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In a game scenario I am developing, one option for a fleet to infiltrate an enemy is to use ftl to "hard burn" through a black hole's event horizon. Their ftl drives use a "warp bubble" principle to function. So, my questions are:

  1. Would the singularity's time dilation still affect the fleet as it burnt through? What would the effect be?

  2. Would the warp buble, in principle, provide insulation/protection from this?

  3. What other ways would the ships/crew be affected?

*I should specify that they are moving through the outer edge of the EH, where it can trap light but their FTL engines allow them to "maybe" slide through.

**This is a theoretical, "seat-of-the-pants" maneuver in a science-FICTION universe using science-FICTION space travel and technology. The protagonists CAN attempt this maneuver with the possibility of success. I am only asking the above questions. IOW, what complications/effects could the crew face after successfully performing the maneuver? They are trying to save their world from a powerful enemy. Do they emerge to find the war over? Or progressed further than they expected? Etc.

***Though I am looking for more general effects, the drives they are using have a 5c acceleration capacity and the singularity they are trying to cross is approximately 100k miles in diameter (350-400 Sol mass), if you want to do calculations.

****For those interested/wanting to know for calculations: there are two ftl drive types available to humans in the setting. The first, "slip drive" is mostly used by the AI piloted mother/colony ship. It only consumes energy when entering/exiting FTL "sub-space" and travels at 1.5 c in subspace, and can (but generally doesn't for resource conservation) use its maneuvering/sub-light engines for added acceleration. The second drive type, "warp drives", are used for close interstellar travel. They envelop the ship in a warp bubble that allows the ship to accelerate at a pace of 5 c/second with virtually no upper limit. However, the ship burns fuel/energy at an extreme rate while warping in order to maintain the bubble and must decelerate to sub-light speeds before the bubble collapses (not doing so would result in any number of disastrous effects, all of which include the destruction of the ship/crew).

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    $\begingroup$ The event horizon is the place where the direction towards the black hole becomes timelike. Inside the event horizon the future points towards the black hole, and the exterior universe lies in the past. Unless the FTL drive doubles as a time machine, there is no way to escape... (And the event horizon is not at all special locally -- unless you take careful measurements and make the required computations you won't notice anything special when crossing it.) $\endgroup$
    – AlexP
    Commented Sep 5, 2019 at 7:35
  • $\begingroup$ But would the ships crossing it emerge into a galaxy that had experienced the same passage of time, more, or less? My understanding of the EH is that it is the point where the singularity's gravity exceeds the speed of light (thus it is assumed one cannot escape) however, the actual singularity is still quite a ways within the border of the EH, meaning it's influence is still weaker at the edge of the EH than at its actual surface. This would leave a theoretical "corridor" where a ship capable of constant ftl acceleration could potentially pass through. $\endgroup$
    – HA Harvey
    Commented Sep 5, 2019 at 7:42
  • $\begingroup$ Also, the question is both labelled as "science-fiction" and NOT labelled as asking for "hard science". The whole point of sci-fi is "what if?" so, What if such a nutty path (using imaginary tech that also doesn't currently and maybe can never exist) COULD be traversed? What effects would make sense in the story? $\endgroup$
    – HA Harvey
    Commented Sep 5, 2019 at 7:48
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    $\begingroup$ Given that you have a FTL drive, it makes sense to have a customized EH for the FTL drive itself. Given that the EH is when light can't escape, surely there will be a point where even if you are FTL, you won't be able to escape. $\endgroup$
    – Shadowzee
    Commented Sep 5, 2019 at 7:56
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    $\begingroup$ There are a few details that need clarifying. What is the size of the black hole? How fast is the FTL drive? For example, a 3 c FTL drive can pass through a BH between the 1 c EH and the 3 c EH. The faster the drive the deeper its passage. $\endgroup$
    – a4android
    Commented Sep 5, 2019 at 8:20

2 Answers 2

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Any answer will depend on the size of the black hole (BH) and the speed of the faster-than-light (FTL) drive. Let's start with an extreme example: a galactic mass BH and a 1,000 c FTL drive. The diameter of the BH is four light hours.

The fleet of FTL vessels can travel through the BH in a wide variety of angles and directions as long as they don't go below the 1,000 c EH.

Assuming the fleet travels along a path of length two light hours or 7,200 light seconds, its travel time through the BH will be only 7.2 seconds. If time dilation applies, assuming the warp bubble doesn't change relativistic time inside it, then a time dilated traverse will be much, much less than the 7.2 seconds.

Personnel on the fleet vessels won't notice they have travelled through the BH. Not visually anyway. Their instruments will indicate their passage based on their position, location and distances travelled.

The fleet will emerge seconds after their trip through the BH. The war won't be over. However, if the fleet puts itself into orbit around the central mass of the BH, with a FTL orbital velocity it can remain there for a reasonably long period of life. If they choose to, the fleet can stay there until the war is over. Once they decide to leave, the fleet can increase its FTL velocity and attain escape velocity from the BH.

It is conceptually possible to manipulate the sizes of the BH and the speed of the FTL drive to achieve whatever objective you want for your game scenario. Basically time dilation won't much impact on a FTL trip through a black hole. But, things are different, if the fleet places itself in an FTL orbit inside the black hole.

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  • $\begingroup$ thanks! That helps a lot. The drives use a warp bubble to enter ftl, and then can propel themselves at extreme speeds normally (thus, the 1000 c speed wouldn't be that outlandish). However, as I was thinking that their ftl bubble would only make the trip possible . . . not easy, I was thinking that only the engines' ability to accelerate would let them move contrary to the BH's pull. As for lurking, the fast drives couldn't do that, because maintaining their "bubble" burns fuel very quickly, where the slower drive could do that, but would have to crawl out of the EH. $\endgroup$
    – HA Harvey
    Commented Sep 5, 2019 at 8:54
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    $\begingroup$ There's a scene in "The Orville" where the heroes do just this. Be warned, the episode in question does have 3 or 4 episodes to watch to fully understand the story, but the trick is cool enough without the required watching. It will be Season 2 finale. $\endgroup$
    – hszmv
    Commented Sep 5, 2019 at 12:21
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As long as you have warp bubbles allowing you to go through event horizon, you can plausibly have them protect you from all possible time dilatation effects (if they don't, you are opening quite a can of worms: you might even end up time travelling to the past when moving faster than light).

If the technology does not protect you, you will (seen by an outside observer) get stuck on the event horizon, as an instant there corresponds to infinity in outer space. Definitely not coming out in time for battle.

TlDr: make your warp technology eliminate time dilatation.

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  • $\begingroup$ That is a reasonable solution. I was thinking that (to avoid the relativity issue every time ships jump between systems) the warp bubble should at least partially insulate against time by "warping" time-space around the ship. Especially with the other answer, the dilation wouldn't have a drastic effect anyway, so it's best to not worry about it and bog down the story unnecessarily. $\endgroup$
    – HA Harvey
    Commented Sep 5, 2019 at 9:00
  • $\begingroup$ As for a reason why the bubble only insulates the ship/crew, that's easy enough. Creating a bubble that completely isolates the ship from normal space-time would be problematic because there would be no way to return to the ship's own time/relative space after travel/possibly even dimension. So, the ship has to "keep a foot in the door" so to speak. $\endgroup$
    – HA Harvey
    Commented Sep 5, 2019 at 9:35

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