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From the headline I thought a high powered drone lowered a line for the swimmer to be lifted out of the water. https://www.youtube.com/watch?v=At3xcj-pTjg http

by mentos 9y ago

From the headline I thought a high powered drone lowered a line for the swimmer to be lifted out of the water. https://www.youtube.com/watch?v=At3xcj-pTjg https://www.youtube.com/watch?v=At3xcj-pTjg Casey Neistat worked with a team to create a drone capable of lifting him and his snowboard in heavy ski gear/boots. I bet you could make something like this to lift a drowning swimmer to the beach.

deleted 9y ago
[deleted]
falcolas 9y ago
One of the hurdles is that the traditional multi-rotor design doesn't scale up well. The blades just gain too much mass to be quickly sped up and slowed down. As the craft gets bigger to hold bigger payloads, more energy has to be devoted to fighting rotor momentum, making them less efficient. It's why most multirotors over a certain size use variable pitch rotors, like a helicopter. And at some point, the complexity of managing multiple variable-pitch rotors just makes the single rotor design of a helicopter more efficient; especially when it can be powered by a gas engine. Of course, a normal helicopter can be run remotely just as effectively as a multi-rotor.
- goldenkey 9y ago
  When you say 'gain more mass,' do you mean the inertia from the rotor speed? I would think the more rotors you have, the slower each can spin? Is it possible there is an efficient design we havent yet tried involving self-stabilizing bearings or ball detents? https://en.m.wikipedia.org/wiki/Ball_detent https://en.m.wikipedia.org/wiki/Ball_detent
  - falcolas 9y ago
    Intertia from both mass and speed (larger props tend to spin more slowly, at least in part to keep the tips sub-sonic). Traditional multi-rotors, like the one featured in this article, maneuver by quickly changing the speed of the props with respect to the other props to change the attitude of the craft. The larger the prop, and thus the greater the inertia, the harder it is to quickly change the rotational velocity of those rotors. Which is why helicopters tend to use variable pitch props, since they can alter the lift (and rotational force) generated by the prop without having to change the velocity. Well, that and variable pitch props let you create differential lift (such as tilting the helicopter into forward flight) with a single rotor as well. :)
- sharemywin 9y ago
  But if that rotor/engine/system goes out what keeps you in the air?
  - phillc73 9y ago
    Nothing, if only a single engine helicopter. However, many (probably all, but I don't know for sure) heavy lift or rescue helicopters are multi-engine. For example, the Westland Sea King (Powerplant: 2 × Rolls-Royce Gnome H1400-2 turboshafts, 1,660 shp (1,238 kW) each)[1] or a newer Sikorsky S-92 (Powerplant: 2 × General Electric CT7-8A turboshaft, 2,520 shp (1,879 kW) each).[2] Here's a document from the Civil Aviation Safety Authority (CASA) in Australia, concerning performance standards for multi-engine helicopters. It provides a pretty good overview of what they need to be able to do with one engine inoperative (OEI).[2] [1] https://en.wikipedia.org/wiki/Westland_Sea_King https://en.wikipedia.org/wiki/Westland_Sea_King [2] https://en.wikipedia.org/wiki/Sikorsky_S-92 https://en.wikipedia.org/wiki/Sikorsky_S-92 [3] https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/corporat/policy/notices/ceo-pn029-2005.pdf https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/...
JoeAltmaier 9y ago
I'm not sure I need another threat to my life whizzing toward me, when my life is already in danger. He's drowning! Lets sent an airborn quisinart chopper at him at high speed! Lets think again.

by mentos 9y ago

deleted 9y ago

[deleted]

falcolas 9y ago

One of the hurdles is that the traditional multi-rotor design doesn't scale up well. The blades just gain too much mass to be quickly sped up and slowed down. As the craft gets bigger to hold bigger payloads, more energy has to be devoted to fighting rotor momentum, making them less efficient. It's why most multirotors over a certain size use variable pitch rotors, like a helicopter. And at some point, the complexity of managing multiple variable-pitch rotors just makes the single rotor design of a helicopter more efficient; especially when it can be powered by a gas engine. Of course, a normal helicopter can be run remotely just as effectively as a multi-rotor.

goldenkey 9y ago
When you say 'gain more mass,' do you mean the inertia from the rotor speed? I would think the more rotors you have, the slower each can spin? Is it possible there is an efficient design we havent yet tried involving self-stabilizing bearings or ball detents? https://en.m.wikipedia.org/wiki/Ball_detent https://en.m.wikipedia.org/wiki/Ball_detent
- falcolas 9y ago
  Intertia from both mass and speed (larger props tend to spin more slowly, at least in part to keep the tips sub-sonic). Traditional multi-rotors, like the one featured in this article, maneuver by quickly changing the speed of the props with respect to the other props to change the attitude of the craft. The larger the prop, and thus the greater the inertia, the harder it is to quickly change the rotational velocity of those rotors. Which is why helicopters tend to use variable pitch props, since they can alter the lift (and rotational force) generated by the prop without having to change the velocity. Well, that and variable pitch props let you create differential lift (such as tilting the helicopter into forward flight) with a single rotor as well. :)
sharemywin 9y ago
But if that rotor/engine/system goes out what keeps you in the air?
- phillc73 9y ago
  Nothing, if only a single engine helicopter. However, many (probably all, but I don't know for sure) heavy lift or rescue helicopters are multi-engine. For example, the Westland Sea King (Powerplant: 2 × Rolls-Royce Gnome H1400-2 turboshafts, 1,660 shp (1,238 kW) each)[1] or a newer Sikorsky S-92 (Powerplant: 2 × General Electric CT7-8A turboshaft, 2,520 shp (1,879 kW) each).[2] Here's a document from the Civil Aviation Safety Authority (CASA) in Australia, concerning performance standards for multi-engine helicopters. It provides a pretty good overview of what they need to be able to do with one engine inoperative (OEI).[2] [1] https://en.wikipedia.org/wiki/Westland_Sea_King https://en.wikipedia.org/wiki/Westland_Sea_King [2] https://en.wikipedia.org/wiki/Sikorsky_S-92 https://en.wikipedia.org/wiki/Sikorsky_S-92 [3] https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/corporat/policy/notices/ceo-pn029-2005.pdf https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/...

JoeAltmaier 9y ago

I'm not sure I need another threat to my life whizzing toward me, when my life is already in danger. He's drowning! Lets sent an airborn quisinart chopper at him at high speed! Lets think again.