NASA completes testing of sophisticated Mars rover
BY STEPHEN CLARK
Posted: August 14, 2011
Engineers finished up functional testing of the $2.5 billion Mars Science Laboratory last week, verifying the Curiosity rover can make it to Mars and pursue scientific clues that the planet may have once harbored life.
The Curiosity rover's destination is Gale crater, a scenic impact site carved out of the Martian landscape when a comet or asteroid stuck the planet long ago. The crater spans 96 miles across, and Curiosity is aiming for a narrow target at the base of a lofty mountain towering nearly three miles high.
"We just wrapped up our last functional test of the vehicle," said Dave Gruel, the manager overseeing MSL's assembly, test and launch operations. "Our functional test campaign included things like showing the vehicle can float through the solar system, showing we can successfully go and do the entry, descent and landing phase, get down to the surface and actually deploy the arm, deploy the mast, take images and things of that nature."
Over the next few weeks, technicians working inside an ultra-clean processing facility will stow the rover's high-gain communications antenna, retract and lock the robot arm, latch its camera mast for launch, and tuck its six wheels into the configuration for the trip to Mars.
Torsten Zorn, an integration test engineer, said the front wheels will be toed in 50 degrees and the rear wheels angled 10 degrees for launch.
"We'll just fold it up like a little insect and latch everything down," Zorn said.
NASA allowed news reporters and photographers into the clean room Friday to see the rover as it will appear on the surface of Mars. Concerned that germs from Earth could contaminate the mission's scientific results, everyone allowed near the rover must wear special coveralls, a hood to cover the head and a mask.
"We're going to start stowing the vehicle for launch," Gruel said. "What that basically means is we're going to take the arm, and we're going to put the arm nice and close up against the vehicle. We're going to put the mast down. We're going to tuck the mobility system nice and tight. Once we're in that configuration, that's the configuration the rover is in at launch."
Engineers will conduct thorough checks of the spacecraft's electrical system in parallel with the mechanical work.
The rover arrived at Kennedy Space Center on June 22 aboard a U.S. Air Force C-17 cargo plane. The mission's heat shield and aerodynamic shell was shipped to KSC in May.
Once Curiosity is in launch shape, crews will place the rover beneath a rocket-powered descent stage.
Similar to previous Mars landers, Curiosity will plow through the planet's thin atmosphere safeguarded by a heat shield attached to a nearly 15-foot-wide aeroshell, larger than the diameter of the Apollo command module.
Engineers will encapsulate the rover and descent stage inside the cone-shaped aeroshell this fall. The final act will be adding the cruise stage, the spacecraft bus that will shepherd the rover from Earth to Mars during the nearly 10-month cruise through the solar system.
"That forms the configuration that we will launch on the Atlas 5 in November of this year," Gruel said. "We will actually complete our encapsulation process probably in the last week of October. We then have to fuel the cruise stage. The Atlas team then brings the [payload] fairing out here, and we encapsulate inside [the processing] facility. Then we head out to the launch site for launch on the 25th of November."
Workers will add the rover's plutonium power source when the probe reaches the launch pad and is mated to the Atlas 5 rocket.
Once the craft endures the 3,800-degree Fahrenheit heat of atmospheric entry at Mars, a parachute will deploy to slow its velocity, and the craft will jettison the blackened heat shield.
Then the real fun begins.
After falling free of the parachute about a mile above the surface, eight small rocket engines mounted to a descent stage will fire up to maneuver the nuclear-powered rover to a safe landing zone.
With pulsing radar beams constantly giving its computer altitude and motion updates, the descent stage will throttle the thrusters for control and lower the nearly 2,000-pound rover to the surface on three bridles.
But the sky crane architecture has never been tried before. Mars surface missions up to now have used cushioning airbags or rocket-powered landers with legs.
"It's pretty overwhelming," Gruel said. "We all got to see the Juno launch a couple of days ago and realizing that we are next up, that the next rocket that's going to be on that pad is going to be for MSL is a pretty humbling experience for the team. We all realize that the finish line is upon us with respect to getting Curioisty ready to launch."
All the testing so far was meant to ensure any last-minute bugs were caught on the ground and didn't crop up during the flight.
"We're all really confident that we've exercised Curiosity to the best of our ability and what's next up for Curiosity is actually get down on the surface of Mars and show us what she's capable of doing."