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Old 10-02-2022, 11:27 AM   #1
johndallman
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Default [Basic] Advantage of the Week: Pressure Support and Vacuum Support

Pressure Support [5, 10 or 15] is an exotic physical advantage. You are capable of withstanding pressures much higher than that of your native environment: how much higher depends on how much you’ve paid for the advantage. This advantage first appeared in GURPS Aliens for 3e.

Vacuum Support [5] is likewise an exotic physical advantage, which protects you from the effects of low pressure, vacuum and decompression. It also first appeared in GURPS Aliens for 3e, but the 4e version is substantially cut down from 3e, requiring the use of other advantages to get the same abilities.

Pressure Support protects you from ambient pressure. It does not reduce or prevent damage from crushing attacks or explosions. It does protect you from exotic attacks that manipulate ambient pressure, or try to crush you as a whole. It lets you maintain a constant internal pressure irrespective of outside pressure, within the limits of what you’ve bought. Characters with this advantage may well have the Sealed advantage, but this is not required.

Vacuum Support protects you from the bad effects of vacuum and “decompression.” The latter seems to be protection from pressure loss taking you down from your normal pressure to vacuum, or a very thin atmosphere. Claiming that it protects you from “decompression sickness” aka “the bends,” where you suffer problems from the ambient pressure reducing from much higher than your native pressure, is not supported by “Vacuum” on p. B437. Characters with this advantage usually have Sealed, and may well have Temperature Tolerance and/or Radiation Tolerance, but none of those advantages are mandatory.

The first level of Pressure Support [5] protects you from pressures up to ten times your native pressure. For [10], you get protection from up to 100 times your native pressure. At [15], you’re protected from any pressure.

Humans with SCUBA gear can adapt readily to pressures up to about three atmospheres: the breathing apparatus supplies air at ambient pressure, and higher pressures cause problems because of the effects of breathing nitrogen and oxygen under high pressure, not because of the pressure itself. With different gas mixtures, pressures of 50 atmospheres can be reached, although this is complicated and very dangerous if things go wrong, and “decompressing” from high pressure takes considerable time. An atmospheric diving suit provides Pressure Support 2 as per the advantage, maintaining a sea-level atmosphere inside an extremely strong, heavy and bulky suit. Surprisingly, these aren’t in High-Tech.

Several “Body of ...” meta-traits include Pressure Support, and it’s standard issue on templates for aquatic characters, Elder Things, elementals, golems and many robots; some of those creatures (and some undead) also have Vacuum Support. Page B.435 has helpful advice on how to be killed by high and low pressures. Banestorm has guidance on the amount of Pressure Support required by aquatic characters, and suggests that creatures who live in ocean depths might need Vacuum Support to reach the surface. Bio-Tech provides TLs for both of these advantages as biomods, and Magic has a single spell that provides either, although the cost depends on just what you take, and the spell is also provided in Sorcery: Protection and Warning spells.

Power-Ups 4 allows the Force Field enhancement for both advantages and Power-Ups 8 allows them to take the Active Defense limitation, which I would not allow. Supers shows us how to build equivalent abilities out of other advantages, and Template Toolkit 2: Races has modernised versions of many meta-traits. Transhuman Space: Changing Times has additional detail for diving, and Ultra-Tech extends Pressure Support to equipment. Underground Adventures deals with pressure in deep caves, and creatures from the Earth’s outer core.

I’ve never used either of these advantages as a character trait, although I’ve played space and submarine adventures where they were provided as equipment. Have they shown up in your games?
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Old 10-02-2022, 06:12 PM   #2
Pursuivant
 
Join Date: Apr 2005
Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

Vacuum Support and Pressure Support are critical when designing non-human species which can easily cope with higher or lower pressures.

One obvious problem with Vacuum Support is that it doesn't allow partial levels, nor the option to "compress" available atmosphere to make it more breathable, like an ultratech compressing respirator. IIRC, there is a "hard" sealed diving suit in GURPS High Tech, but it might be out of date.

Vacuum Support that only works for Thin Atmospheres (treating the local pressure as one level higher, up to a maximum of Average) might be worth 1 point (i.e., a -80% limitation) and could be a Perk. Perhaps a -60% limitation for the advantage to work in Thin or Very Thin atmospheres but not hard vacuum, or -40% if "trace" atmosphere is treated as Very Thin.

Add suitable gadget limitations if your power depends on some sort of concentrating equipment.

There's also the possibility of a zero point version, which allows Thin atmospheres to be treated as Normal, but Normal atmospheres get treated as Dense. Alternately, Very Thin gets treated as Normal, Thin gets treated as Dense, and Normal gets treated as Very Dense.

Realistically, anything with Pressure Support + Sealed should have a reasonably good DR. A Sealed + Pressure Support character with a limited "crush depth" might have DR with a limitation (Not at extreme pressures), representing decreased ability to withstand damage at high pressures.

If you wanted to get wonky with the points, you could have finer levels of Pressure Support, with each character point up to 5 providing +2 ATM of pressure support, each character point up to 10 providing +18 ATM of pressure support, and each point up to 14 providing +100^(n-9) ATM (1,000 ATM at 11, 10,000 at 12, etc.). (Edit: GULLIVER used x2, x3, x5, x7, x10, x20, x30, x50, x70, x100, progression for levels 1-10, which is a bit more elegant.)

As an enhancement, the ability to reduce the local pressure level with respect to your body might be worth +50%. Environmental (Liquid or Gas only) would be a -40% limitation, suitable for things like cetaceans or gas-giant dwellers, especially if they're not Sealed.

Last edited by Pursuivant; 10-02-2022 at 06:36 PM.
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Old 10-03-2022, 10:54 AM   #3
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

This is one of those places where fudged or under-considered features were grandfathered into 4th edition, and the system could do with a bit of a re-write - except that it's hardly worth the effort in practice.

(When statting up your notKryptonian super, just define their native pressure as a million billion atmospheres, and then take Vacuum Support. Much cheaper than taking Pressure Support.)
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Old 10-03-2022, 11:23 AM   #4
ericthered
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

I occasionally stick these traits on templates and characters: its generally very obvious when they should have them. Vacuum support comes up a lot more often than pressure support. Its hard enough to play a game in the water, let alone worry about pressure from depth. Folks and creatures who can operate in hard space show up decently often in my games though.


One interesting discovery I made a while back is that most robots/computers shouldn't have vaccuum support, because they rely on air to cool their chips and will quickly fry their brains in a vacuum.
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Old 10-03-2022, 03:56 PM   #5
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

Quote:
Originally Posted by Phil Masters View Post
This is one of those places where fudged or under-considered features were grandfathered into 4th edition, and the system could do with a bit of a re-write - except that it's hardly worth the effort in practice.
Agreed. I've tinkered in my house notes with a rewrite of pressure, gravity, and temperature, giving all three a similar range of "intolerance" or "tolerance" -- and threw in a hack at radiation tolerance at the time because why not.

But it sure as heck ain't play-tested.
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Old 10-03-2022, 04:13 PM   #6
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

Quote:
Originally Posted by Phil Masters View Post
(When statting up your notKryptonian super, just define their native pressure as a million billion atmospheres, and then take Vacuum Support. Much cheaper than taking Pressure Support.)
Cute, but that trick doesn't work for a super from an Earth-like planet - which mere mortals can visit without getting squashed into jelly - who also has the ability to visit the earth's core unprotected. It's legitimate for aliens native to a gas giant or the earth's mantle, however.
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Old 10-03-2022, 05:20 PM   #7
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

A core problem with most life-support type abilities is that GMs either don't put plot-important things in locations where life support is available, or make sure that the PCs can all get there -- i.e. they are "go places there's no reason to go" or "avoid the plot segment where you acquire the tools to get to hard to reach places". Neither is terribly valuable.
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Old 10-03-2022, 11:36 PM   #8
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

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Originally Posted by johndallman View Post
I’ve never used either of these advantages as a character trait, although I’ve played space and submarine adventures where they were provided as equipment. Have they shown up in your games?
They've turned up in my game as advantages a high-end android had, along with sealed, etc. They proved useful she she fell out of a boat (she was far too dense to swim) and ended up having to walk along the bottom of the lake to get to shore.
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Old 10-16-2022, 05:26 AM   #9
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

Quote:
Originally Posted by Anthony View Post
A core problem with most life-support type abilities is that GMs either don't put plot-important things in locations where life support is available, or make sure that the PCs can all get there -- i.e. they are "go places there's no reason to go" or "avoid the plot segment where you acquire the tools to get to hard to reach places". Neither is terribly valuable.
I would very much second this, I have had a couple of characters with vacuum support (every so often I go through a phase of cyborg or augmented characters).

While it seems fairly priced for what it does I can't see me taking it again without some sort of serious limitation because despite playing a fair number of these characters I have used it a grand total of once (ok that one time it literally saved the character and most of the party) and then only in highly atypical and entirely player created circumstances.
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Old 10-16-2022, 06:21 AM   #10
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Default Re: [Basic] Advantage of the Week: Pressure Support and Vacuum Support

Quote:
Originally Posted by Anthony View Post
A core problem with most life-support type abilities is that GMs either don't put plot-important things in locations where life support is available, or make sure that the PCs can all get there -- i.e. they are "go places there's no reason to go" or "avoid the plot segment where you acquire the tools to get to hard to reach places". Neither is terribly valuable.
This is a problem not just with life support but all kinds of abilities that let characters go somewhere different. It has really stood out since the introduction of cyberspace to gaming - where the alternate realm is pretty core to the game theme, but it comes up all over the place from fantasy races that can't get too far from their grave/home tree, to how much modern characters can afford to pay for travel tickets. When you have restrictions like this, either nobody can go there - the game can't involve those locations, everybody can - in which case there isn't anything "special" about them anymore, or you are stuck with a situation where some of the party can't participate in part of the adventure, or arguably worse, the ability counts as an unfair tax on the one player who took it with Affects Others to bring the party along - essentially the "Owns the Starship" problem.

Making the abilities cheap at least lets you use the location, by either pushing you toward either everybody has it, or making the tax for taking the Affects Others version less crippling.
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