Gravity

[Peleliu]

So, looking through book 3 on planet generation (T5.10). I can't find anything regarding gravity for worlds. Have I overlooked it or am I looking in the wrong place?

 

[tjoneslo]

Very few of the Traveller world generators include the gravity generating formula. The problem is the density of the material in the world can vary and thereby give different values for gravity

Planetary Size - Traveller

wiki.travellerrpg.com

Has a range of values for each planet size

 

[agorski]

CT Book 1 (1977) pg 33 has a formula for calculating the weight a character can carry based on planet size alone.

T5 Book 3 pg 251 has a gravity table also based on planet size alone.

I'm using that in an app I'm working on right now to calculate encumbrance reductions to characteristics.

 

[coliver988]

CT Book 1 (1977) pg 33 has a formula for calculating the weight a character can carry based on planet size alone.

T5 Book 3 pg 251 has a gravity table also based on planet size alone.

I'm using that in an app I'm working on right now to calculate encumbrance reductions to characteristics.

well, just because they can lift 2x as much does not necessarily mean they can carry 2x as much if those are big things. And inertia still rules

 

[Peleliu]

CT Book 1 (1977) pg 33 has a formula for calculating the weight a character can carry based on planet size alone.

T5 Book 3 pg 251 has a gravity table also based on planet size alone.

I'm using that in an app I'm working on right now to calculate encumbrance reductions to characteristics.

Pg 251? Tucked away in the animal creation section? What an odd organizational choice.



P.S.

I finally found some reference to gravity and density on a page 56 table in the world mapping section. A better place to put it is probably with the system creation rules similar to MegaTraveller's World Builder Handbook.

 

[kilemall]

IIRC world tamer has a gravity/ density range along with what atmosphere composition can be retained due to that gravity.

 

[McPerth]

MT:WHB (page 60) has a formula for gravity...

G=M x (64/R²)

Where G is gravity (in Gs) M is mass (in Earth's) and R is UWP size (0.6 for R)

Example: A UWP size 5 world has a mass of 0.161. Divinding 64 by 5 squared gives 2.56 . Multiplying 2.56 by the mass of 0.161 yelds a surface gravity of 0.41 g.

Not sure if CT Grand Census or Grand Survey (fro mwhere I've heard most info for MT:WHB is taken) also have it...

 

[agorski]

Pg 251? Tucked away in the animal creation section?

With T5 you have to search the PDFs using keywords to find anything!

 

[Timerover51]

It looks like the T5.10 table on page 251 is assuming that the density of the planet is the same as Earth, which is 5.51 grams/cubic centimeter. If you change the density compared to Earth, you change the surface gravity. Mercury is considerably smaller than Mars, but because of its higher density, its surface gravity is the same.

 

[aramis]

Given the same density, the surface gravity scales directly with the diameter.
given the same diameter, gravity scales directly with the density.

So G's at surface = D×S/44 where D is density in g/cc and S is size digit.

And while indeed, Mars gravity is comparable to Mercury, it's Mars that's the outlier for rocky, not Mercury, but ceres and vesta both are light rocky bodies, too.

Planet or Dwarf Planet​	Average Density (gm/cm3)​	Type
Mercury​	5.4​	Rocky Planet
Venus​	5.2​	Rocky Planet
Earth​	5.5​	Rocky Planet
Mars​	3.9​	Rocky Planet
Jupiter​	1.3​	Gas Giant
Saturn​	0.7​	Gas Giant
Uranus​	1.3​	Ice Giant
Neptune​	1.6​	Ice Giant
Ceres​	2.2​	Astroid Belt Dwarf Planet
Pluto​	2.1​	KBO Dwarf Planet
Haumea​	3.0​	KBO Dwarf Planet
Makemake​	1.8​	KBO Dwarf Planet
Eris​	2.5​	KBO Dwarf Planet
Vesta​	3.5​	Asteroid Belt Asteroid

https://starchild.gsfc.nasa.gov/docs/StarChild/teachers/densities.html .
https://spacemath.gsfc.nasa.gov/Pluto/PlutoA.pdf .

 

[mike wightman]

Don't suppose you could add surface gravity and diameter to that table

 

[aramis]

Don't suppose you could add surface gravity and diameter to that table

not with my current level of lazy

 

[Timerover51]

Don't suppose you could add surface gravity and diameter to that table

Here is the information for the planets in metric units.

Planetary Fact Sheet

For English units, which would give a Traveller-style diameter, see the following.

Planetary Fact Sheet - U.S. Units