'Seven minutes of terror': Mars rover landing will be a nail-biter
Scientists are utilizing a complicated new 'sky crane' technique for landing the car-sized Curiosity rover on Mars Monday. The hope is that the good luck NASA has had with Mars missions will hold up.
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The bags then deflated, leaving the rover to drive down a ramp and explore its new home. When telemetry indicated that the airbags had deflated and that the rover and its landing platform were upright and healthy, cheers and high-fives erupted in mission control.Skip to next paragraph
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"Going into Pathfinder, there were a lot of people who said: ‘That is a strange, new system; why would you ever consider using such a thing?’" Dr. Lemmon says. “Now, everyone points to that as a way to go.”
The twin rovers Spirit and Opportunity, which arrived at Mars separately in January 2004, also used the airbag approach. Spirit fell silent in March 2010. Opportunity is still exploring its patch of the planet, logging 21.52 miles since its arrival.
The sky crane "looks a bit crazy," acknowledges Adam Steltzner, the rover's lead engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "I promise you it's the least crazy of the methods you could use to land a rover the size of Curiosity on Mars.... I'm fairly confident that [the landing] will be a good night for us."
During the "seven minutes of terror," the descent vehicle is expected to slam into the Martian atmosphere at 13,000 miles an hour. Kept on course by small steering jets, the vehicle will release its single parachute after slowing to about 1,000 miles an hour. About a mile above the surface, the descent module then will release the chute, drop its heat shield, and the module's eight rocket motors will ignite, braking further to about 200 miles an hour.
The ultimate goal is to slow the descent to about 1.5 miles an hour, while descending straight down. About 70 feet above the surface, the module will begin lowering Curiosity until it dangles about 24 feet below the module. When the descending module senses that the rover is squarely on the surface, it will cut the cables and fly off to crash a safe distance away.
The fully automated landing system is designed to sense its track during descent and steer itself, an approach that's never been used before. This leads to a more precise landing, shrinking the size of the projected landing zone from 62 miles for past missions to 12 miles. That tighter landing zone makes a successful touchdown in Gale Crater possible.
Of the seven minutes, three are the most tension-filled, Steltzner noted during a briefing Thursday. The guided descent and the use of the sky crane are obvious nail-biters. The other involves a huge 70-foot-wide parachute, which must endure supersonic descent speeds.
Parachutes are "fundamentally sketchy kinds of devices," he says. Unlike, say, paratroopers, Curiosity has no back-up parachute due to design considerations.
While history is replete with failed Mars missions, with Curiosity, Lemmon says "you've got to look at the experience of the people doing it and say: You've got some reasonable confidence. If anyone can do it, the team that's running Curiosity can.”
How confident is he? "I have a lease on an apartment here in Pasadena for the next three months," he says. But, he adds, "there's an escape clause."