Despite Risk, Experts Bet on Mars Rover’s Novel Landing Plan

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NEW YORK — The seemingly implausible landing strategy NASA will employ Aug. 5 as it attempts to deliver the $2.5 billion Curiosity rover safely to the martian surface might seem overly risky, but engineers say the worry is overblown.

Curiosity, the Mini Cooper-size centerpiece of NASA’s Mars Science Laboratory (MSL) mission, is designed to be lowered onto the martian surface by a hovering Sky Crane holding it up via tethers. Despite the audacity of the concept, many aerospace engineers say the plan is solid.

“I agree it looks scary, it looks risky, but it’s technically sound,” said Georgia Institute of Technology professor Bobby Braun, who served as NASA chief technologist from 2010 to 2011. Braun was not part of the engineering team, based at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., that designed the Curiosity landing system. “In my view, it’s not risky; it’s actually the right way to land the system they’re trying to land.”

The Curiosity rover is designed to analyze samples of Mars rock for signs that the planet is, or ever was, habitable. Weighing in at 1 ton, Curiosity is too heavy to land with the assistance of cushioning airbags, like NASA’s two previous Mars rovers, Spirit and Opportunity.

Instead, parachutes will slow the MSL descent stage toward Mars before rocket engines fire to dampen its speed further. Finally, at about 35 meters above the surface, the Sky Crane system will lower Curiosity, wheels-down, toward the ground, attached to nylon tethers. The rover is designed to be gently settled on the surface, after which the Sky Crane will detach and fly off to land a distance away.

The plan requires a large number of sophisticated parts to work impeccably, and is utterly different than any previous mechanism used to land a machine on another planet, prompting some to charge that it is a scheme Rube Goldberg would have approved.

“A lot of people seem skeptical of it. I’m not,” said Stephen Gorevan, chairman of New York-based Honeybee Robotics, which built Curiosity’s internal Sample Manipulation System but was not involved with the landing strategy. “I just think the thing has been so tested. I see the electromechanical elements, I’m an engineer, I see at least each individual element of the scheme seems very reliable to me. It’s new, it’s daring, but I see it working.”

The Mars Science Laboratory team members themselves have admitted that the landing will be a nail-biter, as the fate of the rover’s entire two-year mission rides on the Sky Crane working correctly.

“Everyone will be biting their nails, but that’s not because they’re not confident,” Braun said. “I’ve worked on a couple of Mars projects myself, and I can honestly say that there is no team more deserving of success through the actions they’ve taken than the MSL team. They’ve put everything into this and they rightfully should be confident. At the same time, the reason we’re going to Mars is because it’s an unknown. Space exploration is hard, and landing on Mars is one of the hardest things we do in space exploration.”

Another aerospace engineer, Mars Society President Robert Zubrin, agreed the Sky Crane plan is technically sound, but said he wished that a more field-proven technology had been chosen for such an important mission.

“I can see the arguments why it should work,” Zubrin said. “I’m not one of these people who say, ‘Oh, this is ridiculous.’ However, it is its first time out. We’ve got an untried system being used on a mission in which the whole ball game is at stake.”

Zubrin said the success or failure of the Sky Crane, and hence of MSL itself, will likely determine the future of Mars exploration.

“What’s at stake here is the entire Mars program,” Zubrin said. “If this fails I think it will be very hard to push back at the [President Barack] Obama administration, as well as at the fiscal conservatives. People will say, ‘Look, we just gave you $2 billion and you failed.’ On the other hand, if it succeeds, I think the level of success is going to be very profound.”