You’ve probably already seen the trailer. It’s gotten 800,000 YouTube hits, it’s been shown on most major broadcast and cable news shows and its name — “Seven Minutes of Terror” — has become something of an Internet meme. But the producer of the video sensation it not one of the usual Hollywood suspects. It’s NASA — and if you think the five-minute web teaser the space agency has produced is cool, wait till you see the actual show, scheduled for Aug. 5.
That’s the day the Mars Curiosity rover — the $2.5 billion, six-wheeled lab that’s the latest brainchild of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena — is scheduled to touch down on the Red Planet. While the mission of the SUV-sized rover is ambitious — employing a new suite of instruments to go rambling about Mars sniffing out signs of past or even present life — other rovers have done similar things before. The landing, however, will be like nothing NASA has ever attempted. If the engineers can pull this one off, their efforts will be counted a success even before the rover can move so much as an inch across the soil.
There are basically two ways to land on another world: parachutes if the planet or moon has a thick enough atmosphere, and rocket engines if it doesn’t. Right away, Mars presents problems. It’s wrapped in just enough atmosphere to slow an entering spacecraft down and give a parachute something to bite, but not enough to permit a soft and survivable landing. The previous three rovers — Sojourner, Spirit and Opportunity — solved that problem with a combination of parachutes, descent rockets and, for the final plunge, a swaddling of air bags that allowed the vehicles to hit the surface and bounce across the landscape until they finally rolled to a stop and could shake off their padding. It was an ignominious way to arrive, but it got them there in one piece.
But Curiosity, at 5,293 lbs. (2,400 kg), is way too heavy for the airbag model, so JPL engineers had to dream up a new approach — and dream they did. When the blunt-bottomed, conical pod carrying Curiosity slams into the Martian atmosphere on its way to a touchdown in the planet’s Gale Crater, it will be traveling at a blistering 13,000 mph (21,000 k/h). The thin air will provide enough braking force to bleed off about 93% of the speed. When the ship is about 7 mi. (11 km) above the surface and traveling 900 mph (1,448 k/h), it will at last deploy its parachute — but not just any parachute. At 51 ft. (15.5 m) in diameter with 80 suspension lines, it’s the biggest chute ever used in an extraterrestrial landing. This will slow the spacecraft down to 190 mph (305 k/h).
(PHOTOS: NASA’s New Mars Rover ‘Curiosity’)
That, of course, is not a remotely safe landing speed. So after jettisoning the no-longer needed heat shield, the ship will fire retrorockets that will slow it a crawl that actually approaches a hover. At that point, the rover could just be set gently on the surface, right? Not quite. And here things take a decidedly Jetsonian twist.
Since the blasting retrorockets could stir up an instrument-damaging dust cloud as Curiosity closes in on the ground, the spacecraft will transform itself into — wait for it — a sky crane. As it reaches a 2 mph (3.2 k/h) descent speed, half of its eight engines will shut down and four nylon cords will spool out, lowering the rover the last 25 ft. (7.5 m) to the ground. Once the spacecraft senses touchdown, the descent stage will sever the cords and soar off in a flyaway maneuver. It will crash at least 500 ft. (152 m) away, sacrificing itself to make certain its rockets don’t damage the rover.
All together now: no way!
“It’s like a big long chain, and all of the links have to work in order for the thing to land properly,” says Tom Rivellini, the JPL engineer who provides much of the memorable, conversational narration for the “Seven Minutes” video. “One of my best friends said, ‘you guys are kind of playing up the drama a little bit,’ but to be honest we’re actually downplaying it. So much stuff has to go right in order for the thing to not crash and burn. I’ll take the coolness factor once it works properly.”
Working properly is by no means a sure thing. First of all, there are the numbers: Sixty percent of all Mars missions fail and “every landing is a first,” says Doug McQuiston, director of NASA’s Mars Exploration Program. Then there’s another big number: two — as in the paired, redundant hardware that NASA typically designs into its ships so that if a primary system fails, a back-up can fill the breach.
Two computers will control the avionics as Curiosity descends. There will also be dual explosives firing when the heat shield and other systems separate from the craft, even though only one pyrotechnic is needed for the job. But duplication is expensive in both dollars and weight, so that’s where the redundancies end.
“With no humans on board we have the luxury of taking a little risk, so we turn that risk into more science and it’s a great return on investment,” Rivellini says. “But it does come at a potential cost which is, you might lose the mission because we have these single-string, complicated vehicles and things just have to go right.”
Wild as the whole ideas sounds, the reality is that the landing system is actually just a next-generation version of its predecessors. Previous rovers used similar but more rudimentary radar to target the ground and simpler rockets that couldn’t be throttled. This time, JPL engineers upgraded the radar and borrowed a page from the 1970s Viking landers by adding thrust valves to the rocket motors on the descent stage. “Now we can control the velocity so well that we don’t have to make up the difference with airbags; we can just set the payload directly on the surface of Mars,” Rivellini says.
If the complicated landing sequence does play out as hoped, the work that follows could produce some amazement of its own. The science payload aboard Curiosity will be 10 times bigger than that carried by any previous rover. The most important of those instruments is the soil-sampling system that will look for signs of Martian biology. “We will have a big milestone when we put the first scooped sample into the analytical lab,” says Joy Crisp, the deputy project scientist. “That will reveal the minerals, and we’ve not been able to answer that before.” The rover’s other instruments will beam x-rays into powdered rock, sniff the atmosphere, and scan different wavelengths of light, all in hopes of finding water, carbon, methane, and other life-building elements. The results should inch researchers closer to definitive answers about whether the planet serves as a model for Earth’s own past — including its early biology. Says Crisp, “We’ll have a lot more clues to put the puzzle together.”
Oh, and while Hollywood may not have had a role in producing Curiosity’s celebrated web trailer the mission will still give us an action movie of sorts. An on-board camera will be recording full-color video of Curiosity’s landing, offering the first-ever view aboard a spacecraft landing on Mars. If all goes well, it seems “Seven Minutes of Terror” won’t be the last compelling video about Curiosity’s wild ride to Mars.
PHOTOS: Roving the Red Planet