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Old 02-02-2011, 03:27 AM   #1
Agemegos
 
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Default Planets, gravity, G-experience, G-tolerance, and Free Fall skill

A GURPS character has a "home gravity" (B.17). within ±0.2 gees or this home gravity he or she acts as normal. For each full 0.2 gees difference between the prevailing gravity and a character's home gravity, a character suffers a -1 ro all DX rolls and DX-based skills. There is also a penalty to IQ and HT for gravity well above home gravity, but it comes in at larger values (B.350) so we don't have to worry about it for the purposes of this discussion.

A character can improve his or her performance in non-home gravities by one skill or by either of two advantages.

The skill is Free Fall (B.197), "the ability to operate in a free-fall (zero-gravity) environment." When you are in free fall you roll against the lower of this skill and your DX or DX-based skill for DX-based tasks. I presume that that means DX and skill without the penalty for non-home gravity, because it is hard to get rid of that penalty as we shall see below. If the penalty does apply everyone is going to be pretty clumsy in free fall, and stay that way despite acquiring Free Fall skill. (Note that there are rules for free fall conditions in the Free Fall skill description that do not appear in the rules section on 'Different Gravity' (B.350).

The first advantage (taken alphabetically) is G-Experience (B.57). This advantage costs 1 point per gravity "field" (the example making it clear that this means "value of local gravity"), and halves the DX penalty for operating in this "field". I am not sure of the rule for rounding fractional skill penalties (B.9 doesn't mention skill bonuses or penalties), but I am going to assume that you round up, that -½ becomes -0. The rules don't say how wide the band of gravities encompassed by a "field" is. I presume that the difference betyween 0.16 gee and 0.161 gee wouldn't matter to anything except a sensitive gravitometer, but I couldn't say whether the "field" encompassed ±0.2 gee (like a home gravity) or one of the 0.2-gee increments based on home gravity (so that a person from Earth with G-experience in the Moon's gravity would suffer halved penalties (-2 instead of -4) in the increment 0 gee to 0.2 gee), or what.

You can buy G-Experience in all gravities (ie. halve all DX penalties but not IQ or HT penalties) for 10 points.

Note that G-experience will never allow you to fully acclimatise to 0.5 gee if you grew up at 1.0 gee, etc.

The other useful advantage is Improved G-Tolerance. This widens the "G increments" around home gravity. For 5 character points you have no penalties in the range within home gravity ± 0.3 gees, and -1 per full 0.3 gees away from your home gravity. For 10 points you get -1 per full 0.5 gees, which is better than G-Experience in all gravities at the same price, and also reduces the HT and IQ penalties at very high gravities. For 15 points you get -1 per full 1.0 gees away from home; for 20 you get -1 per full 5 gees difference; and for 25 you get -1 per full 10 gees difference.

Unfortunately Improved G-Tolerance is not a learnable advantage. You can't buy it to represent acclimatising to a new planet's gravity.

As we saw a while ago, in a universe compliant with GURPS Space shirtsleeve-habitable planets will have surface gravities ranging from about 0.44 gee to 1.44 gee, none lower, and few higher (those not at all common and not very appealing). The average surface gravity of habitable planets will be about 0.8 gee.

Typical characters will have a home gravity of about 0.8 gee. They will suffer no DX penalty in the range approximately 0.6 gee to 1.0 gee. They will have a -1 from 0.4 to 0.6 gee, and from 1.0 gee to 1.2 gee which they can buy off for 1 point per "gravity field"—but we don't know how wide gravity fields are. They will have a -2 at 0.2 gee to 0.4 gee (encompassing no habitable worlds, but pertaining at some outposts and perhaps on some spaceships) and from 1.2 to 1.4 gee (including some habitable worlds and high-spec spaceships), which they will be able to reduce, but never completely eliminate. They will have a -3 in microgravity to 0.2 gee and on some, not very appealing, habitable worlds.

A player will be disadvantaging his character in a way that is hard to mend if he or she makes him come from a planet with a surface gravity much below 0.8 gee or much above 0.9 gee, because there are going to be plenty of inhabited worlds with gravities only a little above 0.5 gee or only a little below 1.2 gee.
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Old 02-04-2011, 06:53 PM   #2
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

I have a few issues with this.

1) Free Fall is a DX-based skill, which means that it suffers penalties for gravity increment. A person who grew up on Earth gets a -5 modifier to Free Fall. Once he or she buys G-Experience in the microgravity "field" this becomes -2. And that -2 can never, as far as I can see, be got rid of.

2) There is no way to completely acclimatise to a gravity more than 0.4 gee different from your home gravity. If you live on Earth until you are sixteen, and then join the Space Patrol or emigrate to Mars, you might with high-tech medicine be spry and active a hundred years later. But you will not have got used to low gravity.


These are serious problems for my SF setting, which involves PCs regularly travelling from planet to planet, with a strong emphasis on variety among those planets. I am strongly tempted to allow a character to buy a second or subsequent home gravity value for 5 character points. Can anyone see any problems with that?

I am also tempted to define a number of 0.4-gee wide gravity bands and have characters buy familiarity with them separately, rather than floating everyone off the peculiar value of their homeworld gravity.
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Old 02-04-2011, 09:09 PM   #3
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Being acclimatized to the gravity of a particular planet is a Feature. If someone lives in one place long enough that you think they should be fully used to it let them exchange their native default gravity for a new one.
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Old 02-04-2011, 09:28 PM   #4
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

I'm pretty sure that Free Fall completely replaces the penalties for being several gravity-increments away from home gravity. In other words, it's never penalized for DX penalties due to gravity, since it's only useful in microgravity.
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Old 02-04-2011, 09:42 PM   #5
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Quote:
Originally Posted by Langy View Post
I'm pretty sure that Free Fall completely replaces the penalties for being several gravity-increments away from home gravity. In other words, it's never penalized for DX penalties due to gravity, since it's only useful in microgravity.
That makes sense to me, similar to how the shield skill doesn't take an off hand penalty for using it in what's normally your off hand.
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Old 02-04-2011, 10:37 PM   #6
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Quote:
Originally Posted by lexington View Post
Being acclimatized to the gravity of a particular planet is a Feature. If someone lives in one place long enough that you think they should be fully used to it let them exchange their native default gravity for a new one.
Hmm. Fair enough. What about officers of the Space Patrol, who divide their time between inspecting asteroid bases, conducting investigations on planets with surface gravities between 0.45 gee and 1.45 gee, low gravity in space stations and accelerating ships, and free fall in orbiting ships? Is halved penalties (for 10 CP worth of G-Experience) the best they can hope for?

Quote:
Originally Posted by Langy View Post
I'm pretty sure that Free Fall completely replaces the penalties for being several gravity-increments away from home gravity. In other words, it's never penalized for DX penalties due to gravity, since it's only useful in microgravity.
I agree that it ought to work that way. But the rules don't seem to say that it does.
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Old 02-05-2011, 02:49 AM   #7
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Quote:
Originally Posted by Brett View Post
The first advantage (taken alphabetically) is G-Experience (B.57). This advantage costs 1 point per gravity "field" (the example making it clear that this means "value of local gravity"), and halves the DX penalty for operating in this "field". I am not sure of the rule for rounding fractional skill penalties (B.9 doesn't mention skill bonuses or penalties), but I am going to assume that you round up, that -½ becomes -0. The rules don't say how wide the band of gravities encompassed by a "field" is. I presume that the difference between 0.16 gee and 0.161 gee wouldn't matter to anything except a sensitive gravitometer, but I couldn't say whether the "field" encompassed ±0.2 gee (like a home gravity) or one of the 0.2-gee increments based on home gravity (so that a person from Earth with G-experience in the Moon's gravity would suffer halved penalties (-2 instead of -4) in the increment 0 gee to 0.2 gee), or what.
G-experience is weird:

In 3edition, it was a 10 pts advantage.
If you had it, you had double g-increment for the purpose of determining dx penalties.
4th edition made it into a levelled advantage, but forgot to specify how it work for partial g-xp.

The most strict reading would give you half penalty at 0.16 but not at 0.15 or 0.17... GM call needed.
A generous approach would be to give the effect in a g-increment wide window, but that mean 4 point in g experience would cover anything from .1 to 2g for an earth human, wich seem very generous.

By the way, in 3e, you could buy g-experience (the full 10 point one) once you had actual experience in 3 different gravity field.

Nb: half penalty is misleading. You don't divide the penalty by 2, you double the range of g-increment.

Quote:
Originally Posted by Brett View Post
I have a few issues with this.

1) Free Fall is a DX-based skill, which means that it suffers penalties for gravity increment. A person who grew up on Earth gets a -5 modifier to Free Fall. Once he or she buys G-Experience in the microgravity "field" this becomes -2. And that -2 can never, as far as I can see, be got rid of.
According to THS, and I see nothing to indicate it changed in 4th edition, microgravity and 0 gravity use different rules, ie the free-fall skill cap.
there is no -5 dx penalty to the free fall skill in 0g/microgravity, or to any dx roll, the rule for different gravity don't apply in 0 grav.

Celjabba

Last edited by Celjabba; 02-05-2011 at 03:00 AM.
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Old 02-05-2011, 03:02 AM   #8
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Quote:
Originally Posted by Celjabba View Post
Nb: half penalty is misleading. You don't divide the penalty by 2, you double the range of g-increment.
B.57 says
G-Experience 2
1 to 10 points

You have experience working in one or more gravitational fields other than your native one, and your reflexes adapt quickly to the way objects move and fall in those fields. You suffer only half the usual DX penalty for different gravity (see Different Gravity, p. 350).
Emphasis added.

It is Improved G-Tolerance, not G-Experience, which alters the width of an increment. And that is not listed as a learnable advantage. (B. 294)
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Old 02-05-2011, 03:12 AM   #9
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Quote:
Originally Posted by Brett View Post
B.57 says
G-Experience 2
1 to 10 points

You have experience working in one or more gravitational fields other than your native one, and your reflexes adapt quickly to the way objects move and fall in those fields. You suffer only half the usual DX penalty for different gravity (see Different Gravity, p. 350).
Emphasis added.
I know. But:

Quote:
Originally Posted by campaign p 350
DX: You are at -1 DX per G-Increment of difference
(-1 per two full G-Increments, if you have the GExperience
advantage,
And THS say the same.
i don't have my 3E space or uplift available, unfortunately.
But THS is very clear on this.

Quote:
Originally Posted by ths p 54
For most purpose, .. reduce dx by 1 for each full .2g increment of gravity different from the charcter native gravity, unless the charcter has the g-experience advantage. In that case, reduce it by 1 per 0.4g increment.
And THS point to C1p25 for the g-experience advantage, wich do say half-penalty, like the 4th edition one.

The advantage may say half-the-penalty, but the rule say double the g-increment.
(the result is roughly the same).
Unless you want to double-dip and have both half penalty and double-wide increment.

If you had g-tolerance, the .2/.4 above become .3/.6, .5/1, ...

celjabba

Last edited by Celjabba; 02-05-2011 at 03:19 AM.
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Old 02-05-2011, 04:09 AM   #10
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Default Re: Planets, gravity, G-experience, G-tolerance, and Free Fall skill

Quote:
Originally Posted by Celjabba View Post
I know. But:

Quote:
Originally Posted by campaign p 350
DX: You are at -1 DX per G-Increment of difference
(-1 per two full G-Increments, if you have the GExperience
advantage,
Hmm. That's a good catch. Looks like errata to me. That rule doesn't seem to be compatible with G-Experience being a 1-point to 10-point variable advantage.

Quote:
And THS say the same.

But THS is very clear on this.


And THS point to C1p25 for the g-experience advantage, wich do say half-penalty, like the 4th edition one.
THS is 3rd ed. No matter what it says or how clearly, it doesn't apply to 4th ed.

Quote:
The advantage may say half-the-penalty, but the rule say double the g-increment.
(the result is roughly the same).
No, the result is not the same at all. The halved penalty applies only in the "gravity field" that you have paid for.

And I have to say, I wouldn't want the rules to work in such a way that experience in low gravity made you better in high gravity. E.g. a character comes from a planet with 1.0 gee, and acclimatises to a space station with 0.5 gee. This should not make him or her better off in 1.4 gee.
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