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.
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.
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.
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 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! 🇺🇸🗽🦅🏈
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.
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.
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?”
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.
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.
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.
The entire airport is now covered in solar panels. Yes, the runway is a solar panel too.
Ahhh. That makes sense. I’m assuming the airplane is also just a giant flying solar panel!
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.
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
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.
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.
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?”
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.