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Relevant: "Why haven't quadcopters been scaled up yet?"[1] The gist is, scaling up multi-rotor systems isn't as simple as making things bigger - the size adds

by Alupis 9y ago

Relevant: "Why haven't quadcopters been scaled up yet?"[1] The gist is, scaling up multi-rotor systems isn't as simple as making things bigger - the size adds many issues that the small models don't face (models having nearly impossible performance characteristics compared to full scale versions). Also, there's safety issues regarding controlling such as system when one or more rotors/motors fail. It's not to say it cannot be done, because obviously it can. It's a question of "why?", when there's clearly better, more simple and efficient ways to get around. Also, battery power density (and weight) has a long way to go before it will match Kerosene, or even regular AvGas - "Could an electric engine provide the same performance as jet engines on current aircraft?"[2]. [1] https://aviation.stackexchange.com/questions/3300/why-havent-quadcopters-been-scaled-up-yet https://aviation.stackexchange.com/questions/3300/why-havent... [2] https://aviation.stackexchange.com/questions/26910/could-an-electric-engine-provide-the-same-performance-as-jet-engines-on-current https://aviation.stackexchange.com/questions/26910/could-an-...

ChuckMcM 9y ago
> It's not to say it cannot be done, because obviously it can. It's a question of "why?", when there's clearly better, more simple and efficient ways to get around. I observe that in spite of the 'simple and efficent' ways to get around there is a tremendous amount of capital being invested to find new transportation modalities. Perhaps one or more of those investments will surprise you.
- Alupis 9y ago
  There are two things that a full-sized electric multi-rotor vehicle must contend with to be practical: 1) Battery power density must have a tremendous breakthrough, in both terms of weight and stored capacity. 2) Electric motors capable of producing the energies required to produce the thrust necessary to propel a full-sized vehicle must also have a tremendous breakthrough in size, weight, and heat dissipation (especially if we're discussing vehicles capable of typical cruise altitudes over long distances). It would be far more simple and efficient to make a full-sized Kerosene, AvGas, or any other petroleum-based fuel multi-rotor vehicle... but then you must also overcome the unnecessary challenges multi-rotor systems introduce at this scale. Which... leads back to today's average helicopter and airplane designs. Like I said, it's not impossible... it's just not practical for these reasons. If someone wants to do it, they can... obviously... but it's not the most effective way. > Perhaps one or more of those investments will surprise you Indeed, people often invest in some very surprising ideas... sometimes even without really understanding what they are getting into...[1] [1] https://aviation.stackexchange.com/questions/33541/are-fixed-wing-aircraft-with-gimbal-thrust-feasible/33542#33542 https://aviation.stackexchange.com/questions/33541/are-fixed...
  - ChuckMcM 9y ago
    And all I'm saying is that you are looking backwards to guess what will happen in front of you. Historically when people have done that, they have been surprised by what came next.
    - Alupis 9y ago
      You're absolutely right... but it's important we put faith into feasible ideas instead of chasing down fun, but terribly unproductive and/or unsafe ideas... and also obey the laws of physics. Differentiating between the two is sometimes difficult, especially when people, generally, want to "believe" in a fantastical vision of tomorrow.
      - ChuckMcM 9y ago
        > 2) Electric motors capable of producing the energies required to produce the thrust necessary to propel a full-sized vehicle must also have a tremendous breakthrough in size, weight, and heat dissipation (especially if we're discussing vehicles capable of typical cruise altitudes over long distances). This one had me wondering, especially since one of the reasons that model quadcopters even exist is because of breakthroughs in brushless motors which have good power to weight ratios for things that fly. So trying to compare a state of the art helicopter engine and a state of the art brushless motor lead me down this path ... It is notoriously difficult to get details out of Tesla but according to this: https://chargedevs.com/newswire/elon-musk-cooling-not-power-to-weight-ratio-is-the-challenge-with-ac-induction-motors/ https://chargedevs.com/newswire/elon-musk-cooling-not-power-... the Model S electric motor is 362 bhp at a weight of 70 lbs (5.2 HP/lb), and according to this: https://www.geaviation.com/sites/default/files/datasheet-T700-401C-701C.pdf https://www.geaviation.com/sites/default/files/datasheet-T70... the engine used in the AH-64 Apache is 1662 shp at a weight of 458 lbs (3.62 HP/lb). The point about cooling is well taken (Elon mentions it as a challenge) however in both model airplanes and quadcopters the motor typically is mount directly under the rotor so that not only does the prop wash provide the lift for the craft, it provides a lot of cooling for the motor driving it. Again, not saying that you're wrong or that I'm right, I'm just saying that things are changing rapidly, people are investing in that change, and that is a recipe for surprising results.

by Alupis 9y ago

ChuckMcM 9y ago

> It's not to say it cannot be done, because obviously it can. It's a question of "why?", when there's clearly better, more simple and efficient ways to get around. I observe that in spite of the 'simple and efficent' ways to get around there is a tremendous amount of capital being invested to find new transportation modalities. Perhaps one or more of those investments will surprise you.

Alupis 9y ago
There are two things that a full-sized electric multi-rotor vehicle must contend with to be practical: 1) Battery power density must have a tremendous breakthrough, in both terms of weight and stored capacity. 2) Electric motors capable of producing the energies required to produce the thrust necessary to propel a full-sized vehicle must also have a tremendous breakthrough in size, weight, and heat dissipation (especially if we're discussing vehicles capable of typical cruise altitudes over long distances). It would be far more simple and efficient to make a full-sized Kerosene, AvGas, or any other petroleum-based fuel multi-rotor vehicle... but then you must also overcome the unnecessary challenges multi-rotor systems introduce at this scale. Which... leads back to today's average helicopter and airplane designs. Like I said, it's not impossible... it's just not practical for these reasons. If someone wants to do it, they can... obviously... but it's not the most effective way. > Perhaps one or more of those investments will surprise you Indeed, people often invest in some very surprising ideas... sometimes even without really understanding what they are getting into...[1] [1] https://aviation.stackexchange.com/questions/33541/are-fixed-wing-aircraft-with-gimbal-thrust-feasible/33542#33542 https://aviation.stackexchange.com/questions/33541/are-fixed...
- ChuckMcM 9y ago
  And all I'm saying is that you are looking backwards to guess what will happen in front of you. Historically when people have done that, they have been surprised by what came next.
  - Alupis 9y ago
    You're absolutely right... but it's important we put faith into feasible ideas instead of chasing down fun, but terribly unproductive and/or unsafe ideas... and also obey the laws of physics. Differentiating between the two is sometimes difficult, especially when people, generally, want to "believe" in a fantastical vision of tomorrow.
    - ChuckMcM 9y ago
      > 2) Electric motors capable of producing the energies required to produce the thrust necessary to propel a full-sized vehicle must also have a tremendous breakthrough in size, weight, and heat dissipation (especially if we're discussing vehicles capable of typical cruise altitudes over long distances). This one had me wondering, especially since one of the reasons that model quadcopters even exist is because of breakthroughs in brushless motors which have good power to weight ratios for things that fly. So trying to compare a state of the art helicopter engine and a state of the art brushless motor lead me down this path ... It is notoriously difficult to get details out of Tesla but according to this: https://chargedevs.com/newswire/elon-musk-cooling-not-power-to-weight-ratio-is-the-challenge-with-ac-induction-motors/ https://chargedevs.com/newswire/elon-musk-cooling-not-power-... the Model S electric motor is 362 bhp at a weight of 70 lbs (5.2 HP/lb), and according to this: https://www.geaviation.com/sites/default/files/datasheet-T700-401C-701C.pdf https://www.geaviation.com/sites/default/files/datasheet-T70... the engine used in the AH-64 Apache is 1662 shp at a weight of 458 lbs (3.62 HP/lb). The point about cooling is well taken (Elon mentions it as a challenge) however in both model airplanes and quadcopters the motor typically is mount directly under the rotor so that not only does the prop wash provide the lift for the craft, it provides a lot of cooling for the motor driving it. Again, not saying that you're wrong or that I'm right, I'm just saying that things are changing rapidly, people are investing in that change, and that is a recipe for surprising results.