Many sci-fi words use anti-gravity or artificial gravity to manipulate the weight of their ships making flight much easier. Wikipedia even has an article on it which discusses several attempts to make objects float.

The main approaches seem to be:

  • Gravity shields
  • Gyroscopes
  • Warp drives
  • Superconductors
  • Exotic Matter

Which of these techniques (or any other) is most feasible to allow large ships to float into, out of and fly around within a planet's atmosphere?

I'm not after hard science (as the technology has not been invented yet), I'm after an evaluation of which approach to solving this problem is most feasible.

What is the most scientifically likely method of making a craft of a thousand tons (for the sake of argument) float?

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    Gyroscopes? Really? Is that a real suggestion or crazy crystal people suggestion? – Tim B Nov 19 '14 at 10:06
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    Some other possible ideas that are not directly antigravity: Superconductors This might be a bit wild but you could use really really efficient superconductors that cause a ship to float in the Earth's magnetic field. This is very pseudo-physics because we're miles away from superconductors that powerful. Exotic Matter Again playing with pseudo-physics topics you could use a collection of exotic matter with equal or near-equal mass to an object to cause that object to float. – sydan Nov 19 '14 at 10:07
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    When you say you are "not after hard science", then the only possible answer is "whichever you want to be most feasible" – Philipp Nov 19 '14 at 19:31
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    A craft of a thousand tons and floats? Easy. How about 94000 tons with no trouble floating! – JDługosz Jan 28 '15 at 7:01
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    @TimB At least it's slightly better than "magnets" – 2012rcampion Sep 25 '15 at 22:03
up vote 2 down vote accepted

I'll go out on a further limb here.

It's well known that gravity is the significantly weaker of the 4 forces by an exponential factor compared to the other 3. String theory (or at least attempts at explaining this using string theory) states that gravity could be acting through several other dimensions than just the 3 we can observe thus greatly expanding the distance involved for gravity compared to the other forces. These extra dimensional spaces are microscopic in size, but the full addition of all of these dimensions add up and greatly affect gravity.

With this in mind (and using very futuristic technologies)

  1. Bombard these extra dimensions with energy to either increase their size or their number. This effectively increases the distance between two objects when calculating gravity. These dimensions could be stacked upon one another...ie, a microscopic unit of our space contains other dimensions and in turn a microscopic unit of this dimension contains other dimensions (and so on for 7 to 11 levels)... so expanding the bottom level of this dimension hierarchy by a factor of 10 could have an astonishing effect. The value of G is calculated using a distance to the 'center' of the earth's mass in the 10$^6$ range. If we were to increase the bottom of this dimensional hierarchy by a factor of 10 over a range of 1 meter, we could be effectively increasing the distance between two objects by a factor of 10$^7$ up to 10$^{11}$, effectively negating gravity compared to air resistance. SO this is increasing the distance between the two objects and effecting the space between the object and earth itself. Heh, no clue what this would do if the moon was to cross over this distance effect as it's affecting the distance between any objects between this area of increased dimensional space. Edit : if it's the 10$^{11}$ number, this would even have a noticeable effect between the earth and sun. Second edit : This could also have an interesting affect on weather and cloud patterns as there is now an area of air that isn't being affected by gravity either. If there was a definable edge to this effect, you would have negligible gravity for one step and then a return to regular gravity in another... flight would be quite flaky and hard to control producing sporadic movements as you leave and reenter the effects of gravity.

  2. Close off these dimensions entirely for the mass of the space ship. If gravity acts through these other dimensions and these dimensions are blocked, theoretically, would we have 0 gravitational pull towards this full mass of the ship. Instead of having a space between the object and the earth, this effect would be directly on the object and not on other objects experiencing the increased gravitational distance.

I think I've confused myself in this explanation around 10$^{11}$ times.

  • I like this solution, it ties into gravity/time logic which most people have at least heard of them bamboozles them with science! – Liath Nov 20 '14 at 8:30
  • @liath - Lets say the area effected (#1 above) is now a 1m space spanning a 10^7 meter distance...light travelling through this would either accelerate to well past the speed of light(?) or it'd take a significant amount of time to travel through. I'd imagine this would make the affected area look black as light is in transit through it. Items entering it could also be accelerated, applying time, length, and mass dilatation effects to them...might be the same effects as entering the horizon of a black hole. So much unknown lying in unproven theory that an author is really free to define it. – Twelfth Nov 20 '14 at 20:05
  • I'm marking this as the answer because although perhaps not the most scientifically sound the I find the solution the most intriguing and "Accepting doesn't mean it's the best answer, it just means that it worked for the person who asked" – Liath Nov 26 '14 at 9:56
  • I don't understand the part about nested dimensions containing each other. – JDługosz Jan 28 '15 at 6:55
  • @Twelfth, amazing answer, but how would one do that? The bombarding the dimensions with energy? What does that mean? I know you said "very futuristic technologies", but... – Len Feb 14 at 15:25

Building on the fact that your edit now includes my suggestion for superconductors I'm going to write an answer arguing why I think it's the most plausible solution.

Superconductors

Superconductors actually work right now with maglev trains. These however have superconductors whose magnetic fields interact with metal conductors to cause them to levitate enough to reduce friction.

Comparatively the Earth's magnetic field is very small to that which is produced by these conductors so you need really strong superconductors.

There are a few issues with this:

  • They need to either be made of some unknown material which works at normal temperatures (as opposed to below 70 K or -203°C)
  • They need to be small and light enough to carry around in the ship
  • They need to not consume more energy that normal propulsion

However despite these issues I still believe superconductors are more promising than the other options, comparatively:

  • Gravity shields are hypothetical
  • Gyroscopes seems wildly difficult to achieve
  • Warp drives may not be possible
  • Exotic matter may not exist

All you have to do is invent a special superconductor for your world that meets the requirements you need.

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    Gyroscopes flat out don't work. Magnetic levitation is an interesting idea, it's not really anti-gravity but it achieves the same aims. Unfortunately the Earth's magnetic field is not very conducive to the idea though :( physics.stackexchange.com/questions/14044/… – Tim B Nov 19 '14 at 13:27
  • @TimB Can't remember the math but something like a 1 mi^2 ship with a flat, paper-weight superconductor could have enough gradient to support a 65 kg person... Don't quote me on it though. – Black Nov 23 '14 at 9:38
  • It's not the actual strength of the Earth's magnetic field that's relevant to magnetic levitation, but rather how the direction of the field changes over space, and the field is so large that the change is tiny. See this page for more info. – Hypnosifl Mar 10 '16 at 5:12
  • What are gravity shields? Just curious... – Len Feb 14 at 15:34

Which of these techniques (or any other) is most feasible to allow large ships to float into, out of and fly around within a planet's atmosphere?

Um...

enter image description here

  • Wow there, although this isn't hard science, you at least to need to propose something plausible. – PyRulez Nov 12 at 2:18

If what you need is to reach the orbit, a nice solution could be a space elevator.
You will have to invent some super strong material that would prevent the cable to be broken by the enormous forces involved, but it's a likely solution.

What is a space elevator?

Basically you put a very massive object on a specific point orbiting around the world.
That object will be in "equilibrium": it won't fall down or go away in the space.

Your ship will only be lifted to a specific point (using normal rockets), then it will be uplifted without any energy need due the Apparent gravitational field

If placed in the deep space, the counterweight will generate enough power to lift your ship to Jupiter. Once in space the ship can be maneuvered using conventional boosters.

It's not a very sci-fi solution (ie push a button and everything is magically working), but it has solid scientific basic and it's technologically feasible.

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    That's not how a space elevator works? The ship won't need to be supported by a strong material, it will be to be 'held down' by a strong material because if the elevator is tall enough the ship will be pulling outward away from the earth. This idea also doesn't allow the ship to move, I don't think the problem is reaching orbit as much as being very efficient in moving around. – sydan Nov 19 '14 at 11:55
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    you need a good material since the snapping of a wire long several Km will be "unhappy". The OP asked about reaching the orbit, not going around the atmosphere. – tampe125 Nov 19 '14 at 12:21
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    I don't know why you are mentioning rockets or apparent gravity. With space elevators you just climb up the cable (once the elevator is built) using an...elevator... It's a very cheap way to reach orbit although unfortunately we do not (yet) have the materials science to build one. – Tim B Nov 19 '14 at 13:28
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    It's also not anti-gravity... – Tim B Nov 19 '14 at 13:29
  • @tampe125 thanks for your answer - in this case I'm after flying or floating rather than an elevator - I'll edit the question to make it a little clearer – Liath Nov 19 '14 at 15:54

I'd comment on superconductors, but not allowed.

This only works for Earth - and things with magnetic fields. You'd crash right into Mars, Venus,or the Moon.

You could substantially turn down (hopefully) your supermagnets, when you want to skim Jupiter for H3


What about anti-gravity waves or use of gravitons?

Here's an example: http://www.startrekfreedom.com/wiki/index.php/Antigravity_Systems

  • Gravitons wouldn't work (they hypothetically mediate gravity), but I suppose something from sci-fi could be adopted. – HDE 226868 Nov 19 '14 at 22:01
  • Why wouldn't gravitons work? "I'm not after hard science" == looking for an excuse for a scifi book / setting (RPG?) – user3082 Nov 20 '14 at 1:01
  • They cause gravity. – HDE 226868 Nov 20 '14 at 3:33
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    Umm, and you point them the other direction, causing gravity opposing the gravity you're being dragged down with? – user3082 Nov 20 '14 at 7:15
  • Why not just use other particles? It's like saying that you'll use copper as an insulator, despite the fact that its properties make it an excellent conductor. – HDE 226868 Nov 20 '14 at 15:56

While it is not strictly "antigravity" in that it does not reduce the effects of gravity, the EmDrive is an apparently plausible reactionless thruster that relies solely upon electrical input.

Should this device be increased in size and efficiency, ganged up with computer control to compensate for external forces such as wind and turbulence, and provided with a sufficiently large power source (quite possibly atomic), there is no reason why it could not be used to counter the acceleration of gravity, thus providing a craft of thousands of tons mass with the appearance of floating.

  • Read the intro to the wikipedia link you posted. The original results were not reproducible and it seems that as of now they are chalked up to errors in precision. – ben Nov 11 at 0:20

Magic

Oh, wait, no

The Ether

Well, something like it, anyway. As it turns out, space is not really empty. Maybe mostly empty, but not really. Also, we have a strong tendency to think that the Sun is just sitting there, but as it turns out the Solar System is hurtling through space.

If you couple the two of these ideas together, perhaps there's a way to reach out and "grab" something that is relatively stationary, or use something with an incredibly low density to rise waaaaaaaaay up.

It'd be kind of magic, though.

The only one of those options that really works is "exotic matter". All the other options are going to require enormous amounts of energy to work, making them roughly as useful as picking up your ship with helicopters.

  • Gravity shields
    These would require some kind of gravity-blocking substance be found, which would cause those shields to be much heavier than normal. If such a thing were possible, it could be used to at least lower the amount of gravity passing through, and thereby reduce the thrust required. But to block all the gravity, your shield would have to weigh a substantial fraction of all the earth beneath it. (It would be the percentage of solid angle the shield covers.)
  • Gyroscopes
    I have no idea how a gyroscope would keep you in the air. Conservation of momentum says anything the gyroscope does to move you up has to be accompanied by a similar pull down.

    If you could get the gyroscope to produce a net force, it would come at the expense of rotational momentum, requiring you to expend more energy to keep the momentum up. For example, a spinning disc could create an electric field that might push against another field and keep you up, but it's ultimately just thrust.

  • Warp drives
    Warp drives, if they work at all, will be ridiculously expensive. The only reason to bother with them is to break the speed of light over vast distances. Keeping a warp field open to hover over the planet would likely use up the mass energy of the entire planet pretty quickly.

    And all that energy has to go somewhere. You'd melt the planet you were hovering over even if there weren't more pressing relativistic problems.

  • Superconductors
    These have the same basic problem as gyroscopes. You're just using electricity to create thrust in a nonconventional way. It's not really anti-gravity.

  • Exotic matter
    If it exists, certain exotic matter could "cancel out" the normal matter's mass. You have to find a way to bind the matter to normal matter, but you'd essentially have a floating device. Bear in mind that you have to get the device to the planet, which means raising it's gravitational potential energy (in this case, the closer it is to a massive object, the more potential energy it has).

    That work done will require energy, so it might not be particularly useful in the long run. Still, the advantage here is that you only have to move it once. After it's down here, you can float with it for thousands of years, which is more energy efficient than constant thrust.

  • Permanent magnets
    There are plenty of kids toys that use permanent magnets to levitate an object indefinitely. You'd be restricted to a specific location, possibly a specific path, and Earnshaw's theorem suggests it wouldn't be totally stable, but you'd use a lot less energy maintaining position than hovering.

    If you wanted to hover in one place, maintaining position would be as simple as attaching a few cables to the ground to counteract any sideways forces. For a track of some kind, you could have cables that run along the track beneath you to hold you in place.

    I've never seen the track idea done. Maybe I'm missing something. But it seems like you could have two magnets side-by-side at some distance, both pointing their north face upwards. Then your airship would have its north face downwards. Now, the airship will tend to fall to a spot between the two magnets, rather than climbing over the magnetic field's "hump" to fall outside the magnets.

    Then, by having a series of these ground magnets, you'd have a line the airship can follow. If you stop moving, you'll tend to settle into the valley between four magnets and hover. However, the south side of your magnet will want to flip you upside down and accelerate to the north magnetic fields. So you need some way to prevent that, such as cables or thrusters. I'm not sure how doable that is.

Exotic matter. If exists, exotic matter has negative mass, which means that gravity actually repels it instead of atracting it, therefore a, let's say, ball made of exotic mass would float insted of fall.

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