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."

Is this needed?

[inject_hotmail.com]

"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.

Sounds like a bad idea.

[Jason1729]

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?

Re:Is this needed?

[morgan_greywolf]

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:Sounds like a bad idea.

[Rob the Bold]

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.

get rid of oxygen, instead of wires

[Anonymous Coward]

How about keeping the empty space in the fuel tank full of an inert gas?
After all, an electric spark can't ignite jet fuel if there's no air to burn it in.

Re:Is this needed?

[Gregb05]

Not without oxygen it isn't.

Re:Is this needed?

[TheBearBear]

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.

Re:Is this needed?

[Chrisq]

All gases are easily flammable! Carbon dioxide? Nitrogen? Argon?

Re:Is this needed?

[Captain Nitpick]

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.

One cannot keep the fuel tanks on any operating vehicle continuously full without shape-changing tanks. Even if one allows for a partial drop in fuel level (with the resulting fuel-air mixture being too rich to burn), this will result in reduced range, and hauling a lot of extra fuel around.

Better to remove potential ignition sources from the tank.

Re:Sounds like a bad idea.

[kmac06]

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 dispersed in the fuel rather than absorbed in one spot. The ONLY thing you would have to worry about in this case is if the light from the fiber is focused onto something that absorbs the relevant wavelength, and can heat it up enough to ignite the fuel (which may be impossible depending on the input power). Well, that and the problems with the electricity after the light is converted (which of course are there anyway).

Re:Sounds like a bad idea.

[TubeSteak]

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?

Glass fiber = static electricity?

[dpbsmith]

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.

Lousy Science

[ajs318]

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?

Re:Uh Oh ?!

[0rionx]

Of the cases listed on that Wiki page, 9 were due to pilot error, 1 due to a fuel leak, and 1 resulting from hijacking. None were a result of instrument failures, and in most of the cases of pilot error there were complicating circumstances, such as heavy storms or landing gear failing to retract, increasing fuel consumption and distracting the crew.