We're in a nearish-future metropolis and the secret police are starting to take control of the city. They have some new technology, including hoverbike-style vehicles (I imagine them as single-person vehicles), that stay above ground when on the move and can zip through the city streets. I guess I am thinking of something along the lines of what we see early in the (2009?) Star Trek movie, when a young Kirk is being chased by a policeman on some kind of hoverbike vehicle. Also the small vehicles used by the Jedi in AOTC when they chase Zam through Coruscant, they are high-flying but seem to be able to fly low too.

Would it be possible to create a functioning version of this kind of vehicle, let's say in the next 40 years? I'm open to all ideas regarding how it might work. I'm not a scientist though I understand that magnetism only works if there is a magnet on the static surface (ie the road) too? I'd rather not have them kept up by huge cannons of water, and also would rather not have them use some form of energy or raw material that we haven't discovered yet.

What are the other options? Gas propulsion? Could some kind of electromagnetism work?

Quick edit: I've just thought about the big ships in The Matrix too, that have those giant electric-blue things around the outside of the hull. I have no idea how they operate but maybe something on a smaller scale could work?

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    $\begingroup$ The actual challenge here is not to make the vehicles hover, the challenge is to make them compact. $\endgroup$ – Alexander Jul 15 '19 at 16:19

Ironically enough, these kinds of vehicles are actually less likely today than they were in (say) the 1960s. The reason for that is the current focus on efficiency.

When you get right down to it, anything that hovers has to constantly apply energy to maintaining a set distance from the ground. This is on top of any other energy that has to be applied to get the hovering vehicle to actually move. This is because of gravity; the Earth attracts all nearby smaller objects to itself and as such you need to counteract that force by turning real energy into potential energy (the energy that would be applied by the earth to a falling object) on a constant basis.

The wheel on the other hand actually uses gravity to its advantage by using weight to press the wheel to the ground, causing tension which in turn causes friction, which (if stronger than the rotational energy applied to the wheel via the axle) causes lateral movement through rolling. This is why car tyres are made of rubber; it maximises the friction between the tyre and the road, making the lateral movement of the car the least resistant application of the energy.

In other words, hover cars and bikes need to apply some of their energy constantly to fighting gravity; wheeled vehicles actually use gravity to apply their energy to lateral movement. Yes, these are simplifications of the physical laws, but they are functionally correct.

In point of fact, we do have a vehicle that performs the way you describe and it's been in service for many decades; it's called a helicopter. We don't like it in sci-fi for a simple reason; the rotors are too big meaning it can't get in tight and do all those dog-fight scenes. Also, they can really suck at those tight fast banking turns and rolls and the like that we like to see on films. But, it's actually a good fit for the rules you've given, and the point of it is that if we could make the rotors safer, smaller and make the craft more agile, we already would have. So the answer is probably no.

But, there is one technology that could make this issue go away; anti-gravity. Just like how in 1861 the Maxwell equations integrated electricity and magnetism into a single fundamental force and led to wholesale jumps in technical advancement that had not been possible before this, if we were to integrate gravity into EM as a fundamental force, and learn how to use EM energy to manipulate gravity directly, it could change the balance of energy use by allowing us to create localised fields of either counter-gravity or nullification fields of some kind. If you have that, all of a sudden you're not contsantly having to fight gravity, your vehicle sits inside a small bubble in which it just no longer exists. In such a situation, the only energy cost is moving the vehicle in 3 dimensions. Even just a localised effect (like the EM pads on the Matrix ships) could work insofar as they force a vehicle to hover by some form of gravitic repulsion. But, to do this right, you need gravity to be affectable via EM fields, and to do that we need to integrate the fundamental forces accordingly.

The caveat on this is of course that the moment your nullgrav field fails, you fall to earth and go splat. But, this has been the case for planes and helicopters for over a century now so we know how to handle that kind of problem.

In short though, if you're not happy with current helicopter design, then the integration of gravity into EM is the one defining piece of research you need to make such a device more energy efficient and easier to maintain / refuel in large quantities.

  • $\begingroup$ "Anything that hovers has to constantly apply energy to maintaining a set distance from the ground": this is false. For example, take your hat and hang it on a hook. It will hover indefinitely without the need of any energy input. Or think of how a magnet can levitate above a another repelling magnet. That we don't know how to make the hat hover without the hook does not mean that it is impossible. $\endgroup$ – AlexP Jul 15 '19 at 17:51
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    $\begingroup$ @AlexP The hat hovering when it's on a hook is a false-equivalency, that's just like saying I'm hovering when I sit in my car, because I'm not touching the ground. $\endgroup$ – william porter Jul 15 '19 at 18:08
  • $\begingroup$ @williamporter: A false equivalency? How so? It shows that maintaining a position in a gravitational field does not have to expend energy. You need to think why we need to expend energy when no hook is available. $\endgroup$ – AlexP Jul 15 '19 at 20:26
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    $\begingroup$ @AlexP You're falsely equivocating that a hat being held on a hook connected to a solid object pushing off the ground is the same as the body of a helicopter/hoverbike being held off the ground by using repelling forces. If a hat hanging on a hook is an allowable definition for hovering, then we already have hover vehicles in the form of cars and bicycles because they're merely hanging from the ground. $\endgroup$ – william porter Jul 15 '19 at 20:57
  • $\begingroup$ Thanks for the info, I will read up on the possibilities of gravity and EM! $\endgroup$ – JP90 Jul 16 '19 at 5:14

Police hover bikes already kind of exist: https://www.youtube.com/watch?v=4dk-fiyJdvE. If you want something a bit more high-tech feeling, you can replace those bulky fan blades with jet engines, but it's still something well within the limits of modern tech.

So, the real constraint here is not "can we make hover bikes", but under what circumstances do they become worth their utility cost. Other answers have already addressed why they are not cost-effective in most situations; so, if you want to work them into your story, you need to put them into a place where living conditions are so dense that ground vehicles are an impractical first-response solution. In overcrowded urban settings, pedestrian foot-traffic can become so thick that cars have trouble being a viable means of transportation; so, such vehicles would be cheaper and more able to fit into tighter spaces than helicopters, but able to fly over a crowd or traffic jams to respond to an incent.

  • $\begingroup$ Thanks for that link - maybe a manned drone would be a better solution than a hover bike! $\endgroup$ – JP90 Jul 16 '19 at 5:14

The problem here is not so much a technological one but a usability one.

Today we can easily build hoverbikes (have a look on Youtube) that use jets or fans to keep the bike in the air. There are also bigger versions of that that can carry multiple people, they are called helicopters.

The big problem why we don't use these things the way they are used in Star Wars is that they are hardly useful.

Just compare a hoverbike to a regular bike.

  • The regular bike has a lot more traction, that means energy can be transferred much more efficiently. That means both acceleration, deceleration and manoeuvring can be done much more efficiently. Using the same amount of energy will give you a much better result in the comparatively low-speed (less than 300 km/h) chases you would be able to get in a city.
  • Because of the last point, hoverbikes would be much worse when it comes to taking sharp corners.
  • Hoverbikes need to spend a lot of energy just to stay afloat.
  • When flying close to the ground, there is something called ground effect, which does reduce the amount of energy necessary to hover by quite a bit, but it also creates a lot of random turbulence which makes flying close to the ground very hard and uncomfortable.
  • Hoverbikes become more efficient compared to the regular bike the faster they go. So on a long, straight stretch, the hoverbike could be faster than a regular bike, but only when they are not flying close to the ground. I am talking about anything >200 km/h. The higher in the sky it is the more efficient it will get.
  • Hoverbikes can also fly higher while a regular bike can only stick to the ground. This can be quite an advantage in a chase.

TLDR: The technology for a hover vehicle is already here and has been for a while. But it is a very flawed concept that looks a lot cooler in movies than it is in reality. And it will stay like that because it is not a technological problem but a concept problem.

  • $\begingroup$ In fact there are 2 commercial versions of actual hoverbikes right now: the Scorpion 3 and the Aero-X but both only have advantages in really niche areas $\endgroup$ – LinkBerest Jul 15 '19 at 15:03

I like your magnetism idea. Why not they secretly built all static-magnet spread around the city, from tiny things like a signboard to the giant structure like a bridge, rooftop of a building. The technology core is an AI which calculates the static-magnet around the vehicle and manipulates the forces for the movements.

  • $\begingroup$ Remember that the range at which static magnetism (or any magnetism at all) is able to actually carry a lot of weight is very limited. $\endgroup$ – Dakkaron Jul 15 '19 at 11:26

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