04-05-2017, 12:32 AM | #1 |
Join Date: Dec 2007
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Stardivers [Space]
Assume a hyperdrive that can let you make jumps with a maximum range based on the mass of the sun you are leaving. What do you think I should multiply the sun's mass by to get the length of the jump? I'm assuming that it is possible to mount more than stardrive on a ship for increased range but the the only ships that do it are message boat and smugglers.
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04-05-2017, 03:19 AM | #2 |
Join Date: Oct 2008
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Re: Stardivers [Space]
It depends on the hows:
1. How big is your setting? 2. How quickly do you want the PCs to be able to get from planet X to planet Y? 3. How much time does the jump (or recharge afterwards) take? 4. How often do you want them to travel? 5. How important is travelling to the campaign: is it an adventure on its own, or will it be simply skipped? Since you wish to tie it to the star mass, it implies to me that you do want the travelled distance to matter. Stellar masses are roughly from 0.1 Msol to 100 Msol, with the massive stars very very very very very rare. In practice, most of the stars that the PCs would ever visit would be in the 0.1 - 1 Msol bracket (earth-like planet's host star would probably be even closer to something like 0.7 - 1.3 Msol, so you get very very small range if you focus on 'typical' space opera planets), with stars more massive than 3 Msol or so being so rare as to not really matter for campaign planning (save perhaps as a military base, see below). Since the more massive stars are very unlikely to host habitable planets and they are so rare, any benefit you might gain from a longer jump is negated by the need to travel there, first. One way to make the big stars matter would be to make it jump-time always a fixed length, regardless of the distance jumped, and make the distance x*(Msol)**2 (factor times mass squared). This means a star of 10 Msol would have a jump distance 100 times more than a normal sun-like star, which would definitely make them more desirable, almost like wormholes in other scifi (Honor Harrington comes to mind). The squared mass also means that the smallest red dwarfs might stay uninhabited or even unexplored, since they might be too far from another star to get back to it with a jumpdrive: say 0.1 squared is 0.01, and if the distance to the nearest other star is about 1 parsec, you need x = 100, or that star becomes a dead end for FTL. So, lets say that the jump takes a day, your setting is 1000 parsecs across, and you want your PCs able to travel that in a month. In other words, you want 30 jumps to cover that 1000 parsec distance, which means each jump should be about 33.3 parsecs. Since you probably have suitable 1 Msol stars within that 33.3 radius that are more or less along a straight line, that would imply to me that something like x = 50 parsecs would be fine, allowing for a slight fudge factor. Note that if you use the squared mass, this means if you have a 5 Msol star somewhere in your setting, they can reach any point of your setting in one jump: 50*5**2 = 50*25 = 1250 parsecs. Makes for a very nice place to have a fleet presence at, so that you can reinforce any part of your empire in a day (from when you hear that something is wrong, which might take longer). Such higher mass stars would become nexi for high-speed interstellar travel, funneling trade through them. Which has a nice 'geographical' result for trade patterns, meaning you have more 'neglected' systems farther away from the high mass stars, where tramp freighters might ply their trade. Last edited by Whyte; 04-05-2017 at 03:32 AM. |
04-05-2017, 09:31 AM | #3 | |
Join Date: Aug 2007
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Re: Stardivers [Space]
Quote:
Using the stellar distribution from (probably) First In it gave me interesting results. G-class stars usually connected to something though direct links between inhabited systems would probably be rare. 3 to 5 jumps in a zig-zag for what would have been a straight line separation of 20-30 parsecs was the norm. M-class dwarves seldom connected to anything except the other stars in a multiple star system. Most of the time they could be ignored. A-class stars usually did connect to at least 1 more A-class and these links could form the backbone of a network. In my setting long trips were referred to as "taking the A train".
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Fred Brackin |
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04-05-2017, 12:10 PM | #4 | |
Join Date: Dec 2007
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Re: Stardivers [Space]
Quote:
I like the idea of squaring the mass. It will help magnify the strategic importance of larger (named) stars even though they're largely worthless for more than military bases and transhipment points as a place of habitation while isolating the annoyingly common smallest red dwarfs. It's impossible to leave an M7 dwarf by normal means so I can just leave them off the map. So if x=12, let's say, then anything smaller than a M4 dwarf doesn't exist as anything except a one way trip. |
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04-05-2017, 12:22 PM | #5 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Stardivers [Space]
It's not really necessary, even linear in mass means star importance maps pretty well to star brightness.
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04-06-2017, 03:48 AM | #6 | |
Join Date: Oct 2008
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Re: Stardivers [Space]
Quote:
This means that a star of 10 solar masses is 1000 times less likely to be found in the same volume than a 1 solar mass star. Granted, the volume that the 10 solar mass star jump would encompass is also jump_distance**3, so you might actually still gain a small benefit from re-routing via the more massive star, depending where you start in that sphere and where the target is. If you use squared mass, though, you accomplish dropping the low-mass stars like the red dwarfs, and you make the high mass stars REALLY useful. This, like David points out, has some cartographic advantages for the setting. |
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04-06-2017, 11:44 AM | #7 | |
Join Date: Aug 2007
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Re: Stardivers [Space]
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Yet A's are common enough. Earth has at least 2 decently close. Sirius at 8.3 ly and Vega at 25. You'd probably need to go 400-500 ly to find a giant star that'll end up in a core-collapse supernova. I think Antares is the closest. So the size of stars you need to consider is actually fairly limited.
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Fred Brackin |
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04-06-2017, 11:58 AM | #8 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Stardivers [Space]
That actually has a kind of useful effect, though, in that it means your routing will actually be dominated by G-class stars (the initial mass function seems to flatten out somewhat below 1 stellar mass, and even if it didn't, lifespan pretty much ceases to be a factor for anything smaller than a G-class star).
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04-07-2017, 03:55 AM | #9 | |
Join Date: Oct 2008
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Re: Stardivers [Space]
Quote:
If you use just mass, I wouldn't actually bother with it. The most common (i.e. habitable) planets you'd even bother to visit would likely be around K & G stars (M dwarf flares would make habitability an issue and the liquid water zone planets would likely be tidally locked, too), so the difference in masses is so small that it is not worth adding as a complication, IMHO. If you want to discriminate against the ubiquitous red dwarfs, you could easily put in a cutoff at 0.5 solar mass or so and claim that any star smaller than that doesn't allow the stardiver jump drive to work because of reasons. If the jump distance is small (less than a few parsec), then you might get a Traveller like situation, where you have jump routes, which is nice for some campaign purposes, but also requires you to map the routes (Traveller flinched and did it just in 2D). If the distance is long (10+ parsecs), the you can pretty much assume that you will find a suitable star more or less on the direct line, and there are no more 'routes'; it just adds to the travel time, making it more akin to hyperdrive, with the requirement of a star just being a campaign tweak. EDIT: Actually, now that I think about it... if the jump is connected to the surface gravity of the star (i.e. the gravity at the stellar atmosphere, the photosphere), then that would actually discriminate against the biggest stars since they are more 'puffed up' than our Sun, and favor red dwarfs! You would feel more of a gravitational force in a corona of a red dwarf, since you would be so much closer to its center! The jump points of choice would become the white dwarfs, which are even more compact. Last edited by Whyte; 04-07-2017 at 04:35 AM. |
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04-07-2017, 07:09 AM | #10 | |
Join Date: Aug 2007
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Re: Stardivers [Space]
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http://astronomy.stackexchange.com/q...nt-stars/18562 ....has a calculation that of the 7000-odd stars within 50 parsecs in the Hipparchos catalog there are _no_ type O's and only 2 or 3 M-class giants. There were 29 B's and he didn't bother to count the A's like Sirius or Vega. This is why Gurps Space doesn't randomly place stars above A.
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Fred Brackin |
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