The Expanse High G space travel in GURPS?

[Maz]

In the setting of The Expanse limitation on how fast you can go in your space ship is not just based on motor power but also the ability to be able to withstand the high G's of fast acceleration.

In the Expanse Roleplaying Game (From Green Ronin) it has travel time listed based not on speed of space craft but on the G's. So it goes from traveling at 0.3 G up to 12 G.

The only rules in Basic I could find for how to handle G's is on p.434. It says if you experience a sudden acceleration you roll at a penalty. However there are no rules for being under a high G-force for an extended period of time. Which is specifically a plot point many times in The Expanse.

Also even 7 G is noted as "a lot" in The Expanse but in GURPS that would just be a -3 HT penalty. Sitting down gives you +2 so most typical GURPS PC 's would have little trouble passing such a roll. (For typical adventuring PC's, I think it's rare to see below effective HT of 12)



Are there more detailed rules in any other GURPS books, Space perhaps?
If not, how often would you have people make the HT-rolls for extended G-force traveling?

[ravenfish]

Gurps:Spaceships pp.38-40 has guidelines for converting from known acceleration to distance traveled/time taken, if you don't feel like working out the math from first principles. There's no general rules in there for how uncomfortable it is to be on a rapidly accelerating ship, as far as I can tell, but it is mentioned in passing that ordinary humans won't be able to move around without assistance at 3+G of acceleration (p.63) and that rapid course adjustment, as per a dodge, could cause unsecured passengers to take damage as per a fall of 10 yards * G of acceleration (p.64).

[Maz]

Originally Posted by ravenfish

Gurps:Spaceships pp.38-40 has guidelines for converting from known acceleration to distance traveled/time taken, if you don't feel like working out the math from first principles.

I don't actually need distance/travel time. I got the Expanse RPG and it has some handy tables for it. However I would prefer to use GURPS for the everything else. And I need some rules for handling the high G experienced by fast space travel. And those rules have to be dramatic and fit the setting.

The one's in basic seem fine, but I need to know how they work for extended exposure to high G.

[ericthered]

Originally Posted by Maz

The only rules in Basic I could find for how to handle G's is on p.434. It says if you experience a sudden acceleration you roll at a penalty. However there are no rules for being under a high G-force for an extended period of time. Which is specifically a plot point many times in The Expanse.

Also even 7 G is noted as "a lot" in The Expanse but in GURPS that would just be a -3 HT penalty. Sitting down gives you +2 so most typical GURPS PC 's would have little trouble passing such a roll. (For typical adventuring PC's, I think it's rare to see below effective HT of 12)

The rate at which the HT penalty builds up is pretty slow, I'll say that. I wouldn't blame you for coming up with an alternate progression, or adding a blanket -2 to all the rolls.



I do not find that most my players tend to have high HT scores, especially across the board, and I'm fine with that. I find that HT is most interesting at 9 to 11, and scores above that give performances drastically above the typical human.



What is the expected behavior? Do people always eventually pass out? Or are some able to function at those high G's?


If they always eventually pass out, using margin of success to time how long you have is one option. If some people are able to function, you could just add +2 to rolls to stay conscious if the acceleration is sustained.

[Fred Brackin]

Originally Posted by Maz

The one's in basic seem fine, but I need to know how they work for extended exposure to high G.

The Gurps rules for Acceleration effects have been redone several times. Usually with the result of making them, more generic but less realistic. Real world fighter pilots used to need a special Advantage like Resistant to G-Forces. Now they don't even roll until they try a 9G turning maneuver.

From my memory (and possibly from Space 1e) characters in g-seats roll for prolonged acceleration effects as if the G-force was 3 Gs lower. With current rules that would mean you didn't even roll at 11 Gs and that's hooey.

If characters are up and working you figure their extra weight as Encumbrance and charge the FP as if Hiking. A ST 10 character can't even walk if his extra weight plus carried gear at its' current weight goes over 200 lbs.

I don't find the current rules very satisfactory but I think I know where my copy of Space 1e is. :)

[Maz]

Originally Posted by ericthered

What is the expected behavior? Do people always eventually pass out? Or are some able to function at those high G's?

At the high G-levels. Yes they all eventually pass out.

The scenes from the TV-series I would like for the rules to be able to mimic is:

Traveling very fast you need to strap down and be injected with a specific "high G juice" that help your body withstand the high G. Not using it results in passing out. Even injecting will make people pass out after minutes, when traveling at "fastest speed".
[This is seen often in the series. I I like it as a dramatic effect. "Do you press on, pushing yourself and the others for added speed, or do you play it safe but waste travel time"]

Traveling, really, really fast might even kill you.
[Again seen in the series, especially in a scene where one passenger does not have the same toughness as the others so they have to choose between going fast, maybe/likely killing that person or slowing down, but then not reaching the target before "the plot".]

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So what I would like are some rules similar to p.434. But maybe with a slightly higher penalty and then having to make the HT rolls at a specific interval. From "once per hour" for only slightly faster, to "once per minute" for very high G's.

Loosing Fatigue based on degree of failure is fitting (as it can also lead to HP loss if you have lost all FP).

I don't really mind making my own. I just wondered if there were some already made to make it easier :)

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In general. I really lack a general rule in GURPS to switch between "having to roll very often at low penalty" to "having to roll less often but at a higher penalty". But that's a different topic so I will make a new thread for that.

[whswhs]

Have you read "Different Gravity" on p. B330?

For a normal person, a G-increment is 0.2 G. So being at 3G would be 10 G-increments. That gives you -5 HT and lowers your FP by 5. At 5G, it's -10 HT and FP reduced by 10. It's not explicitly stated, but I think a character with 10 FP, whose FP was reduced to 0, might be unable to do anything that takes significant effort.

[Maz]

Originally Posted by whswhs

Have you read "Different Gravity" on p. B330? [edit: B350]

For a normal person, a G-increment is 0.2 G. So being at 3G would be 10 G-increments. That gives you -5 HT and lowers your FP by 5. At 5G, it's -10 HT and FP reduced by 10. It's not explicitly stated, but I think a character with 10 FP, whose FP was reduced to 0, might be unable to do anything that takes significant effort.

Hmm, no I hadn't really taken those into account. Thanks!
I could do that, that would certainly overcome the "problem" of high HT character being immune to high G.

[Rupert]

Originally Posted by whswhs

Have you read "Different Gravity" on p. B330?

For a normal person, a G-increment is 0.2 G. So being at 5G would be 10 G-increments. That gives you -5 HT and lowers your FP by 5. At 5G, it's -10 HT and FP reduced by 10. It's not explicitly stated, but I think a character with 10 FP, whose FP was reduced to 0, might be unable to do anything that takes significant effort.

Well, at 0FP B426 says doing more than talking or resting requires a Will check, with failure resulting in collapse. So at 3G the average person can sit in an acceleration couch and watch the console lights blink, but if something goes wrong there's a 50/50 chance they'll be unable to effectively react to it.

As they are also at -20 to DX tasks (-10 if they have G-Experience at 5G) and -10 to IQ tasks, whatever they're trying to do had better be dead-simple. Even the bunch of near unto superhuman PCs in my SF game would be fazed by these penalties (though a fight in these conditions would solidify their love for lasers, which don't take DX penalties for gravity).

That last point makes me think that maybe even skills like Lockpicking and Beam Weapons should take half penalties (rounded down), and thus with G-experience for 5Gs they'd only take a -5. Still clearly superior to using a projectile weapon, but not nothing.

[Rupert]

Originally Posted by Fred Brackin

I don't find the current rules very satisfactory but I think I know where my copy of Space 1e is. :)

I think they're quite adequate, and they still penalise overweight characters and encourage skinny people. They also still punish characters that are not Overweight or Fat but are simply heavy for their weight. If your campaign sees high gravity much, you 'should' make your character as light for their ST as the GM will allow.