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Old 05-31-2016, 10:59 PM   #11
thrash
 
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Default Re: Good ways to limit space travel?

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Originally Posted by Calvin View Post
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, ...
These don't exist in a binary system with more-or-less equal masses. You need the smaller mass to be less than ~1/25 of the larger mass for the equilateral points (L4-L5) to be stable. The co-linear Lagrange points (L1-L3) do exist, but stable orbits around them (halo or Lissajous) will be extremely difficult to find and maintain.

I would assume that both systems were colonized from somewhere else at nearly the same time, not one from the other. That gives you a space race to drive development, even if it isn't strictly economical. If your default drive is space sails (photon or magnetic), your "breakthrough" could be the fielding of laser/maser or particle beam boosters.

Your target world could have an optically thick atmosphere that limits attempts to map its surface from the original colony systems.
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Old 05-31-2016, 11:01 PM   #12
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Default Re: Good ways to limit space travel?

Maybe when the higher ups saw the oddities reported by scouting robots they concocted a convenient lie layered with half truths about the impossibility of getting there/getting information from there, and began a fnord space program to rush into the potential riches and claim monopoly.
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Old 05-31-2016, 11:16 PM   #13
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Default Re: Good ways to limit space travel?

If the 3rd star is a captured wanderer, its orbit isn't likely to be circular. Give it an eccentric orbit that has only just brought it close enough to be reachable.
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Old 05-31-2016, 11:34 PM   #14
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Default Re: Good ways to limit space travel?

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Originally Posted by RyanW View Post
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.
I second this. Whatever probables actuarial artificial gravity would introduce into the setting wouldn't be that much more outrageous then whatever allows these 1g drives to operate.
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Old 05-31-2016, 11:50 PM   #15
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Default Re: Good ways to limit space travel?

Possible scenario:

Ships which will make that trip are very expensive, and neither empire can afford to just throw them away.

The third star is sending more radiation in the band usually used for communication, making it impossible to maintain contact with ships within (some distance) of it.

The first several ships sent to explore were lost. No data came back showing what happened or why. They're just gone. Neither empire is willing to send more because then the other will have an advantage in material.

Now, a new communications array has been invented which should allow communication (at light speed). So now there's reasonable expectation that at least data will come back.

Who would be crazy enough to go out on this ship knowing the previous expeditions were lost? The most likely scenario is that this ship will suffer the same unknown fate as the prior ships. But the brave crew will go down in history as the discoverers of... whatever is there.

Maybe the communication system was invented and then rapidly stolen by the other empire and now both are racing to be the first to send their suicide squad to discover what's there.
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Old 06-01-2016, 12:15 AM   #16
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Default Re: Good ways to limit space travel?

I think I'm probably going to use the jump drive option.

The trouble with the constant 1g is that if something is out of range for the sup to constantly burn during the trip, then all it needs to do is not constantly burn. Do it for half/one quarter/etc the time and you still arrive just fine.

The radiation idea is good, both the lethality and the interference with communications, it was actually what I was imagining. The jump drive option just happens to solve the second issue of in-system travel without the 1g drive. It also has less of a "footprint" than the radiation thing, which might raise other issues.

Quote:
These don't exist in a binary system with more-or-less equal masses. You need the smaller mass to be less than ~1/25 of the larger mass for the equilateral points (L4-L5) to be stable. The co-linear Lagrange points (L1-L3) do exist, but stable orbits around them (halo or Lissajous) will be extremely difficult to find and maintain.
Don't exist at all? Or do they have the same instability that the L1 through L3 normally have? The plan is for two 1.2 solar mass stars and one 0.6 solar mass star. I don't suppose there's some other set of gravitationally stable points to use?

Quote:
I would assume that both systems were colonized from somewhere else at nearly the same time, not one from the other. That gives you a space race to drive development, even if it isn't strictly economical. If your default drive is space sails (photon or magnetic), your "breakthrough" could be the fielding of laser/maser or particle beam boosters.
The plan is actually to have the larger of the two systems (It kinda just happened during system generation, I ended up with several more orbits to fill on the first of the two 1.2 solar mass stars) be home to this campaign's "Earth". During TL8 a colony ship was sent to the second star where a second habitable planet was found. In the vein of the British colonization of Canada the colony continued to get more or less reliable support to help it grow. It also achieved independence in the same way Canada did around late TL8, early TL9. The difference is that now the mother government is sort of regretting letting go so easily. The first star is home to a Representative Democracy with heavy corporate influence. It's in-system (in-star?) outposts and colonies each with a corporate government. The second star is home to an Athenian Democracy, transitioning more and more towards a Cybercracy, limited only by how powerful they can build their computers. The idea is that the mother government has a much better developed industrial base, with a lot more natural resources. The cybercracy on the other hand has fewer resources (though not a massive shortage), but have gotten better at using them effectively and are somewhat more advanced.

===

As a total aside, the Space book is really great. I got pretty much all of the inspiration from the setting as I was rolling up the three star's planetary systems. I got one large system with a bunch of good resource rolls, that later in generation got a lot of Standard or Delayed rolls for TL. The second system had fewer bodies, but got very good rolls during TL generation. No Delayed and most of the Advanced. Finally I got a third star that has a gas giant in the habitable zone (Using eccentric gas giant layout) with a whole bunch of habitable moons.
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Old 06-01-2016, 12:39 AM   #17
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Default Re: Good ways to limit space travel?

The treaty that ended some previous hostilities included not setting up new colonies, including the other star. The "no expansion" part of the treaty ends during the campaign. Now you don't even have to invoke some sort of weirdness!
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Old 06-01-2016, 04:04 AM   #18
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Default Re: Good ways to limit space travel?

You really cannot have long term 1g drives in hard science TL9. A small fraction like 0.001g is much more likely as you are really energy limited when you want to make your reaction mass last long enough for maximum total speed.

And really with hard science there is nothing likely stopping things from traveling to the further star, it will just take longer.

So I would go by the one miracle rule and add something like a pseudo velocity drive that is limited in operation duration until it needs to discharge in high enough gravity, with the third star being further away than the maximum. Also have the alternative engines be really poor. Thus your options are along the lines of: Take few weeks to get to star B or a decade to star C.. so no one bothered as there was something more important to spend the money on. Then when you want it you could allow a breakthrough in the technology to allow for the travel.. or perhaps a discovery of large enough objects in an oort cloud type thing to allow discharging the dive on the way(making travel to other star be: accelerate at the oort cloud, wait, accelerate,decelerate to the target star system).
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Old 06-01-2016, 08:08 AM   #19
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Default Re: Good ways to limit space travel?

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Originally Posted by Calvin View Post
I think I'm probably going to use the jump drive option.

The trouble with the constant 1g is that if something is out of range for the sup to constantly burn during the trip, then all it needs to do is not constantly burn. Do it for half/one quarter/etc the time and you still arrive just fine.
...
The plan is actually to have the larger of the two systems (It kinda just happened during system generation, I ended up with several more orbits to fill on the first of the two 1.2 solar mass stars) be home to this campaign's "Earth". During TL8 a colony ship was sent to the second star where a second habitable planet was found. In the vein of the British colonization of Canada the colony continued to get more or less reliable support to help it grow. It also achieved independence in the same way Canada did around late TL8, early TL9. The difference is that now the mother government is sort of regretting letting go so easily. The first star is home to a Representative Democracy with heavy corporate influence. It's in-system (in-star?) outposts and colonies each with a corporate government. The second star is home to an Athenian Democracy, transitioning more and more towards a Cybercracy, limited only by how powerful they can build their computers. The idea is that the mother government has a much better developed industrial base, with a lot more natural resources. The cybercracy on the other hand has fewer resources (though not a massive shortage), but have gotten better at using them effectively and are somewhat more advanced.
You'll have to think through the implications of a jump drive, then. For instance, unless it is limited in drastic ways any ship can escape combat by jumping, so all combats must be mutually agreed upon. I.e. both sides have to want combat. It's hard to trap and destroy a weaker force.

Is there a reason that you picked 288AU as a distance for the third companion star? There are trinary systems where the third orbits much farther than that. 1000AU might solve your problem.

Or, I'd say, drop the 1g reactionless drive and use jump gates. This has a number of advantages from your point of view. (Other than that reactions drives offend me, of course.) One is that it introduces good handwavium: the gates are wormholes that you have to first grow to size and then you have to ship one massive end of it across real space to make the gate. This is expensive and time consuming. Obviously, shipping them smaller distances is less onerous so you might have only one or two long wormholes between the two near companion stars but several smaller ones within each system. Have the stronger empire have a Gibraltar-like extraterritorial outpost in the weaker empire's system or something- it makes for interesting politics. Perhaps they control the gate between the two stars? And everyone (players) groks wormholes. Another advantage is that these gates create natural chokepoints for trade and combat. A final advantage is that it explains why the 1000AU system is only now being explored: someone finally got around to shipping a wormhole there through slow-space. Or alternatively, create great upheaval in your campaign by developing a jump drive! Suddenly these gates are obsolete! Either way, though, there still probably would have been unmanned probes to the distant star. I don't think there's any way around that. It might take them a century to get there, though, using conventional drives, so the data available now might be old TL7 stuff- not a lot of detail, but a few damned shocking images in secret files somewhere...

For shipboard gravity use spin of some sort.

I agree with making one star much smaller than the other, among the two developed systems. You could make one a small red dwarf with a single planet in the goldilocks zone, but it was such a great garden world that the initial colonization effort ages ago chose it despite the very short year. So now that is the older, more established empire, with almost every airless rock in the system colonized. Then the younger system is a larger star with a wide goldilocks zone with two or even three planets in it, but none are "just right" and needed some development, so it was colonized later from the older colony at the smaller star. This explains the "Gibraltar" outposts in the newer larger system, and creates political strife in that while the older empire might be more advanced somehow the newer empire is larger and more populous with greater potential resources. At TL9 no one is doing semicore mining so the smaller older empire might even be approaching a resource-constrained environment, especially if it is poor in asteroids and other small exploitable bodies. When you have to land on a big rock (i.e. a planet) to do any mining then gravity is a bitch. This creates an almost early-UK-USA vibe. There might be more than one "Gibraltar". To make it really interesting have one such be the Old Empire's biggest source of some sort of unobtanium, whereas the New Empire thinks that the entire larger star system should manifestly belong to them!

Last edited by acrosome; 06-01-2016 at 08:22 AM.
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Old 06-01-2016, 08:12 AM   #20
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Default Re: Good ways to limit space travel?

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Don't exist at all? Or do they have the same instability that the L1 through L3 normally have? The plan is for two 1.2 solar mass stars and one 0.6 solar mass star. I don't suppose there's some other set of gravitationally stable points to use?
Don't exist at all. An object at L4 or L5 is orbiting the primary (larger) mass, with just enough perturbation from the secondary to keep it fixed in place (in a co-rotating coordinate system). If the secondary is too large, the object essentially "doesn't know" which mass to orbit and wanders around instead.

Your system will have long-term stable restricted four-body (three stars + object) orbits, but they won't be confined to particular points in space. In fact, they probably wander around all three stars, taking tens or hundreds of thousands of years to make the circuit.

The Lagrange points are very much a special case in astrodynamics, although one that turns up fairly frequently in real life.

Last edited by thrash; 06-01-2016 at 08:19 AM.
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