4
$\begingroup$

What is an expedience of sci-fi gliders? these machines flying near the very ground.

It doesn't matter what they call them there (in different way).

No matter what specific principle they fly - what is the point as a principle? In all these fantasy worlds ... Why don't they rise higher as normal flying devices, why do they parody cars? Or this is it for those who are only afraid of heights or do not know how to fly vehicles in the air? Well, all these computers would handle it... If it’s about energy, i don't suppose that much less is consumed energy in this way. It's about building any sci-fi world, civilization and the technology that has such machines.

What is the meaning and purpose of this particular type of machine?

glaidet SW

$\endgroup$
1
  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Sep 30, 2021 at 18:54

15 Answers 15

35
$\begingroup$

This sort of vehicle will become popular when

a) you get a repulsive principle which gets weaker with distance,

b) the repulsive force requires more power for greater force, and

c) the available power you can put in a vehicle is limited to a value which only produces a foot or two of clearance.

This produces a vehicle which will travel on any reasonably smooth terrain, and a sufficiently sophisticated repulsion control may permit operation on quite rough terrain: the repulsion can be reduced when the vehicle runs over a rock or bump, just enough to keep the altitude constant. Basically, it behaves like a hovercraft. It will be popular on "frontier" worlds where roadways are uncommon.

Presumably, military or police craft with expensive, high-power units can operate at greater altitude.

$\endgroup$
6
  • 9
    $\begingroup$ @Пилум starwars.fandom.com/wiki/Repulsorlift $\endgroup$
    – PcMan
    Sep 27, 2021 at 13:56
  • 4
    $\begingroup$ @Пилумor, closer to reality, the ground effect (see the Ekranoplan in jamesqf's answer). With weak engines compared to the local gravity flight as we know it becomes very hard $\endgroup$
    – Chris H
    Sep 27, 2021 at 15:23
  • 8
    $\begingroup$ @Пилум: It's called handwavium. The author makes up the tech for story purposes, just like for example faster than light travel. $\endgroup$
    – jamesqf
    Sep 27, 2021 at 17:36
  • 1
    $\begingroup$ In the case of a), especially when said repulsive technology is low to no power requirement (which seems to be the case with star wars hover craft as they seem to float even when unused/off) as compared to some kind of active thrust mechanism that would otherwise be capable of lifting it into the air. $\endgroup$ Sep 27, 2021 at 20:25
  • 2
    $\begingroup$ the simple answer is it's related to a magnetic "-LIKE" effect. it's that simple. do note that magnets behave exactly like this in the real world. (if all of the ground surface was steel, you could literally build, a device that behaves exactly like this - it floats, but only a couple feet off the ground, and can't go higher.) in future physics there are "other" forces we just don't know about currently, and, certain of them are "magnetic like" (but work between any material, ie the dirt/rocks, and our synthetic generator thingy). gravity is totally unrelated. $\endgroup$
    – Fattie
    Sep 30, 2021 at 5:28
23
$\begingroup$

There are lots of possible reasons:

  1. It's a hovercraft. Real-world examples: https://en.wikipedia.org/wiki/Hovercraft

  2. It's an ekranoplan. Another real-world example: https://en.wikipedia.org/wiki/Lun-class_ekranoplan

  3. It depends on a hand-waved anti-gravity repulsion effect, which drops as the square of the distance from the surface. No real-world examples, alas, but a maglev train is somewhat similar: https://en.wikipedia.org/wiki/Maglev

PS: Technology aside, there might be another reason, which is simply that it's fun. Ever looked out the window of a commercial airliner that's flying at a large fraction (typically 0.75-0.85) of the speed of sound? It seems like you're barely moving at all. Fly along with me in my single-engined prop plane when I've got the wheels down close to the sagebrush, and I guarantee it'll seem a lot faster. Likewise driving a sports car vs a jacked-up SUV at the same speed, riding a horse at the gallop, a sailboard in a good wind, and many other things. It's all about your point of view :-)

$\endgroup$
10
  • 7
    $\begingroup$ @Пилум did you read the bit about " repulsion effect, which drops as the square of the distance from the surface". You should read the bit about the repulsion effect, which drops as the square of the distance from the surface. You could learn about the repulsion effect, which drops as the square of the distance from the surface, if you do so. $\endgroup$
    – PcMan
    Sep 27, 2021 at 13:59
  • 6
    $\begingroup$ @Пилум: The point, which you're obviously missing, is that neither those real-world devices nor the SF ones ACTUALLY FLY. They use some technology that allows them to rise only a short distance above the surface. $\endgroup$
    – jamesqf
    Sep 27, 2021 at 17:32
  • 1
    $\begingroup$ Instead of saying ekranoplan I would instead simply use ground effect, as that is probably a bit better known, and I at least think of the ekranoplan as a specific implementation not a classification. $\endgroup$
    – jmoreno
    Sep 28, 2021 at 0:32
  • 2
    $\begingroup$ @jmoreno: I don't think so, because an ordinary plane can certainly fly in ground effect - see above about having the wheels close to the sagebrush, or better yet, dry lake beds :-) Then too, I don't know of any purely ground effect vehicles other than the Soviet-era ekranoplans. $\endgroup$
    – jamesqf
    Sep 28, 2021 at 4:52
  • 1
    $\begingroup$ @jmoreno While the ekranoplan is a specific implementation it's the only implementation, thus it defines the whole class. $\endgroup$ Sep 29, 2021 at 4:47
17
$\begingroup$

Why do you want a bridge when a taut rope would do?

It's al about safety. If I am traveling on a flying machine that is mass marketed for everyone like a car and which can ramdomly fail anywhere, I'd rather take a three feet fall than a three thousand feet one.


Also it'd be a hassle to climb up to the clouds when my final destination is the bakery just a few blocks away.

$\endgroup$
3
  • 1
    $\begingroup$ This only makes sense if the vehicle only moves at car-type speeds. If I'm going a few hundred miles and hour I want to be up in the sky--being low means more chance of hitting something (civilian aircraft are limited to 250 knots until they're high enough up--mainly due to bird danger) and the speed will be lethal anyway, not as far to fall simply means less time to fix the problem. $\endgroup$ Sep 29, 2021 at 4:49
  • 1
    $\begingroup$ On the other hand, if you only need to go and pick up some power converters, why would you travel a few hundred miles for them? Cars aren't driven anywhere near top speed for most of the time either. $\endgroup$
    – ojs
    Sep 29, 2021 at 7:24
  • 1
    $\begingroup$ @Loren Pechtel: Not necessarily. I've been known to fly ~100 kts at not much above sagebrush level, 'cause it's fun. (Though I do it out in the desert, where it only annoys coyotes & jackrabbits.) And birds aren't even on the radar when it comes to the 250 kt speed limit. $\endgroup$
    – jamesqf
    Sep 29, 2021 at 16:20
9
$\begingroup$

The vehicles are basically hovercrafts, sometimes with advanced sci fi technology making them work.

Hovercrafts are great for travel. Bumps in the road are no issue, you can float over obstacles, less friction so you can go faster. They aren't as expensive as aircraft, and they're less vulnerable to bad takeoffs than aircraft.

Irl, they aren't popular because they're fuel hogs, they're loud, and maintenance is difficult. In a sci fi future these issues could be overcome so they are the best method of transport, removing the need for dedicated roads.

$\endgroup$
2
  • $\begingroup$ "fuel hogs". Hovercraft (at the right scale) are actually quite efficient, they're just really loud and difficult to control. Higher flying ground effect vehicles are even better, due to their ability to surpass rough terrain and have no rolling friction. $\endgroup$ Sep 27, 2021 at 17:45
  • 7
    $\begingroup$ The reason they're not popular, except for water crossing, is that the air blowing out from underneath the cushion dislodges all sorts of loose material and sends it flying outwards at high speeds. $\endgroup$
    – jamesqf
    Sep 27, 2021 at 18:15
6
$\begingroup$

To put it very simply - they can’t fly. Whatever keeps them from falling on the ground doesn’t allow them to rise thousands of feet into the air. Even worse, if they reach their max height limit and start falling, it’s unable to overcome the momentum of falling, so if you have a 50 foot ceiling and go over a 60 foot depression, you are probably going to crash. Go off a 100 foot cliff and it’s guaranteed.

Note that this actually in line with our real world equivalent’s. Real life vehicles that rely upon some sort of ground effect to stay off the ground, whether it is a hovercraft or an ekranoplan or a wig (Wing in Ground) or the Spruce Goose, if they “fly” off a large cliff and they will hit the ground at a terminal velocity..

If you look at the image you posted, it’s obviously not flying aerodynamically, and it’s not flying via kinetic repulsion. And it doesn’t have an airtight cockpit, so just looking at that, I would expect rising to 20k and flying to be impossible.

$\endgroup$
1
  • 1
    $\begingroup$ Going slightly over your ceiling would probably result in more of a bounce, as the flying effect also gets stronger when you are too close to the ground. $\endgroup$ Sep 28, 2021 at 14:54
5
$\begingroup$

Technology limitations

  1. They can't fly higher. The technology requires you to be somewhat close to a "solid" surface to work.

  2. It isn't safe to fly higher. The technology used to keep it balanced requires you to be somewhat close to a "solid" surface to work.

  3. You can't go as fast if you are higher. The technology to push yourself forward relies on being somewhat close to a "solid" surface to work.

Safety/regulation limitations

  1. The technology itself is unreliable; unacceptably often it gives out, and the base of the vehicle is designed to survive a low-altitude crash.

  2. The air space above the ground is reserved for other purposes, and being in it is a violation of the law.

  3. The rules for a vehicle that can go more than a small distance above the ground make it too expensive to provide cheaply. So a limiter is installed to prevent the vehicle from becoming air-born, thus changing how the vehicle is regulated. These regulations could come from a safety, military, pilot license, or even random legacy legal crud place.

  4. People shoot down flying vehicles depressingly often, and it isn't hard. On the ground you are harder to hit, and it doesn't matter as much.

Ignorance is Bliss

  1. Nobody knows how the technology works. But you do X Y and Z, and you get something that floats a bit above the ground. The real reason may be anything above, but the people using it don't know what the real reason is.

  2. There is a taboo about flying high in these vehicles. Nobody knows why you must follow the taboo, but doing so gets you in extreme social trouble.

  3. It works perfectly fine, and when asked about it people are confused as if you are talking nonsense. When demonstrated, they express no surprise, but still don't understand when you ask them why they aren't doing it.

$\endgroup$
3
  • $\begingroup$ In my opinion, it is difficult to come up with a plausible technology with such restrictions. However, I don’t know ... The antgravity has many gitiks ... which no one knows; if it's antigravity... The safety argument being made often here doesn't strike me as convincing. Considering both advanced computers and the real unsafety of cars, etc. About taboo - it's amusing :) $\endgroup$ Sep 28, 2021 at 20:56
  • 2
    $\begingroup$ @Пилум Who says it is antigravity? It could literally be rolling force-field ball bearings of dynamic but limited size. Are you talking hard science fiction? Then no such vehicle exists, and neither does antigravity. $\endgroup$
    – Yakk
    Sep 28, 2021 at 21:29
  • $\begingroup$ Hovercraft exist currently. Those are above the ground, but not arbitrarily high. $\endgroup$
    – lidar
    Sep 29, 2021 at 0:28
3
$\begingroup$

Why don't they rise higher as normal flying devices, why do they parody cars?

Very likely they work using a special field rather then simple reaction (momentum conservation) or pressure differential

Possible reasons that I can imagine, alone or in combination

  • field strength decays much faster with the distance from the surface than increasing the available power of a mobile energy source can compensate
  • the field produces side-effects in between the generator and the surface. The side effects intensity is acceptable in intensity for small distances, but become increasingly damaging (unsafe) at increased attitudes in respect with the soil surface. E.g. at 30cm, the field heats the air 20K above the ambient temperature, at 0.5m above the generate heat causes 100K temperature differential, at 1m the air underneath becomes a thermal plasma (you can write short stories based on the reckless behavior of race drivers boiling the spectators)
  • the materials required to generate/sustain/orient the field have an inherent saturation intensity. Any attempt to go over a certain value will result in stray field lines escaping in unwanted direction causing instabilities in unpredictable/uncontrollable manner (like various types of instabilities keep the controlled nuclear fusion on a perpetual 30 years in the future).
$\endgroup$
3
$\begingroup$

They are simpler to use.

If you start flying high, at some point you'll need a jacket to keep warm, and a oxygen mask. Much simpler if you just fly near the ground where the temperature (and oxygen) is at normal levels.

Also when navigating by eye (assuming not every planet has GPS-like system) its much easier to have signs on the ground telling you how many miles it is to the next city. While navigation in the air would need more effort (and experience) by the pilot to be able to follow maps/dead reckon or the planet needs to invest in some sort of GPS-like system to be able to navigate. I know many people who still get lost with a GPS navigation device telling them where to go, which is much riskier if your stuck in the air rather than tuck near the ground.

Maybe there technology is unreliable (or people can only get hold of junk to build their vehicles from)? No one would fly in a plane that had a 50% chance of losing lift at any moment. But a land speeder that loses lift 50% of the time? Annoying but not life threatening.

There is also the consideration of whether a space government would want everyone to have what is effectively a small missile. A plane when crashing into a building can do a lot of damage, while a land speeder crashing maybe damages a building but not as much as a plane would.

$\endgroup$
2
$\begingroup$

I'm going to treat the hover part as simply a new form of wheels. As others have pointed out like a hovercraft it uses some form of ground effect rather than direct flight to stay aloft. This is also why such gliders can remain aloft even when the owners have effectively shut it down and leave it behind.

The reason why you would choose this over wheeled vehicles has simply to do with roads. Take any city or town and the most expensive and time-consuming project they had/have is their roadways. You have to spend days if not weeks checking and laying the soil layer by layer, then place the road support material and on top of that the roadway itself. These roads need to have a lot of standards to work. They need the right angle and permeability to get rid of rain, it needs to be the right mixture to reduce ice forming during the cold and not melt too much when its hot while also cheap enough to lay down the thousands of cubic meters of asphalt and ease with low cost to maintain that road.

Or you lay down some hard-packed earth and use a sci-fi glider instead. You cut down heavily on all the costs and the time spend on the roads while the vehicles are able to handle almost any surface as long as its reasonably flat (except water, hoverboards dont work on water).

$\endgroup$
10
  • 1
    $\begingroup$ "some form of ground effect|" - what is it ? "hoverboards dont work on water" - why ? $\endgroup$ Sep 27, 2021 at 16:59
  • $\begingroup$ "why you would choose this over wheeled vehicles " -i'm sorry, but my question was - "The main question here is why these devices are not converted into ordinary aircraft, if they fly anyway.." :) $\endgroup$ Sep 27, 2021 at 16:59
  • $\begingroup$ You want me to explain the ground effect of a sci-fi glider which makes no sense to begin with? There is no realistic or theoretical method that would work and simultaneously be efficient enough to be useful. I was assuming the sci-fi explanation of "well it just works with antigrav or something, dont ask and I dont have to explain". Which is pretty much all glider-type vehicles in sci-fi that I know off. As for "hoverboards dont work on water", I suggest you watch all 3 Back to the Future movies, they are old but still great. $\endgroup$
    – Demigan
    Sep 27, 2021 at 17:36
  • $\begingroup$ As for "why not use them as aircraft". You already call them gliders and that is exactly what they are: they glide above the ground. The picture of your glider already has no altitude control available (its from stad wars) which is a sign the technology cannot let it fly. You are essentially saying "anything that can remain off the ground for X seconds has to be able to fly, why dont they actually fly?" And applying it to all sci-fi gliders which each have their own, usually handwaved, explanation. $\endgroup$
    – Demigan
    Sep 27, 2021 at 17:41
  • 1
    $\begingroup$ @jamesqf I am talking movie hoverboards. The Back To The Future one was such pop culture that they actually tried making a real one: crealev.com/mattel-hoverboard-bttf and bbc.com/future/article/…. The problem as I said already: they just arent feasible efficient versions that we would be using for cars. $\endgroup$
    – Demigan
    Sep 28, 2021 at 7:10
1
$\begingroup$

You want to include a land speeder (as Star Wars calls them) in your world but can't think of a good justification? Unfortunately, that's a tall order.

Beyond the real-world practicality of special effects (especially pre-CGI), they appear in Star Wars because they capture the aesthetic feel that Lucus was going for back in the 70s. He wanted a world with fantastic technology that still felt worn-out and familiar. By presenting a basic, non-flying car he gave people something they were very familiar with. By removing the wheels, he gave them something of the fantastic. Honestly, it's probably one of the better tricks he pulled off back then.

After Star Wars, they reappear in various other fictional worlds mostly because they were in Star Wars. Just the association with one of the most recognizable media franchises in history gave them credibility. No one really asks the obvious questions (well, some do).

Is a "land speeder" viable in a new constructed world?

Sure, just don't explain it. As with every other movie, tv show, book, or other story that used them, the audience won't care. They're familiar and they're cool. That's all that matters.

If you want something better than "rule of cool", you have a problem. As demonstrated by the question, lots of "reasons" can be offered up but each one is easy to shoot down.

This is one of those that is either used without explanation or not used at all.

$\endgroup$
1
$\begingroup$

An "out of universe" explanation:

The readers/viewers know about cars as transportation vehicles that stay close to the ground and require sort-of level terrain.

This is clearly a car FROM THE FUTURE. Look: it even has no wheels but magically technologically stays afloat a fixed distance from the ground. Even though that technology is never explained.

$\endgroup$
1
  • $\begingroup$ This. A wheeled vehicle or a horse would be too mundane. A hovering vehicle is cool and futuristic. $\endgroup$
    – user31389
    Sep 29, 2021 at 18:41
1
$\begingroup$

Legislation and ease of operation

Flying vehicles require a skilled operator. You would also need a pilot's license/certification to be allowed to pilot them. For a ground vehicle you only need a driver's license and basic driving skills. Thus manufacturers artificially limit the maximum altitude to a meter or so to make it legally a ground vehicle. It also allows it to be operated easily - almost like a car. This also makes it cheaper as there's no need for a pressurized cabin, ice-proofing, radio for communication with air traffic control, etc. They are basically hull + power + engines. And since it's considered a ground vehicle, you pay significantly less taxes. Aircraft is considered a luxury and taxed heavily.

And the actual reason they are popular in science fiction is that they are obviously cool and futuristic, while a wheeled vehicle feels mundane and comparatively low-tech.

$\endgroup$
5
  • $\begingroup$ "the pilot's license / certificat, air traffic control" is not very convincing. The development of computer technology is striking even now, but if it matches the level of such an engine ... In general, smart computers will solve all such problems. "a pressurized cabin, ice-proofing" is an interesting argument, but ... rather small. As is clear, such disadvantages also have opposite advantages. :) $\endgroup$ Nov 14, 2021 at 22:30
  • $\begingroup$ @Пилум While autopilot certainly makes the pilot license/ease of operation argument moot, aircraft is still significantly more complicated and expensive than ground vehicles. You need an enclosed cabin, pressurization, heating, emergency oxygen masks, comms, rain-, ice- and bird-proofing, redundancy, few types of external lights, etc. Significantly more legal requirements for development methodologies, testing, certification of the vehicle as airworthy, etc. If there's no ground-based air control, it gets even more complicated. Also, aircraft might be considered a luxury and taxed more. $\endgroup$
    – user31389
    Nov 16, 2021 at 16:26
  • $\begingroup$ Also, in science fiction they are often operated by actual humans, despite computers and autopilots existing. Even the one in your question looks like it's designed to be operated by a pilot. And it certainly doesn't look airworthy. $\endgroup$
    – user31389
    Nov 16, 2021 at 16:34
  • $\begingroup$ In general, you are unreasonably prolonging modern conditions - into the universal sci-fi future. As for computers, they can use exactly the total simplification of control, the automation, but still control of the pilot, and not just "autopilot" only. $\endgroup$ Nov 16, 2021 at 20:53
  • 1
    $\begingroup$ I'm only doing that when it comes to the autopilot. Other arguments are perfectly reasonable. Yes, you are right about the autopilots in reality. But sci-fi is not reality. You do whatever you want to suit your story. If you want your story to be science-based, you can say that autopilots are not used for legal reasons. This does not contradict science. For example you can say that when a pilot crashes a vehicle, the pilot is to blame, but when autopilot does it, its creators are to blame and must pay very large fines. Therefore it's not profitable to put autopilots in cheap vehicles. $\endgroup$
    – user31389
    Nov 19, 2021 at 18:30
0
$\begingroup$

If you want a Star Wars specific answer, you'd be better off asking in something like the sci-fi SE (or researching repulsorlift).

But if you want a general justification, you can simply go with these two simple properties:

  1. hovering higher off the ground requires more energy
  2. increasing the mass (size of vehicle, number of passengers, amount of cargo, etc) requires more energy to hover at a given height

In other words, small vehicles close to the ground require less power. That means a simpler/cheaper/smaller source of power. It probably also means lower maintenance costs in terms of components and expertise.

Another thing to consider is that your power source is going to be split between lift and propulsion. For a given energy output, that means that being near the surface lets you go faster.

As also mentioned, there is a safety factor. It's less catastrophic for the vehicle to fail 1 meter above the ground than 1km above the ground. This might not be as relevant in very heavily populated areas where you have easy access to parts and repairmen with specialized skills and tools for regular maintenance, but in very remote areas, you might want something simpler that you can easily maintain yourself.

And before you ask for a mechanism of lift: it's made up. Star Wars, Star Trek, etc, all have their own fictional approaches to this. My answer is assuming that whatever made-up mechanism is being used has the property that hovering higher = more power required.

$\endgroup$
0
$\begingroup$

Another possible explanation: They can fly but it's inefficient. The higher you go the more energy the repulsor needs. Perhaps this is even prohibitive--try to fly too high for too long and you overheat the drive.

No current technology can produce such craft so the drive is inherently handwavium, make it work how you want. (Yes, the ekrantoplan has been mentioned--it has a minimum speed for flight that's not much below it's cruise speed. It doesn't behave anything like the craft pictured.)

$\endgroup$
0
$\begingroup$

Just to give the (obvious) psychological answer... Humans think about travel in two dimensions; travel is conceived over a surface, not through a volume. The reasons for this are subtle, and related to the reason why ancient humans thought of the sky as a flat bowl: we are far more attuned (with respect to long distance) to front/back/left/right than to up/down.

So, when people want to go from point A to point B, they think about it in terms of travel over a (more or less) flat surface, just as though they were going to walk the distance, except faster. A car, speeder, floater, or other just-over-the-ground vehicle fits into that expectation nicely.

I'll add, for interest's sake, that sticking close to the ground is likely more efficient in all cases. The alternatives — trying to achieve lift (like an airplane) or relying entirely on thrust (like a rocket) — mean that substantial energy must be consumed merely overcoming the object's tendency to fall like a rock. A vehicle that has a relatively passive mechanism for keeping itself slightly off the ground (ground effects, wheels and springs, hovercraft air pressure, anti-gravity, etc) saves a tremendous amount of energy, and achieves most of the advantages of true flight. Further, it avoids the need for centralized landing areas designed to accommodate the huge inertia of a jet landing (aka a controlled fall) or the heat energy released by a rocket pushing back against the earth's gravitation.

$\endgroup$
1
  • $\begingroup$ "(like a rocket) — mean that substantial energy must be consumed merely overcoming the object's tendency to fall like a rock.", "anti-gravity, etc" - this is sounds contradictory. No matter how this device flies - it really flies. Just by the very ground. "hovercraft air pressure" and the like. - just not the case of this question. $\endgroup$ Nov 14, 2021 at 22:12

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .