Space combat hangups

[Josh_Kablack]

Imma gonna look at some ways that FTL might be setup within a game or other work of fiction, with some brief overviews of what else happens for each starting assumption:

So if you postulate

I. Relativity missed something, FTL Travel is totally possible

You get ships that travel faster than the speed of light.

You get projectiles that also travel faster than the speed of light

You presumably get very big explosions when something moving faster than the speed of light hits a sufficiently large and solid object, and such missiles or mass drivers are a major component of spacewars.

You have to postulate some ramifications for ships moving faster than any known sensors. Some options here include having FTL sensory mechanisms, having cleared spacelanes, having precognitive pilots, having AI that make probabilistic calculations that approach precognition, having FTL ships hardened against the inevitable collosions, or having even more faster than light scoutdrones run ahead of the main ship. Your answer to this leads to what stealth and detection and ambush tactics look like in warfare.

II. You can cheat relativity and get there faster than light by taking a shortcut through another universe

You then have to postulate a bunch of details about Hyperspace, Subspace, The Warp, Psispace or whatever you want to call it.

You also have to postulate details about entering and exiting it, and these details should probably include some reasoning why everyone doesn't use it all the time and with people just opening a hyperspace shortcut down to the qwicky mart for milk and a turbo dog thankyoucomeagain.

Various works of sci fi have postulated that such might require computationally difficult astrogation; cannot be done in significant gravity field;, requires large engines; requires nekkid psychic chicks hooked into your ship; imposes great physical stress on living organisms, involves fighting indescribable horrors that dwell in that dimension; or can only be done in places where the fabric of space has particular properties - but that brings me to the next option:


III. You can cheat relativity only via specific connection points

Then warfare will be all about finding or building these Stargates/Worm Holes/ Warp Gates and about capturing and holding those already known or established.

If the connection points are universal constants, then finding and holding them is key.

If the connection points can be built, then you get sublight generation ships expanding empires at a crawl over centuries while those within the area covered by established connections can be traversed in a timeframe approxaimating 21st century inter-city air travel.


IV. You can cheat relativity by collapsing parts of this universe into a semi-stable demiplane

This is the technobabble Star Trek went with - their Warp drives warped nearby space into a bubble, which moved through regular space as the ship moved through the bubble. It's also begs for people to build recursive bubble-within-bubble-within-bubble propulsion. You might want to put some limits on that and what else this is used for - Can you use these bubbles as weapons or shields? Can projectiles use these to hit things at greater than lightspeed? If not, do things in warp bubbles pass through/under/around objects in nearby places in normal space?

But if you're going for this sort of wild sorcery answer then, there are two final options


V. Relativity Holds true, FTL is impossible, but this whole thing is a what-if-simulation

You're all inside a computer game/VR/military simulation/dream/psychic exercise designed to predict what might happen if some other type of FTL could work. The simulation itself is limited to giving data at the speed of the electrons in the computer, but it can rewrite your location from Sol-3 to Deneb-7 by updating the flash memory of it's database - so you lose a lot of granularity and scenery of the vast reaches.

You can use this to turn any of the above into something that is actually scientifically plausible, at the expense of turning the whole game into a potentially recursive Cartesian demon scenario.

VI. This is Comedy

If your goal stops being semi-plausible science or exploration of ramifications of implausible science and shifts to making the audience laugh, then you open up some really out-there stuff like Improbability Drives, Ludicrous Speed turning your ship plaid or turning the nekkid psychic chicks into outright dirty jokes.

In this setup, warfare is potentially about being able to throw a custard cream pie at FTL velocity.

[Chamomile]

Raspberry! Only one man would dare use raspberry on me!

[kzt]

Plus the option of something off the wall but serious. For example, I have always liked "Five-Twelfths of Heaven", but you sure are not playing a standard SF game with the drive system they used.

[hyzmarca]

Imma gonna look at some ways that FTL might be setup within a game or other work of fiction, with some brief overviews of what else happens for each starting assumption:

So if you postulate

I. Relativity missed something, FTL Travel is totally possible

[...]

II. You can cheat relativity and get there faster than light by taking a shortcut through another universe

[...]


III. You can cheat relativity only via specific connection points

[...]

IV. You can cheat relativity by collapsing parts of this universe into a semi-stable demiplane

Also remember that any method of cheating relativity also permits convoluted and limited, yet dangerously practical, time travel. This is because of how velocity relates to time dilation. Essentially, any method to break light speed in a relativistic universe lets you send information into the past and break causality.

The only way to defeat this is to postulate an absolute reference frame. But even then you should be able to fake time travel to a degree.

[Grek]

The only way to defeat this is to postulate an absolute reference frame. But even then you should be able to fake time travel to a degree.

This can be avoided (for all practical purposes, anyways) if you use wormholes or wormhole-like objects with the following properties:

A. Neither end of the wormhole can be within the light cone of the other end.
B. Both ends of the wormhole (and presumably the thing you're using the wormhole to access) are moving apart from eachother at a speed greater that C due to the expansion of the universe.
C. There is a 1 to 1 linear mapping between instants of time for the frames that the two ends of the wormhole connects.

Together, these make it so that you are unable contact anyone with FTL communication/travel than you could contact with STL communication/travel (and thus avoid any potential for time paradoxes) while still allowing you to visit as many planetary systems as you want.

[hyzmarca]

The only way to defeat this is to postulate an absolute reference frame. But even then you should be able to fake time travel to a degree.

This can be avoided (for all practical purposes, anyways) if you use wormholes or wormhole-like objects with the following properties:

A. Neither end of the wormhole can be within the light cone of the other end.
B. Both ends of the wormhole (and presumably the thing you're using the wormhole to access) are moving apart from eachother at a speed greater that C due to the expansion of the universe.
C. There is a 1 to 1 linear mapping between instants of time for the frames that the two ends of the wormhole connects.

Together, these make it so that you are unable contact anyone with FTL communication/travel than you could contact with STL communication/travel (and thus avoid any potential for time paradoxes) while still allowing you to visit as many planetary systems as you want.

B is impossible, though. Nothing can move at a speed greater than C. And if you've got FTL expanding wormholes you can probably use whatever phenomena lets them move that fast to make FTL engines of your own.

You can make it extremely impractical to have time travel in a wormhole system, but not impossible.

[Quantumboost]

B is impossible, though. Nothing can move at a speed greater than C. And if you've got FTL expanding wormholes you can probably use whatever phenomena lets them move that fast to make FTL engines of your own.

You can make it extremely impractical to have time travel in a wormhole system, but not impossible.

Not quite true. If space between the two points is expanding faster than the light can traverse it, the points can be moving away from each other faster than lightspeed. Special relativity is overridden in that case by general relativity, since the assumption of flat spacetime is grossly violated.

It's postulated in scientific circles that this sort of space hyperinflation could eventually go into a self-reinforcing runaway explosion and overcome even the strong nuclear force. We'll almost certainly all be dead from too much entropy by that time, of course.

[Vebyast]

It's postulated in scientific circles that this sort of space hyperinflation could eventually go into a self-reinforcing runaway explosion and overcome even the strong nuclear force. We'll almost certainly all be dead from too much entropy by that time, of course.

Yep. For more information on this possibility, read up on the Big Rip. Basically, there's a value for the ratio of dark energy (weird stuff that repels other stuff) to its density w. If w < 1, then the universe will collapse back onto itself in sort of a big bang in reverse. If w = 1, the universe will eventually reach an asymptote and last forever (well, except for thermodynamics). If w > 1, the universe's expansion will accelerate until adjacent subatomic particles are moving away from each other faster than the speed of light and the universe basically disintegrates.

Fun fact of the day: we've spent twenty or thirty years trying to measure w, and so far every single test we've done has been inconclusive. Our measurements are so close to 1 that we can't tell between 1, <1, and >1.

[fectin]

We already had the time travel discussion in one of Frank's Heartbreaker threads. Someone brought in ringers, and it turned out there was a way to make everything work, without time travel being possible.

[schpeelah]

B is impossible, though. Nothing can move at a speed greater than C. And if you've got FTL expanding wormholes you can probably use whatever phenomena lets them move that fast to make FTL engines of your own.

You can make it extremely impractical to have time travel in a wormhole system, but not impossible.

Not quite true. If space between the two points is expanding faster than the light can traverse it, the points can be moving away from each other faster than lightspeed. Special relativity is overridden in that case by general relativity, since the assumption of flat spacetime is grossly violated.

Except that requires that both edges of the wormhole be outside each other's observable universe. Literally the edge of the observable universe is defined as "so far away the speed of space expansion approaches c". For any practical purposes, those wormholes might just as well put you in another universe entirely. I don't think that's what we were going for.

[Grek]

For any practical purposes, those wormholes might just as well put you in another universe entirely.

Not quite! Consider the following example:

1. You start out in the Alice System.
2. You have a pair of wormholes (named AL and LA) which connects the Alice System to the Larry system.
3. You use AL to transport yourself from Alice to Larry at FTL speeds
4. You then go to a short distance the Larry System and enter the LA wormhole, bringing you back to the Alice System
5. You have now displaced yourself a significant distance across the Alice System while spending a short amount of subjective time in transit across Larry.
6. From the viewpoint of the people in the Alice System, you entered the Alice end of the AL wormhole and disappeared. Some time later (as long or longer than it would have taken you to travel the distance with STL methods) you appeared at the Alice end of the LA wormhole.
7. Causuality is preserved without your crew having to survive the countless years it would take to fly from AL in Alice to LA in Alice!