Back in business: World's largest wind tunnel picks up where it left off

  • Published
  • By Philip Lorenz III
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  The U.S. Air Force Arnold Engineering Development Center's National Full-Scale Aerodynamics Complex (NFAC) resumed its historic role in supporting space exploration with the recent successful dynamic loads and developmental testing of NASA's Mars Science Laboratory's massive parachute.

The MSL is scheduled to launch in 2009.

The last test before NFAC was mothballed in 2003 was on the NASA Mars Exploration Rover parachute in the 80-foot-by-120-foot wind tunnel.

However, the significantly larger size, mass and weight of the MSL payload and the forces acting upon the large parachute were unprecedented in what has flown before. 

NASA's Jet Propulsion Laboratory, Pasadena, Calif., chose the unique environment of NFAC, located on the NASA Ames complex at Moffett Field, Calif., for conducting the recent tests. 

NFAC has the world's largest wind tunnel, and it offers a controlled environment that is preferred over aerial drop testing.

By Dec. 14, when the second round of tests concluded, it was clear the parachute had survived most of the rigors of descent through the Martian atmosphere as simulated in the tunnel.

"We learn something new every time we put the parachute up," said Justin McClellan, NFAC's test director on the recently completed project. "In this second phase, we were testing the parachute in a manner similar to how it will be tested during its full space flight qualification test, still planned for fall of 2008."

Earlier in the fall, the same team had run a series of early entry tests at NFAC on the parachute to help set test conditions and determine what supporting hardware and data collection systems would be needed for the subsequent test work.

Joe Sacco, NFAC test director on the initial project, said these earlier tests helped to determine how the MSL parachute would fly and what its subsonic trimming would be under simulated flight (descent) conditions. The tests were run in NFAC's 80-by-120-foot wind tunnel.

"We had never tested a parachute this large before in the facility," he said. "So there were questions about exactly how we should do it and what kind of techniques we might need to use. We hope to use the data from those and the more recent tests to establish flight qualifications."

JPL, which is developing and building MSL, had three main objectives for the earlier test series.

One was to determine if the parachute would fly in the tunnel in a stable manner and to verify the functionality of the test support hardware. 

The second was to measure the response of the tunnel itself to the presence of the parachute as it blocked 25 percent of the tunnel area and there was a risk that it could cause excessive stresses in the fan blades that drive the tunnel. 

The third was to was to practice operations and plan for the mortar fired deployments needed in later testing.

McClellan said the MSL parachute testing, both the initial series and the recently completed work was all part of an almost seamless collective effort.

"This was a very dynamic group - our customers were constantly trying to think outside the box and come up with new and innovative ideas and we helped push those ideas and see them come to bear fruit," he said. "It was such a collaborative effort between JPL, Pioneer and all the guys at NFAC, the lines were really blurred as to whose idea was any one individual's."

NFAC's 40-by-80 and 80-by-120-foot wind tunnels at are primarily used for determining the low and medium-speed aerodynamic characteristics of high-performance aircraft, rotorcraft, and fixed wing, powered-lift Vertical/Short Take-off aircraft. These facilities are operated by the Air Force for the Department of Defense, industry, NASA, and other government agencies.

The tunnels are used primarily to support technology development programs in aerodynamics, dynamics, and acoustics, including evaluation of full-scale advanced aircraft and their components, and validation of computational methods.