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The age of electric flight is finally upon us

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Re: The age of electric flight is finally upon us

#41

Post by semi-extrinsic »

taf2 wrote: post #22

I wonder if with electric we can fly higher like much higher maybe 80k to 90k since we don’t have to worry about the engine stalling. Could this also make the flight times comparable or faster? For sure less turbulence. As someone who lives on a flight path I’m eager for the change in noise pollution too- though I’m worried the transition will take decades...

You can't really go above the Armstrong limit (~60k feet) in a passenger airplane without adding huge complexity in handling the event of cabin pressure loss.

https://en.wikipedia.org/wiki/Armstrong_limit

Re: The age of electric flight is finally upon us

#42

Post by gambiting »

isostatic wrote: post #35
SeanBoocock wrote: post #16

Earlier quoted context omitted.

From the article: > Even assuming huge advances in battery technology, with batteries that are 30 times more efficient and "energy-dense" than they are today, it would only be possible to fly an A320 airliner for a fifth of its range with just half of its payload, says Airbus's chief technology officer Grazia Vittadini. > "Unless there is some radical, yet-to-be invented paradigm shift in energy storage, we are going…

A320 family range varies from 5500km to 8700km, so "a fifth of it's range" is around 1500km, which is 80% of the industry emissions. I'm not sure of that quote either -- a lithium ion battery is currently about 1MJ/kg and 1MJ/litre. Jet fuel is 43MJ/kg and 35MJ per litre (values from from wikipedia) So a battery that's 30 times more energy dense will be in the region of jet fuel, and thus would presumably be able to…

Don't forget that the fact that the fuel is burnt up as you travel is a big factor in the range of an aircraft. The weight of batteries does not go down during the flight.

Re: The age of electric flight is finally upon us

#43

Post by maxxxxx »

marvin wrote: post #20

I fly gliders. Absolutely can't wait until my local club finally decides to get an electric single-seat self-launching glider, preferably with enough endurance to do some additional tens of kilometers after the launch, in order to avoid landing out if the weather dies out. It's a gamechanger with regards to both costs and convenience. No towplane, towplane pilot, no outlandings.

How about a battery that can glide by itself? You attach a big battery for the launch and once you are up you disconnect and it glides back to the airfield. That should be possible today technically. Not sure how safety would work.

Re: The age of electric flight is finally upon us

#44

Post by semi-extrinsic »

alex_young wrote: post #6
ginko wrote: post #2

I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene. The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.

The main source (95%) of hydrogen fuel in the US is a by-product of Natural Gas extraction ( https://www.energy.gov/eere/fuelcells/hydrogen-production-na... ). What problem are we solving by moving to hydrogen?

When you do steam methane reforming to produce hydrogen, separating out the CO2 is a necessary step in the process. Then it's just a matter of storing it underground, rather than just emitting it.

Re: The age of electric flight is finally upon us

#45

Post by pjc50 »

ginko wrote: post #2

I'm surprized hydrogen fueled flight isn't looked into more. Hydrogen can be produced using electrolysis and it's packs significantly more energy per weight even than kerosene. The main drawback is the low density which would require larger fuselages, but that should be offset by the significantly lower weight.

Rather than mess around with hydrogen, with the proper mandates a lot of jets could switch over to renewable jet fuel. One of the main leaders here is, surprisingly, the US Navy: http://www.altenergy.org/new_energy/seawater-into-jet-fuel.h... directly from seawater and nuclear energy from a ship's reactor, or various other biofuel initiatives.

Re: The age of electric flight is finally upon us

#46

Post by bdamm »

Yizahi wrote: post #37

Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would…

Electric wheel propulsion on aircraft seems like an entirely unnecessary feature. Airplanes have no difficulty using their primary form of propulsion - moving air - to move on the ground, and it takes very little energy to do it compared to the energy required to move through the air while off the ground.

Re: The age of electric flight is finally upon us

#47

Post by jandrese »

Tade0 wrote: post #38
wlesieutre wrote: post #13

Earlier quoted context omitted.

As a gas at 1 atmosphere, wikipedia says 0.011 MJ/L, compared to jet fuel at 35 MJ/L. You'd save weight (it weighs less than air so this would make you float) but need 3000x as much space if it's not compressed. Compressed at 690 bar (about 680 atmospheres) it goes all the way up to 5 MJ/L, only 7x as much volume of fuel required compared to jet fuel. But the tanks to pressurize something that much are presumably ver…

Counterintuitively enough liquid ammonia packs more hydrogen than liquid hydrogen per unit volume - also it condenses at -33C (-27.4F), so it actually wouldn't require cooling once in the air. It can be burned in a gas turbine, but for now the NOx emissions are pretty horrible.

Also, it's horribly corrosive and poisonous.

Re: The age of electric flight is finally upon us

#48

Post by iosonofuturista »

davidrm wrote: post #14
iambateman wrote: post #10

From the article: conventional fuel for a 100 mile flight costs $400, while electric energy would cost $12. This seems like such a tremendous difference that the market would be in an arms race to make it a reality. Especially considering electric motors have fewer moving parts and so require less maintenance. Oh and it would be so quiet.

> Oh and it would be so quiet. would it? I was under the impression that proppelers were much louder! what is the biggest source of noise in an aircraft/type?

Ah, good ol' Thunderscreech[0]!

> The XF-84H was almost certainly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as the "Mighty Ear Banger". On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away. Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down.

[0] https://en.m.wikipedia.org/wiki/Republic_XF-84H_Thunderscree...

Re: The age of electric flight is finally upon us

#49

Post by aphextron »

Yizahi wrote: post #37

Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would…

>I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes.

The whole point of electrifying flight is that it makes small aircraft economical for airlines. The future of inter-city transport will be light aircraft with less than 20 passengers flying out of of small regional airports. Driving to LAX and waiting in security to get on a huge jet and fly for 90 minutes to SF sucks, but so does the drive. We're stuck with two terrible options there. Driving to a tiny airfield and hopping directly onto an electric plane that costs the price of a bus ticket will change everything about the way people live. They will never replace turbine engines for long haul routes, but the vast majority of commuter flights will be completely electric within 30 years.

Re: The age of electric flight is finally upon us

#50

Post by smileysteve »

bdamm wrote: post #46
Yizahi wrote: post #37

Simple electric wheel on aircrafts for taxiing (as compared to the electric powered flight) took almost 10 years from first demo tests and it still hasn't entered production on commercial airlines. And that thing is completely possible with modern tech. I highly doubt we will see electric powered aircrafts (bigger than small* experimental crafts) in our lifetimes. Way too much limitations existing today. But it would…

Electric wheel propulsion on aircraft seems like an entirely unnecessary feature. Airplanes have no difficulty using their primary form of propulsion - moving air - to move on the ground, and it takes very little energy to do it compared to the energy required to move through the air while off the ground.

> Airplanes have no difficulty using their primary form of propulsion

There are a few things to be weary of; Mostly that thrust is loud and dangerous to air crews. Weight shifts.

Individually driven wheels offer some precision without significant forward thrust.

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