back to article 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 …

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.

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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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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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Re: shock absorbers for landing

I dunno but it's not not unlikely. Nice ASCII btw.

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Re: shock absorbers for landing

Nah, that is nothing compared to landing a probe with 20 year old+ tech on a comet moving at 40,000mph 500 million miles away - I am just in awe how these guys do it. Just amazing.

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Re: shock absorbers for landing

I hope they worked, as whenever I drop something fragile on the kitchen floor I always find it breaks on the last bounce ..

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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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Re: shock absorbers for landing

That's what my general trajectory always looked like when I was playing Lander as well...

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Re: shock absorbers for landing

Nobel prize for the team...

...except for that schnozzbottle dork in *that* shirt

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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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Pint

Fingers crossed

...and a beer to wing it's way to them for an exciting Friday nights work

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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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Never give up

That's the message I get from this. Good attitude on the part of the boffins.

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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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Just like in earlier documentaries

This is where it always fails - drilling. Why didn't they ask Willis?

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It's all very well saying this after the fact, but with an unpredictable (at the time the mission was devised) surface, and the possibility of cliffs and craters, I bet the wish they included an independent power source (nuclear) now...

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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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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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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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"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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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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I hope they can retrieve and analyze a sample!

But I'm going to be disappointed if the results come back "The comet is really a dirty snowball" :)

Where is the "fingers crossed" icon?

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Re: I hope they can retrieve and analyze a sample!

I hope so too, but what's wrong with a dirty snowball, the amount of water in the comet is of great interest like the "dirt" too. Fingers crossed in my coat.

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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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Re: I hope they can retrieve and analyze a sample!

Harry Stamper, where are you when we need you!

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Can't someone just ask the SoupDragon for help?

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Solar panels

I don't suppose Rosetta has any shiny surfaces that could be used to reflect some sunlight onto Philae (when they find it)?

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Re: Solar panels

presumably the comet - and Philae - is rotating with reference to Rosetta? Would make aligning a reflected beam difficult

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video of what happened

https://www.youtube.com/watch?v=HArUmqqiL0s

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Don't give up. One more giant bounce for robotkind.

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When harpoons failed it was probably inevitable it would bounce til wedged

I suppose that if the lander had not gotten wedged in this location it would have bounced again a few times before either getting wedged some place else or running out of energy.

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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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Boffin

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.

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