4 ms·

... and what exactly are you basing any of this on? Battery-powered airplanes are perfectly capable of flight. They are just inefficient for long trips.

willis936 5y ago
None of them have 20 MW to feed.
- Robotbeat 5y ago
  The largest machines humanity has built (typically mining machines) are electric. I don’t see why people think total power is the real limiting factor vs, say, specific power.
  - Tuna-Fish 5y ago
    Specific power is also not a problem. Specific energy is.
    - Robotbeat 5y ago
      Indeed, but the article is about a motor.
      - willis936 5y ago
        An aircraft motor*.
- osigurdson 5y ago
  At the upper end, the largest aircraft engines such as the GE CF6 (used in 747) produce about 40MW [1] and there are 4 of these. [1] https://en.wikipedia.org/wiki/General_Electric_LM6000 https://en.wikipedia.org/wiki/General_Electric_LM6000
  - willis936 5y ago
    The GE CF6 does not use motors for propulsion. The LM6000 is not used in aircraft because it can't be with current technology.
    - osigurdson 5y ago
      The CF6 is a gas turbine engine, not an aircraft. Virtually all aircraft engines outside of very small personal planes are gas turbines. This includes turboprops, helicopter applications, all commercial aircraft (turbofan) as well as fighter jets. The primary difference is how the thrust is used. If mechanical energy is required a power turbine is used - as is done in the LM6000. The LM6000 is the industrial version of the CF6 (the cold section is largely the same). The thrust is converted to mechanical energy using a power turbine. I included this link instead of the CF6 since it provides a direct reference to power output in MW (i.e. not thrust).
- Tuna-Fish 5y ago
  And if you just look at the state of battery tech, that does not actually look unreasonable to provide. There are commercially available high-energy cells that provide ~900W/kg. That's ~22t for the cells, round up to 30t for the other stuff. Coincidentally, that's roughly similar to the fuel capacity of an A320, to which they compared their engine power. You could push the specific power up quite a lot, but you'd have to start sacrificing specific energy, which is the sticking point of electric airplanes. With those batteries, you only get 5MWh, or you could only provide that 20MW for ~15 minutes. This is not as bad as it sounds, because airplanes only need to provide near their maximum power for relatively briefly. There are many short hop routes where that airplane can operate profitably. Still, it should make clear the point that the deficiency of electric airplanes is not their power, but their range. When you fit a plane with batteries that contain sufficient energy to go anywhere useful, you also provide it with frankly excessive power to run it's engines.
  - SigmundA 5y ago
    >There are commercially available high-energy cells that provide ~900W/kg. Can you please provide more information? My understanding is the best lithium is under 400wh/kg. Edit: Sorry looks like you are talking about power density not energy density (watts vs watt/hours). My understanding is range (energy density) is the problem not power output. Cruise takes about 1/3 the power of takeoff so maybe an hour of flight with 5 Mwh?

willis936 5y ago

None of them have 20 MW to feed.

Robotbeat 5y ago
The largest machines humanity has built (typically mining machines) are electric. I don’t see why people think total power is the real limiting factor vs, say, specific power.
- Tuna-Fish 5y ago
  Specific power is also not a problem. Specific energy is.
  - Robotbeat 5y ago
    Indeed, but the article is about a motor.
    - willis936 5y ago
      An aircraft motor*.
osigurdson 5y ago
At the upper end, the largest aircraft engines such as the GE CF6 (used in 747) produce about 40MW [1] and there are 4 of these. [1] https://en.wikipedia.org/wiki/General_Electric_LM6000 https://en.wikipedia.org/wiki/General_Electric_LM6000
- willis936 5y ago
  The GE CF6 does not use motors for propulsion. The LM6000 is not used in aircraft because it can't be with current technology.
  - osigurdson 5y ago
    The CF6 is a gas turbine engine, not an aircraft. Virtually all aircraft engines outside of very small personal planes are gas turbines. This includes turboprops, helicopter applications, all commercial aircraft (turbofan) as well as fighter jets. The primary difference is how the thrust is used. If mechanical energy is required a power turbine is used - as is done in the LM6000. The LM6000 is the industrial version of the CF6 (the cold section is largely the same). The thrust is converted to mechanical energy using a power turbine. I included this link instead of the CF6 since it provides a direct reference to power output in MW (i.e. not thrust).
Tuna-Fish 5y ago
And if you just look at the state of battery tech, that does not actually look unreasonable to provide. There are commercially available high-energy cells that provide ~900W/kg. That's ~22t for the cells, round up to 30t for the other stuff. Coincidentally, that's roughly similar to the fuel capacity of an A320, to which they compared their engine power. You could push the specific power up quite a lot, but you'd have to start sacrificing specific energy, which is the sticking point of electric airplanes. With those batteries, you only get 5MWh, or you could only provide that 20MW for ~15 minutes. This is not as bad as it sounds, because airplanes only need to provide near their maximum power for relatively briefly. There are many short hop routes where that airplane can operate profitably. Still, it should make clear the point that the deficiency of electric airplanes is not their power, but their range. When you fit a plane with batteries that contain sufficient energy to go anywhere useful, you also provide it with frankly excessive power to run it's engines.
- SigmundA 5y ago
  >There are commercially available high-energy cells that provide ~900W/kg. Can you please provide more information? My understanding is the best lithium is under 400wh/kg. Edit: Sorry looks like you are talking about power density not energy density (watts vs watt/hours). My understanding is range (energy density) is the problem not power output. Cruise takes about 1/3 the power of takeoff so maybe an hour of flight with 5 Mwh?