Steve Jackson Games Forums Stardivers [Space]
 Register FAQ Calendar Mark Forums Read

 04-05-2017, 12:32 AM #1 David Johnston2   Join Date: Dec 2007 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.
04-05-2017, 09:31 AM   #3
Fred Brackin

Join Date: Aug 2007
Re: Stardivers [Space]

Quote:
 Originally Posted by David Johnston2 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.
I did this (without the multiple stardrives thing) and I picked 3.3x (in parsecs) the combined mass in Sols of the stars involved. no jumps into empty space possible.

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".
__________________
Fred Brackin

04-05-2017, 12:10 PM   #4
David Johnston2

Join Date: Dec 2007
Re: Stardivers [Space]

Quote:
The jump is instantaneous inside and out (except in the case of rare malfunctions) but the transit time is affected by the fact that you can only jump from the corona of a star and you don't arrive in the corona of the next star (unless you want to do go kaboom since the direction you are moving as you approach the star controls both the direction you are jumping and your vector on emergence and it doesn't correct for the relative velocities of the two stars). The corona doesn't usually damage your ship because you jump as soon as soon you hit it and you're moving at very high speed when that happens to minimize your time of exposure. Hence the name of the setting.

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.

04-05-2017, 12:22 PM   #5
Anthony

Join Date: Feb 2005
Location: Berkeley, CA
Re: Stardivers [Space]

Quote:
 Originally Posted by David Johnston2 I like the idea of squaring the mass.
It's not really necessary, even linear in mass means star importance maps pretty well to star brightness.
__________________
My GURPS site and Blog.

04-06-2017, 03:48 AM   #6
Whyte

Join Date: Oct 2008
Re: Stardivers [Space]

Quote:
 Originally Posted by Anthony It's not really necessary, even linear in mass means star importance maps pretty well to star brightness.
The number density of those big stars goes down like 10**-2.35 in the initial mass function, and it gets even worse once you take into account that the massive star lifespans are measured in millions of years rather than billions. I don't have an easy reference at hand for the number of observed stars per stellar mass, but lets assume the exponent is -3 as a test case?

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.

04-06-2017, 11:44 AM   #7
Fred Brackin

Join Date: Aug 2007
Re: Stardivers [Space]

Quote:
 Originally Posted by Whyte 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.
Gurps Space normally assumes that anything over an A is too rare to be worth putting on a random table. You'd hardly go over 2 solar masses with those.

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.
__________________
Fred Brackin

04-06-2017, 11:58 AM   #8
Anthony

Join Date: Feb 2005
Location: Berkeley, CA
Re: Stardivers [Space]

Quote:
 Originally Posted by Whyte The number density of those big stars goes down like 10**-2.35 in the initial mass function, and it gets even worse once you take into account that the massive star lifespans are measured in millions of years rather than billions.
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).
__________________
My GURPS site and Blog.

04-07-2017, 03:55 AM   #9
Whyte

Join Date: Oct 2008
Re: Stardivers [Space]

Quote:
 Originally Posted by Fred Brackin So the size of stars you need to consider is actually fairly limited.
Yep, like I said in my first response. However, if it is mass squared, then those massive stars, while very rare, become very very useful.

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.

04-07-2017, 07:09 AM   #10
Fred Brackin

Join Date: Aug 2007
Re: Stardivers [Space]

Quote:
 Originally Posted by Whyte Yep, like I said in my first response. However, if it is mass squared, then those massive stars, while very rare, become very very useful. .
They're probably too rare.

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.
__________________
Fred Brackin

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Fnords are Off [IMG] code is Off HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Illuminati Headquarters     SJ Games Discussion     Daily Illuminator     Forum Feedback and Help Warehouse 23     Warehouse 23 General Discussion     Warehouse 23 Digital     Pyramid Munchkin     Munchkin 101     Munchkin     Munchkin Collectible Card Game     Other Munchkin Games Roleplaying     Dungeon Fantasy Roleplaying Game         DFRPG Resources     GURPS         GURPS Resources         GURPS Character Assistant     Transhuman Space     Traveller     The Fantasy Trip         The Fantasy Trip: House Rules     In Nomine     Roleplaying in General     Play By Post Board and Card Games     Car Wars         Car Wars Old Editions     Ogre and G.E.V.         Ogre Video Game         Ogre Scenarios     Board and Dice Games     Card Games     Miniatures The Gnomes of Zurich     The Industry     Conventions     Trading Post     Gamer Finder

All times are GMT -6. The time now is 09:46 PM.