Last night, the United States (and all of humanity) landed a rover known as Curiosity on the planet Mars. We’ve managed to place a rover on Mars three times before, but never in such incredible fashion. The maneuvers performed on this mission read like the stuff of fantasy, or the plot of an episode of MacGyver. If you missed it last week, NASA’s Jet Propulsion Laboratory put together a fantastic video called Seven Minutes of Terror showing exactly how Curiosity’s entry, descent, and landing (EDL) worked.1
Watching that video is well, well worth five minutes, but here’s a summary of the steps it took to get Curiosity from above Mars down to its surface.
Eight months after being launched from Earth, Curiosity entered Mars’ atmosphere. Its heat shield withstood temperatures of as much as 2000 degrees Celsius while slowing from 13,000 miles per hour.
As the craft was slowed by the atmosphere, it was also self-guiding towards a very specific landing spot, constantly adjusting course to get close.
When Curiosity got down to 1000 mph, a supersonic parachute was deployed to continue slowing the descent.
After the parachute was deployed, the heat shield needed to be fired away so that the radar system could scan the ground for its landing.
With its parachute only capable of slowing the craft to about 200 mph, Curiosity needed to cut it off for the next stage. Rockets, thrusting away from Mars, were then used to slow the descent further and divert away from the parachute.
The rockets next lowered the rover towards the surface. However, due to the dust this descent stage could kick up, the rocket engines could not get too close to the surface itself. How do you put a rover on the ground if you can’t set down on it?
Why not use a sky crane? Yes, while the descent stage was hovering above Mars, it lowered Curiosity down on a tether.
Finally, once the rover was on the ground, the descent stage cut itself from Curiosity and flew away for a planned crash landing safely away from Curiosity.2
So that’s how you land a one-ton, car-sized, nuclear-powered rover on a planet 150 million miles away. And oh, one other thing? Because of the 28 minute round-trip for radio signals between Mars and Earth, this all had to be done automatically, with no human intervention whatsoever. We could only sit back and wait to hear word of our success or the deafening silence which would indicate failure. Guided entry, parachute descent, powered descent, and an honest-to-goodness hovering sky crane, all pre-programmed to be able to handle anything an inhospitable foreign planet could throw at us. And we pulled it off.
Some might question why we should explore space, particularly when we are beset by so many terrestrial problems. Dr. Ernst Stuhlinger provides a wonderful response with a letter penned 42 years ago. The simple answer is that research and discovery are two of the greatest tools we have to solve problems, whether those problems are hundreds of millions of miles away or right here on Earth. It’s impossible to know what benefits we’ll reap from this incredible mission, but history tells us they will be great and they will be plentiful.
Many pictures will be received from Mars in the coming days, weeks, and months. They’ll come in color, from higher-quality cameras yet to be deployed. However, I think this prosaic shot of Curiosity’s shadow, one of the very first images it sent back, has a beauty all its own.
Look at what we can do.
While it’s silly to anthropomorphize machinery, this still strikes me as a sad but noble death. ↩