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The largest electric aircraft just flew [video]

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Re: The largest electric aircraft just flew [video]

#291

Post by bluGill »

athrowaway3z wrote: post #272
class3shock wrote: post #155

Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…

The economics to do what planes do today make no sense; but i think that's making the analysis the wrong way around. There are opportunities for which airplanes have never made economic sense because they have big fixed costs like pilot, hangar, fuel-infra, engine(-maintenance). So will small short haul (?pilot-less) rechargeable planes have enough allure to beat out alternatives where planes were never considered be…

The big problem with autonomous airplanes is they still require airports. I don't have a runway in my backyard, and I can't build one because someone else has a house there. My closest runway is about 20 minutes away, and then once I get to the far airport it is another 20 minutes to get where I'm going. This is why commute by airplane will always be a niche only a few people can do. In turn this means airplanes will never scale to be as cheap as cars are (a new Cesna stationair HD MSRP is over $700k - I submit that if they were building 40 per hour like many SUVs are built the cost would be around $70k)

Even a farmer is unlikely to be willing to give up that much space from their farmer operation. I do know farmers who have their own private runways, but they love flying and so are willing to give up some income to have a runway. They are giving up thousands of dollars in gross income to have that runway.

I happen to have a backyard that is big enough for a helicopter (I think - I never measured but I think I'm at the minimums the FAA requires), but I have an oversized yard. There are a lot more places for a helicopter. Most local parks have enough space, but I think communities would object to regular use. (if used only a couple times a month no problem, but more that and the noise and need to clear everyone else out will make it an objection)

Re: The largest electric aircraft just flew [video]

#293

Post by bluGill »

fmpfmp wrote: post #237
class3shock wrote: post #155

Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…

Also consider that an empty battery weighs the same as a charged one. Whereas empty fuel tanks don't. I wonder how annoying this is for the engineers to stay within landing weight limits (MLW)

My guess (I'm not an engineer) is landing weight limits are more then because the airplane will never have more than that anyway. They need a little better suspension in case of a hard landing, and different training for the aircraft (which you need anyway) to account for it handling differently, but otherwise it is still an airplane. Maybe bigger spoilers or some other part as well to better bleed off speed.

They need to account for it of course, but it seems more like account for it, not difficult. Any engineer in this space able to comment?

Re: The largest electric aircraft just flew [video]

#294

Post by tmtvl »

jryle70 wrote: post #38
tmtvl wrote: post #29

Earlier quoted context omitted.

Commercial passenger planes can generally only lift off and on at dedicated facilities, though.

So both can coexist? what's the issue? Why does HN waste energy on pointless pissing contests?

Yep, both can coexist perfectly well, in fact rail + flight + water + cycling should be good enough to account for the vast majority of mobility requirements.

Re: The largest electric aircraft just flew [video]

#295

Post by bluGill »

ddlsmurf wrote: post #197
class3shock wrote: post #155

Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…

Yes, it doesn't even make sense to make electric trucks, let alone airplanes. Or they'd be mostly battery.

There are a lot of trucks that never go very far in a day. Many of them are used for "last mile" delivery. They start at a warehouse, get loaded, then go make a few deliveries and head back for the next load. While fast charging is needed, they don't go very far and thus don't need extreme range.

It is a valid question though: how do we get more of the long distant freight onto trains. Followed closely by how to we get existing freight trains to move to all electric instead of diesel electric (I've been told railroads have studied this: if diesel gets to $8/gallon it is cost effective - but I can't find any references to cite and so you should take this "Fact" with some salt)

Re: The largest electric aircraft just flew [video]

#296

Post by theflyingelvis »

2III7 wrote: post #252
dyauspitr wrote: post #164

Earlier quoted context omitted.

Unless they have a whole new airport and flying experience, I don’t think a lot of people are going to fly just 125 miles. That’s less than two hours of driving. It would be 2 hours of just airport shenanigans much less the flight itself.

You don't drive to islands.

Bridges are a thing

Re: The largest electric aircraft just flew [video]

#297

Post by brohee »

Tepix wrote: post #210
onjectic wrote: post #106

I don’t see how a purely electric aircraft could ever beat synthetic jet fuel made with electricity. If this is a hybrid, I am curious where they are stealing energy from.

Well, what’s the efficiency of synthetic jet fuel production? Is it still competitive? Can we realistically get lots of it, like ever?

Efficiency is not that that important in an era of negative price electricity.

Synfuel made just from air and electricity is doable (both water and carbon dioxyde can be extracted from the atmosphere). And with 10% of what's spend on IA we'd be way out of the lab...

Thankfully there are military budgets (synfuel makes sense on a nuclear carrier)

Re: The largest electric aircraft just flew [video]

#298

Post by 542354234235 »

bluGill wrote: post #293
fmpfmp wrote: post #237

Earlier quoted context omitted.

Also consider that an empty battery weighs the same as a charged one. Whereas empty fuel tanks don't. I wonder how annoying this is for the engineers to stay within landing weight limits (MLW)

My guess (I'm not an engineer) is landing weight limits are more then because the airplane will never have more than that anyway. They need a little better suspension in case of a hard landing, and different training for the aircraft (which you need anyway) to account for it handling differently, but otherwise it is still an airplane. Maybe bigger spoilers or some other part as well to better bleed off speed. They ne…

Landing weight limits are less than takeoff limits because of the extreme stress it puts on the landing gear. This is why planes that have an issue right after takeoff often need to dump tens of thousands of gallons of fuel before they can land.

>Aircraft have two main types of weight limits: the maximum takeoff weight is composed of dry operating weight (DOW) plus payload (passengers and cargo), collectively the zero fuel weight (ZFW), plus the trip fuel, contingency, alternate, final reserve and the block fuel (taxi fuel), and the maximum structural landing weight, with the maximum structural landing weight almost always being the lower of the two. This allows an aircraft on a normal, routine flight to take off at a higher weight, consume fuel en route, and arrive at a lower weight. [0]

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

Re: The largest electric aircraft just flew [video]

#299

Post by bluGill »

kmeisthax wrote: post #102
QuantumNoodle wrote: post #32

These kind of startup excite me. More so than the "next killer app" or "look what we shoved AI into." Cheap electric transportation can finally offset USA's lacking rail commutes and attack Europe's short flight market (which is already cheap). Now we need bigger planes or more frequent planes and the next startup to solve the energy needs.

USA's lacking rail commutes come down to the fact that America's leaders made the deliberate decision to destroy its own rail network and force people onto planes. The electric range of this aircraft is 125 miles[0], which is at the low end of the range where conventional intercity rail is time-competitive with the plane. A bullet train would absolutely smoke this. tl;dr I have a few qualms with this app[1]. Now, thi…

> USA's lacking rail commutes come down to the fact that America's leaders made the deliberate decision to destroy its own rail network and force people onto planes

This is utterly 100% false!

The US made the decision to focus rail roads on freight. You never think about freight because you never use it for anything personal, but it is still there. The US beats any place in Europe for Freight and few countries even come close to US for freight rail.

There was a decision made to get rid of passenger rail. However most of those destroyed routes are routes that nobody sane would put passenger rail on today even in high rail mode share countries. There are only a small number of routes should return - for most of the lost routes a bus is better. That isn't to say passenger rail is bad. However the routes we had were bad.

Re: The largest electric aircraft just flew [video]

#300

Post by thelastgallon »

I wonder if Aluminium–air battery can be used for flying. They are not rechargeable, but with zero cost of energy during daytime, a supply chain can be built.

The design battery energy density is 1300 Wh/kg (present) or 2000 Wh/kg (projected): https://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery

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