Airbus and Rolls-Royce hit eject on hybrid-electric airliner testbed after E-Fan X project fails to get off the ground

Airbus and Rolls-Royce have ended a joint venture to produce a hybrid-electric airliner testbed that could have paved the way for electric aircraft of the future. Airbus CTO Grazia Vittadini said in a statement late last week that "we need to re-focus all of our efforts on technology 'bricks' that will take us" to a low-CO2- …

[Chris G]

If it doesn't get off the ground

I can see a future in in shipping for a generator like that.

[Holtsmark]

It may be worth noting that the Siemens electric aircraft propulsion unit was aquired by Rolls Royce in October 2019

https://www.rolls-royce.com/media/press-releases/2019/01-10-19-rr-completes-acquisition-of-siemens-electric-and-hybrid-electric-aerospace-propulsion.aspx

This means that Siemens position in the project is irrelevant.

[Tubz]

beer keg, not that big, make a mini version for a vehicle, may be trucks ?

[Vulch]

2.5MW would make a respectable railway locomotive by the look of it.

[Cynic_999]

Engines are not trivially scalable, and in any case a jet engine can have problems in a ground vehicle due to the considerable centrifugal forces of the high speed turbines causing problems when cornering. Although those can be alleviated by mounting it vertically.

[CliveS]

In the UK, for railway use, I would draw your attention to British Rail 18000 and 18100, and to the APT-E, all gas turbine powered and the first completed in 1949. As regards road usage, I'd like to mention the Rover JET1 (1949), Fiat Turbina (1954), Chrysler Turbine Car (1963), Toyota GTV (1987) and Jaguar C-X75 (2010) as examples of gas turbine installations in practical cars.

[Yet Another Anonymous coward]

Or a motorbike

[Cynic_999]

In fact you *make* my point rather than refute it.

There are good reasons why none of the turbine cars you mention were successful, and AFAIAA there is not a single turbine car or locomotive that went into mass production or are available today.

[CliveS]

Please, re-read your own post before being so daft as to claim I *make* your point. I'll help you out:

"Engines are not trivially scalable, and in any case a jet engine can have problems in a ground vehicle due to the considerable centrifugal forces of the high speed turbines causing problems when cornering. Although those can be alleviated by mounting it vertically."

The "considerable" centrifugal forces obviously aren't, as none of the examples mentioned had a) any cornering issues, or b) turbines mounted vertically. Scalability isn't a problem either, as there are plenty of examples of gas turbine applications ranging from the micro-turbines used in the C-X75 through to the larger turbines used in the Rover JET1 and APT-E.

There is an issue, one you completely fail to mention, which is throttle response on gas turbine/mechanical drive systems. It was this that caused issues with the JET1 (for example). The Jaguar C-X75 didn't go in to production as the market for an £800,000 - £1,000,000 million niche supercar was considered non-existent in 2010, less than 2 years after the financial crash.

APT-E worked fine, with the gas turbines driving electrical generators, but was not adopted for production as Leyand stopped manufacture of the turbine it used. An additional concern was that BR have had to maintain a fleet of diesel, electric, and gas turbine powered rolling stock. The same issue that caused BR to eventually scrap diesel-hydraulic locomotives and instead use diesel-electric. In France SNCF operated the Turbotrains, two classes of turbine powered trains that were production models rather than one-off prototypes.

The issues around the widespread adoption of gas turbines comes down to infrastructure and economics. So yes, there were good reasons why none of the vehicles mentioned went in to production. However those reasons had absolutely nothing to do with the points you made.

[Yet Another Anonymous coward]

The APT project's problems were beyond anything to do with the turbine.

I wonder how practical a mass-produced turbine hybrid car engine would be?

A small 50-100Hp turbine with an integrated brushless type generator, so you don't have to make a 20,000rpm gearbox. It could run at a constant speed/load just charging the battery

Safety containment shouldn't be any harder than a turbo. Modern control is trivial (lab turbo molecular pumps run at 100K rpm safely) . They can burn pretty much any fuel and should be hot enough to have very little particle exhaust.

[Anonymous Coward]

I wonder how practical a mass-produced turbine hybrid car engine would be?

A small 50-100Hp turbine with an integrated brushless type generator, so you don't have to make a 20,000rpm gearbox. It could run at a constant speed/load just charging the battery

That was the Jaguar model. Worked, but was a tad pricey.

[Yet Another Anonymous coward]

True but a lot of features debut on ludicrous hyper-cars and are then standard on a hatchback a decade later

[jake]

"True but a lot of features debut on ludicrous hyper-cars and are then standard on a hatchback a decade later"

A bad ride, evil handling, eats tires and brakes, 'orrible controls, uncomfy seating, impossible to work on wiring and drivetrain, bad lighting (inside and out), entirely too noisy/buzzy for long trips, not worth anything near what you paid for it ... You're right! A cheap hatch IS an awful lot like most so-called "hypercars"!

[SImon Hobson]

A small 50-100Hp turbine with an integrated brushless type generator

It wouldn't have to be that big as part of a hybrid with energy storage.

For cruising, the power requirements for most cars would be lower than that - and keeping to a lower output genny while using stored energy (batteries and/or supercaps) for higher requirements would reduce the need for throttling back the genny. That's one of the big issues with gas turbines - they work best at fixed (or only slowly changing) power outputs. Configuring the system such that it ran almost all the time at a set power level would mean it could be carefully optimised (efficiency, emissions) for that.

[itzman]

small gas turbines

are inefficient due to the problems in getting micro scale gas turbines efficient because getting the clearance between turbine blades and the ducting small enough is very very hard

[cheb]

There was also LMS Turbomotive built in 1935.. From what I've read it was successful, but uneconomic to rebuild when it failed in 1949.

[Dr Who]

So ... the shit hit E-Fan then

[John Brown (no body)]

E-Fan Gum. The Yorkshire version.

[Anonymous Coward]

Cost saving

Rolls-Royce is stopping all projects they can, due to the fact no engine maintenance is being sold. They need to save at least £750 million this year and the the “headwind” caused by the Covid-19 outbreak so far was approximately £300 million.

[Phil O'Sophical]

Electric planes?

Can anyone explain why an electric plane would be a good idea? Aircraft are far more sensitive to weight than any other form of travel, so hauling a set of batteries around as dead weight just doesn't seem logical. Not to mention that recharging an aircraft during the typical 2 hour turnaround would be a challenge. Even with a super-small generator as described here, where's the benefit over just using the fuel to feed a turbine engine directly, instead of carrying fuel + generator + engine?

For environmental concerns, I'd have thought that air travel would be a prime target for hydrogen or alcohol fuel, which could be obtained from sustainable sources & consumed in a largely-standard engine (turbo-fan or turbo-prop). Since the journeys are well-known in advance, and they always start and end in places with refuelling infrastructure, the logistics would seem easier.

It's a genuine question, I'm not an aero engineer but I struggle to see the benefits of electrical propulsion beyond the "look how clever my engine is" bragging rights.

[Anonymous Coward]

Re: Electric planes?

They tried hydrogen - it had some drawbacks!

[Anonymous Coward]

Re: Electric planes?

The Hindenberg burned because of the dope-covered fabric, all the hydrogen dissipated upwards and burned off mostly harmlessly. It's certainly safer than crashing with tanks full of JET-A1.

[Giles C]

Re: Electric planes?

Well I would guess that if you can power the planes by electric motors, then if someone comes up with some really efficient solar panels you could be on the way to a free fuel situation.

Thinking about it if the panels are good enough then as long as you are flying in daytime almost zero cost. Flying at night might be a bit trickier....?

[David M]

Re: Electric planes?

Electric batteries are about fifty times the mass of airline fuel for a given amount of energy. Plus the batteries aren't consumed during flight, so the landing mass is the same as at take-off. And solar doesn't help - a panel the size of the aircraft would only produce a tiny fraction of the required energy.

The only realistic way to reduce airline fossil fuel consumption at the moment is to fly a lot less. And we're currently proving that this is perfectly viable.

[batfink]

Re: Electric planes?

Speak for yourself. We split our time between the UK and Aus for family reasons. It's not "perfectly viable" to do this any other way than by air travel, given the limited amount of available holiday time.

[BebopWeBop]

Re: Electric planes?

You are going to have to get that Yachtmaster certificate then!

[Cynic_999]

Re: Electric planes?

"

And we're currently proving that this is perfectly viable.

"

Hmmmm. Do you also believe that we are currently proving that we don't need restaurants, pubs or sporting events? Or that over half the population can stop working altogether? Or that we don't need to treat cancer or many other serious conditions?

Just because something is possible to do for a limited time does not mean that it is either possible or desirable to maintain that situation permanently.

[John Brown (no body)]

Re: Electric planes?

"we are currently proving that we don't need...sporting events?"

I'm not seeing the downside there.

[MiguelC]

Re: Electric planes?

we used to fly people from all over Europe for essential face-to-face meetings

everyone, up to c-levels, is now getting that video conferencing serves us as well as in-person meetings ever did and is a lot more economical

if you add the carbon footprint gains, we're in a win-win-win situation

[Cynic_999]

Re: Electric planes?

"

we used to fly people from all over Europe for essential face-to-face meetings

"

I should think that face-to-face meetings comprise the minority of air passengers. Besides, vidoconferencing is a poor substitute for in-person meetings where you get to converse and bond with other attendees during informal breaks, and swap ad-hoc ideas with individuals.

Making a business proposal or selling an idea is far better done in person than by video call. Would you buy so much as a used car that is being sold only via video call?

Tourists make up not only a very large proportion of air passengers, but are also a huge proportion of the economy of many countries. Going back to the time when the most exotic holiday location most people were likely to see was Blackpool would be feasible - but hardly desirable. And it would be disasterous for many countries.

[Yet Another Anonymous coward]

Re: Electric planes?

Would you still fly 100 people to Atlanta so they can sit in the same room and all watch the same CEO give a Powerpoint about leveraging dynamic synergies?

[JibberJabberBadger]

Re: Electric planes?

I have a feeling we may have worked for the same company - ah, I don't miss the days of flying around Europe every week in business class for a two hour internal meeting and the 6 monthly trips to Atlanta for training and meetings that could have easily been done online - massive waste of money.

[Anonymous Coward]

Re: Electric planes?

I used to fly to the US 3-4 times a year for team meetings and design workshops, plus a few trips around Europe to teams and customers. Our team was known as one of the best in the company, solid despite the geographical separation. We always worked well together, our product sold very well.

Now the penny-pinching beancounters are trying to impose video meetings, I haven't been to the US in several years, and am lucky if I get an annual trip to meet the rest of my European team. It sucks, team co-operation is crap, product quality is falling, and I can't wait to leave.

[Nifty]

Re: Electric planes?

Maybe your C-levels haven't yet discovered the idea of an online discussion forum.

[CAPS LOCK]

Absolutely. And just imagine if your MP spent all his/her time in the constituency instead of...

...the Ivy.

[Intractable Potsherd]

Re: Absolutely. And just imagine if your MP spent all his/her time in the constituency instead of...

Well, that depends on your MP, doesn't it? The feckless lump of lard I've currently got seems to be universally disregarded even by the people who voted for her.

[amanfromMars 1]

Re: Electric planes?

Just because something is possible to do for a limited time does not mean that it is either possible or desirable to maintain that situation permanently. .... Cynic_999

I submit it most certainly is possible whenever both highly desired and desirable. What's not to like for a real long time? I mean ...... come now, don't be fooled again.

Does one have to spell out the attractions and temptations that deliver desire for passions to quench and revitalise, in order that you more clearly see the treasures and pleasures before you with an Alien Being in Strange Charge with Universal Key Strokes in/for Fully Virtually Remote Field Operations.

Tell me that really do know what LOVE is? Are you not already told to be aware of Live Operational Virtual Environments?

You realise what it means if you haven't a clue about everything you have just learned there now. It is withheld and being detained and restrained by other forces ..... for something else.

What would you be minded for such other forces to do ..... in Order that Brotherly and Sisterly Orders Always Succeed and Endlessly Prosper and Grow and Evolve ?

Think Big and Bigger Again and Again is Certainly Better in this Case for in the Midsts of Madness are the Acorns and Apples of Genius Tempting their Way Through All Manner and Matter of Engaging Novelty and Passionate Internet Discourse.

[jake]

Re: Electric planes?

Sorry, amfM ... virtual environments don't feed & exercise the dawgs & horses. Nor do they feed the food (hogs, steers, chickens ... ). Nor do they clean up after all the above. The physical world makes the virtual possible, not vice-versa. One can do without the other quite nicely. And oftenusually does.

(Substitute "children" as appropriate if you don't keep livestock.)

[Cuddles]

Re: Electric planes?

"Do you also believe that we are currently proving that we don't need restaurants, pubs or sporting events?"

Well yes. They may be nice to have available, but there's obviously no actual need fo them to exist. If you can't go out for a meal, you can still very easily avoid dying of starvation. And if you're not able to fly from the UK to Australia, you can very easily simply avoid doing so, no matter how much family might be at the other end.

The difference is that pubs have very little environmental impact compared to eating at home, so there's no reason to worry about them opening back up once this lockdown is over. We absolutely have proven that we don't need them, but we want them and have little reason to oppose that want. Planes, on the other hand, do have some serious downsides to their use. And since we've proven that we don't need them anywhere near as much as some people liked to use them, maybe we should think a bit harder about going back to previous levels of use as soon as we can.

[Intractable Potsherd]

Re: Electric planes?

Once again, the eco-miserabilists speak! How dare we have fun? How dare we do things that aren't "necessary"? Don't you know the planet is DYING!!11! 1 eleventy one?

I have no real doubt that the days when we could fly cheaply and relatively efficiently are over - the economic situation is going to provide far less choice, therefore far less competition, as airlines go bust over the next 12 months or so. However, that is going to be accelerated by governments bending to the eco-twats who think that we should all go back to living where we are born and never travelling further than the nearest market town in the name of "duh env-eye-row-mint".

[ICL1900-G3]

Re: Electric planes?

Thank heaven there's another planet just waiting to be used up.

[Intractable Potsherd]

Re: Electric planes?

This one is fine, and will last for ages.

Look, there are some very good reasons for using less, and reusing and recycling what we have. However, in the developed world, we have the safest, healthiest environment in history, and lots of disposable income (on average). Things my parents (born in the 1930s) could not have imagined for the first 40 years of their lives have become commonplace - all of it made possible by the use of fossil fuels. People who want radical green policies want us to move back to pre-industrial levels, without hope of ever getting out, and they want to do it without engaging in proper, democratic, debate.

The developing world will be left forever behind if they adopt green policies, so the "enlightened" developed countries are enforcing it on them, and the complaining that they never make anything of themselves.

When you can talk in terms of the moral correctness of maintaining (for the developed world) and improving (for the developing world) the standard of living through efficient reuse and recycling, we'll have common ground. Talk to me about "only one planet" and I'll not hear a word you are saying.

[Phil O'Sophical]

Re: Electric planes?

And we're currently proving that this is perfectly viable.

No, we're currently proving that it is very, very painful. I won't get to see my family for months, I've had to cancel vacations.

One of my colleagues has been stuck in another country, unable to get home, for 6 weeks.

We need to develop ways to use sustainable fuels, not to just give up on travel.

[Anonymous Coward]

Re: Electric planes?

Regrettably, I don't get to see the mother in law.

[hoola]

Re: Electric planes?

We need to develop ways of living more sustainably or we are seriously stuffed. Currently sustainable fuels are generally plant based and as such are doing huge amounts of damage to the environment. It is the usual our of sight, out of mind, believe the PR bullshit about reduced CO2 and offset.

We have to travel less and we have to stop using resources at the rate we do. When I was at school (a long time ago) a family going on a trip abroad was a major event. Nowdays people are jetting off all over the place for weekends, half terms, AND their main holiday. Air travel is seen as a right and and it must be cheap, not the luxury it actually is.

[Intractable Potsherd]

Re: Electric planes?

See - hoola proves my earlier point perfectly! God forbid that human progress should make that which was expensive affordable by all!!

[rcxb]

Re: Electric planes?

Electric batteries are about fifty times the mass of airline fuel for a given amount of energy.

This is a nonsense comparison. Lithium-Air batteries have a theoretical specific power of 11.4 kW/kg, compared to the theoretical maximum of 11.99 kWh/kg for Jet A-1, so very close.

We don't have those theoretical Lithium-Air batteries, you may say, but that's fine, because we don't have theoretical engines with 100% conversion efficiency for jet fuel, either. And if we did, they wouldn't be zero mass and zero volume, so would negatively affect those numbers. And that's without mentioning that jet fuel needs things like storage tanks, pumps, which also add mass and volume.

The only realistic way to reduce airline fossil fuel consumption at the moment is to fly a lot less.

Actually, a large number of options to reduce fuel consumption exist. Flying wing designs improve performance by 1/3rd, lower air-speeds propelled by turbo-props instead of turbofans are more fuel efficient, just flying slightly at slightly lower throttle (which some airlines have already done) reduces fuel usage at the expense of slightly longer flight times.

[Holtsmark]

Re: Electric planes?

It must also be noted that the efficiency of a combustion based energy conversion has a maximum efficiency of approximately 35% (diesel ICE), whereas an electric machine operates n the high nineties.

Furthermore, an electric drive-train allows numerous advantages with regards to propulsive integration.

Undesired wake interactions can be avoided. Propeller disk loading can be optimized (yielding higher propeller efficiencies at lower speeds). Boundar layer ingestion and propeller / wingtip vortex interactions can be used to further reduse aerodynamic losses.

Electric drive-trains also lend themselves to high redundancy architectures, which increases safety and allows for what would otherwise be deemed to be "risky" strategies like blown wing designs (NASA), further reducing the required wing area and thus drag.

Finally, maintenance- and operational cost can be significantly reduced with an electric drive-train.

These are all things that are being studied intensely, but which will require a number of key technologies to mature before being widel adapted. And meanwhile, the cumulative effect of a couple of percent's worth of annual improvements in efficiencies for conventional aircraft means that there will be a certain amount of catch-up to do as well.

[Anonymous Coward]

Re: Electric planes?

Lithium-Air batteries have a theoretical specific power of 11.4 kW/kg, compared to the theoretical maximum of 11.99 kWh/kg for Jet A-1, so very close.

But they're still there for the whole flight, unlike the liquid fuel that burns off during the journey.

[Graham Dawson]

Re: Electric planes?

And a theoretical specific energy means little if it isn't practically achievable.

[TrumpSlurp the Troll]

Re: Electric planes?

Another point on power density.

For Lithium Ion batteries is the figure for full power delivery until the battery starts to become nearly fully discharged? That is, can you use all the energy at a constant supply rate until the battery is effectively discharged?

As far as I can see jet fuel retains the power supply characteristics until the tanks are dry.

[rcxb]

Re: Electric planes?

As far as I can see jet fuel retains the power supply characteristics until the tanks are dry.

That's completely wrong. As fuel level goes down, you're spending more energy pumping it to the engines, dealing with vapor, and running risks of stalls due to the fuel not being over the pump inlet while the jet is turning, and there are dangers of inaccurate fuel gauges, etc.

Battery-electric vehicles are vastly superior on that front. Li-Ion batteries do maintain a very, very flat power curve until they are deeply discharged, and engineers prevent deep discharge to extend battery life, anyhow. At the low discharge rates used in vehicles, they are extremely consistent and predictable. I would NEVER consider driving my petrol car down to 5% of a tank of fuel, but with a battery electric car, it's quite safe to do and not uncommon.

[Phil O'Sophical]

Re: Electric planes?

I would NEVER consider driving my petrol car down to 5% of a tank of fuel, but with a battery electric car, it's quite safe to do and not uncommon.

Buit that wasn't the question. You don't get less energy from your petrol when the tank is 10% full than when it's 90% full, but does a battery have the same characteristics?

[jake]

Re: Electric planes?

"I would NEVER consider driving my petrol car down to 5% of a tank of fuel"

I do. All the time. Sometimes much less. 5% of a 20 gallon tank is one gallon, which will get me quite a distance before I need fuel.

[rcxb]

Re: Electric planes?

Buit that wasn't the question.

The "answer" was just before the part you quoted...

"Li-Ion batteries do maintain a very, very flat power curve until they are deeply discharged,"

You don't get less energy from your petrol when the tank is 10% full than when it's 90% full

Actually you do, though really quite minor at that scale.

[rcxb]

Re: Electric planes?

But they're still there for the whole flight, unlike the liquid fuel that burns off during the journey.

Much of the fuel burns off, but the engines, storage tanks, pumps, etc., do not. Jet fuel can be as low as 20% of the overall weight. And the weight is of most concern at take-off, where both types of planes would be fully loaded in any case. This single effect you're focusing on is really just a footnote, for a theoretical jet that doesn't exist with as-yet unknown technology.

[Anonymous Coward]

Re: Electric planes?

Jet fuel can be as low as 20% of the overall weight.

A 787 is 120 tonnes empty, and can carry 180 tonnes of fuel. A 747-800 weighs 220 tonnes empty and can hold 230 tonnes of fuel. It can't land at that weight.

the weight is of most concern at take-of

Landing is also a concern, a 747 can't land with full fuel tanks, it has to dump 100+ tonnes from a full load if it needs to land soon after a maximum-weight takeoff.

[rcxb]

Re: Electric planes?

A 787 is 120 tonnes empty, and can carry 180 tonnes of fuel.

That may be true, but it's useless (and impossible) to fly an empty aircraft. Throw in the crew, passengers, baggage, or other cargo, and the fuel isn't such a large percentage. Plus, a significant fraction of the fuel is maintained as reserve capacity, which would be much less necessary without the vagaries of liquid fuels.

See: https://commons.wikimedia.org/wiki/File:Takeoff_weight_diagram.svg

[Graham Dawson]

Re: Electric planes?

"but it's useless (and impossible) to fly an empty aircraft."

Now I know you're talking out of your backside. Aircraft are routinely flown empty to reposition for route changes, for testing, for maintenance stops, and to maintain flight slots.

And that diagram shows loaded fuel being more than a third of the weight of a fully laden craft, not that it's much use without numbers.

I suspect you have no idea what your talking about.

[Graham Dawson]

Re: Electric planes?

Of course, on rereading, you were talking about flying a plane without fuel, which is a stupid argument on its face. Of course a plane can't fly without fuel. Fuel is a necessary part of the plane, but flight distances (and reserve fuel) are calculated on the back of the mass reduction from fuel expenditure. Fuel is a significant proportion of the mass of a fully laden plane, as yoir own otherwise meaningless diagram attests, but that mass is expectex to reduce over the course of the flight, extending its range significantly.

Battery mass doesn't reduce as its energy is extracted, reducing the effective range of the plane as it has to continue to haul dead weight. This isn't a theoretical exercise either; this is well understood physics. Even with your mythical super batteries with their theoretical specific energy and a mass comparable to kerosene, an electric and will not have the same range as a comparable jet turbine plane, entirely because of that battery mass - a good third of the entire mass of the plane - remaining in place.

That remaining mass of empty batteries also means the cargo capacity has to be reduced, so that the plane can land safely, so on top of the reduced range, you have reduced carrying capacity.

Electric planes aren't viable. Simple as that.

[rcxb]

Re: Electric planes?

Aircraft are routinely flown empty to reposition for route changes

Very difficult to fly a plane with zero fuel.

I suspect you have no idea what your talking about.

I'm the one supplying numbers and linking info. What you're accusing me of actually applies to everyone else but.

[jake]

Re: Electric planes?

Note how rcxb conveniently ignored the follow-up post Graham made some 9 hours prior to rcxb's latest missive. One wonders if he somehow thinks that'll make his side of the argument "more right"?

[Colintd]

Re: Electric planes?

Are you sure your data is correct?

https://en.wikipedia.org/wiki/Energy_density (and other references) suggests Jet 1A has a specific energy density of around 43MJ/Kg whereas Lithium ion batteries are between 0.4 and 0.9 MJ/Kg... That is between 50-100 times worse.

Even lithium-air is only 9MJ/Kg, so 5 times worse, and they are unproven technology.

In addition, as a number of others have noted, fuel is burnt so not present at landing. For batteries this is not the case.

[vtcodger]

Re: Electric planes?

... solar panels ...

Max theoretical output about 1 kwh per square meter. In the tropics. At noon. On a cloudless day. Using far more efficient panels than we can make today.

Might be feasible on a 21st century zeppelin. On a conventional fixed wing airliner, probably not.

Maybe our great, great, ever so great, grandkids will indeed travel the world in gas filled bags propelled by solar electricity. But I doubt the groundspeed for lighter than air transport will ever be what air travelers today experience. Trains, however, may eventually go as fast as today's planes. Maybe faster. But probably not from Los Angeles to Sydney.

[Snapshot]

Re: Electric planes?

I haven't looked into the benefits of converting fuel to electricity on-board but they must be real as diesel-electric trains replaced diesel a good while ago and shipping is also doing the same.

[BenM 29]

Re: Electric planes?

" diesel-electric trains replaced diesel a good while ago"

Indeed they did - back in the 1920s, however that was largely due to the great benefits of using an electric motor that can be co-mounted with the driving wheels rather than having to somehow transmit vast numbers of HP down to the wheels through a transmission that had to fit in quite a restricted space.

Nealry all Modern (post 1930) "Diesel" locomotives (Sprinters/Pacers and the like excepted cos they are just busses IIRC without bogies) are Diesel-Electrics.

The use case for electric fans on a plane is rather more obscure - and I can't pretend that I know what it is or even may be!

[Cynic_999]

Re: Electric planes?

"

The use case for electric fans on a plane is rather more obscure

"

There are certainly advantages in mounting the heavy part of the power train in the fueselage rather than on the wings, and separating the power generator from the thrust convertor. Whether the advantages outweigh the disadvantages is a matter for the engineers to assess.

[John Brown (no body)]

Re: Electric planes?

Also not an [aero]engineer, but I wonder if it's more of a pollution/exhaust thing? Put the power generation inside the fuselage and drive the exhaust through filters/catalytic converters/whatever, which slows the exhaust down significantly, not something you can do when the exhaust is your motive force in traditional jet engines/turbofans.

[Phil O'Sophical]

Re: Electric planes?

exhaust is your motive force in traditional jet engines/turbofans.

AFAIK the jet exhaust is only a very small part of the thrust in a modern high-bypass engine.

[jake]

Re: Electric planes?

Yeahbut ... Remember this bit: "the generator – about the same size as a beer keg – but producing a staggering 2.5MW."

What kind of noise does it produce? How much sound insulation will be required to put it into the fuselage and yet still allow the passengers to hear each other scream? What kind of mass are we talking about? How much space will it take up (in paying customer ass-units[0])?

[0] If you're a resident of a small island off the coast of Yurp and incapable of translating for insular and/or holier-than-thou reasons, feel free to substitute "arse-units". The conversion factor is 1:1, even in teh metrics. You are quite welcome.

[Anonymous Coward]

Conversion factor

I'd have thought the conversion factor for US ass-units to European metric arse-units would be about 1.8:1

>;-)

[hoola]

Re: Electric planes?

The electric fan used the same technology principals as an modern jet. This is where the burning jet fuel spins the shaft. This in turn drives the fan that pushes vast amounts of cold air through some very clever cones to provide the thrust. The jet fuel spinning the shaft is replaced with an electric motor.

As a principal it is great, it is just sorting out all the relative power delivery. This is where there generator will have come into the solution. I suspect that batteries simply cannot deliver the power required to drive the motor. It is not about the energy density of the batteries but how quickly you can get the power out without destroying them. This is where jet fuel (and ICE) have the advantage, you just keep making it bigger and as long as the pipe supplying the fuel is fat enough, power delivery is maintained. Obviously there are other constraints but it is not in the delivery of fuel to the engine.

[Anonymous Coward]

Re: Electric planes?

Diesel-electric trains have been around for a while, and they make sense because of the engineering benefits of:-

A: being able to keep the diesel engine running at the most efficient speed whilst moving the train at a range of velocities

B: regenerative braking: there's a lot of energy in a moving train

C: distributed power to the wheels:- You can power as many axles you want on a train allowing a better use of traction.

D: If you design the train right, you can swap between diesel electric and pure electric running, making use of the better power conversion efficiency of a static power plant when overhead cables are available.

Diesel electric ships have been a thing for a long time. There are two benefits that I can think of from the top of my head:-

1. Power redundacy; Useful on a ship going to remote locations, where you can have "spare" diesel generators in case of failures. (e.g. icebreakers)

2. Mass distribution: You aren't constrained to straight lines from the propellor locations to where you can position the ships engines.

With regard to electric aeroplanes, given the efficiency of a large, modern, turbofan engine, I can't see how a generator or fuel cell and electric motor combination can beat that. In fact, I can't see how any engineer could seriously consider an electric aircraft for long distance freight or passenger transport without some magic breakthrough in battery energy density or a breakthrough in materials science that allows really lightweight high pressure hydrogen storage.

[Anonymous Coward]

Re: Electric planes?

> Diesel-electric trains have been around for a while, and they make sense because of the engineering benefits of:-

I thought the main advantage was the torque characteristics of the electric motor and the way that gearboxes break with the sort of loading that trains have.

[Richard 12]

Re: Electric planes?

Diesel-electric ships have some other pretty big benefits:

3. The engine can run at its maximum efficiency for the desired power output at all times, regardless of the needed propeller RPM

4. The thrusters can use the same generator

5. You can have "Azi-pods", which mean you don't need a rudder or thrusters at the aft of the ship.

On an aircraft, (3) is still an advantage, though I don't think fan RPM varies very much.

[werdsmith]

Re: Electric planes?

Also, military vessels can operate stealthily below the surface without needing to emit exhaust gas.

[Phil O'Sophical]

Re: Electric planes?

No visible chemtrails!!

[rcxb]

Re: Electric planes?

A: being able to keep the diesel engine running at the most efficient speed whilst moving the train at a range of velocities

No. Locomotives don't have a huge bank of batteries. The engine has to throttle up and down as power needs vary, as it would with a mechanical transmission. Although in the case of multiple locomotives you can turn some of the engines on and off as needed to try and improve fuel efficiency to a small degree.

B: regenerative braking: there's a lot of energy in a moving train

No. Again, diesel electric trains do not have a huge bank of batteries to dump that energy into. Regenerative braking only works for electrical grid-connected electric trains, while it's a benefit there, it has nothing to do with why trains became diesel electic.

[Neil Barnes]

Re: Electric planes?

I suspect, from talking to a few commercial pilot friends, that you'd get a significant fuel saving simply by putting electric motors in the wheels; it seems that a significant portion of the fuel load is burned simply getting from the terminal to the end of the runway. Jet engines aren't terribly efficient at low speeds, it seems.

[Cynic_999]

Re: Electric planes?

It was tried, and there were several reasons why it did not work. Nowadays we have electric tugs that can pull the largest airliner. If it was economically viable, tugs could be used to take the aircraft right onto the runway instead of burning fuel taxying.

[A.P. Veening]

Re: Electric planes?

If it was economically viable, tugs could be used to take the aircraft right onto the runway instead of burning fuel taxying.

Schiphol (Amsterdam Airport) is currently testing exactly that and the first results seem promising.

[Yet Another Anonymous coward]

Re: Electric planes?

It's economic when oil prices are high but abandoned as soon as oil prices drop.

Main problem is that you can't tow at very high speeds (tugs would be massive and you would have to strengthen front landing gear) so it really slows down your airport operations.

Unless you can guarantee such tugs are available at all airports that the aircraft type would ever serve you still need the engines to be able to run in taxi state so don't gain as much

[A.P. Veening]

Re: Electric planes?

You don't need to tow the planes at take-off speeds and taxi speeds are typically 30 to 35 km/h, that taxibot will tow at 22 knots, about 50 km/h.

See also this with a short movie (Dutch, subtitled in English).

[Yet Another Anonymous coward]

Re: Electric planes?

Virgin tested this at Heathrow as a green program.

It wasn't capable of towing at anything like taxi speed (max 30knts for the 737, 25knts for a 747).

IIRC it was abandoned because it was limited to little more than walking pace, a combination of a safety requirement (eg. stopping distance) and nose gear strength.

It would make a lot of sense from noise, cost, pollution, safety etc - but I suspect it's one of those things where the aircraft makers, airlines, airports, aviation authorities all have to align to enable the changes.

[Chris G]

Re: Electric planes?

As far as I know, all aircraft are designed to be manoeuvred by tugs, I suspect there is a relatively standard nose oleo design to accommodate this. I worked on light aircraft in the seventies and used to earn extra money at weekends pulling and taxiing aircraft in and out of the gangars and parking and orpping them for owners. The different models of which there were many only needed a few adapters for the hand operated tug to connect to them, the tug had a 5HP Honda mower engine. That would pull. Cessna Golden Eagle with ease at about 2MPH.

[Yet Another Anonymous coward]

Re: Electric planes?

Aircraft are designed to be moved by tugs very slowly and carefully

If you wanted to tow a fully loaded and fuelled 747 at 30mph you would need a much stronger towing point - especially if you wanted the ability to stop quickly. F=ma is a bugger.

You would probably also need an interface to allow the tug to control the brakes on the main gear

So the airline would have to pay for heavier nose gear and carry the weight on every flight for the benefit of the airport. So unless a major continent made this mandatory at all airports you have a catch-22.

[chris 143]

Re: Electric planes?

I think the idea is that if they could run it on electricity then they'd have the option of alternative fuel options.

Also not being left behind if someone does develop a good fuel cell/battery/nuclear fusion/fusion energy source, maybe there's some efficiency to an internal generator, but I doubt it was ever the objective, just good enough for powering the test engine

[maffski]

Re: Electric planes?

You need far more power for take off and landing than during cruise.

So much so that cruise is less efficient than it could be, if you could use a couple of smaller jets and then add in electric fans for extra power when you need it you could improve fuel economy by a couple of percent.

NASA are trying another approach, using a smaller wing which is fine for cruise but then adding electric fans to increase the airspeed over the wing during take off and landing to gain the extra lift required. - https://www.nasa.gov/specials/X57/index.html

[jake]

Re: Electric planes?

"You need far more power for take off and landing than during cruise."

Steam catapult for take-off and a tail hook for the landings. It's a tried and true technology that actually works. Lots of retired 35ish year olds with the requisite skill-set out there, too.

A not insignificant side affect is reclamation of all that newly unneeded runway space nearish to city centers that could be used to house the homeless.

[batfink]

Re: Electric planes?

Maffski's idea of adding a couple of small jet engines (or maybe disposable rocket engines) just for take-off is one that should be tested. I propose that we could call this "jet-assisted take-off", or JATO for short.

[Cynic_999]

Re: Electric planes?

As I understand it, the electric motors would not be powered from rechargeable batteries, but by a fossil fuel engine & generator. There are some advantages in doing it that way despite the power loss in the double conversion.

Quite a few ships are nowadays driven by electric motors & fuel-oil powered generators. Electric "azipods" remove the need to put propellor shafts through the hull (which inevitably has at least some water leakage), the heavy engine can be positioned in the best place for C of G rather than needing to be placed where the geometry allows them to drive the propellors, and having azipods that are able to rotate through 360 degrees gives the ship far better manoevourability. Other advantages are: Instant response to engine commands. Servicing & repair is far easier. The main engines can also serve to supply the ship's electrical needs, so separate generators are not required. In the event of an engine failure, both props can still be driven (at reduced power) so you don't have asymmetric thrust.

[Anonymous Coward]

Re: Electric planes?

> Can anyone explain why an electric plane would be a good idea?

That was my first thought too, but then I thought it's possible that some different way of thinking might come from such a project.

The only one my non-aerospace-engineer brain could think of is to reduce necessary onboard power, along with associated weight etc, for the critical take-off phase of flight. Most of the flight is spent in cruise mode, with far less power being required, so if this can be supplied from a new design of generator, while the extra power required for take-off could be supplied by supplementary power, eg batteries, maybe that's worth exploring.

Just a thought, and may be far off, of course.

[Phil O'Sophical]

Re: Electric planes?

Making it effectively a hybrid? Yes, I could see how that could be viable without needing large heavy batteries. Thanks.

[SImon Hobson]

Re: Electric planes?

... reduce necessary onboard power, along with associated weight etc, for the critical take-off phase of flight

I have an idea for that, somewhat tongue in cheek ...

You have a socket at the end of the runway, and a cable about the length of the runway. You plug in the plane, it takes off using (in addition to it's own power) power from the grid for that energy sapping "accelerate a couple of hundred tons of stuff up to flying speed" bit, then the plug pulls out and the cable is wound back in ready for the next plane.

Actually I'm not alone in having had a similar energy saving idea some years ago, but I think all the manufacturers rejected it on the basis that they couldn't get elastic bands big enough.

OK, I'll get my coat.

[deive]

Re: Electric planes?

Smaller buffer battery with multiple hydrogen fuel cells?

[Anonymous Coward]

Re: Satelite designers missed a trick

I'd prefer a small nuclear power cell.

[Marcelo Rodrigues]

Re: Electric planes?

"It's a genuine question, I'm not an aero engineer but I struggle to see the benefits of electrical propulsion beyond the "look how clever my engine is" bragging rights."

There is ONE thing in which that a theoretical electric plane would be superior than a normal one: noise.

One big problem to airports is the noise of the planes. A quieter plane could operate closer to the city - or with far less restrictions.

[A.P. Veening]

Re: Electric planes?

A quieter plane could operate closer to the city

Just check the location of London City Airport ;)

map

[Yet Another Anonymous coward]

Re: Electric planes?

>"It's a genuine question, I'm not an aero engineer but I struggle to see the benefits of electrical propulsion beyond the "look how clever my engine is" bragging rights."

For super small private planes it might be worthwhile. ie a Piper Telsa. Mainly if you can reduce the service costs over a regular engine.

I strongly suspect this project is a combination of Greenwashing and a way for RR to score some Eco grants/tax-credits to do R&D for their small turbine on-site generator business.

If you can have 2.5MW on a pallet, compared to their current container size powerplant then a lot of on-site diesels could be replaced.

[jake]

Re: Electric planes?

"a Piper Telsa"

This pilot says no. You couldn't pay me enough. Civilian aircraft are NOT haberdashery for the idle, clueless, wealthy set. Not primarily, anyway ...

[werdsmith]

Re: Electric planes?

If a plane is going to chuck a lot of gas out the back, enough gas to third law forward fast enough to get it into the sky, then it’s going to make a racket regardless of how you rotate the fans.

[cb7]

Re: Electric planes?

As well as reduced noise (hopefully), if the electrics are used only during take off and landing, you also gain the benefit of lower emissions in densely populated areas.

That gets rid of two of the main objections to airport expansion in densely populated areas. And most of the world's airports are in urban neighbourhoods.

And even if its a small reduction in emissions overall, it's a good stop gap measure until we can go fully electric.

[Fenton]

Re: Electric planes?

Weight problem aside you can increase efficiency quite a bit by having a central engine charging a small amount of batteries which power electric motors. The problem with gas turbines is they are very efficient at constant load (e.g. cruise), but quite fuel hungry at full boost (take off/Landing) also they don't respond. that quickly to changes in speed.

Whereas an electric motor responds very quickly to speed changes and if you have enough battery power (generated during cruise or charged on the ground) for the high thrust parts of the flight envelope you can increase efficiency quite a bit.

Needs a new generation of solid state batteries to work properly in an aircraft setting mind.

[MJI]

Re: Electric planes?

Use say super capacitors for a power boost for take off.

I do like the BAe146s and I blame getting rid of them for the downfall of Jersey European -> British Eurppean -> whatever they were called when went under.

They are a little hot rod of an airliner.

[Anonymous Coward]

Re: Electric planes?

I saw some of their flight testing, it is a lovely plane.

[Yet Another Anonymous coward]

Re: Electric planes?

If you have passengers that can breathe engine exhaust

[EBG]

why ?

Because decarbonisation. Thinking ends there.

Seriously. These things are pure PR. The total project costs are small compared with total corporate profits. No major corporate can not be seen to be behind governments' policies on climate change, irrespective of the hassle from the eco-activists. We must do something.

[Klimt's Beast Would]

Project shafted.

Can you dig it?

[amanfromMars 1]

Starting Off with a Novel Instant Economy ... Vorsprung durch AI Technik does IT Proud and Loud :-)

Do Rolls Royce do Cyber? For the Exercising and Exporting of Virtual Excellence with Future Provenance in Novel Powerful Mediated Currents Delivering Presents for Live Production Facilities and Utilities to Realise ....... and share of course quite widely to ensure that the information and intelligence is disenabled to be misplaced or foolishly misspent and abused/misused.

Can you imagine the Titanic Teutonic Precision such an AI Provision would Supply to BIOS [Basic Input/Output Systems] in CHAOS [Clouds Hosting Advanced Operating Systems]

Methinks exemplary is just and suitably understating.

And that question can equally well be seriously asked of Rolls Royce Motor Cars and BMW ..... for you surely cannot believe an Advanced Automobile Industry is not into Engineering Future Loads with Virtual Vehicles to take you practically immediately to wherever you need or have paid to go to.

And as Surprisingly Sophisticated Virtual AIMachinery, Always Something of a Pleasant Mystery to Enjoy and Employ rather than Export and Exploit, which is quite totally different and for others in that very particular and peculiar frame of mind.

[jake]

Re: Starting Off with a Novel Instant Economy ... ::snippage to fit the Re: size restriction[0]::

"BIOS [Basic Input/Output Systems] in CHAOS [Clouds Hosting Advanced Operating Systems]"

Just to translate for anyone who doesn't speak Martian, that's SNA (Systems Network Architecture). IBM has made a whole pile of loot from it over the years. However, it's mostly depreciated now, and the world has moved on ... with the exception of Marketards selling the Sheeple on an obese, pale, overly complex, ugly johnny-come-lately variation on the theme, which for some reason seems to be much loved by Our Favorite Martian.

Perhaps Mars is stuck in the mid-late '70s?

{0} Hey, amfM ... that the TitleSubject up there, not the body of the text!

[Boothy]

Standard engines + fuel vs fuel + gas turbine + electric?

I'd be curious to know what differences there would be between things like weight and fuel consumption, between using standard engines burning 'jet' fuel directly, and a gas turbine (or two, one under each wing?) burning (perhaps cheaper) fuel, to generate electricity + electric motors?

Add a few batteries and/or super caps to the mix, to boost take off power/store excess energy, so you could have a smaller turbine (although the added battery weight might off-set any savings in using a smaller lighter turbines anyway?).

If using batteries (or some other suitable storage method?) you could use stored power for take off and landings (quieter and cleaner for the locals), and then only use the gas turbine/s once at altitude.

Might not be as efficient as a traditional jet due to extra weight etc, which also means it likely wouldn't have the range, but I could see this being useful for short haul flights, especially into city airports, or environmental hot-spots.

Or perhaps just not viable at all?

[Yet Another Anonymous coward]

Re: Standard engines + fuel vs fuel + gas turbine + electric?

Unfortunately you need the other way around. Big noisy jet engines on maximum power (and afterburner ;-) on take off and minimum engines at cruise altitude.

[Boothy]

Re: Standard engines + fuel vs fuel + gas turbine + electric?

Quote: "Unfortunately you need the other way around. Big noisy jet engines on maximum power (and afterburner ;-) on take off and minimum engines at cruise altitude."

Not sure I understand? Or perhaps you've misunderstood me?

We already know electric aircraft can take off, even with heavy batteries, as these aircraft already exist, (many still early prototype, but there are flying examples already) so the 'Big noisy jet engines on maximum power...' isn't really relevant.

I'm comparing standard existing aircraft, i.e. The 'Standard engines + fuel' bit. i.e. a normal current commercial aircraft.

against an electric only aircraft, but using a gas turbine to generate the power rather than a battery, i.e. 'fuel + gas turbine + electric'.

Also worth mentioning, this would almost certainly be competing against short to medium haul turbo-prop aircraft, rather than jet aircraft, at least till the tech matured a lot.

The main issue with existing electric aircraft is their lack of range, (heavy batteries + not much actual stored energy as compared with liquid fuel). Plus having to then wait to recharge the batteries after a flight.

Burning fuel* to produce the electricity removes, or at least reduces the need for batteries (might still be useful for take off and landing to keep noise down, and/or give a boost to available power), and you've still got the high potential energy stored in the fuel that drives the turbine, more range needed, just add more fuel.

* Obviously this also need the fuel to be 'clean', i.e. made from crops or something. But that should be easier to do for turbine fuel, than for jet fuel (turbines can be run from almost any fuel, so you'd pick something suitable for the use case in hand).

My question, is basically is this feasible, from a physics/engineering standpoint? i.e. Would having fuel + turbine + generator + electric engine, still be too heavy to be efficient?

Even if this wasn't as efficient as a turbo-prop (or jet), it might still be viable if it wasn't too far off, simply to help keep local noise and emissions in check, as rules around these things are almost certainly going to get stricter over time.

PS: I didn't down vote you.

[Yet Another Anonymous coward]

Re: Standard engines + fuel vs fuel + gas turbine + electric?

Sorry was reading an earlier post where they said we could use the little electric engine on the ground to be quiet and only switch to the massive powerful jet in cruise

[Anonymous Coward]

Ideal, a keg-sized 2.5MW generator

for a Rolls-Royce compact nuclear power unit scheduled for a street corner near you soon.

[Anonymous Coward]

Electric planes do not need batteries - Ammonia may be better

Ammonia in a fuel cell is efficient and no doubt with extra engineering even more.

It has zero pollution if made from renewables. This will soon be cost competitive too in places like Australia.

Ammonia has similar bang per buck as current jet fuel but unfortunately requires double the volume. This disadvantage is offset by the greater efficiency.

It is a well known liquid and while needing careful handling so does jet fuel.

Elelctric planes are quieter, less complex (cheaper, more reliable, easier to maintain) and more powerful meaning runways can handle considerably more takeoffs at higher angles minimising disturbance.

My main irritation with current electric engines is they lack elegance. Having 8 or so propellers just does not seem the future.

[jake]

Re: Electric planes do not need batteries - Ammonia may be better

"It is a well known liquid and while needing careful handling so does jet fuel."

Only problem is that spilling 100 gallons of jet fuel would annoy the greenaholics ... but spilling 100 gallons of ammonia could conceivably kill many of them and permanently damage many more for life.

[Intractable Potsherd]

Re: Electric planes do not need batteries - Ammonia may be better

But, a bit like bears, an annoyed greenaholic is much more dangerous than a dead one... - - - >

[Anonymous Coward]

Lithium has issues too.

The key thing is that Airports have stringent safety handling than the farmers who currently may handle ammonia.

Would not want joe public filling up their cars with Ammonia at self service stations.

[jake]

Re: Lithium has issues too.

As a farmer and pilot, I can assure you the safety standards for handling ammonia here at the Ranch are a hell of a lot more stringent than handling fuel at any given airport.

[Cliff Thorburn]

What's not to like for a real long time?

If I had a promissory note for every time i’ve heard that, I wouldn’t need to utilise prime prior art in pirate prime intellectual property to hit the launch button on hyper neuklear intellectual alien intellectual property tied and defied in Live Operational Virtual Environments, part V ....

More sagas than Star Wars, more great gaming than Sega’s, more frustrating than frustration, more costly than pandemics, and more secretive than the da vinci code :0)

[jake]

C'mon, dude, the da vinci code ain't a secret. People have been selling works of fiction for thousands of years because (here's the secret!) People, as a whole, are credulous idiots.

Please, do no harm with this knowledge Grasshopper.

[Updraft102]

"Although the BAe-146 can fly on three of its four conventional jet engines, Cranfield's runway isn't long enough to do that safely."

How long would the runway have to be for it to fly on three engines?

I was not aware runways could fly on any number of engines.

[opalideas]

Plaintively waving

As a pilot, I have been following this development from the other side of the centre-of-the-universe: https://www.harbourair.com/harbour-air-and-magnix-announce-successful-flight-of-worlds-first-commercial-electric-airplane/

Sadly, covid-19 will likely set back the schedule somewhat.

[TrumpSlurp the Troll]

Extra drag?

I'm struggling a bit with the proposal for extra power on take off and landing.

How is that electrical power delivered?

Having an electric motor built into the shaft of the turbine might give increased fan speed at crucial moments, I suppose.

Otherwise you would seem to need extra propulsion units on the wing which would supply extra drag for the whole flight.

Just looking at hybrid cars as far as I know you don't have an electric engine to make the main engine spin faster, you deliver the extra power through wheel motors. So how does that map onto power delivery from wing mounted devices?