The airbag landing system isn’t an option for Curiosity. Weighing in at an impressive 1,654 pounds (that’s three-quarters of a ton), it is the size of an SUV.
Similarly, a larger parachute to slow Curiosity’s initial descent ... would be too heavy for the launch vehicle and unlikely to fully inflate before its payload reached the Martian surface.
The Jet Propulsion Laboratory was also keen to move away from the inevitability of driving a rover off a landing platform as it had with the previous rovers.
It was clear that for NASA to deliver the larger and heavier payload with less room for failures, it would need a new landing system. Enter the Sky Crane.
When this problem is first presented to people, the most offered solution, Manning says, is to use airbags, since they have been so successful for the missions that he has been involved with; the Pathfinder rover, Sojourner and the two Mars Exploration Rovers (MER), Spirit and Opportunity.
But engineers feel they have reached the capacity of airbags with MER. “It’s not just the mass or the volume of the airbags, or the size of the airbags themselves, but it’s the mass of the beast inside the airbags,” Manning said. “This is about as big as we can take that particular design.”
Did they have to use all the terrible action-movie-trailer cliches? [...] Show me some science, don't try to excite my reptile brain by making me think I'm watching 24.
You don't need to try to convince me of that! I'm in complete agreement. I'm just pointing out that I think the video in question is a representation of the decline of the level of public education and engagement. It's very disappointing that we expect so little of the citizenry that anything that doesn't conform to the Hollywood production values for "entertainment" we've come to expect over the past 15 or so years will be ineffective and pointless, and even moreso that we automatically suppose that links to four 2 page, easily understood papers will make a reader fall asleep.
I want to see a video of this thing hovering/maneuvering over a piece of the Nevada/California desert before I will start getting excited.
In its tilted state, the spacecraft does not fall like a rock. It actually generates lift. It will literally be flying in Mars' atmosphere, not falling. It can, in theory, even rise in elevation at some points during the deceleration phase (though it probably won't need to, given how low-elevation Gale Crater is). It will use an inertial measurement unit (which contains gyroscopes) to detect its path through the atmosphere, and will change its pitch (the angle of the cone) and also bank left or right as needed, making S-shaped curves, in order to deliver the spacecraft to a targeted spot at a targeted velocity for parachute deployment. This guided flight phase is what makes Curiosity's landing ellipse so much smaller than previous landers'. The atmosphere will still have an opportunity to move the rover around while it's under parachute, but Curiosity will be able to fly out almost all other sources of landing inaccuracy in this guided phase.
Another concern after the parachute inflates is something called "wrist mode oscillations." This is where the spacecraft spins underneath the parachute. Here's an interesting sentence from Ravi's article: "Historical attempts to bound the wrist mode behavior and its time evolution following parachute deployment have failed to bound the behavior during flight (e.g. MER-B)." Translation: we're trying to figure out ways to make our computer simulations produce the same behavior we observe in reality, but we're not there yet. Without an understanding of why this oscillation happens, it's really hard to engineer a system that prevents it.
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