Those 5 words
"NUCLEAR-POWERED ROBOT LASER TANK" - Did anyone else need to change their pants when they read this?
NASA's nuclear-powered robot laser tank, which the agency plans to land on Mars in 2012, will now be enhanced with a new automated lab experiment intended to discover evidence of life on the red planet. It's inventor seems confident that life - or anyway evidence of life in the past - is there to be found. "Mars was a lot …
They need controlled landings to put things on the ground where all the interesting stuff is. Boulders, craters and crevices do not make for good bounce-landing sites, but they're where a lot of the science is. That method looks obscene, but it allows for better placement and site selection, stops the rover being impeded by the landing gear or trapped on a landing platform and the rover's own suspension can handle any small surface irregularities.
"Could someone explain why, now having had a high number of successful landings on Mars NASA would now choose such a horribly complex completely new landing process?"
I'll take a crack. There are 2 issues. One is the concern of using rocket retro-rockets firing down to landing and igniting perchorates, which (it's hypothesised) burnt off any organic remnnats of life during the Viking missions. It's also a *lot* bigger than the 2 previous rovers which would have need much bigger crash bags. IIRC this is roughly 10kg versus 1500Kg.
The combination of these constraints gave rise to this "Skyhook" landing mode. It is complex (not to mention needing the top section to fly off and crash safetly out of the way) but should work. Note parachutes are a non starter given the mass (Viking handed it with landing rockets. But that's the point. you can't use them).
There are quite tight limits on how much mass the existing Entry Descent and Landing (EDL) can handle. Additionally, they're very inaccurate, and limited to areas of high (for mars) atmospheric pressure, which translates to low altitudes. The new, excitingly complex mechanism allows for a heavier payload, at higher altitude, and should also allow a high precision landing.
Landing precision is important for a rover that is used to look at rock outcroppings, as it's possible to land near them safely rather than either avoiding them completely and having a long drive to a site of interest by targeting a smooth landing area, or risking disaster by landing with poor accuracy amongst them.
Does anyone else feel it's wrong to be sending a vehicle to another world powered by hazardous material (which will still be so for many many years after the vehicle has ceased to be useful), which includes plans to kill alien lifeforms, even if they are only microscopic ones??!
Or is it just 'cos I watched The Day The Earth Stood Still (the Michael Rennie original natch) on DVD yesterday instead of getting to work through the snow..? ;-)
I thought the graphic of the landing was good, like the way they've jazzed it up with contemporary shaky cam effects (a bit like Firefly). What I did find interesting though was the whole deployment, probe detachment, thrusters, parachute *and* extension lines for a soft a landing as possible straight onto the wheels - wow. I can no doubt think of a few ways that goes wrong, high winds, landing on the edge of a crater etc. How much AI is in the landing module?
Because I'm a tiny microscopic bacteria and I don't have any bloody arms, that's why! And even if I did I wouldn't help the bastard, it wants to fry my family!
I dunno, bloody foreign killer laser nuclear-powered death robots, coming over here, taking our sand and cooking our women....(cont. p.94)
@Neil Stansbury
"Could someone explain why, now having had a high number of successful landings on Mars NASA would now choose such a horribly complex completely new landing process?"
I'll have a go.
("EDL" = "entry, descent, landing", aka The Six Minutes of Terror.)
The problem is mass. MSL is a huge beast, the general size comparison for the USians is "VW Beetle-sized". This is significantly bigger than the Phoenix lander (2008, EDL consisted of with aerobraking with a heatshield, then hypersonic parachutes, then drop out the bottom of the backshell and fly down to the surface on small thrusters) and the wildly over-successful MERs, Spirit and Opportunity (EDL: aerobraking, hypersonic parachutes, rapel down a line, inflate airbags, fire last-minute hack sideways-motion-damping rocket half-way up the stack, cut tether, bounce to a standstill, deflate airbags, self-right, open up.) MER was pushing the envelope on the mass that airbags can cope with; MSL would shred 'em in seconds, with unfortunate consequences (lithobraking.) There's also the problem that because the Martian atmosphere is so thin, you really need to land at as low an elevation as possible, so that your chute gets the chance to slow you down to the sort of speeds where you can fire up forward-facing thrusters: these tend not to like starting up with pointing into hypersonic airflows.
http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Landing_system
What I don't know, off-hand, is why they need the tether/bridle/winch mechanism, rather than flying the whole stack down to the surface, releasing the rover on contact, and then flying off to make an interesting hole in the nearby scenery. Of course, that doesn't mean there isn't a very good one, just that I don't know / have forgotten it :>
I'm guessing that the bridle/winch arrangement obviates the need for a soft landing capability and a completely flat and level surface to land on, as hovering-within-limits somewhere around the right altitude above something vaguely flattish should be entirely adequate here. Remember, there's no nice Mr Armstrong at the controls to go: "That looks a bit lumpy you stupid computer, let's go over there".
Having said that, I'd have thought that relying on all the bridle cables detaching themselves from the lab as one at the right moment is rather high risk. If one of those release clips fails they can kiss the mission goodbye as far as I can see. I'll bet the carrier doesn't have enough fuel to sit up there hovering while the lab asks control on earth for instructions....
Since Mars's atmosphere is 96% CO2 and atmospheric pressure is about 150 times lower than Earth's, I'm pretty sure all those (seemingly hundreds of) actuator motors can not be heard as in the video...
Instead of those stupid sci-fi like sounds, NASA (as a scientific rather than sci-fi org) should add a narrative to explain the complicated procedures seen on video...
Plus judging by the partially shielded cylinder with cooling fins on the front part of the "tank", the "nuclear" seems to be a standard RTG, but "nuclear powered" sure sounds more sensational than "radioisotope thermoelectric generator powered".