AIR & SPACE MAGAZINE

NASA’s Curiosity rover will try a new way of landing on another planet

Dropping in on Mars.

January 1, 2012

If the giant, bouncing airbags that delivered NASA’s previous rovers (Sojourner, Spirit, and Opportunity) to the Martian surface initially made some people nervous, the Sky Crane maneuver designed for the new Curiosity Mars Science Laboratory looks every bit as scary—at first. The most advanced and expensive rover ever sent to Mars, the $2.5 billion Curiosity will be lowered from a hovering, thrusting descent stage, on a bridle of three nylon cords, to a soft touchdown on the surface. No landing platform required: This explorer will start off on its own wheels. It may seem treacherous, but the Sky Crane maneuver was inspired by Sikorsky CH-54B helicopters that routinely airdrop heavy cargo on Earth. The method has advantages over bouncing airbags, which couldn’t have handled Curiosity’s one-ton weight. The landing should be precise and gentle, and because the descent stage flies away after dropping off the rover, there’s no rocket exhaust to contaminate the arrival site, as happens with conventional landers. The journey to Mars takes nine months, but the final, stomach-churning landing sequence, scheduled for August 5, 2012, takes less than a minute. Stay tuned.

Landing Site: Gale Crater

Mars scientists have long eyed Gale Crater as a possible landing site for its variety of geological settings spanning two billion years. Curiosity’s precision aiming (within a 12- by 15-mile ellipse) allows a landing here for the first time, within reach of dried-up stream beds and a three-mile-high central peak.

Rover Sizes

About the size of a small car, Curiosity is five times heavier than the last Mars rovers and has a bigger experimental payload: 165 pounds versus 11. The new rover carries more and better science instruments, and is designed to last longer (687 days vs. 90) and travel farther (12 miles vs. 0.6).

Mission Tools

Powered by a nuclear battery, Curiosity will be able to analyze soil and rocks that earlier rovers could only inspect.

1. The rover’s head-like mast has color cameras for wide views and close-ups, and a ChemCam for determining chemical composition of the rocks from afar.

2. Weather sensors track wind, humidity, temperature, and pressure.

3. A mini-laboratory in the rover’s body heats soil until it vaporizes, so a laser spectrometer can identify any organic elements.

4. An arm-mounted “turret” includes a drill and a scooper that collects samples for the lab.

The Last Minute To Mars: Parachute Deploy

A supersonic parachute slows the spacecraft after its fiery entry through the atmosphere, and the heat shield is dropped.

The Last Minute To Mars: Backshell Separation

Using radar to sense its distance from the surface, the descent stage — with the rover tucked underneath — separates from its parachute and protective backshell. Altitude: 5,900 feet.

The Last Minute To Mars: Powered Descent

Immediately after backshell separation, eight engines fire to stabilize the descent stage and begin slowing its rate of fall from 100 feet per second to 2.4. Powered descent lasts 25 to 30 seconds.

The Last Minute To Mars: Sky Crane Maneuver

About 70 feet above the surface, still descending at a little over two feet per second, the rover is lowered on its bridle until the nylon cords unspool to their full 25-foot length.

The Last Minute To Mars: Touchdown

With the rover’s wheels locked in landing position, the descent stage keeps dropping until it senses (from automatic throttle-down commands sent to the engine) that the rover’s descent has stopped at touchdown.

The Last Minute To Mars: Flyaway

Once touchdown is confirmed by onboard computers, the nylon cords and a data umbilical are cut, and the descent stage flies away to crash at a safe distance on the Martian surface.