The age of electric flight is finally upon us • Hacker News Board

Re: The age of electric flight is finally upon us

#51

Post by sheldonth » Fri, Jun 21, 2019, 3:16 PM UTC

NickM wrote: post #17

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.

Yeah I have wondered about this option as well. Hydrogen fuel cell cars make very little practical sense for a lot of reasons, but most of those reasons don't seem to apply so much when you're dealing with air travel: - It'll be a long time before fuel cells are cost competitive with gas or electric cars, but for planes the cost of fuel and operation is much more significant than with a car, so the upfront cost for b…

I wonder what a YC application with such an idea might look like. Design the plane and the fuel containment/loading systems at 2 airports. Start America's first "carbon free" aviation route. Maybe move freight instead of people at first for an easier regulatory pipeline. It's absolutely crazy and would almost certainly fail but so are most of the revolutionary startup ideas that deal with earth heating in any meaningful way.

Re: The age of electric flight is finally upon us

#52

Post by wlesieutre » Fri, Jun 21, 2019, 3:16 PM UTC

usrusr wrote: post #32

afiori wrote: post #4

Earlier quoted context omitted.

Is it so much less energy dense per liter to offset the gain in weight? In a plane energy per weight is rather important afterall

The penalty for more volume is rising with higher speed, whereas the penalty for more weight is staying pretty much constant. In a fast plane, volume is just as important as weight, if not more.

Also liquid fuel tanks in planes are usually out in the wings. They can be shaped pretty much like whatever as long as the fuel keeps flowing.

Pressure vessels though, you're better off making them round.

Re: The age of electric flight is finally upon us

#53

Post by taf2 » Fri, Jun 21, 2019, 3:16 PM UTC

semi-extrinsic wrote: post #41

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

I see that does making exceeding 60k pretty scary. I was from London to Denmark and we had cabin pressure loss I think we were maybe at 30k and dropped pretty fast to 20 if I recall correctly. The sensation that I remember was slow motion and shock from the flight attendant as the masks did not deploy. Later after landing the captain told us during preflight they set the cabin pressure incorrectly such that as we went too high an emergency system kicked in the prevent the cabin from exploding... I was maybe 12 so the details are fuzzy but definitely the take away is cabin pressure loss is no joke

Re: The age of electric flight is finally upon us

#54

Post by smileysteve » Fri, Jun 21, 2019, 3:17 PM UTC

CraftThatBlock wrote: post #25

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...

Higher means lower air density, meaning less lift, meaning higher power usage, which is even more critical with electric

Lower air density also means both lower drag and more slippage; would definitely need adjustable pitch.

Re: The age of electric flight is finally upon us

#55

Post by bdamm » Fri, Jun 21, 2019, 3:21 PM UTC

Rychard wrote: post #31

j9461701 wrote: post #24

Earlier quoted context omitted.

This is why I'm so excited for lithium-air batteries. Theoretically they'd carry ~40.1 MJ/kg, which is very competitive with gasoline's ~46.8 MJ/kg. Factoring in the higher efficiency of electric drives (95% vs. 35% for say a regular ICE car), you'd be getting effectively over double the energy per pound in terms of moving you around.

Burning fuel reduces weight, so the range per unit of (remaining) fuel is greater. Batteries however, weigh the same amount regardless of charge level. I wonder if this affects the calculations in an appreciable way.

At nearly double energy efficiency, nobody will care much about the weight of the batteries. Some airplane design changes due to no longer being able to take off heavier than they are allowed to land (this is common on long hauls) but the design changes also likely change due to better placement of thrust and its weight (engines go almost anywhere the designer wants), and better control over location of the weight (batteries aren't liquid and don't slosh around, and a sloshing liquid also has negative aerodynamic effects.)

Re: The age of electric flight is finally upon us

#56

Post by Yizahi » Fri, Jun 21, 2019, 3:21 PM UTC

aphextron wrote: post #49

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 minute…

The answer is - railway ;) . I doubt that small craft (any prop type) will ever be so quick overall - they are aircrafts and require all aircraft related checks and control, safety for passengers, safety from passengers etc. And about price I don't know, maybe it will be slightly cheaper than jets. So you'll have slightly cheaper businessjet prices, which are still astronomical.

Re: The age of electric flight is finally upon us

#57

Post by whamlastxmas » Fri, Jun 21, 2019, 3:23 PM UTC

base698 wrote: post #40

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...

Engines don't stall, planes do. Plane stalls are about aerodynamics, and nothing to do with the engine. Current engine designs operate poorly at higher altitudes for a number of reasons: less air density meaning less oxygen to burn and less air to push against. Turbine engines can flame out, which maybe that's what you were referring: https://en.m.wikipedia.org/wiki/Flameout

Stalling is a term also used with engines, and it's pretty clear he's talking about engines not working at altitude so "stall" is probably the correct term

Re: The age of electric flight is finally upon us

#58

Post by taf2 » Fri, Jun 21, 2019, 3:23 PM UTC

base698 wrote: post #40

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...

Engines don't stall, planes do. Plane stalls are about aerodynamics, and nothing to do with the engine. Current engine designs operate poorly at higher altitudes for a number of reasons: less air density meaning less oxygen to burn and less air to push against. Turbine engines can flame out, which maybe that's what you were referring: https://en.m.wikipedia.org/wiki/Flameout

Yeah I’d imagine most of the reasons sited from this hat wiki article don’t apply to an electric plane. But yeah air density would definitely be an issue but I thought the nasa Helios flight showed 90k to be the upper limit? So figured pushing to bear that altitude could be achieved and possibly beneficial since it would avoid bad weather and reduce drag... I guess was imagining the bulk of the engine power would be consumed at the start of the flight to reach altitude and then from there mostly glide until descending to land... but I’m not an aviation engineer at all just dreaming of quieter sky’s and less pollution

Re: The age of electric flight is finally upon us

#59

Post by bdamm » Fri, Jun 21, 2019, 3:23 PM UTC

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?

Propeller noise can be generally managed more easily than engine noise.

Re: The age of electric flight is finally upon us

#60

Post by ggreer » Fri, Jun 21, 2019, 3:24 PM UTC

gambiting wrote: post #39

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.

1kg of kerosone can be kept in a plastic tank that weighs nothing. 1kg of hydrogen has to be kept in a pressurized, pure-lead 70kg bottle, and even then hydrogen will diffuse through it in just few weeks. So to take 1kg of hydrogen with you you're taking a lot of weight in the tanks too.

Some rockets use hydrogen and their pressure vessels aren't so heavy as to keep them stuck on the ground. You only need to contain the hydrogen for hours, not weeks.