Kelley Knight Heins
Click for video: John Callas, project manager for the Mars rover mission,
explains how a duplicate rover is being used at NASA's Jet Propulsion Laboratory
in Pasadena, Calif., to figure out how best to free up a rover stuck in Martian sand.
Click on the image to watch an msnbc.com video.
Take two parts diatomaceous earth, add one part clay ... and voila! You've got a blend of simulated Martian sand fine enough to get a rover stuck in.
"It's not a secret formula," John Callas, project manager for the Mars Exploration Rovers, said as he showed us around the place at NASA's Jet Propulsion Laboratory where a stand-in for the Spirit rover is mired in buckets of the stuff.
The semi-impromptu tour, arranged for me and a few other folks who attended last week's American Astronomical Society meeting in Pasadena, Calif., provided an inside look at the clean room where NASA's future Mars rover is taking shape, as well as the not-so-clean room where rovers are put to the test.
Sometimes the tests are conducted long after the real rover has left the building, and that's why an engineering model of the Mars Exploration Rover (known as the Surface System Test Bed rover, or SSTB) is up to its robotic ankles in fake Martian sand at JPL's In-Situ Instrument Laboratory. The real Spirit rover has been stuck in a sand trap and possibly hung up on a rock for more than a month, and its handlers are planning to practice techniques for dislodging it in an indoor pit filled with crushed rock.
Once the pit is set up to duplicate the scene on the west side of the Martian plateau known as Home Plate, mission managers will see which maneuvers have the best chance of freeing Spirit. For example, should the rover try following its own tracks out of the mire, or turn its wheels down the slope to take advantage of gravity? Should it go slow, or go for broke?
"The most important thing is, we don't want to make things worse," Callas explained. The rover could just spin itself in deeper, for example, and get hung up on the pyramid-shaped rock that appears to be sitting beneath its belly. That would immobilize Spirit: After more than five years of rambling, the rover would end its days at that spot.
"If you set the belly on the ground, I think it's 'game over' at that point. We don't want to do that," Callas said.
Kelley Knight Heins
A "Rover Crossing" sign is mounted near the entrance to the Jet Propulsion
Laboratory's In-Situ Instrument Laboratory, where rovers sometimes get grimy.
Last Tuesday, while we were looking in on the pit, workers were shoveling the crushed rock to build a mound with the same 12-degree slant that Spirit is experiencing on Mars. Then a box will be placed on the slope and filled with a sandy soil like the stuff in which Spirit is stuck.
This particular stuff is lighter and fluffier than your typical Martian soil. "It's almost flourlike," Callas said. Duplicating the texture wasn't easy, but after fiddling with the ingredients, engineers came up with the not-so-secret formula Callas described. They hollowed out a hole in the rock pit, set a blue tarp down into the hole, filled it with the simulated sand and then stuck two of the test rover's six wheels way down into the hole for a "shoebox test." The test showed that the mixture seemed to have about the right fluffiness.
The next task is to mix up enough of the faux Mars muck to fill NASA's sandbox and start making dry runs. Eventually, a sequence of maneuvers will be beamed up to Spirit, and the microscopic imager on the end of Spirit's robotic arm will be used to monitor the rover's progress.
It could take weeks for the plan to play out, but that's fully in line with NASA's expectations: When Spirit's twin, the Opportunity rover, was stuck in a sand dune on the other side of the Red Planet, back in 2005, breaking free took weeks as well. Spirit's current situation looks even stickier, Callas said.
At least he and his colleagues are on the right track with their formula for Martian sand. Who knows? Maybe you could even sell the stuff. When our NASA guide, Whitney Clavin, put her hand in the sand, the sensation made her suspect that Mars might not be all that bad a place after all.
"That felt great!" she said later. "That stuff felt like a beach in Thailand."
NASA / JPL-Caltech
Click for video: Full-scale models of three generations of Mars rovers
were put on display at NASA's Jet Propulsion Laboratory in May 2008: Mars
Pathfinder's Sojourner rover is front and center, with the Mars Exploration
Rover (model for Spirit and Opportunity) at left and the Mars Science
Laboratory (now named Curiosity) at right. Click on the image for a
YouTube video of the photo opportunity.
The grimy rover pit is just a few minutes' walk from the immaculate clean room where the successor to Spirit and Opportunity is taking shape. Components for the Mars Science Laboratory, which was rechristened the "Curiosity" rover last month after a naming contest, are spread across the floor of a warehouse-sized white room at JPL's Spacecraft Assembly Facility.
A model of the spacecraft's "Sky Crane" descent stage sits against one side of the room like a giant spider. A couple of saucer-shaped protective shells are in different corners, covered in shiny shrouds. Racks of rover wheels are sitting in the center of the floor, as are two partly assembled models of the rover itself. One is an engineering model, which would be used like the rover in the rocky pit. The other is the flight model, which is due for launch in 2011 and a soft Martian landing in 2012.
"The engineering model will get dirty," the mission's deputy project scientist, Joy Crisp, told us. "The flight model will stay clean."
If NASA stuck with its original plan, Curiosity would have been launched this year. But money troubles and problems with the rover's actuators led mission planners to order a two-year postponement. I asked Crisp whether she was worried that engineers would lose their edge due to the delay.
"That's not our big worry," she replied. "It's still a very big, complex, challenging thing. ... Even with the two years, we're going, 'Oh, gosh, this is hard!'"
Curiosity is designed to drill into some of Mars' biggest mysteries: What types of organic compounds are hidden in the rock and soil? What happened to the liquid water and the carbon dioxide that scientists believe was more abundant on ancient Mars? Could this seemingly dead world sustain life?
For big questions, you need a big rover, and Curiosity will be the biggest rover ever to roam the Red Planet. It measures 10 feet long (3 meters long, not including its robotic arm) and weighs 1,927 pounds (900 kilograms). In comparison, Spirit and Opportunity are both 5.2 feet (1.6 meters) long and weigh in at 384 pounds (174 kilograms) each.
As we looked down into the clean room from a viewing gallery, white-suited workers covered up some of the racks and attached equipment to an overhead hoist system. One worker pulled around what seemed to be a rather low-tech vacuum cleaner, making sure the clean room was as clean as could be. (Crisp guessed that the vacuum was equipped with special HEPA filters.)
Launch vehicle manager Arden Acord stopped by the gallery for a look, and told us that the clean-room workers were practicing the installation procedure for Curiosity's plutonium-fueled power source.
Curiosity will be drawing electricity from a radioisotope thermoelectric generator, or RTG, unlike the solar-powered rovers currently operating on Mars. (Even Spirit and Opportunity use radioisotope units as heaters, however.) Through the decades, RTGs have been used on spacecraft ranging from the Apollo lunar lander to the Mars Viking lander, the Cassini orbiter and the New Horizons mission to Pluto. The units are considered more reliable than solar arrays for providing round-the-clock power, but they tend to generate controversy as well as electricity.
Acord knows full well that RTGs need to be handled carefully, and as little as possible. The units can get as hot as 350 degrees Fahrenheit (175 degrees Celsius). "We're not putting the real one on until [Curiosity is being prepared for launch at] the Cape," he said.
The practice unit has to be installed - quickly, efficiently and safely - through a hole in the side of the spacecraft's backshell, Acord said.
"The health physics people down at the Cape have to know that you know what you're doing," he explained. "That's why you have to do it with a tape measure and a stopwatch."
NASA / JPL
Click for video: Engineers from NASA's Jet Propulsion Laboratory and Alliance
Spacesystems test the range of motion on the Curiosity rover's robotic arm joints.
The instruments have not been mounted on the arm's turret yet, but weights have
been placed on it for testing. Click on the image for a QuickTime video from NASA
that shows the testing procedure (sped up to compress the time).
Other aspects of spacecraft assembly are practiced using similar routines. Engineers recently put an engineering model of Curiosity's robotic arm through its paces, using dummy weights at the end of the arm. The real thing will bristle with tools, including a camera, a spectrometer, a drill, a brush and a tungsten carbide drill.
"This arm is truly amazing," Crisp said. "It's got 75 pounds on the end of this huge robotic arm."
Assembling everything will take months, and if the past is any guide, Curiosity and its earthbound twin will be at least partially assembled far more than once.
"They've put things together and have done some testing - and then they took it apart," Crisp said.
For updates on the Mars missions, check in with our "Return to the Red Planet" section. For more "Inside" reports, click on the links to these archived items: