GURPS Space campaign setting

[combatmedic]

Originally typed by MrId:
As I understand it, in this setting, the rule seems to be "artificial gravity and contragrav, but no grav drives." I'm not sure how that works, but since it's rubber science, it can be explained any number of ways. I think the goal is to avoid the dirt-cheap planet-cracking problem of reationless thrusters while still having artificial gravity. I don't know what the actual rationalization for this will be. But as for why no grav drives, well, 'cause the rules (or setting parameters) say so.

Unless I'm completely off base (likely), and in which case, grav drives seem like a logical consequence of general gravitic technology.

I had envisioned gravitics as a relatively young technology. It hasn't yet been sucessfully micronized, for example. Perhaps the grav drive is still on the drawing board? Maybe the Precursors used them?


I'm trying to work backwards from story assumptions, then determine what technology [real or imagined] would fit best. Rubber physics is okay in limited doses. The setting is space opera, not hard sci fi.


I am aiming for an ''Age of Sail'' feel, similiar to that achieved in Traveller. I worry that reactionless drives would cause problems with that, but maybe they wouldn't. I'll need to give it more thought...

Most of my players won't care about the technical aspects of the setting as much as I do. That's fine. I just like an internally consistent milleu.

[combatmedic]

Good point, Agemegos.

I'll have to read up on the various possibilities for STL drives before I make a decision. At this point, I'm not sure what fits best.

[Pomphis]

Originally Posted by Agemegos

Well, any spaceship drive capable of giving space-opera-like performance to spaceships is a weapon of mass destruction. Any object on an escape trajectory has 63 MJ per kilogram, no matter where it got it from or how long it took to accumulate.

How about pseudo-velocity and inertialess drives ?

[David Johnston]

Originally Posted by Agemegos

Jon's Law still applies. I echo Burnside's Advice.

Changing laws of physics is a dangerous thing to start, because the ramifications are uncontrollable, and usually fatal to suspension of disbelief.

Aw heck, once you start worrying about that you start to realise that space travel has no real gaming value because there's nowhere interesting to go.

[Fred Brackin]

Originally Posted by Agemegos

Jon's Law still applies.

Jon's Law would not apply directly to pseudo-velocity or inertialess drives. Those don't accumulate kinetic energy and no vehicle propelled in ths manner can be used as a kinetic energy weapon while under drive.

I suppose you could develop scenarios involving "intrinic velocity" but not all pseudo-velocity drives use an intrinic velocity concept.. It's a lot simpler if you don't.

The only way any sort of realisitic space propulsion could be involved in a true space opera setting is it they only needed it to travel short distances. Realisitc drive performance only travels long distances in relatively long periods of time.

Fred Brackin

[Rupert]

Originally Posted by Agemegos

Sure it does. It lets you get to a position of high gravitational potential. Then you can switch the drive off and fall back to Earth with a bang.

If the drive doesn't retain initial velocity, this does at least limit the kinetic energy you can obtain somewhat. Of course, it does raise the interesting question as to just what do you not retain your relative velocity, and I'm sure there's going to be some setting busting potential inherent to the answer, pretty much no matter what it is, if the setting is supposed to be at all hard SF - and that brings us back to your statement about technobabble just drawing attention to where you don't want it.

[MrId]

Originally Posted by combatmedic

I'll have to read up on the various possibilities for STL drives before I make a decision. At this point, I'm not sure what fits best.

FWIW, I mainly use nuclear pulse propulsion (which is slightly different from Orion drives -- mainly that the fuel isn't a pile of nuclear bombs and the explosions are internal) for long-haul STL flights (i.e., to the distance where FTL can be used) and a variety of other drives (Nuclear Thermal, largely) for short-haul in my setting.

GURPS stats for these rockets can be found in Vehicles, Vehicles Expansion 1, and Vehicles Expansion 2.

[Fred Brackin]

Originally Posted by Agemegos

Sure it does. It lets you get to a position of high gravitational potential. Then you can switch the drive off and fall back to Earth with a bang.

It just takes time, but Jon's Law admits that.

I said "directly" and this is a pretty indirect scheme. It wouldn't even work in some set ups.

It's as likely as anything else that turning on your inertialess drive detaches you from the local frame of reference and turning it off attaches you to a new local frame of reference. If your relationship to that new frame is that of a stable, circular orbit you'll have to do a de-orbit burn at a minimum .

It doesn't really matter if you can theoretically use a drive as a weapon as long as it doesn't make a _good_ weapon or specifically such a good weapon as to overshadow any other options in the setting.

Fred Brackin

[Flyndaran]

Originally Posted by Agemegos

Sure it does. It lets you get to a position of high gravitational potential. Then you can switch the drive off and fall back to Earth with a bang.

It just takes time, but Jon's Law admits that.

What if when the drive is turned off in such a situation all that imparted potential energy is suddenly changed to waste heat exploding the vehicle into useless but still inertialess mist?

[Fred Brackin]

Originally Posted by Flyndaran

What if when the drive is turned off in such a situation all that imparted potential energy is suddenly changed to waste heat exploding the vehicle into useless but still inertialess mist?

Then that's not a very useful drive and also why space opera drives usually don't conserve...well, usually they don't conserve lots of things.

Usually when you start breaking the laws of physics it's best to break them in all relevant areas and in a nice neat symmetrical fashion when you turn the physics-breaker on and off.

It's usually when you decide you're only going to break _just this once_ and scrupulously apply them the rest of the time that things start going wrong.

Fred Brackin