# A way to hinder interstellar portalling? FTL travel

So I'm working on a story that at its groundwork has a lot of sciency things, and then has a lot of unsciency things attached to it. The story has an FTL drive which is the good old "fold space, puncture space, travel through" methodology. As a restriction, folding more space (i.e. traveling farther) requires more energy, and smaller folds are more efficient as you fold less "extra" space. For example: If you travel 1 km, you fold 1 km of space in all directions. If you travel 10 km, you fold 10 km and thus a far greater volume.

But now I want to create an interdiction method. My current idea was to use mass and its gravity. Any mass bends space around it, and something like a planet bends much more space, which is how light can change its trajectory by a mass without actually having a mass to be attracted to the planet's mass. By causing tons of these bends in space in quick succession you could create ripples in space that go outward at the speed of light (at least I think that's the case). My idea was that these ripples would disrupt the accuracy of someone trying to bend space and trying to portal somewhere, as long as the ripple is going through the space they are bending. My question is, would that assumption be correct? Or does the space-bending properties of a mass not reach very far?

For those who realize what I'm asking, yes we are ignoring the fact that you are now creating tons of very temporary artificial gravity wells that would probably have to range between a planet's mass and a black hole to have any noticeable effect and would undoubtedly destroy your ship when you create so many nearby.

• What is the effect of folding space (a) at the launch point, (b) over the span of the "fold" and (c) at the destination ? In particular what relative dimensions do these effects happen over and what happens things already between source and destination when space is folded ? Commented Mar 24, 2018 at 1:49
• At 10km your not folding 10km, your folding the volume of a sphere 10km in diameter. This is the basis of the inverse square law, which applies to gravity, light and many other things.... The range of gravity is infinite, but it's strength is reduced by the inverse square law as the volume grows. Commented Mar 24, 2018 at 4:18
• to range between a planet's mass and a black hole These are not mutually exclusive things, you can have a black hole the mass of a planet(in theory), and you can have a planet with any mass below that required for fusion. and you can have a Black hole the mass of several thousands of stars. A.K.A just a undefined amount of mass. Commented Mar 24, 2018 at 4:33
• @StephenG Nothing happens with anything inbetween the fold. The ship itself is also in the fold so it would be rather problematic if it had any annoying effects. Commented Mar 24, 2018 at 9:20
• @ArtisticPhoenix if you want to travel 10Km in a straight line, you would indeed need to fold a 10Km sphere, that's why I talk about volume when talking about folding space. And that square law for it's range is part of what I was looking for, tnx. As for the range of masses, on average a black hole will have a larger mass than a planet, so I used the assumption of that average. Commented Mar 24, 2018 at 9:20

When ships have the technology to fold space at will, then you can do the same thing. So when you detect a ship folding space, you just counter their fold using your own space-folders.

If you want to be nice, you just fold the space back to normal, so it simply doesn't work. If you want to be mean, crumple the space the ship wants to travel through. Instead of one neat fold, create a whole bunch of differently aligned folds in their route. Now when they puncture the folded space, different parts of the ship will travel different distances in different times, ripping the ship apart.

• I really like many of the implications, but is there any reason why any ship would be able to detect someone else folding space? A better question might be: If this is truly possible, wouldn't it be impossible to have multiple ships jump in close proximity to eachother? If another ship happens to be jumping from the other system towards yours while you are preparing a fold for your jump, then you are both folding eachothers space accidentally and now the first one is in big trouble. Seems a bit too dangerous to allow as it would invalidate unregulated space travel. Commented Mar 27, 2018 at 7:03

Last year humankind witnessed a merger of two black holes. We were able to do so because the merger gave out gravitational waves:

The detected gravitational waves — ripples in space and time — were emitted during the final moments of the merger of two black holes with masses about 31 and 25 times the mass of the sun and located about 1.8 billion light years away. The newly produced spinning black hole has about 53 times the mass of our sun, which means that about three solar masses were converted into gravitational-wave energy during the coalescence.

I imagine such waves could make any space travel rather... Turbulent, even more so if the ship is using an Alcubierre drive or anything similar.

So yeah, not only it is possible, it happens every once in a while in our universe.

The issue I see here is targeting. You have to know with fairly high precision where these enemy "folds" in space are going to be, and then arrange to have your own "folding" mechanisms get there and begin creating disturbances.

Of course, since you are observing in inertial space, you won't "see" an FTL effect until it gets there, so you cannot either:

a. preemptively move your system to the enemy origin point, or:

b. activate your system before they arrive.

Given these constraints, the only way I can see for your mechanism to work as described is to use it as a static defence mechanism. You park the device in orbit and set it running to create ripples in space-time, negating the ability of an enemy system to enter "nearby". I would suspect that the rippling spreads outward at the speed of light, so initially the volume of protected space is rather small. I also would imagine that the inverse square law applies, so there will be a distance where the gravity waves are so attenuated they no longer affect the FTL "folding".

This of course ignores the effects on the protected planet, asteroid etc. of a "rippling" gravity well the size of Jupiter in action nearby.

• I'm not sure why targeting would be a problem. Think of it like a pond: It's smooth until the ship starts generating it's gravitational waves to distort space. It creates several ripples every second of varying size and in different locations around the ship, possibly for days on end. This mess of waves will ripple outwards at the speed of light in all directions and hopefully come into contact with a ship that's trying to travel through the distorted space, throwing off their accuracy. So the interdiction method itself wouldn't, as far as I can tell, require accuracy. Or a lot of timing. Commented Mar 24, 2018 at 9:26
• Except the ripples travel at the speed of light while the description of superluminal transit has the ripples being the effect of the movement of the ship, it arrives before the ripples of distorted spacetime. Commented Mar 25, 2018 at 2:36
• Whether the ship arrives before or after depends on it's direction doesnt it? If the ship doesn't pass close to the interdicting ship before those ripples arrive at his traveling points, the ripples won't do anything. This allows interdiction methods where ships have to jump in relatively far away from planets in case someone is interdicting, which would send them way off course if it is happening. To prevent jumping into a planet (interesting to think of what would happen then) they would jump in far and then travel normally or in small bursts to maintain accuracy more. Commented Mar 27, 2018 at 6:59

Here is a thought I had.

Say spacetime is elastic, the ease at which it can be stretched manipulated, folded etc. Is directly related to the amount of mass in the path of the jump.

Jumping would be a cylinder not a sphere, a sphere would work for the interdiction device but to use that for jumping is a huge waste of energy. This in turn makes interdiction harder. Because the more energy poured into a jump, then it would seem logical that interdiction of that jump would need even more energy.

Back to the effect of the elastic property of space time. If that was so then jumps along certain paths would be much easier then jumps along others. Jumps to one star system from another would have to follow a sort of fuzzy lane. Because if there was another star system between the start and end points it would make jumping directly much harder.

It would also prevent jumping into a system from a random direction. For example you wouldn't be able to jump to the far side of a system, because the mass of the system would make space less elastic.

It wouldn't make these things impossible. One could jump to the middle star system, then jump to the target system after travailing in normal space around or through it. But it does add time and a chance to place beacons that may detect an enemy fleet in advance.

In the second case you could take a route that allows you to jump just outside the system from a different direction. But it would be a much longer route and require many more jumps.

This may be enough to take care of the "you have to know where to put the interdiction device at" problem. It also plays to how the interdiction device works.

How deep into a system can also be rationalized for jumps, it may be ok to jump in to the orbit of Jupiter (if the planet is on the other side of the sun) but not the orbit of mars because the deeper into the gravity well of the sun you go the more stiff space time becomes.

Hope that idea makes sense... lol

• I like the idea of allowing gravitywells to make space harder to fold. I'm not sure what you mean with the "you have to know where the interdiction device needs to be". Why would that be important? If the interdiction device has strong enough ripples cross the other ships spacefold he would already succeed right? If the other ship is too far, he can still jump assuming his trajectory doesn't cross too close to the ripples. Sounds like a good system to me, unless there's a big problem with it? Commented Mar 27, 2018 at 6:54
• What I mean is you have to know where he is jumping to, if he jumps in on the other side of the solar system, your interdiction device needs to be more powerful. So by limiting the ability to jump through a system, if you know the direction an enemy is coming from you can better place the device. Commented Mar 27, 2018 at 16:37
• I reality this is all hand waving, but it's a matter of the magnitude of the power the interdiction device needs. You could say I can interdict any jumps in the galaxy if you had a powerful device, or you could say it's 1ly in volume what it comes down to is which is more believable. Commented Mar 27, 2018 at 16:39
• As I said in the main comments, if the geometry of the jump and interdiction is the same, then it would stand to reason that the power use is the same. But if the jump is cylinder then it requires much less power. Ships would tend to have less power then a static station rooted in a solar system. Commented Mar 27, 2018 at 16:41
• Another example is say you can only jump to Jupiter's orbit. if a jump drive is spherical, you would need to be half way to your destination to use it. Because would not Jupiter's orbit be inside your jump sphere. And if it can prevent jumps further in there should be nothing special on one side of the sphere vs the other. And thus it would prevent jumps away as well. This is why I think a jump needs a different geometry that has a start and end point. Commented Mar 27, 2018 at 16:45