<choosing my words carefully here because I actually work in a Tier-1 aerospace supplier working on electric aircraft>I think the range on these things will be poor (compared to typical US commuter range) with lithium, but with solid state batteries...let's fly. Where's Craig when you need him?
The economics are obvious...while flying takes more energy than driving, the electric drivetrain and low-massing of the vehicle means that a drone commute might use less primary energy than one person driving a big ICE SUV. And automating flight (and in air avoidance) is MUCH easier than automated driving on crowded, poorly repaired streets. Less material to build the vehicle, no emissions, reduced need for asphalt and concrete infrastructure...sounds GREEN to me.
Main one is mass - as a rough figure of merit each of these 110kW motors would have a mass of 40kg plus say 20kg for power electronics, and improving this is hard work. That's 250kg for propulsion, even before you start adding in structural mass and batteries.Sure. Let's do the maths...
The existing 1 person quadcopter (e.g. the Ehang 184) has a 15 kWh battery and a 23 minute air time. We could extrapolate that it would require 15*(60/20) = 45 kW in normal forward flight at 30 mph, or 45 kWh to carry one person 30 miles.
As you asserted, motor peak output is more than 2X this figure, 106 kW.
The existing model, of course doesn't have 30 mile range, it would only get 10 miles and then need to be charged for 2 hours, but I was supposing a future superior, lower specific mass battery.
Ah - I assumed you were doing a direct comparison of an electric SUV available in a few years to an electric quadcopter available in a few years. Current hybrid SUVs are typically 20 kWh for 30 miles of driving (although most are pretty tepid hybrids incapable of this) - if you go all-electric (permitted for the quadcopter) you can cut out a shedload of mass such as the entire IC drivetrain to get it down to maybe 15kWh without much of a drama - a third of the power consumption of the quadcopter.A proper US SUV might have 15 mpg, and use 2 gallons of gasoline to carry one driver 30 miles in normal road traffic.
Primary energy content of 2 US gals of gasoline = 228,000 BTU. The Ehang's 45 kWh = 153,000 BTU.
It appears that the Ehang 184 electric helicopter uses less primary energy to move 1 person than some SUVs in current use, as asserted.
What am I missing?
More than you'd think, if done properly. The quadcopter example we're talking about, for instance, might well have two motors per rotor with each being powered and controlled independently to ensure that there is no single point of failure (well, it certainly would if certified under FAA or JAA rules - given that they're talking about flying it in Dubai but not under either set of rules rather suggest that some short-cuts might have been taken here). Unfortunately there's a lot I know here about current projects that I can't really talk about, but there is some serious money being put into electric aircraft of all types - mostly hybrid rather than pure battery. The battery type tend to be either tech demonstrators or possible trainer aircraft like the Airbus E-Fan.While fixed wing aircraft can obviously glide, they don't always have a place to land in a dense urban area. The Ehang can neither glide nor even gyro, it would need a low-mass parachute in case of power failure. Multiple motors do provide some redundancy.
The physical avoidance is easier, but that really isn't the problem with self driving cars. Instead the problem is spotting and interpreting a hazard, then deciding what it will do. Controlled airspace gets over this problem by only permitting aircraft with transponders to enter, and insisting that they are under positive control from the ground at all times. To get "flying car" type functionality you need to get rid of this - which either means that everything needs to have transponders/TCAS on board (cue massive revolt from other airspace users - balloonists, glider pilots, GA pilots, hang gliders, etc.) or you have to use optical systems as per current self-driving car systems. With aviation that's much harder however - the threat can come in three dimensions rather than two, and given the very much higher average speeds you need to spot potential threats at a far greater distance than on the ground. It's also worth noting that the maximum rate of deceleration/turning is significantly higher on the ground than can be achieved by anything but an aerobatic aircraft - tyres help an awful lot because they give you positive contact to something that isn't moving, compared to shifting a lot of air to apply a force.As for avoidance...three dimensions makes it easier rather than harder compared to two dimensions (or in a single lane, one dimension), especially with vehicles that can hover and execute sharp turns.
With batteries as the only power source, yes. All I'm comfortable saying is that there is some serious money going into electric helicopters right now, coming from people who know what they're doing.I think with existing or near-future Li-battery tech helicopters are going to be a bit of a stretch...I'll defer to you on fixed wing.
Getting that airspace will be very painful - no way would "flying car" type aircraft be permitted into existing controlled airspace, and kicking existing users out of airspace that is currently not controlled will also be very difficult. Controlled access highways may actually be easier, since the restricted access interstate/motorway/autobahn system already exists.I personally think that autonomous driving will have a difficult rollout, not b/c it is intrinsically difficult, but because we are imaging a **mixed** environment with both human and autonomous controlled vehicles on the same roads. Way harder than an all autonomous system...predicting human behavior is harder than figuring out a fixed obstacle in your path. As long as humans are in control, lightweighting land vehicles is probably out as well.
In the air it will likely be easier...define controlled airspace corridors that no human operated aircraft are allowed to enter.
Have a think about the cost of inter-seasonal storage of energy - the only plausible way I've yet seen proposed is to use it to generate synthetic hydrocarbons, probably methane. Once you've done that, synthesising jet fuel is pretty easy using standard processes: the assumption that future aircraft will be all-electric is actually quite an implausible one, although they will certainly have a very significant electric component and probably a very large battery capacity (peak power demand cruise power demand, but cruise energy consumption energy consumption during peaks).I also think that in a future renewable powered world, there will be plenty of primary energy for those that can afford it. While probably not enough that we can all vacation on the moon once a year, a system of electrically powered, lightweight autonomous aircraft for commuting is no crazier from a primary energy point of view than the asphalt/concrete/steel/ICE/fossil system that we seem to have now.