361–370 of 387 posts
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>They already very agressively hide car lithium fires But you found out... how?
They regularly pop up on the usual guanxi, douyin/weibo etc. They stay up for a few hours usually.
Yet you state their frequency as some sort of statistical fact. Your anecdotal experience doesn't make it any more or less true.
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> A 737 has a lower drag coefficient than my car Drag coefficient is about the shape and needs to be multiplied by area to get drag. Your car is a lot smaller when viewed from the front than a 737. And there's no way a plane flying at the speed it does has the same drag losses as two EVs.
That’s why I approximated the fuselage as two EVS (the frontal area) and I only looked up the drag coefficient of a 737 because it’s a well-known narrow-body airliner. I don’t know what speeds they flew, but AFAIK most maiden flights are very tame. My point stands, low hundreds of kilowatthours of energy seems like the right ballpark.
Have you ever seen a car and a plane? The Tesla model x has a frontal area of 2.6 sqm and a 737 fuselage alone, without any wings is already 11 sqm. With all attachments it’s at least 20 sqm.
And half of the energy for altitude gain and half for drag is way too optimistic.
The flight cost more than $5 in energy.
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…
> Lets say we are using batteries that are 300 wh/kg (0.3 kwh/kg) 400 Wh/kg are almost there [1]. [1] https://youtu.be/nM86DBOqgPM?t=541
For cars the economics is a dicey proposition. Because $/wh is important. The extra range (dubious) or lower weight has to cover the cost difference.
But for electric aircraft there is a lot to be gained by weight savings.
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> and should not happen on well planned flights You make it sound like it is acceptable for a badly planned flight to have a fuel emergency. It is not. If there is a fuel emergency (or the plane lands with less than 30min of fuel) there will be an incident investigation that treats the situation as serious as if the plane had crashed. If the investigation discovers it was nothing more than bad planning, (at minimum)…
> there will be an incident investigation that treats the situation as serious as if the plane had crashed No the investigation isn’t as serious as if the plane had crashed. In July 2026 nine planes simultaneously had a fuel emergency in London. You bet it’s different from nine planes simultaneously crashing in London. It helps to understand different kinds of fuel emergency. Declaring a fuel emergency to get to a di…
But still very serious. 9 simultaneous fuel emergencies could have easily overwhelmed ATC and snowballed to worse issues.
Something lead 10 different aircraft to make the exact same mistake and find themselves without enough fuel for a safe diversion. There will be recommendations to try and prevent it from happening again.
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Lots of down votes on this but it is a legitimate question. The goal is likely to have the majority of flight off of batteries. That being said, the total weight of the emergency fuel plus generators is likely far less than the weight of the extra batteries they would haul around for the safety margin they need. So they end up lighter and more capable AND don't need to burn fuel. That being said, I wouldn't be surpri…
> That being said, I wouldn't be surprised if they didn't start the generators during critical phases so they may end up using some fuel for a flight, but not much. I would guess the opposite. Many parts in a turbine engine are "lifetime limited" by number of engine starts. That is, you are required to tear down the engine and replace certain parts after a certain number of engine cycles. That makes the economics of…
There aren't that many existing flight routes that will fit into the 125 mile range (though the existence of this plane might change that), so I suspect we will see most of these planes go into service on slightly longer routes. So they will probably still need one cycle per flight.
Though... The video isn't quite clear if the 125 miles is what they can fly without starting the turbines or if it's what they can fly without needing the turbines ready to act as an emergency reserve. I actually suspect it's the later and this aircraft can make it to 200+ miles without starting the turbines.
Where I live, there aren't that many 125 mile flights, but there are a lot of 200 mile fights.
I also suspect the turbines are sized so that only need to start one of the two turbines on most flights, which would extend lifetime a lot. Ideally the turbines would be sized so that one is enough for cruising, and with two you can actually charge the batteries after a go-around (enough to enable a second and third go-around)
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I remember reading about making ground effects electric planes for this reason. You need a reserve, but if your plane could double as a boat and was flying over water, that would satisfy the requirement.
As long as water conditions allow for a safe landing. In much of the world that severely limits when you can operate due to storms or ice. In practice routine use of ground effect vehicles will be mostly limited to lakes and inland seas with fairly benign weather. Like I don't think we're going to have regular passenger service from San Francisco to Los Angeles or Detroit to Cleveland.
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Batteries aren't rapidly improving. Every single battery that has proposed higher energy density also has downsides in max discharge current. We may get at best like 10% improvement over what it is today.
That's max discharge current per cell though. You are going to have a lot of cells in a plane like this.
The only way to reduce current is to put batteries in parallel, which for a given voltage doubles the weight of the battery pack.
You could go with lower voltage, but that means for a given, power, you need more current, which drops your efficiency.
Hybrid! That's what happens when you build new devices around old infra. Steve Jobs didn't design the iPhone around Carriers; it was the other way around.
A new approach required new thinking about everything involved, including takeoff and landing. They didn't do that; that's why they ended up with the compromise of a hybrid. It was a sign, and they ignored it and went ahead. Imagine a design that requires - no traditional landing and takeoff, including no ATC; some electric planes are already built around that, but sadly not this one.
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Electric planes can in theory get longer flights, provided they change the flight profile - you spend a lot of energy going up to higher altitude, and the essentially glide down.
The energy used to achieve altitude is then saved in the descent stage. So that’s not an issue for aircraft, regardless of how they’re powered. This is why every flight you’ve ever been on climbs to cruise altitude as fast as possible. High altitude where the air is less dense is better for speed due to less drag. This is also power source agnostic.
When you size a gas engine for a plane, you design around the power needed to takeoff on a given runway, which is fine because in cruise, you will throttle down and use less fuel.
When you design an electric vehicle, if you design it the same way, you end up carrying effectively dead battery weight, which also affects power consumption during cruise (you either go faster, or use use more wing, which creates more induced drag).
IF you design it for cruise, you end up being horribly inefficient at takeoff.
The only 2 solutions are
1. 10 mile long runway where you can take your time accelerating, to reduce the torque requirement on the motor. You would basically limit the current draw and the plane would accelerate slowly, and eventually you get to cruise speed
2. Changing your flight profile, where you get to high altitude ASAP where you can be more efficient,
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That's max discharge current per cell though. You are going to have a lot of cells in a plane like this.
To get high voltage, you need batteries in series, which means all the batteries see the same current. The only way to reduce current is to put batteries in parallel, which for a given voltage doubles the weight of the battery pack. You could go with lower voltage, but that means for a given, power, you need more current, which drops your efficiency.
This is supposed to be able to handle "up to" 2-hour flights, and (for jets at least) takeoff power is about 3x cruise power, so about 1.5 watts per watt-hour of battery, or a 1.5C peak discharge rate. What chemistries are you thinking of that cannot handle this?