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First all-electric seaplane takes flight in B.C.

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Re: First all-electric seaplane takes flight in B.C.

#21

Post by agurk »

abakker wrote: post #14
scottmsul wrote: post #9

Still seems a bit far from replacing jet engines? This article was going on about fuel emissions in the entire aviation industry, this is just an electric propeller. Anyone know how far we are from electric jets? Is such a thing even possible?

I think "Electric Jet" is like saying "Electric Internal Combustion Engine" - A Jet is a type of engine, so an electric aircraft wouldn't be a jet. I know people call Jet-powered aircraft "jets" but, that's really an abbreviation. I think what you're asking though, is whether there are any electric propulsion systems with the same characteristics as jets - i.e. more thrust relative to speed. AFAIK, there are not, bec…

The jet in jet-engine refers to the fact it uses jet propulsion - i.e. producing movement in one direction by ejecting a fluid in the opposite direction. This means that lots of things are actually jet engines - rocket engines and water jets being two common ones.

The propulsion of a 'jet engine' is normally through a gas turbine, which is a type of internal combustion engine, so you wouldn't get an electric gas turbine.

Replacing the gas turbine with an electric motor would in this case produce an electric jet engine.

Re: First all-electric seaplane takes flight in B.C.

#22

Post by aphextron »

squilliam wrote: post #12
scottmsul wrote: post #9

Still seems a bit far from replacing jet engines? This article was going on about fuel emissions in the entire aviation industry, this is just an electric propeller. Anyone know how far we are from electric jets? Is such a thing even possible?

A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. An electric ducted fan would be the battery-powered equivalent.

>A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine.

No, it's not. A propellor creates thrust by slicing the air and creating lift just like a wing, but in a forward direction. A jet engine's fan blades create no thrust in themselves. They provide the compression needed for combustion to occur within the engine, and thrust is created by the expelling of hot exhaust gasses.

Re: First all-electric seaplane takes flight in B.C.

#23

Post by jws »

bzudo wrote: post #3

Off topic and stupid, but could an electric plane be outfitted with lightning rods and/or lightning rockets to attract lightning strikes in order to charge the batteries?

Fermi estimation says…

The internet says the energy of a cloud to earth lightning strike is 10^9 joules. A gallon of jet fuel contains about 10^8 joules of energy. A strike would provide the equivalent of 10 gallons of fuel.

A 737 would need to be struck at least once every 10 miles to keep going.

Sadly, that lightning power number is for cloud to earth, a cloud to airplane is going to be far less. If you try to extract too much power from the bolt it will just go around you.

␄

Meta comment: I like the breadth of this comment's peers. We have this one about the scale of energy, one commenting that it doesn't help range because you can't rely on it, one about the disparity of power between charging and discharging, and one about avoiding complexity and mass in airplanes. All good points. I hope in 12 months we hear back from the lunatic that ignores them and makes a functioning prototype.

Re: First all-electric seaplane takes flight in B.C.

#24

Post by darksaints »

bittercynic wrote: post #10
giarc wrote: post #6

I suspect this would be much, much quieter than a regular gasoline engine correct? These smaller planes are loud.

Much of the noise from small planes is from the propeller(s), so it might not help much.

For retrofits like this, the noise will go down a bit because the engines are inside the fuselage.

Re: First all-electric seaplane takes flight in B.C.

#25

Post by throwawaysea »

aphextron wrote: post #22
squilliam wrote: post #12

Earlier quoted context omitted.

A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. An electric ducted fan would be the battery-powered equivalent.

>A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. No, it's not. A propellor creates thrust by slicing the air and creating lift just like a wing, but in a forward direction. A jet engine's fan blades create no thrust in themselves. They provide the compression needed for combustion to occur within the engine, and thrust is created by the expelling of hot exhaust gasses.

The bypass part of a turbofan does generate thrust.

Re: First all-electric seaplane takes flight in B.C.

#27

Post by semi-extrinsic »

You can do small aircraft like this, no problem. The trouble is you can't scale it up, due to how quickly the power and energy demands go up. This thing is 560 kW and gets a range of 86 nmi; an A320 is around 40 000 kW and has a range of 3 500 nmi, while an A380 is around 80 000 kW and has a range of 8 500 nmi.

Going from this DHC-2 to the A380 requires an increase in energy storage by a factor of around 14 000x, while the max takeoff weight ratio between the two planes is only 250.

Airbus is developing a hybrid electric jet, the E-Fan X. They've done the math. When their CTO was asked about the possibility of an all-electric A320, the response was

"""

Assuming for a moment that we’d be able to rely on batteries 30 times as energy dense as that of today, an A320 would be able to fly with half of its payload for one-fifth of its current range, 500nm max. So, assuming a battery which today does not exist... It doesn’t work, purely electrical will not work.

"""

Re: First all-electric seaplane takes flight in B.C.

#28

Post by agurk »

aphextron wrote: post #22
squilliam wrote: post #12

Earlier quoted context omitted.

A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. An electric ducted fan would be the battery-powered equivalent.

>A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. No, it's not. A propellor creates thrust by slicing the air and creating lift just like a wing, but in a forward direction. A jet engine's fan blades create no thrust in themselves. They provide the compression needed for combustion to occur within the engine, and thrust is created by the expelling of hot exhaust gasses.

That is a description of a turbojet - the earliest type of aero jet engines[0]. GP is referring to modern turbofans which are defined by having a bybass - i.e. air that is compressed and then expelled rearwards without passing through the main turbine body[1].

This is done to trade the high speed of the jet exhaust for a larger amount of air moving more slowly. Making the speed of the jet plume closer to the true airspeed of the aircraft makes it more efficient.

[0] https://en.wikipedia.org/wiki/Turbojet

[1] https://en.wikipedia.org/wiki/Turbofan

Re: First all-electric seaplane takes flight in B.C.

#29

Post by darksaints »

aphextron wrote: post #22
squilliam wrote: post #12

Earlier quoted context omitted.

A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. An electric ducted fan would be the battery-powered equivalent.

>A modern jet engine is just a shrouded propeller that happens to be powered by a jet turbine. No, it's not. A propellor creates thrust by slicing the air and creating lift just like a wing, but in a forward direction. A jet engine's fan blades create no thrust in themselves. They provide the compression needed for combustion to occur within the engine, and thrust is created by the expelling of hot exhaust gasses.

No, the exhaust is not the primary thrust generator, unless you're talking about military jets. The fans themselves are creating the majority of the propulsion. Modern high bypass designs have bypass ratios of ~10:1, meaning for every 1 lb thrust generated from the exhaust, 10 lbs comes from the fan.

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

Re: First all-electric seaplane takes flight in B.C.

#30

Post by nuccy »

I'm a big fan of renewable energy (solar, wind), electric cars and likely electric planes (not yet available, so hard to say). But my biggest concern is that all this will eventually lead to people decisions being affected by rather this hipe, than common sense (like with nuclear power, which is the greenest currently available peak/off-peak source of energy). Something similar can also happen, as with Saturn 5/Apollo, after some time we will lose the technology, because people retire, workshops are disassembled. We can loose technology of efficient piston and jet engines, nuclear reactors, ultrasonic flight, et al. This by itself is fine, batteries work fine obviously, though one can imagine conditions where it is not the case: Antarctica, Mars, Moon, space, etc. Just look at Juno space probe, which instead of small RTG uses huge solar arrays, which produce just few hundreds of watts on Jupiter orbit, while being capable or producing kilowatts on Earth one.
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