Re: Downloadable Spacemapping

My answer was based on the theory that you were trying to do this within a single star system.

If what you are asking has to do with going from star to star, its unlikely that you'll care at all about the movement of planets within their respective star systems, nor about the movement of stars, which is at a glacial pace compared to anything needed to travel from one star to another in a game related pace.

Once again, though, its going to be more interesting to figure distances, so that you can look at time traveled via different speed craft

Lance Berg wrote:


goldman@xxxxxxxx wrote:

In rec.games.frp.gurps Rainbow Warrior <pizza@xxxxxxxxxx> wrote:

Anyone know of any good programs to do 3D mapping, even with pre-setup worlds & some basic data would be cool too. I am starting up a space campaign and dread the PC question "How far is it from Planet A to Planet B in a straight line?"
I don't really need to go as far as orbit position calculations.



"Two weeks ship time, three months Station time." Is the answer the
players in my latest game got when they asked. And then I pointed out
that no one in the group had *any* shipboard skills other than vacc suit.

So far it is working out well.

Planets don't sit stationary waiting for you to make a trip, they move around in those orbits.

Even assuming you have ship drives sufficient to make orbital mechanics fairly ignorable, the answer varies depending on the date you plan to make the trip.

The distance from Mars to Earth, for example, varies from .5 AU to 2.5 AU, since both planets orbit the sun, Earth at 1 AU and Mars at 1.5 AU (rounding off a lot for simplicity). And the latter assumes a straight line trip that goes right thru the sun, its likely any real route at that point would be at least 3 AU distance.

Travel times also get funny, assuming you have a ship that can accellerate constantly all the way (well, accelerate halfway and then slow back down the other half), a trip of 5 AU isn't 5 times as long as one of 1 AU.

And then there's the differences between one ship and another; Say a passenger liner makes a constant 1G, a cargo ship makes do with .5G, while military or private yachts make 2G and courriers can do 4G; that courrier is going to make a much quicker journey than the slow cargo craft.

If nobody in your party has any knowledge of the intricacies of ship operations, you can get away with just making up some travel times, but since some of your players probably have a clue, it would help if you included some of these variables to make it look like you'd actually done the math;

Say you have 3 inhabited planets:
Cargo Passenger Courrier A-B winter 2 weeks 1 week 3 days
A-B spring 4 weeks 2 weeks 1 week
A-B summer 8 weeks 4 weeks 2 weeks
A-B fall 4 weeks 2 weeks 1 week

A-C year one 4 weeks 2 weeks 1 week
A-C year two 8 weeks 4 weeks 2 weeks
A-C year three 12 weeks 8 weeks 4 weeks
A-C year four 8 weeks 4 weeks 2 weeks

A-C use same chart as BC but add a half week in the summer, subtract half a week in the winter

Thats pretty bad, really, and I'm sure an hour with a calculator and some scratch paper could give much better figures, but we'd need some clue as to what descisions you've made in terms of ship capability and so on.

Goldman's answer was reasonably correct for the ignorant; you may end up sitting around the station for a while before the next departure, and then the trip will take as long as it takes. On my chart above, will anyone really launch a ship in the "summer"(of world A) or for trips to/from C, during the third year of the cycle? Might want to wait till the planets are closer together!

Lance
.

Relevant Pages

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