Tuesday, August 16, 2022

An Interesting Possibility

One of those things we hear from time to time is something like, "it's the 21st century?  Where are the flying cars?"  The thing is, while we aren't living in the Jetsons, there are flying cars out there.  Not very widely talked about, not widely available, not very well established, but it's an area of serious investigation by a lot of big players.  Both big name and startups alike.  There's a couple that turn up in web searches that aren't something you're likely to run across out in real life (unless you're lucky enough to live near where they're tested) but they're fairly advanced in their development.    

  • The Jetson One: "a jet ski of the air" - seems like a bit of a toy compared to...
  • The AirCar, which converts from more car-like to very plane like with the push of a button.
  • This video is an overview that shows several of the bigger development projects.  After about the first half of it.

I say this to introduce yet another consortium that made the Electronic Design magazine news this month.  Korean automaker Hyundai and Rolls-Royce have joined into a flying car development project.  While all of those flying cars in those videos seem to rely on drone technology: several electric motors, relatively small propellers (except AirCar) and battery packs on board.  The Hyundai/Rolls-Royce vehicle (which doesn't seem to have a name yet) will be powered by fuel cells, or stated more directly, it will be powered by hydrogen gas.  They plan to have a flying demo car by 2025.  

The article doesn't explicitly call this picture a prototype of their goal and I can't help but think it looks like a helicopter.  The door on the side toward us having been opened upwards adds the illusion of a wing, but with no visible means of propulsion or much of anything else, it's hard to say what this model is supposed to be.

All that aside, fuel cells are an attractive technology but less practical than a battery operated vehicle.  Why?  To refuel the battery, you plug in the charger; to refuel the hydrogen fuel cell, you fill a tank somewhere with pressurized hydrogen.  Maybe you replace one fuel tank with an already-filled and stocked tank, but there is virtually zero, zip, no hydrogen distribution infrastructure in the country.  Yes, it may be possible to get filled tanks from a local supplier of welding and other industrial gasses, but that's as convenient as it seems it can get.  Another disadvantage of hydrogen is that it's the smallest molecule in the universe, so it's hard to handle.  It tends to leak out of pressurized tanks and fuel lines, even going between the atoms in metal tubes.

Rolls-Royce seems to see this joint venture as a way to refine their designs for aviation grade fuel cells, in the belief that commercial aviation will be driven from fossil fuels soon.  

“Battery-powered propulsion to fuel larger aircraft over longer distances is not possible with today’s technology,” explains Matthieu Thomas, Airbus’ ZEROeAircraft Lead Architect. “Hydrogen fuel cells could be a great alternative because they can generate—with zero emissions—significantly more power and energy for a given weight. This makes fuel cells an extremely interesting technology to achieve our ambitions.”

Hydrogen fuel powerplant benefits include:

  • Regional transport range; longer flight times than battery-powered engines.
  • No battery charging required.
  • Zero carbon emissions.
  • Reduced noise signature.

Both Hyundai and Rolls-Royce share a vision of leading the AAM segment via battery-electric and fuel-cell electric solutions to the Urban Air Mobility (UAM) and Regional Air Mobility (RAM) markets and advancing sustainable aviation.

Everyone knows that batteries wear out and can't be recharged beyond some number of cycles.  There was a story widely talked about in the last month about someone buying a used EV for their kid and the battery failing.  A replacement battery would more than double what they paid for the car.  I'm new to the concept of fuel cells wearing out, but this article was talking about it being a major obstacle to the wider adoption of fuel cells back in 2011.  Toyota published an article implying that their fuel cell-powered Electric Vehicles would likely have their fuel cells wear out around 62,000 miles, and they had some way to ameliorate that. 

Along with the peace of mind of a 100,000 km warranty, Toyota’s take-back scheme ensures that when the fuel cell stack nears the end of its life it can either be reused in other applications or dealt with safely and responsibly.

It's hard to draw a comparison of driving 100,000 km on a car to the number of hours in a flying car. 


  1. It looks like a wing root at the back of that Hyundai/Rolls-Royce concept.

    I can see a drone like vehicle based on fuel cell technology or hybrid technology (fueled engine driving a generator that powers electric lift-drive fans). That would be more of a "Jetson" style vehicle. Battery power is just not good for flight for many reasons. My tablet just hit 5% charge on the way to no charge so cutting this short.

  2. Thankfully reliability isn't too important with aircraft.

    1. We used to say, "flying has a perfect record: we've never left one up there."

      Airplanes have a perfect record. Every plane that ever took off brought its passengers back down again.

  3. can always pay the owners to fly them over drought-stricken areas

  4. Vaporware, as usual.

    Call me when there's a brick-and-mortar dealer network and the FAA approves their use.

    Until then, this is boob bait for the PopSci/PopMech bubbas, as it has been since the 1930s.

    1. And c'mon SiG, you know better than this:
      "It's hard to draw a comparison of driving 100,000 km on a car to the number of hours in a flying car. "
      100k is 63K miles.
      At 30 MPH that's about 2000 hours of engine time.
      At 60 MPH, that's 1000 hours of engine time.
      A pilot with 1000 hours is just getting good at it.
      An airplane with 1000 hours is virtually brand new.

      An electric consumer airplane makes almost as little sense as running one with a full nuclear reactor.

      If they're going to go this full-asinine, they may as well power them with CR123s, or even just use alkaline D-cells, and have you swap them out in-flight, FFS.

      I'm pretty sure I saw an ad for a battery-powered flying pack in Sgt. Rock around 1966, but I didn't fall for it then, either. ;)

    2. Nah, we'll charge the batteries with free electricity from non-polluting, non-radioactive fusion plants (/sarc)

    3. The fusion plants will be online in 20 years. They've been telling me that since 1970.

  5. Do understand that the product of fuel cells is water vapor.
    Water is FAR MORE of a greenhouse gas than CO2.

  6. Dear Sir;
    I have been involved in one way or another with LTA (Lighter Than Air) aviation for much of my life, mostly with hot air balloons but with both helium and hydrogen balloons as well. I don't have recent information about hydrogen, but back when I first studied this subject I discovered that hydrogen is actually thin and slippery enough to diffuse through glass while hydrogen was much easier to capture and hold because it is a binary molecule due to it's one electron in the valence ring. However, I tend to agree with the concept of it being difficult to hold under pressure and that it would be a major problem, particularly in an enclosed space environment.

  7. Sorry. I meant to say that helium is thin and slippery enough to diffuse through glass. oops.

    1. I thought that was what you meant, but thanks for clarifying. For the record, my only actual experience with helium or hydrogen have been either (1) balloons or (2) something in high school chemistry. It's just when I read something over and over in technical publications, I tend to internalize it.

  8. Hydrogen is hard to contain - in some cases letting get absorbed into metal then heating to extract it. Not really practical for flying. Binding 4 H atoms to one C atom works well - as SpaceX has shown. An old but hard to control technique is to bind 2 H atoms to 2 O atoms, hydrogen peroxide. Didn't they once run torpedos that way?

  9. Considering the IQ and lack of common sense the average driver posseses it's a damn good thing that flying cars aren't a viable mean of transportation. Would you want Bubba and his POS Jetsonmobile flying over your house daily....just waiting to crash into it because he couldn't bother with basic maintenance?

  10. If they're flying cars, what need to go near JFK or Dulles?
    That's the exact problem one is trying to solve by making them flying cars, rather than driveable airplanes.