Another week, another flying car. Well, kinda.

This time it’s not a flying car, it’s two of them and, to be fair, neither uses the phrase ‘flying car’ while trying to do what amounts to the same thing: provide personal transport, only in different locations.

Project one is the Kitty Hawk Flyer, which is “safe, tested and legal to operate in uncongested areas under the Ultralight category of FAA regulations”.

The finished Kitty Hawk design will apparently look different from the prototype doing the rounds, which, given that it looks like a rodeo bull on floats surrounded by eight terrifying rotor blades, is probably a good idea.

It’s designed to be used over lakes and rivers where nobody is around, in short.

Still, the company says: “When everyone has access to personal flight, a new, limitless world of opportunity will open up to them.” That might be true, but the Flyer’s ‘world’ will be over lakes and rivers that are pretty much deserted, which isn’t that limitless, and the ‘opportunity’ will be to have what looks like quite good fun but not really go anywhere.

Idea number two comes from every cab driver’s favourite company, Uber, which wants to introduce “on-demand urban air transportation” in a few years. Which you can kinda get now, if you own a helicopter.

Uber has grander ambitions than Kitty Hawk and has partnered with aerospace firms to investigate and develop new vertical take-off and landing vehicles. It foresees a future where you can “push a button and get a high-speed flight in and around cities”, a sentence in itself that terrifies me three times. ‘Push a button’ suggests it’ll come to you, ‘high-speed’ suggests it’s fast, and ‘in and around cities’ suggests you and I might be near it while it’s happening.

I don’t want to sound like a flatearther, but the logistical, legislative, technical and cost barriers are absurdly high. And when you generate the kind of force necessary for flight, you tend to generate quite a lot of noise, which is why even a kids’ drone weighing a 1kg sounds like living in a wasps’ nest, and why you can hear a helicopter from miles away.

So how did we get here, to where novices think that getting into the air transport business is readily achievable? I suspect a vast underestimation of gravity, and the application of very simplistic physics.

Thing is, see, if you try to calculate the power required to keep an object in the air, hovering, it can look quite tempting, because there is no minimum power requirement to do it.

Yes, obviously, hovering requires a force equal to the weight of the unit (100kg would want 980N to hold it against gravity, I think), but if you generate that force efficiently enough, you can – theoretically – use very little energy doing so. The more efficient you are, the less power you’ll use, and electric motors are quite efficient. It’s acceleration, and how fast you want it, that requires lots of power.

And so you can see why the idea appeals to people. And why the freedom of flight has appealed to us for centuries. But the biggest problem – beyond the legislation – remains gravity. Yes, theoretically, you can use very little power to hover stationary against it. But just try it without any.