Mars Science Laboratory begins cruise to red planet
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: November 26, 2011
KENNEDY SPACE CENTER, FL--A towering Atlas 5 rocket flashed to life and vaulted into space Saturday, putting on a spectacular weekend sky show as it boosted NASA's $2.5 billion Mars Science Laboratory rover on an eight-and-a-half-month 352-million-mile voyage to the red planet.
It is the most complex and scientifically ambitious Mars mission yet attempted, one that promises to revolutionize humanity's understanding of martian history and whether the planet ever had -- or still has -- the raw materials and an environment hospitable to the evolution of life.
The Curiosity rover is "really a rover on steroids," Colleen Hartman, a senior manager in NASA's science directorate, said before launch. "It's an order of magnitude more capable than anything we have ever launched to any planet in the solar system. It will go longer, it will discover more than we can possibly imagine."
The mission got underway on time at 10:02 a.m. EST (GMT-5) when the rover's United Launch Alliance Atlas 5 rocket roared to life and lifted away from launch complex 41 at the Cape Canaveral Air Force Station.
Equipped with four solid-fuel strap-on boosters for additional power, the 1.2-million-pound Atlas 5 blasted off with nearly 2 million pounds of thrust, majestically climbing away from its seaside pad and arcing away to the East through scattered clouds as it accelerated toward space.
Trailing a churning cloud of fiery exhaust, the strap-on boosters were jettisoned just under one minute and 55 seconds into flight and the rocket continued on its way under the power of its Russian-built RD-180 first-stage engine.
Four-and-a-half minutes after takeoff, the first stage dropped away and the hydrogen-fueled RL10 engine at the base of the Centaur second stage ignited, powering the spacecraft toward a planned 102-by-201 mile high parking orbit 11-and-a-half minutes after launch.
Telemetry from the rocket was spotty during a 20-minute coast to the Mars departure point, but the Centaur re-ignited as planned for a final eight-minute burn, accelerating the spacecraft to an Earth-escape velocity of 22,500 mph. A few moments after that, at 10:46 a.m., the Mars Science Laboratory and its solar-powered interplanetary cruise stage separated from the Centaur, completing the launch phase of the mission.
"The launch vehicle has given us a great injection into our trajectory, and we're on our way to Mars," Project Manager Peter Theisinger said in a statement. "The spacecraft is in communication, thermally stable and power positive."
During the eight-and-a-half-month cruise to Mars, engineers at the Jet Propulsion Laboratory in Pasadena, Calif., will test the rover's instruments, adjust the craft's trajectory and tweak the control software that is vital to the mission's success.
"Our first trajectory correction maneuver will be in about two weeks," Theisinger said. "We'll do instrument checkouts in the next several weeks and continue with thorough preparations for the landing on Mars and operations on the surface."
If all goes well, Curiosity will reach the red planet on Aug. 5 for a nail-biting six-minute plunge to the floor of Gale Crater.
Just before entry, the cruise stage will re-orient the spacecraft and small weights will be ejected to change the entry vehicle's center of gravity, providing the lift necessary for a guided descent.
Using an advanced heat shield to endure entry temperatures up to 3,400-degree Fahrenheit, the rover's flight computer will fire small rocket thrusters as required to fine tune the craft's fight path based on actual atmospheric conditions.
Four minutes and 15 seconds after entry, at a velocity of about 900 mph and an altitude of roughly 7 miles, a huge braking parachute will unfurl, slowing the probe's plunge to a more manageable 180 mph. At that point, at an altitude of just under 1 mile, the rover and its "sky crane" rocket pack will fall free of the parachute assembly for a powered descent to the surface.
For flight controllers at JPL, monitoring the computer-controlled descent, this will be the moment of truth.
Too large to use airbags like those that cushioned NASA's Pathfinder, Spirit and Opportunity rovers, Curiosity will rely instead on landing rockets positioned above the rover, avoiding the challenge of coming up with a reliable way to get a one-ton vehicle off of an elevated, possibly tilted lander.
Using a high-precision radar altimeter, sophisticated attitude sensors and complex software, Curiosity's radiation-hardened computer will control the dual rockets on each corner of the sky crane to achieve a steady 1.7 mph vertical descent rate.
Just before touchdown, the rover will be lowered from the hovering sky crane on a long tether, gently setting down on its six 20-inch-wide wheels. At that point, the bridle will be cut, the sky crane will fly away to a crash landing and flight controllers will begin checking out and activating Curiosity.
Thanks to the sky crane and the guided entry, mission planners were able to select the most scientifically interesting target -- Gale Crater -- from a list of carefully considered candidates.
Starting on the floor of the vast crater and then slowly ascending the central peak through canyons and ravines visible in orbital photography, "we're basically reading the history of Mars' environmental evolution," said MSL project scientist John Grotzinger.
"We start at the bottom, where ... the clays are, we go up farther, there are the sulfates, and then we go to the top of the mound and we get rocks that we thing were formed ... in the drier, more recent phase of Mars," he said.
Climbing the central peak with its exposed layers will be "analogous to what you would see in the Grand Canyon," Grotzinger said. "So our rover is going to be like John Wesley Powell going down the Grand Canyon on Mars, looking at this thick stack of strata."
The mission is expected to last at least two years and possibly longer if the rover stays healthy and no major malfunctions occur.
The primary goal of the mission is to determine if Mars ever had a habitable environment at some point in its history, areas where the three necessities of life -- water, energy and carbon compounds -- existed in concert.
The first two are now well established, thanks to earlier Mars missions that showed Mars was once a much warmer, wetter world. But the search for carbon compounds is a much more challenging proposition.
"The promise of Mars Science Laboratory, assuming that all things behave nominally, is we can deliver to you a history of formerly, potentially habitable environments on Mars," Grotzinger said. "But the expectation that we're going to find organic carbon, that's the hope of Mars Science Laboratory. It's a long shot, but we're going to try."
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