Comet Probe Philae Unanchored But Stable — And Sending Back Images 132
An anonymous reader writes with an update to the successful landing of the ESA's comet probe Philae, which (as mentioned yesterday) had problems attaching to the surface of the comet's Rosetta: "BBC now reports that Philae is stable on the surface. Although no source claims so, we can all imagine a faint humming of 'Still Alive' coming from the probe." Not just stable, but sending pictures while it can. From the article: The probe left Rosetta with 60-plus hours of battery life, and will need at some point to charge up with its solar panels. But early reports indicate that in its present position, the robot is receiving only one-and-a-half hours of sunlight during every 12-hour rotation of the comet. This will not be enough to sustain operations. As a consequence, controllers here are discussing using one of Philae's deployable instruments to try to launch the probe upwards and away to a better location. But this would be a last-resort option.
New submitter Thanshin notes that the persistent Philae bounced a few times, and actually performed 3 landings, at 15:33, 17:26 & 17:33 UTC.Thanshin adds links to a handful of relevant Twitter feeds, if you want to follow in something close to real time: Philae2014; esa_rosetta; and Philae_MUPUS (MUlti PUrpose Sensor
One).
Sideways (Score:5, Informative)
Now Philae seems to be sideways and under the shadow of a cliff that only let's it have sunlight 1,5h per 12h cycle.
That amount of sunlight may not be sufficient to keep Philae operating beyond its 60h battery autonomy.
Most info seems to appear first in BBC news [bbc.com]
Couldn't they have used an RTG? (Score:2)
Why did we get away from that technology for space exploration? If you're going to spend the money to conduct a mission of this sort why limit yourself to the power provided by solar panels? It would be a pisser to have come this far only to have the mission fail because the probe can't get enough power to carry on operations.
Re:Couldn't they have used an RTG? (Score:5, Informative)
They are still used but it's in short supply because you need to create it in special reactors. And funding is a problem.
http://en.wikipedia.org/wiki/P... [wikipedia.org]
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France operates a number of breeder reactors that could be repurposed possibly. Since the Regan administration (in fact, Regan himself) we've lost the capability to manufacture Plutonium in abundance. Not that there's a lot of use for the stuff but the supply is running low as is it's half life.
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Julianne, the singer? Or perhaps rugby player Mark?
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Two reasons: fear that an accident might release plutonium dust into the atmosphere, and the relative shortage of plutonium.
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Come to think of it, quite a lot of systems have failed on this probe. The landing was a success but the mission doesn't look to be too successful.
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I don't believe Philae has thrusters, much less thrusters that can be fired gently. I get the impression that there is one single-use thruster that was meant to counter the reaction of firing the harpoons, and neither went off as planned. I would guess that at some point they will attempt to manually fire both. But if something goes wrong with that attempt it's very possible that Philae will get launched off of the comet, so they probably want to get as much science done as possible before they even try
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The weight figure I have heard is: equivalent to one sheet of paper on Earth.
Re:Couldn't they have used an RTG? China syndrome (Score:3)
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You are lucky to get 10% efficiency from an RTG with a thermoelectric element, and proper Stirling engines or steam turbines are not popular in space for some reason.
However, Philae only needs 32W apparently.
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You are lucky to get 10% efficiency from an RTG with a thermoelectric element, and proper Stirling engines or steam turbines are not popular in space for some reason.
I presume that reason is water weight, in the case of steam turbines, and the lack of free atmosphere to work with in the case of stirling engines. If you could somehow get the water there, though, a recirculating steam system seems perfectly cromulent. Certainly the system efficiency is dramatically better than an RTG, and it doesn't require any especially exotic materials.
If you had unlimited mass to work with (ha!) and you were using water for reaction mass anyway, it might actually make sense. Not here
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I presume that reason is water weight, in the case of steam turbines, and the lack of free atmosphere to work with in the case of stirling engines.
A Stirling engine doesn't require an atmosphere - all the gases are sealed inside and they are "external combustion" engines - just apply a heat source to one side, allow the other side to radiate heat, and away you go.
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Actually there is such a thing as an internal combustion Stirling engine. The British military deployed a portable generator set during WW2 that used one, and the google will disclose a few more. Obviously not much good in space, of course.
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... We could have built a pretty big station out of the space shuttle main tanks, for example.
We sort of did, actually, back before the space shuttle. See "SpaceLab", I think it was. But it's hard to get them high enough, and it fell back years ago.
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R&D on a nuclear-powered stirling engine for space [wikipedia.org] is ongoing [wired.com]. It's not they they aren't popular, per se, its just that they are a very difficult engineering problem. How many devices with continuously moving parts do you know that operate maintenance-free for years or decades? It's not impossible, but is really hard.
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That's the big problem. Mechanical devices wear down, and even without maintenance, going for years is difficult. Think of things like your hard drive bearings, or fans that work for years without maintenance, but having them work for a decade is a more iffy proposition reliably.
Plus, there's also
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proper Stirling engines or steam turbines are not popular in space for some reason.
Stirling engines are used in space, but only when there is a compelling reason to do so. The basic argument against them is two words: moving parts.
Mechanical wear is a huge problem, and thermal management is not a small one. Depending on the spacecraft a sustainable thermal regime may have to be maintained across very different environmental conditions (full sunlight, deep shadow) and very different operational phases. Just getting lubrication to work properly under such circumstances, over a decade in the
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I was being facetious, I thought that both ideas were so ridiculous that it would be obvious to everyone why no one does that.
Obviously I was wrong about Stirling engines. Perhaps I will end up wrong about steam turbines too one day.
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Rosetta/Philae came back to Earth several times for gravity boosts. It would not take much to make those flybys into direct hits, probably turning the RTG into radioactive dust.
Agencies who are dependent on public funding are generally wary about spreading radioactive dust.
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Several probes with RTGs have made close Earth passes. As I recall, Cassini happened to pass low over Iran for its final boost outward.
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Indeed. There was protests about that, and that was just a single pass IIRC. It is just not worth the bother unless it is the only way to accomplish the mission.
Re:Couldn't they have used an RTG? (Score:5, Funny)
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Re:Couldn't they have used an RTG? (Score:4, Insightful)
Who said the mission would be a failure? They've landed on a comet and received lots of data from the lander already. Even if the mission is cut severely short, it sounds like a success to me.
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The present RTG designs for spacecraft are all 1-2 orders of magnitude larger than what Philae would need.
One other thing I would note is that RTGs have useful lifespans measured in years to decades. Philae hasn't been designed to operate for that long (its long sleep until it arri
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Why? Because solar panels will do the job, where the job needs to be done. Simple as that. All the interesting stuff is going to happen when the comet is near perihelion, which for 67P is 1.2 AU. There's plenty of solar power there.
At 67P's aphelion of 5.7 AU an RTG would be needed -- if there were any observations worth spending money on. But powering this spacecraft with an RTG would be sending an expensive and heavy piece of equipment out into the middle of nowhere for no good reason. It'd be differe
Re: Couldn't they have used an RTG? (Score:2)
A name for the next one (Score:2)
"Unanchored But Stable — And Sending Back Images"? Let's call the next comet probe "Kim Kardashian". Then again, Philae is stable.
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But at that point, we risk pulling the comet out of its orbit due to Kim Kardashian's massive ass.
Good one, made me chuckle. Kindda reminds me of Gravitina [wikia.com] from the old Buzz Lightyear cartoon. Except she was massive on the other end.
So... (Score:2)
ESA has three successful landings on a comet now to brag about.
Using the same lander, on the same comet. Cheaters.
Warranty voided (Score:2, Funny)
"The lander weighs about 220 pounds and is the size of a domestic washing machine"
I'm waiting for the Saturday Night Live skit..
Due to a terrible mix-up. a Maytag washing machine was inadvertantly placed in the cargo hold of the Rosetta spacecraft.
"My socks have been missing for 10 years!" said Matt Taylor. He also added that now he knows why the washing mashine in Mission control does such a horrible job on the rinse cycle and has stymied the Maytag repairmen/women for the last 10 years.
"In hindsight we s
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The lander weighs only about one *gram* on the comet's surface.
The Philae mission is a partial success (Score:4, Interesting)
At the moment, the Philae mission is a partial, or qualified, success. They'll be receiving the passive science data and imagery, but let's be realistic: they have no way of anchoring Philae to the comet, they can't drill, and any attempts at "bouncing" it are at the mercy of how much gyro range is available to keep it stable while it follows the ballistic arc - and whether it'll come down anywhere safe enough to keep itself upright. The gravity is so small that the lander could "impact" the comet upside down and it wouldn't damage it, it'd just make its orientation useless for the deployment of drilling instruments. Heck, it may be that the gyros have enough oomph to roll the Philae if it ends up upside-down, although it'd probably tumble for a while before setting in some other random orientation, possibly still a wrong one.
They have to weigh the battery life against science returns - and right now there's no battery recharging to speak of. That's the hard part of rocket science - it's not through any fault of mission design, it's simply a bad luck. So, I bet they'll keep Philae where it is up to say 48-50hr mark, and then they'll re-enable the gyros and attempt a bounce, and they'll get one shot at it due to the time the bounce will take, and the link availability constraints due to Rosetta's orbit. I really wonder if the harpoons didn't work due to insufficient contact forces and a sequencer step to shoot the harpoon not being triggered, or if it's due to a failure of the harpoon deployment mechanism itself. It wouldn't hurt to reattempt a harpoon firing once the bounce ends with a recontact.
I'm still wondering why they couldn't get the Rosetta spacecraft itself to be the lander. It's a much bigger platform, it has a proper RCS system and could easily land and take off to scout multiple locations on the comet. Not having a stand-alone lander would give enough available weight to put the instruments on Rosetta itself, and take the extra fuel to do repeated landings and take-offs. That's at least according to my back-of-the-envelope fuel budgeting, I may be way off, though...
Overall, the biggest lessons learned are about things didn't work. Any further low-gravity comet lander designs will need to use designs that include fixes for whatever didn't work this time. I really wish they did, for example, store a duplicate thruster fuel supply system on Earth, in cryogenic conditions, for the decade Rosetta was out there - I bet it'd fail on Earth just as it failed out there, and it'd be an easy thing to post-mortem. But that time has passed, so we may never know what went caused the failure of the puncture pin system...
Re:The Philae mission is a partial success (Score:5, Insightful)
The problem is: we are talking about a design area of 1995 to 2002, with flight in 2004.
So, what we can do now, is all based on what we have learned.
All your ideas are valid and we will be better at it in the future.
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Bigger means more vulnerable to rough terrain, and we really knew nothing about the terrain on the comet when the probe was launched. (And actually, we only have a sample size of one, now.) Making the whole spacecraft a lander also puts the entire mission at risk in the event of a landin
K.I.S.S. [Re:The Philae mission is a partial succe (Score:2)
A lot of problems do seem to be caused by trying to do to much in unknown environments. A Russian Mars lander in the early 70's even had a little rover. This was before anybody knew what the surface of Mars was even like: rocky? sandy? dusty? If they focused instead on making it simple and robust, they could have had the first successful landing.
Same with UK's Beagle lander. If they had made it simpler and smaller, they'd have enough money left ov
Black and White? (Score:3, Interesting)
I have a question... Does anyone know why are the photos in black and white? Is that for higher resolution, because of low/high light situations?
Ok nvm, found my answer here: Why are images from space probes always in black and white? [straightdope.com]
Still think they should take photos with RGB filters too so we can see what it would actually look like, you know, for PR photos...
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There's nothing colorful on a comet. It's just shades of gray. Seriously. It's literally dirty ice.
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I realize that, but then what colour is the ice? What colour is the dirt? This isn't for science, it is for general interest.
I realize that using the filters they have they can create enhanced colour images, and I think that might be exactly what they should do...
Do you really know it is grey? Ice can have some pretty amazing light distortion properties(go visit Alaska)... And not all rocks are grey.
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No doubt they will, if they have time and power. But they're sharply limited on both, and I doubt the color images actually have all that much more PR value. (Not that PR has ever been shown to translate into actual public support mind you.)
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ted turner hasn't colorized them yet...
Amazing. Just plain amazing. (Score:4, Interesting)
This [flickr.com] is so cool [flickr.com]. ... Isn't that freakin' amazing? ... I'm getting goosebumps all over and feel like back in the 70ies when we'd been to the moon. (my Grandpa worked at Grumman as a Engineer on the Lunar Lander btw.)
We've landed on a friggin' Comet! This is so awesome!
F*ck yeah! YAY! Go, space exploration, go!
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I'm feeling the same way. You know that scene in The Lego Movie where Benny finally gets to build a spaceship and he builds/flies it while shouting "SPACESHIP!!!" as loud as he can? I feel like doing that only shouting "ROBOT ON A COMET! ROBOT ON A COMET! ROBOT ON A COMET!!!!!"
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think of all the new math we will learn (Score:2)
While it's not Math, we will add more knowledge to the simulations, we will learn a lot of the bounces, which should teach something about gravity bouncing on asteroids. We just might discover that the "dust" was really frozen solid, we might learn how to glide better.
They did something that was very improbable (speed matching at amazing speeds) which now makes it possible. I can not wait for the future
On the bounce (Score:1)
sending pictures while it can (Score:3)
Send Mark Watney (Score:1)
Cool landscape (Score:1)
This is an amazing shot in my opinion, like something out of an early 1960's sci fi show:
https://www.flickr.com/photos/... [flickr.com]
With some image processing it can probably get even clearer. We are seeing the rawer early versions.
The spewing "jet" ones are also interesting, but do look similar to past Enceladus images. The difference in this case is that they are probably only a few miles away from the probe instead of a few thousand.
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Someone needs to photoshop in one of those cheesy man-in-suit sci-fi aliens. ;-)
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Vectors are hard, even for rocket scientists... (Score:2)
First bounce was 1000m up (from the surface) - that's a helluva hop.
Then again, that was pretty much my result every time I tried to play Lunar Lander too.
Super Mario Galaxy! (Score:2)
Those pictures are amazing! I immediately was taken back to playing Super Mario Galaxy and imagined Mario running around the comet.
-Chris
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And on Fox they were denying it happened because one can't see any stars in the picture.
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That's just the SJ Sathanis in the background
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Ha, you can't fool me, they collapsed the jump gate to the Sol system, and the Shivans can't come here.
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If the History Channel has taught me anything in the past couple of years, whatever the puzzle is, it was Aliens.
Ten years ago, History Channel taught me it was all about Hitler
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"we land things on the earth every day and it's travelling thousands of miles an hour too"
Earth has gravity, and most of the stuff we land on it start from earth (so share the same velocity to begin with)
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I don't think we're the ones that need telling, Captain Obvious.
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Believe it or not, the fundamental premise of relativity(not to mislead here: it was understood as part of conventional physics far before that), that all motion is relative to a frame of reference is not well understood by the public at large.
Even people who graduated high school, and took basic physics classes might not have been directly exposed to the notion or internalized it. To a lot of people speed is an inherent characteristic of objects. Either you're going fast or you're not.
And scientists freq
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No kidding!
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No kidding!
Yeah no shit man. I was typing too fast and an error is always excusable.
It would be far more excusable if Slashdot did not give you a preview of your comment before you commit it. Type as fast as you want, but read what you wrote slower. You'll find your error rate reduced.
Re:Big deal... (Score:5, Insightful)
Why does every science-illiterate newsreader think that the most amazing part of the mission is that "the comet is moving at thousands of miles an hour?" This was amazing months ago, when Rosetta moved into its station-keeping formation with the comet. Right now, it is stationary with respect to Gerasimenko. What's incredible now is the deployment of Philae and its fight for survival in a totally unknown environment.
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I'm amazed there is apparently enough gravity from a 2kmx4km(right?) rock to hold the two objects together.
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Anchors, harpoons, flywheels and thrusters are used to keep the Philae in place.
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The great thing about age and money is that we don't have to give a crap about how you cave nutters feel. What really galls you is that some of the more successful space nutters have billions to play around with, and are making their dreams happen.
Meanwhile, feel free to pick another lump of charcoal out of your campfire and draw another buffalo on the wall.
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I think that it is a fabulous achievement. And even if it will not be possible to drill: look at those awesome pictures. Wonderful.
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If this were an American probe, would the commentor also have dismissed this landing as easily?
On MSNBC, yes. It would have also been declared waste of money that should have gone toward wage-inequality.
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Actually, for several demographics, viewing times and shows, they're doing better than CNN. [zap2it.com]
However, the Fox News numbers are absolutely obscene. *shudder*
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That may be true, but I would argue that is entirely CNN's fault for making themselves into such a joke of a network the last several years, rather than a success of MSNBC.
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Okay. So, you started by insinuating that MSNBC is a joke, and now you claim that CNN is a joke?
Actually, I think you have it backwards. Fox News is the joke. [forwardprogressives.com] They discovered long ago that the truth doesn't sell ads.
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When the Sun was newly formed, there was a cloud of dust surrounding it. As time passed, the dust particles collided and (thanks to gravity) stuck together, forming bodies of various sizes. Some collided together to form planets. Some were likely thrown out of the solar system (or into the Sun) thanks to gravitational interactions. Some cleared their orbits and became planets. Comets and asteroids are smaller compositions from this era that survived without becoming a planet, moon, or being tossed out.