How Much Electricity Would It Take To Provide 1g For Scifi Artificial Gravity?

[Spacescifi]

If you were to meaure the force gravity is exerting on a typical floor inside a house with a bathroom, bedroom, and kitchen inside, how much electricity would it take to provide the power to to match that force?

 

I am not speaking by rotation. This will be either a hillariously high amount of energy to match the force gravity is providing per second on the floor or something less jaw dropping.

 

Will be amusing either way to learn.

 

[darthgently]

6 minutes ago, Spacescifi said:

If you were to meaure the force gravity is exerting on a typical floor inside a house with a bathroom, bedroom, and kitchen inside, how much electricity would it take to provide the power to to match that force?

 

I am not speaking by rotation. This will be either a hillariously high amount of energy to match the force gravity is providing per second on the floor or something less jaw dropping.

 

Will be amusing either way to learn.

 

Strangely, it will be in the neighborhood of the amount of energy that would be required to create the same amount of artificial spin gravity centrifugally

[mikegarrison]

Anywhere from infinite to zero, because artificial gravity does not exist.

[K^2]

It's just like energizing a magnet. A magnetic field has energy. You have to put that energy in somehow. Any objects within the field may be magnetized by the field, and that will add to the energy requirement, as they now gained potential energy relative to the magnet. That's the minimum you have to add. From there, it all depends on how efficient your setup is. A solenoid will drain power. A permanent magnet won't. A superconductor may require cooling, which is a power drain that had nothing to do with how much field it's generating.

Artificial gravity is much the same way. @darthgently is spot on with centrifugal gravity. That's real gravity and it plays by the same rules as any other methid would. We just know how to make it actually work. The more mass you have, the more energy it will take to get the wheel going. You're putting that potential energy in. If ships depart or arrive you might have to adjust that. Other than that, if the wheel is frictionless, it just keeps going. If there is a source of friction, you'll have to supply some power to maintain the spin. How much energy you'll actually spend? Depends on how efficient your setup is. If you can literally attach an electric motor, it will be very efficient. If it's rockets, not so much.

Other means of generating gravity will work by the same rules, but we have no idea how much overhead there will be for something practical. We know that it can be a lot. If you have to provide energy equivalent to mass energy sufficient to generate that gravity, it will be more energy than the civilization produced thus far. By a lot. We know this brute force method works, but it's not practical precisely due to energy requirement. Anything else will be between these extremes.

P.S. Completely forgot to add that acceleration is gravity. There is no distinction. That's part of why we can use the centrifuge as a benchmark. But linear acceleration also works. 1g gravity aboard a torchship is a real gravity. How much energy is that taking? A frigin' lot, but ot's energy you need to spend either way. So that's one more example.

Edited April 2, 2023 by K^2

[magnemoe]

Just now, darthgently said:

Strangely, it will be in the neighborhood of the amount of energy that would be required to create the same amount of artificial spin gravity centrifugally

Who is true, however the spin gravity is an one time expense, a gravity plate would demand this power all the time. 
I say it depends a lot on how it work, most "realistically" you have to accelerate the entire house. 
say 30 ton who would require 5.7 MW, if you somehow made the house immune and only accelerated the items you wanted to say 3 ton it would be 570 KW. 
So not something you want as you house power bill  But not insane 570 KW is 783 horsepower. 
Remember that sports cars are able to accelerate and brake at over one g and helicopters can fly. while being much less efficient than this gravity plate who I assumed was 100 % efficient. 

I say this would not be practical for creating gravity but would make huge flying stuff like aircraft carriers an reality, and obviously orbit capable crafts who was similar sized. 
Simply as with 1.25 g you would end up in orbit. 

[K^2]

2 minutes ago, magnemoe said:

I say it depends a lot on how it work, most "realistically" you have to accelerate the entire house.

Yeah, that's kind of the problem. We can put some bounds on how much or how little it can be, but without having a specific method in mind, you can't really say what it will be. Linear acceleration will add to the kinetic energy. Do we want that? Is it a waste? Can it be avoided to save on power requirements? All depends. We clearly can with rotation. Can you "rotate" in place without moving? There might be degrees of freedom we can tap into, but that gets uncomfortably close to the attempt of reinventing string theory. *big shrug*

[magnemoe]

25 minutes ago, K^2 said:

Yeah, that's kind of the problem. We can put some bounds on how much or how little it can be, but without having a specific method in mind, you can't really say what it will be. Linear acceleration will add to the kinetic energy. Do we want that? Is it a waste? Can it be avoided to save on power requirements? All depends. We clearly can with rotation. Can you "rotate" in place without moving? There might be degrees of freedom we can tap into, but that gets uncomfortably close to the attempt of reinventing string theory. *big shrug*

Agree, it would be much much more valuable if you can levitate heavy stuff even if you needed jet engines to move stuff around, or more fun lift stuff past the moon and play with gravity. 
And yes as you say its pretty easy to make this into an free energy machine.
On the other hand rotation is very simple and its only fail modes is structural integrity.
So you would use rotating habitats even if 1g torch ships was standard for passenger ships. 

Yes you might create 0 g on earth but if you could get into obit at current long range jet flights energy costs its just for amusement parks stuff. 

[Spacescifi]

I see. So to save power a more sensible scifi floor gravity plate would be smart. After all people need gravity... nothing else does.

So gravity plates would only provide gravity within the immediate radius where a person is standing or lying. Meaning if you throw something beyond it would float off till it hit a wall.

Edited April 2, 2023 by Spacescifi

[K^2]

1 hour ago, Spacescifi said:

So gravity plates would only provide gravity within the immediate radius where a person is standing or lying. Meaning if you throw something beyond it would float off till it hit a wall.

Well, therein lies the complexity of it all. I've mentioned magnetic fields above, primarily because people are familiar with magnets a bit more than electrostatic effects, but it is, indeed, the electrostatic forces that are an almost perfect analog for gravity. Even with gravity as immense as the Sun's, the difference from electrostatic forces is effects like precession of the orbit of Mercury, which is tiny all things considered. You really have to get to neutron star gravities before it really becomes important.

So with that in mind, you can pretty much apply basic electrodynamics to gravity. And just like with electric fields, there are rules you have to follow. Relevant one here is the one about the field divergence. I won't go into the math, but the way you picture this is by drawing the field lines. Any time a field line stops or starts, you have non-zero divergence. So you can't have the field lines just start at the gravity plate. That would require the plate to be very massive. How massive? Well, the Earth needs all the mass that's located directly under your feet to generate 1g of gravity, so you'd need that much mass. I hope you agree that's not remotely practical.

Because of how much mass we need for even the tiny amount of field divergence, to build a practical "gravity plate" it would have to be divergence-free. This is where we go back to magnets analogy, because magnetic field also has zero divergence. You achieve this by looping all the field lines back on themselves. If you look at any picture of the magnetic fields around a magnet, you'll see the field lines pass through the magnet, then expand out at either pole, and then wrap around outside of the magnet creating a sort of a field vortex around that magnet. We'd have to do something similar. We'd want the plate to attract things above it, repel them from below, but then around the edges, the situation would be reversed. It'd be a much weaker field, rapidly dropping as you move further away (as an inverse cube) acting in the opposite direction, applying a bit of gravity in the upwards direction. The net gravity across a slice passing through the plate would be zero, with positive 1g near the plate, and negative, but much weaker gravity, far away from the plate, dropping to zero as you get far enough out.

There are a whole lot of additional complications here. Like, getting the gravity field to turn like this requires it to have a non-zero vorticity. Or curl, mathematically speaking. There's a simple way to generate that without bending space-time, but that requires accelerating a lot of mass at very high rate, so again, not practical in the least. Whether this can be a stable system at all is unknown. There is a famous result from mean field theory that the gravity allows for a torsion term. Einstein set it to zero in his field equations, either because he missed them or because he saw no evidence of them. To this day, we have no idea if they are physical. There is no known space-time torsion "charge". If we had one and could bend it into a loop shape without causing problems, you would, theoretically, have exactly what you want, a gravity plate with properties described above. It might even require no upkeep. It'd just exist, like a permanent magnet. You could install it on a ship and fly around with it. You'd just have to be careful about two ships with such plates passing close, because they'd behave exactly like you'd expect a pair of giant magnets to. But this goes of into such deep hypotheticals that it's pointless to speculate further. We have zero evidence that this is a physical phenomenon and people have looked. So we might be out of luck with this, and there is no known alternative.

[Spacescifi]

9 minutes ago, K^2 said:

Well, therein lies the complexity of it all. I've mentioned magnetic fields above, primarily because people are familiar with magnets a bit more than electrostatic effects, but it is, indeed, the electrostatic forces that are an almost perfect analog for gravity. Even with gravity as immense as the Sun's, the difference from electrostatic forces is effects like precession of the orbit of Mercury, which is tiny all things considered. You really have to get to neutron star gravities before it really becomes important.

So with that in mind, you can pretty much apply basic electrodynamics to gravity. And just like with electric fields, there are rules you have to follow. Relevant one here is the one about the field divergence. I won't go into the math, but the way you picture this is by drawing the field lines. Any time a field line stops or starts, you have non-zero divergence. So you can't have the field lines just start at the gravity plate. That would require the plate to be very massive. How massive? Well, the Earth needs all the mass that's located directly under your feet to generate 1g of gravity, so you'd need that much mass. I hope you agree that's not remotely practical.

Because of how much mass we need for even the tiny amount of field divergence, to build a practical "gravity plate" it would have to be divergence-free. This is where we go back to magnets analogy, because magnetic field also has zero divergence. You achieve this by looping all the field lines back on themselves. If you look at any picture of the magnetic fields around a magnet, you'll see the field lines pass through the magnet, then expand out at either pole, and then wrap around outside of the magnet creating a sort of a field vortex around that magnet. We'd have to do something similar. We'd want the plate to attract things above it, repel them from below, but then around the edges, the situation would be reversed. It'd be a much weaker field, rapidly dropping as you move further away (as an inverse cube) acting in the opposite direction, applying a bit of gravity in the upwards direction. The net gravity across a slice passing through the plate would be zero, with positive 1g near the plate, and negative, but much weaker gravity, far away from the plate, dropping to zero as you get far enough out.

There are a whole lot of additional complications here. Like, getting the gravity field to turn like this requires it to have a non-zero vorticity. Or curl, mathematically speaking. There's a simple way to generate that without bending space-time, but that requires accelerating a lot of mass at very high rate, so again, not practical in the least. Whether this can be a stable system at all is unknown. There is a famous result from mean field theory that the gravity allows for a torsion term. Einstein set it to zero in his field equations, either because he missed them or because he saw no evidence of them. To this day, we have no idea if they are physical. There is no known space-time torsion "charge". If we had one and could bend it into a loop shape without causing problems, you would, theoretically, have exactly what you want, a gravity plate with properties described above. It might even require no upkeep. It'd just exist, like a permanent magnet. You could install it on a ship and fly around with it. You'd just have to be careful about two ships with such plates passing close, because they'd behave exactly like you'd expect a pair of giant magnets to. But this goes of into such deep hypotheticals that it's pointless to speculate further. We have zero evidence that this is a physical phenomenon and people have looked. So we might be out of luck with this, and there is no known alternative.

Oh we are in scifi territory already.

I just wondered about the energy cost of it all. But I can live with it if gravity plating only tracks the immediate crew positions.

 

That said, we are in the realm of gravity generation and control.

One interesting superpower we could emulate if we could do that is tactile kinesis. Moving mass over the gravity generating object anyway we wish.

 

If done fast enough you could use it for rocketry... very simply too. Just get a tank of any liquid you want and pump it into a sprayer down the throat of a rocket nozzle made of the tactile kinetic nozzle. Which would accelerate the liquid so fast it would become a relativistic plasma plume the nozzle accelerated it.

Basically an artificial gravity nozzle insteas of a magnetic one.

AG drive: Pros: Any propellant you want will work. Cons: Awful lot of power to power it.

[K^2]

47 minutes ago, Spacescifi said:

If done fast enough you could use it for rocketry... very simply too.

That might actually be easier, because here you're fine with it being pulsed. If you take a gyro, spin it very, very fast, and then start rotating its cage in a perpendicular direction, you will generate a small amount of artificial gravity along the surface of the gyro. This artificial gravity will rotate along with the cage, meaning it will only point where you want it for a brief moment, and will point in the exact opposite direction at some other point in time (just like before, average gravity being zero makes it a lot easier...), but if you time your propellant in pulses, you can get thrust out of it. Will it be a lot? With anything a physical gyro can survive, no. Actually, I don't think it'd even be measurable with anything we can practically build right now. But we might be able to find some sort of an effect that lets us bottle an enormous quantity of angular momentum in something without it physically spinning. Not only would it make for amazing reaction wheels, but we'd be able to do something like this with it.

I still don't think it'd be useful for actual rocket propulsion, as with that level of tech, we ought to have better options, but just the concept of being able to briefly pulse gravity for various needs might be useful in some other applications, and that might actually be achievable without us discovering fundamentally new physics. Just some exotic materials that may or may not be possible.

[RCgothic]

Gravity is a field.

Setting up a gravity field would take energy at least equivalent to moving every massive object within it from infinity to its position inside the field, because work is energy is force times distance.

How much energy this is depends on the size of the field. If the field drops from 1g to ~0 over 10m it could be as little as 12.5J/kg for objects at the 1g level. Less for objects further away, more for any objects below the "deck". For this reason the design would probably need to minimise the mass between the artificial gravity generator and the useful gravity zone.

The energy put into establishing the field may be regeneratively recovered when it's disestablished.

For comparison 1J isn't a lot. It takes 4200J to heat 1kg of water by 1°C.

It needn't take any energy to maintain a gravity field either. Objects at rest within a field aren't having any work done upon them. The system would need to supply the energy for any movement of objects.

The only question then is how efficiently your gravity generator can convert electrical power into gravity fields and keep them operating. And as this is mythic tech with no known, this could be anything from next to nothing to "needs energy totalling the mass of a planetoid with equivalent surface gravity".

[kerbiloid]

Any type of antigravity needs as much power as a smartphone consumes while describing this antigravity in a sci-fi text.

[Terwin]

18 hours ago, Spacescifi said:

I see. So to save power a more sensible scifi floor gravity plate would be smart. After all people need gravity... nothing else does.

So gravity plates would only provide gravity within the immediate radius where a person is standing or lying. Meaning if you throw something beyond it would float off till it hit a wall.

If you only need 'gravity' for people, then just use steel plates on the floor and magnets in your boots.

Simple, practical, and the energy requirements are low enough that it can be provided by the muscles of the person(mostly for lifting your foot away from the floor)

You should even be able to tune the strength of the magnets to minimize or eliminate muscle atrophy in the legs(even if the muscles are likely to re-allocate a fair bit over time).  

This may even act as 'training wheels' for people not accustomed to microgravity for long duration flights on large vessels(like a starship to mars).

[kerbiloid]

The blood won't be pulled down from top, so all cardiovascular and other health problems will stay.

The objects, including the dust will stay in air. The CO2 will stay around the humans.

The magnet boots solve only the tiniest problem, the humans won't fly.
Though, they should be keeping eyes on their ankles. The sole is attracted to the floor, while the whole body inertia tries to revolve around the ankle.
The Expanse is a rather poor piece of science.

[sevenperforce]

As usual, the energy requirements (whether electrical or otherwise) are completely dependent on the mechanism used, and since we don't have a mechanism presently, this becomes nonsensical pretty quickly.

However, we could look at potential mechanisms, perhaps by reversing systems that have been proposed to negate the effects of gravity on Earth. A space fountain is one concept to create a space elevator without needing high tensile strength or a geostationary-distance tether:

In theory, you could imagine some sort of yet-unknown particle with a very high interaction cross-section that would freely pass through objects but produce significant drag on those objects, accelerating them downward. Then you would just need a plate in the ceiling and a plate in the floor, and you'd fire these particles out of the ceiling, catch them in the floor and deflect them through a loop back up to the ceiling, and repeat. Something like this:

That would be your "active antigravity" concept. Presumably you would be able to recycle the majority of the particle energy.