Planetary Gravity Well

[Yak Face]

I don’t think this is covered in the standard rules (I could be wrong), so I hope that other Pit users will offer opinions and help me to generate a House Rule.

How many space units does the gravity well of a "standard" size planet
extend, from the edge of the atmosphere, in terms of the ability to block hyperspace travel? My reason for asking is that there needs to be some reasonably objective number to assign that players can count on when making plans. Planning raids, figuring out how to escape authorities, etc. makes this knowledge pretty important, and a lack of consistency can make a GM look very opportunistic/arbitrary.

Any thoughts?
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[jmanski]

One rulebook (can't remember which one- probably 2nd Ed.) lists benchmarks for space travel: 50 space units is the benchmark listed for gravity well around a planet, if I'm not mistaken.
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[Grimace]

I think I remember something like that as well. I generally sit it somewhere between 50 and 200, depending on the size of the planet. If it's a gas giant with a gas mining operation, you're looking at 100 to 200. If you're looking at a terrestrial planet, depending on the size, it could be anywhere from 50 to 100. Earth sized planets might be 75 or so. Mars sized would be 60, Venus sized around 50.

Smaller planetoids such as Mercury or Pluto sized might only be 30 or so, depending on size. I don't think you want to get too much smaller than that, unless you're talking about just a honkin' big asteroid, and that might be 10 or so space units for a gravity well, if even that.

I think if you're just looking for a generalism, though, 50 works great. If you want more specific, vary it based on planet size/density/type.

[Yak Face]

Excellent - thanks very much! That's a great help. It makes perfect sense for bodies of different mass to have different gravity wells, so that will be taken into account. A chart can be quickly drafted using the guidelines you've provided. It's nice to fill in yet another important detail of the overall space combat picture.

In our Privateer campaign we fight (or flee) in space frequently. To support that I'm in the process of finishing up a system for space combat that ties together my favorite aspects of Star Warriors, the Rules Companion, and the 2nd Ed Rev&Exp - and encompasses the capital and starfighter scales. I'm basing the details of movement on SW and speeds on 2nd Ed, but developing a table-top measurement system to replicate it in place of a hex map, much like is used in other table top wargames. This GW distance item is relevant to my effort - a 50 inch (unit) interception space gives enough table room for several rounds of good action before the PCs can slip the surly bonds of earth and flee a star system.
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However beautiful the strategy, you should occasionally look at the results. -Sir Winston Churchill

[TrueGrit]

[vong]

I could go all geeky and say the formula to distinguish the attraction between two bodies is:
G * Mass1 * Mass2 / (D^2)

D is the distance between the two objects (from their respective centers
G is approximately 6.67 × 10^-11
Mass 1 and 2 are the respective masses

SO then the question becomes, at what point in gravimetric attraction does it pull you from hyperspace to realspace?

</geek>
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[Yak Face]

Errr... that sounds like a lot of work... I have a hard enough time getting the story line done for my adventures between gaming sessions, without the burden of higer math! I like my house rules the way I like my women - fast and dirty. I figure a bench mark for plain old regular planets and the occasional gas giant are enough for me to mess with. I appreciate all the good thinking, though!
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However beautiful the strategy, you should occasionally look at the results. -Sir Winston Churchill

[vong]

Yea i dont expect anyone to actually do the calculations in a gaming session. But there is a potential to do a few calculations before hand to get an idea of size and attraction
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[ifurin]

why not? it's not that hard of a formula and most of the gamers i know keep calculators on them. and realy what gm wouldn't love to make the game more realistic?

[Yak Face]

Your players keep calculators on them?? Wow... I suppose I must be operating in a different gaming "culture" if you will. Mine don't even bring pencils. Just a lust for cash and violence. Oh - and the need to escape reality for a bit.

I guess laziness is a key part of the approach I use - I just don't use anything other than planets with fairly standard mass/gravity in my adventures.
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However beautiful the strategy, you should occasionally look at the results. -Sir Winston Churchill

[vong]

yea, very different group. i have one that would do that, and one that wouldn't. the hard part would be putting in the mass of the planet ad hoc. i suppose you could calculate a few reasonable masses before hand
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[Yak Face]

I can see I'm dealing with real planners here - excellent! I'm going to have to continue to take advantage...
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However beautiful the strategy, you should occasionally look at the results. -Sir Winston Churchill

[garhkal]

For me the SU of a planet's well lasts 5 rounds for a speed 8 or better ship, 6 for one at 6-8 speed, 7 for one at 4/5 and 10 for one at 3 or less.
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[TrueGrit]

[garhkal]

Yup. And one thing i do is if they are doing a full dodge/piloting for that round they are neither gaining nor loosing space towards their destination... So that makes them think about whether to risk it or go for it but have a good chance of being hit.
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