Siemens and Airbus To Push Electric Aviation Engines (networkworld.com) 242
coondoggie quotes a report from Networkworld: Siemens and Airbus teamed up today to develop electric and hybrid electric/combustion engines for commercial and private aircraft. The companies said they would amass a joint development team of about 200 employees that would jointly develop prototypes for various propulsion systems with power classes ranging from a few 100 kilowatts up to 10 and more megawatts, for short, local trips with aircraft below 100 seats, helicopters or unmanned aircraft up to classic short and medium-range flights. Hybrid-electric propulsion systems can significantly reduce fuel consumption of aircraft and reduce noise. European emissions targets aim for a 75% reduction of CO2 emissions by 2050. These ambitious goals cannot be achieved by conventional technologies, the companies stated. Airbus has developed a 2-seat electrically powered aircraft, known as the E-Fan. Siemens too has been developing an electric aircraft engine.
Energy density per kg (Score:4, Interesting)
Is the energy density per kg of batteries really that much better than the energy density of methane gas, or liquid hydrogen?
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Re: Energy density per kg (Score:2)
Re:Energy density per kg (Score:5, Insightful)
I would imagine not. On the other hand, there are other ways of storing energy than batteries (like hydrogen fuel cells).
Get the electric airplane engine working. Let someone else worry about storing the electricity to power it.
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If the hydrogen is from a carbon neutral source, which I assume it must or it's a waste of time, then would it not be more efficient to just burn the hydrogen in a traditional jet engine? Looking to Rube Goldberg for hints on aircraft design does not sound like a good idea to me.
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Re:Energy density per kg (Score:5, Interesting)
There are other advantages to hydrogen as a transport fuel besides the tree-hugger appeal.
There are also many disadvantages. Hydrogen eats steel and aluminum. It has a much poorer energy density by weight and volume than jet fuel. I could come up with more if I wasn't so tired right now but those two alone really kills hydrogen as aviation fuel, especially if derived from a very useful fuel like natural gas (which is mostly just methane) or propane.
Since the entire goal of using this system is to improve the efficiency of burning the jet fuel then producing hydrogen from a fossil fuel sounds like you'd be going backwards. Part of the energy of the fuel is in the carbon hydrogen bonds, if you break those bonds on the ground to make the hydrogen then it is not contributing to the movement of the plane in the air.
Unless you can show me where I've gone wrong, or something I missed, I still think that hydrogen fuel for airplanes is a very bad idea with the possible exception of hydrogen derived from cracking water with power derived from nuclear fission. I won't even consider wind, solar, or geothermal good alternatives since they currently cost more than nuclear power.
Nope. When you burn anything in an internal combustion engine, more than half of the energy from the reaction is lost as exhaust heat.
That would be relevant if the aircraft in question did not have an internal combustion engine. What they want to do is run a generator with an internal combustion engine, then use that electricity to run a motor that drives a ducted fan. While you caught me on the thermal efficiency angle since they claim to reduce fuel consumption by 25% with this system they also hope to gain on efficiency by having batteries be part of the airplane structure. That is not a simple task and they know it.
Their claim of these efficiency gains comes from the hope that they can develop an electric storage system suited to power an aircraft. Since we have not even found a suitable storage system for the much simpler problem of electric cars and trains I believe they are not going to find that solution soon. If they do then perhaps we can see internal combustion cars get beat out by pure electric and electric hybrid cars on every price point, not just luxury cars and tree hugger magnets.
If I use the definition of efficiency to refer to it's cost and complexity, and not it's ability to convert fuel to forward motion, then a common jet engine is more efficient than the hybrid. For an airline this is a make or break matter, they run on total cost of ownership. For a personal vehicle this might not be so critical since a hybrid might offer other advantages such as comfort, performance, or just bragging rights, that a common jet engine would not have.
Re:Energy density per kg (Score:4, Interesting)
Liquid Hydrogen would work well in Commercial jets - massive reduction in fuel mass reduces structure weights. It doesn't matter much that have to store fuel in fuselage tanks (just make a bigger fuselage), because so much of plane power use is to lift 1/3rd of takeoff mass in kerosene and bigger engines to accelerate it at takeoff.
EG 787-8 takeoff kerosene is 130tonnes dry, 100tonnes out of total 230tonnes needing about 125m for average mission weight of 180 tonnes.
LH2 would be about 140 tonnes for 25% power or energy saving, needing about 24 tonnes of fuel (engine and landing gear and structure would be lightened) and needing about 350m (tanks about 3.5 tonnes) in a fuselage length of 14m (which is roughly difference between the 787-8 and the 787-10).
If necessary you can just make your jet fly higher to reduce relative size of fuselage compared to larger wings, gives benefit of more internal volume for comfort.
Liquid Hydrogen is probably the best fuel for supersonic use - as it cuts fuel weight by about 75% (about 40-50% of takeoff weight) lowering structural loads and weights, lowering thrust needed proportionally and lowering boom noise by up to half (perhaps more if flying higher), and can easily give global range (eg see lapcat). Also possible advantages in improving gas turbine efficiency through pre or intercooling or using a superheated rankine cycle on the LH2 for even bigger fuel savings. Can also cool passengers.
LH2 would also be fine in Trucks and Ships. What it really sucks at is intermittent small applications like cars motorbikes etc where small scale long term storage issues and close proximity to humans make it dangerous. Fortunately batteries are good enough for that.
So in a post fossil fuel world LH2 is pretty attractive for all sorts of transport, as long as we can find cheap methods of manufacture (ideally nuclear or perhaps southern ocean floating wind turbines or around Antartica to use collosal power available in katabatic winds there.)
Comment removed (Score:4, Insightful)
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Ummmm.....I thought the first stage of Saturn V burned kerosene and LOX. Second and third stages burned liquid hydrogen and oxygen.
Re:Energy density per kg (Score:4, Insightful)
I assumed they meant to say "wasn't" ;)
Indeed, to sum up:
Mass density: excellent
Volumetric density: horrible
Thrust: poor (though probably not an issue for passenger jets)
Ease of ignition: easy. Burns aggressively in almost any fuel-air mixture, requires only a trivial spark to ignite, and burns can accelerate from deflagrations to detonations in many circumstances.
Ease of accidental ignition: likewise, easy.
Liquid storage: very difficult. High boiloff rate (liquefies air outside its tank), lots of energy goes into creation (incl. ortho/para conversion), entrained air freezes out as a highly explosive ice, subpar compatibility with composites, metal embrittlement over long periods. Boiloff gases pool under overhangs / enters pipes & follow them to their destinations.
Gas storage: difficult. Requires very high pressures for even low densities; high leakage rate and metal embrittlement over long periods. Leaked gas pools under overhangs / enters pipes & follows them to their destinations.
Airflow required for stoichiometric burn: high (~17kg air per kg kerosene, ~40kg air per kg H2)
Basically: as a fuel, hydrogen is both wonderful and terrible.
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Part of the energy of the fuel is in the carbon hydrogen bonds, if you break those bonds on the ground to make the hydrogen then it is not contributing to the movement of the plane in the air.
Unless you can show me where I've gone wrong, or something I missed, I still think that hydrogen fuel for airplanes is a very bad idea with the possible exception of hydrogen derived from cracking water with power derived from nuclear fission. I won't even consider wind, solar, or geothermal good alternatives since they currently cost more than nuclear power.
That depends if you're a lone source then it's energy inefficient. But there's more energy in a H-H bond than a H-C bond so Hydrogen itself is quite a viable fuel. The question of how to make it is more interesting. Yes building a plant to produce just hydrogen is wasteful. However Hydrogen is a by product of many other processes and at least one refinery I know of generates enough waste hydrogen that they can't actually export it all with the facilities they have... so they just send it to the flare.
That s
Re:Energy density per kg (Score:5, Interesting)
Aircraft are only now beginning to use turbines to generate electricity which is then used in electric motors but is is a very widely used technology in many ships -- especially large warships.
A first application for adding an electric engine to the tail end of an airliner to re-energize the fuselage boundary layer airflow. As the plane flies through the air it slows down some of the air which ends up as drag. By putting a ring around the end of the fuselage directing the boundary layer airflow to an electric engine powered from the main turbines, drag goes down to the point that smaller diameter engines are needed (also diminishing drag). The major design change needed is that with the ring and engine, the horizontal stabilizers must be moved to a T tail.
Both NASA & Airbus are studying this for future designs: see here [aviationweek.com].
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Aircraft are only now beginning to use turbines to generate electricity which is then used in electric motors but is is a very widely used technology in many ships -- especially large warships.
A first application for adding an electric engine to the tail end of an airliner to re-energize the fuselage boundary layer airflow. As the plane flies through the air it slows down some of the air which ends up as drag. By putting a ring around the end of the fuselage directing the boundary layer airflow to an electric engine powered from the main turbines, drag goes down to the point that smaller diameter engines are needed (also diminishing drag). The major design change needed is that with the ring and engine, the horizontal stabilizers must be moved to a T tail.
Both NASA & Airbus are studying this for future designs: see here [aviationweek.com].
Do you ever fly?
APUs have been in aircraft in various forms since World War 1. Modern APUs are turbines that burn jet fuel.
Next time you are close to a big plane, look for a small-ish vent on the wing or the tip of the fuselage. Large planes (and lighter than air aircraft) have had these for a century already.
Your article does have some interesting ideas about using drag envelopes to gain an efficiency advantage, but the idea there haven't been separately powered generators on aircraft before is false.
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The previous poster was referring to a motor-generator system, where turbine engines are used to generate electricity to power electric motors that drive the propellers. The APUs you confused them with are "Auxiliary" Power Units, and have never been used to make the plane move.
What I wonder about in such a system is the cost of converting the power to electricity before creating thrust. You have to carry around heavy coils of wire in each motor and generator, whereas the turbofan only has to carry a driv
Re:Energy density per kg (Score:4, Insightful)
Hydrogen eats steel and aluminum.
I noticed there is a strong groupthink on Slashdot that is against hydrogen fuel cell technology. And one of the (blatantly incorrect) statements is that hydrogen is impossible to store. And yet, there are multiple car manufacturers that make viable hydrogen-powered cars, and the hydrogen storage is not the problem at all. The problem is the current common methods of producing hydrogen, and the (non) availability of gas stations.
I swear that the collective Slashdot IQ falls through the floor when fuel cells, especially hydrogen fuel cells, are the topic. The dumbest, least researched statements, get the most upvotes. It's embarrassing to watch.
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Fuel cells are not all that great either. One of the biggest problems is that they're low power density. And the more power you try to get out of them, the lower their efficiency gets. Plus, aircraft jet engines - when operating at high throttle - are actually pretty efficient to begin with.
A hydrogen fuel cycle - between electrolysis losses and fuel cell losses is much less efficient than an electric cycle. When it comes to cars, usually 1/4 to 1/2 the system efficiency; for aircraft it'd be in the bal
Re:Energy density per kg (Score:5, Insightful)
The engine is the easy part. We already have plenty options for efficient electric engines on any power range you'd like. I recall a group called "Bye Electric" fitting a C172 with a 200hp electric engine with little issues.
Power storage is everything. Every single option to store electric energy onboard an aircraft is orders of magniture less power-density efficient than gas.
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This is a hybrid, it still uses liquid fuel.
TFA doesn't have specifics but it seems that they have a set up similar to diesel electric trains. A liquid fuel combustion engine drives a generator that produces electricity, and that electricity is used to drive electric motors that provide propulsion. The advantage is that you only need one combustion engine and it can be run at the most efficient speed.
You can then add a battery pack so you don't need to run the combustion engine all the time. Great for cutti
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A liquid fuel combustion engine drives a generator that produces electricity, and that electricity is used to drive electric motors that provide propulsion.
In that case, job done. You're basically describing the thermodynamic cycle of a high-bypass turbofan or turboprop engine, minus all the electrical efficiency losses in between. Gas generator driving a turbine which produces mechanical power to drive a bypass fan or prop. And you're misunderstanding the reason why we have multiple engines on passenger aircraft. It isn't because we can't build em large enough. It's because everything fails. That's why you have two of everything in aircraft. Two engines, two
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The fact that a preponderance of people cannot do long-term loss calculation precludes the likelihood Nuclear is an option for you and yours.
Tesla3 (pre)sales estimates alone seem to suggest a couple million less barrels of oil per year... what are we going to be creating the additional electricity with?
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Trust us, it's for your own good.
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A mixture of different electricity generation methods, including a small number of 1970s style nuclear AP1000 units currently planned or under construction. Not having a monoculture means not being held hostage by a single industry with a small number of major players among a range of other benefits, which is one reason why some in the oil industry are pushing hard against windmills and anything else they see as a threat to their influence.
A
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LiPo = 0.95MJ/kg [wikipedia.org]
Re:Energy density per kg (Score:4, Interesting)
Energy density for liquid hydrogen needs to be measure in MJ/L for you to really see why it sucks to use. LH2 is 5.6MJ/L and a LiPo is 2.28 MJ/L.
While batteries are probably a long way from being capable of driving aircraft liquid hydrogen is a non starter because it takes up too much space. Standard Kerosene jet fuel has an energy density of 37MJ/L and has none of the painful storage or explosive risks of hydrogen.
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Re:Energy density per kg (Score:5, Informative)
They are both equally important. Especially in things like aircraft. To carry the amount of energy required the size of the hydrogen tanks would be stupidly large. So large that it you wouldn't have any room for anything else. The 777s cary 181,300 L of fuel, this is 6,708,100 MJ of energy. If you assume the same efficiency for a hydrogen burning engine you will need 1,197,875L of liquid hydrogen fuel.
When you then consider that the 777 is 73.9m long and has a cabin diameter of 5.87m which, if treated as a cylinder is 1,362,000 L you start to see the problem. Even if you assume that all 181k of jet fuel is carried in the wings, you have cut your cabin space down to just 345m3 from the original 1362m3 just to hold the extra fuel volume. And this would be an over estimate as it is based on the plane being a tube.
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Low density is a good thing. You could use the fuel tank's buoyancy to generate lift. Maybe you could do away with wings completely.
I'm amazed that in all humanity, nobody's tried it.
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Ummmmmm. Liquid hydrogen is heavier than air.... So for the purposes of an aircraft it actually makes you fall....
Re:Energy density per kg (Score:4, Funny)
I'm amazed that in all humanity, nobody's tried it.
"Oh, all the humanity!"
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Don't liquefy it then. Do I have to do all the thinking round here?
Re:Energy density per kg (Score:5, Funny)
Don't liquefy it then. Do I have to do all the thinking round here?
Good idea. Let's put all the fuel in a big cigar shaped tank that you carry on top of the plane. By virtue of being so light, it also helps to create extra lift.
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Quite the opposite, but that's okay; the sun and wind are free! Slap some solar panels on the body and a windmill on the nose, and the plane will have all the energy it could ever use, while providing lots of jobs. It will never actually leave the runway, but that is a minor point, right? /s
Many of the "green" ideas are attractive, and superficially plausible to the layman. Ultimately though, reality has the final word, and the numbers just don't work. At a small scale, obscene subsides can partially co
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Re:Energy density per kg (Score:5, Informative)
This was actually tried in the past: both the USA and the ex-USSR experimented with nuclear powered engines. Instead of electric engines they used regular jet engines, with the combustion chamber using heat from the reactor instead of burning fuel. It worked fine, the problem was they were unable to properly shield the crew from the reactor's radiation without adding too much weight.
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Actually what they have managed to do (both the USA and the russians) is to put a working nuclear reactor on a aircrafts using conventional engines - the reactors had nothing to do with moving the aircrafts. After that point, the projects were abandoned because there were too many problems (radiation shielding was a big one).
The cylinder is heavy, not the gas, but where from (Score:3)
Why use liquid hydrogen? Does it have some magical property? Given the weight of the cylinder, it's not a particularly efficient way to store energy, though it may be better than batteries.
At larger sizes, hybrid, multi-stage systems can work. The typical locomotive is a great example. The diesel engine turns a generator which powers the electric motors that propel the train.
Re:The cylinder is heavy, not the gas, but where f (Score:5, Insightful)
Turbine about a third the weight (Score:2)
Two example turbines:
The Lycoming T53, first produced in 1955, produces 1400 horsepower and weighs 688 pounds. So just over 2 horsepower per pound.
The turbines in on the Boeing 777 produce over 8 horsepower per pound.
Electric motors:
The Prius motor produces 0.8 HP per pound.
The Tesla motors are better, but still not as good as a 1950s era turbine, if memory serves.
Not a single data point situation (Score:2)
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Not a single metric situation (Score:2)
Re:Energy density per kg (Score:5, Interesting)
Not at all. Kerosene is a very good fuel.
The problem with methane, or even worse, liquid hydrogen, is that while the energy content per pound is good, the energy content per unit volume it terrible. That means very large fuel tanks, meaning more drag and more airframe mass, which leads you to making the wings bigger, which leads to you needing and even bigger tank, which leads to more drag, etc. Liquid hydrogen is one of the worst fuels imaginable for an airplane.
Liquid hydrogen is only about 4.4 lbs/ cu ft and lerosene is something like 55 lb/cu ft. You simply can't make the airplane big enough.
Re:Energy density per kg (Score:5, Informative)
Run this way, the engines can be optimized for maximum efficiency at just a single RPM (max thrust), instead of having to be optimized across a wide range of RPM. The fuel you save from the higher efficiency of optimizing for a single RPM can more than makes up for the extra weight of the batteries. The point of this project is to figure out what combination of battery size and RPM optimization profile yields the greatest overall fuel savings.
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Re:Energy density per kg (Score:4, Funny)
Not currently (sorry). Maybe that's why they're targeting short haul flights - it's limited by the length of the cable.
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The very best supercapacitors are in the neighbour of 20 Wh/kg. For reference, petrol is 12,300 Wh/kg.
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...making the body of the fuselage one huge supercapicitor with quick charge capabilities.
Aside from the very poor energy density of supercaps, (even when compared with liquid hydrogen), there's also the problem of even minor fuselage damage seriously compromising or destroying your energy source.
CO2 emissions (Score:2)
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If they will reduce CO2 output, it will come at significant cost, significant expense.
Significant expense for consumer is, at the same time, significant revenue to the counter party. Extracting revenues is the main point of all the initiatives.
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If that idea holds, then the extracted revenues may be cause high CO2 output or need high CO2 output for them to be.
E.g. consumer buys a hybrid car, saves 18% CO2 per mile, gets paid by the government for buying the car, drives it 10% more since it's so much "green" and better ; that still results in a 10% CO2 savings at use. But making the car and batteries released twice the CO2 than making the non-hybrid car.
So, the hybrid car is more expensive and worse for the environment.
Other example, Germany runs a
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But making the car and batteries released twice the CO2 than making the non-hybrid car.
Citation required.
In both cases the problem does NOT come from wanting to reduce CO2, rather it's because of PRETENDING to.
Easily solved by taxing CO2 across the board, so that any CO2 used for manufacturing the car is also counted.
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How are they suddenly going to start REDUCING Co2 emissions?
Nuclear fission?
No, wait, that should not have been a question...
Nuclear fission. The answer is nuclear fission.
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Software models don't quite match up to reality in a lot of areas guys. The real world has turbulent flow and other stuff that doesn't model well.
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Good luck convincing the public to support nuclear energy.
At least I'm trying. I bring it up here on Slashdot and on other forums I subscribe to. When politicians call me or knock on my door I ask them about nuclear energy. I've e-mailed politicians, not just the ones I voted for. What have you done?
I'd like to do more but I must still work and go to school.
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Inability to completely solve the problem means we should not even attempt to reduce the scale of the problem? That's your argument? Really?
Yes, quite possibly, yes...
We only have so much money and so many resources. Would they best be put to use reducing the scale of the problem, or planning for and mitigating the problem as it arrives?
It is possible that all the efforts to reduce the core problem will leave us unable to actually deal with it when it arrives.
Imagine that you're on the Titanic. Sure, bailing out water and trying to stop the flooding are all noble goals, but is that the best way to use the time you have left? Had the Captain
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"Imagine that you're on the Titanic."
Seriously, you're going with that analogy?
Ok genius, so we bugger up the climate and are metaphorially all bobbing around in the ocean slowly dying. Do tell us where in your analogy where the rescue ship comes from?
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We only have so much money and so many resources. Would they best be put to use reducing the scale of the problem, or planning for and mitigating the problem as it arrives?
We'll still have to deal with phasing out fossil fuels when they run out, so why not start earlier ? The cost will be less.
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You keep stating this when it's patently false. In fact, in 2015 the EU had its lowest CO2 emissions since 1990.
It might help you to stay abreast of that which you use to condemn. It will help you to avoid situations like this, where you make an argument drenched in drama, based on something you, or someone you trust, made up.
Use the US Navy seawater to jet fuel tech instead (Score:5, Interesting)
The US Navy has been experimenting with the technology that can extract carbon and hydrogen from seawater, connect those elements together in long hydrocarbon chains, with heat and electricity from nuclear fission. They've shown it works. This technology makes aircraft carbon neutral without any modifications to the aircraft itself.
The use of an electric hybrid aircraft would still require hydrocarbon fuels. If that fuel is dug from the ground then it is still adding carbon to the air. I suppose we could combine the two technologies, synthetic hydrocarbons and hybrid planes, but it would still require that we invest in synthetic hydrocarbons.
These electric planes are interesting I suppose but they would not solve the problem like synthesized fuels would.
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Thars fine for the Navy, it lands its planes on carriers to refuel them.
I don't think airline passengers are going to be too happy to do that.
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I'd pay for that experience...
Arresting wire landing in a 737...
Catapult takeoff in a 737...
It'd be far more entertaining than the normal takeoff/landing.
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The P8 is a modified 737, and it does carrier takeoffs and landings.
Hahahah ... no.
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In taking carbon from the ocean and dumping it into the air as CO2, without a corresponding step to move it back to the ocean when used, it is not carbon neutral.
Re:Use the US Navy seawater to jet fuel tech inste (Score:4, Interesting)
And you failed to understand what a Hybrid Electric System is. It's a Combination of Internal Combustion engine with an Electric Drive Motor
A true hybrid allows for power from more than one energy source. An internal combustion engine driving a generator, and the generator driving a motor, is not a hybrid. That would make an electric drive train.
The Fucking Chevy Volt uses such a setup.
No the fucking Chevy Volt has a battery pack and a mechanical transmission. While it might not be able to go in reverse or slow speeds without the electric drive train it is capable of going highway speeds without it. These proposed aircraft do not claim to have a mechanical link from the on board internal combustion engine to the ducted fans. If they did then I might be impressed since that would be an engineering feat.
Locomotives are also Hybrids
Very few trains are true hybrids. Some are capable of using a "third rail" for power, those are hybrids. Even using capacitors or batteries on board would not make them hybrids since all the energy to drive the train comes from the fuel oil.
many of the latest cruise ships are using the same tech
Yes they do, but unless those ships use under water extension cables to power the ship at sea they are still just diesel powered with electric drives.
so why in hell can't you get it through your tiny little mind that Hybrid does not mean Fuel Cells and Batteries.
Because I actually looked up what "hybrid" means.
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Carbon neutral means that they don't add carbon to the atmosphere. Since the carbon they emit comes from the air and is returned to the air after being burned it is carbon neutral. If that is not carbon neutral then bio-fuels are not carbon neutral.
Perhaps you don't understand how the carbon gets in the water, it dissolves in the water from contact with the air.
not going to work (Score:3)
Liquid fuels like kerosene have energy densities on the order of 40-50 MJ/kg, while batteries (of any type available) right now range from 0.5-1.0 MJ/kg.
You simply cannot overcome this large a performance gap if you're talking about these categories of fuels, especially since the weight of fuel dominates the mass of any large / long distance aircraft. We're not talking about a factor of a few here, this is a factor of 100x missing energy density.
Part of the benefit of hybrids in cars, too, is that the idle time they spend can be turned into electric consumption at much lower energy usage than keeping a gas engine spinning. Airplanes spend very little time idling.
Ok, if somehow the on-demand flight services industry takes off (Uber for airplanes, short distance, personal travel), then maybe small battery/hybrid aircraft might be viable, but we will simply not find a battery-chemistry-based improvement on liquid fuels. The compressed energy of millions of years of dinosaurs and plants cannot be beaten, and there's a reason for it...
Re:not going to work (Score:4, Interesting)
Not to mention that the hydrocarbon-fueled aircraft gets lighter and more efficient as it burns fuel, while batteries stay the same weight that they were at takeoff.
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On the other hand, the efficiency of regular aircraft engines vary wildly with altitude. Electric engines don't have that issue.
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Re:not going to work (Score:4, Interesting)
Yeah, but to a much lesser degree. Aircraft engines are usually optimized for a given altitude range - normal piston engines decrease power with altitude. Turbochargers improved on this, but they suffer the same issue. Turbofan engines used on airliners have peak efficiency at cruise altitude but suck when flying low.
In general, air density is the main factor impacting aircraft performance, because it impacts on three separate thing: how the engine runs, how much lift can the wings generate and how much air can a propeller push or a jet can suck. Of those, the first one is by far the most important, as it in it can compensate (to a degree) for the rest.
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But the batteries just need wires and switches to move the power around, where explosive liquid fuel needs fuel tanks, fire suppression systems, redundant electric boost pump and mechanical pumps, valves, cross-feed, filters, drainage, filling connectors, thermometers and heating, bleed-air pressurizing system, and let's not forget the ENGINE, where the fuel is burned, as well as a big start
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Yes. I have been a pilot for almost three decades and I have followed the two interesting improvements: one is diesel aircraft engines, the other is called operating "lean of peak". The diesel engines seemed promising, but it seems that they just fizzled out. Maybe they were just too expensive for the cost savings. The "lean of peak" idea made a lot of sense, but only for aircraft with fuel injection and when the injectors were carefully matched. It's a great idea, but can it help us car users when we chang
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"Lean of peak" is common on modern piston-engine aircrafts; you trade off a little power for a significant fuel economy. John Deakin wrote a fantastic piece [avweb.com] on the subject.
Entire system (Score:2)
It's like the mistake with the all ceramic engine project - fantastic performance on a test rig but as soon as you wanted the thing to move the extra weight of the cooling system exceeded the benefits.
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No question that liquid fuel is more energy dense then batteries. But what is the conversion ratio of that stored energy to thrust. From here, http://www.ipcc.ch/ipccreports... [www.ipcc.ch], I get average efficiency of 30-37%.
If it is 37% though you are down to an effective energy store of 14 MJ/KG. Electric engines can be in the 98%+ efficiency level. So while it is still a huge distance to span it's not as big as the pure fuel density implies.
Also when you compare energy density per litre vs per kg batteries do bet
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I thought the whole point of the efficiency measure was the conversion of stored energy to thrust. If thats not what it's measure what is it?
Re:not going to work (Score:5, Insightful)
I'm sure this is all new information to them.
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Picking the only named engineer in the article (actually the in the Sugarvolt video), Marty Bradley [zoominfo.com] has a PhD in aerospace engineering and a high profile career at one of the worlds best aerospace companies, with a whole bunch of other super smart engineers looking over his shoulder to ensure he doesn't waste company money. He has studied the idea in detail, and thinks it might work. You've read a pop-engineering article, and on that basis you call Dr Bradley an idiot.
It looks like a hard problem. I don't s
Re:not going to work (Score:4)
You nailed it. IDIOTS are pushing this. Void of any comprehension of engineering realities.
Yeah, Siemens and Airbus aerospace engineering teams tend to contain lots of idiots.
Well, either that or slashdot tends to contain lots of arrogant blowhards.
Which is the case here is left as an exercise for the reader.
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Actually: "Compared to advanced piston engine airliners of the 1950s, current jet airliners are only marginally more efficient per passenger-mile." [wikipedia.org]
Fuel cells are more thermodynamically efficient than even the best turbines at converting hydrocarbons into work, and they conveniently happen to output electricity, directly.
Fuel cells are being developed th
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It's about Bypass Ratio Improvement (Score:5, Insightful)
Wow, all the comments on this article have completely missed the point of this. IDIOTS are not pushing this - the concept offers very real efficiency improvements.
The primary constraint in modern jet aircraft efficiency is the propulsive efficiency - turning the mechanical shaft power into forward thrust. This is fundamentally limited by the size of your fan for a given airspeed. If you make the fan swept area a little bit bigger, you can get major improvements in the overall efficiency of the aircraft. This is why newer airplanes always have bigger and bigger engines (787 vs 767, 737NG, A320NEO).
However there are limits to how big you can go. One problem is physically fitting a large diameter engine into existing airframe designs. On the 737NG they had to raise the nose landing gear to accommodate the new engines. There are practical limits to how much you can keep doing this sort of thing without having to create a completely new airframe (the 737 is a 1960s airframe). The other problem with larger fan blades is that the tip speed increases with diameter, which means the fan RPM must reduce to prevent supersonic airflow. This then creates a compromise on the turbine section of the engine. The newest generation of engines are now using gearboxes so that the turbine can run at a higher speed than the fan, which lets them go to larger bypass ratios. The cost, however, is in weight and complexity.
The big benefit that hybrid electric could offer is being able to effectively increase the fan area by distributing fans along the wing. This could create massive efficiency gains, and bring jet aircraft closer to the efficiency of turboprops. Imagine a 737 with two large electric fans next to each other. This could double the swept area on the same fuselage. Further, the concpept could make boundary layer ingestion designs practical, and these also offer big advantages in terms of efficiency for future airframe designs.
This is not about making battery powered aircraft. It is about re-arrangement of the aircraft systems to provide better propulsive efficiency.
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It's actually more like the BMW i3 with range extender. A small, efficient petrol engine generates electricity to recharge the batteries. It's light weight because it's not mechanically coupled to the wheels and no complex gearing is required like in a Prius.
They appear to be planning to have a combustion engine to generate electricity, and a small battery pack to allow that engine to run at a constant, maximum efficient speed. It's a great idea, and entirely feasible.
Re: not going to work (Score:2)
A random Slashdot user with the crudest understanding of a hybrid I've ever read. Electric motors have low end torque, so you don't have to Rev up to get moving and they recover power instead of wasting braking energy as heat.
Alternate applications... (Score:2)
You server OEM types use enough underfill to keep the forced air cooling from lifting the ICs off the logic boards, right?
Sure, why not? (Score:2)
The first time, we built full-size planes, then we built models that look like them. Now, we are building model planes with these:
http://www.hobbyking.com/hobby... [hobbyking.com]
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You think that's noisy? I guess you missed out on the first ones powered by two stroke engines? Or the pulsejets?
In other news.. (Score:5, Funny)
Siemens and Airbus just formed a partnership to develop a 4000 mile long power cord.
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Siemens and Airbus just formed a partnership to develop a 4000 mile long power cord.
Ha rats.....I was hoping they''ll be shooting power laser at it...
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Why bother? Siemens admitted their electric motors for aircraft are unsafe and unsuitable for flights over water [aopa.org].
So you can use it over land only, and you don't need a big extension cord when you can land and charge right up again...
Who said it was battery powered? (Score:4, Interesting)
This sounds a lot like the diesel-electric "hybrids" that power trains. Diesel generators generate electricity to power electric propellers. It makes sense to me... of course I know nothing about this stuff. If my assumption is correct, a nice benefit would be that aircraft could use cheaper fuel rather than jet fuel (which I assume costs more per litre... I think it does, if only because of lower volumes).
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Diesel-electric trains have no batteries and are not hybrids. A hybrid is not the same thing as an electric transmission. Sheesh.
What makes sense to you may not make sense to anyone with a modicum of engineering knowledge.
BTW, diesel fuel is most assuredly NOT cheaper than jet fuel. Jet fuel is just kerosene.
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Diesel-electric trains have no batteries and are not hybrids. A hybrid is not the same thing as an electric transmission. Sheesh.
No, they are hybrids. Their drive system is part ICE, part electric. What they aren't is parallel hybrids, and what they don't have is power storage beyond what it takes to start the diesels. The former will probably never come (why bother) and the latter will only come when all trains adopt active bogeys rather than using dedicated engines in the first place. Such a train might have battery cars specifically for power storage interlaced throughout the load, as well as generator cars. You could cut arbitrar
Ah, how cool :-) (Score:3)
I know - this is about turboprop and that sort of things, but I can't help imagining a jet-engine with an almighty bolt of lightning coming out of the rear end.
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From what i've read, the main issue they had was not safety but (surprise surprise) weight. It took a lot of shielding to protect the crew from the reactor's radiation.