THE MARS SCIENCE LABORATORY (MSL) team is calling it the “six minutes of terror”—the time between entering the Red Planet’s atmosphere and landing on its surface.
The NASA probe, carrying the Curiosity rover, will be using a totally new landing technique called the “sky crane”, whereby the six-wheeled vehicle will be lowered by cable down to the surface from an altitude of about 20 metres…courtesy of a rocket powered descent stage.
This graphic shows us the different parts of MSL: the cruise stage (which looks after the whole ensemble on the way to Mars); the backshell (which protects the rover during the cruise to Mars and initial atmosphere entry); the parachute (contained within the backshell); the descent stage (which will handle the final part of the descent); the rover itself; and the heatshield.
Doing most of the work during the atmospheric entry will be the huge heatshield. At 14 metres wide, it is the largest heatshield ever sent to another planet, and about half a metre wider than that used by the Apollo spacecraft in the 1960s and 1970s. It will need to withstand temperatures up to 2,100 degrees Celsius. These couple of photos will give you an idea of the size:
Packed inside the backshell is the parachute, the largest ever sent to another planet. It’s also the largest “disc-cap-band” of any kind ever made. It is 16 metres wide and has 80 suspension lines that are 20 metres long. When deployed during the descent through Mars’ thin air, it will need to withstand a wind speed of Mach 2.2.
Here’s a photo of it, with some people standing nearby to give a sense of scale:
And here’s a video of it being tested at AEDC’s National Full-Scale Aerodynamics Complex 40-metre wind tunnel—the largest in the world—at NASA’s Ames Research Laboratory in California. The action starts about 53 seconds in:
Quite impressive isn’t it? The parachute will deploy just over four minutes after atmospheric entry, and about two-and-a-half minutes before landing. At this stage the craft will be travelling at about 1,450 kilometres per hour! Twenty-four seconds after the parachute unfurls, with the speed down to about 500 kilometres per hour, the heatshield will drop away.
Another 70 seconds (approximately) and the parachute and backshell will detach, and the descent stage rockets will fire up for the final, powered descent stage.
The following video animation takes us through the interplanetary cruise phase, and the whole entry, descent and landing. Let’s keep our fingers crossed that everyone works as planned on August 6 next year!
Story by Jonathan Nally. Images and videos courtesy NASA.
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