test cells.
The journey to space began for AEDC March 27, 1957, when the aerodynamic loads a rocket would experience at escape velocity (25,000 mph) were measured in AEDC’s von Karman Gas Dynamics Facility. The following year, engineers in the Engine Test Facility test-fired their first solid-propellant rocket motor for the third stage of a space vehicle. In 1959, the first wind tunnel tests were performed on a model that would evolve into the Saturn V rocket.
During the 1960s, AEDC conducted some 55,000 hours of test support for the Apollo program, involving 25 of the center’s then 40 test facilities. These tests included simulated re-entry tests where thermal protection materials were evaluated. From 1960 to 1968, AEDC conducted more than 3,300 hours of wind tunnel tests, representing more than 35 percent of all of NASA’s Apollo wind tunnel tests. From June 1965 to June 1970, 340 rocket engines were fired in the single largest test program ever conducted at the center to man-rate the Saturn V upper stages.
During the 1970s, NASA’s emphasis shifted from deep space exploration to near Earth space operations and development of Skylab and the space transportation system known as the Shuttle. During that time, AEDC evaluated various model configurations for the space shuttle program, obtaining data on heat transfer, aerodynamic forces and pressures. These tests helped determine the appropriate construction materials and establish baseline flight models for the ascent portion of the mission. The tests also included separation predictions for the two strap-on solid propellant boosters from the shuttle after burnout.
AEDC has supported NASA throughout space shuttle operations, as required, to address potential operational scenarios and anomalies. In the 1980s, wind tunnel tests assessed the effect of a space shuttle main engine failure during the initial stages of ascent.
In the 1990s, space shuttle insulation materials used to protect the Shuttle’s external fuel tanks were reassessed.
AEDC also supported several aspects of the Space Shuttle Return-to-Flight program following the Columbia accident. The objective of the tests was to flight-qualify the redesign of the bipod fixture that connects the liquid fuel tank to the shuttle.
Arnold employees designed and fabricated full-scale calibration models of the original and redesigned components and a 30-percent scale model of the redesigned area. Tests were conducted in 4T, supersonic wind tunnel A and hypersonic wind tunnel C.
The full-scale tests in 4T and Tunnel A measured air pressure on the calibration models and validated the integrity of the full-scale foam models. The sub-scale tests in Tunnel C measured heating rates in addition to air pressure. These tests greatly expanded NASA’s database of localized thermal and pressure measurements in the bipod region and improved their computational fluid dynamics (CFD) data.
AEDC also supported development of technologies on several NASA space probes and experiments. The protective nose tip material for the Galileo Space Probe that sampled Jupiter’s atmosphere in 1995 was evaluated by launching scale models at 11,000 mph down the AEDC 1,000-foot-long hyperballistic Range G.
The NASA/European Space Agency Cassini mission to Saturn deployed a probe to Saturn’s moon, Titan, to assess the moon’s environment. The Huygens probe deployed a parachute for its descent. Drag data was acquired in 16T on a model of the Huygens probe.
In another NASA/ESA joint venture, an Infrared Sub-millimeter Telescope mirror was calibrated in the AEDC 10V sensor calibration chamber to support sky-mapping efforts. Deployment of structures in space after launch presents another considerable design challenge. AEDC tested solar panels for NASA’s Microwave Anisotropy Probe (MAP) to determine if the panels would deploy properly in space and routinely discusses potential investigations supporting development of NASA missions.
AEDC has supported NASA at both its two remote operating locations—the Hypervelocity Wind Tunnel 9 Facility in Silver Spring, and the National Full-Scale Aerodynamic Facility (NFAC) at Moffett Field, Calif., making numerous contributions to NASA. Most recently, both facilities have supported the development of the Mars Science Laboratory (MSL). In 2006, a team at Tunnel 9 successfully completed atmospheric entry testing of the Aeroshell configuration for the MSL, scheduled to be launched in 2009 for a sevenmonth journey to Mars.
At NFAC, engineers successfully conducted dynamic loads and development testing on the MSL’s massive parachute. The parachute, which holds more air than a 3,000-square-foot-house and is designed to survive loads in excess of 80,000 pounds, was attached to a launch arm mounted on a swivel base that allowed the parachute to pitch and yaw under simulated conditions of subsonic entry into the Martian atmosphere.
AEDC has laid the foundation for a new capability—the Space Threat Assessment Testbed (STAT) ground test capability—with the awarding of a contract in October 2008.
STAT will create a realistic space environment to perform developmental and early operational testing of space hardware for the Department of Defense, the National Reconnaissance Office and other agencies against man-made threats and naturally occurring environmental phenomena. STAT will simulate the environmental conditions existing at various orbits and self-induced effects and will emulate man-made threats to perform system test and evaluation, laying the foundation for near real-time connectivity to a satellite operations center. It will allow the center to do integrated system testing, training, tactics, techniques and procedures development and represents a significant step toward the development of an important new national capability. ♦
Colonel Arthur F. Huber II
Colonel Art Huber is the commander, Arnold Engineering Development Center, Air Force Materiel Command, Arnold Air Force Base, Tenn. He oversees the largest and most advanced complex of flight simulation test facilities in the world. The center comprises 58 aerospace test facilities located at Arnold Air Force Base, as well as two geographically separated units, the Hypervelocity Tunnel 9 in Silver Spring, Md., and the National Full- Scale Aerodynamics Complex at Moffett Field, Calif. The test facilities simulate flight from subsonic to hypersonic speeds at altitudes from sea level to space. All NASA manned spacecraft and every high performance aircraft, missile, space launch system and most military satellites in use by the Department of Defense today have been tested in center’s facilities.
Huber was commissioned in 1983 as a distinguished graduate of the Air Force Reserve Officer Training Corps program after completing studies at the University of Notre Dame. He has held a variety of assignments in the Air Force specializing in air and space testing, tactics development and various areas of systems acquisition and sustainment. Huber has been assigned as officer aircrew in multiple aircraft systems accruing over 500 flying hours.