Curiosity, NASA's roving space laboratory, touched down on the red planet on Aug. 5. Its nearly nine-month journey was not an easy one, particularly in the final few minutes when the rover entered Mars' atmosphere and had to complete a complicated set of maneuvers to survive.
NASA contracted AEDC to design tests for Curiosity's landing. The center, which is headquartered in Tennessee and has operating facilities across the country, has tested the aerodynamics and structural integrity of weapons systems since the 1950s.
AEDC teams evaluated different components of the rover's landing system. In Maryland, they used Hypervelocity Wind Tunnel 9 to simulate the descent of Curiosity's aeroshell.
In Tennessee, AEDC engineers assessed candidates for the rover's heat shield that would have to endure temperatures higher than the melting point of titanium.
In California, an Arnold team tested Curiosity's supersonic parachute that would slow the rover in the last moments of its Mars descent.
Dave Duesterhaus, an AEDC engineer, helped test the fortitude of the parachute in AEDC's National Full-Scale Aerodynamic Complex at Moffett Field, Calif. He told the Daily Report in a mid August interview that this was the largest parachute ever seen in the wind tunnel.
Working with NASA and Pioneer Aerospace engineers, AEDC technicians calculated that the parachute would experience an initial shock of 65,000 pounds. To be safe, AEDC engineers tested it for 94,000 pounds.
The wind tunnel is 80 feet tall and 100 feet wide. The team built a tripod 40 feet tall to deploy the parachute. Packed in a carriage with mortar and propellant, they launched the chute back 225 feet in the center of a 70-knot airstream—and it was shredded in the wind.
"In the first attempts, the parachute was actually destroyed," said Duesterhaus.
AEDC, NASA, and Pioneer Aerospace examined the photographic data and adjusted the packing of the parachute and the composition of the materials over the course of two years and five different rounds of testing.
"We learned as we went along," said Duesterhaus, noting that after the first series of tests, they installed lights and cameras further back in the tunnel.
They knew the parachute would go through cycles of inflations and deflations, like an undulating jellyfish, as it descended, he said.
The team developed a hands-on way to simulate these fluctuations. They stood inside the tunnel and helped the parachute catch the wind. Then, they cleared out and turned up the speed. By the fifth series, the parachute was ready to deploy from the supersonic capsule and endure the numerous strains of descent.
"The work we do on the ground paves the way," he noted, reflecting on AEDC, adding that aeronautics developers have "been running wind tunnel tests as far back as the Wright brothers."
AEDC's efforts paid off for NASA.
Several hours before dawn on Aug. 5, Curiosity reached Mars' atmosphere at a speed of 13,000 miles per hour.
The rover's aeroshell, designed to withstand heat exceeding 3,500 degrees Fahrenheit, slowed the plummeting capsule to 1,200 mph. At this speed, Curiosity's parachute deployed. As the vehicle slowed, it shed its aeroshell, which crashed into the dust below.
When it reached 200 mph, retrorockets kicked in and lowered the lab-on-wheels to the ground below. The only reported mishap in the landing involved damage to the rover's wind sensor, caused by the rockets kicking up rocks as the rover was lowered, completing its 352 million mile journey.
Duesterhaus said NFAC has more parachute tests for space landings lined up.
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