Problem of math

[Catavarie]

Of course you could always allow them to travel back to the terran system and have them find it to be missing completely with no sign of its existence.

Or have the coordinates of the terran system be lost from knowledge since man had left it behind such a long time ago. Might just have to play with your timeline a bit. That would then make for a nice long Story Arc...the finding of Terra.

 

[WhatGravitas]

I third this. IIRC alpha centauri is something like 4.5 light years away.

Ditto.


Additionally, you can make the system a "charging" system: The computer must calculate the perfect trajectory (an arduous task for high speeds in multi-body systems), then it must find a homing signal of the target spacestation/homing beacon/whatever.

After all these processes, the ship can drop technobabble-thing, providing massive propulsion (like some kind of shockwave-engine).

This gives two problems for travelling to Sol: First, you must find the homing beacon, and second: The farer the target location is away, the more complicated the calculations become (and the more detailed stellar cartography you need), meaning exponential travel times (i.e. 0.5 ly: 1 day, 1.0 ly: 2 days, 1.5 ly: 4 days, 2.0 ly: 8 days, 2.5 ly: 16 days, 3.0 ly: 32 days, 3.5 ly: 64 days, 4.0 ly: 128 days, 4.5 ly: 256 days, 5.0 ly: 512 days (~1.5 years), 5.5 ly: 1024 days (~3 years), 6.0 ly: 2048 days (~6 years))

This makes short range travel fast, long range travel very slow... and the exponential complication of calculations is nice technobabble.

 

[ThirdWizard]

There was an episode of Star Trek: TNG where they were experimenting with a techology in which a planet would emit a wave that a ship could ride on to a destination. That's also a possibility similar to my ring suggestion above. The wave could just not be strong enough to reach another star system, stranding a ship out between stars if they try to go too far out.

 

[Whimsical]

I like the ideas posted so far. What I recommend: keep your system normal sized. Make propropultion technology such that at top speed it takes two months to get from one side of the system to the other. Make it a very risky thing to fly your ship at speeds that you would use in space while in an atmosphere. I wouldn't bar it, but I would have increasing catastrophic consequences proportional to the speeds being navigated. Plus I would set it up so that legendary ship crews has a good chance of pulling it off while n00bs and mooks will crash and burn. Every "legendary" crew member would be required to pull off a series of "imposible" skill checks out of their butt to do it, but it can be done. It's just "insane". Only to be attempted in dire emergencies (which is just another day at the office for legendary crews).

 

[Inconsequenti-AL]

I'd go with gates. They take a very long time to be maneuvered into place. Vastly speed up travel between them. Any technobabble reason should work.

Stealing from Richard Morgan:

The gates are based on duplicated alien technology. Who's to say there aren't other gates out there - just don't know how to connect to them yet? Makes it easy to add more locations in later if needed....

/stealing

 

[Harmon]

There were a few to many ideas that I had for adventures between planets, and travel should be free as the open road so gates and worm holes and such won’t really work.

It’s a non magic campaign as well, so that too is out.

I want no interstellar travel, but the speeds at which I would like to operate at place interstellar within reach, and that is what is confounding me.

I suppose that I should just go with the whole two-engine/drive system, one for atmosphere and the other for space travel.

Any additional thoughts would be appreciated, but with what I see here my understanding of the distances and speeds seems confirmed and campaigns along the lines that I want might not be do-able without a lot of hand waving.

Thanks for the effort.

 

[LightPhoenix]

So basically this is a Firefly-like setup - multiple planets in a solar system but no extra-solar activity?

I don't think speed is the problem here - no matter what, if you've got interplanetary travel that is is relatively quick (ie, a week or two) then there's always going to be the possibility of leaving the solar system. You can't change that, and you could perhaps use it as a hook of some kind.

The biggest impediments to leaving the solar system would be calculating trajectory and needing supplies.

Even with multiple planets, a good captain is going to want to conserve supplies - fuel, oxygen if you don't have some sort of scrubber system, food and other necessities, water, and I'm sure you can come up with more. So calculating a trajectory that not only avoids solar bodies (asteroids, moons, the sun, other planets, etc) but gets you from X to Y in the fastest and easiest path is no small feat even in one solar system. You can semi-handwave that plotting that course to an unknown solar system is all but impossible, especially without any sort of charts. Not to mention it would take decades, and no sure chance of finding anything.

The other problem of course is supply. You would need such an enormous amount of supplies to make that trip it would be rediculous to try and calculate the logistics of it. You would need vast stores of supplies and since that's mass, even more vast supplies of fuel - only governments, corporations, and the obscenely rich will even have the resources to attempt it - and why would they bother?

So, really the speed issue isn't really an issue at all. I wouldn't worry about it.

As for atmospheric stuff - as someone said above, spaceships don't have to worry about friction. The largest spaceships will be unlikely to be able to land on a planet (think Enterprise, Galactica, and other large-ish ships). Smaller ships might be able to navigate both atmosphere and space, but atmosphere is going to be much clumsier and more stressful on the ship unless it is specifically designed to do both (Serenity, Raptors, Shuttles, Puddle Jumpers) - and even then, atmospheric craft (ie fighters, bombers) will be more than a match for it.

[edit]Now I really want to play StarDrive! Even a PbP game!

Speaking of though, I'm sure GURPS has a few books on the issue. I'd recommend checking out StarDrive and Alternity if you can find them - they sound like they might be a good reference. Also, you can always Wikipedia our solar system and nearby ones (Alpha Centauri, Betelguese) to get some idea of distances and speeds.

 

[Mishihari Lord]

Yes, your system should be smaller.

Also, you could make a propulsion system external to the ship. There are stations around each planet that have accelerators that can launch and decelerate ships ships with enough acceleration to reach remote locations in a reasonable amount of time. On their own the ships can only move at the speed you mentioned. The down side is that you can only easily reach locations where there are stations. Or maybe that's an upside. You could base adventures around finding locations of lost stations with working accelerators.

 

[Knight Otu]

I want no interstellar travel, but the speeds at which I would like to operate at place interstellar within reach, and that is what is confounding me.

If you want to place interstellar travel out of reach, have you considered to place an "unsurmountable barrier" around the system? Perhaps the system is orbited by a thick shell of debris that just cannot be navigated. Only if you had a FTL drive you could circumvent the debris entirely. A favorite of sci-fi writers would be a semi-permanent local hyperspace "storm" that unpredictably strikes through into the normal space, making interstellar travel an uncalculable risk. Only within a certain radius around the star is the space-time continuum stable enough to normally be safe from the storm. Normally. Perhaps there are some FTL-capable ships stationed in the general area of the system, commanded by an AI acting on out-of-date orders to "quarantine" the system?

 

[Slife]

There were a few to many ideas that I had for adventures between planets, and travel should be free as the open road so gates and worm holes and such won’t really work.

The hyperdrive requires a huge amount of energy to initially activate. Once it's online it requires very little additional power, but virtually all vessels need a launchpad to go into hyperspace. Coming out of hyperspace will store a significant fraction (three quarters?) of the initial energy in the hyperdrive's core - this can cause serious damage to the system if left there for a couple of days (varies by ship, of course). Thus, it is only practical to begin and end near space stations. Intersteller travel will end up with you being lost in space.

Or maybe coming out of hyperspace requires interfacing with something designed to take you out from the realspace side. Then you can't go anywhere that doesn't have a station. (maybe there are also natural places which do the same thing)