Gravity on planets

[JNJ]

Hi,

It appears to me that gravity effects are well enough detailed in the rules but I am not sure this is well reflected in the adventures.

For example, Walston where is located High and Dry is Size 5 and has a surface Gravity of 0.45G

Let's say that the ship bringing the travellers there put a local 0.45G during the Jump so a part of them will be already accustomed and won't suffer any side effect. Others won't be for weeks (core rules)

Even if all are, the local gravity will have important effects during the climb to the mountain summit, even more if someone falls, and even on the way the volcano eruption disperses in the air.

This doesn't seem to be taken in account. On the contrary local Atmosphere effects are explained, and possible effects taken in account in details.
It seems the same for all adventures in any edition of Traveller. Maybe I am wrong.

How do you handle it ? Do you care about it or don't consider it at all ?
In my opinion it is a great tool for adding a "reality" feeling to each planet they travel too, and many role playing opportunities.

 

[Arkathan]

I handle it the same way Star Wars handled it on the asteroid when they were inside the worm.
There is either gravity or there isn't, and their gear will compensate... or it won't...

 

[phavoc]

Half the gravity means roughly half the effects. Usually it's just the details missing (not uncommon). Most won't do much with all the related effects of things other than the very basic - you can carry roughly twice your normal weight and falling effects can be reduced in some instances.

 

[Condottiere]

My rule of thumb is that seventy to one hundred forty percent Terran norm is tolerable to most default humans.

Step outside that range, and it's time to look up the charts.

 

[Bryn the 2300AD guy]

Humans can survive about 1.5 G and start adapting. This is fine, because rocky worlds with greater than ca. 1.35 G will become gas giants unless very close to the star, in which case they're BBQ. Similarly, worlds with less than about 0.5 G don't have enough gravity to retain oxygen in the atmosphere. This places a workable range for garden planets of between about 0.5 and 1.35 G.

Whilst Humans suffer muscle and bone wastage at lower G than they're used to, short exposures have no more effect than sitting on the couch.

 

[TrippyHippy]

Time passes at a slower rate on high gravity planets. Not sure how to work this into the rules, but might be worth noting. Also, I’d possibly be asking for more Strength and Endurance tests to move about.

 

[Sigtrygg]

I don't think the microseconds/day difference will matter much in general life but it will add up over... time

And Dex, a simple trip and you are falling towards the ground much faster than your reflexes are used to.

 

[CordwainerFish]

Time passes at a slower rate on high gravity planets.

Not perceptibly so.

 

[Gavain]

I wonder why we use 1g as the standard for gravity in Traveller? This is the distribution of planet sizes in the Trojan Reach showing the most frequent size is 5 (0.45g). Only 25 out of 327 have size 8 (1.0g). In my game I use the Companion rules on gravity where you get a DM -1 for each 0.25g difference between actual gravity and your current adapted gravity.
I tend to think that all space stations would be at a gravity more consistent with the sector than consistent with an arbitrary planet most of humanity have never heard of. That value in my game is 0.8g, higher than average because mistakes from mall adaption are less painful in low g than high g. But in general I gloss over the differences unless there is an in game reason to apply any penalties.

 

[Sigtrygg]

This is a rabbit hole...

300,000 years ago humans from Earth (1g) were transported to other worlds, Vland (1.15g) and Zhdant (0.8g) and a few others. The Vilani should be shorter, stronger and have higher Dex than Terrans. The Zhodani should be taller, and likely not as strong etc.

 

[Condottiere]

Maybe when they were prototying their respective manoeuvre drives, they came to the conclusion that what passes for Terran norm is a universal constant (at least in the tech tree).

 

[JNJ]

View attachment 1079
I wonder why we use 1g as the standard for gravity in Traveller? This is the distribution of planet sizes in the Trojan Reach showing the most frequent size is 5 (0.45g). Only 25 out of 327 have size 8 (1.0g). In my game I use the Companion rules on gravity where you get a DM -1 for each 0.25g difference between actual gravity and your current adapted gravity.
I tend to think that all space stations would be at a gravity more consistent with the sector than consistent with an arbitrary planet most of humanity have never heard of. That value in my game is 0.8g, higher than average because mistakes from mall adaption are less painful in low g than high g. But in general I gloss over the differences unless there is an in game reason to apply any penalties.

Thanks for the data, and thanks all for your answers.
I agree with your conclusion Gavain and manage it nearly the same.

IIRW the official answer for the 1G standard is that from TL10-12 onward people live in cities able to afford gravitic plates. This allows people to live and travel from 1 planet to the other while keeping the same gravity.
Highports, downports maybe ? and Imperial navy also use the 1G standard I think.
That said, not very pratcical when you exit the cities ... on a planet with a different gravity.

The Traveller 2300 last version seems to accord more importance to gravity (being lower TL), using it also for character background and creation. I imported a part of it, mixed with Traveller companion rules and added rules from T20 (not sure ?) for PC's height and weight modified by homeworld gravity.

According to me using gravity rules while jumping from a system to another adds flavour and role playing opportunities. Another way to make each planet more unique ... The distance a bullet can go on a low gravity planet is always an interesting "1st encounter" for new players

 

[Condottiere]

Outside being capped at technological level nine, once the Vilani spend a great deal of time accelerating naked at one gee, they may feel that's the optimum pressure they can operate under.

 

[Sigtrygg]

Why would the Vilani cap their drives at 1g instead of the 1.15g or some fraction of it that they are used to?

 

[Bill Sheil]

... Size 5 and has a surface Gravity of 0.45G

Just checked the World Generation rules and it it looks like all the gravity values given are wrong and not even in the correct range of values. They should all be linearly proportional to the radius of the planets for worlds with the same density (as the book states is an assumption). A size 5 (terra density) world should have a surface gravity averaging 0.625G.

Surface Gravity is proportional to the mass of the planet divided by the radius squared. Mass is proportional to radius cubed (multiplied by density). Therefore Surface Gravity is proportional to density x radius. So a size 4 world should have a base gravity of 0.5G and a size 6 world should have a base gravity of 0.75G for example.

The values give seem to assume that density is increasing with radius/world size (true for mars, for example) but that is contradictory to the statement: "The values for gravity in the Size table assume that the world has a density similar to that of Earth."

This error goes back to 1st edition Mongoose and is inconsistent with T5 which gets the numbers right on the same assumption.

 

[Condottiere]

Does rotational speed play a factor?

 

[Condottiere]

Why would the Vilani cap their drives at 1g instead of the 1.15g or some fraction of it that they are used to?

If they were stuck at technological level nine for a while, and weren't inclined to install inertial compensators or gravitational plates, on cost grounds.

Rocket thrust only gets you that far.

 

[Bill Sheil]

Does rotational speed play a factor?

To any detectable degree no.

 

[Bryn the 2300AD guy]

To get a size-5 world down to 0.45 G, density must be 0.7 of Earth. It would have an atmospheric pressure of 0.49 atm, and a MMWR of 25; so it is close to not being able to retain O2 (MW = 32) and N2 (MW = 28). Pretty close to not capable of having a breathable atmosphere.

A size-4 world of that density could not maintain a breathable atmosphere.

At density = 1 Earth, a size-4 world could not maintain a breathable atmosphere, and a size-10 retains helium, but not hydrogen. Any world of that density larger than 10 becomes a gas giant/dwarf.

 

[Bill Sheil]

I am beginning to doubt whether anyone has looked in detail at the Mongoose World Building rules since MgT1e. The TL bonus for balkanisation also strikes me as odd, and is also inconsistent with other (Marc Miller) versions of Traveller. And there is a danger that, with SecondSurvey/TravellerMap becoming canon, Mongoose is publishing sector data that is inconsistent with its own ruleset.

Hopefully @Geir is watching these threads for the World Builder's Handbook.