OT All electric fighter plane.

So feasible then.

I have passed the Queen's house.

No, it's really quite simple: you are thick as s*it in the neck of a bottle.

This presupposes that he *is* out of nappies.

Have you been living with the limits of electric flight as well then, Timmy ?

Have you been as badly affected as Turnip, by your ordeal ?

michael adams

...

Most short-haul flights will be further than that and you need to allow for diversion to a more distant airport. Plus there is the turnaround time. Many short haul flights are unloaded and reloaded and away again very quickly - how long will an electric plane take to fully recharge?

I'm sure they will become viable, but not for some time.

SteveW

don't have the energy density.

Engineer not in non plane company says energy in the battery would need to be 10 times. Has no job to lose, so trust him

Not commercially.

Like electric milk floats, electric aircraft have a niche market, but unless the batteries can get ten times better they cant compete on any commercial route.

You are ware of the need to have several alternate destinations and an excess of fuel on any passenger carrying flight? No. Thought not.

Actually most of the LI-ion batteries I use are easily rechargeable in an hour or so, given the right charger. You can push it more than that but they get hot and each charge damages them.

Its more an issue with cars, than planes. One would expect an airport to have a high power substation and plenty of juice to recharge a plane since it doesn't have to be duplicated up and down the road network

Work is being done to reduce charge times: for cars 5 minutes might be possible - this is an area where development can and will produce results.

I've seem peak discharge currents go from 'don't flatten this battery faster than 10 minutes' to 'don't flatten this battery in less than 2 minutes'

That's what's enabled the car jump start packs. Massive peak discharge rates.

Its all tantalizingly close, but the problem is that even if you go to lithium air which is a fair bit better than lithium graphene, which is better than lithium with aluminium electrodes, its still really not where it needs to be for aircraft, although cars will get better and better and I suspect that a decent BEV with about 400 miles range will be here in a few years.

It's close, but no cigar....Of course being that close makes it a huge opportunity for con men to pretend to be doing research to get to point X when they know damn well the physics says they will only get to X/3.

Not without some major breakthrough.

Energy density is the one crucial issue. It ain't there yet, not even in the lab. Let alone packaged and safe.

You never read, or understood, the Youtube vids I gave.

After a quick read the Griffon engined Spitfire was pretty useless in combat. It's purpose was maritime use and was used for chasing V1s. Not many of the Griffins were made in WW2. Most went on to power the Shackleton.

I'm not sure if charging time would be an issue. I would have thought a replaceable battery pack would be a neater solution. Charging wouldn't be hurried leading to improved battery reliability.

I don't know how much room there is for improvement for a 'safe' battery.

At the end of the first vid it said that the Samsung graphene battery had achieved a 30% increase in energy density over Li-ion. Great for smart phones, but what is needed is a 1000% increase before they become a major player in long-distance transport.

That *would* be novel.

Not really. The biggest use of power is in the climb. Getting to rotate speed is a fairly small part of the whole. Also, it would limit the aircraft to flying in and out of suitably equipped airports.

Apart from the lack of emissions, which is what is driving the aircraft industry that way.

Although the power required to maintain level flight is a lot less than that required to take off and climb.

I did,

You haven't read or understood ANYTHING I have written. You didn't even understand the videos you linked to.

Graphene is a lighter replacement for aluminium in LI-ion cells. It is an incremental advance in LI-Ion technology, but not enough to replace an airbus.

It might in ten years give us a 600 mile car battery though.

There is no doubt that electric cars in cities are here to stay - the on the street reduction in pollution from exhausts and from brake dust, and a range enough for urban travel is a good driver. Transferring the pollution to power stations that are better able to deal with it is also good, and if nuclear power is used, even better., However the same fundamental energy density problem affects cars as well as planes. Batteries are too heavy for the energy in them. And whilst this is getting better, there is a theoretical limit to how good it can get with lithium based electrolytes, and there are no BETTER electrolytes than lithium.

Lithium sits in the sweet spot in the periodic table. If we are talking chemical batteries then lithium is the *only possible* electrolyte. Juts as Uranium and thorium are the only possible fuels for fission reactors!

Lithium air batteries *in theory* might just be able to fly a transatlantic plane, Lithium Graphene never can, but they could drive a

What I am saying - mostly for John's benefit - is that where we are is as good as it gets right now, and whilst there are small improvements in sight, that may see a lot of light planes and even a very short haul electric plane in use, the dream of a fee paying load carrying transatlantic electric jumbo is a pipe dream.

There is a common misconception amongst people who avidly consume the outpourings of technical and pseudo technical marketing, that anything can be achieved with technology of you throw enough money at it. This is a dangerously false assumption. In reality there are very very few things that can be achieved by technology. And of those there are even fewer that are actually worth achieving.

And chemistry and physics, to an engineer, do not help him achieve those targets but they do absolutely and irrevocably show him what targets

Teh chemistry and physics of chemical batteries show that normal technology batteries cannot fly a plane across the Atlantic. They show that only very nearly perfect lithium air batteries *might* if they could be developed to be within about 70% of the theoretical optimum, do that job.

Not super capacitors, not graphene lithium batteries, lithium air. Why is energy density so important? why cant we just have heavier planes?

The answer lies in a relatively constant feature of aircraft wings. The lift to drag ratio - which is visible in terms of glide angle. The better the lift to drag, the flatter the glide angle. Now making a plane heavier doesn't change that angle, but it does increase the drag, because the wing needs to generate more lift to keep the weight up, and therefore up goes the drag. And drag times the flight distance is the energy it takes in level flight. Which as I showed in a previous post is the dominant energy usage on a long haul flight.

A heavy battery gets to the stage where you cant carry anything BUT the battery to get the range, and no payload means no profit.

It's like solar powered planes or man powered planes, You can do it but it is a dead end. You cant do anything really useful in terms of load carrying.

There is another serious problem in science and engineering too, and that is compartmentalisation. A person involved in battery design doesn't know aerodynamics and vice versa. Each may be struggling towards unattainable goals without being aware that they are wasting their time.

And woe betide if they, as I did with a well known self styled 'inventor', point out that the task assigned was actually *physically impossible*. It is very tempting to carry on taking the salary and inventing reasons...instead of being constructively dismissed for pointing out that the boss didn't know what he was talking about.