It’s 2015. By now we were supposed to living in levitating glass houses on the moon, riding around on hover bikes, and traveling in tubes. Instead we’re still stuck on Planet Earth living in houses made out of rocks and plant carcasses, driving our puny little motorcars burning fossil fuels. I mean I guess some of us do travel in tubes, but the ones I’m talking about are more Futurama and less London Underground. It’s the future! Where was all the cool stuff we were promised in Back to the Future, and Star Trek?!?!
Well let me tell you why:
Let’s start off with the big one. For some reason everybody always seems to think that flying cars are the future. Ever since mankind first took flight its seemed like flying cars were 20 years away. So where are they? You’d think, surely by now someone would have invented a flying car. I mean whoever it is is sure to be an instant billionaire…right? Well, no. As it turns out, the flying car is kind of a stupid idea. I should say, it’s a dumb idea, with current technology. Now let me tell you why.
Ever since cars and planes were invented they have had diverging design criteria. Planes are built for two things, first and foremost safety, and secondly efficiency. In an oversimplified way, flying is a war with gravity, and when you lose that war you often end up pile-driving straight into the ground like whatever picture immediately comes into your head when I say the word “pile-driver”.
Anyways, because of those priorities planes are designed to be light, and maneuverable. Just about everything aboard an airplane is designed either to help you avoid crashing, or to try and save your life if you do. That’s why flying is so safe, even though you’re basically giving god a giant middle finger while you do.
Cars on the other hand have been designed for luxury. Those cushy seats with the internal heating that keeps your butt warming, all that stuff has a mass greater than zero. That’s extra crap you have to carry around, which means you need to add extra energy to get the car to move as fast. That’s why cars get such bad mileage. Every time people manage to make an engine that is better and more efficient they just see it as an excuse to shove more crap into the car. And while cars have been getting safer and safer there’s a reason that more people die driving cars in a single day than die in an entire year in the air.
Also flying a plane and driving a car are completely different prospects. If you thought learning to drive in 2-dimensions was hard, try flying a plane in 3-dimensions with crosswinds and updrafts and all that nonsense. There’s a reason pilots have to have 1,500 hours of flying time before they’re allowed to fly alone, kinda makes that 10 hours you fudged on the DMV from kind of insignificant doesn’t it.
Aaaaanyways, what happens when you try to design a flying car is you have to make sacrifices to both aspects of the car and what you end up with is a vehicle that’s a crappy car and an even crappier airplane. To make the plane able to fit on a road (even with folding wings) you have to make really stubby winds which are aerodynamically inefficient. There’s also the matter of creating a propulsion system that can move through the air and then transition to driving instead, although that’s a fairly easy problem to solve. If you want to make the car able to fly, you have to ditch that massive entertainment system, and the heated seats. What you get is this:
It looks cool, but as an aerospace engineer I can tell you, that thing looks draggy. And as a car, that thing fits one person (barely). The whole point of the flying car is that we’d all be driving them, but that thing lacks all of the utility of a car. You can’t carry any thing, you can’t even bring a friend with you to show off your crappy new flying car. You can design a car to look like a plane, and a plane to look like a car, but to have a single vehicle that is functionally similar to both is nigh on impossible, but not totally impossible.
How you do it:
So what would you need to build a real flying car? First and foremost you have to completely remove the human element, or at least the human pilot. Humans can drive on roads well enough (not really, but we’ll pretend). Planes nowadays pretty much fly themselves, and by pretty much, I mean the totally run themselves. On a modern airliner like a Boeing 747 a Pilot needs to taxi the plane to the correct runway, radio with the tower for a little bit, press the button to takeoff, press another button to raise the flaps, press another to lower the flaps when its time to land, press a third whole button to initiate landing, and then taxi the thing to the gate at the end. My car would have two, select a location, and go. In my world, everything else, even the Air Control Tower would all be automated. If Google would let me, I’d also integrate their self-driving software/sensors into the vehicle too.
As for the vehicle, it would probably look like an SUV with a big wing strapped on top, albeit with a couple of modifications. First off, We’re making this thing way more aerodynamic, enough of this blocky crap, I want some nice smooth edges. Next, we’re getting rid of all this steel crap, I want wood and Aluminum! The frame will be the cheapest Aluminum I can get away with, and everything else will either be wood or some type of foam, hell I’ll use balsa if I have to. Next, we’re keeping the piston engine, maybe ramp it up to V8 or V10, except instead of petroleum we’re burning hydrogen. It’s 20-gaddamn-15 enough of this fossil fuel BS. Coming out of the front will be a nice big propeller that will either fold or simply lock in place during road travel (or both). Next, we cram fuel into every available nook in cranny in the vehicle, this will be a tad difficult, since we’re using gaseous hydrogen, it will have to be pressurized, but those are the types of challenges that make engineering fun. Lastly, we cover the vehicle in control surfaces. The tail will likely have to have some kind a collapsable feature to it, we’ll throw some canards on there for funsies, and enough airbrakes to kill a shark. I’m imagining it will look something like this:
Ok let’s talk about Jetpacks. I wasn’t going to include Jetpacks on this list originally. Largely because we already have them, and they’re the douchiest things ever. I should clarify, the jetpacks themselves aren’t douchey, it’s more like the subset of people most likely to buy a jetpack is disproportionately douchey, but more on that later. The idea of giving everybody jetpacks has the same issues as trying to give everyone airplanes, basically you’re going to have a bunch of untrained idiots crashing into stuff and dying (kind of like cars). speaking of which…
All you have to do is look at what’s happening with drones. Suddenly anyone can fly their $200 quadcopter into restricted airspace and cause entire airports to shut down. Now granted some of that has to do with FAA regulations that were not designed with miniaturized UAV technology in mind, but the argument still stands. It’s a lot less funny when its a human being crashing into your wedding party than it is when it’s a toy.
Anyways, we’re not here to talk about the cultural ramifications of jetpacks, we’re talking about the technological hurdles. Let’s start by examining that jet pack from earlier.
What’s happening here is that the jet pack is redirecting water downward. If you remember Newton’s Third Law from high school, when you push something one way, it pushes back on you in the other, so if you push water down, it will push you up (fun fact: this is how airplanes work). Ok that’s simple enough, but wait, where’s the water coming from? Well if you notice in the picture, there’s a big tube leading from the jetpack into the water. In reality the pack that this person is wearing is just a nozzle. The water itself is being pumped in from an external power source (essentially a ski-doo engine). And so we have reached the big technological hurdle of building a badass jetpack: propulsion.
So generating enough power isn’t too much of a problem. There are plenty of options, you could have some kind of pressure just like the jetpack up there, you could build a little turbofan, or simply have some helicopter blades, although you can ask the US Army how well that turned out.
There are a number of problems however. As far as propeller driven craft, those tend to either be too weak to fly out of ground-effect (a lift enhancing phenomenon that happens when you’re close to the ground), or too stable to strap a human too. Turbofans are cool, but the miniature versions are incredibly inefficient, have a lot of control lag, and run really hot, needless to say you wouldn’t want to strap one to your back. The most popular idea is some kind of pressure jet, like that water jetpack I keep mentioning, but the problem with that comes down to fuel. You have to pump a huge mass out of your pack every second just to maintain flight that you either fly for at most 10-15 seconds, or you have some kind of external pump that essentially limits your mobility to the point where the jetpack has lost its value. Oooooor you say fuck it and just strap yourself to a giant rocket.
So How Do We Do It?
Like that stupid Redbull thing they keep showing off.
Now don’t everyone go out and try to buy one of those jetpacks all at once, there’s quite a few problems I see there. Now I should start by saying that there are a whole host of specification that I don’t know, either because they haven’t released them, or because I’m too lazy to look them up (probably more the former than the latter). First off, those things look insanely draggy (read: inefficient). Granted, the human body is very draggy on its own, but those guys are flying at really high angles of attack (read: draggy, read: inefficient). Again this could be due to the aerobatics they’re performing, but still, so much drag. Secondly, I’m not entirely certain what type of propulsion they’re using, but they look like miniaturized gas turbines (jet engines), which are insanely inefficient, albeit quite powerful (although I should note that they still need four of them). Going along with this, I’m not sure what the endurance is on these packs. The video is edited in such a way that no one shot lasts longer than a few seconds, which means they could run for a few hours, or a few minuets, or even just a few seconds. I’m not intensely familiar with those particular engines, but I’d be surprised if they lasted more than 10-20 minutes (although I’ve been wrong before). It’s also hard to tell how much thrust is output, how fast they’re going, etc. which means you can’t really tell if they’re “flying” or “falling with style” (although I’d argue there isn’t really much of a difference).
Ok and let’s stop over analyzing this video and get down to what this means for your jet-packing near future. And the answer is a solid maybe…but I wouldn’t be on it. I should note that those guys were dropped out of a helicopter, those jetpacks aren’t capable of taking off from the ground, and they need a parachute to land. Also they’re bulky, they more resemble an airplane wing than a jetpack (because it is). Oh and controllability is still an issue (meh, make a computer do it). Ultimately, until we can come up with a smaller, more efficient, less face-melty propulsion system we’ll be stuck with watching reruns of Thunderball.
Ok wow, that was a lot longer than I was anticipating, I had intended for this to be a one-off bit, but I got so distracted talking about flying cars and Jetpacks, that I think the rest of this article deserves its own post. For that I hope you will join me next week for part two of Why We Can’t Have Nice Things.