[SPACE 4e] System Design help? (star systems that is...)

[Qoltar]

The last 2 or 3 comments are interesting guys - but does that have any effect on my three potential planets?

Just wondering.

- E.W. Charlton

[balzacq]

Qoltar -- sorry for the thread hijack; I thought your question had been answered and I took the opportunity to quiz Mr. Zeigler.

Jon -- never mind, now that I have my book before me I see there is a planetary eccentricity table.

[Qoltar]

"Back" to this star system ... hhmm... this sort of a TRAVELLER questiuon now but here goes:

Would planetary masking be an issue for a starship jumping in from either JumpSpace or Hyperspace??

Also what are the likely travel times between the 3 planets??

- E.W. Charlton

[ericbsmith]

Originally Posted by Qoltar

"Back" to this star system ... hhmm... this sort of a TRAVELLER questiuon now but here goes:

Would planetary masking be an issue for a starship jumping in from either JumpSpace or Hyperspace??

Also what are the likely travel times between the 3 planets??

Those two questions are so campaign dependent as to be nearly impossible to answer.

First, by "planetary masking" I take it you mean that the star gets in the way of the incoming ships route so it is forced to drop from Jump Space at a location away from the planet?? That's always a problem with a Traveller style Jump drive, and if you go with a binary pair of stars it's double the problems, since either star has a chance of blocking access to planets around the other depending on the direction the ships are coming from and the distance between the two stars (two stars at 20AU are going to block more of each other's space than two stars at 20,000AU).

For the second question it is necessary to know what technology is available for FTL and STL drives, what speed they go, and what distance the 3 planets are from one another (which can vary at different times of the year). It takes, what, 8 months for us to go from Earth to Mars using current technology? But then we don't have Reactionless Drives as in Traveller; with a 1G constant acceleration (easy in Traveller) that same trip to Mars would take between 2-4.5 days, depending on the exact positions of the two planets in their orbit. With a Grav drive which can do 100G or more that trip could be cut down to less than 12 hours.

[Pragmatic]

I just got Space this week.

Back when I was using GURPS Traveller: First In, I found that, instead of one bright star (which doesn't have enough time to form a decent ecosystem), if you had two semi-bright stars (say, a Sol and a red dwarf), their combined luminosity gave you enough energy to get three planets into the life zone.

I found that you couldn't get a habitable world in the first sixth-ish of the life zone (too hot), nor the last third-ish (too cold). But it's possible to fit in a hot garden, a decent garden, and a cold garden in that distance.

As for just three worlds, how about five? Have a trinary system: A green/yellow sun (our sun is green with lighter shades of yellow; we just can't see green as well as yellow) with a close red companion, and a distant green/yellow companion with two worlds in its life zone.

Toss in a couple of asteroid belts, and a couple of gas giants, and it's a neat little system.

(Note: pulling this idea from On Death Ground/Shiva Option books...)

I'm SO looking forward to someone designing a spreadsheet to help with this. :)

[Pomphis]

Originally Posted by Pragmatic

if you had two semi-bright stars (say, a Sol and a red dwarf), their combined luminosity gave you enough energy to get three planets into the life zone.

How did you calculate combined luminosity and blackbody tempreratures ?

IIRC one first adds (all stars luminosity divided by the square of distance) before taking the fourt root and multiplying with 278. So a close companian red dwarf would add very little to the blackbody temperatures of planets.

[Pragmatic]

Originally Posted by Pomphis

How did you calculate combined luminosity and blackbody tempreratures ?

IIRC one first adds (all stars luminosity divided by the square of distance) before taking the fourt root and multiplying with 278. So a close companian red dwarf would add very little to the blackbody temperatures of planets.

Per Traveller: First In, pg 53 (Step 6: Locate Orbital Zones), if two stars have Very Close separation, simply add the masses and luminosities together and treat them as one star. This allows you to get the larger Life Zone of a brighter star, but with a longer lifespan.

As for red dwarfs, you should know it's been about a year since I've done this, so I don't remember how I did it. The idea is the same, though: a second, not-as-bright close companion that adds mass (to determine the Outer Limit) and luminosity (to determine the range of the Life Zone and the Snow Line and the black-body radiation of the planets).

I generally toss in a third star at such a point as to wipe out the last three or four orbitals.

[Pragmatic]

Originally Posted by Qoltar

Alright I bought GURPS:SPACE 4/e and I am looking for a little bit of advice or at least someone to point me in the right direction.

For a player in my campaign I need to concoct a star system that has THREE planets within the life zone. Thats right 3 (!!) planets in some kind of tolerable and believable orbit bands and such ...all of them plausibly habitable for humans. And is VERY "okay" if one of the 3 turns out to be a mostly "Desert World" . I also own INTERSTELLER WARS ....but I figure might as well use the more detailed system.

Okay, I've looked at the data. It's impossible, under the rules as written, to have 3 garden worlds for one star. Within the inner rings, the minimum separation from orbits must be 0.15 AU, and the minimum separation ratio is 1.4.

The range of black-body temperatures for garden worlds is 241K to 320K (page 113). Using the formula for placing pre-designed worlds, the radius of the orbit is 77300 / B^2 x sqrt(L). Using the range of black-body temps, above, the orbital radii would be 1.330 x sqrt(L) and 0.755 x sqrt(L), respectively. That means the geometric-average separation ratio would be 1.33, well below the mininum separation ratio of 1.40.

So pretty much nothing even remotely human-habitable can be fit in a third orbit. :( As I've previously stated, the first sixth-ish of the "Life Zone" (GURPS 3E Traveller: First In concept not brought in to 4E) is too hot and the last third-ish is too cold.

Too bad they don't have detailed star system generation any more. As it is, a lot of the numbers have changed. :shrug:

[Ze'Manel Cunha]

Originally Posted by Pragmatic

Okay, I've looked at the data. It's impossible, under the rules as written, to have 3 garden worlds for one star.

What about the double planet suggestion I made, along with a third world in a separate orbit?

And what discounts the idea of three habitable large moons around a gas giant?

[ericbsmith]

Originally Posted by Ze'Manel Cunha

And what discounts the idea of three habitable large moons around a gas giant?

Those have some serious problems because of the high levels of radiation (the gas giants magnetic field funnels stellar radiation right into the moons) and extreme tidal effects. On the up side, the extreme tidal effects means lots of volcanism, which means a strong magnetic field for the moon, which means possible protection from the radiation. On the down side, lots of volcanism means lots of, well, volcanos - lots of ash in the atmosphere and lots of volcanic gasses such as CO2, and pleanty of places you don't want to live unless you want your village to be incinerated once every couple generations. Not likely to be a nice place to live.

Not that it's impossible, but they're far less likely to be habitable.