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Old 03-04-2013, 12:23 AM   #1
scc
 
Join Date: Mar 2013
Default [Space] Gravity for Human Homeworld

OK, I've had the beginnings of an idea for a space campaign and I'm part way through rolling up the first of the two minimum habitable worlds in the system (It's going to look a bit Steam-punk Firefly I think) but I've run into a problem.

The generated gravity comes out at 0.6607 G, now a nice low gravity is good for some of what I want to do (I think) but this is supposed to be the human home-world in this setting and could cause problems, chances are that any other world will have a higher gravity, and putting the gravity this low means that I can't use normal 1G humans to hopefully reduce complications.

I was thinking that I could up the gravity to 0.81G and rule that everybody has a home Gravity of 1G, is this a bad idea or not?
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Old 03-04-2013, 01:10 AM   #2
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Default Re: [Space] Gravity for Human Homeworld

I've always thought that there should be give and take between gravities one is used to from living there, and what species native gravity they evolved in.

With so little known, you could easily make nearly any claim and have it be reasonable.

0.81 would mean that they wouldn't suffer any issue from up to 1.00 gravity other than fluff discomfort as they get used to it.
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Old 03-04-2013, 01:32 AM   #3
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Default Re: [Space] Gravity for Human Homeworld

What I'm seem to be aiming for is very early 'hard' sci-fi, the sort were the people today who would know that something doesn't/wouldn't work didn't.

How much early sci-fi brought up the subject of varying gravity on human worlds? Especially as more then fluff piece
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Old 03-04-2013, 02:01 AM   #4
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Default Re: [Space] Gravity for Human Homeworld

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Originally Posted by scc View Post
The generated gravity comes out at 0.6607 G, now a nice low gravity is good for some of what I want to do (I think) but this is supposed to be the human home-world in this setting and could cause problems, chances are that any other world will have a higher gravity, and putting the gravity this low means that I can't use normal 1G humans to hopefully reduce complications.
In GURPS, ones home gravity is a band 0.2 gee either side of the gravity one grew up in. People from a 0.66 gee home have no problems or adjustments between 0.46 gee and 0.86 gee.

I did a little study of the distributions of surface gravity on worlds generated using GURPS Space 4th ed., and how the range varies with Habitability or vice versa. The results are in an old thread, and perhaps they will help you understand the issues you face.
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Old 03-04-2013, 02:17 AM   #5
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Default Re: [Space] Gravity for Human Homeworld

Brett, from what I can see it's likely that the gravity generated is a bit on the low side, which is likely to be a problem for what I'm aiming for
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Old 03-04-2013, 04:19 AM   #6
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Default Re: [Space] Gravity for Human Homeworld

I freely admit having only skimmed the system in Space, but as a general GM-ing rule, why would you roll the dice for something if you have a result already in mind?

The human homeworld is clearly an important part of the setting and in the setting, it wasn't determined randomly, but happened to be the one world where certain very specific conditions were favourable to humans. It would seem to me logical if you would simply assign it those conditions and extend the rest of the model according to that.
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Old 03-04-2013, 04:51 AM   #7
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Default Re: [Space] Gravity for Human Homeworld

Interesting point, Icelander, I'll try and keep that in mind for next time.

I didn't actually have the Outcome predetermined, I just knew that keeping that result wouldn't end well. I've set the Gravity to 0.81 G and any characters will have a home Gravity of 1G (their Human)

Now for those interested, here is the completed planet

Step 1
Ishichi
The home-world of humanity is this setting. Is TL 7 for aerospace but lower for everything else. 100 years after observing moons around the systems gas giants astromiers discovered an inhabitable planet, Newhome, orbiting the Daystar, a somewhat distant companion star of the Sun, from that point on the race to colonise the newly discovered world was on, currently the former Navel powers control the major off-world colonies.

Step 2
Select Standard (Garden) world

Step 3
Atmospheric Pressure: 0.972
Atmospheric Composition: Normal Garden World Atmosphere
Marginal Atmosphere? Roll of 12 for presence, roll of 12 for type (Pollutants)
Atmospheric Mass: Roll of 12, mas of 1.2

Step 4
Hydrographic Percentage: Roll of 2 for 60% with a +5% mod

Step 5
Roll of 8 for result of 5, with a step of 6 thatís 30 added to the base of 250 for 280 Kelvin
Climate type of cool, Temperature Range of 40ļ to 60ļ F
Absorption Factor: 0.88, Greenhouse Factor: 0.16 (These are both likely to change soon)
0.88 X [ 1 + ( 1.2 X 0.16)]= 1.04896 Blackbody Correction
Blackbody Temperature: 266.931 K

Step 6
Density: Roll of 11 for 1.0 modifier of -0.02 for 0.98 total
World Diameter first.
Square Root of (Blackbody Temperature/ Density)[A] is: 16.5084
Minimum Possible diameter is: A X 0.030 = 0.4951[B]
Maximum Possible diameter is: A X 0.065 = 1.0728[C]

Difference [D]= C-B = 0.5776
Roll is 5-2 for 0.3 for multiplier with a +0.01 modifier
Final World Diameter: 0.31 D+ B = 0.6742[E]

Surface Gravity is 0.98 X E= 0.6607[F]
For this setting a low gravity is probably useful, this is very low so instead Gravity will become 0.81 G and Diameter will be re-calculated

Now with Gravity fixed at 0.81 G Diameter needs to be recalculated, .81/.98=.8265[G]
This means that the planetís mass can be calculated, with a value of .5533[H]

Atmospheric pressure can now be calculated

Step 7
A Roll of 8 for RVM yields a value of -1

An atmospheric pressure of 0.972 is Standard, giving a +3 for Affinity, but those Pollutants mean itís Marginal, denying it a further +1
Hydrographic Coverage of 65% yields a +2
Finally the Cool climate is another +2 for a total Habitability of +7

Combined with the RVM of -1 thatís a total of +6

Step 8
This is a Homeworld

Step 9
TL is 7 for aerospace, pretty much 6 for everything else, areas related to space-flight and commerce are better off but. Delayed as well

Step 10
Base Carrying Capacity is: 5 million
Affinity Modifier is: 60
Together with the Diameter this gives a maximum of: 166 Million,
This rather low for the described society, so the actual population is likely in the 200 million range, supported by a mixture of more advanced then normal technology and off-world imports
PR: 8

Step 11
The world is Factionalized, split into several different countries

Step 12
The common CR is 3, with a single crumbling CR 2 state

Step 13
Base per-capita Income: $19,000
Thereís a -10% for the low Affinity Score, but the presence of some higher technologies offset this for a net of 0%
Final per-capita Income: $19,000
Typical Wealth Level is Average
Economic Volume: 3.8 X 1012

Step 14
There are several Class II Spaceports, one for each major Nation or group of Nations
Most other facilities are present, often more then one per Nation
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Old 03-04-2013, 05:16 AM   #8
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Default Re: [Space] Gravity for Human Homeworld

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Originally Posted by scc View Post
Interesting point, Icelander, I'll try and keep that in mind for next time.
There is a natural temptation to roll for stuff if there is a system for doing that. This is often beneficial, in that one might have the imagination stimulated. However, while real life might be randomly generated, the powers that be there have the luxury of rolling an infinite number of times. Most GMs don't.

If one is rolling for something specific, such as a world someone elected to colonise or where a given race originated, one already has some data in mind. That is to say, unlike the vast majority of planets in the world, this one is salubrious. In the case of original homeworld, it's very possible that the specific mix of conditions that have to exist for intelligent mammalian lifeforms is so rare as to occur only once in several billion random cases. If so, I wouldn't want to have to roll them all up and discard the unsuitable ones. Much better to insert the values one already knows have to be in place and adjust the rest of the model according to that.

Outside of the Space model, this is analogous to games with random generation for characters. If I've already established an NPC as being massively strong, charismatic and the leader of a warlike people who select their rulers by duels, it wouldn't make sense to roll Attributes for him purely randomly. Better assign what I know and roll for the rest.

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Originally Posted by scc View Post
I didn't actually have the Outcome predetermined, I just knew that keeping that result wouldn't end well. I've set the Gravity to 0.81 G and any characters will have a home Gravity of 1G (their Human)
Sounds good enough for government work. I wasn't trying to suggest it as a negative thing that you had an outcome predetermined. Just that merely by declaring the world a human homeworld, a lot of the detail about conditions there was implied. They'd have to be congenial to human life, after all, and most worlds aren't.
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Last edited by Icelander; 03-04-2013 at 05:19 AM.
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Old 03-04-2013, 09:26 AM   #9
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Default Re: [Space] Gravity for Human Homeworld

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Originally Posted by scc View Post
How much early sci-fi brought up the subject of varying gravity on human worlds? Especially as more then fluff piece
Starting with John Carter and Barsoom? Rather a lot of it. The gravities of the rest of the Solar System were one of the few pieces of available data.

I see you've made a sensible decsion so I'll spare you the long monograph on Golden age SF.
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