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> The good thing is we don’t really need anything better than lithium ion for most applications (aerospace excluded). I highly doubt that you can achieve decen

by danaos 8y ago

> The good thing is we don’t really need anything better than lithium ion for most applications (aerospace excluded). I highly doubt that you can achieve decent flight times on battery powered plane. The extra battery weight is managed by increasing wing size which in turn translates to higher drag. Higher drag is compensated by more power meaning bigger batteries. It's an engineering nightmare.

philwelch 8y ago
Yeah, I looked into this a bit. Planes and rockets absolutely require expendable fuel to achieve efficiency; the ratio of wet to dry mass provides an exponential factor to either flight range or delta-V by virtue of lowering weight as it provides thrust. A lighter flying thing can use less thrust to counteract its own weight (indirectly by generating lift in some cases) thus making its remaining fuel more efficient. This is why the Saturn V had an absolutely gargantuan booster stage, followed by a large booster, then a small booster, and finally a tiny Apollo CSM to actually get to the moon and back. Lifting a rocket itself requires an exponentially bigger market just to get you a few km further off the ground. For planes it’s arguably worse because a plane in level flight thrusts forward and relies on that to indirectly provide lift, whereas weight is always pulling straight down. Also, thrusting forward creates drag backwards.
- pauljurczak 8y ago
  > Planes and rockets absolutely require expendable fuel to achieve efficiency This may change for planes soon: https://www.eviation.co/ https://www.eviation.co/
audunw 8y ago
It should be mentioned that electric motors allow for designs which can drastically lower drag. See NASA X-57 Maxwell for instance. But it will take quite some time for that to translate to commercially made planes. I think the key to electric flight is just a rough doubling of battery capacity, along with finishing the R&D around new designs like the X-57. Nothing that's out of the reach in the near future. A doubling of capacity can be achieved with lithium using either solid state electrolytes or silicon anodes. There's a decent chance that something like that will reach mass production in the next 10 years.

by danaos 8y ago

philwelch 8y ago

Yeah, I looked into this a bit. Planes and rockets absolutely require expendable fuel to achieve efficiency; the ratio of wet to dry mass provides an exponential factor to either flight range or delta-V by virtue of lowering weight as it provides thrust. A lighter flying thing can use less thrust to counteract its own weight (indirectly by generating lift in some cases) thus making its remaining fuel more efficient. This is why the Saturn V had an absolutely gargantuan booster stage, followed by a large booster, then a small booster, and finally a tiny Apollo CSM to actually get to the moon and back. Lifting a rocket itself requires an exponentially bigger market just to get you a few km further off the ground. For planes it’s arguably worse because a plane in level flight thrusts forward and relies on that to indirectly provide lift, whereas weight is always pulling straight down. Also, thrusting forward creates drag backwards.

pauljurczak 8y ago
> Planes and rockets absolutely require expendable fuel to achieve efficiency This may change for planes soon: https://www.eviation.co/ https://www.eviation.co/

audunw 8y ago

It should be mentioned that electric motors allow for designs which can drastically lower drag. See NASA X-57 Maxwell for instance. But it will take quite some time for that to translate to commercially made planes. I think the key to electric flight is just a rough doubling of battery capacity, along with finishing the R&D around new designs like the X-57. Nothing that's out of the reach in the near future. A doubling of capacity can be achieved with lithium using either solid state electrolytes or silicon anodes. There's a decent chance that something like that will reach mass production in the next 10 years.