Team AEDC celebrates the landing of NASA's Mars Science Lab

  • Published
  • By Philip Lorenz III
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  As news broke of NASA's Mars Science Laboratory (MSL) "Curiosity" rover's successful landing on the "Red Planet" Aug. 6, a number of people affiliated with the Arnold Engineering Development Complex (AEDC) were paying close attention to the story.

"Curiosity" is the most highly advanced, mobile robot with the heaviest overall payload ever sent to another planet to investigate Mars' ability, both past and present, to sustain microbial life.

AEDC's role in supporting the MSL program has included evaluating the aerothermal loading of the heat shield at the complex's Hypervelocity Tunnel 9 facility in Silver Spring, Md., and assessing thermal protection system material candidates for the MSL's heat shield at the complex's central location in Tennessee. In addition, NASA and AEDC's engineers tested the MSL's full-sized parachute in the world's largest wind tunnel at National Full-Scale Aerodynamic Complex (NFAC) in California.

AEDC Hypervelocity Tunnel 9 Director Dan Marren said he takes great pride in MSL's successful landing, considering AEDC's role in contributing to the program on several fronts.

"AEDC has provided aerothermal characterization of the heat shield design at our Hypervelocity Wind Tunnel 9, material characterization in Arnold's arc jet facilities in Tennessee, and parachute testing at full scale in AEDC's National Full-Scale Aerodynamic Complex, located at NASA's Ames Research Center in Moffett Field, Calif.," Marren said. "NASA and the Air Force maintain a unique partnership when it comes to research that is in both our interests."

AEDC's Arc Heater facilities

Mark Smith, Aerospace Testing Alliance's senior engineer and scientist at AEDC's Space and Missiles Systems Project Section, oversaw testing done on the MSL's aerothermal protection material candidates at AEDC's H2 arc heater facility in 2007. He said it was a privilege to play a role in supporting NASA on such a milestone project.

"The AEDC H2 [test cell] provided some very high shear test conditions which were not available at [NASA] Ames, and that's why they decided to do some testing here at AEDC."

Smith said the testing proved to be more productive than anyone anticipated.

"As it turned out, their primary candidate material for the MSL heat shield was giving questionable results at some of the AMES [arc jet] conditions," he said. "AEDC really confirmed that it was not going to be satisfactory for the heavier MSL vehicle with its higher shear levels.

"As a result of these tests at Ames and AEDC, NASA decided to go with a thermal protection material under test for [the] Orion [Crew Exploration Vehicle] for MSL. It worked out well, and was a real boost for our team to be able to work with NASA on a planetary probe program like this."

AEDC's National Full-Scale Aerodynamic Complex

Evaluation and qualification of MSL's full-scale parachute decelerator system took place at NFAC, AEDC's remote site located in northern California, between 2007 and 2009. A series of full-scale wind tunnel tests were designed and conducted to qualify and validate the design and final flight articles.

MSL's Curiosity rover is unprecedented in its size, weight, and complexity and as such requires an extremely large decelerator to slow its descent to the surface of Mars.

When fully inflated, the MSL parachute spans more than 50 feet across and reacts with more than 65,000 pounds of drag. Full-scale testing on flight-like articles was required to prove the design, materials and fabrication techniques were capable of surviving the rigorous mission requirements.

NFAC provided a uniquely suited test environment as the only wind tunnel facility in the world capable of testing such a large decelerator.

NFAC's drag scale is only capable of measuring up to 50,000 pounds, requiring NFAC to devise a new system for supporting the parachutes and measuring their drag.

Joe Sacco, NFAC's deputy director, served as the test director for the first test in the MSL series.

"We worked with John Perry, a NASA Ames design engineer, to come up with a great support structure that the Ames shops could fabricate and [that] would handle 100,000 pounds of drag," Sacco said, referring to the process.

Sacco and the test team oversaw testing of several parachutes on this support structure, commenting that one of the final design assets was tested to nearly 97,000 pounds.

To qualify the parachute design for flight and verify the workmanship of the final assets, NFAC worked with Jet Propulsion Laboratory personnel to devise a test campaign wherein a single flight-identical parachute was deployed 10 times.

Justin McLellan, NFAC's Test Engineering Group lead served as test director for several phases of the MSL test series.

"Three canopies were built from final design: the one that just landed Curiosity, one backup for the mission, and one to test here at NFAC. Our final test series with that canopy was flawless," he said.

Sacco and McLellan said they were impressed with the seamless collective effort shown by the MSL test team throughout the test series.

Pat Goulding II, test director on the final verification test of the flight-lot asset, added that the test team of engineers and technicians from Jet Propulsion Laboratory, Pioneer Aerospace Corporation (the parachute supplier), Ames Research Center, and NFAC "displayed great synergy, flexibility, and professionalism in adjusting to the test series' many challenges and finding ways to make the program a success."

Hypervelocity Tunnel 9

Regarding the aerothermal testing done at Tunnel 9, Lafferty, their technical director, said he also appreciates the ongoing partnership with NASA and the trust their team places in AEDC's workforce and the complex's unique testing capabilities.

He said the challenges facing NASA and AEDC with validating the design and materials under consideration for MSL made the missions' success even more impressive.

"The Mars Science Laboratory is a multifaceted NASA project to land a very large rover on the surface of Mars - the largest one they've ever built," Lafferty said. "It's about the size of VW Beetle in both wheel base and weight.

"We were involved with characterizing the aerothermal environment, or the aerodynamic heating to put it more in lay language, around the capsule that occurs during atmospheric entry into Mars' atmosphere."

Lafferty said the test helped NASA's engineers to better understand the aerothermal stresses the MSL would have to withstand to survive atmospheric entry and enable a safe landing on Mars. In 2006, Lafferty was working on that testing with Dr. Brian Hollis, who is now a senior technical lead in the Aerothermodynamic Branch at NASA Langley Research Center.

"We knew that the flow and the heat shield would be turbulent," Hollis said. "We needed the wind tunnel test facility where we could get a very high Reynolds number to get us turbulent flow data."

AEDC Tunnel 9 fit the bill because...they've got a huge Reynolds number range that they can hit and that seemed the best place to go to get some data on turbulent heating."

Hollis also had praise for Tunnel 9 and their workforce, including Arnold Collier, the facility's lead engineer on the project at the time.

"[They have a] very professional organization with impressive capabilities," he said. "We got what we wanted for the money. It was a very good experience."