Comment by PowerfulWizard | Hacker News Reader

Comment by PowerfulWizard | Hacker News Reader

I'm optimistic about electrical. Here is a high level analysis of power and energy density required for some electric vertical takeoff aircraft, compared to some existing batteries: https://www.pnas.org/content/118/45/e2111164118 (h.t. kittyhawkcorp twitter). The necessary power density is achieved, the energy density needs to improve by about 2x for these vehicles to attain their intended range.

The article also compares the range and energy efficiency to electric and ICE vehicles, accounting for the distance reduction by flying in a straight line versus driving on the road. If I recall it doesn't apply any extra value for time savings. The overall energy used in flying could be as little as 2-3x the energy used driving a terrestrial electric vehicle. Combine that with vertical takeoff and no traffic and we're looking at something pretty compelling.

And how much does it really need to cost compared for example to a Tesla? The weight will be more optimized and the safety regulations I assume are much sterner. The technical complexity seems similar but the volume will be much lower. I don't think it really works if you need a pilot's license so full autonomy is probably also a prerequisite for an everyday application.

I think EVTOL will still be embryonic in 2 years, but impressive in 5 years.

Autonomous vehicles can't drive in a tunnel yet, and you're imagining flying autonomous cars in 5 years?

Flying cars already exist, they're called helicopters, and they are not a promising consumer technology, and never will be. Flying heavy materials (such as human flesh and bone) is far too energy intensive and inevitably produces too much noise. It is also far too dangerous to become a consumer technology.

1. Autonomy in the air is far easier than on the roads

2. Helicopters have a much lower L/D ratio in forward flight than the tiltrotors being proposed for eVTOLs.

1. Yes, but autonomy in a fixed tunnel would be easier still, and yet the Vegas Loop is using human drivers.

2. Helicopters have the advantage of actually existing in many varied form factors and designs, in common civil use, unlike tiltrotors.

Yes, in the air I'm expecting a very different scenario than on land. No pedestrians just an element of collision avoidance for birds, all vehicles legally required to be broadcasting their position to an automated air traffic control, probably maintaining 100 meters between vehicles versus road traffic being 1 meter from oncoming. In the air it would be almost a pre-planned route with a 50 meter collision avoidance corridor. Plus an emergency landing site selection process, potentially the ability to land on water or an emergency parachute.

Part of the reason I found the paper I linked to be persuasive is that they predict the EVTOL aircraft only needing 2-3x the total energy of an EV. The energy cost in dollars could be less than gas for an ICE vehicle making the same trip. There are very light aircraft with 100HP engines, I'm picturing something light and birdlike.

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