Could artificial gravity help send large spacecrafts into space?

Question

In science fiction technology that induces a gravitational pull is often sidelined as just a convenient way of getting people to walk on a spacecraft. The implications of gravity that can be turned on and off are actually much bigger than that. Theoretically you could help launch ships into space by using a satellite equipped with an artificial gravity generator to lighten the gravitational pull in an area. This could allow to save a considerable amount of fuel or in this case launch monstrously large ships into space. Spacecrafts the size of multiple football fields could be constructed on earth, without the need to send rockets back and forth into space to assemble pieces bit by bit. On paper this all sounds fantastic, but realistically it would be much trickier than that.

The handwavium generator is a theoretical device that can generate varying magnitudes of gravitational force. You could set it to moon gravity (1.625 m/s2 about 0.166 ɡ) or earth gravity (9,807 m/s² exactly 1g) at the flick of a switch. The device can generate gravity on par with a planet but doesn't have the same radius, so naturally the area of effect is smaller.

Obviously I don't want to set it in orbit to 1g to cancel out gravity completely, or worse have it come crashing into earth. It would have to be half or less than 1g to not cause unwanted destruction on the surface. The predicted effects would be a localised expansion of the atmosphere, a drop in sea levels and of course everything would seem lighter. The idea is that the artificial gravity field dips just on the earths surface on the linear center, to affect only the region that needs to be lightened.

What would permit such a system to work? Are there any unforeseen consequences?

Edit: This isn’t a reality check. “Gravity a interacts with gravity b, can this be used?” is what is being asked. Obviously creating gravity is fiction. Please review your answers.

Answer 1

G-crane

You won't have to put the generator in orbit permanently, but you'll want to avoid operating this generator on the planet surface ! Because of the short distance, it will have a devastating effect on surrounding matter. Pull your space ship up (G+), rather than pushing it (G-).

To prepare for lifting a ship into orbit, your handwavium generator could first lift itself, e.g. 50m above the ship's ceiling. Then move the ship under it.

When the G-crane is switched on, it will pull anything off the surface, that resides in its vicinity. Not only the ship. The ship will need some armour, because the weight of the matter will put pressure. The trick to minimize taking matter along: while the cargo accelerates upward, the generator should move up, along with it. While the generator elevates the space ship "hanging" under it, its influence on the planet surface will rapidly diminish (G force diminishes with square of altitude)

The first few minutes of the lifting process will cause near objects, sand, dust, water and atmosphere near the surface to move upward as well. The lifting will cause large amounts of matter to stick on the bottom of the ship. The force should be maintained, until the ship is far enough up in space, to prevent sticking matter from falling back too early. When the generator is switched off and your ship is in orbit, the material sticking to the ship will detach and burn up in the atmosphere.

It is still advisable to move the whole operation into flat, uninhabited territory like a salt lake. The initial move will cause a crater. Underways, a spontaneous low pressure area is formed under the ship. Strong local airflow could cause tornados to occur.. maybe other weather effects..

Answer 2

What would permit such a system to work?

Magic, plain and simple. What you're asking for is so far away from any plausible scientific or engineering feat there's not really any other answer. Even in scifi, the antigravity fields tend to be confined to very small volumes, so this is even more unsound than star trek or star wars.

Are there any unforeseen consequences?

Your plan is almost entirely made of unforseen consequences.

Consequence the first, for example: once the gravity beneath your satellite is neutralised, what keeps your satellite in its orbit? Without gravity, it'll shoot off on a tangent away from Earth at orbital velocity until the gravity-neutralizing effect stops working. A very powerful rocket would be needed for station keeping.

Speaking of station keeping, you'll need to have the area of effect more-or-less centred on the thing you're lifting all the way up. This means sticking your lifting satellite in geosync orbit, or having it in a forced orbit at low altitude (requiring very powerful rockets) or on some kind of dynamic orbital ring.

There will be some interesting atmospheric disruption along the zone that the antigravity system affects. I'm not entirely certain what this will look like... there will be a general upward movement as the stuff at the top escapes into space and the high pressure stuff further down tries to equalise with the lower pressure stuff above it and air will be sucked in from the surroundings at lower level and blown out at higher levels, possibly forming some kind of large toroidal vortex that might actually form a tornado. It'll also be subject to interesting coriolis effects if you're not pointing an antigravity beam along the Earth's axis of rotation, but this isn't a large effect (see this answer of mine for some discussion of coriolis effects for things suddenly not subject to gravity).

What happens to the ground (or ocean) in the volume of effect is probably a bit more dramatic and destructive. I think the ocean will fountain up, pushed by pressure from below with substantially more force than the air, because there's potentially a lot more ocean pushing down and providing pressure from below. I haven't the faintest idea if the tensile strength of the crust and upper mantle, and the viscosity of the mantle in general is enough to prevent the formation of a giant magma fountain but, y'know, it might not be.

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The biggest issue is the whole "conservation of energy" thing. If you can just conjure energy from nowhere by lifting stuff up magically for free, then turning the gravity back on, then you've broken huge amounts of physics, and I can't help you. Clearly, if you can create free energy then merely using this thing for spacelaunch and keeping your spacecraft comfy seems a bit silly... you should be blasting yourself up the Kardashev scale.

(speaking of breaking physics, what happens if you use one of these things on a black hole? can you now cross back through an event horizon without waiting for the black hole to evaporate?)

If you can't create free energy, then you'll have to pay for every single joule of gravitational potential energy you're imbuing the material you're lifting... this would be about 3.4 MJ/kg for lifting something from the surface to the altitude of the ISS. Obviously lifting any useful amount of mass requires a large amount of energy, and the mass of a column with cross-sectional area 1m² reaching all the way down to the Earth's core would be gigantic and need such a powerful energy source as to effectively be unfeasible.

Clearly you need some kind of additional constraints on your AG system... it nullifies gravity between two plates, perhaps. Then you can stick one of the plates in orbit and one on the ground, and only have to lift the atmosphere (10 tonnes per square metre at the surface) plus the weight of your spacecraft. If you were clever, you could build a dynamically suspended tube (maybe using a space fountain, or maybe the antigravity system could do this trick too) so as to prevent lateral air movement during operation, preventing the formation of a tornado.

Suddenly though, if you can make a confined gravity nullification system then maybe you can simply make a box that renders its contents effectively massless (though you might wanna consider how inertia works when moving something confined in this way, because I'm not gonna touch that problem here) and just attach that to a regular spacelaunch system. Sure, you can't lift football-field sized things into orbit, but on the other hand you can do all sorts of other neat things that don't break the local atmosphere or crust. You have now more or less re-invented cavorite, or as was pointed out by DWKraus, the spindizzy, or any number of their descendents.

Answer 3

It is astonishing how much we know about gravity, and at the same time not know what it really is.

We can see it is an observation of a warping of spacetime inwards towards regions of higher mass. We can calculate its effect on objects in terms of movement and time. That's about all we know.

We don't actually know how it works, or how gravity (General Relativity) relates to the Standard Model. Many posit that if we can find this link, a theory of Quantum Gravity, it may yet yield developments that could result in our ability to manipulate it.

In your scenario, this is sidestepped, but this link would inform the consequences of your system. There are several predominant theories currently being studied that attempts to reconcile it, such as Loop Quantum Gravity or String Theory, but no current experiments can fully confirm or rule them out - or even if they are on the right track.

So for your launch assist system to work:

• You may need to develop a tested theory of Quantum Gravity, to enable your satellites to be designed to manipulate regions of space using this theory
• You would need to understand how to alter SpaceTime, and what 'time and space' is (properties of our universe currently in dispute), to enable velocities and masses to be controlled, and a way to control it.
• Apart from the theory, your satellites need also to be practical. They presumably need energy to do this, and the energy required may need to be colossal.
• How it affects the surrounding gravitational fields (or how it bends SpaceTime) and affects Earths own SpaceTime bending is unknown, as we don't have a working theory.

Such effects are not observed in nature, and it is not known if bending away from dense regions is even contemplatable. There may be yet a physical limitation of our universe that prevents anti-gravity - we just don't know.

Answer 4

• Perturbs the orbits of every other satellite badly. Gravity has the longest range of any fundamental force. Even making the satellites point gravitating masses only subtracts off the radius of the Earth from their effective range, given that 1 g is the nominal gravitational acceleration at the surface of the Earth.
• Perturbs the orbit of the Moon itself. 1 g is straight-up acceleration, not thrust, and therefore is not proportional to mass. It is proportional to distance and these satellites are passing closer to the Moon than the Earth so you have the n-body problem to solve.
• Probably screws up weather patterns and tides beneath it pretty good, with global effects.
• Increases atmospheric escape to space quite a bit
• While it does null gravity in a zone between the satellites and Earth, then you have to fight the gravity of both the satellites and the Earth once you try to reach an orbit above them. TANSTAAFL.

Answer 5

The system you propose is fiction and has nothing to do with scientific fact. There is nothing wrong with that if you are writing a work of fiction, but remember it is a fiction.

If such an anti gravity device were to become possible it would enable perpetual motion as water (for example) could be drawn up when the device was switched on and then allowed to fall through a turbine when the device was switched off. But this is just one example problem the whole idea of an anti gravity device would drive a coach and horses through the entirety of modern physics.

Answer 6

In order to not be a perpetual motion machine, the device consumes power based on how much work it needs to do. So, for people walking around on a deck, you just need a small amount of buffering to handle short term variations in various objects rising and falling a small amount, but at the end of the day it tends to cancel out.

But for launching something, using a tractor or repeller beam, it requires as much energy as the change in potential energy you are effecting. To lift a ship and let it get away, you must supply as much power as you would with any normal means of lifting the ship. Now, on the deck situation we assumed that it works in reverse, that falling objects in the field can give energy back to it, at least if it's re-used quickly. For a busy space port, they have as many incoming ships as departing ships, and can make use of the same principle on a larger scale. Traffic control tries to balance it out so that breaking the falling ships transfers power to the departing ships.

a field between two plates

My own idea for ship-based gravity that avoids the issues of messing up satellites etc. and has some other advantages is that the artificial gravity requires two plates, and produces a uniform field between them. This is analogous to the electric field between two charged plates. People on the deck will feel a constant gravity, but nothing happens beyond the bounding plates.

For launching something, you let it accelerate to the "bottom" plate and then escape, by opening a hole in that spot. Again, it's analogous to using an electric field, and it requires power to accelerate the object.

Answer 7

My enjoyment of stories involving artificial gravity on a space craft has always assumed that it was not actually gravity of some kind (maybe it's tricks of inertia, force fields, etc), exactly for the reason you propose. The ability to create actual gravity fields would have far reaching effects, and some of them devastatingly dangerous.

We first need to discuss how real gravity works. Gravity is a natural property of all matter. All matter attracts to all other matter. The weird part is that it's an extremely weak force, except as more matter clumps together, the gravitational force increases. More massive objects exert more gravitational force than less massive objects. It's even weirder that gravitational force between two objects increases as the distance decreases. Two objects approaching each other propelled only by their gravity will accelerate as they get closer together. This is why gravity is expressed in distance per time squared.

It's not necessary to go into the exact math (mostly because I don't understand it, lol), but it's necessary to know that gravity is based on mass, is stronger with more mass, and is exponentially stronger with linear decreases in distance between two objects.

For true artificial gravity, there's really only one conception: an exact point in space that, with respect to gravity, imitates the center of mass of an object. In the plainest understanding, the machine targets a point in space that then attracts all other matter to that point with an actual gravity field.

Where it gets tricky (meaning, using such tech effectively), is that gravity is mathematically tied to the mass of the object. If you wanted to lift by gravity with the same force as earth's gravity, then you'd need a massive point that matches earth. But suddenly dropping an earth weighted point in the solar system would have obvious devastating effects. In fact, it would be so bad that the only use for that would be to destroy planetary environments.

Where it might be an actually usable technology is if it's possible that a mass can be big enough that when in close proximity it would attract nearby objects at greater than planetary gravity, but would not be massive enough that it would meaningfully affect the planet itself. To make this truly useful, this technology would have to be able to move the artificial gravity point so as to keep a consistent pull on the target object. So I imagine a massive point, with virtually no volume, that you can place in extremely close proximity to an object, and as that point pulls the object, you move the point in your desired direction.

Depending on your readers, maybe you can hand-wave this as possible. To actually find out, you'd really have to ask a physicist. My lay-understanding has me believing that the math would punch out unfavorably. It would be intensive pull at only a few millimeters, and virtually none at only a few centimeters. If we put such a force above your head, it'd be more likely to make you dizzy before actually lifting you in the air.

So anything you lift would need a specially designed harness. The harness has a bit of mass which is the target, and when it moves, it pulls by attachments your actual target object. You couldn't just grab whatever you want. Every "gravity move" would require planning and preparation. Lifting an Earth built space station would require a very small mass, like a golf ball, that could attach to and then lift the entire station. Sounds unlikely, so you'd have to add like a thousand golf balls all over and inside the station, and then target them all in unison. Holy crap, this is getting complicated!

But if it's possible, then all the terrible side effects go away. That's great!

Another interesting use would be propulsion, both on planet and in space. You could put this tech in virtually every vehicle, provided the vehicles are designed to have the target "golf balls". This also illuminates how much easier it is to use if the gravity machine is attached to the target it's trying to move. The gravity machine would no longer need to be able to move the gravity point. Instead, it would only need to be able to create the gravity point in a specific space relative to itself.

Answer 8

ASSUMPTION

Assume gravity fields behave similarly to magnetic fields in that we can send some thing through a wire/pipe to generate excess gravity field than what you would expect and follows a sort of right-hand rule. (Perhaps through relativistic mass gain? Maybe a little fantastic there!)

THE MECHANISM: SOLENOID AND FIELD NEGATION

Have you ever heard of a solenoid? It does this nifty thing where the magnetic field inside is very strong but practically non-existent on the outside. (Try using this right-hand rule on a wire in solenoid configuration to see why!) We could use the above mechanic to negate most/nearly all the mass of a spaceship by having our gravity pipe wrap around the spaceship and produce a gravity field opposing the dominate one (a.k.a. Earth, the nearest major gravitational mass).

Now that your spaceship has the equivalent mass of some piping, or maybe even negative effective mass, it is pretty easy to zoom around!

Bonus points: Since you are negating mass, fast-as-light travel becomes much more realistic. You may even get away with things like an Alcubierre_drive. (Okay, if these fields are generated via star-trek like nacelles, you place one in front and one behind you, not side-to-side. Funny looking ships ensue!)

This, of course, assumes you can producing the opposing gravitational field is less 'expensive' (in terms of energy, cost, etc.) than simply adding more rockets/fuel.

OTHER APPLICATIONS

Hey, why stop with something so mundane as space travel? If you go into a deep enough gravitational field, time starts acting odd (due to a theory of relativity!) and you can effectively put people into 'stasis'! (It's not cryo-sleep, its gravo-sleep!)

What about zero-g architecture; why not live in cities in the sky if we can power anti-grav stuff with, say, nuclear fission/fusion? What about floating solar power plants to beam stuff down into cities?

Grav guns (perhaps ship based?) and grav traps also become things. One of these solenoids could be incorporated to a launcher, while a straight cord could increase gravity to "pin" people/objects/vehicles down.

Grav-mining may also be a thing- rocks are much easier to move when they weigh less. So maybe a mining operation lifts rocks in volume, miners 'sift' through it, and then they simply de-activate the grav field, letting the remainder simply fall back in place.

I guess what I am saying is that the ability to generate gravitational fields, even if it does require large (but not unmanageable) amounts of energy, is a game changer for transport, weapons, architecture, mining, politics, humanities, and more. It changes so much.

Answer 9

As others state, it seems your ideas are pretty far from our current understanding. However, as we're world building, let's imagine we can have an "electro-gravity" device, that when powered up "makes" gravity, in the same way as an electromagnet "makes" magnetism.

The first assumption is that you can reverse the polarity of the gravity. That's a rather big one, as (so far, I think I'm right in saying...) we've never observed or really even postulated the occurrence of anti-gravity. Therefore, to get your object on Earth into space, you'd have to have your grav-o-matic in space to begin with. You could turn it on, create 1G and then enjoy all manner of objects from the surface of the earth (including the atmosphere), in orbit around the Earth, and then even in orbit around the Sun all starting to head your way.

That leads on to the next assumption: you'd need to be able to direct your gravity into a "beam", and ideally to a specific distance. Here again, we're a long way from known physics. Without making it directional though, you have other problems. By example, lets we put your grav-o-matic in space, and set it up for 1G. That "neutralises" the gravity on the surface of the Earth below the gravo-matic. However, gravity is only zero at infinite distance, so on the back side of the Earth, the gravity is now 2G. Likewise, the gravity on the space-side of the grav-o-matic is 1G, plus the 1G from the Earth (so 2G again). Say nothing of the gravitational effects on your grav-o-matic itself, which will most definitely be headed Earth-ward when switched on.

Suffice to say, manipulation of gravity is seemingly simple and convenient yet makes, arguably, the most complex problems of world building.

Since you mention handwaving, perhaps instead you can conjure up some sort of super-magnetic material (that perhaps uses some other force, not traditional magnetism). Now your grav-o-matic doesn't generate gravity, it generates this other force, which "pulls" the material (with the thing you want to launch attached) into space. Now the force that leaks into space doesn't affect anything except more of the special material. Even this is full of "plot holes", but as I say, this all presents a lot of challenges.

Answer 10

I've used something like this concept in a worldbuilding project before! The idea was Humanity never really abandoned rocket technology and we essentially railgunned all of our ships into orbit. That was it. Brilliant, ham-fisted efficiency. The ships were AI-guided to a space elevator where their crew was awaiting their ship, since the G-forces of getting catapulted into orbit would Probably Kill You. I later abandoned the concept and went with a lower-power jump drive that sent the ships most of the way out of the planet's gravity well, but for a time I almost made it work. My idea for an artificial gravity-assisted launch would probably be in a similar vein, but gravity being gravity, it's a slightly more difficult of a concept than just launching spaceships into orbit from a giant cannon.

As far as the similarities go, I would say they begin and end with the general concept; generate enough force, and it sends your ship into open space real nice and quick. Way easier than all the nonsense with orbits and gravity and what-not. Where it gets complicated with artificial gravity, I would say, is how its generated, and also the theoretical physics question of 'how do two completely different gravity systems interact with one another when one is a planet and one is generating enough gravity to both counterract the influence of gravity on the ship and reverse it enough to get it offworld'. I have some issues here before I expand on this further.

Artificial gravity really only ever works inside large space structures such as space stations or even really large spaceships with those big spinning rings, via centripetal acceleration. This works because they're in an enclosed, localized space immersed in zero gravity-and even then, there's a lot of if's and maybes involved and most sci fi worldbuilders ime just apply a heavy topical spread of handwavium cream. This specifically, though, could not really happen in the real world as we understand it currently. This is essentially the reverse of a thruster on an incredibly large scale-instead of creating a stream of mass in one direction that pushes the mass it's connected to in another, you're asking all the force to move the mass as it moves out. This would have to both negate and then counterract the planet's gravity, and even then be focused enough to push the large craft directly up, with a somewhat controlled spead as to not launch it into a dangerous trajectory.

With that out of the way, let's make it work with my favorite worldbuilding tool: rebranded sci-fi themed magic. We have a payload and a need to move it using artificial gravity. I would probably go about this by havving four large pylons denoting the altered gravity zone. Depending on how large your large spaceships are, this could be part of a planetary spaceport or a large part of the ocean that giant spacecrafts occasionally emerge from like cosmic horrors rising to reclaim the universe. This zone would somehow create a sort of direct beam that would push the spacecraft from the surface and out into space (Maybe it's enerated by the pylons? The gravity machine might be located directly underneath the landing pad?). You could call this gravity, I guess, but functionally it's more of a reverse tractor beam that I'm visualizing - which would most definitely have to work through magical means, but that's not the point here.

Another thing you could do is have small, artificial gravity-propelled drones work like tugboats, literally pulling the ships into space. They might also be further assisted by smaller objects that attach to the ship and propell it as well, to reduce the strain on the main drone. and operate faster.

This is completely unrealistic, unfortunately, but it still is a very interesting concept and I hope that my responses could help you come up with a solution! [: