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Old 05-31-2016, 06:32 PM   #1
Calvin
 
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Default Good ways to limit space travel?

I'm working on a new campaign for my group and need some help. TL9, hard scifi, and somewhat more serious.

The campaign is set in a trinary star system. The two primary sun sized stars orbit each other at ~144 AU, leaving them both enough room for their own set of interesting planets. Further out, at 288 AU is a smaller star orbiting the barycentre of the two larger stars, it also has it's own set of planets.

The plan is to have each of the two primary stars host a separate colonial empire, with the two not hostile, but not exactly friends either.

The third star is supposed to be either mostly or totally unexplored. What I want is for it to be currently inaccessible, and for some technological advance during the game to make it accessible. It's supposed to be a "captured" star, and is much older than the first two. (5 billion years compared to 11.5 billion). I basically intend it to be a Schrödinger's star. Maybe one of the habitable planets used to have a now dead civilization on it, maybe there's bronze age aliens going about their business, maybe there's the remnants of an FTL drive system to be found in that dead civilization if I want to expand the scope of the campaign.

But how would I even do this? My current plan for space travel is to have some as yet undetermined drive allow for constant 1g acceleration, with that providing "gravity". But even if ships need to stop to refuel, what's stopping them from just flying off to the third star, only expending fuel part of the time there and back? Alternatively, if I go to a very hard scifi approach and only have the engines in use at the very start and very end then they can still get to the third star, it just takes longer.

Basically, how do I stop two empires that are currently competing for habitable planets and useful resources from either wanting to or being able to travel to the star to see what goodies are to be gotten? I can't hide the star, I can't really stop anyone from getting there at TL9 if they're willing to take the time, and whatever is stopping both empires needs to have held up for the past 100-200 years. (I'm not certain on how long these two empires have been at TL9 with spaceflight, etc)
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Old 05-31-2016, 07:15 PM   #2
jason taylor
 
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Default Re: Good ways to limit space travel?

It is not necessary to make the third star impossible to reach, only to make it to big an investment for the return. Suppose recent engine upgrades can leave more holdspace.

Perhaps scouts had been there before but no attempt has been made to exploit it.


Another possibility. The fuel you use is only sufficient for a one way voyage at that range. The only reason you were able to settle the second star's worlds was that ore deposits were discovered making it possible to refine fuel for the return voyage on site. Once that was done colonies were gradually built. Now unmanned probes have discovered similar ore deposits on the third star's planets.
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Old 05-31-2016, 07:22 PM   #3
Calvin
 
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Default Re: Good ways to limit space travel?

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Originally Posted by jason taylor View Post
It is not necessary to make the third star impossible to reach, only to make it to big an investment for the return. Suppose recent engine upgrades can leave more holdspace.

Perhaps scouts had been there before but no attempt has been made to exploit it.


Another possibility. The fuel you use is only sufficient for a one way voyage at that range. The only reason you were able to settle the second star's worlds was that ore deposits were discovered making it possible to refine fuel for the return voyage on site. Once that was done colonies were gradually built. Now unmanned probes have discovered similar ore deposits on the third star's planets.
The trouble with it being scouted but unexploited is that it's harder to justify people just not knowing about many of the things I'd like to put there. Alien ruins, alien primitives, would be simple to spot. So either I decide ahead of time on what's there (somewhat defeating the purpose), or it must be something non-obvious to scouts (limiting my options).

As for distance, that just increases the time required. Sure, it might be far enough that to get there takes more than half the fuel, but then all the ship needs to do is not use as much fuel on the way there. Burn at the start to get up to speed, burn while there to slow down, coasting in the middle.

For distance to work the star needs to be REALLY far away. Ideally I want the star to be close enough to get to within at most a year of travel time once whatever limitation on travel there has been lifted.
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Old 05-31-2016, 07:26 PM   #4
Fred Brackin
 
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Default Re: Good ways to limit space travel?

Quote:
Originally Posted by Calvin View Post
I'm working on a new campaign for my group and need some help. TL9, hard scifi, and somewhat more serious.

The campaign is set in a trinary star system. The two primary sun sized stars orbit each other at ~144 AU, leaving them both enough room for their own set of interesting planets. Further out, at 288 AU is a smaller star orbiting the barycentre of the two larger stars, it also has it's own set of planets.

My current plan for space travel is to have some as yet undetermined drive allow for constant 1g acceleration, with that providing "gravity".
Sustained 1 G is seldom used with the words "TL9" "hard science"and "limited". You probably have to scrap this drive is you want limited space travel in pretty much any way. Sustainable !G would allow for very reasonable STL interstellar travel.

Also, any propulsion system even one that has to be Emergent Superscience that still acts in a Newtonian framework that allows for trips of 144 AU will go twice that far under some sort of circumstances.

You need some sort of non-Newtonian Superscience drive to enforce a hard range limit. Some sort of Jump or hyperdrive that required a target star and did not permit jumps to the middle of nowhere and di not allow for jumps of 288 AU might do the trick. Introduce the 288 AU drive when you desire.

If you drastically shorten the trips in normal space by jumping over most of that 144 AU in the middle you can use a much more hard science drive that could not travel 288 Au in less than decades. If it travelled no faster than our Voyager probes it could take centuries. Hundreds of AU is a long,long _long_ trip for a hard science propulsion system.
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Old 05-31-2016, 07:40 PM   #5
Calvin
 
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Default Re: Good ways to limit space travel?

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Originally Posted by Fred Brackin View Post
Sustained 1 G is seldom used with the words "TL9" "hard science"and "limited". You probably have to scrap this drive is you want limited space travel in pretty much any way. Sustainable !G would allow for very reasonable STL interstellar travel.

Also, any propulsion system even one that has to be Emergent Superscience that still acts in a Newtonian framework that allows for trips of 144 AU will go twice that far under some sort of circumstances.
The 1g thing I my current hacky solution to gravity on spaceships. It is/was my one TL^ thing to tie things together. You do point out the problems with that though so It's probably best to drop it.

The Jump drive seems like a pretty good solution, though I do still need some sort of sublight drive, or other way to get around the system. Each one has it's most distant planets at 48 AU from the star, so ships still need some way to manage their longest trips being about 48 AU without everyone being geriatric by the time they arrive. Or I remove all of the outposts and colonies too far from the star.

The other thing to consider is Lagrange points. I had intended to put [interesting things] at those points. Trojan planets in the L4 and L5 of the stars, space stations at the L1-L3 points. Though some of them are nicely at half the 144 distance. So maybe the jump drives need to be charged near a star, and then run off of that battery. They can either expend the full charge to jump to another star, or spend half to jump to somewhere else with the ability to jump back. It even nicely solves my in-system travel problem. Jump ships just need to store some charge to be able to get back from the outerplanets so they can charge at the star.
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Old 05-31-2016, 08:48 PM   #6
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Default Re: Good ways to limit space travel?

Radiation. Assume that radiation shielding was just good enough to make travel between A and B possible, if spectacularly ill-advised, and recent improvements in materials science finally allow shielding good enough to send a manned expedition to C (and make travel between A and B safe enough for the non-deranged or professionally obligated). Failing that, you can define your drive system to be something like 2300AD's stutterwarp: a maximum range of 7.7 ly before it has to discharge accumulated radiation into a gravity well. If it fails to do that, it crisps everyone and everything involved. Maybe the drive only now became efficient enough to operate that long without irradiating the crew and electronics?
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Old 05-31-2016, 08:52 PM   #7
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Default Re: Good ways to limit space travel?

Maybe use some sort of gateway device like the Mass Relays from Mass Effect? They can fling you to another relay almost instantly, but you need your own propulsion to go anywhere else.

So you have a linked pair between your two inhabited stars and nobody has found a way to the third one. The third star might have a dormant relay, or the players would have to build one when they got there. There could be a lot of questing involved in the new system to try and find the resources or knowledge to make a relay in the first place.
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Old 05-31-2016, 08:53 PM   #8
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Default Re: Good ways to limit space travel?

Quote:
Originally Posted by Calvin View Post
The 1g thing I my current hacky solution to gravity on spaceships. It is/was my one TL^ thing to tie things together. You do point out the problems with that though so It's probably best to drop it.
Any reasonable set of numbers, using hard science (the only way to go that way is to throw something the other way), 1g acceleration for more than a day or two would require energy sources not much more plausible than teleporting using a Ring of Wishing. I'm getting numbers that look like gigawatt outputs out of a laptop battery, and, just as unbelievable, the ability of the drive to survive that kind of energy density. That's some hot exhaust.

Honestly, if rotating (or counter-rotating, to avoid gyroscopic effects) or just plain living in microgravity doesn't work for you, artificial gravity is probably no more magical than 1g interplanetary travel. It also avoids implications of 1g travel that you are searching for a solution for.
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Old 05-31-2016, 09:12 PM   #9
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Default Re: Good ways to limit space travel?

If you want to limit travel to the third star, stay away from jump drive and stick with constant 1G acceleration--this model is a great way to keep things theoretically plausible and it provides hard-sci artificial gravity. Using this system makes acceleration and fuel storage/consumption huge factors in any travel.

To keep the third star inaccessible, make refueling difficult. This also keeps things believable; after all, why should refueling be an easy option, especially in the emptiness of interstellar space? Since constant acceleration at 1G would eat up a lot of fuel, just declare that it is an in-system-only option--Maybe just a few AU (an already enormous distance). And make refueling take a long time, requiring lengthy layovers--especially long ones if there is not a fuel depot established. This is related to Jason's suggestion that the fuel would only be enough for 1-way, since there would be no industrial infrastructure to support refueling at the destination. Travel to and fro would require an investment of human resources and decades of construction at the far end.

You could also make the orientation of the planes of the systems to each other work to your refueling advantage. Since most baryonic matter will be found roughly within the disk of the the ecliptic, if the stars had roughly parallel ecliptic planes most refueling stations (presumably servicing spacecraft utilizing the raw materials of asteroids and planets) would likely be no closer to the other system than the stars themselves. So there is no convenient half-way point. As a bonus, this coincidental arrangement provides a fertile field for all kinds of "Intelligent Design" theory subplots.
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Old 05-31-2016, 09:42 PM   #10
spacemonkey
 
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Default Re: Good ways to limit space travel?

If there was an ancient civilization, maybe one of its defense drones lasted just long enough to destroy the first scout ships, but damaged or destroyed itself in the process. The locals held back until now, with all sorts of theory, fiction, and religious nuttery about the third star/third star people, but someone managed to make the trip and return in one piece with some data. If there's a lowtech society, they could have suffered a tech collapse, so you could place the low tech species on the same planet as the high tech ruins.
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