back to article Rolls-Royce to work on electric cyber raygun aero-tech

An American high-tech jet engine design bureau, owned by UK-centred firm Rolls-Royce, will design key power systems necessary for the electricity-heavy combat aircraft of tomorrow. Future fighters and bombers are expected to use huge amounts of electricity to power such things as directed-energy rayguns and/or cyberwarfare …

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Anonymous Coward

combat during solar storm anyone?

A plane relying that heavily on electricity will fall like a stone from the sky when a solar storm hits earth

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Anonymous Coward

Swings and roundabouts

Every Watt diverted to the generator is a Watt lost to moving the aircraft. Going from hydraulics to electrics won't alter the net power consumption but ever-increasing electrical demands will.

I wonder how far this can go before it gets impractical.

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Re: Swings and roundabouts

true, but given that jet engines have a power output measured in tens of megawatts, I wouldn't worry about it too much.

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Silver badge
Boffin

RE: Swings and roundabouts

"Every Watt diverted to the generator is a Watt lost to moving the aircraft. Going from hydraulics to electrics won't alter the net power consumption but ever-increasing electrical demands will...." Hydraulics don't come for free, they require a power source to drive them (either a direct drive from the engine or an electrical pump). So hydraulics are no less power-free than electrical systems.

Also, for a hydraulic system there has to be a hole for a pipe to pass through in wing struts, etc, whereas in electrical systems you can even embed the wires into the carbon-fibre skin, which means stronger struts and simpler construction. Wirelooms can easily be duplicated whereas duplicate hydraulic systems have to be balanced, and electric motors and wires are more damage-resistant than hydraulic systems.

Hydraulic pipework is also heavier than wires, especially when full of fluid, and the pipes have to be carefully maintained or they leak, and topped up regularly which means a logistics burden which is not there with electric wiring. Which brings us to another good reason for switching from hydraulics in that most hydraulic fluids are oil-based and therefore represent a fire risk, especially if a damaged pipe is spraying fluid into the engine bay. It's not a new idea, the Germans switched to electrical undercarriage and flaps for the WW2 FW190 for exactly the same reasons.

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Anonymous Coward

RE:Matt Bryant

Hmmm, mechanics and electrics obviously aren't your forte.

A watt of hydraulic power re-designed into a watt of electrical power equals one watt. No net change.

Believe it or not hydraulic systems offer the best power to weight ratio by far, hence their selection in the first place. Reliability speaks for itself.

Copper is heavy. Its selection for this project is for reasons you haven't thought of. I suggest you look up the flashpoint of hydraulic oil and also what goes into an electrical servo-actuator.

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Silver badge
Coat

or just use 5000 D cells

http://www.theregister.co.uk/2009/01/08/dad_battery_challenge_droid_sub/

It also solves the problem of the navy's new plane being too heavy to land you just pop the batteries out at then end of the flight.

Obviously you have to make sure the little red ribbon is outside - otherwise you need a pen.

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Anonymous Coward

@Matt Bryant

Wrong. The prime mover on a turbofan-equipped plane is not the jet of hot exhaust air (from which the turbine would be generating the electricity indirectly), but the turbo-fan (the big fan up front). High-bypass turbofans use only very little of the total volume of air pumped through the entire system (hence the name high-bypass).

If the appropriate changes are made inside the high- and low-pressure turbines, adding a genny on will not cause the plane to move slower. The turbofan will still move the same amount of air. However, the additional weight of copper in four powerful gennies (one per jet) could pose a performance penalty.

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Stop

RE: Anonymous Coward

Yikes !

Sorry AC you are as wrong as a very wrong thing on a very wrong day.

The piece is about combat a/c which almost always use turbojets.

Also, any power take-off via the Accessory Drive Gearbox from spool two (N2) will slow the spool due its load. This will reduce gas flow and therefore power. More fuel will be needed to get RPM back up. Max RPM / thrust will be reduced due to the extra external load.

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Paris Hilton

@ Martin

"Obviously you have to make sure the little red ribbon is outside - otherwise you need a pen."

HAHAHAHAHAHHA, hilarious. Thanks, as I'm at work on this cold (Canada) Saturday morning, I needed that.

Paris, because I'll bet she'd find that as reasonable as I do and if she thinks it's reasonable I'm sure not going to disagree ;^)

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Silver badge
Pirate

RE: RE:Matt Bryant

"Hmmm, mechanics and electrics obviously aren't your forte...." Why do I get the feeling you're about to prove neither those topics nor physics, avionics nor chemistry are yours?

"....A watt of hydraulic power re-designed into a watt of electrical power equals one watt. No net change....." Really? What, we've developed frictionless pumps, then? And weightless ones at that? I think not. All mechanical systems have losses, so 1 Watt in does not equal 1 Watt out. And then you have to consider the weight of the system, which adds to the burden of the aircraft. Hydraulics are very reliable and therefore very good for areas such as brakes on aircraft, just as they are on cars, but that doesn't mean they're good for everything, and by reducing them you reduce the load on the aircraft, the load on the engine from parasictic drives, the risk of fire (see below), and the problems of safely supplying what is actually a hazardous substance.

"....Believe it or not hydraulic systems offer the best power to weight ratio by far, hence their selection in the first place. Reliability speaks for itself...." Yes, hydraulics are reliable if well maintained. They are not the most efficient, though, as they require a lot of maintenance and are heavier than electircal systems, especially when you consider modern fibre-optic cabling promises to make electronic systems both much lighter, faster and more damage resistant. Sorry, but the text you must be using as a reference is about twenty years out of date.

"....Copper is heavy...." And what is hydraulic piping made out of, then, fairy dust and moonbeams? Try thinking before typing. Then go read up on fibre-optic looms - much lighter than copper wiring or hydraulic pipes. Even the electric motors necessary are no heavier than the valves needed for hydraulic systems.

"....Its selection for this project is for reasons you haven't thought of. I suggest you look up the flashpoint of hydraulic oil and also what goes into an electrical servo-actuator...." Well, let's see then - MIL-H-83282 has a flashpoint of 205 degrees C (I'm assuming military jets would go with the more exotic MIL-H-83282 rather than the common MIL-H-5606, which flashes at 82 degrees C, even when cut with Skydrol fire retardant). AVCAT (aka JP-5 or Navy jungle juice) burns at about 287 degrees C in open air and a lot higher if confined and fed a jet of air (like say in a fire in a holed fuselage or wing). Phosphorous will easlily set fire to MIL-H-83282 and JP-5. That's the reason just about everyone uses it in SAPI shells common to most aircarft cannon systems. Now, think carefully - which is the more dangerous, a pipe spraying hydraulic fluid or a thin piece of copper?

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