Excuse my ignorance...
...but won't a 21 foot tether be too short from 20 metres up?
It's T-40 days unti NASA's nuclear powered Curiosity rover arrives at Mars and commences re-entry and descent to the surface beneath its hover-rocket sky crane lander - and the space mission's engineers are biting their nails. It's not the first time the space agency has talked about "seven minutes of terror". Pretty much …
Of course the foot is no less rational than the metre. After all, it's trivial for anyone to convert feet into, oh, let's say, miles (after you guess which kind of mile we're talking about). So, how many miles in 457 feet?
On the other hand, converting say 457 metres into kilometres requires the wholly counterintuitive process of shifting the decimal point a three places to the left.
Er, no. Not when the thing then descends until the rover's wheels hit the dirt some 21-and-some feet below it isn't.
UoM is unimportant too. As long as tether length < distance to ground at deployment, everything's fine. No need for any exactitudality on this one.
 While I'm being unusually positive and friendly toward the yanks, I might as well go the extra mile and use the language.
Pity they cannot land near Spirit or Opportunity, so they could film the descent.,,
Yeah, that would be pretty cool, but even if they were able to precisely target the MSL landing to a point within sight of Opportunity's cameras, it'd probably still be a toss-up as to whether or not the Opportunity cameras would be able to catch it. There'd be all kinds of timing issues, I'm sure. Maybe -- maybe -- Opportunity might be able to catch MSL incoming if its entry/descent flight path carried it over the area where it's currently working.
Still, we do have that spectacular shot that the MRO camera got of the Phoenix lander's descent under its parachute -- as I recall, a wide, sweeping panorama of a large crater with Phoenix, still in its aeroshell, with its 'chute fully blossoming above it in the relatively near distance, backdropped by the floor of the crater. The foto was at a high enough resolution that when you zoomed in to 1:1, you could see the parachute lines extending down to the lander. Gorgeous. Still, if I remember, it was a case of MRO simply being in the right place at the right time.
...before the damned "martian curse" kicks in and we lose this vehicle, too?
As I recall -- at least lately -- the Martian Curse seems to have only affected Russian missions, and in many of those cases, it was due to sloppy programming or engineering. Some of the early US missions had that problem, too, but by the time of the Viking missions, JPL pretty much had it going on.
Oddly enough, though, now that you mention it, the Russians have had extraordinarily good luck with Venus missions.
NASA engineers mixing imperial and metric measures in one video. Miles, kilometres? Feet, metres? Hope they get it right this time.
I'm not keen on all these high speed manoeuvres. I'd prefer much more that retro rockets, parachutes, and air brakes were used in the upper atmosphere, and then they can deploy a large balloon, for a gentle descent to the surface. I really hope that it all works. For me space exploration is the only thing that excites me about technology these days. Here on earth the "bad monkey's" are still killing one another over trivial things, monkey hives (cities) are overcrowded, resources are running out, or so the greedy monkeys tell us. It is just a shame that all the greedy control freaky monkeys ensure that trillions are spent on means to kill other monkeys rather than really solve the problems of the day.
Perhaps this scenario is our only hope.
Fact check. sojourner and the long-lived rovers ALL used these cranes with teathers. The difference here is that there is no air-bag encapsulating the rover-module. It is not without risk, but it is an incremental improvement from the MELs...
Well, sure, but...it's so crazy, it just might work!
As it's often been pointed out here, the method being used for MSL is really no crazier than the idea of encasing your landers in bouncy balloons and just letting it fall in, bounce, and roll to a stop. As I recall, the airbag landing system used on Pathfinder and MER also contained thousands of parts that all had to work just right, controlled by millions of lines of code that all had to execute just right in a computer that had to work just right.
Same with Apollo, waaaaay back in the day; there were a mind-numbingly huge number of complex hardware and software systems that all had to work just right in order to get the crew to the moon and back.
Doesn't gravity take care of most of this? I mean I don't think it's a challenge getting from the top of the atmosphere to the surface, nor going from 13,000 mph to 0, although I grant you the last bit can be tricky if you want to use anything afterwards...
Whilst NASA may well be guilty of mixing their units, I'm not sure the difference between 21 feet and 20 metres actually matters. Depends on what they meant by lowering it slowly to the surface. If they want to hover at 20 metres and use the wire to lower it all the way to the surface, that's an issue if it's 21 feet long. However, if they want to lower the rover on it's 21 foot wire when at 20 metres and then gradually drop the lander to deposit the rover, that's fine. The lander will be at 21 feet when the rover touches down. Without knowing which one is their idea, it's difficult to say if their feet/metre issue will present a problem.
Whilst a very interesting way of delivering the package and certainly more entertaining than other more conventional methods, I'm not sure why they've chosen this method. We've got a lot more experience of dropping a lander on reto-rockets to touch down than trying to hover them. Then, the rover could run off the top. Not sure what the issue was with that, but dangling a rover under the lander seems unduly complex. Given the difficulties of carrying loads under helicopters on earth, this seems silly.
Alos hope there are no aliens around when the lander detaches the rover and fires off to its destruction. Not sure they would appreciate a lander hitting them.
I seriously urge NASA to use these last 40 days to re-check which part of the whole shebang is expecting its input in fractions of imperial units. Considering the thing was built and operated by engineers such as the one interviewed here, there's high probability of a non-metric bug stuck somewhere in the middle. Hopefully, it's not a 21 ft rope gently dropping the buggy from 20 m above surface...
Down at JPL in Pasadena (California, not Texas) and an auxiliary site a city or two away, LOADS of people are going to visit. All sorts of politicos and "distinguished visitors" of every stripe. Having a brother in law in charge of working the antennas (the deep space network, Hi Wayne!) didn't get me a seat at all, so I have to watch it on a computer as the Satellite service (DirecTV) doesn't have it on the default channel list (curse, curse).
The weird thing is that by the time the telemetry gets back to Earth, the whole thing will have done its deed (pass or fail). When we get word of it entering Mars (little) atmosphere, it will all be over. Hopefully the Mars orbiter will snap a pic like it did on the last lander. At 8:30 we'll get nice pictures and all will be well! I'll then go back to bed.
Having deposited the rover, I hope the descent vehicle is going to land and do something useful,
rather than crash land as stated.
Having got all that way, it would be a shame not to have it at least take photos (e.g. of rover site) or provide data relay and save power on rover.
It's not rocket science... oh, er...
The only potentially useful thing the descent vehicle will do after dropping the rover will be to make a nice bit dent in the ground as it crash lands.
To land the descent vehicle as well would probably require more fuel which in turn would mean less stuff on the rover so dumping instrumentation or somthing. The mass on these trips is very tightly constrained and they want as much as possible do be doing the most useful work it can.
It's a bit like the platforms spirit and co. rolled off, they didn't do anything afterwards.
<= Photo of descent vehicle at instant of touchdown.
Remember what they said in the 50's (and more recently by that good fellow Monty Burns), "Radiation gives you a healthy glow!"
So it'll be easy for us to find the Martians in about 20 to 30 years...
Let's hope the Martians are forgiving about the other bit (being as impotent as a Nevada Boxing Commisioner)
I volunteer to start the 'When will this over-complicated system fail and splat the whole mission?' sweepstake ...
"Deploy the rope!"
"... why is there no rope?"
"Malcolm, you are the 'safety unspool prevention pin' pre-launch remover. Now tell me again who was supposed to remove the 'safety unspool prevention pin'?"
I know they have been very quiet recently and have let Spirit, Opportunity et al. carry on BUT I'm not so sure what their response will be to "Thunderbird" type landings complete with Bungees!
BTW does anyone have any info about the system of measurements used by the Martian locals
...is it more or less accurate than NASA's systems?
I don't quite get it.. Previously they used large balloons to cover the whole unit and basically had it drop from the sky using parachutes. They did this twice and it worked.
Why all of a sudden change the whole setup for something which has hardly been tested ? It seems to me that this system is a lot more prone to errors than the previous one.
I don't quite get it.. Previously they used large balloons to cover the whole unit and basically had it drop from the sky using parachutes. They did this twice and it worked...
You may want to review the video and read up on the MSL mission. Basically, the MSL rover, being about the size of a Mini Cooper, is too heavy to land with an airbag system.
Does anyone know of any footage of this descent contraption being tested on Earth, if indeed it has been tested with a physical prototype dropped from an aircraft? I realise that Martian gravity is weaker and atmosphere thinner than at home, but adjusting the size of the chute and strength of the retros shouldnt be too much trouble for rocket scientists, and would presumably be a worthwhile piece of validation.
I think this is a case of the US governmental "good idea bus" making a stop at NASA. Too many moving pieces means too many things to go wrong. I'm sure the engineers have put some thought into this contraption... I have good thoughts that this fuckery will actually work.
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