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.
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.