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Electricity Over Glass
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."
"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.
So, firing laser beams into fuel tanks is a safety feature now?
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?
...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...
Those who live by the sword, get shot by those who live by the gun...
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
Enjoy science fiction? "Turing Evolved" - AI, Mecha, Androids and rail-gun battles. What more could you want?
I think you're mixing up innovation and patent-worthiness. You must be new here.
-1 not first post
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 an ever present danger. To deal with that, we have explosion proof wiring. http://en.wikipedia.org/wiki/Electric_actuator#Explosion_protection In other words, the problem was solved long ago.
...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 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.
Still...there might be some application for this device, but it certainly WON'T be in a fuel tank.
By the way, millions or even billions of fuel level sending units have been in use in anything with gas gauge for years. How many users of such devices have been killed due to electric failures? I'm guess very very VERY few, if any at all.
I agree with another commenter when they said that they don't want frickin' lasers pointing at their frickin' gas tanks.
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.
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.
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.
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 else in the wiring harness that will accidently put a lot more power on the line. There are a TON of wires on an aircraft, going every which way, some of which can deliver a lot of power. Short one of those to the sensor line and you can get a spark in the fuel tank.
It's not wasting time, I'm educating myself.
I dunno, electricity in glass could lead to some shocking panes.
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.
"How to Do Nothing," kids activities, back in print!
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 the lines up to use less steel. (ie: This is possibly an argument against doing this). The cost savings in the tower construction outweighs the power lost in the lines.
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:
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.
Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong fix.
Unless those techniques are patented?
Je fume. Tu fumes. Nous fûmes!
OLD: The deal was finished on May 26, 2005 . 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.
You're going to overestimate your remaining fuel if you are relying on a capillary. Unless, of course, your ocular spectrogram can automatically correct for the capillary rise.
-- Cave quid dicis, quando, et cui
http://en.wikipedia.org/wiki/Category:Fuel_exhaustion_on_commercial_airliners
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...
MCSE? No, sir...I don't do Windows. Yes, I am an idealist. What's your point?
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.
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.
Je fume. Tu fumes. Nous fûmes!
Gimli Glider.