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.
Launch HN: H3X (YC W21) – High power density electric aircraft motors
51–60 of 169 posts
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#52Earlier 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.
Don’t many modern ships already have this? I recall watching “Big Ships” or some such on
Discovery Channel about 15-20 years ago where they explained ships already having multiple stern and aft, starboard and port, “pods” either with jet streams or rotors.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#53Oh I've got many questions :) 1- Isn't a HW startup really hard compared to software? Like the ideas are like yet-another-social-media-site or a SASS but in hw one needs to do the embedded programming, the mechanical design, the software, marketing and *then* the novel idea that sells. How do you do it? 2- How do you manage to find the expertise to build a viable product? How did you find investors? 3- Any tips/books…
1. There are parts that are certainly harder and there is one part I can think of that may be easier. - Harder: Longer and more expensive iteration cycles, MVP can be expensive, manufacturing and production required to scale, expensive certification - Easier: Raising money (sometimes) especially if you are a moonshot with a big vision. Good example is Boom Supersonic. Good news is there has never been a better time t…
I'm not in the field, but from my perspective, aviation is super, super conservative. That is one of the reasons why we have GA still using leaded gasoline in engines that are largely unchanged from the 1950s. F1 is basically the exact opposite, they are pushing the bleeding edge of technology all the time.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#54Earlier quoted context omitted.
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.
Don’t many modern ships already have this? I recall watching “Big Ships” or some such on Discovery Channel about 15-20 years ago where they explained ships already having multiple stern and aft, starboard and port, “pods” either with jet streams or rotors.
Sure, but having driven ships with those, they're not as maneuverable as they could be. It takes time to deploy the pods and often they aren't available at high speed.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#55Which DMLS platform are you using to print these components?
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#56I 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 silver would actually hurt you (proximity effect from flux crossing through the stator conductors, producing eddy currents).
We want to start simple with cooling, hence the water/glycol. There certainly could be some opportunity to use something different (maybe with certain fuel cells and liquid hydrogen already onboard?). Regardless, the thermal resistance from hotspot to coolant is dominated by conduction resistances inside the motor, and is less a function of the convection resistance from the housing to the coolant.
We will be sending out a newsletter occasionally, there should be a link at the bottom of our website.
Thanks for the questions!
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#57First 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!
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#58If you don't mind sharing - what is the airgap diameter (presuming it's a radial flux motor)?
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#59Given 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. My back-of-the-envelope is: - Assuming 0.4 kWh/kg for batteries, and they have to run for 4 hours, then the total mass per kW is 10 kg (batteries) and 0.08 kg (motor). - A 1% increase in motor efficiency could eliminate 0.1 kg of batteries, which…
Keep in mind that an electric motor isn’t limited by the amount of oxygen in the air. As a result it can fly significantly higher where there is far less air resistance. Since air density is proportional to the square of the elevation this can lead to significant efficiency gains. Believe it or not, partly as a result of this, the SR-71 had it’s best mpg at peak speeds.
A simple physics-based plane model (like the one we made to understand vehicle-level impact of our technology development) dictates that the range-optimal cruise speed is proportional to 1/sqrt(air density), so it makes sense that the blackbird was more efficient at high speed when at high altitudes (admittedly, this simple model is subsonic, and there are a lot of other factors for supersonic flight).
Since having lower air density also means you need a higher lift coefficient (angle of attack) to produce the required lift, and then you have more lift-induced drag (which goes with the square of the lift coefficient). I think air density more or less washes out when it comes to its impact on range. That being said, you cover the full vehicle range at a higher velocity at higher altitudes, so it certainly seems like there would be significant benefit from a travel-time perspective.
All that being said, there are significant high voltage insulation challenges at higher altitudes, which is something we are working on.
Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors
#60So... in layman terms, can I buy this, strap on the Boeing 737 instead of turbine and fly? Will I need 2 units, for each wing? Or how does it work?
Well, you would need significant energy storage either in the form of batteries or hydrogen + fuel cells as well :)
Our technology demonstrator is a 250 kW machine, but we have plans to scale up to the megawatt class in the next few years. Like Jason mentioned elsewhere in the thread, tens of megawatts are required for a narrow-body jet like the 737. There is significant aerodynamic benefit from having multiple distributed propellers/fans as opposed to two-four big ones, and likely this is the path forward for electrification of these larger planes, i.e. a lot more than 2-4 units, with single-digit megawatt capability per unit.