5 ms·

> One aircraft we looked at required 30-35MW during takeoff and ~10MW during cruise. Do you envision some airframes to include assisted take-off technology? (J

> One aircraft we looked at required 30-35MW during takeoff and ~10MW during cruise. Do you envision some airframes to include assisted take-off technology? (JATO and the like, even catapults)

mliben 6y ago
I think most forms of assisted takeoff technology would reduce electrical power requirements for takeoff, but not put much of a dent in the climb power (unless you can catapult/ JATO all the way up to cruising altitude, which would be challenging). Since climb power is still significantly higher than cruise power, and is effectively thermal steady state for these components (10-20min), it would still drive the propulsion system sizing.
- hbrav 6y ago
  You could have another aircraft tow you, like gliders sometimes do. Doesn't seem terribly practical though.
  - mliben 6y ago
    Not exactly what Talyn Air is doing, but along the same lines- separating out the "lift/climb" vehicle from the "cruise" vehicle. It can actually be a very compelling design!
  - omgwtfbyobbq 6y ago
    That could be a great use case for lighter/smaller electric motors, since a tow plane could take off, assist with takeoff, turn around and land, charge, and repeat. The tow plane wouldn't need as large of a battery pack, but having good power to weight for towing other plants to whatever altitude is very important.
    - mchusma 6y ago
      I feel like this is something that drones/100% automated ops can really help with. Power satellites (basically giant solar arrays transmitting power) are also interesting (https://www.geekwire.com/2020/space-force-will-test-solar-power-transmission-x-37b-space-planes-next-mystery-flight/ https://www.geekwire.com/2020/space-force-will-test-solar-po...). We could have these complex automated systems to make electric aircraft much more viable, which is cool in theory.
      - outworlder 6y ago
        Power satellites are interesting. But here's the thing: For most aircraft (except some gliders), covering them fully with solar panels is not even close to the power they need in cruise, correct? So a power satellite would have to generate _at least_ the same W/m2 as the sun (around 1.4kw/m2( just to break even with a solar panel, but most likely much, much more, by orders of magnitude. For a 747, I've seen figures from 90 MW to almost 200MW. If the receivers were at the wings only, that would be almost 6MW per square meter if you take the lower figure. For a target as small as a plane, this would look like an energy weapon from science fiction. Even something like this would not cut it: https://en.wikipedia.org/wiki/MIRACL https://en.wikipedia.org/wiki/MIRACL For general aircraft the numbers look better. Then again, they are much smaller. I can't wait for power satellites to be deployed, but they will mostly be servicing ground stations.
- throwawayboise 6y ago
  You still need enough reserve power at the end of a flight to do a rejected landing/go around, or you won't get certified. If you are relying on some kind of catapult, rail gun, or rocket assist to take off, not sure how that happens.
  - sokoloff 6y ago
    An early rejected landing still requires less power than a static takeoff, so you could get by with a mix of craft and assistive power.
elihu 6y ago
A simpler alternative could be to just have an electrified runway. The plane draws power from power rails embedded in a runway, or something like that. So, it doesn't switch to batteries until it's in the air. You could even have a long cable that hangs behind the plane and keeps an electrical connection until you're a few hundred feet up. (I'm picturing it connected to something like a slot-car that travels in an electrified track that could extend a mile or so past the end of the runway.) When you get to the end of the track, the cable (which could probably belong to the airport rather than be part of the plane) releases from the plane. (This would help marginally with range, but doesn't really help with power density, unless you're limited by the voltage and current available from the batteries rather than the power of the motor.) I keep wondering if there could be a way to re-charge in flight so that battery range/weight wasn't such an issue, but that's a hard problem.
- K0balt 6y ago
  None of the things you mention would have a significant effect on range, and all could be replaced with a nominal increase in runway length. If an aircraft cannot produce sufficient power to take off, it cannot produce sufficient power to climb.... And to be efficient, it must climb as high as possible, ideally to 30k feet or more. You are talking about the first 30 seconds... But it needs to keep it up for 30 minutes. Take off assists are for ultradshort runways.
- quickthrowman 6y ago
  > You could even have a long cable that hangs behind the plane and keeps an electrical connection until you're a few hundred feet up. I can assure you this will never ever happen. It’s wildly impractical, improbable, and sounds extremely unsafe. Sure, it’s theoretically possible, but that’s about it. The NFPA is not going to add a code section in the NEC for hundreds of feet long live electrical conductors being pulled into the air by a plane and then disconnected in mid-air, and the FAA isn’t going to allow it either.
  - worik 6y ago
    They allowed 737 MAX 8, so maybe, who knows?

> One aircraft we looked at required 30-35MW during takeoff and ~10MW during cruise. Do you envision some airframes to include assisted take-off technology? (JATO and the like, even catapults)

mliben 6y ago

I think most forms of assisted takeoff technology would reduce electrical power requirements for takeoff, but not put much of a dent in the climb power (unless you can catapult/ JATO all the way up to cruising altitude, which would be challenging). Since climb power is still significantly higher than cruise power, and is effectively thermal steady state for these components (10-20min), it would still drive the propulsion system sizing.

hbrav 6y ago
You could have another aircraft tow you, like gliders sometimes do. Doesn't seem terribly practical though.
- mliben 6y ago
  Not exactly what Talyn Air is doing, but along the same lines- separating out the "lift/climb" vehicle from the "cruise" vehicle. It can actually be a very compelling design!
- omgwtfbyobbq 6y ago
  That could be a great use case for lighter/smaller electric motors, since a tow plane could take off, assist with takeoff, turn around and land, charge, and repeat. The tow plane wouldn't need as large of a battery pack, but having good power to weight for towing other plants to whatever altitude is very important.
  - mchusma 6y ago
    I feel like this is something that drones/100% automated ops can really help with. Power satellites (basically giant solar arrays transmitting power) are also interesting (https://www.geekwire.com/2020/space-force-will-test-solar-power-transmission-x-37b-space-planes-next-mystery-flight/ https://www.geekwire.com/2020/space-force-will-test-solar-po...). We could have these complex automated systems to make electric aircraft much more viable, which is cool in theory.
    - outworlder 6y ago
      Power satellites are interesting. But here's the thing: For most aircraft (except some gliders), covering them fully with solar panels is not even close to the power they need in cruise, correct? So a power satellite would have to generate _at least_ the same W/m2 as the sun (around 1.4kw/m2( just to break even with a solar panel, but most likely much, much more, by orders of magnitude. For a 747, I've seen figures from 90 MW to almost 200MW. If the receivers were at the wings only, that would be almost 6MW per square meter if you take the lower figure. For a target as small as a plane, this would look like an energy weapon from science fiction. Even something like this would not cut it: https://en.wikipedia.org/wiki/MIRACL https://en.wikipedia.org/wiki/MIRACL For general aircraft the numbers look better. Then again, they are much smaller. I can't wait for power satellites to be deployed, but they will mostly be servicing ground stations.
throwawayboise 6y ago
You still need enough reserve power at the end of a flight to do a rejected landing/go around, or you won't get certified. If you are relying on some kind of catapult, rail gun, or rocket assist to take off, not sure how that happens.
- sokoloff 6y ago
  An early rejected landing still requires less power than a static takeoff, so you could get by with a mix of craft and assistive power.

elihu 6y ago

A simpler alternative could be to just have an electrified runway. The plane draws power from power rails embedded in a runway, or something like that. So, it doesn't switch to batteries until it's in the air. You could even have a long cable that hangs behind the plane and keeps an electrical connection until you're a few hundred feet up. (I'm picturing it connected to something like a slot-car that travels in an electrified track that could extend a mile or so past the end of the runway.) When you get to the end of the track, the cable (which could probably belong to the airport rather than be part of the plane) releases from the plane. (This would help marginally with range, but doesn't really help with power density, unless you're limited by the voltage and current available from the batteries rather than the power of the motor.) I keep wondering if there could be a way to re-charge in flight so that battery range/weight wasn't such an issue, but that's a hard problem.

K0balt 6y ago
None of the things you mention would have a significant effect on range, and all could be replaced with a nominal increase in runway length. If an aircraft cannot produce sufficient power to take off, it cannot produce sufficient power to climb.... And to be efficient, it must climb as high as possible, ideally to 30k feet or more. You are talking about the first 30 seconds... But it needs to keep it up for 30 minutes. Take off assists are for ultradshort runways.
quickthrowman 6y ago
> You could even have a long cable that hangs behind the plane and keeps an electrical connection until you're a few hundred feet up. I can assure you this will never ever happen. It’s wildly impractical, improbable, and sounds extremely unsafe. Sure, it’s theoretically possible, but that’s about it. The NFPA is not going to add a code section in the NEC for hundreds of feet long live electrical conductors being pulled into the air by a plane and then disconnected in mid-air, and the FAA isn’t going to allow it either.
- worik 6y ago
  They allowed 737 MAX 8, so maybe, who knows?