WASHINGTON – When engineers at NASA’s Jet Propulsion Laboratory (JPL) realized they had to start from scratch in order to safely land a Mini Cooper-sized rover on the surface of Mars, they realized simulating the fiery descent and landing widely known as the “Seven Minutes of Terror” would require an unprecedented amount of computer simulations and testing.
They turned to companies like Siemens PLM Software to help conduct thermal design and analysis studies to determine how the Mars Science Laboratory spacecraft carrying the Curiosity rover would behave as it descended through the thin Martian atmosphere made up mostly of carbon dioxide and sulfur dioxide. NASA engineers had to figure out how to protect the spacecraft moving at speeds as high as 13,000 miles per hour as it descends to its landing site from temperatures as high as 1,447 degrees C.
If the spacecraft survives the fiery entry into Mars’ atmosphere and its sky crane successfully lands Curiosity on the surface early Monday morning (Aug. 6), the rover must then be able to operate at temperatures ranging from -135 degree C to +50 degrees C.
Tim Nichols, managing director of Siemens PLM Software (PLM stands for Product Lifecycle Management) said in an interview that program managers also had to find ways to model the G forces on the spacecraft during entry, descent and landing. Early in the risky program, Nichols continued, JPL engineers realized they needed a far more integrated approach to simulating the hazardous automated landing and the spacecraft’s predicted behavior as a way to minimize risk.
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The automated entry, descent and landing sequence of the Mars Science Laboratory spacecraft that will use a risky sky crane landing technique to lower the Curiosity rover to the surface of Mars. (Source: NASA Jet Propulsion Laboratory)
“We provided the toolbox for designing, testing and ultimately manufacturing this robot,” Siegfried Russwurm
, CEO of Siemen’s Industry Sector, said during the recent Farnborough Air Show. “Our virtual testing was really used to do things where you would not have a physical prototype” of the spacecraft or rover.
The company claims its integrated suite of tools called NX pulled together disperate CAD, CAE and CAM tools to allow JPL engineers to “capture all of the DNA of [the Mars Science Laboratory] design” and determine, for instance, whether they “over-designed it,” Nichols said. NX was used to develop many of the mechanical portions of the Mars Science Laboratory spacecraft, particularly the thermal control systems for entry, descent and landing as well as for surface operations at Curiosity’s planned landing site at Gale Crater.
The integrated approach allowed JPL engineers to “refine, refine, refine” a never-before-attempted spacecraft design, Nichols said. Among the factors engineers had to take into account in their design were thermal loads and the effects of radiation exposure after the nine-month, 354 million mile trip to Mars.
Doug McCuistion, director of NASA’s Mars Exploration Program, credited the Siemens software with helping engineers manage the evolving design of spacecraft systems. “It was very useful to be able to test the parts and test the interfaces before we had to actually assemble” the spacecraft, he said at Farnborough.
Despite the extensive simulations and testing, program officials acknowledge there is only so much risk that can be eliminated when attempting a fully automated landing of a roughly 1-ton rover on Mars using an untried landing technique like a rocket-powered sky crane. Among the unknowns will be wind gusts during the spacecraft’s descent, dust storms near the surface and large rocks and loose sand near the landing site.
We’ll find out whether all this effort paid off about 14 minutes after Curiosity either lands or crashes on Mars this coming Monday morning.Related story:NASA preps spacecraft for risky Mars landing attempt