The case for Autointerdiction.

[Drashner1]

Todd: There doesn't have to be a rational reason to go to war. In fact, there almost never is, at least for the aggressor. (Going to war when someone has already gone to war with you is not only rational, but vital for national survival.)

I'm not seeing how this statement is relevant to my points above. Are you responding to something specific (in which case, please point out which one it is) or making a general statement?

Regardless, the same statement can apply to any war, anywhere. As I've already pointed out, a civ limited to just this planet can have any number of methods of killing itself - some of them vastly simpler and harder to defend against than an attack from another solar system - so why is the potential for an eventual attack any different or more of an issue? Biotech or AI research or nanotech could eventually create the means to destroy humanity. Should we therefore ban all research into these fields because there is a potential risk regardless of any and all potential benefits? If we're going to go down that road, then shouldn't we ban all further tech development because we can't predict what could come out of it that could destroy us? Note that even apparently 'safe' tech can fall under this umbrella - various chemicals and the internal combustion engine were long thought to have no global scale downsides - hellooo climate change and contaminated water and such.

Of course, if we give up tech then we put ourselves at the mercy of the universe (which has none) and that can eventually destroy us just as certainly, if not more so. So Catch - 22.

Taking this to an interstellar civilisation: Without any fom of FTL, to make any sort of coherent interstellar society work requires relativistic speeds and the associated gigantic energies.

Actually most people would argue that any kind of coherent interstellar society in the mode of an Earth based nation or empire is impossible in a slower than light limited universe. OA gets around this by a combination of memetics (propaganda and marketing on steroids) and presuming that civs in the setting are much more loosely organized than any planet based civilization.

Also, if sheer speed is your main criterion than radio or optical data links are the way to go over starships for keeping your intersetllar culture at least somewhat linked together and cohesive.

It also seems unlikely that high relativistic speeds would make much of a difference. A 20ly trip will take 20 years for the start and end points no matter how close to light speed a ship can make the journey. And, barring a major tech advance, relativistic speeds of a level sufficient to produce any kind of significant time dilation are not going to be the first thing achieved, so early ships will go considerably slower and take much longer.

As far as throwing gigantic energies around - our civ already deals in energy levels that dwarf the achievements of earlier cultures - and we also see a certain amount of death and destruction as a result. We continue to do it anyway because:

a) We find the benefits of having such energies to outweigh those costs.

b) We're used to doing it. Just as we take it for granted we can throw around X amount of energy without undue fear, future civs will presumably throw around even greater energies and not think twice about it. They will have appropriate safety protocols and such that they have developed - but they will still consider the benefits to outweigh the costs.

It doesn't take much of a course change to turn a ramscoop freighter into a world-wrecking weapon.

Actually it's not that easy. Adam (inventor of our wormholes and reactionless drives) weighed in on this many years ago. At high relativistic speeds, Lorentz contraction and distortion of the star field makes hitting something as small as a planet (space is very very big) very very difficult if not impossible if the ship is just left to its own devices. Hitting space habs would be even harder.

You could set up beacons or the like to make it easier for the ship, or have the ship go slower (which makes it easier to detect of course), but in that case you're using a relativistic strike as a coup de gracie rather than a surprise first strike - so a different situation entirely.

Realistically, freighters would probably be much bigger than that; after all, they have to sustain the crew for decades.

Why would you need a crew at all? If you can build ships of this kind you surely have automation that can let them fly themselves.

So what do you do, when you see a ramscoop drive light up at your next-door neighbour, headed your way? After all, you can't be sure the ship will make turnover at midpoint.

Lots of options:

a) Spread your civ as widely as possible so it become impossible for any one group to be sure of 'getting everybody'. An accident then becomes unfortunate, but not a species or civ ending event.

b) Communicate as widely as possible all the time so secret military buildups and attacks become harder and so that, if one does somehow take place everyone else knows about and can retaliate against the perpetrator.

c) Set up really good telescope and interferometer systems and watch other star systems like hawks. When you see a drive flare, keep an eye on it and confirm that it has started slowing down when it should. If it doesn't or if it goes out, go on alert, let everyone know and shift the orbits of your habs so they are harder to hit. Consider spreading clouds of dust and gravel around your planets or along the presumed path of the incoming ship to up the chance of it hitting something too big for its shields and being destroyed. Use weather machine tech on your planet to fire a multi-petawatt laser at the ship, which should do bad things to it or any incoming projectiles. Probably other options as well.

d) Set up ships in deep space as a retaliatory force. If an attack takes place they rev up and launch toward the attacker. They are detectable in flight, but if we're postulating this kind of thing anyway, the attacker is presumably no more able to stop the incoming ships than you could. MAD is a quite sensible policy with a demonstrated track record of effectiveness, really.

Etc.

Going back to OA, Ithuriel did a lot of work on starship drives a year or two ago and one of the things he concluded is that high acceleration sustained for long periods runs into problems even with amat or conversion systems. So starships may be more likely to accelerate at fractions of a G and just be able to keep that up for a long long time rather than rapidly boost up to high speed or boost constantly for a whole interstellar trip at 1G or the like. The waste heat issues seem to put a block on this kind of thing.

Todd