Sci-Fi Space Station Adventure Help

[Surpriser]

For an upcoming game, I would like to run a sci-fi adventure that has the PCs hopping between asteroids and space stations.

Now, I have the basic situation and story planned out, but it is missing twists and complications that would make the whole thing entertaining.
Also, it currently looks a lot like a railroad-track without many opportunities for meaningful choices.

The PCs are hired to investigate an asteroid mining station that fell silent after a big explosion was registered on the asteroid. When they arrive, they find the asteroid blown apart, with only a small research camp still intact. On site, they find information that the survivors of the accident decided to transfer to a previously unknown space station that appeared in their telescopes, in the hopes of finding help and ships capable of bringing them home (their shuttles on board do not have deep-space capabilities).
When the PCs follow them, they are targetted by the space stations automated defense systems and their ship is damaged (to prevent easy escape). It turns out that the military conducted experiments with mind control on prisoners on the station. When the mining asteroid exploded, the debris damaged quite a few systems, with the result that the current test subject gained mental control of (most of) the crew.
The PCs have to find and disable the prisoner in control (either kill him or shut down the machines he is connected to). After that, they can free the crew and the fugitives from the mining camp (who were thrown into cells on arrival) and use the shuttles in the hangar to get everyone home.

Do you have ideas on how to make the various plot points challenging? I am looking especially at non-combat situations, since I don't have a lot of experience with science fiction settings.

Some ideas I had:
- The prisoner can not leave the machine he is strapped into (or if he did, the crew would regain control) and intends to kill everyone on board by crashing the station into the mining asteroid. This would set a simple timelimit and enable me to use the danger of time running out as an effective way to create suspense.
- I would like to play up the dangerous and unusual environment of space. Therefore any situations/objectives/encounters including space-walks or the dangers of vacuum (try not to pierce the station's hull with a bullet...) would be greatly appreciated.
- If possible, I would like to present multiple possible solutions to each problem, with different costs and/or outcomes.

[The Grue]

Space has lots of fun and terrifying hazards unique to it. How hard are you going on the science? (I presume, given your synopsis mentioned a "shockwave" in space, that the answer is "not very")

Anyway for idea-mining I would suggest the films Gravity, Interstellar, and of course the classic Apollo 13.

[Surpriser]

Right, the term "shockwave" was a bad choice! I corrected it to "debris", which I hope is better suited.
The science should be hard enough that any artistic freedom is not immediately obvious to someone with general knowledge about the topic.
The "shockwave" example would probably pass unnoticed, as would any handwaving about orbital mechanics, gravity wells, warp-drive and similar topics, as long as it is not too extreme.
The goal is to avoid discussions during the game about the realism and any obvious contradictions would surely be pointed out and argued about by my players.

The technology level should be nearish future, interplanetary travel is common and possible within days or weeks (otherwise such a rescue mission would be pointless).

[rs2excelsior]

Space is quite dangerous and hostile. Micrometeor strikes can damage your spaceship (sometimes critically, depending on tech level--they're small, but moving at potentially relative speeds up to hundreds of miles per second). Solar and planetary radiation are a threat, so damaged radiation shields or spacewalks in relatively unprotected spacesuits could provide challenges. Plus there's the threat of getting separated from your ship--it's not like you could walk back. If you're feeling particularly cruel, have a group of miners (or a few groups) blown away from the ship, and the players don't have the time/propellant to save them all and stop the bad guy.

For that matter, propellant limits give opportunities for storytelling. A ship with a given mass ratio has a given delta-V, and there's nothing that will change that. If someone stows away (or the players try to load more people on a ship than they should) and increases the mass, or propellant leaks, the ship might not have the delta-V it needs, and everyone aboard is on a long trip to nowhere.

Atomic Rockets (http://www.projectrho.com/public_html/rocket/index.php) is an invaluable site for hard sci-fi writers. It's got everything you need to get a grip on realistic space travel--calculating mass ratios of rockets, figuring delta-Vs and transit times, analysis of common sci-fi weapons, crew arrangements, engine types and performances, etc. Plus a lot of links to other good sites. There's a lot to wade through, but it's well worth it.

[Reltzik]

How hard is your sci-fi?

I'm guessing it's soft because you had the shock wave from the asteroid explosion (plausible, depending on how small the asteroid was versus how energetic the mining process was) damaging the station. Shock waves need a medium to travel through, like atmosphere or water, and space... doesn't have that. The concept would still work by having it be a wave of radiation (emp) or a debris front (micrometeors), both of which could cause severe problems to a space station.

However, my advice will be hard sci-fi. If you're playing soft and don't like anything I say, you can just wave it away.

What about gravity? A space station out in the asteroid belt (either one of them) is pretty far from Earth. I doubt people are rotating back as part of a daily or weekly commute. The human body doesn't take extended periods of zero-g or microgravity well. Bones lose density and muscles lose strength. Resistance training with elastics can slow this process, but long term habitation requires artificial gravity. In a soft science setting, this can be hand-waved with things like "artificial gravity generators" or "grav plates". In a hard setting, the only way we know how to do this (even theoretically) is a spinning station. (It MIGHT be possible to have everyone wear iron rings, bracelets, belt, etc, and then use a strong magnetic field to generate a pull towards the deck, but that would severely limit the sort of other gear or equipment you could carry, especially unshielded electronics. Also, some things would want to float away while others would want to fall down.) This will be a problem on the asteroid as well. Even the largest asteroids will only generate a few percentage points of a g. Most of them will produce effectively nothing. Setting up a centrifuge on the asteroid itself, or in orbit, would be a good hard science solution. Ideally, you'd spend most of your day (including sleeping hours) in the centrifuge, but if it's too small to hold everyone at once you'd still put in a few hours of exercise there every day. Also, it's SO MUCH easier to do engineering and repair work in gravity than outside of gravity.

A rotating habitat produces a severe threat: You can be flung away, without the ability to get back. If the floor gives way, you fall FOREVER. This makes EVA even MORE dangerous than it already is. Safety lines, hand holds, belaying clips, and so forth are a must. A spinning hull also puts severe stress on the hull itself. The hull needs to be designed for that, or else it will disintegrate and fly off in all directions. A hull that was designed for this and subsequently badly damaged faces the same problem. Also, the asteroid's probably got hardly any gravity, meaning an escape velocity (aka, speed required to launch away from the surface and go flying off into infinity) that's pretty much zero. Be VERY CAREFUL how much bounce is in your step.

Gravity's a long-term problem. Hours, days, even weeks without it, and you'll be okay. (A bit weak after weeks, but okay.) Once you're into the realm of months, it's a big issue. Having the gravity turned off isn't a game-ender, but not having a ship with gravity means that long-range travel or long-term survival is off the menu. Also, any long-term installation will have some way of producing gravity. Not seeing this is a sign that it was never meant to be long term (or, perhaps, that it was paired with a second installation that DID have gravity).

Weapons: Hull punctures are only a hugely serious problem if they're big, if the compartment they puncture is small, if there's no way of isolating them (causing the ship to bleed out), or if the outgassing causes the hull to tear around the hull, ripping a small hole into a large one. A well-built tough hull won't have this last problem, and an armored hull that causes ricochet will probably be an even bigger reason for guns to be a dumb idea. Patch kits will probably be commonplace, scattered around any habitat with at least as much frequency as fire extinguishers. Think about alternate weapons for onboard use. I once ran a hard science setting where the primary weapons were and gladiuses. Yes, the roman swords. I figured that short engagement ranges in twisting corridors with zero sound to warn that someone was coming would favor close, melee weaponry, and a short stabbing sword would be good if you could grab the enemy for leverage or simply hurl yourself at them in a respectable charge. Guns are bad ideas for numerous reasons listed, plus recoil and the risk of hitting vital equipment.

Atmosphere. Obviously, you can't live in a vacuum. But you also can't live in a pressurized environment when the oxygen level drops too low. If it rises too high spontaneous human combustion becomes possible. Many other gasses that are part of what we think of as "air" are quite dangerous in different quantities. Pollutants like smoke are just as likely to end up in your lungs as anywhere else. Notably, carbon dioxide becomes poisonous if not filtered out, and if you're not producing carbon dioxide then you're dead. Food is rationed by mouths, atmosphere by lungs; add or subtract people from the expected compliment, and you have to adjust your equipment settings accordingly, and perhaps even that is not enough. Atmosphere control is dangerous, touchy, and convoluted.

Radiation. HOOO BOY. You can't see it, can't touch it, can't hear it. Outside of a magnetosphere (which is rare, we're lucky to have one on Earth) it is EVERYWHERE. You get too much of it and you are dead. Deeeeeaaaaaad. You might be walking around for a few hours but there's nothing to be done for you. Hard science solutions include radiation-proof (er, -resistant) hull materials, hard suits that resist radiation, radiation badges, using water tankage as shielding, and detectors that scream the most awful alarms at you imaginable. Soft science solutions include force fields (or generating your own magnetosphere, which is more of a hard solution), anti-radiation drugs, and just plain forgetting it's a problem. Having a nuclear reactor as your power source can add to this problem. For extra fun, have a radiation spike from a solar flare (as a bonus, this doubles as an EMP.)

Temperature: People describe vacuum as cold. It's actually neither hot nor cold. It's an insulator. Stick a cold beer in it and the cold beer remains cold. Stick a hot pizza in it and the pizza remains hot. There are a lot of ways to generate heat for warmth, but there are very few ways to bleed off excess temperature. A ship "glows" in infrared (at least, if it's anywhere near human-habitable temperature), and it's possible to install radiators of the right elements to maximize this glow and thus bleed heat into radiated light. Usually this is a decision made at installation time and can't be changed on the fly, though there might be provisions for covering or uncovering radiators. The station, ship, or suit will heat up from direct sunlight. You can superheat or supercool a fluid or gas and then either dump it or tank it to get the rest of your environment the right temperature, but eventually you run out of fluid or gas this way, and it's basically an emergency option. Other options are per-engineered to radiate a certain amount of heat at a certain rate, and hard to change and based on assumptions that might not hold true in an emergency, and it's quite possible to get cooked to death, especially with extra metabolisms on board. On the flip side of the coin, most heating options require power to pull off. Without power, you freeze to death. This makes EVA interesting... it limits how much time you can spend in direct sunlight or shadow.

Isolation: There's no corner store for you to pick up a replacement part or a spare tank of oxygen. You've got nothing but what you've brought with you, and this makes everything that breaks or gets lost a major issue. Recycle everything you can, or better yet design everything to be reusable. Include major machine and electronics shops that let you improvise new components or replace old ones. This is one of the reasons that a nuclear (fission) reactor is a GOOD idea. A few 50 pound rods can provide you all the power you need for a century. No need to stop by the gas station. In particular, air and water can be recycled, but unless you've got some sort of farm where you're growing plants (or at least edible algae or bacteria) then food is going to be an issue. So can going stark raving mad. Computer memory is cheap, so be sure to have lots of entertainment programs and video games.

Propulsion: Since getting from point A to point B is a significant part of your plot, this needs mentioned badly. The big issue isn't fuel so much as it is reaction mass. The two get confused a lot, so I'll put it simply. Reaction mass is the stuff you throw in one direction so that you get pushed in the other. Fuel is what gives you the energy to throw it. The big problem is that before long, you've thrown away all your throwing-away stuff (reaction mass) and have nothing left to throw away, which means you can't go anywhere. Bringing along more reaction mass increases how much your ship masses (in lay terms, how much it weighs), and requires you to throw more reaction mass away in order to get the same increase in speed, because you're trying to speed up a heavier object. So you need to bring along more... and more... and more. This is called the rocket equation, and it's a pure ironclad bitch for interplanetary travel. There are two fairly hard solutions. The first is a ramscoop, a device designed to gather up reaction mass from the interplanetary medium and refill your reaction tanks. This will need to be very big and work very slow, because the stuff is thinner than any vaccuum we can create in any laboratory here on Earth. The second option is a reactionless drive... basically any propulsion system that doesn't work on the principle of reaction mass. While most of these are soft science fiction, a solar sail is a hard, plausible solution that just saw its first real-world empirical test. (Just remember, it only lets you accelerate AWAY from the sun, not towards it). Don't forget, you need to work just as hard to slow down at your destination as you worked to speed up at your starting point!

Navigation: Navigation in space is difficult. You're being acted upon by multiple gravity wells that change in influence as you move in or out of them. These affect your velocity, which affects your position, which affects how hard the gravity wells pull you. You can't solve for these variables in isolation; you have to solve them all at once. Your end goal isn't just to get from Point A to Point B. It's to get from Point A at velocity A and Time A, to Point B at Velocity B and Time B. You have to match not only position, but speed, and do so with perfect timing. The targets are exceptionally tiny, too. Look up at the night sky, pinpoint Mars. That's what's you're aiming for if you want to reach the nearest planet. (Well, that'd be Venus, but we don't want to go to Venus.) It's harder with things like asteroids and space stations, which don't produce gravity wells for us to sink into and don't have atmospheres for aerobraking. Clever navigators can pull off incredible, reaction-mass saving accelerations and decelerations with sequences of orbital slingshots charted out months or years in advance of actual execution, but timing for these is critical. But tooling around the solar system requires either moving extremely fast (on a scale where a speeding bullet is SLOW), or taking years to get anywhere. Putting together propulsion (with the way it changes the mass of your craft) and navigation is a very difficult problem, but it's not like it's rocket scie- oh, wait, it is.

Anyhow, the good news is that you're not likely to plow into an asteroid by accident. MAYBE, in an awful nightmare scenario, you'll get hit by a pebble or two. But those scenes of asteroid belts from Star Wars? Forget that. Putting these two together and you're going to have a problem with your kamikazee prisoner plot. How did he get the space station moving?

Power: Most everything you do out there will require power of some sort. You've basically got three or four options. (1) Nuclear reactor. Fission is the best option. Disposal of radioactive waste is easy, a fission reactor takes up little space, and the fuel can last literally for generations. On the other hand, it IS a major radiation hazard. (2) Chemical reactor. Basically, burning gas, coal, hydrogen, or whatever. This isn't a good solution overall because you go through fuel quickly, but it's handy for rocket propulsion, short-term excursions, and vehicles you don't want to put a nuclear reactor in (like a space suit). Hydrogen cells are good for this overall because it's easy to recycle the waste product (water) back into hydrogen and oxygen with more power from (1). (3) Chemical batteries. You can probably fold this into (2). (4) Solar power.

Fire: Fire BAD. Fire consumes oxygen, damages equipment, produces often-toxic smoke (especially if it's burning plastics), and produces massive amounts of heat. The good news is, environmental controls will make it easy to snuff a fire out and your typical oxygen-consuming fires put themselves out in zero-g. (Most flames draw in air from below as the exhaust pushes upwards. Without a clear up or down, the heat pushes the exhaust flame in all directions, there's no way for oxygen to come in, and the fire is extinguished.) However, some chemical reactions are capable of running away all on their own without oxygen; these fires won't consume oxygen, but will cause every other problem that oxygen-consuming fire causes and be real hard to put out.


Here's possible adaptations of your plot.

1) As your heroes approach the asteroid, it explodes for reasons unknown. Their own craft is damaged by the debris. They can handle short-term excursions but not long-term. Alternatively, they're on a short-range shuttle and their mother ship is destroyed.

2) A hab section with a centrifuge remains -- damaged, but operable. It offers a prospect of surviving until your heroes can be rescued, or of equipment for repairing the mother ship to the point where it can be brought home. This is your military installation with the prisoner that's taken over everything.

3) The prisoner is trying to commit suicide and take his tormentors with him by using every last thing I just mentioned. He's slowly figuring out how to get into various systems and take them over. He can monkey with the air, the temperature, the nuclear reactor controls, the radiation shielding, the pod bay doors, water recycling (poison ahoy!), you name it.

4) On top of all this, the hab is damaged and needs repairing before it comes apart.

5) The prisoner's somewhere hard to get to. They'll need to beat him eventually, but your heroes should spend most of his time preventing his attempts to kill everyone. The big challenge will be disabling the hacked equipment without destroying it because, hey, that stuff's vital.


EDIT: And that's why I shouldn't write long posts. In the time it took, you fixed the shock wave problem and others contributed much of what I had to say. Oh well.

[Surpriser]

Wow, thanks for your comments and especially Reltzik for your detailed analysis.
You have given me both a lot of ideas and some points that I will have to correct.

Concerning gravity:
- It seems that asteroid mining that is not completely robotic would necessarily have to depend on a spinning space station to provide habitats for the workers. I can circumvent this by having this station completely destroyed by the explosion. The base on the asteroid itself was meant to be a temporary structure anyway (from a prospecting mission), so having microgravity there should work out.
Alternatively, if I don't find anything interesting to do there, I might also skip this part and send the PCs to the aforementioned station directly, where they find out that it also had a military use. The mining station was primarily meant to be a diversion anyway*
- For the station itself, a ring-shaped station with a zero-g central part would be really interesting (I am a fan of unusual geometry). However, the only maps I could find of such stations were huge colony-sized things. Do you know where I could find a (free) map I could use? The precise challenges will depend largely on the layout of this map.

Ricochets for weapons will mostly be hand-waved away, as it is done in most games I know of. But they will be warned that a critical failure could break something important, so guns should be used as a last resort.

Ressource, equipment and fuel shortages will be based on story-needs. Unless it provides an interesting challenge, there will be enough fuel and air available.
It certainly does give me an excuse to enforce limits on the capacity of any vehicle used.

Navigation will be handled by a simple roll for the pilot skill, the rest will be done by the on-board computer.

I would really like to set them a time limit. Which of these options is the most plausible/interesting:
1) The station is on a collision course with some other object - be it an asteroid or larger debris from the explosion. This might be due to really bad luck, but of course the station is maneuverable to some degree, so the prisoner (he needs a name, lets call him Chief) could have adjusted the orbit slightly to hit something big enough.
2) Due to the damage on the station, the air-filter system is damaged. The remaining supply will last for a few hours at most. Repairing the system (and thereby removing the threat of time running out) would be a nice secondary goal.
3) Reactor overload. I don't know how realistic it is to have a fission reactor (either damaged or sabotaged) slowly breaking down until the big bang. Rising radiation levels, which the station was not built to handle, could be a factor too.
4) All of the above, providing two secondary goals and a hard timeout.

Some other challenges I can think of:
- The Chief has control over all surveillance systems and air locks. Unless they find a way to gain control of these systems, they will be sitting ducks, as they can't get anywhere unseen.
- While currently their personality is overwritten by that of Chief, the crew can be rescued by knocking them out. This will reset their minds, but they will require medical attention to wake them up again.
- There could be even more prisoners (as replacement, in case of failed experiments), who can serve as either tragic losses, valuable help or at least a diversion. They certainly don't like the idee of committing mass suicide, but won't trust the PCs or anyone of the crew either.

*If I tell them to go to a research or military station that has gone dark, they will immediately assume that anyone greeting them is the enemy. Via the detour to the mining colony, I hope to ease their suspicions, especially if it is made clear that the explosion was caused by an accident.

[Storm_Of_Snow]

Certain areas of the station could be off limits without an appropriate security clearance. This could range from simple locked doors to an automated defence system that might have turrets, but can also make environmental changes, such as the gravity generators (invert their effect to throw intruders at the roof, redirect it so they're pulled away from the secure area, or amplify it massively to pin them to the floor until they asphyxiate through being unable to get air into their lungs anymore), turn lights on and off (strobe them to induce nausea and possibly seizures, leave intruders in pitch darkness etc), life support (depressurisation, removal of oxygen/failure to remove CO2, even increasing pressure - especially on the other side of a doorway (sealing it if it's hinged and opens into that section, or coupled with turning the gravity generation off to blast an intruder away if it slides or opens away from that section), and so on.

Reltzik mentioned heat buildup - as an example, Skylab crews had to place a gold sheet over part of the station in order to reflect solar radiation because some of the radiators were damaged at launch, and the station would have cooked otherwise. A station on an asteroid outside the star's life zone might need reflectors behind it to increase the amount of solar radiation hitting it, and compensate for heat bleeding out of the station into the asteroid without requiring the power plant to be run at a higher capacity and thus reduce the endurance of the base.

[Reltzik]

For maps, don't afraid to go symmetric and/or modular. The designers will want to balance the weight of the ring, after all; they don't want it wobbling like a misloaded clothes washer. So, feel free to make a boring map, like it's a motel. Main corridor. Bedroom, bedroom, bedroom, bedroom. Lab. bedroom, bedroom, bedroom, bedroom. Mess hall. Office, office, office, office. Gym. So on. Technical details: You probably want a spin of no more than 4 RPM, preferably closer to 1 RPM, to avoid having everyone on board feeling like they're on one of those spinning teacup rides all the time. In order to get 1g out of that, your hab ring will need a radius of 56m or 895m, respectively, giving perimeters of 352m and 5623m, respectively. (Perimeter, in this case, means how far you have to walk around the hab rim in order to get back to where you started.) The relationship between RPM and radius (and perimeter) is inverse-square, so if you halve the RPM you need to quadruple the radius and perimeter. You don't need a full 1g for survivability. THAT relationship is linear -- if you want to make do with half a g, that cuts the radius and the perimeter in half. For a quarter g, divide the radius and perimeter by 4. You probably don't want to go much below a quarter g. All told, that gives you a lot of range of distance to work with. There's no reason you need to rotate even as fast as an RPM, either, if you want a perimeter that's 6km or longer, just have the station spin more slowly.

For extra fun, introduce the Coriolis Effect. Ballistic courses will NOT behave the way you expect them too. They will tend to curve wide and to the outside of the can. Bullets travel too quickly to be affected much, but thrown objects and long jumps will be a problem. This will probably be more trouble than it's worth as a GM, but it might be fun if your players get overly clever with some Rube Goldberg contraption.

Going through your list of options:

1) This isn't that much of a major threat. Debris will be difficult to pinpoint with radar or telescopes until you're in "omg we've got seconds to live" range, which works against the PCs when it comes to dodging it, but also against Chief when it comes to setting a suicide course. Unless the space station is capable of major acceleration or starts very near an asteroid, a collision course will take weeks to reach its destination, and the slightest course change can avert it if you don't wait too long. As in, a single thruster burst, or even just blowing out an airlock. (Remember, it took the better part of a week for the Apollo missions to reach the moon, their spacecraft were more rocket than craft, and the moon is pretty dang close to us relative to how far apart asteroids are.) Large, relatively immobile chunks that are very close also aren't much of a threat. Remember, it's not generating much gravity, so you can't die from falling damage. Your space station would need enough delta-v to accelerate to... well, at least fender-bender speeds (say, 30kph), which actually take a while unless you're basically strapping a phone booth to a skyscraper of fuel and rocket the way the Apollo crew did. Extended burn on something like a space station, which is far more phone booth than rocket, means that by the time you're hitting good impact speeds you've actually been flying a ways. Your best possibility is to have a large chunk of asteroid that the station was initially stationary relative to, but which following the explosion is now inexorably slowly drifting its way towards the station at a speed of, oh, maybe 100kph. On an astronomical scale this isn't even a snail's pace, it might take days or weeks to hit, and it doesn't SOUND like much, but even at 100kph there's no such thing as a gentle nudge. More explosives or just tow cables attached to a small shuttle would fix this, or maybe you could move the station out of the way, but if that thing hits it's game over.

2) A reasonable threat. Be sure to specify what type of filter you're changing. A CO2 filter implies a very different threat than a particulates filter. One suggests that your environmental machinery is overloaded because there's too many people breathing on the station for its newly-reduced equipment to handle, while the other could suggest a fire somewhere. (Of course, CO2 filters might get overloaded by that as well). For extra fun, you can describe the problem to your players with the actual phrase "too many people breathing on the station".

3) Generally speaking, fission reactors do not go bang. At least, the cores don't. What might go bang is the large tanks of water used for cooling, or which circulate to exploit the temperature differential that the core creates and translate that into power. Boil those tanks until they pop and yeah, you can get a big steam explosion. For drama during a boss fight, you can even have smaller valves giving way under the increasing pressure, venting dangerous steam jets. But the core itself is pretty non-explody. When fission reactors overload, they do something far, far worse than explode. They go into meltdown.

The basic idea of a fission reactor is that you've got radioactive fuel. The radioactive fuel is slowly atomically decaying and giving off radiation and heat as it does so. If the radiation it gives off hits more radioactive fuel, then that prematurely triggers decay, and more radiation and heat, which hits more fuel, which also decays faster than it would, and so on. So, get enough fuel rods close enough together (these are solid things), and you really speed up the decay process and get all the heat it produces a lot faster. Heat is good for heating water and turning turbines and also not freezing to death. But too much heat can damage the reactor, cause water tanks to burst, etc. The challenge of a fission reactor is the finicky, touchy balancing act of keeping it in the Goldilocks Zone of "hot enough to be useful, but not so hot that it's dangerous". Normally the reaction is controlled by sliding in something that intercepts and blocks radiation between fuel rods, cutting them off from each other. Your default option will be sliding in control rods between the fuel rods (basically, slabs of radiation shielding), with emergency options like flooding the core with a neutron-blocking gel. The latter option will prevent meltdown, but will also ruin the reactor or at least take it offline for quite a long time. In space, you might have a third option of just jettisoning the core entirely and falling back on batteries and/or solar panels until rescued.

If none of these options happen, then the core just gets hotter... and hotter... and hotter. At some point, the fuel rods melt. The housing melts. The radiation shielding melts. (Also, at high temperatures its material properties change and it stops doing a good job of shielding against radiation.) The machinery that moves the control rods in and and out and the machinery that injects the emergency gel and the machinery that jettisons the core all melt. The computers controlling all of it melt. It glows red-hot and then yellow-hot and then white-hot. Escaping radiation contaminates everything nearby, turning IT into radioactive hazards. The HULL melts. No, vacuum doesn't stop the meltdown, not unless it's a violent decompression that scatters the globs of radioactive molten fuel everywhere and splits it up. In gravity, the molten magma slurry of awfulness that used to be your power source literally melts a hole down through the concrete floor, and the rock underneath, until it hits the water table and poisons everyone to death. Without gravity, that doesn't happen. It just sits there like a glob of perpetual shining death irradiating and melting everything until the fuel runs out... a process that will take decades.

This is, of course, bad for the station on many levels. In addition to the problems of radiation, you've got excess temperature and losing power. If you're out in the hab ring, its radiation shield is intact, and the radioactive particles don't get into the air system, then the temperature or power loss or hull damage will probably kill you before the radiation does. But the radiation will be what terrifies you.


For game balance purposes, I'd suggest having the Chief have all of these available as options... but not initially, and not all at once. The Chief has to do a lot of hacking, figuring out where control systems are hiding when he doesn't know how the directories are laid out, guessing passwords, learning how to use the unfamiliar control interface, correlating camera feeds to physical location, reading up on how to force a reactor meltdown, overriding safeties that prevent all sorts of stupid things being done with airlocks or environmental controls, and so on. For extra fun, have a bunch of maintenance drones designed for things like EVA that the Chief can take over... eventually... but which will prove useful to the players until then. Disconnecting computers from central control might handicap him... or, given the prevalence of wireless signals in your future, might not. Of course, the maintenance drones or mind-slaves might undo this, working subtly to keep him in control of the computers. I don't know how the mind control would work, but I'd imagine that the Chief isn't particular adept at managing that either. Just because you've got a dozen extra sets of hands doesn't mean your brain knows how to use more than two at a time, or keep track of where they all are, or intuitively recognize the opportunities they present as they present them. One of the scariest parts of this story might be that the Chief is LEARNING, getting faster and more effective at using all these new tools at his disposal.

[Surpriser]

So, I will have a central rod, with a power core (fission reactor) at one end and a control center on the other end, with storage space and laboratories (including the one containing the chief) in between.
This is surrounded by a ring of habitats, including living space, live support, more laboratories, workshops,...
Where should I put the docking bay? From a gaming perspective, it would be more convenient to have the hangar on the outer ring, so that the PCs can plot their way inwards (with a big showdown in zero-g at the center). But it seems that such a layout would seriously destabilize the ring (the clothes-washer syndrome). The same problem arises for weapons systems with recoil.

How long would such a meltdown take before it reaches critical levels? I'm asking only for rough estimates (seconds, minutes, hours, days), the fine tuning will be set by the strength of the security measures and shielding.

The mind control is supposed to be more like a mind overwrite. The crew is still capable of independent action, but with the memories and personality of the Chief. As such, they all work together to bring an end to the station (though allowing some of them to be persuaded otherwise would be an interesting challenge too - as in: "You don't have to die, just because the original can't leave"). This way, they have all the necessary security clearance to do stuff, but not the knowledge how to do so, at least in the beginning.

When the PCs arrive, the Chief will be in control of the comms systems and all doors and airlocks, although the latter can only be locked/opened on site and both doors can never be open at the same time. A section of the ring will be damaged and sealed.
Later on, he will gain control of the following systems (maybe in random order, whenever the PCs are about to do something unconvenient?):
- Cameras
- Door remote control
- Air filter system (initiating a time limit before the CO2 builds up to toxic levels)
- Lighting and Laser barriers
- 2 maintenance drones on the outside (who are initially busy trying to repair the damage to the habitat section)
- The reactor (initiating first one countdown, up to which it is possible to stabilize the reactor if they reach it in time, and then a second during which the whole reactor module can be jettisoned. After that, the clock starts ticking until the whole station falls apart)
- any other ideas?

[Lord Torath]

Docking on the ring is Bad IdeaTM. Trying to match speeds with a rotating bay would be effectively impossible. You'd need to approach on a helical path, which is just about impossible in a vacuum. The docking bay should be in a non-rotating section of the base. You could get by with a rotating bay located along the central axis of the station, but you'd need to spin your craft as you approach, costing maneuvering fuel, and overall making things just that much more difficult. Plus, zero-G makes loading and unloading much easier.

[Storm_Of_Snow]

Docking on the ring is Bad IdeaTM. Trying to match speeds with a rotating bay would be effectively impossible. You'd need to approach on a helical path, which is just about impossible in a vacuum. The docking bay should be in a non-rotating section of the base. You could get by with a rotating bay located along the central axis of the station, but you'd need to spin your craft as you approach, costing maneuvering fuel, and overall making things just that much more difficult. Plus, zero-G makes loading and unloading much easier.
You'd also be putting tremendous strain on your docking points if you dock to the ring - if you need to have gravity for whatever reason, then the centre line docking bay (Babylon 5 or Coriolis stations in Elite) would be best (meaning at worst the craft has to roll to enter - but once that roll is set up, it'll require no more fuel to maintain it in the short term, then the craft is manipulated to its berth once inside - whether that's big robot arms or tractor beams is up to you).

Although that could be another complication - the docking systems are out of action, so the crew have to move their ship to its berth themselves.

The alternative - a stable section with a spin habitat - may be easier, but you'd ideally need contra-rotating pairs of habitats (otherwise they'd probably stay still and the stable section would rotate instead :smallamused: ). And you could get the PCs racing to fix the system before it breaks down and starts the whole thing spinning around in the very destructive way it wasn't designed to do.

[Reltzik]

Agreed with Storm of Snow that reflectors to concentrate sunlight onto solar panels might be a good idea. It also gives the Chief an added tool in his inventory of death: Concentrating sunlight somewhere OTHER than the solar panels. The hull's probably tough enough to take it... but someone who's EVA might be in for a very bad excursion. Ant, meet magnifying glass.

Also, I'd agree with Storm AND Torath that docking on the ring is bad. It would be like trying to board a moving carousel, when you have to approach it on a toboggan sliding across the slickest ice imaginable, and you need to grab on to a PARTICULAR HANDHOLD. It's the match-speed-position-and-time-all-at-once problem all over again. ... though if you've got computers devoted to astrogation, they can probably handle this problem easy. The bigger problem is, indeed, the unbalanced clothes-washer issue. Launching from the ring can be cool (great place to put escape pods), but docking in the hub is easiest. If you really want the PCs to start in the hab ring, then have them go to the docking port at the hub, discover it is nonoperative and/or hostilely defended, and have them EVA "down" exterior ladders to a working airlock on the hab ring.

How long the reactor will take to melt down would depend on the reactor design. "Many minutes to many hours" is probably a good answer, but if it's engineered for heavy protection the answer might be "days". It WON'T be designed such that it can run away in a matter of seconds. The designers will have made it so that the humans will have time to notice it, think through a solution, discuss it, and implement it. Most reactors will also be fail-safe... if something goes wrong, the computers shut it down by default. Expect a lot of safety measures to be automated, and hacking around them so that they don't trigger will be a huge task for the Chief. Figuring out what the Chief is up to might go something like this:

"Okay, so I'm in the computer systems. What's the Chief working on right now?"
"The Chief is currently disabling Alarm #2953 so that it won't sound throughout the station when it's supposed to."
"Okaaaay, and what does Alarm Number Whatever do?"
"Alarm #2953 sounds if someone tampers with the control systems of the automated neutron-absorption-gel injectors."
"And these neutron-gel-injectors... what do they do?"
"The neutron-absorption-gel injectors are an automated safety feature. They are designed to spray the interior of a nuclear fission reactor with a gel that basically stops the nuclear fission in a process known as SCRAMing the reactor. They do this automatically as the last line of defense to prevent a nuclear meltdown."
".... so the Chief is trying to disable the alarm that would normally warn us if someone, like the Chief, is monkeying with the safety mechanism that prevent the nuclear reactor from going critical?"
"One of the safety mechanisms, yes. Oh, and the Chief has just now successfully disabled Alarm #2953. He's moving on to alarm #2876, which monitors the control rods that are the FIRST line of defense against meltdown."
"....ohcrap."

EDIT: Oh, and you don't need reaction thrusters to spin up the craft. You can use rings that spin one way to spin the craft another way. This causes engineering difficulties (every moving part is hard on engineers who design and maintain it) but saves on reaction mass, which is a major concern.

[Surpriser]

Thought so about the ring. In that case, the weapon systems will be a bit more effective than originally planned and the shuttle will be destroyed before it can reach the docking bay at the front of the central part (the back containing the reactor). Time for the first EVA, luckily there will be enough spacesuits and a small emergency pod for everyone on board.
As all airlocks will be, well, locked, they will have to decide between forcing their way in or landing on the damaged section of the habitat, which was depressurized automatically to snuff out the fires.

At least this gives them an obvious goal even before they know about the Chief: Get to the hangar, as that is the only place that contains another shuttle. The emergency pods were all immediately launched of course, wouldn't want anyone to sneak off like that.

I will also need to provide quite early access to some sort of systems monitor, so that they can find out what they have to fix this time. Alternatively, I could let the chief ignore the alarms (everyone will die anyway, so why bother keeping it secret?) and inform the PCs about any dangers with red lights and sirens.

There will probably be at least one additional control center on the ring, where access to a lot of systems can be gained.

[rs2excelsior]

Seconding above that docking is best handled in the central section. You could have a small crew-transfer section where the ring meets the center bar that can be spun or stopped to allow movement between the two sections--offering another point of contention/obstacle for the PCs. Weapons would also be best mounted on the central section, as that's a stable firing platform. It matters less for projectile weapons, but lasers rely on dwell time on target, so NOT rotating out of firing arc every 20-30 seconds would be a good thing. Also, the rotating hab modules will have a gyroscopic effect on the station, mitigating the effects of recoil.

Also seconding dual counter-rotating hab modules; it'd save a LOT of propellant.

[The Grue]

A station on an asteroid outside the star's life zone might need reflectors behind it to increase the amount of solar radiation hitting it

Why? If the objective is for increased solar power generation, it's more efficient to cut out the middleman and build more solar arrays. If you mean to make the asteroid habitable without life support, uh, there's actually not much you could do to make that happen. Until humans no longer need to breath oxygen and can tolerate extreme and rapid temperature changes then we're talking about a pressurized habitat on said asteroid. And as long as we're filling it with air we might as well heat it up a bit too.


and compensate for heat bleeding out of the station into the asteroid without requiring the power plant to be run at a higher capacity and thus reduce the endurance of the base.

You' actually want to be dumping heat into the cold asteroid, or else you'll cook the inside of your asteroid base. O2 cycling, lights and computers all generate heat as a byproduct - as do the metabolic processes of your human crew. If you're still radiating heat, it's trivial to install and run some electric space heaters(no pun intended) to compensate - it's a lot easier to heat up the inside of a spacecraft than to cool it down, especially if your primary power plant is in fact the sun.

[Reltzik]

Agreed on the heat thing. It's easier to build up heat than to dump it (provided you have power). But I figured that mirrors were probably cheaper than solar panels, up until the point where there was such an intensity of light on the panels as to be dangerous or create inefficiencies. Sure, you can build more panels, but it's probably cheaper to build more mirrors.

[The Grue]

Remember that mirrors aren't 100% efficient at redirecting incoming energy, though - I don't even know where to start with the math, but my intuition is that you might get less energy per [monetary unit] building mirrors to reflect sunlight onto your solar panels than you'd get by simply building more/bigger panels. Otherwise, why does the ISS have a bunch of solar panels instead of a few panels and a bunch of mirrors?

[Reltzik]

Not 100%, no, but pretty darn high. A typical everyday mirror has an albedo somewhere in the 75%-80% range. An industrial mirror would probably have a higher albedo. Given how expensive solar cells are, we could buy 25%-33% more mirrors than solar cells and still get lots of savings. I'd guess ISS doesn't employ mirrors for one of the following two reasons: (1) the engineers weren't feeling that clever. (2) the mechanisms for controlling or maintaining them introduced a level of expense or practical difficulty. But mirrors ARE used here on earth for solar power, to get the same results for much cheaper.

In any case, either approach will work and both are quite plausible.

... but the mirrors are cooler. :smallbiggrin:

[Knaight]

Not 100%, no, but pretty darn high. A typical everyday mirror has an albedo somewhere in the 75%-80% range. An industrial mirror would probably have a higher albedo. Given how expensive solar cells are, we could buy 25%-33% more mirrors than solar cells and still get lots of savings. I'd guess ISS doesn't employ mirrors for one of the following two reasons: (1) the engineers weren't feeling that clever. (2) the mechanisms for controlling or maintaining them introduced a level of expense or practical difficulty. But mirrors ARE used here on earth for solar power, to get the same results for much cheaper.

The price difference between solar cells and mirrors is a big deal here on earth. In space, the vast majority of the price comes down to how much mass you have to get out of earth's gravity well. In addition, if the mechanisms are more complicated they are more likely to need repair, which means sending more mass out to repair them (though this might just be sending them up with replacement parts). In short the savings highlighted can just about be completely ignored, and what actually works better depends almost entirely on mass. Judging by how the ISS and tons of satellites use solar panels, I'd be willing to bet that mirrors are more expensive.

[Reltzik]

But we're talking about a setting with space-borne industry and mining. There's no need to lift mirrors out of Earth's gravity well. If anything, we'd be looking at a frontier economy where simpler objects (mirrors) can be produced locally, but more complicated products (solar cells) can't be, or can't be as easily as they might be produced back in civilized territories and then imported.

(This is how I nitpick the nitpick of the nitpick of the nitpick. :smallbiggrin:)

[The Grue]

Let's resolve this tangent once and for all:

Given "the station is covered with solar panels", the players will accept the description and move on.

Given "the station has a few solar panels, and in the distance you can see a collection of mirrors", the players will stop and have this exact conversation we are currently having as to why before continuing on with the game.

Thus, it's in the interest of session expediency to have solar panels rather than mirrors. :P

[Surpriser]

Solving engineering problems by minimizing the expected amount of arguing - I like it!

However, since a fission reactor will provide most of the energy (the meltdown scenario is just too awesome to omit), solar panels will only be used as a backup power source (if at all).

While designing the habitat area, it has turned out that even a quite small ring (210m circumference, 0.5g have to suffice) provides a lot of room that wants to be filled.
With a crew of not more than 20, there is only so much room you can use for living quarters and storage, especially since there is not a lot to interact with in these areas (storywise).
Aside from that, I already have:
- Two secondary control rooms (basically a terminal where various status checks and life support configurations can be executed). These will provide PCs access to the stations network and information about the current situation.
- Offices, possibly included in officer living quarters. Lots of files detailing the experiments and recent events.
- A small prison, with two additional prisoners. If convinced to trust the PCs, they can be valuable allies.
- Laboratories in addition to those on the central rod, though I am not sure what to put in there.
- A sickbay and medical center.

What else would be suitable to be put on the ring?
Power supply, armory, docking bay and bridge will be located in the central part, together with the main laboratory holding the Chief.

[Reltzik]

Solving engineering problems by minimizing the expected amount of arguing - I like it!

However, since a fission reactor will provide most of the energy (the meltdown scenario is just too awesome to omit), solar panels will only be used as a backup power source (if at all).

While designing the habitat area, it has turned out that even a quite small ring (210m circumference, 0.5g have to suffice) provides a lot of room that wants to be filled.
With a crew of not more than 20, there is only so much room you can use for living quarters and storage, especially since there is not a lot to interact with in these areas (storywise).
Aside from that, I already have:
- Two secondary control rooms (basically a terminal where various status checks and life support configurations can be executed). These will provide PCs access to the stations network and information about the current situation.
- Offices, possibly included in officer living quarters. Lots of files detailing the experiments and recent events.
- A small prison, with two additional prisoners. If convinced to trust the PCs, they can be valuable allies.
- Laboratories in addition to those on the central rod, though I am not sure what to put in there.
- A sickbay and medical center.

What else would be suitable to be put on the ring?
Power supply, armory, docking bay and bridge will be located in the central part, together with the main laboratory holding the Chief.

Mess hall.
Gym. Exercise is one of the main advantages of gravity. If you've got the space to spare, put in a pool. It will double as water tankage and easily-relocated ballast.
Lounge/rec hall/entertainment center.
Engineering bays and machine shops. There's lots of stuff that's more convenient to work on in gravity than out of it. In particular, anything with lots of fiddly parts that you don't want floating away when you disassemble it, and anything leaking liquid that you'd rather have forming a puddle instead of free-floating gobs.
Environmental equipment. Probably a lot of small stations scattered throughout rather than one big unit in the hub. For bonus points, have the air vents be designed to double as maintenance crawl spaces.
Storage. It's probably easier to store some stuff in the hub, but again, it's nice to be able to shift mass around the ring as needed, so this will double as ballast. Also, most work will be done in the ring just for the sake of comfort, so they'll want supplies close at hand.
Emergency shelters. Places to retreat to in case of a solar flare, decompression, or whatever. These might be the jettisoned escape pods.
If it's a military base? A shooting range. Because military.
Hydroponics. After an extended stay fresh food that isn't freeze-dried and shipped from Earth will be in high demand. If this isn't allowed, someone will have set it up in their closet anyway. Also, a still.
Laundry.
Showers.
Waste processing.
Algae tanks. A low-tech solution for producing oxygen and consumables and recycling waste, all in one. (I hear it's better than MREs.)

[The Grue]

If it's a military base? A shooting range. Because military.

Er...

If you're using explosives to propel bits of metal at high velocity in a pressurized oxygenated compartment...

...you're going to have a bad time.

Could have one on the outside of the station I guess. Reduced risk of hull breach, zero risk of fire!

[Reltzik]

It's not that hard to do. Just make the compartment walls tripple-thick, physically guaranteed to stop any small arms fire. Besides, what self-respecting GM would pass up the opportunity to give the PCs the gear that they most dearly want and can least sanely afford to carry?

... but the rotating frame of reference and stuff would make training in that kind of environment counterproductive. You wouldn't learn to shoot, you would learn to shoot POORLY. Withdrawn.

[The Grue]

Actually, shooting in a rotating inertial reference frame might be a useful skill to learn.