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Launch HN: H3X (YC W21) – High power density electric aircraft motors

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Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#61

Post by mliben »

tin7in wrote: post #51

An interesting anecdote I listen to during a conference on eVTOL. A long flight with an electrified 747 will require more power from the grid than Heathrow's electricity consumption for half a day.

Certainly. Infrastructure is actually one of the biggest technological challenges for flight electrification. This is one area where hydrogen / fuel cell might have a leg up since it can physically/geographically decouple the power distribution from the airport itself (whereas for battery electric, unless you want to swap tens of tons of batteries between flights, you need charging infrastructure at the airport itself- and charging many 747-sized planes simultaneously at C-rates of at least 1 would require an obscene amount of power).

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#62

Post by mliben »

balfirevic wrote: post #58

If you don't mind sharing - what is the airgap diameter (presuming it's a radial flux motor)?

For our technology demonstrator, we have a pretty small rotor. Future direct drive designs (typically higher power as well) will have much larger diameters.

I can't be too specific, but you can probably get an idea of the rotor size from the preliminary datasheet (and/or CAD model) that you can download from our website. We have dimensions of the outside of the unit. Remember that the inverter is in there as well!

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#63

Post by jjsylvestre »

fallingmeat wrote: post #57

First hires should be people with strong SAE-ARP4754A and SAE-ARP4761 experience. Get your safety assessment correct first. Understand how to build a FADEC function with appropriate development assurance and hardware reliability. Then build your extended team (or outsource). Good luck!

Absolutely. Appreciate the advice Nate!

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#65

Post by elihu »

mercurywells wrote: post #8
jjsylvestre wrote: post #7

Earlier quoted context omitted.

This is an excellent question. For narrow body aircraft we've studied, they require high propulsive power during the takeoff and climb phases, and a fraction of the peak propulsive power during the cruise phase. One aircraft we looked at required 30-35MW during takeoff and ~10MW during cruise. So, thrust power and system level power density (kW/kg) are critical during takeoff/climb and cruise efficiency is important…

> 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)

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.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#66

Post by thescriptkiddie »

Electric passenger aircraft are not and will never be viable, but I would sure like to see super lightweight electric sustainer motors for gliders. Paired with regenerative braking and/or solar cells on the wings you could probably keep a glider in the air indefinitely.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#67

Post by baybal2 »

A trick question. How heavy is your gearbox, and not a motor?

Getting ridiculous power to weight ratios on electric power is not that hard if you opt for super high RPMs.

By my standards, what matters in electric motors are their torque per weight.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#68

Post by luplex »

bob29 wrote: post #64

Is there an analog for regenerative braking in the flying EV world?

Interesting question! On helicopters, you can use autorotation to land safely even when your engine broke.

On planes, I'm not so sure. I suspect most of the braking forces while flying come from the drag of the normal plane body, so you can't really capture them.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#69

Post by baybal2 »

mliben wrote: post #56
airbreather wrote: post #42

I have more questions, why are you not using silver, around 106% better conductance of electricity, but also a better conductor of heat? And cooling, lots of big electrical plant uses H2 for a cooling medium as it has about 22 times better heat transfer than air - I can see the peroblems, but you can't light up 100% H2, it's when it gets some air with it is the problem. I actually have a bucket load more, I am Elec E…

Silver is crazy expensive compared to copper, and the tradeoff isn't worth 6%. Also, 3d-printing pure copper is relatively new, and I'm not sure there is as much of a business case for 3d-printing silver (from the perspective of the companies making these metal AM machines), since the demand is lower because of the cost. Lastly, there are actually some loss mechanisms in the motor where the lower resistivity of silve…

Silver is heavier than copper.

That's why people were so upset when carbon nanotube yarns happened to be poor conductors.

People were thinking of super light motor windings.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#70

Post by quickthrowman »

elihu wrote: post #65
mercurywells wrote: post #8

Earlier quoted context omitted.

> 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)

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 el…

> 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.

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