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Electricity Over Glass 187

Posted by CmdrTaco
from the still-no-sandwiches-over-plastic dept.
guddan writes "Running a live wire into a passenger jet's fuel tank seems like a bad idea on the face of it. Still, sensors that monitor the fuel tank have to run on electricity, so aircraft makers previously had little choice. But what if power could be delivered over optical fiber instead of copper wire, without fear of short circuits and sparks? In late May, the big laser and optics company JDS Uniphase Corp., in San Jose, Calif., bought a small Silicon Valley firm with the technology to do just that."
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Electricity Over Glass

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  • Is this needed? (Score:4, Insightful)

    by inject_hotmail.com (843637) on Monday December 17, 2007 @09:46AM (#21724500)
    "Running a live wire into a passenger jet's fuel tank seems like a bad idea on the face of it. Still, sensors that monitor the fuel tank have to run on electricity, so aircraft makers previously had little choice. But what if power could be delivered over optical fiber instead of copper wire, without fear of short circuits and sparks? In late May, the big laser and optics company JDS Uniphase Corp., in San Jose, Calif., bought a small Silicon Valley firm with the technology to do just that."

    What, no one ever heard of vacuum lines? Or maybe pressurized lines? I'm not a rocket scientist, or even a plane scientist, and I could figure that out before I was finished reading the frickin' summary, let alone the frickin' article.

    People love to make work for themselves...

    Setting that aside, the idea sounds awesome!...what with all the planes we lose every year to short-circuiting wires...BUT, I'll wait to see if this materialized before I get all excited about it.
    • Re:Is this needed? (Score:5, Insightful)

      by morgan_greywolf (835522) on Monday December 17, 2007 @09:52AM (#21724550) Homepage Journal
      Who even says that the sensor necessarily needs to be fully electronic? You can have a mechanical piece that sticks in the fuel tank and have an electronic control piece that's outside of the fuel tank. In fact, this is exactly how the gas gauge in your car works [howstuffworks.com]. This design has, quite frankly, worked well for decades. Sure there's a few disadvantages, but, uh, who cares?
      • Re:Is this needed? (Score:4, Informative)

        by Renegade88 (874837) on Monday December 17, 2007 @10:02AM (#21724626)
        I've replaced the gauge on a mid-eighties Buick a number of times and I can tell you live wires go into the gas tank. The transducer was a one-piece unit. Did you ever consider there is more than one way to design something? Your point, therefore, is invalid.
      • Re:Is this needed? (Score:4, Informative)

        by schnikies79 (788746) on Monday December 17, 2007 @11:14AM (#21725300)
        Unless they have changed something very recently (in the last couple of years), the guage controlling unit is inside the tank, wires and all. The only thing outside is the plug to go into the wiring harness. I've changed plenty of sending units.

        The wires for your electric fuel pump are inside the tank too.
        • Oh yea, I forgot to add that the electric fuel pump is itself submerged in fuel to keep it cool. It's not a fully sealed unit either.

          Oh course when you run your tank low the pump is above the fuel level.
      • by WED Fan (911325) <akahige@trashmai ... t minus math_god> on Monday December 17, 2007 @11:16AM (#21725318) Homepage Journal

        Speaking as a former USAF Avionics Specialist, who worked on C-5's, C-141's, and C-130's, and who personally saw a parked C-141 burst into flames on the ramp because of a fuel probe maintenance accident, let me explain things simply.

        Design considerations:

        • There are many fuel tanks on an air craft.
        • The criticality of accurate fuel readings in any attitude is much higher than with any other vehicle on the planet.
        • Large tanks have many 8+ fuel probes running into them. Some have 12+.
        • The criticality of fuel quality readings in the tank is very high.
        • Weight and simplicity are a vital factor.
        • The system has to work in extreme temperatures.
        • The system has to work in extreame teperature changes over short periods of time.

        JP4, the fuel that makes most jets run, is difficult to ignite. It needs a heat source. You could run a bare wire into a full tank and not have a problem. However, heat that wire up, and get the fuel/air mixture just right, and you have a problem. Big Boomba Problem, to quote JJB.

        The big problem is the mostly empty tank and exposed heat sources. The C-5 has a nitrogen purging system. Basically, as fuel empties from a tank, it is replaced by nitrogen. The only way that wing is going to explode is if something other than a bare wire acts on it. Then, you've got bigger problems.

        The big problem comes when you open the tank for maintenance. So, there are massive safety considerations. The C-141 that exploded in the mid-90's at Travis AFB in California blew because a jackass tech did not follow lockout/tag out procedures. The 141 doesn't have the nitrogen purge, but the tanks were open anyway. Two senior specialists were standing on top of the aircraft when the wing blew. Several others were in the cargo box. Luckily, aside from bumped elbows and bruised body parts, everyone got out o.k. We towed nearby aircraft to safer distances. There was precious little left of the burnt aircraft that identified it as such.

        Most amatuers could make a good guess at a practical design for fuel sensors, but most of the solutions developed as such will end up being to costly, too heavy, will introduce other problems such as high maint., or simply won't work in 3-d, or extreme temperatures.

        • by Anonymous Coward on Monday December 17, 2007 @12:01PM (#21725768)
          Most jets (the largest quantity number of them, civilian commercial and private aircraft including everything from jetliners to small turboprops) burn Jet-A, which is a completely different formulation from the old JP-4. JP-4 had a significant amount of lighter molecular weight hydrocarbons (e.g. more of the constituents of gasoline) blended in.

          JP-4 was also phased out of use by the USAF over ten years ago. JP-8 is used now, which is a completely different formulation from JP-4 and has much higher flash point than JP-4. JP-4 was a naptha-based fuel and JP-8 is a kerosene-based fuel. Today's Jet-A and JP-8 have very similar base formulations, but they have very different additive packages blended in. JP-8 has a much higher flash point than Jet-A too, since it is tailored for use in military aircraft that need to handle supersonic operations.
    • Re: (Score:3, Informative)

      by JonTurner (178845)
      >>Running a live wire into a passenger jet's fuel tank seems like a bad idea

      Why? it's extremely difficult to ignite liquid gasoline, or jet fuel. An air-fuel mix ignites quite easily, however. So moral of the story: if you're paranoid that wires in your fuel tank are freyed, keep your fuel tank full. Or get your crappy car fixed.

      (In fact, nearly every automobile built in the past 20 years has not one, but two powered devices in the fuel tank -- a fuel pump and a level sensor.)
    • Re:Is this needed? (Score:5, Insightful)

      by TheBearBear (1103771) on Monday December 17, 2007 @10:34AM (#21724880)
      What, no one ever heard of vacuum lines? Or maybe pressurized lines?

      I'm no rocket scientist either, and I'm sure that those rocket scientists has already consider those options you've mentioned. Perhaps because it is on an airplane going over 500mph and you have all sorts of physics and temperature considerations that vaccuum/pressurized lines are just not best suited for.
    • by vertinox (846076)
      What, no one ever heard of vacuum lines? Or maybe pressurized lines?

      1. Airplanes often travel at 30,000ft which may make it more difficult to do this on the wings (where they keep the fuel)
      2. Airplanes have a whole problem with weight versus lift ratio. If you can squeeze a few more passengers by using fiber optics instead of the gear required for the pressurized/vacuum lines then the Airline executives would prefer that.
    • OLD: The deal was finished on May 26, 2005 [compoundsemi.com]. The article referenced by the Slashdot story is from October 2005.

      NOT NEW TECHNOLOGY: They are merely piping light using fiber optics, and then using the light with photocells to create small amounts of power for use with measuring devices. The measurements are communicated back through the fiber optics, using a different wavelength.

      PATENTS? The article says, "Photonic Power owns key patents..." Can the generation of power using light be patented again? Can sending information using fiber optics be patented again? Maybe the company has patents, considering that the U.S. government has become corrupt, but it is difficult to believe that any patents could be valid.

      IGNORANT: See this quote from the article referenced in the Slashdot story: "... the company's fastest growing sector is currently electric power transmission. One important application is eliminating the transformers used to step down high currents and voltages to measurable levels."

      The article should have said, "... the company's fastest growing sector is currently powering and connecting the measuring devices used in electric power transmission."

      The writer does not understand that the idea does not change the measuring system, only the method of transmitting the data. If step down transformers are part of the method of measurement, they will still be required. The "senior research analyst" who was quoted, Vincent Lui, doesn't understand that, either, apparently.

      REALITY RULES: If you play video games too much, your brain will become partly useless for other things, and, if then try to be a Slashdot editor, you won't be able to do a good job. (This is a theory that seems to fit the facts.)

      This is a useful idea for computer professionals in some cases where voltage isolation is needed, but the Slashdot story was mishandled, as often happens.
    • Re: (Score:3, Informative)

      by russ1337 (938915)

      What, no one ever heard of vacuum lines? Or maybe pressurized lines?

      Aircraft are required to operate at various altitudes (which have various temperatures and pressures) making compensating for differences in pressures and temperatures in a system that requires vacuum lines more difficult (and more difficult to maintain and keep calibrated). Early aircraft had a sight glass on the outside of the tank, but these are only good for reading volume and at a specific aTTitude (i.e on the ground) intrinsic [omega.com]

    • Re: (Score:3, Interesting)

      by kestasjk (933987)
      I watched a documentary about the only case I know of where a plane went down due to a short circuit in the fuel tank, and after I tell you how it happened maybe you'll see why this new tech will be a welcome addition to aircraft safety.

      I think it happened a few months after 9/11 and happened to a plane leaving JFK airport, so everyone initially assumed it was terrorists. (Just to help jog anyone's memory, not making a point here)

      IIRC the power cables that went into the fuel tanks weren't at a high en
    • by hey! (33014)
      Ye Gods; your post gave me PTSD flashbacks to working on my '76 Pinto.

      Back in '76 emissions controls were in full force, so the engine performance had to be tweaked in all kinds of subtle ways. Unfortunately, engine computers were still a pretty exotic idea, certainly not something that they'd consider for a cheap pony car at the end of its model lifespan. So the answer was vacuum lines. Lots and lots of vacuum lines. Some of them were big rubber affairs, like the ones going to the EGR. Others were sti
    • by ceoyoyo (59147)
      Some might argue that shining a high powered laser into a fuel tank is a bad idea too. Probably a worse idea than a live wire.
  • by stinky wizzleteats (552063) on Monday December 17, 2007 @09:47AM (#21724506) Homepage Journal
    So, firing laser beams into fuel tanks is a safety feature now?
    • Re: (Score:3, Funny)

      by ByOhTek (1181381)
      yes, but will they run on sharks?
  • by Jason1729 (561790) on Monday December 17, 2007 @09:48AM (#21724510)
    But what if power could be delivered over optical fiber instead of copper wire, without fear of short circuits and sparks?

    You're stilling bringing as much power into the fuel tank. High-power beams of light aren't any safer, a laser can cut inch thick steel.

    At least electricity is very well understood, we know how to insulate the wire, we know how much voltage will spark in a given medium, and the low voltage for sensors is very safe.

    High energy lightbeams are not at all well understood. Will the fiber heat up? What about light leakage, will that cause an explosion? What if the fragile fiber breaks while the beam is on?
    • by Lally Singh (3427)
      And how much power do you need to run a sensor?
      • by Rob the Bold (788862) on Monday December 17, 2007 @09:59AM (#21724606)

        And how much power do you need to run a sensor?

        Not much, at least compared to what it takes to run a pump motor. And at least jet fuel isn't nearly as volatile as gasoline, which is pumped every day with submersible electric turbine pumps at nearly every gas station in the developed world. It's a PITA to make intrinsically safe electric circuits, but it's well understood and done every day.

        The light powered device might be useful in planes if they could achieve the same degree of intrinsic safety at a lower weight.

        • The light powered device might be useful in planes if they could achieve the same degree of intrinsic safety at a lower weight.

          I think that makes sense, lower weight means higher overall efficiency.
          But it's the safety aspect that they seem to be pushing, Quote TFA;

          ...has developed a system that uses a laser to inject power in the form of light into a fiber-optic cable and a photovoltaic (PV) array to convert the light back into electricity for powering devices...

          I might be wrong but I think large aircraft fuel tanks are part of the wings so there is no choice but to put wires through the cavity that holds the fuel.
          The article links to a picture of the 1996 TWA flight 800 [wikipedia.org] reconstruction to drive the point home.

          • Re: (Score:3, Informative)

            by russ1337 (938915)

            I might be wrong but I think large aircraft fuel tanks are part of the wings so there is no choice but to put wires through the cavity that holds the fuel.

            Most of the wing is the tank, but not all of it. There is room behind the 'leading edge' and the trailing edge (between the aft of the tank and the front of the flaps/ailerons. ) This is where other services go, such as air ducts for the leading edge De-Icing (heating) systems, and wires that run to those little navigation lights way out there on the

      • by JonTurner (178845) on Monday December 17, 2007 @10:04AM (#21724636) Journal
        Millivolts. Most level sensors are variable resistors, so you only need to exceed the forward min. bias of the resistor (see the spec. sheet) to have accurate results. Above that, it's just a matter of calibration and maintaining a well-regulated power supply.
        • Re: (Score:2, Informative)

          by AP2k (991160)
          A well regulated power supply required to stabilize a millivolt source with any semblence of accuracy is far too bulky and expensive to ever be considered. Beyond that, the noise inherent in the wiring would give lots of false readings at all operating temperatures. The ADC in the measuring circuits are also not standardized much below 1V, if there are any manufacturers that produce them at all; lets not even consider the exceptionally poor resolution they would give.

          Thus, such a system would be extremely c
    • You're stilling bringing as much power into the fuel tank. High-power beams of light aren't any safer, a laser can cut inch thick steel.

      It's a lot easier to ensure the power is properly limited. Running a sensor is a low power application (you wouldn't be using a "steel cutting" laser), and the power is limited with the size of the laser diode. There's no other way to get power through the line.

      With electric lines, the issue is whether the wire to the sensor is going to short to another wire somewhere

    • Re: (Score:3, Insightful)

      by kmac06 (608921)
      No, no and no. Some (very high power) lasers can cut steel. Those lasers have many orders of magnitude more power than your standard laser pointer, which is probably amount the amount of power necessary to work a couple of sensors. High energy lightbeams are very well understood, I don't know how you could think otherwise. No, the fiber will not heat up (fibers can safely carry kilowatts or more of laser light without melting). Light leakage would be very small. If the fiber breaks, the light will be disper
    • by TubeSteak (669689) on Monday December 17, 2007 @10:54AM (#21725082) Journal

      You're stilling bringing as much power into the fuel tank. High-power beams of light aren't any safer, a laser can cut inch thick steel.
      Technically, since their solar cell is only 40%-50% efficient, they're pumping in twice as much "power" into the fuel tank. So yes, while there are lasers that can cut steel, there are also lasers that can be safely shined into your eyeball without causing any harm.

      About the only valid sentence in your post starts with "electricity is very well understood". The rest of it just reflects your ignorance.

      "High energy lightbeams are not at all well understood" by you. Light leakage causing an explosion? Seriously?
    • by AmaDaden (794446)
      More importantly you have to make the Light to Electricity transfer. Since this will be highly costly you need to have far more energy coming in then before. I'm guessing the reason they are still looking at this is because light disperses easier then electricity. Electricity can build up and then spark. Light only heats up as far as I know. So as long as the tank can cool it should be ok.
    • by DieByWire (744043)

      What about light leakage, will that cause an explosion? What if the fragile fiber breaks while the beam is on?

      Ahh, that's it. I always wondered why the gas tank filler neck on my truck has that little flapper at the top. It's to keep the light out!

      The people who made my gas cans sure screwed up, though. No light blocking flappers on them. I'm lucky I haven't been torched. From now on, I only open them at night.

  • ...have been using similar technology for some time.

    however, there is a problem with what is called dark current. that is when there is no light hitting the transducer, and there is still a current being developed...
  • Intrinsic Safety. (Score:5, Interesting)

    by GrpA (691294) on Monday December 17, 2007 @09:53AM (#21724556)
    There is nothing wrong with running wires into petrol tanks for sensors... Take a good look at how badly made the rheostats in everyone's pertol tanks are made. Most engineers freak out when they see them for the first time.

    However the design is what is known as "Intrinsically Safe"... ie, it can't cause an explosion.

    Currents, voltages are limited. Components are overrated by a set amount.

    I've never heard of any intrinsically safe circuit igniting gasoline.

    So what if you use fiber optics to provide the power. It's still electronic circuits in the tank, except now they are a whole lot more complicated and have power generation and regulation circuits, which make it a whole lot more dangerous...

    And please don't just say encapsulate the dangerous stuff, because I'm sure that won't explode with a pressure build up if a component dies (as they tend to do in regulated power circuits).

    It really scares me how such "great" ideas like this seem sane, when the original technology was probably safer.

    GrpA
    • Re: (Score:3, Informative)

      by Rob the Bold (788862)

      There is nothing wrong with running wires into petrol tanks for sensors... Take a good look at how badly made the rheostats in everyone's pertol tanks are made. Most engineers freak out when they see them for the first time.

      Good point. Note that electronic sensors are also used in underground (and above-ground) storage tanks. Electric turbine pumps, too.

    • Well, the reality of it is, gasoline won't burn without a ready source of air, so the danger of a spark inside a tank of gas is minimal until the tank itself is ruptured. And if you can keep the bulk of the components outside the tank anyway, then it doesn't matter if they're more prone to failure.

      Other than that, I tend to agree. Stick with the reliable, proven method, until the alternative offers enough benefits to make the risks worthwhile.
    • by MightyYar (622222)

      I've never heard of any intrinsically safe circuit igniting gasoline.

      Ahh, but flight 800...

      The source of ignition energy for the explosion could not be determined with certainty, but, of the sources evaluated by the investigation, the most likely was a short circuit outside of the CWT that allowed excessive voltage to enter it through electrical wiring associated with the fuel quantity indication system."

      The problem wasn't the safe circuit, it was that the wires made a path into the fuel tank. Sometimes circuits don't stay the way you built them :) An optical path would off

      • by GrpA (691294)


        Yes, TWA 800.

        Well, the biggest problem with Intrisically Safe designs is that they don't tend to be nearly as safe when they get struck by missiles... :)

        I thought it was interesting though. I don't actually know enough about that aircraft to know if it was an intrinsically safe design that went wrong or just bad design.

        Of course, Avtur - or Kerosene, doesn't ignite with a spark or even a flame - try it. It takes a LOT more, so I'm not really sure how the middle tank went up. You need heat and pressure too.
        • by MightyYar (622222)

          Or of course, it might really have been that the wires became frayed after being struck by a missile :)

          Oh, stop :) I think they made a South Park about people like that!

          The center fuel tank was actually empty, and thus full of vapor. It is true that jet fuel would not have exploded, but in certain conditions the vapor can be explosive.

          Here is a pretty good, if dated, analysis. [wisc.edu] From the link:

          The temperature inside the central fuel tank of TWA Flight 800 was unusually high, and probably played a significant role in the explosion. When fuel is heated, a greater portion of it exists as vapor, thus increasing th

    • Re: (Score:3, Interesting)

      by IcePop456 (575711)

      It really scares me how such "great" ideas like this seem sane, when the original technology was probably safer.

      It also bugs me, as an engineer, when people want better, faster, cheaper, but then refuse change. I hear numerous stories from my coworkers who used to design parts for the automotive industry. Apparently they had to come up with improvement plans and present them only to have the "what we have works, why change it?" mentality. Follow this with, now do it for less because we are going to buy the same system for less money each year...but remember, don't change or improve anything. Sounds dumb? Obviou

    • Re:Intrinsic Safety. (Score:5, Informative)

      by Cassini2 (956052) on Monday December 17, 2007 @10:34AM (#21724900)

      Intrinsically safe circuits can ignite gasoline when they are hit by lightning. The concern in aircraft applications isn't that the fuel ignites in normal operation. Rather, it is suspected that some airplanes have exploded after being hit by lightning.

      If enough power hits just the right wire, and the tanks are near empty (with lots of explosive fuel vapors), and enough planes get hit by lightning in flight in a sensitive location, then potentially disaster can happen. The accident data says fuel tank explosions occur, and this might be a possible cause. Safety problems demand a precautionary approach. Hence the desire to eliminate the wire going to the fuel tank.

      Further resources:
      http://www.epa.gov/fedrgstr/EPA-GENERAL/1997/April/Day-03/g8495.htm [epa.gov]
      http://easa.europa.eu/doc/Events/fueltanksafety_24062005/easa_fueltanksafety_24062005_large_transport_ppt.pdf [europa.eu] [pdf]

      Note: a widespread consensus exists that many possible ways for fuel tanks to ignite exist. As such, most of the focus is on minimizing the likelihood of ignition, rather than one specific cause, like the fuel tank wires themselves.

      • by ajs318 (655362)
        A lightning strike is pretty extreme. There's enough potential difference there to ionise the insulation on the wires (especially if it's PVC; a chlorine atom attached to every other carbon atom looks "just polar enough"). Under which circumstances, it tends to stop insulating.

        Even fibre optic cable -- or its outer protective sheath -- can potentially become conductive.
    • by Skweetis (46377)
      In order to ignite the gasoline or jet fuel (essentially high-octane kerosene), you need two other things: a spark which brings the temperature of the fuel to its flash point, and oxygen. You're absolutely right, a low-voltage/current sensor would never be able to spark enough to bring the fuel to its flash point, and if it's submerged in the fuel, it doesn't matter anyway, there's no oxygen available for ignition. Properly insulate the sensor, and it's extremely safe.

      Actually, gasoline can be used to pu
      • Re: (Score:3, Interesting)

        by GrpA (691294)
        Actually, there's a lot of air in the tank anyway, especially when it's nearly empty, so a spark would be bad news.

        Intrinsic Safety [wikipedia.org] is better explained on the Wikipedia that I did in the post.

        And the insulation doesn't exist in the rheostat - just wires rubbing together in the presence of fuel and air, but as I mentioned, it's extremely rare for car fuel tanks to spontaneously explode, which is probably a good example of why intrinsic safety designs work so well :) (Yes, the wires in a fuel tank have
    • There is nothing wrong with running wires into petrol tanks for sensors. [...] Currents, voltages are limited. Components are overrated by a set amount. [...] So what if you use fiber optics to provide the power.

      If the wires short with something outside the tank (even far away), that power is now going inside the tank where it could cause sparks. With fiber optics it's virtually impossible to cause a spark via light. I'm assuming the fiber would carry very weak light, on the level a solar calculator uses,

      • by GrpA (691294)
        See my comment above.

        If the diode driver circuit is hit by lighting, the output will be in the order of watts before the diode disappears... Way more than a CD burner. Anyone who's worked with LEDs knows how easily you can overdrive them if you have the duty cycle low enough. Basically, the power limitation in LEDs is based on how quickly they can dissipate the heat. This is the same for many electronic circuits.

        But having thought it through, I'm thinking that even with wires inside the tank, I've heard of
    • by nahdude812 (88157) *
      Just curious, is there a reason that fuel levels can't be read entirely by fiber optic? Place a fiber end every few millimeters, place a light source (also carried by fiber optic) at the top of the tank, and measure the total light coming back on the incremental fiber. If the fuel is not opaque enough to accommodate (gasoline is pretty clear, I don't know about jet fuel but for some reason I think it is not), put a floater in front of the return fibers and identify which ones are blocked.
      • by meatspray (59961)
        Or weight sensors under the tank, or optically via shooting visible light through the tank top to bottom and reading the loss, or acoustic range finding from top down or PSI sensors at the bottom of the tank.

        There are a million ways to do this. Some tech firm just came up with an idea to combine laser transponders with solar cells and is trying to find something to do with it.

        I saw once on TV that they add agents to the fuel to make it even less flammable and a red dye of some sort but it was years ago an
    • People always complain about battery monitors being inaccurate (spending 90% of their time at full charge and 10% of their time on the way down). I always wonder why people can't build a reasonable fuel gauge, as they seem to suffer the same problem. It would seem like these measurement biases could be calibrated out, but I guess it isn't that easy.
      • Re: (Score:3, Informative)

        by ajs318 (655362)
        Battery monitors are trying to do an incredibly tricky job. For all practical battery chemistries, the fully-charged voltage is only a tiny fraction more than the to-all-intents-and-purposes-spent voltage.

        There are battery charging monitors that integrate the current over time to get an idea of how many amp-hours are remaining, but even these don't account for the tendency of most battery chemistries to self-discharge.
    • by afidel (530433)
      Well the theory about limiting current works until there is something wrong with an adjacent high voltage line and current is either transfered or induced powerful enough to cause a spark. This is known to have taken down several airliners over the years. If you were to make an intrinsically safe circuit that was powered by light it would be MUCH more difficult for such a fault to occur. I'm not an electrical engineer but assuming JDS can design such a circuit then it would in fact be more safe than running
  • by Anonymous Coward
    Why bother with electricity at all. A piece of fiber to an optical encoder would do the job just fine. I can't think of any sensor that couldn't be implemented optically.

    Having said the above, the product seems like a solution in search of a problem. I can't recall any incidents where a fire or explosion was caused in an airplane because of faulty wiring in the fuel tank. There are lots of places where an electrical spark could cause an explosion. For instance in a mine, or factory, dust explosions are
  • ...and found that they said "Such transformers are large and necessarily heat up, which can lead to hot spots. To prevent equipment temperatures from rising to dangerous levels and to reduce power leaks, oil and gas are used as insulators. But oil is flammable and can make the transformers explode at high temperatures. The transformers are also expensive to install and maintain."...

    Say what?!? Ok...so, yes, I'd much rather have the manufacturer disclaim that they can't be sure that their product won't expl
    • I'd much rather have the manufacturer disclaim that they can't be sure that their product won't explode (thusly guaranteeing all hands lost), than use wires that have have never caused a problem in the manner in which the manufacturer of said bomb-like device

      I'm not defending this new technology, in fact I agree with you. However that said, they're was at least one documented case of a plane blowing up because of a failed fuel sensor. Actually, it wasn't the sensors fault, but rather it's low current wire c
  • Power is still power. Whether you're pumping 100 mW of electricity or light into a fuel tank, I don't see a difference.

    We already have intrisically safe electrical technology for such things. As long as you limit the power so that there isn't enough to create an ignition source, you're golden.

    Personally I'd prefer new sensor technology that allows sensing the desired quantity with either less power or from a safe distance, like ultrasonic level sensors and such.
    • by artg (24127)
      So electrical and optical power is power, but acoustic power isn't ?
    • Power is still power. Whether you're pumping 100 mW of electricity or light into a fuel tank, I don't see a difference.

      There isn't much diffrence between feeding 100 mW opticaly or not.

      "where electromagnetic interference is more than just an inconvenience"

      Feeding 100 mW sensor and getting a 50 nW signal back with 25 mW of induced ground radar or cell telephone signal on top is the problem. It swamps the signal. In extreme cases such as a close lightning strike, the induced power could be enough to create
      • by RobinH (124750)
        Feeding 100 mW sensor and getting a 50 nW signal back with 25 mW of induced ground radar or cell telephone signal on top is the problem. It swamps the signal. In extreme cases such as a close lightning strike, the induced power could be enough to create a spark. The optical is for noise rejection and less for fire safety.

        This makes a lot more sense. We already have industrial protocols like SERCOS for closed loop motion control that are based on fiber, specifically for high data rate and noise immunity. H
  • by Ihlosi (895663) on Monday December 17, 2007 @10:10AM (#21724690)
    One of the main applications for this will be when galvanic isolation of the components is required. This has fairly little to do with fuel tanks, but is interesting for various medical applications, applications in humid environments, and so on.
  • How much Power? (Score:3, Interesting)

    by sadtrev (61519) on Monday December 17, 2007 @10:12AM (#21724710) Homepage
    This development would be great for Intrinsically Safe (EEx etc) instrumentation applications.
    Current ATEX regs make it awkward to supply anything above about 1Watt at 6V.
    Most people resort to pneumatics and/or keeping the computational logic outside the zoned areas.

    Disappointingly for IEEE, he article is sparse in terms of technical details, such as the power/size ratio.
  • Right, so instead of running electrical cables into the fuel tanks, we'll just shoot lasers into them instead.
  • by RyoShin (610051) <tukaro@NosPAM.gmail.com> on Monday December 17, 2007 @10:50AM (#21725040) Homepage Journal
    I dunno, electricity in glass could lead to some shocking panes.
  • A small tube is lightly pressurized with a known gas. A mechanical sensor at the far end moves a tiny piston in or out of the tube to measure fuel level or temperature. At the near end, a device emits an acoustic pulse into the gas and measures the return reflection timing. This timing gives the length the piston has moved in the tube. The tube can be made of metal (well grounded to the tank frame at many points) or other reasonably rigid materials.

    One tube can even be used for multiple sensors. This

  • by dpbsmith (263124) on Monday December 17, 2007 @11:01AM (#21725176) Homepage
    No, probably not, although friction on glass does develop a static charge, and under the exact right bad conditions could conceivably cause a spark. As others have observed in this thread, premise, as presented in the posting, is stupid and promotional.

    The safety of stuff in a fuel tank depends on a) how well the risks are understood, and b) how well the engineering to mitigate them is performed.

    It's a standard rhetorical ploy to assert that because something is different from an older technology, it is automatically free from the problems of the older technology... and, without saying so in so many words, allowing the listener to infer that it does not have equivalently bad new problems of its own.

    The first time I heard groove-skipping on a CD, I laughed out loud. With all the promotion of the digital perfection of the CD, the fact that it suffered from exactly the same problem as a vinyl LP was... delightful.
  • by Anonymous Coward
    If they can scale this technology up to usable levels, would the power loss of the conversion outweigh the power loss to heat/resistance in High Transmission Lines? Obviously not over short distances, but imagine how it would play out over the thousands-millions of miles in the electrical grid.

    For an idea of the scale of loss versus cost of power: some power companies are currently willing to take the hit in lost power by using aluminium lines instead of copper, because they can engineer the towers holding
  • Lousy Science (Score:3, Insightful)

    by ajs318 (655362) <sd_resp2 AT earthshod DOT co DOT uk> on Monday December 17, 2007 @11:18AM (#21725328)

    Running a live wire into a passenger jet's fuel tank seems like a bad idea on the face of it.
    Only if you don't understand the basics of electronics or chemistry. One would hope that aircraft designers and constructors would have studied the science in these fields (mind you, if they're Americans, they probably think that God Did It, End Of Story; and if they're British, they probably think that All Beliefs, Even Demonstrably Untrue Ones, Are Equally Valid).

    Still, sensors that monitor the fuel tank have to run on electricity, so aircraft makers previously had little choice.
    You can use a low enough voltage that it won't spark; and you can use sufficiently-close contacts that even if it does spark, there will be insufficient energy to ignite the fuel.

    Unless those techniques are patented?
  • by Ancient_Hacker (751168) on Monday December 17, 2007 @11:26AM (#21725404)
    Formidably silly article, for many reasons:
    • Exploding gas tanks are very low on the list of problems, sorted by frequency and severity. If we spend money on these less severe problems, we're taking money away from figting more serious and cost-effectively attakcable problems.
    • The problem is having explosive mixtures in gas tanks. Rather easily solved by plumbing a little engine exhaust gas into the tanks to displace the oxygen. Done for decades on tanker ships.
    • The typical sensors in airplane tanks are capacitive dielectric guages. These can easily be made to run on microwatts of signal, not enough to cause ignition.
    • Even if the sensors were a problem, which they're not, and you replaced them all with some new method, you'd still have all the other sources of ignition, including sulfur chemical catalsys, static discharges, lightning, friction, and more. You need to make the stuff non-explosive or ignitable, see point #1.
    • by TubeSteak (669689)

      Exploding gas tanks are very low on the list of problems, sorted by frequency and severity. If we spend money on these less severe problems, we're taking money away from figting more serious and cost-effectively attakcable problems.

      Running a cost:benefit analysis on problems is a really stupid way to design something. Especially an airplane.

      Engineers spend a disproportionate amount of effort (which means money) working to prevent things that might happen 1% of the time.

      Why? Because those 1% events usually end up as huge fucking disasters.
      "But it only happens 1% of the time!" say the penny pinchers.

      Multiply all the airplanes in service by 1% and they'd start blowing up left and right because you thought it is good to be "figting more

  • by element-o.p. (939033) on Monday December 17, 2007 @11:42AM (#21725586) Homepage
    I thought capacitance based fuel sensors solved most, if not all, of the problems of sparking inside fuel tanks by keeping the powered components on the *outside* of the fuel tank. Is there some problem with accuracy or reliability that makes them unsuitable for commercial aviation that I'm not aware of or is this a solution searching for a problem?

    And for all of the people asking how often sparking inside a fuel tank causes a tank to explode, yes, it *does* happen sometimes. The final NTSB report on the airliner that crashed off New York about a decade ago (you know, the one that the conspiracy theorists said was shot down by a hand-held SAM) was due to sparking inside the fuel tank. I'd link to it, but I can't recall the flight number, and I don't have time to search for it right now...
    • Re: (Score:3, Informative)

      by trayrace (1182967)

      Flight 800? [wikipedia.org]

      The NTSB investigation ended with the adoption of their final report on August 23, 2000. In it they concluded that the probable cause of the accident was "an explosion of the center wing fuel tank (CWT), resulting from ignition of the flammable fuel/air mixture in the tank. The source of ignition energy for the explosion could not be determined with certainty, but, of the sources evaluated by the investigation, the most likely was a short circuit outside of the CWT that allowed excessive vol

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