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Old 12-03-2010, 06:15 PM   #1
terranstrider
 
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Default [Spaceships] Radiation protection question

I recently read "Cold Horizon" an excellent article by Mark Gellis in Pyramid 3/18 about space habitats in the Kuiper Belt. The sample colony is a 3 million ton space station in "GURPS Spaceships" format. It is 60% armour dDR 280:

Quote:
With 60% of its mass consisting of steel shielding, it can protect unmodified human beings from cosmic radiation indefinitely.
This triggered the question; are all the players going to die of cancer? My campaign is TL10^ / early TL11^ with wormhole jumpships, no "miracle" medical tech and no nano tech (microbots only).

Freighter crews spend 50+% of their working lives in space. Thin skinned light warships are often on 3 month deployments in deep space. Exploration ships may spend a year or more in deep space.

My question is: how much armour / radiation shielding is required for starship crews who spend a lot of time in space?

What is a realistic solution to provide radiation protection for the crew of a 3,000 ton tramp freighter with <10 dDR armour?

Thanks.
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Old 12-03-2010, 06:28 PM   #2
munin
 
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Default Re: [Spaceships] Radiation protection question

GURPS Spaceships 5 provides information about radiation hazards. It's not just armor which provides protection, occupied systems are assumed to take advantage of the mass of any systems not primarily empty space (so armor systems, factory systems, fuel tank systems, etc. all provide PF against radiation because they're all mass that will intercept it). Cosmic radiation is 1 rad per week (doubled 75+ AU from the sun), but divides PF by 100.

An SM+9 spacecraft is likely to provide PF 150-250, which won't slow cosmic radiation too much.

Last edited by munin; 12-03-2010 at 06:36 PM.
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Old 12-03-2010, 06:40 PM   #3
Fred Brackin
 
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Default Re: [Spaceships] Radiation protection question

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Originally Posted by terranstrider View Post
This triggered the question; are all the players going to die of cancer?.
Yep.

You could call it a bad mix of realism and optimism if you wanted but your assumptions are incompatible.

The last hope might be Radiation Damahge Repair gene therapy from Bio-tech p.182. That might be sufficiently non-nano for you. It's an $80,000 treatment though any you'll need it at least once per year.

You're going to need miracle rad shielding, advanced medicine or a non-realistic treatment of radiation i.e. ignore the problem.
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Old 12-03-2010, 06:52 PM   #4
lexington
 
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Default Re: [Spaceships] Radiation protection question

Quote:
Originally Posted by terranstrider View Post
I recently read "Cold Horizon" an excellent article by Mark Gellis in Pyramid 3/18 about space habitats in the Kuiper Belt. The sample colony is a 3 million ton space station in "GURPS Spaceships" format. It is 60% armour dDR 280:



This triggered the question; are all the players going to die of cancer? My campaign is TL10^ / early TL11^ with wormhole jumpships, no "miracle" medical tech and no nano tech (microbots only).

Freighter crews spend 50+% of their working lives in space. Thin skinned light warships are often on 3 month deployments in deep space. Exploration ships may spend a year or more in deep space.

My question is: how much armour / radiation shielding is required for starship crews who spend a lot of time in space?

What is a realistic solution to provide radiation protection for the crew of a 3,000 ton tramp freighter with <10 dDR armour?

Thanks.
If they're fighting in thin skinned warships it's not the cancer that's going to get them.

Still, GURPS doesn't consider anti-rad medicine to be superscience. It shows up at TL9 (B436) to start extending their longevity make a TL 10 or 11 version that gives an even larger bonus. But as a general rule, yes, without massive shielding, natural immunity to radiation something to repair the damage they will have drastically shortened lives. But it might take a while, cosmic rays only give one rad/week so unless they get caught in a flare or hang out in a planet's radiation belt or get blasted with antiparticle beams they'll survive campaigns that don't last for years.
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Old 12-03-2010, 07:00 PM   #5
Anthony
 
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Default Re: [Spaceships] Radiation protection question

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Originally Posted by terranstrider View Post
This triggered the question; are all the players going to die of cancer?
Probably not; based on estimates for lifespan reduction for low level radiation exposures, it's an average of about a year knocked off of the lifespan of a spacer, which is significant but less dangerous than cigarette smoking.
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Old 12-03-2010, 07:49 PM   #6
munin
 
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Default Re: [Spaceships] Radiation protection question

You're going to have a Control Room and Engine Room which need to be manned, and a Habitat for off-hours. In terms of what needs to be protected, based on how much person-time will be spent in them, I'd say Habitat first, then Control Room (6 stations), then Engine Room (2 workspaces).

Make sure your Habitat and Control Rooms are core systems in hull sections with no other "empty-space" systems (Cargo Bay, Habitat, Hangar Bay, and Open Space systems). For an SM+9 spacecraft core system with six other mass-shielding systems in the same hull section, this will give PF 900 -- dropping cosmic ray exposure to 1 rad every 63 days.

There's no core slot left for the Engine Room, so at best it will be non-core protected by five systems: PF 350 will be 1 rad every 24 days. An 8-hour shift per day, averaged with the Habitat exposure, is 1 rad every 41 days. So if you keep deployments under 410 days, accumulated dosage will stay in the 1-10 rads category (no effects on a successful HT roll, p. B436).

10% of your accumulated dosage never goes away. I'm not sure how that works with doses under 10 rads. There's no mention of how to round these things, so I think you round down (like you would for inflicted damage, p. B9), so a dose under 10 rads will go away in a little over a month once you return to base.

That's a best-case design. You may want to do a more detailed analysis depending on your specific ship design and behavior (for example, if people will be spending a lot of time in hangar bays or cargo holds, which are protected only by armor systems). Semi-worst case, someone who spends 8 hours per day in a hangar bay with no armor systems protecting it, and 16 hours per day in the protected core Habitat, will take 1 rad every 17 days, so missions would need to stay under 170 days (long enough for a 3-month deployment, but not for the year-long deployment).

EDIT: Since radiation heals at 10 rads per day after 30 days, all that may be necessary to handle cosmic rays is to get enough PF to reduce your exposure rate to less than 1 rad per month, which requires a PF of 400+. That is possible on an SM+9 ship, with 2/3 of crew time spent in core systems protected by mass-shielding systems, and the rest of the time spent in systems with some shielding.

Last edited by munin; 12-03-2010 at 10:59 PM.
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Old 12-03-2010, 08:10 PM   #7
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Default Re: [Spaceships] Radiation protection question

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Originally Posted by terranstrider View Post
This triggered the question; are all the players going to die of cancer?
As Anthony said, no. But let me go into more detail.

We know very little about the medical effects of long term low dose radiation exposure. If the radiation is all delivered in a short time faster than the cellular repair processes can kick in, we have a good idea of what happens. But when you try to extend this theory to very low dose rates, it might not work. Or it might work. The problem is that you are dealing with a very small number of events (i.e., deaths from cancer that are caused by the excess radiation), so you need very large trials and robust statistical analysis which makes the research difficult. The model that is currently used is the linear no threshold model. It is probably a conservative model, in that it will over-predict the number of cancers due to radiation exposure. But since we do not have anything better it is what we tend to use when setting policy because in this case you might as well play it safe. This leads to things like long stays in space increasing the occupational dose of astronauts beyond the OSHA limit, when the space residents would probably be fine. No worries, we have plenty of astronauts and the ones who are grounded get to make way for younger recruits and then go write books or give lecture tours or something. So we stay cautious. But for a game you could easily justify people being able to tolerate the dose rates of galactic cosmic radiation beyond the atmosphere and beyond earth's magnetosphere without any adverse health effects. Heck, one of my nuclear physics professors thought that radiation actually had certain beneficial health properties (the lesson I learned - don't go to a physicist for medical advice).

Now solar storms and CMEs and the radiation belts of large gas giants will deliver doses large enough to cause acute radiation poisoning, often of a lethal nature. Fortunately, these low energy particles are much easier to shield against. It appears that you can set up an artificial magnetosphere around a spacecraft, for example, on a relatively low mass budget that will block everything except for the galactic cosmic rays (and uncharged radiation such as gamma rays and neutrons - but you usually don't encounter these naturally. You do encounter them as a result of human activity - reactors and nukes and the like).

Luke
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Old 12-04-2010, 03:12 AM   #8
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Default Re: [Spaceships] Radiation protection question

In my settings, I allow a combination of Genetic Modifications and Mini-magneto-spheres to aleviate the radiation threat.

Slow Regeneration (Radiation Only) is only 4 points, and couples very well with the "No Degeneration in Zero-G" perk fo a total of 5 points. This means that as long as the exposure is less than 5/6 a rad per hour, you'll be ok... that negates cosmic radiation as a threat, and with a decent hull PF, makes solar flares bearable.

I also use a Perk: "Heals All Radiation Damage", which simply allows the 10% "permanent" damage to be healed at normal rate.

--------------

A Magnetosphere device could also aid in shielding radiation hazard, and a plasma saill would function as the same. I wing the rules allowing any plasma sail to be treated as a force screen providing PF equal to the DR of a similar sized TL11 force screen if TL9, or TL12 screen if TL10+... a magnetosphere doesn't operate as a sail, but has twice the PF (like a Heavy Screen), but still only uses 1 PP to activate (but not maintain).

Last edited by Trachmyr; 12-04-2010 at 03:16 AM.
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Old 12-04-2010, 07:50 AM   #9
vicky_molokh
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Default Re: [Spaceships] Radiation protection question

I always felt that GURPS is very, very harsh when it comes to frequent low doses of rads, like cosmic rays, due to rolling every several days - there's just bound to be a critfail in a year, which results in rad burns and much worse from a negligible dose.
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Old 12-04-2010, 11:30 AM   #10
lwcamp
 
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Default Re: [Spaceships] Radiation protection question

Quote:
Originally Posted by Trachmyr View Post
A Magnetosphere device could also aid in shielding radiation hazard, and a plasma saill would function as the same. I wing the rules allowing any plasma sail to be treated as a force screen providing PF equal to the DR of a similar sized TL11 force screen if TL9, or TL12 screen if TL10+... a magnetosphere doesn't operate as a sail, but has twice the PF (like a Heavy Screen), but still only uses 1 PP to activate (but not maintain).
In real life, an artificial magnetosphere would allow you to essentially stop all radiation from solar storms and planetary radiation belts. However, it would only stop the lower energy galactic cosmic rays and allow the higher energy rays right through. It also would do nothing at all against gamma rays or neutrons. I am not entirely sure how to handle that using the GURPS PF mechanism.

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