If we develop repulsorlifts, where would they be used?

[FishInferno]

In all the sci-fi movies, people fly around in floating cars that don't need wings because humanity has developed repulsorlifts to defy gravity. I know that such a technology may not be possible, but assuming it was, where would they be used?

I have a few ideas:

-Flying cars, but there are surely drawbacks to this that I cannot think of.

-Embed them into the wings of fighter jets so they can VTOL without rotating their engine

-MAYBE some kind of space launch system

What do you think?

NOTE: this is not discussing whether repulsorlifts are possible, but how they would be used if they were

[StrandedonEarth]

Hoverboards!

They would also make for anti-repulsor-vehicle mines: Place one upside-down on the ground, and any repulsor vehicle passing over it will strobe and get shot into the air

[LordFerret]

Vimana of course, where the elite would live.

[theend3r]

Obvious drawbacks:

1. Enormous energy consumption
   
2. Difficult to eliminate sideways motion
   
3. Braking (similar problem to 2.)
   
4. Expensive, needs frequent (again expensive) repairs
   

Now the pros:

1. No friction => great for trains but we already use it that way
   
2. Comfortable, can overcome obstacles
   
3. Looks cool
   
4. Hoverboards (we have till October 21, 2015)
   

The drawbacks are significantly larger than the positives, especially for safety concerns - friction is good for cars.

[smjjames]

Hoverboards!

https://bestofthe80s.files.wordpress.com/2011/05/backtothefuture_hoverboard_01.jpg

They would also make for anti-repulsor-vehicle mines: Place one upside-down on the ground, and any repulsor vehicle passing over it will strobe and get shot into the air

Pink though?.....

[sojourner]

Obvious drawbacks:

1. Enormous energy consumption
   
2. Difficult to eliminate sideways motion
   
3. Braking (similar problem to 2.)
   
4. Expensive, needs frequent (again expensive) repairs
   

1. unknown. fictitious technology.

2. see #1

3. again, see #1

4. yet again, see #1

[theend3r]

1. unknown. fictitious technology.

2. see #1

3. again, see #1

4. yet again, see #1

Only #1 is unknown, really. The rest are rather obvious.

[Awaras]

1. unknown. fictitious technology.

2. see #1

3. again, see #1

4. yet again, see #1

Let's put it another way then:

1. Enormous energy consumption (well, similar to what it would take to lift the same weight using traditional means) OR a huge violation of the conservation of energy law which would allow stuff like perpetual motion machines.

Not very likely...

Edited May 20, 2015 by Awaras

[magnemoe]

Obvious drawbacks:

1. Enormous energy consumption
   
2. Difficult to eliminate sideways motion
   
3. Braking (similar problem to 2.)
   
4. Expensive, needs frequent (again expensive) repairs
   

Now the pros:

1. No friction => great for trains but we already use it that way
   
2. Comfortable, can overcome obstacles
   
3. Looks cool
   
4. Hoverboards (we have till October 21, 2015)
   

The drawbacks are significantly larger than the positives, especially for safety concerns - friction is good for cars.

Energy consumption depend on efficiency, if poor it would not let anything hover as heat buildup would limit effect.

If good it would replace helicopters as in any plane might be vtol, draw power from engines to power during takeoff, you use lifting surfaces once you get up to speed, everything from flying cars with stubby wings and an propeller to planes larger than existing.

Sideways movement can be solved with propellers or similar, controll surfaces then you have speed.

Not much interest in something skimming the ground outside of some boat types, military might want to keep low.

If not limited in height it would be nice as an launch system, might still make sense to replace boosters,

[ZetaX]

Let's put it another way then:

1. Enormous energy consumption (well, similar to what it would take to lift the same weight using traditional means) OR a huge violation of the conservation of energy law which would allow stuff like perpetual motion machines.

Not very likely...

Lifting them needs energy. Hovering itself does not use any energy per se. And the cool part about all this is that you can do the lifting like you want.

[Frozen_Heart]

Lifting them needs energy. Hovering itself does not use any energy per se. And the cool part about all this is that you can do the lifting like you want.

Hovering would require constant energy and very large amounts of energy. Earths gravity is always pulling down so you'd always need an upwards force to overcome it.

[ZetaX]

Hovering would require constant energy and very large amounts of energy. Earths gravity is always pulling down so you'd always need an upwards force to overcome it.

That's not how physics works. You don't need any energy at all to maintain distance. Examples of that are superconductors, the moon, and you not falling through the floor.

Force is neither power nor energy.

[YNM]

That's not how physics works. You don't need any energy at all to maintain distance. Examples of that are superconductors, the moon, and you not falling through the floor.

Force is neither power nor energy.

You do need them. Moon stores a heck of kinetic energy - the direction of the speed is continually changed (that's where the gravitational potential energy affect, or what I can guess), but KE is direction independent (so as long as the magnitude stays the same - if it changes, it goes to an ellipse). Superconductors makes it that way by residing in the minimum gradient (maybe ? I don't know which equations govern them). Floor gives a force back to you - the normal force. Normal force are needed to keep Newton from flying away from the ground or breaking it.

Apart from energy consumption... I would agree with hoverboards. Other than that, it could make my dream somewhat comes true - having a satellite that hovers over Earth's terminator ! Or continually above the pole...

[Fulbert]

They would also make for anti-repulsor-vehicle mines: Place one upside-down on the ground, and any repulsor vehicle passing over it will strobe and get shot into the air

I like it how the first (okay, the second) idea of utilizing this new technology is a weapon:-)

[ZetaX]

You do need them. Moon stores a heck of kinetic energy - the direction of the speed is continually changed (that's where the gravitational potential energy affect, or what I can guess), but KE is direction independent (so as long as the magnitude stays the same - if it changes, it goes to an ellipse). Superconductors makes it that way by residing in the minimum gradient (maybe ? I don't know which equations govern them). Floor gives a force back to you - the normal force. Normal force are needed to keep Newton from flying away from the ground or breaking it.

Why exactly do you think that you need to give me an explanation on how forces work after I responded to someone by explaining that one does not need _energy_ to _maintain_ distance¿ Neither of the things I mentioned use up any energy (apart from very small losses), but obviously all of them require forces to stay there; and they require energy to get there in the first place, but that's also irrelevant here.

[Stargate525]

Uses? Depends on how expensive they are.

If they're very expensive or finicky, I'd see them in cargo movement and industrial uses. Instead of a crane, you have a repulsor, and those massive dump trucks dump their wheels/treads and get repulsors.

If they're cheap, I'd imagine them everywhere; floaty desktop toys, replacements for sliding door wheels, wheelchairs, lawnmowers... I'd love to see someone cheat with a repulsor bat.

[heng]

next-gen Fat-Boys©! I'd buy one.

air bags for cars.

depending on size, gaming keyboards with really smooth key press feel.

f*cking mosquito swatters.

fall protection for breakable expensive stuff. like mobiles/cell phones, glasses, watches, me...

shock absorbers for high-end turn tables... a free floating dark side of the moon record? anyone?

[Karriz]

Why exactly do you think that you need to give me an explanation on how forces work after I responded to someone by explaining that one does not need _energy_ to _maintain_ distance¿ Neither of the things I mentioned use up any energy (apart from very small losses), but obviously all of them require forces to stay there; and they require energy to get there in the first place, but that's also irrelevant here.

I'm a bit confused. It requires a constant upwards force to hover, but since there's no movement, there's indeed no energy. But, it definitely does require power to hover.

And power is energy per time. So, how do we convert a constant newton force to watts?

[sojourner]

Let's put it another way then:

1. Enormous energy consumption (well, similar to what it would take to lift the same weight using traditional means) OR a huge violation of the conservation of energy law which would allow stuff like perpetual motion machines.

Not very likely...

Nope, #1 still applies. You can't make any assumptions, good or bad about a completely fictitious technology. Unless you're writing a science fiction story, then feel free to make the rules for the setting.

[ZetaX]

I'm a bit confused. It requires a constant upwards force to hover, but since there's no movement, there's indeed no energy. But, it definitely does require power to hover.

And power is energy per time. So, how do we convert a constant newton force to watts?

It does not definitely require power to hover. See those examples I gave. Hovering by pushing air/gases around requires power because you also create moving gasses. But that does not mean that every methode does so, we just don't know a better one in some conditions.

[YNM]

It does not definitely require power to hover. See those examples I gave. Hovering by pushing air/gases around requires power because you also create moving gasses. But that does not mean that every methode does so, we just don't know a better one in some conditions.

Hmm... Yeah, conservative energy. Although, systems where there's no net total energy changes often implies constant (or periodic) movement. No ? (like, gravitational system, atoms, while superconductors don't need to move around there should be some tendency to move...)

[ZetaX]

Hmm... Yeah, conservative energy. Although, systems where there's no net total energy changes often implies constant (or periodic) movement. No ? (like, gravitational system, atoms, while superconductors don't need to move around there should be some tendency to move...)

Not necessarily (but see the next paragraph). Superconductors are stable when floating, meaning that every (not too big) disturbance will be counteracted; but if you ignore everything (mostly inductive effects and friction) then it would keep swinging back and forth. In reality, it stops moving after some seconds. One can by the way float things at room temperature using diamagnetism; it even works with permanent magnets when using sufficiently diagmagnetic materials (pyrolithic graphite, bismuth).

On the other side, there is a mathematical theorem (http://en.wikipedia.org/wiki/Earnshaw%27s_theorem) that forbids stable and non-moving configurations of objects influenced by gravity and/or "usual" magnetism; the relevant part is that you only allow repulsion via dipoles, i.e. charges and magnetic poles, but not that some weird materials are repelled by both poles. You can cheat the system by e.g. using rotating objects as they are not counted as non-moving. Or you realise that electromagnetism allows for diamagnetism or even superconductors, rendering the assumption on the forces moot.

Thus (because the assumptions are almost true in most settings) that theorem still says that what you say is correct more often than not: most stable configurations need to move.