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

Re: The age of electric flight is finally upon us

#111

Post by rbanffy » Fri, Jun 21, 2019, 5:34 PM UTC

usrusr wrote: post #65

isostatic wrote: post #35

Earlier quoted context omitted.

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…

The 80% figure are flights longer than 1500 km. 1500 and less are the 20%. So even if all those flights were switched to magic zero emission electricity, the aggregate improvement over the whole industry would barely beat the relative improvement between a 737 NG and a MAX. (yes, this is an apples to orchards comparison)

To be fair, the MAX has been zero emission for a couple months now.

Re: The age of electric flight is finally upon us

#112

Post by Havoc » Fri, Jun 21, 2019, 5:43 PM UTC

Surprised at the hybrid comment. I would have expected electric for the cruise phase not takeoff and landing

Re: The age of electric flight is finally upon us

#113

Post by opportune » Fri, Jun 21, 2019, 5:44 PM UTC

Havoc wrote: post #112

Surprised at the hybrid comment. I would have expected electric for the cruise phase not takeoff and landing

Electric is more burstable so it makes more sense for periods of rapid acceleration/deceleration. Hybrid cars work the same way

Re: The age of electric flight is finally upon us

#114

Post by mmphosis » Fri, Jun 21, 2019, 5:49 PM UTC

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.

The race is already on.

REDMOND, WA and VANCOUVER, B.C. – March 26, 2019 – magniX, the company powering the electric aviation revolution, and Harbour Air, North America’s largest seaplane airline, today announced a partnership to transform Harbour Air seaplanes into an all-electric commercial fleet powered by the magni500, a 750 horsepower (HP) all-electric motor. https://news.ycombinator.com/item?id=19539796

Re: The age of electric flight is finally upon us

#115

Post by sokoloff » Fri, Jun 21, 2019, 5:50 PM UTC

ac29 wrote: post #94

sokoloff wrote: post #90

Earlier quoted context omitted.

The taxi fuel is not primarily used for motivation of the airplane around the airfield, but just from idling the engines. (It's about minutes of ground operation more than miles of ground operation.) Electric drive wheels don't eliminate that unless you don't start the engines until near the hold short line (in which case, you don't have air conditioning or electric power, meaning you end up running the APU [itself a…

Yes, you'd need at least enough battery power to power not just the drive wheels, but the other things that engine power provides for like air conditioning. I wonder how large a pack would actually be required (of course there are huge differences between airports - some of them youre in the air only a few minutes after leaving the gate, some it can be 20-30 minutes). If it was a large amount of battery, it would be…

Anecdote, but relevant, we were on the ground in Las Vegas in a 787-400 (an all-electric, no-bleed airplane) and due to a 15 minute ground hold while they sorted an issue with a brake indication, the APU powered pack alone was not able to keep up with the Vegas environmentals. (They couldn't run a main engine because they were doing maintenance in that area.) They were able to bring in ground-based chillers to take some of the edge off, but it was uncomfortably hot in the cabin with an APU running.

A 787 may be ideal for an electric conversion (since it's already a no-bleed airplane). Even then, you probably might as well run the APU for electrics on the ground, since you're going to be carrying around that amount of weight anyway.

Re: The age of electric flight is finally upon us

#116

Post by vosper » Fri, Jun 21, 2019, 5:53 PM UTC

rbanffy wrote: post #110

mannykannot wrote: post #92

Earlier quoted context omitted.

A fire in an airplane is a lot more scary than a loss of power (proportionally more so in a small airplane, where an off-field landing is feasible, and increasingly they have ballistic parachutes), while there is currently a well-known problem of fires (that can't be extinguished) in high-power-density batteries. Gasoline is dangerous, but we have learned how to handle it safely.

You could mount batteries on pods that could be released if needed. Additional benefit would be that the pods could be replaced on the ground by fully charged ones for faster turnaround.

You can't really rain burning battery pods down on the landscape, though. What if the plane is over a populated area?

Re: The age of electric flight is finally upon us

#117

Post by murkt » Fri, Jun 21, 2019, 5:54 PM UTC

namirez wrote: post #106

As others have noted, electric flights require a major breakthrough in the battery technology. Here are energy density numbers for gasoline, jet fuel, and lithium-ion batteries: Gas and jet fuel specific energy density ~= 45 MJ/kg; Lithium-ion specific energy density Even worse, a jet engine is much better at generating power. A modern high-bypass turbofan engine can generate 10 kW/kg whereas an electric motor is aro…

1 kW/kg for electric motors looks a bit on the low side for me. Tesla Model S with the highest power rating has 581 kW, and I don't think that its motors weigh in for more than half a ton combined.

I've found a statement that some version of their motors with 270 kW weigh 31 kg (70 pounds). Which amounts to 8.7 kW/kg and isn't far off from your 10 kW/kg estimate for modern turbofan engines. Also it's probably not the latest number for an electric motors, and newest motors have better power-to-weight ratio.

Re: The age of electric flight is finally upon us

#118

Post by 0xffff2 » Fri, Jun 21, 2019, 5:54 PM UTC

stcredzero wrote: post #109

namirez wrote: post #106

As others have noted, electric flights require a major breakthrough in the battery technology. Here are energy density numbers for gasoline, jet fuel, and lithium-ion batteries: Gas and jet fuel specific energy density ~= 45 MJ/kg; Lithium-ion specific energy density Even worse, a jet engine is much better at generating power. A modern high-bypass turbofan engine can generate 10 kW/kg whereas an electric motor is aro…

Electric motors can enable something which jet fuel and gasoline cannot: beamed power. There could be a new class of vehicles which only have a small onboard power store for emergency purposes. The weight savings would be about 20%.

Is this something that someone has actually fleshed out with real numbers? The infrastructure and efficiency problems involved seem at first glance to be extremely challenging.

Re: The age of electric flight is finally upon us

#119

Post by verelo » Fri, Jun 21, 2019, 5:54 PM UTC

sandworm101 wrote: post #100

mannykannot wrote: post #81

Earlier quoted context omitted.

That's probably OK: having to replace a motor would be a small cost compared to that of an off-field forced landing that went badly.

>> off-field forced landing that went badly. Parachutes. They are now a very practical option for GA aircraft. More than a few cessnas have been saved. The concept of "off-field forced landing" should too be going away. https://brsaerospace.com/cessna-faqs/ " Q. How many aircraft saves are credited to a BRS Whole Aircraft Rescue Parachute System? A. As of August 2017, 376 ."

"Q. How much damage will be done to my plane if I land it with a parachute? A. In all likelihood the aircraft will suffer some significant damage. The terrain where you land will affect this greatly. Though the extent of damage has varied from plane to plane, most GA aircraft that have come down under a BRS deployment have eventually (or will soon) fly again."

Call me a skeptic until they provide hard numbers and details of what planes make it back into the sky v's scrapped, and those planes have a year or two of a service history showing they make it back into a reasonable service lifestyle, I'd be shocked to hear this is great at saving planes. I find a lot of the old 172's i fly have plenty of bumps and scratches, but wouldn't be super excited to trust the frame of a plane that went through an experience like this.

I like it from a safety perspective, but in my mind, the reward you get out of a system like this should be your life...I have zero expectations the plane will ever fly again.

Re: The age of electric flight is finally upon us

#120

Post by newsoul2019 » Fri, Jun 21, 2019, 5:56 PM UTC

sandworm101 wrote: post #100

mannykannot wrote: post #81

Earlier quoted context omitted.

That's probably OK: having to replace a motor would be a small cost compared to that of an off-field forced landing that went badly.

>> off-field forced landing that went badly. Parachutes. They are now a very practical option for GA aircraft. More than a few cessnas have been saved. The concept of "off-field forced landing" should too be going away. https://brsaerospace.com/cessna-faqs/ " Q. How many aircraft saves are credited to a BRS Whole Aircraft Rescue Parachute System? A. As of August 2017, 376 ."

Wait, that's an astonishing number of would-be crashes.