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Space Station Solar Equipment Showing Damage

Posted by CmdrTaco on Mon Oct 29, 2007 07:54 AM
from the don't-touch-me-there dept.
NASA Space
bhmit1 writes "The latest space walk has turned up some bad news for the problematic solar panels: metal shavings. From the article: "The rotary joint, 10 feet in diameter, has experienced intermittent vibrations and power spikes for nearly two months. Space station managers were hoping a thermal cover or bolt might be hanging up the mechanism. That would have been relatively easy to fix, so they were disheartened when Daniel Tani radioed down that metal shavings were everywhere. 'It's quite clear that it's metal-to-metal grating or something, and it's widespread,' Tani said.""
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Submission: Space station solar equipment showing damage by bhmit1 (2270)
[+] More Solar Panel Problems For ISS 118 comments
rufey writes "This week there have been two pieces of bad news from the International Space Station. First was the discovery of metal shavings inside a problematic rotary joint used to keep one set of solar panels in the optimal position for power generation. At the close of a subsequent spacewalk, after it was relocated to its permanent location, the unfurling of the 4B solar panel resulted in it tearing in two places. A spacewalk is now planned for November 4th to attempt to fix the tear. The upcoming spacewalk is not without risks, including the remote possibility of electrocution since it is impossible to stop the solar panel from generating electricity during the repair attempt. NASA says the ripped wing needs to be fixed or the solar rotary joint problem solved before any more shuttles can fly to the space station and continue construction. With a hard deadline of 2010 for Shuttle retirement, NASA does not have much wiggle room in the schedule in order to finish ISS construction."
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  • that's not metal-on-metal grating (Score:5, Funny)

    by jollyreaper (513215) on Monday October 29 2007, @08:02AM (#21155965)
    That's not metal-on-metal grating in the bearings, that's just some sick bastard playing Yoko Ono.
  • It's one thing to get the metal on metal thing going in your car and then be stranded alongside the road. But at least your life would be in no danger. It's quite another to get the metal on metal thing going and getting stranded in space. Tow trucks for space stations cost a considerable amount more. And the mechanics... don't get me started on the mechanic's wages.

    • Re:Towing in space (Score:5, Interesting)

      by Migraineman (632203) on Monday October 29 2007, @08:23AM (#21156107)
      Towing in space has been done before. Grumman sent North American Rockwell an invoice for towing [geocities.com] their crippled spacecraft home. The rate per mile seems pretty reasonable too.

      All joking aside, this is going to be a bear to fix. The best scenario would be that the drive gear was munching an insulation blanket. The debris would be friendly to space suits, and should only be labor intensive to clean out. If the gears are grinding on each other, the debris will be sharp and hard. That would be "bad" and I'd expect NASA to seriously consider returning the entire assembly to earth for repair. Expensive, but much less likely to kill someone.

      I'm of the opinion that the drive system on this beast is probably over-engineered. It should resemble a Ford F-150 differential - loose tolerances, and designed to run for many millions of rotations without much maintenance. There's absolutely no need for the solar array to have precision pointing capability. I really do hope that the problem isn't due to over-engineering, but I wouldn't place a bet.

      • Re:Towing in space (Score:5, Informative)

        by Rei (128717) on Monday October 29 2007, @10:55AM (#21157705) Homepage
        These *were* designed to run for many rotations. The design specs for the SARJ (Solar Alpha Rotary Joint) were that the 10.5'x2.5', 2,500lb structure would rotate at 4 degrees per minute without imparting vibration to the laboratories that would mess up the microgravity experiments, for a minimum of 15 years. They also have to transfer 60kW of power at 160V while rotating through a "roll ring". These were the design specs, and they were engineered around that; this break was not supposed to happen. That's why this is considered an anomalous event. It's not a case of an insufficient design goal.

        One thing that a lot of people don't realize is that there's still a tremendous amount of stuff that we don't know about living and operating things in space. It's deceptively similar to our world; just picturing it being like an Earth where you can't breathe and you can have enough velocity to fall in a circle simply doesn't cut it.

        Example: TSS-1R. Space Shuttle Columbia deployed this as part of NASA's series of experiments with orbital tethers (for "hanging" craft from other craft and for raising and lowering orbits). When the tether was 19.7km out of the desired 20.7km deployed, it snapped. Evidence suggested arcing and burning in the tether. Why? The tether was at -3500VDC compared to the orbiter, with no current flowing through it. A minor defect in the tether's insulation left the conductive core exposed to space. Unexpected trapped gas in the insulation bubbled out in the vaccuum of space. This gas created a path for conduction to the orbiter, creating a plasma arc that burned away at the tether until the remaining strands failed under the strain.

        In hindsight, it's easy to look at this and say, "Oh, we should have had a short-detection system." However, hindsight is 20-20. We've learned a great deal from past experiences, which unfortunately means that systems have to get more complicated. For example: where does the heat from running the drive motor for the arrays go? Why, it goes all over the place! It took an entire design study [harvard.edu] just to figure out where it would be going and what to do with it. Now picture unexpected current draws (creating more heat) from the metal shavings thrown into the mix, and what that will do for heat load, or what the metal shavings themselves could get into or allow to conduct unexpectedly. Things get tricky fast.

        Too many people seem too eager to see a "finished product" in space. It's important that things like the ISS be seen foremost as learning experiences. In this case, I'm sure we'll see the same thing.
    • seen on a sign in a mechanic's garage:

      Labor $10.00 Hr.
      If you watch $15.00 Hr.
      If you help $25.00 Hr
    • It's one thing to get the metal on metal thing going in your car and then be stranded alongside the road. But at least your life would be in no danger.

      Actually your life could well be in danger, from idiots crashing into your broken down car...

      It's quite another to get the metal on metal thing going and getting stranded in space. Tow trucks for space stations cost a considerable amount more.

      Together with having a long callout time...
      • I would think my life would be in considerably more paral if I was streaking across the sky in a ball of plasma. While survivable, car hitting my car might be dangerous too.

    • pfft. (Score:3, Informative)

      by djupedal (584558)
      "It's quite another to get the metal on metal thing going and getting stranded in space"

      They have spares on board. Excepting the fact that it came as a surprise (a similar setup is ok), this is a non-issue.

  • Metal to metal grating... (Score:3, Funny)

    by RandoX (828285) on Monday October 29 2007, @08:10AM (#21156013)
    ...or something.

    Thanks for the technical breakdown. Sounds like the way Beavis would describe it. That's comforting. Or something...

  • Will a replacement fix it? (Score:5, Insightful)

    by _merlin (160982) on Monday October 29 2007, @08:13AM (#21156041) Homepage Journal
    I noted that they intend to fit a replacement joint, and are limiting the travel of the solar panel(s) in the mean time. My question is, do they know what the source of the problem actually is? Is it a manufacturing defect, damage or wear and tear in the currently fitted joint? If it is, replacing it is a reasonable solution. But if it isn't - i.e. if there's a design or operational problem - replacing it will just be a temporary band-aid, and the same thing will happen again sooner or later.

    • Re: (Score:3, Insightful)

      by Guysmiley777 (880063)
      The problem is with the right side solar alpha rotary joint, what I infer from that is the joint on the left side panel joint is working fine. Which would seem to indicate a part failure rather than an engineering problem. But I'm sure nobody can say for sure until they get a look at the failed joint.
      • Well even a part failure is an engineering failure in a space environment - i.e. if the part failed because it wasn't manufactured to tolerance, then why was this missed; If it was manufactured as designed, why was the design wrong? The fact it is a different side to me
        Either way they need to understand why this failed, how to fix it, and how to make sure this doesn't happen again.

        i.e. by definition, someone somewhere screwed up - what the concern needs to be is why this screwup was missed and how to make s

      • Re:Will a replacement fix it? (Score:5, Interesting)

        by mha (1305) on Monday October 29 2007, @08:34AM (#21156207) Homepage
        So how would you propose these things are done? I mean, things that no one's ever done before, and which you can't really simulate?

        An anecdote from my days of working for a huge German company (240000 employees) at Oracle (first job after university): I was part of the 32-64bit porting team. The question came up, are customers going to need additional or larger hard drives for the 64bit version of Oracle?

        The answer from the Germans: Well, you've got the source code. Examine all structures in the code that end up on disk and count the bytes. (we know how many Bytes an "int" takes up on 32 vs. 64bit, etc.)

        The answer from the Americans: Well, you've got the source code there. Just compile it and see what happens!

        You know, while the German approach (I *am* German) sounds a lot more "scientific" and exact I would say the American way was not just better, but the only one that actually WORKS outside a simulated computer environment with a limited number of known-in-advance factors.

        So again, how would YOU go about discovering the unknown? *I* would do just what NASA does, and what humans have done for millenia: Try, fail and try again, never approaching any ideal solution but something that works for now, until the next unforeseen thing happens.

        Of course, in the western world everything that even LOOKS like risk has to be eliminated: from hot coffee to horses with tourists on them going any faster than a slow walk (I'll NEVER go on any tourist expedition on a horse in the US again, in Germany my friends who've never been on a horse before were forced to "survive" gallop several times in a 2 hour tour - and did so with relative ease).
        • "Try and fail" can be a bad approach when you're dealing with the space shuttle, which is simultaneously the least reliable and most expensive option.

          Another option would have been to bring back the Saturn V, which despite having 10 times the payload capacity of the shuttle, costs less for a single launch. We could have had the space station built long ago for much less cost if we weren't so hell bent on using our space shuttles for everything.

          • Re: (Score:3, Informative)

            by AJWM (19027)
            In the original scheme of things -- i.e. back in the late 1970s when the Shuttle was being built -- the plan was that while the Shuttle would carry the vast majority of "medium size" payloads, they'd keep Delta around for small payloads (Delta has been upgraded quite a bit since then) and Saturn V around for the large payloads.

            Needless to say, that plan was scrapped early on. Probably just before they overhauled the VAB and Pad 39 to make them Shuttle-compatible but Saturn V-incompatible.

        • Hardware (especially aerospace hardware) tends to be a bit different than software. Like you said, with a software package I can discover an unknown just by trying. What's the worst I can do? Crash? Blue screen? Oooh, maybe if I was *really* bad I could fry the motherboard. Big deal.

          Imagine if we tried that mentality on the shuttle. Er, we don't know what this thing will do in space, well, let's launch it and hope we don't just send 9 astronauts to their doom!

          Different tools for different jobs eh? Space

          • Imagine if we tried that mentality on the shuttle. Er, we don't know what this thing will do in space, well, let's launch it and hope we don't just send 9 astronauts to their doom!

            First try: It's seven astronauts. Need Another Seven Astronauts.

            Too old-school?

            Okay, second try: Imagine if we did. Why, we'd be zipping those babies up there with big ol' blocks of ice banging into it willy-nilly, and never fear the damage it may cause!

            Yeah, that's more like it.

          • Re: (Score:3, Insightful)

            by mha (1305)
            It *is* the same, however you twist it. Of course you try a little harder when lifes are at stake. You also drive more carefully when the road seems dangerous or you are not wearing a seatbelt (on the average). Not sure what you're trying to say. When flying was discovered and aircrafts developed many died. When we went into space the human cost was low ONLY because of the enormous effort - very few people have been up there at all, and many, including those who went to the moon, were just lucky - there was

        • So again, how would YOU go about discovering the unknown?

          Flight Simulator. It's warmer in the basement. And there are snacks.

        • Space travel, the trial-and-error way, eh? You mean, Wan Hu [wikipedia.org] style? ;)

          "Early in the sixteenth century, Wan decided to take advantage of China's advanced rocket and fireworks technology to launch himself into outer space. He supposedly had a chair built with forty-seven rockets attached. On the day of lift-off, Wan, splendidly attired, climbed into his rocket chair and forty seven servants lit the fuses and then hastily ran for cover. There was a huge explosion. When the smoke cleared, Wan and the chair were
      • Cutting corners in what way? As far as the design of ISS goes, most of these designs are old news at this point. Most of the hardware for the ISS is currently just sitting in storage waiting to be loaded and lifted into space. Considering that they've got an identical joint on another set of panels that's showing no damage, it's probably not the case of it being a mechanical design defect. I think it's more likely that the joint got contaminated either while being installed or while it was being loaded.

  • Dust buster? (Score:3, Funny)

    by advocate_one (662832) on Monday October 29 2007, @08:23AM (#21156109)
    I was gonna suggest using a dustbuster to sweep up the shavings... but there's nothing to suck...
    • If the shavings are of a ferrus material a magnet might be a good idea. Otherwise I might suggest canned air. Though once I think about it you'd still have the problems of the shavings coming back due to the microgravity of the station.

      A high tech version of the push sweeper might be a better idea - rotating brushes pick up debris and pull it into a storage chamber.
      • I can't imagine the shavings coming back being a problem; the atmospheric friction already decelerates the space station so this should have a much larger effect on any shavings.
        • In the long term, yes. Especially if you concentrated on reducing the orbital velocity of the shavings when you removed them. However, the microgravitational effects of the ISS would be quite substantial in the medium term. So they might come back. It already appears to be enough to hold the shavings despite any friction.
    • They could use a swiffer dust mop.

  • From the TFA (Score:4, Funny)

    by denzacar (181829) on Monday October 29 2007, @08:30AM (#21156159)

    "It's quite clear that it's metal-to-metal grating or something, and it's widespread," Tani said.

    "Wow," said his spacewalking partner, Scott Parazynski.
    Its nice to see those "Keanu Reeves Linguistic School" classes paying off for astronauts.

  • One hell of a gear box (Score:5, Insightful)

    by BadHaggis (1179673) on Monday October 29 2007, @08:58AM (#21156469)

    The SARJ, 10.5 ft in diameter and 40 inches long, will maintain the solar arrays in an optimal orientation to the sun while the entire space station orbits the Earth once every 90 minutes. Drive motors in the SARJ will move the arrays through 360 degrees of motion at four degrees per minute. The joints must rotate the arrays smoothly without imparting vibrations to the laboratories and habitation modules on the station that would impact microgravity-processing activities. At the same time, 60 kW of power at 160 volts and multiple data channels are carried across each joint by copper "roll rings" contained within. From: Google Cached Lockeed Martin Article on the Panels. [64.233.167.104]
    The joints in question are huge and as this article points out any vibrations back into the ISS could cause problems with other equipment or experiments. Additionally power is transferred back to the ISS through copper rings in the unit itself. Any metal which provides a better circuit path than the copper would cause the power spikes.

    Opening this thing up would be something like trying to rebuild an Automatic Transmission, then add the complexity of doing this in micro-gravity. It would probably be easier for NASA to send up a complete replacement instead of trying clean out all of the metal shavings and replace the parts that are damaged.

    • Re: (Score:3, Insightful)

      by mikelieman (35628)
      Isn't this, then, *exactly* the time to learn how to do this stuff on-site? No-one said that learning was ever "easy".

  • Someone must remember the Asimov story about the space mechanics sent to check out some satellite and inside they find some kind of metal worm burrowed into the thing.

    Metal on Metal grinding? Or have we been found?
  • I didn't know the ISS had such a big despun platform. On uncrewed satellites, despun platforms have historically been a source of catastrophic failures. If the bearing suddenly locks up, the whole satellite starts spinning wildly out of control. I assume the ISS wasn't designed so that the failure of this bearing would kill eveyone aboard, but then what does happen if it fails? The article in today's NY Times says there are backup motors, but how does a backup motor help you if the bearing completely seizes
    • It only moves at 4 degrees per minute - if it suddenly stops, it's not going to result in "wild tumbling".
    • I didn't know the ISS had such a big despun platform.

      It doesn't. ISS is not spin-stabilized. Mostly it's gravity-gradient stabilized with gyros and thrusters to make up the difference. The rotating joints are to keep the solar panels pointed towards the sun while the station is at some other angle. In theory they probably don't need to do more than one rotation per orbit, although I'm sure they can rotate much faster than that.

      But nothing like the several RPMs of a spin-stabilized satellite.

    • Re:they forgot to put oil? (Score:5, Informative)

      by arivanov (12034) on Monday October 29 2007, @08:04AM (#21155977) Homepage
      Oil does not work in space. It either freezes or evaporates. In fact only some "solid lubricants" like graphite and MoS work to a point.
        • I'm surprised they're not using a magnetic bearing, considering the size and relative lack of graviational stresses. If it was properly thermally managed it might even be possible to make it superconducting, but maybe that's a stretch.

          • Re: (Score:3, Informative)

            by Agripa (139780)
            Magnetic bearings have their place but it is not in this sort of application. They excel where the physical contact of normal bearings would cause low lifetime at high speed but in other applications normal bearing are just so much easier to build, use, and replace that their limited lifetimes are not significant.

            The space station failure is probably either related to a temperature coefficient mismatch between two parts that are now rubbing or physical damage. A magnetic bearing would not specifically sol

      • Re:Incredible Spending Sink (Score:5, Insightful)

        by elrous0 (869638) * on Monday October 29 2007, @08:30AM (#21156157)

        ut we're figuring out how to live in space with this project
        Wouldn't it be a lot cheaper just to ask the Russians?

        • Re: (Score:3, Insightful)

          by mha (1305)
          Even if we just assume they know so much more (which certainly used to be true in the past when they basically had the monopoly on staying up there long-term), the answer is: depends.

          Globally, for the world as a whole, sure. Locally: no. If you never do it yourself but always ask the others they will get better and better, and you'll depend on them more and more. That's specialization all right, and according to economic theory that's a good thing. You just have to make sure you have something of equal or g
          • Sure you have to do things yourself occasionally, but there's nothing wrong with learnings from others too.. if you tried to play golf or an instrument without any lessons, then you'd be missing out on hundreds of years of experience and little techniques that could help you play/sound better. Just a silly example.. I get your point though, if you just mooch off of others then you lose the ability to fend for yourself.
        • They supplied part of the computer system and the O2 Generator.

          In addition, they have never done anything near this big. As it is, the ISS is already double the mass of MIR, and it will go up by 50%. In addition, it is about 50% more living volume than mir and will still double over the next 2 years. This is WELL beyond what russia has done. This is all an new learning experience for the world. Fortunately, this experience will enable us to go to the moon and mars a lot cheaper and faster.

          Heck, look at Ch

          • Re:Actually, we did (Score:5, Informative)

            by khallow (566160) on Monday October 29 2007, @10:26AM (#21157375)

            They supplied part of the computer system and the O2 Generator.

            The Russians also provide two or three components and a second maneuvering system. They provide the only reliable supply vehicles and as I understand it, there's a considerable part of the orbit that's over Russian space.

            In addition, they have never done anything near this big. As it is, the ISS is already double the mass of MIR, and it will go up by 50%. In addition, it is about 50% more living volume than mir and will still double over the next 2 years. This is WELL beyond what russia has done. This is all an new learning experience for the world. Fortunately, this experience will enable us to go to the moon and mars a lot cheaper and faster.

            Only three times the mass of MIR and you claim it's "WELL" beyond something the Russians have done? Nonsense. As I see it, there are a number of innovations in the structure and construction of the ISS, but the raw size isn't one of them.

            Heck, look at China. Their space program is now outspending yearly what Apollo did at its' height. And with that, they launch a fraction of the flights that did and currently do. That is because they are busy trying to acquire the same technology (generally buying it from Russia or simply stealing it from NASA and RSA).

            Where does that claim come from? Last I googled, China claims it only spends two billion a year [spacedaily.com]. In comparison, when you adjust for inflation, NASA spending in the 60's peaked above $25 billion [wikipedia.org] in 1996 dollars.
            • Yes, Russia does have the current reliable supple vehicle. And that is why I am glad that we are working with Russia. In fact, I think that we should stay partnered with them to the moon and mars.
              I know that you know that Ariene V is solid and the ATV is about to be tested. In addition, in 2009, japan is supposed to do their HLV (though, I seriously doubt it). And of course, I am one of those that believe that Spacex will be providing space launches for at least cargo by 2010 (and I believe humans before 2

      • Don't you think it'd be better if there were several ISS's up there? Because for the amount we spent on this one, we could have have two or four more up there. While redesigning the system so that the Russians ended up on the critical path was remarkably expensive and stupid, we also have a dependence on the Space Shuttle which costs $2 billion per year even if nothing is launched (as was the case from 2003-2005). And currently the projected ISS costs are somewhere over $1 billion per year. I occasionally h

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