this is super interesting! are you planning on working with an experimental manufacturer? would love to see this running on an Sling TSi or RV-10 similar GA airplane.
Launch HN: H3X (YC W21) – High power density electric aircraft motors
141–150 of 169 posts
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#142How do you compare with Magnax?
Also: We're developing high energy density battery packs (cells of 400wh/kg+, packs at 300-350wh/kg), might be interesting to team up. Hit me up on LinkedIn: Bernd Rietberg.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#143Earlier quoted context omitted.
> Given that the batteries weigh a lot more than the motors, I would have thought that motor efficiency (which scales battery size) was much more important than motor weight. I guess that depends on what kind of airplane you are making. If you're just making the same kind of airplanes we've been making with ICE, but with electric motors and batteries instead, you're probably right. But if you're making an electric ai…
These are all great points- everything is very interconnected in these vehicles, and there is a lot of potential upside in high power density distributed propulsion (like on the Maxwell). In characterizing the vehicle-level benefit of power density, it is definitely important to consider the X kg of structure required to support 1 kg of motor/inverter/gearbox/etc.
Excellent points about associated structures! However for the motors, isn't it the case that the support structure design is dominated by the thrust loads, which should vastly exceed the motor mass? For sure, there is some non-thrust-related structure to react the motor's mass, e.g., inertia from a harsh landing, but how much extra is it? This is much more the case with power/mass optimized motors like yours.
Consider an ideal case - you achieve the same power with negligible mass, say 1kg. How much structure in my aircraft using your motor could I really eliminate vs your current model?
And the real case, switching from a competitor's similar-power motor to yours, how much additional structure weight can I save by switching, beyond the obvious great advantage of your motor's weight savings?
(Obviously, these answers massively depend on other factors, but... )
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#144Earlier 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…
But that big max/cruise delta disappears as soon as you ditch the wings and go 'copter, which seem to dominate all use cases where electric is anywhere close to viable. Where motors excelling in W/g could absolutely shine is the still empty area of hybrid planes that downsize their combustive propulsion to cruise requirements and carry batteries only for those short periods of peak power demand.
Would you use a generator or a directly connected ICE?
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#145Earlier quoted context omitted.
Yes, the range-optimal speed is where the parasitic drag is equal to the lift-induced drag. If you go through the analysis, the air density drops out of the range equation if you assume are operating at the range-optimal speed (which is higher at lower air densities).
> the range-optimal speed is where the parasitic drag is equal to the lift-induced drag Not quite true -- range-optimal speed is where the sum of those terms is minimal. With some assumptions, this is where the derivative is 0, dDrag/dv = 0, and since derivative is linear, this means: the range-optimal speed is where the (infinitesimal) increase of parasitic drag (with speed) is equal to the decrease of lift-induced…
Using the simple drag polar approach,
D = A*v^2 + B/v^2 (D is total drag, first term is parasitic drag, second term is lift-induced drag)
dD/dv = 0 where v = (B/A)^(1/4)
Plug in v = (B/A)^(1/4)
D = sqrt(AB) + sqrt(AB), aka dD/dv = 0 exactly when parasitic drag is equal to the lift-induced drag
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#146Earlier quoted context omitted.
Is the scale of the engine for marine applications very different to aviation? Ferries usually have huge hulking diesels so I'm curious what the equivalent electric powertrain is like. I'm also assuming that a scaled down version would be ideal for personal watercraft?
In marine use, as a former ship driver (naval, not commercial, so needs could vary), I would prefer a larger number of small engines I can vector rather than one or two larger engines. It removes the need for tugs from both the maneuverability standpoint since you have vectoring and the safety standpoint since you could have redundant systems.
Now that makes a lot of sense. Unlike side thrusters, you'd be able to use all engines to provide forward movement for max speed while also using the same engines for low speed maneuvering.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#147Earlier quoted context omitted.
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…
As a rule, whenever one feels tempted to say "just do ", it's time to wait and think. Because, if it's "just" about doing something, why isn't it being done already? In this case: let's say it's feasible to retrofit runways to use this system (it probably isn't) and look at a few issues. For instance: "the cable releases from the plane". No system is fail safe. What happens if the cable does NOT release from the plan…
Yeah....you can just change this screen a little bit to....two weeks of design sessions ensue.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#148First 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!
Yeah...GE is ripe for the poaching and it wouldn't be difficult to convince them to join you. GE is being left behind (they are irreversibly way behind in mfg and have no capacity for new engine development)...fast...and it is making long time employees nervous. I was in aviation there until recently and there was zero talk of electric engines...at all...while competitors and customers were seen building their own.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#149Earlier quoted context omitted.
These are all great points- everything is very interconnected in these vehicles, and there is a lot of potential upside in high power density distributed propulsion (like on the Maxwell). In characterizing the vehicle-level benefit of power density, it is definitely important to consider the X kg of structure required to support 1 kg of motor/inverter/gearbox/etc.
Excellent points about associated structures! However for the motors, isn't it the case that the support structure design is dominated by the thrust loads, which should vastly exceed the motor mass? For sure, there is some non-thrust-related structure to react the motor's mass, e.g., inertia from a harsh landing, but how much extra is it? This is much more the case with power/mass optimized motors like yours. Conside…
Yeah, there are a lot of factors that play into this. A couple things come to mind:
1) Considering megawatt-class machines are necessary for many future applications, the mass of the motor+inverter+gearbox (especially using best current technology) definitely adds up.
2) With a very distributed propulsion system, motors that end up near the wing tips have a big moment arm compared to the ones typically tucked under the wing root
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#150Earlier quoted context omitted.
Yes, thermal conductivity is of the utmost importance at the continuous current densities we are designing for. That being said, typically the effective thermal conductivity of the winding (perpendicular to the axis of current flow) is limited by the insulation (strand and/or turn) and the encapsulation/varnish. As a result, changing the thermal conductivity of the conductors themselves will have much less impact on…
It’s just a weird idea, but cant you use hollow copper winding, and run the coolant liquid trough that?
Yes, this is one variation of what is referred to as "in-slot cooling". Keep in mind that putting coolant inside the slot removes precious conductor cross-sectional area. There is a tradeoff to be analyzed, and in some situations it can make sense. However, in-slot cooling does lock you in to having a liquid cooling system, whereas the design we currently use (coolant channels integrated into shared housing) could be modified to be air-cooled if it makes sense to do so.