This seemed intuitively wrong to me (like, way too low a cost), but: 25,000 pounds moving 100 mph is equal to 11,331,007 J of kinetic energy. Since 3.6 million J equals 1 kWh and 1 kWh on average costs $0.17, that means you could accelerate 25,000 pounds to reasonable bare minimum flying speed for about fifty cents (not considering efficiency of the machinery). My mind still can’t process this, but math is math.
On the other hand, looking at it from a potential energy perspective it’s a bit more expensive. 25,000 pounds at a cruising altitude of 10,000 ft. (still quite low from an airliner perspective) is about 339 million J, 94 kWh or about $16 – the cost of lunch at MacDonald’s.
Since a plane requires the most thrust at takeoff, you could use ground-based catapults to get the plane to takeoff speed (or faster even) and then you could carry smaller batteries and propelling machinery. For extra fun, you could have landing planes snag a wire and use their momentum to accelerate a plane taking off.
To save even more weight, since you’re going airport-to-airport you could leave off the landing gear and just have the planes come down on a bouncy trampoline-like surface. If you think that’s batshit crazy, the British actually experimented with this idea for their aircraft carriers in the 1950s.
Edit: to make these numbers more realistic I’m going to assume something like a 737, which can weigh something like 150,000 pounds fully loaded (this includes fuel but you’d need batteries instead for an electric plane). Getting this to a 150 mph takeoff speed would take about 100 million J (getting it then to a cruising speed of 500 mph would be another 233 million J, but that’s pretty minor compared to the other costs). Climbing this plane to 30,000 ft would take 6.1 billion J. Resisting a drag force of 5000 pounds (about what a 737 experiences at cruising speed at 30,000 ft) for 500 miles (the distance from Cleveland to New York City) would need 17.6 billion J. Assuming landing is free (fuck TANSTAAFL) that means a typical trip needs 23.8 billion J or 6618 kWh or $1125. Assuming a real-world efficiency of 25% means the actual cost would be $4500 (which is in the ballpark of what jet fuel costs). Assuming 200 passengers, that’s $22.50 per person. Not exactly “$5 of electricity” but surprisingly small.
yeah it’s pretty crazy how much energy is in fuel.
1 kg of oil contains about 30 MJ of energy. enough to accelerate an object of the same mass to 7.7 km/s. which is almost escape velocity on earth (11.2 km/s), or enough velocity to shoot the object out of earth’s gravity field altogether.
Well, feel free to correct me on my math here, I’m no battery expert. Google says a 100 kWh battery typically weighs between 1000 and 1500 pounds. Since we’d need 6618 kWh for the hypothetical trip from Cleveland to NYC, that means we’d need 67 x 100 kWh batteries which would weigh between 67,000 and 100,000 pounds. Google also says the typical fuel load for a 737 is around 50,000 pounds, so the relative overage from batteries (since obviously you wouldn’t need to carry any fuel) would be 17,000 to 50,000 pounds. This would roughly give you a passenger capacity range between 120 and nobody. Even worse if you consider the need to have some reserves of power for unexpected circumstances. There’s also the problem mentioned elsewhere in this thread that the batteries don’t become lighter as they’re discharged, so your landing weight is the same as your takeoff weight.
So yeah, battery weight is the core problem. But if battery weight comes down by “just” 50% (and I have no idea if that’s on the horizon or not) then electric aviation becomes quite viable.
Since a plane requires the most thrust at takeoff, you could use ground-based catapults to get the plane to takeoff speed (or faster even) and then you could carry smaller batteries and propelling machinery.
Don’t you dare talk about catapulting using electric technologies in America though. Steam only! 🇺🇸🗽🦅🏈
I was about to crunch the numbers to check for myself, thanks for doing it, you did a great job.
Amazes me how they made it work considering the amount of arcane shit it takes to make jet engines work. Of course it is possible since electric motors are torque monsters, but it still must’ve taken insane efforts to make it work.
I wonder if we’ll see these flying anytime soon or if they’ll get shot down by the fossil fuel i industry just like everything else that is amazing
One important caveat to this. It costs less than 17 cents to generate 1 kwh. Closer to 3 cents really. But that’s the cost of making the electricity, getting that electricity to a house or charger or what have you costs more. Since energy is a for profit industry they tack all the logistics costs to the client buying the electricity.
So your math is spot on but I fear the amount of markup on the electricity will be massive especially since it’s for a business let alone an airline.
National average it’s 55¢ to run 3kw on 3phase electricity for an hour. Offshore areas like Hawaii and Alaska see higher costs like 1.60$/hr per 3kw on 3phase electricity but Alaska has a higher natural gas usage and Hawaii is further away from the CONUS electrical grid. National average per 24/hrs of charging is a little over 13$ with 3kw at 3phase.
All those screaming kids would get a quick education on how relatively nice everything was before the plane was launched.
“Billy, why are you crying? Do I have to take you on another plane ride? Oh, you’re gonna cry harder now? That’s it, I’m getting the vomit bags. I got this nice new child design one for you that wraps around your head and ties closed at your neck. Won’t that be a treat?”
Landing yes, it’s kinda silly to try to implement arresting cables for landing anyway. Takeoff though? If the system is broken, well then takeoff is delayed, but that wouldn’t be an emergency. Planes can’t take off all the time because of weather conditions.
Since a plane requires the most thrust at takeoff, you could use ground-based
Actually dragging (or wheeling in) a wire or having a wire car supplying the plane with electricity during takeoff would work too.
I think the only realistic use case is going to be short trips. For long range offsetting the carbon for jet fuel just makes more sense.
But really small personal vehicles could be interesting. There is the Pivotal BlackFly which can VTOL and uses less electricity than a big electric car - and it needs to roads. So for commuting this could actually work to save on infrastructure.
The biggest problem with flying cars is, well, have you seen how people drive?
It’s stressful enough just crossing the street. But at least you know when you’re doing it, look both ways, look around for idiot drivers. If there were flying cars you’d always be in danger everywhere.
Which many don’t regularly do and now added vertical dimension, more directions to look.
Can you imagine the chaos of hundreds of thousands of flying cars all trying to takeoff or land at the same time during morning and afternoon commutes. It would be glorious to witness, minus the human carnage. Even with the help of air traffic controllers there are still collisions with the current volume of air traffic. In a word, unworkable.
Two obvious solutions to traffic congestion in the US are work from home and replacing the public transport networks that automobile and oil interests dismantled.
Yeah and airplane pilots have to do a whole lot of training before they’re trusted with flying.
And yeah, 100% agree on better public transit and more WFH. We’ve developed technology to do this but somehow people insist that we should all sit in moving metal cages surrounded by six lanes of other people in their metal cages every day so we can have a Teams meeting with the person sitting next to us in the office.
Actually dragging (or wheeling in) a wire or having a wire car supplying the plane with electricity during takeoff would work too.
After doing more of the math, I realized that the energetic cost of takeoff is quite a small fraction of the overall cost. So the only real benefit of the catapult would be to reduce the size and weight of the propulsive machinery on the plane. So externally providing just the electricity wouldn’t be much of a benefit.
This is a pretty bananas idea, but I wondered if in the future we’ll be able to have something like a large robot arm “throw” a small plane from the top of a skyscraper as well as catch it for landing. Something like a modified trebuchet, slowly storing energy in a suspended weight to power throwing the plane, or to store the energy from catching the plane. We’d probably need further advances in robotics control, and the arm might need to be too heavy to be fast enough. And overall this makes even less sense than a catapult / puller that is already in use for gliders.
It will be too hard to time landings and take offs at small ports, but if you replace this with a massive flywheel you can have gearing to both spin it up on landings and draw from it to launch.
For extra fun, you could have landing planes snag a wire and use their momentum to accelerate a plane taking off.
What about Flintstones style breaks, where everyone’s legs stick out under the plane and they need to use them to stop?
Sure, it wouldn’t be effective, but one or two of these new flights being on the news and global emissions would be down even farther than with your plan.
This seemed intuitively wrong to me (like, way too low a cost), but: 25,000 pounds moving 100 mph is equal to 11,331,007 J of kinetic energy. Since 3.6 million J equals 1 kWh and 1 kWh on average costs $0.17, that means you could accelerate 25,000 pounds to reasonable bare minimum flying speed for about fifty cents (not considering efficiency of the machinery). My mind still can’t process this, but math is math.
On the other hand, looking at it from a potential energy perspective it’s a bit more expensive. 25,000 pounds at a cruising altitude of 10,000 ft. (still quite low from an airliner perspective) is about 339 million J, 94 kWh or about $16 – the cost of lunch at MacDonald’s.
Since a plane requires the most thrust at takeoff, you could use ground-based catapults to get the plane to takeoff speed (or faster even) and then you could carry smaller batteries and propelling machinery. For extra fun, you could have landing planes snag a wire and use their momentum to accelerate a plane taking off.
To save even more weight, since you’re going airport-to-airport you could leave off the landing gear and just have the planes come down on a bouncy trampoline-like surface. If you think that’s batshit crazy, the British actually experimented with this idea for their aircraft carriers in the 1950s.
Edit: to make these numbers more realistic I’m going to assume something like a 737, which can weigh something like 150,000 pounds fully loaded (this includes fuel but you’d need batteries instead for an electric plane). Getting this to a 150 mph takeoff speed would take about 100 million J (getting it then to a cruising speed of 500 mph would be another 233 million J, but that’s pretty minor compared to the other costs). Climbing this plane to 30,000 ft would take 6.1 billion J. Resisting a drag force of 5000 pounds (about what a 737 experiences at cruising speed at 30,000 ft) for 500 miles (the distance from Cleveland to New York City) would need 17.6 billion J. Assuming landing is free (fuck TANSTAAFL) that means a typical trip needs 23.8 billion J or 6618 kWh or $1125. Assuming a real-world efficiency of 25% means the actual cost would be $4500 (which is in the ballpark of what jet fuel costs). Assuming 200 passengers, that’s $22.50 per person. Not exactly “$5 of electricity” but surprisingly small.
Feel free to check my math, my brain hurts.
yeah it’s pretty crazy how much energy is in fuel.
1 kg of oil contains about 30 MJ of energy. enough to accelerate an object of the same mass to 7.7 km/s. which is almost escape velocity on earth (11.2 km/s), or enough velocity to shoot the object out of earth’s gravity field altogether.
(a kg of oil, ofc, costs about $1)
This plane can’t carry passengers. All the useful load is taxen up by batteries. It’s the fundamental issue with all-electric aviation
Well, feel free to correct me on my math here, I’m no battery expert. Google says a 100 kWh battery typically weighs between 1000 and 1500 pounds. Since we’d need 6618 kWh for the hypothetical trip from Cleveland to NYC, that means we’d need 67 x 100 kWh batteries which would weigh between 67,000 and 100,000 pounds. Google also says the typical fuel load for a 737 is around 50,000 pounds, so the relative overage from batteries (since obviously you wouldn’t need to carry any fuel) would be 17,000 to 50,000 pounds. This would roughly give you a passenger capacity range between 120 and nobody. Even worse if you consider the need to have some reserves of power for unexpected circumstances. There’s also the problem mentioned elsewhere in this thread that the batteries don’t become lighter as they’re discharged, so your landing weight is the same as your takeoff weight.
So yeah, battery weight is the core problem. But if battery weight comes down by “just” 50% (and I have no idea if that’s on the horizon or not) then electric aviation becomes quite viable.
Don’t you dare talk about catapulting using electric technologies in America though. Steam only! 🇺🇸🗽🦅🏈
I didn’t say which type of catapult. I don’t need ICE showing up at my door.
Steam melts ice! Also many wavelengths of lasers does too if you want to be modern
I was about to crunch the numbers to check for myself, thanks for doing it, you did a great job.
Amazes me how they made it work considering the amount of arcane shit it takes to make jet engines work. Of course it is possible since electric motors are torque monsters, but it still must’ve taken insane efforts to make it work.
I wonder if we’ll see these flying anytime soon or if they’ll get shot down by the fossil fuel i industry just like everything else that is amazing
One important caveat to this. It costs less than 17 cents to generate 1 kwh. Closer to 3 cents really. But that’s the cost of making the electricity, getting that electricity to a house or charger or what have you costs more. Since energy is a for profit industry they tack all the logistics costs to the client buying the electricity.
So your math is spot on but I fear the amount of markup on the electricity will be massive especially since it’s for a business let alone an airline.
National average it’s 55¢ to run 3kw on 3phase electricity for an hour. Offshore areas like Hawaii and Alaska see higher costs like 1.60$/hr per 3kw on 3phase electricity but Alaska has a higher natural gas usage and Hawaii is further away from the CONUS electrical grid. National average per 24/hrs of charging is a little over 13$ with 3kw at 3phase.
And yet it still costs me 30 dollars to charge my car in Georgia and in a state like new York it’s 60 to 100 dollars.
The entire airport is now covered in solar panels. Yes, the runway is a solar panel too.
Solar Freakin’ Runways!
Ahhh. That makes sense. I’m assuming the airplane is also just a giant flying solar panel!
Correct. You are a solar panel now too. Bon voyage!
I fucking hate everyone and would love to subject you fucks to 4g of pain taking off with a stupid catapult system. Nice math.
All those screaming kids would get a quick education on how relatively nice everything was before the plane was launched.
“Billy, why are you crying? Do I have to take you on another plane ride? Oh, you’re gonna cry harder now? That’s it, I’m getting the vomit bags. I got this nice new child design one for you that wraps around your head and ties closed at your neck. Won’t that be a treat?”
A plane should still be capable of unassisted taking off and landing for emergencies, imo.
Landing yes, it’s kinda silly to try to implement arresting cables for landing anyway. Takeoff though? If the system is broken, well then takeoff is delayed, but that wouldn’t be an emergency. Planes can’t take off all the time because of weather conditions.
And they lose spots at terminals.
Yeah same thing that happens because of weather conditions. Not an emergency.
Wouldn’t work Militarized though because you wouldn’t be able to refuel it mid flight.
Microwave beams from satellites. What could go wrong?
Actually dragging (or wheeling in) a wire or having a wire car supplying the plane with electricity during takeoff would work too.
I think the only realistic use case is going to be short trips. For long range offsetting the carbon for jet fuel just makes more sense.
But really small personal vehicles could be interesting. There is the Pivotal BlackFly which can VTOL and uses less electricity than a big electric car - and it needs to roads. So for commuting this could actually work to save on infrastructure.
The biggest problem with flying cars is, well, have you seen how people drive?
It’s stressful enough just crossing the street. But at least you know when you’re doing it, look both ways, look around for idiot drivers. If there were flying cars you’d always be in danger everywhere.
Which many don’t regularly do and now added vertical dimension, more directions to look.
Can you imagine the chaos of hundreds of thousands of flying cars all trying to takeoff or land at the same time during morning and afternoon commutes. It would be glorious to witness, minus the human carnage. Even with the help of air traffic controllers there are still collisions with the current volume of air traffic. In a word, unworkable.
Two obvious solutions to traffic congestion in the US are work from home and replacing the public transport networks that automobile and oil interests dismantled.
Yeah and airplane pilots have to do a whole lot of training before they’re trusted with flying.
And yeah, 100% agree on better public transit and more WFH. We’ve developed technology to do this but somehow people insist that we should all sit in moving metal cages surrounded by six lanes of other people in their metal cages every day so we can have a Teams meeting with the person sitting next to us in the office.
After doing more of the math, I realized that the energetic cost of takeoff is quite a small fraction of the overall cost. So the only real benefit of the catapult would be to reduce the size and weight of the propulsive machinery on the plane. So externally providing just the electricity wouldn’t be much of a benefit.
This is a pretty bananas idea, but I wondered if in the future we’ll be able to have something like a large robot arm “throw” a small plane from the top of a skyscraper as well as catch it for landing. Something like a modified trebuchet, slowly storing energy in a suspended weight to power throwing the plane, or to store the energy from catching the plane. We’d probably need further advances in robotics control, and the arm might need to be too heavy to be fast enough. And overall this makes even less sense than a catapult / puller that is already in use for gliders.
It will be too hard to time landings and take offs at small ports, but if you replace this with a massive flywheel you can have gearing to both spin it up on landings and draw from it to launch.
What about Flintstones style breaks, where everyone’s legs stick out under the plane and they need to use them to stop?
Sure, it wouldn’t be effective, but one or two of these new flights being on the news and global emissions would be down even farther than with your plan.