I'm creating a fictional hyperspace to enable FTL travel. It's sort of a mix of Star Wars, Star Trek, Halo, and probably a bunch of other stuff. I've run into an aspect of it that either requires some handwaving or a bit of math that's beyond my understanding. It goes something like this, please bear with me:
Hyperspace is perpendicular to our normal spacetime. As you go "deeper" into hyperspace, coordinates get compressed. Imagine our spacetime represented as a square plane and hyperspace as an inverted pyramid below it (or a disc and a cone, if you like). Since all points eventually converge at the "bottom", if you can go down into hyperspace and travel a bit, when you come back out you will have moved father than normal and faster than light (effectively). This compression occurs in smooth gradients, not distinct layers like subspace in Star Trek.
Like Star Trek though, you need a field that creates a bubble around your ship. This makes an area of normal spacetime that protects your ship. Then you can push into hyperspace with this bubble and manipulate the shape of the bubble to move around in hyperspace. Hyperspace wants to push you out (or keep you out), and gravity wells magnify this effect. So you need enough energy to stay in and you need to plot a course that avoids gravity wells.
I'm not asking about the energy requirements though, because I have a fictional power generator that we don't worry too much about.
Since you naturally pop out of hyperspace near gravity wells (or even if your drive fails), the main dangers with this drive system, in my mind, seem to be regarding the field that makes the bubble. Anything contained within the bubble goes into hyperspace, which allows for stuff getting cut in pieces, like what happens in Halo 2 when the Covenant ship jumps while it's still over the city (It brings chunks of buildings with it into deep space).
The field that makes this bubble in my fictional universe can vary in strength from nothing (off) to a level that allows for the transition to hyperspace, then beyond, until you don't have enough energy to go any deeper into hyperspace. I think that these bubbles repel each other (kind of like magnets), such that two ships in hyperspace would not collide. I also think there must be a gradient of some kind between normal spacetime and hyperspace, however slim, at the edge of the bubble.
Given all that, my questions are:
- What might happen to matter at the inside and outside surfaces of the bubble at the moment of transition?
- Could there be dangerous effects even before the transition to hyperspace, as the field strength is increasing?
- What might happen to propellant expelled/ignited if the ship fired its conventional engines while inside the bubble (or any other matter contacting the bubble, really)?
- Might there be any dangerous radiation inside or outside the bubble, especially due to any matter caught in the transition?
- Does it make sense that the bubbles would repel each other (does it seem internally consistent)?
- What visual effects might there be to an outside and/or inside observer (especially during transition)?
- Any other potential dangers from creating or collapsing this bubble?
Bonus/Epic Fail: Are these questions even answerable with my description of hyperspace?
Edit to attempt to make things less broad:
Based on a4android's answer I'll refine the definition of the bubble by saying that it is impermeable in both directions (hopefully lending credibility to the idea that bubbles repel each other). Also that you can't see out of it, probably for the same reason.
So really the main concern is: what happens to matter when it's sheared at the edge of the bubble as the ship enters hyperspace? (For example, might it become superheated, converted to energy, etc.) Are there any known rules of physics that might inform my description of the effect, or do I just make up whatever seems fun?
I know this isn't hard SF by a long shot, but I like it when the answers at least seem to be based on what we know about physics. I also know that's a bunch of questions rolled into one long post, so I appreciate any help you can give.