shock absorbers for landing
Can someone suggest why a sort of shock absorbing system could not have been used to take the energy out of the actual landing. I was thinking some sort of gas releasing valve to absorb the impact energy.
Comet lander drill cliffhanger as last dregs of power used
The Philae team has opted to use what could be the last of the comet-catching lander’s power to deploy its drill, in the hopes of collecting the chemical analysis that could answer fundamental questions about life on Earth. Artist In a nail-biting cliffhanger end to the lander's story, the plucky probot’s protuberance had …
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Friday 14th November 2014 15:12 GMT Rabbit80
Re: shock absorbers for landing
There was a shock absorber system - but the gravity is so weak on the comet that even the slightest bounce would cause the probe to go skywards again.. That's why they had the harpoon system - to anchor it in place after the touchdown and prevent the bounce.
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Friday 14th November 2014 15:43 GMT Anonymous Coward
Re: shock absorbers for landing
I am wondering if it sort of done this:
..............................................................................
.........................................*..................._________<Cliff
*..............................*...............*........../
..*.....................*..............................* / <-second contact
.....*...............*....1k bounce........*.../ <- second bounce
........*......*.....................................*/
........._*____..............................*./<- third minor bounce
____/............\______/\__/\____*/
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Friday 14th November 2014 20:16 GMT Chris G
Re: shock absorbers for landing
" I always find it breaks on the last bounce"
That'll be WHY it was the last bounce!
After getting eighty per cent of the information they were after in spite of all the bad luck it is well worth going for one last bounce if they can do it.
Here's wishing them luck.
Is there a Nobel prize category for this? The whole team deserves it!
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Friday 14th November 2014 23:58 GMT Annihilator
Re: shock absorbers for landing
"Is there a Nobel prize category for this? The whole team deserves it!"
For Physics, maybe, but doubtful - they didn't come up with new physics to do it. Peace, perhaps, at a stretch.
The challenge is who gets it. It can't be shared across more than (I think) 3 individuals.
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Friday 14th November 2014 15:48 GMT 0laf
There was also some little cold gas thruster to try to keep it on the rock but it was known to have failed before it even detached. Then unfortunately the harpoons failed too. the gravity is so weak that it bounced about 1km up and it took a couple of hours to come back down again and in that time the comet turned about 1km under it.
Interesting that they are now in the almost 'F**k and try" stage where anything goes as long as there is power left. Plus there is an outside bet it could wake up in the future as it gets closer to the sun.
A shame it didn't work perfectly but an awesome bit of work none the less.
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Monday 17th November 2014 09:44 GMT Anonymous Custard
Re: Never give up
Have to agree, plus also the restraint from going all-out to fix things now, given that the comet is heading sun-ward and so the game (or at least the shadowing) and the amount of sunlight available will change as it goes.
So whilst it's in shade and drained now, in a while it may well end up in sunlight and charge again and so become available for more work and communications. Of course the risk here is that the comet and the lander both may not survive longer-term if that heating causes the comet itself to become more unstable and/or break-up, but I guess those are the rules of the game.
But what they've achieved so far has been amazing, anything else additionally is a wonderful bonus. Top boffinry all round.
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Saturday 15th November 2014 01:05 GMT DaddyHoggy
I'm pretty sure Europe agreed some time ago not to fire Plutonium* sourced Radioisotope thermoelectric generator into space - even for scientific reasons.
Given the Rosetta team managed to guide a space probe for ten years - using technology that was designed twenty years ago and actually get the thing there - you'd think these bright boys and girls might have considered these things - and given the lander doesn't have a RTG there are obviously reasons why it hasn't...
* Pu238 because it has a decent half-life, requires the least amount of shielding and yields the best power:weight ratio.
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Monday 17th November 2014 10:43 GMT John Jennings
you are right - on plutonium
ESA are not cleared to use PU 238 - plus, there are 2 problems with it for RTG (thermal nuclear batteries) - 1 the US does not sell nor produce it any more, and 2 the Russians stopped selling theirs in the 1980's....
PU238 is the most efficient (and low radiation) version, but ESA is exploring Americum 241 RTG's - Euro Nuclear reactors can make it, and though its only about 1/4 the thermal efficiency (by mass), and more radioactive, its common as muck (relatively speaking) (Smoke alarms use tiny amounts of it).
Americum 241 has a half life of 88 years, rather than 15 for plutonium.
Regards
F00
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Monday 17th November 2014 18:31 GMT cray74
Re: you are right - on plutonium
"Americum 241 has a half life of 88 years, rather than 15 for plutonium"
Americium-241 has a half-life of 432.6 years, versus 87.7 for Plutonium-238.
"1 the US does not sell nor produce it any more"
The US resumed production of Pu-238 in 2013 at the rate of 1.5kg per year.
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Monday 17th November 2014 18:40 GMT cray74
"and given the lander doesn't have a RTG there are obviously reasons why it hasn't..."
Heat and weight come to mind. An RTG in the same class as Philae's 32 watts of solar power is 15 to 25kg, like the SNAP-19A, and that's just for the RTG. I think the solar system on Philae totals a couple of kilograms, not counting the batteries. Philae has heat trouble with the Sun's ~132 watts of solar heating (or was it 300?) at 67P's current distance from the Sun. An RTG will add about 525 watts - not directly to Philae, of course, since the RTG will probably be sticking out the side - but it's a nearby radiant heat source that will need to be addressed with insulation and so forth.
There's also an issue of what might happen if Nuclear Philae has a landing mishap and ends up at an odd angle with its RTG touching the ice. The RTGs flown by NASA to date have had "cold side" radiator fins running at 210 to 300C. Very cold ice mixes get excitable when hot blades of graphite hack into them like a nuclear macuahuitl.
You might try to bury the RTG inside the Nuclear Philae to avoid that scenario, but then you need to supply mass for the thermal control that keeps the probe from being baked by its own nuclear heart.
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Friday 14th November 2014 16:36 GMT asphytxtc
I would personally go for the bounce up again option, they've come all this way on what seems like tidings of good luck. Okay, it didn't work 100% to plan - but did get 95% of the way there and that's something. Can you imagine the jubilation if a last ditch bounce landed them on a nice flat surface with plenty of sunlight?
And, with a suitably timed bounce, who's to say that the lander might not catch significant amounts of sunlight during the process? It could potentially go again and again until a good site WAS found.
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Friday 14th November 2014 18:33 GMT Doctor_Wibble
Re: I hope they can retrieve and analyze a sample!
On the other hand any comet stays as a dirty snowball without turning into a hot fudge sundae is a dodged bullet and therefore a Good Thing even if those are frequently not very memorable...
(bonus points for spotting *both* literary references)
TBH any probe that has most of its landing systems fail and yet still lands and and is capable of telling us it landed really does get a little gold star for the outstandingness of all involved. Next time it comes around we should put someone on that rock with a hammer to find out what went wrong.
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Saturday 15th November 2014 00:38 GMT Anonymous Coward
quite an achievement
As usual plenty of people on HYS saying it was a waste of money. Looking at the budgets of other space projects, I'd say this is a pretty good deal. Yes, we could have spent the money treating people in west Africa, but this was launched ten years ago, the commentards had plenty of time to instruct them to turn back, don the necessary PPEHYSPPEd treat Ebola patients.
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Saturday 15th November 2014 14:27 GMT phil dude
no sharks...
but couldn't they use lasers to light it up?
If you can stand the flash plugin they have a map here and it shows the probe is heading past the Earth...ok it is 5x108km away...
How big a laser would be needed? And would it work for solar panels?
It's cold here, and very cold there!!
P.
Biting the hand that feeds IT
