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To my understanding the reason helicopters are expensive is the cost of acquiring and operating the airframe. I would imagine a scaled up drone-like airframe w

by fsloth 8y ago

To my understanding the reason helicopters are expensive is the cost of acquiring and operating the airframe. I would imagine a scaled up drone-like airframe would be a lot more cheaper than helicopter. That's why I don't think "drones as flying taxis" is as silly as you make it sound. Helicopters are used in urban areas. I don't see any fundamental reason why drones would not work equally well but with more traffic since they would be cheaper. Like you point out, the unguarded props and so on mean it wouldn't be sharing ground-space with pedestrians - not at least like cars do. Unless.. I don't know if there any way to do an emergency stop to a large scale electric prop. At least power saws stop instantly to stop cutting limbs away. Maybe there could be a similar "proximity failsafe" in the props of urban taxi-drones.

supermatt 8y ago
Power saws don't stop instantly. There is a massive amount of energy in those spinning disks. There are some safety mechanisms available (atypically) that use explosive charges to move the blade away and/or physically destroy it (in the case of table saws), but you cant simply stop something with that much momentum.
- ljf 8y ago
  /some/ power saws can stop instantly - if you try and touch this one with a finger it will stop before it can do damage: https://www.youtube.com/watch?v=eiYoBbEZwlk https://www.youtube.com/watch?v=eiYoBbEZwlk
  - Balero 8y ago
    The method these use, retracting the blade, and jamming it into a block of metal to stop the momentum would not work on a aircraft. This method (whilst pretty amazing) does not work outside of a static machine. You would need a couple of tons of metal attached to each rotor, and thats before getting into what would happen when you actually try and stop the rotor.
    - jacobush 8y ago
      I am sure it could be made to work. Some kind of shroud designed to crumble in the right way, maybe start rotating itself partly. Not tons of metal. But of course, it would make the airframe a heavier and you'd pay a cost for all flights.
  - falcolas 8y ago
    At a cost. There are several consumable components involved that have to be replaced every time it goes off. And it's less that the saw is stopped instantly which prevents the damage, but that it's explosively retracted away from the finger and then stopped. And, as lamented by many wood workers, damp wood can set it off as well. Of course, that's a small price to pay in some cases.
nradov 8y ago
Why would you imagine a scaled up drone-like airframe would be a lot cheaper than a conventional helicopter? Have you actually analyzed the costs and engineering trade-offs?
- fsloth 8y ago
  No, I haven't. I would love to see some actual numbers. I imagined a quadrocopter-like air taxi would have a lower total cost of ownership than a helicopter because: * Toy-scale electric quadrocopters are cheap as dirt and all aspects of that platform are totally commoditized. * Electric vehicles should be cheaper to operate and maintain than corresponding combustion vehicles * I imagine a quadrocopter system would be easier to modularize and platformize than a helicopter system given the fair simplicity and disconnectedness of various components. This should lead to better economies of scale . I don't see why the total commoditization we see in "toy" quadrocopter components would not spread to larger vehicles once they mature. But, I don't know. I would love to hear the opinion of someone who is better informed than me.
  - nradov 8y ago
    Those things don't scale up. What works in a toy won't work in a larger aircraft. Look at rotor disk loading versus power efficiency for example. To gain a better intuitive understanding of the problem, consider why we can't use selective breeding to create a mouse the size of a horse.
    - fsloth 8y ago
      Sure, the mechanical components don't scale up. I wasn't referring to upscaling a toy drone. But, if - and it's an if until someone actually solves all the problems - someone comes up with an electric airframe that works well enough for personal transportation - then I think it's more likely than not to have economies of scale to kick in and drive the cost down together with commoditization of personal flight. Sure, there are lot of if's there. But mainly my guess "an electric 'quadrocopter' will be cheaper for personal transport than helicopter" is based on two things: * it will become popular, hence driving unit costs down * the vehicle will be cheaper to operate than a combustion engine powered helicopter
tomatotomato37 8y ago
What exactly do you think the differences are between a helicopter and drone airframe? They're both unibody constructs built for lightness that are designed to accommodate cargo/passengars via some active lift system; calling it a different name doesn't make it a disruptive technology
taneq 8y ago
To be clear - I wasn't saying manned multirotors are an impossible dream. I'd love to someday build one myself. They're not practical transportation (yet!) though, for a bunch of reasons: - Carrying capacity is very limited. The best current tech is at its limit getting one human off the ground for a few minutes, doing better will need magic batteries from the future - Multirotors using fixed pitch rotors need to vary the rotor speed rapidly to control the thrust and torque of the rotors, and you can't do that fast with big rotors (the rotors on this thing are already too big to control efficiently like this) - Variable pitch rotors add too much weight and complexity, if you're going variable pitch you might as well just build a helicopter (and if this thing's using variable pitch it still doesn't have enough rotors to survive a single failure unless it has well over 2:1 max lift to weight ratio so you've gone from one critical point of failure on a helicopter to 4+ just on the rotors for this thing) - Rotorcraft efficiency (lift per kW of power) is determined by disc loading, which means you need a ton of small rotors for a useful amount of lift with non-bonkers power usage (this thing's dual coaxial rotors are way too small to be efficient) - A rotorcraft with a ton of small rotors (https://www.volocopter.com/en/product/ https://www.volocopter.com/en/product/ say) is going to have a ton of complexity and a high failure rate, this is actually an advantage of multirotors since (with enough rotors and enough spare power) they can tolerate single failures so you won't crash but your rotorcraft is still going to need fixing regularly Helicopters aren't as expensive as they are because the airframe is expensive (it's just fibreglass usually) or even because the powertrain is expensive (it is though). They're expensive because they're regulated to hell and back by the FAA or your local equivalent and require exhaustive certifications, maintenance etc. You could build a helicopter for $10k in your back shed but good luck getting permission to fly it at all, much less as a taxi service, MUCH less over people's houses. (All this is just my understanding, I'm not an aeronautical engineer, just someone who loves rotorcraft. :P )

by fsloth 8y ago

supermatt 8y ago

Power saws don't stop instantly. There is a massive amount of energy in those spinning disks. There are some safety mechanisms available (atypically) that use explosive charges to move the blade away and/or physically destroy it (in the case of table saws), but you cant simply stop something with that much momentum.

ljf 8y ago
/some/ power saws can stop instantly - if you try and touch this one with a finger it will stop before it can do damage: https://www.youtube.com/watch?v=eiYoBbEZwlk https://www.youtube.com/watch?v=eiYoBbEZwlk
- Balero 8y ago
  The method these use, retracting the blade, and jamming it into a block of metal to stop the momentum would not work on a aircraft. This method (whilst pretty amazing) does not work outside of a static machine. You would need a couple of tons of metal attached to each rotor, and thats before getting into what would happen when you actually try and stop the rotor.
  - jacobush 8y ago
    I am sure it could be made to work. Some kind of shroud designed to crumble in the right way, maybe start rotating itself partly. Not tons of metal. But of course, it would make the airframe a heavier and you'd pay a cost for all flights.
- falcolas 8y ago
  At a cost. There are several consumable components involved that have to be replaced every time it goes off. And it's less that the saw is stopped instantly which prevents the damage, but that it's explosively retracted away from the finger and then stopped. And, as lamented by many wood workers, damp wood can set it off as well. Of course, that's a small price to pay in some cases.

nradov 8y ago

Why would you imagine a scaled up drone-like airframe would be a lot cheaper than a conventional helicopter? Have you actually analyzed the costs and engineering trade-offs?

fsloth 8y ago
No, I haven't. I would love to see some actual numbers. I imagined a quadrocopter-like air taxi would have a lower total cost of ownership than a helicopter because: * Toy-scale electric quadrocopters are cheap as dirt and all aspects of that platform are totally commoditized. * Electric vehicles should be cheaper to operate and maintain than corresponding combustion vehicles * I imagine a quadrocopter system would be easier to modularize and platformize than a helicopter system given the fair simplicity and disconnectedness of various components. This should lead to better economies of scale . I don't see why the total commoditization we see in "toy" quadrocopter components would not spread to larger vehicles once they mature. But, I don't know. I would love to hear the opinion of someone who is better informed than me.
- nradov 8y ago
  Those things don't scale up. What works in a toy won't work in a larger aircraft. Look at rotor disk loading versus power efficiency for example. To gain a better intuitive understanding of the problem, consider why we can't use selective breeding to create a mouse the size of a horse.
  - fsloth 8y ago
    Sure, the mechanical components don't scale up. I wasn't referring to upscaling a toy drone. But, if - and it's an if until someone actually solves all the problems - someone comes up with an electric airframe that works well enough for personal transportation - then I think it's more likely than not to have economies of scale to kick in and drive the cost down together with commoditization of personal flight. Sure, there are lot of if's there. But mainly my guess "an electric 'quadrocopter' will be cheaper for personal transport than helicopter" is based on two things: * it will become popular, hence driving unit costs down * the vehicle will be cheaper to operate than a combustion engine powered helicopter

tomatotomato37 8y ago

What exactly do you think the differences are between a helicopter and drone airframe? They're both unibody constructs built for lightness that are designed to accommodate cargo/passengars via some active lift system; calling it a different name doesn't make it a disruptive technology

taneq 8y ago

To be clear - I wasn't saying manned multirotors are an impossible dream. I'd love to someday build one myself. They're not practical transportation (yet!) though, for a bunch of reasons: - Carrying capacity is very limited. The best current tech is at its limit getting one human off the ground for a few minutes, doing better will need magic batteries from the future - Multirotors using fixed pitch rotors need to vary the rotor speed rapidly to control the thrust and torque of the rotors, and you can't do that fast with big rotors (the rotors on this thing are already too big to control efficiently like this) - Variable pitch rotors add too much weight and complexity, if you're going variable pitch you might as well just build a helicopter (and if this thing's using variable pitch it still doesn't have enough rotors to survive a single failure unless it has well over 2:1 max lift to weight ratio so you've gone from one critical point of failure on a helicopter to 4+ just on the rotors for this thing) - Rotorcraft efficiency (lift per kW of power) is determined by disc loading, which means you need a ton of small rotors for a useful amount of lift with non-bonkers power usage (this thing's dual coaxial rotors are way too small to be efficient) - A rotorcraft with a ton of small rotors (https://www.volocopter.com/en/product/ https://www.volocopter.com/en/product/ say) is going to have a ton of complexity and a high failure rate, this is actually an advantage of multirotors since (with enough rotors and enough spare power) they can tolerate single failures so you won't crash but your rotorcraft is still going to need fixing regularly Helicopters aren't as expensive as they are because the airframe is expensive (it's just fibreglass usually) or even because the powertrain is expensive (it is though). They're expensive because they're regulated to hell and back by the FAA or your local equivalent and require exhaustive certifications, maintenance etc. You could build a helicopter for $10k in your back shed but good luck getting permission to fly it at all, much less as a taxi service, MUCH less over people's houses. (All this is just my understanding, I'm not an aeronautical engineer, just someone who loves rotorcraft. :P )