Writing: Input Wanted How to Handle a Fire Onboard a Generation Ship?

[DaveC426913]

The last time we thought about this, I had the rotating sequence completed within a few seconds - given the speed at which the ship is still coasting at this point, I thought the deflector lasers could only clear the path ahead for so many million kilometres. @DaveC426913 considered the time I allocated for completing the rotating sequence far too short, as far as I recall. ;)

The rate limiting factor will be the lateral stresses on the ship during its rotation.

For an operation that's meant to happen only once during the whole trip, you wouldn't want to over-engineer the structures designed to resist these lateral forces, since mass is at a premium. You would therefore make the turnover as slow as possible.

Perhaps that's what went wrong. Perhaps the original design had it being rotated over hours instead of seconds, but that was based on an inaccurate estimation of how much time they had protection using the lasers. With a shortened window of safety, they'd have to speed up the turnover. Something is bound to break loose.

 

[Strato Incendus]

Perhaps that's what went wrong. Perhaps the original design had it being rotated over hours instead of seconds, but that was based on an inaccurate estimation of how much time they had protection using the lasers. With a shortened window of safety, they'd have to speed up the turnover. Something is bound to break loose.

Ooh… I think I like where this is going! Thanks a lot!

So basically, the lasers can’t clear enough space in front of the ship to allow for as slow a braking sequence as anticipated. Two follow-up questions:

1) One way to address this issue would be to simply add more lasers all around the ship. If it rotates much more slowly, it will be easier for the lasers to be accurate even during rotation, won’t it?
The main way to dismiss this would be to argue that extra laser cannons add extra mass… but then again, the ship has a lot of other stuff on board which is probably heavier. So being stingy when it comes to the lasers wouldn’t make sense.

2) What about the dust-cloud solution you considered so brilliant, and which we hadn’t thought of until recently? ;) If this renders lasers redundant, we’ll have to come up with a different reason for flipping the ship faster than intended.

 

[DaveC426913]

What about the dust-cloud solution you considered so brilliant, and which we hadn’t thought of until recently? ;) If this renders lasers redundant, we’ll have to come up with a different reason for flipping the ship faster than intended

I figured it wasn't about inadequate lasers so much as they hit a pocket of dense interstellar dust that wasn't in their predicive models.

They can't predict that very well when first plotting the trip and it's just bad luck that they came upon the cloud right at turn over. A risk they knew about on launch yet nonetheless unavoidable.

Ejecting a defensive cloud ahead of the ship is all well and fine but if the onslaught of interstellar dust is dense enough it will deplete the defensive cloud faster than ideal, requiring a dangerous, but unavoidable, fast turnover.

 

[Strato Incendus]

I figured it wasn't about inadequate lasers so much as they hit a pocket of dense interstellar dust that wasn't in their predicive models.

They can't predict that very well when first plotting the trip and it's just bad luck that they came upon the cloud right at turn over. A risk they knew about on launch yet nonetheless unavoidable.

Wow, that’s great! Believe it or not, that was precisely the idea I had last night when thinking about this. Perhaps it’s simply the most straightforward, “Ockham’s razor” explanation. I’m glad I didn’t post it, though, because the fact that you came up with this independently from me suggests to me it will intuitively make sense to the reader, too.

Last night, I was wondering whether the pocket of dense interstellar dust should be “caused” by something (so that it feels less like plot convenience), or if it should indeed be the randomness of space you can encounter at any moment — the latter would fit thematically, since the crew kind of see the surrounding universe / cosmos as the external enemy that’s always out to kill them.

This is why I’m so fond of your suggestion, because it moves the cause the of the problem back to the ship’s exterior. Even though this thread has moved away from the original idea of a fire breaking out on board (which could of course still happen as a result of this), a fire inside the ship would ultimately have felt more like human failure at best, and deliberate sabotage at worst.

The best part is, going back to the issue of interstellar dust particles even allows me to keep the additional problem of a single dust particle piercing the ship hull (and potentially killing some people as it passes through the ship). This is something we’ve discussed at length before — I simply won’t specify the actual size of the dust particle, so that the debate doesn’t become about whether a particle of this size at 0.125 c would have destroyed the entire ship, or simply punched holes into the walls of several rings and/or water tanks (the latter of which are used for both shielding against radiation and as fuel storage for the nuclear-fusion drive).

In short: The dense dust cloud which the lasers can’t handle in time is what causes them to turn around faster than intended, and that causes friction on the ship’s structure. Given the setup of “the lasers can’t handle this much dust”, the odds of at least one speckle of dust piercing the ship would actually be higher, so this wouldn’t come out of nowhere.

Ejecting a defensive cloud ahead of the ship is all well and fine but if the onslaught of interstellar dust is dense enough it will deplete the defensive cloud faster than ideal, requiring a dangerous, but unavoidable, fast turnover.

Great! :) This means the ship had this extra layer of protection, but it was depleted — rather than the ship designers / earlier generations of crew members “simply having forgotten” about this option. I always prefer the “we had it, but it got destroyed” explanation (especially since the ship can only recycle its resources, not pick up any new ones) over “we forgot to include it at launch”.


I think you’ve once again solved a major issue for my story, @DaveC426913 — and more importantly, this time, it was one of the major plot holes that was keeping me stuck for several years! :D (I think I should probably include a “Dave” at some point in the prequel, among the ship designers… because the Exodus’s iconic dumbbell design was also your idea.) Many thanks once again for all of your ideas and effort!


Now all that’s left is to predict the characters’ responses to this issue:

1) The decision to turn the ship faster than intended has to be based on the commanding staff picking up the denser dust cloud prior to getting there. This means they will now also anticipate any higher risk of the ship being hit by dust particles. That doesn’t mean they’ll be able to prevent them — however, it allows them to brace for impact:
Where would a responsible commander have the crew members go inside the ship if she must factor in that the lasers might not be able to vaporise all the dust particles in this dense cloud during the rotation process? Would they be safer in the ring sections, or would the commander send everyone who isn’t needed elsewhere into the central trunk (“pipe”) of the ship, around which the rings rotate? Or maybe even to the front sphere of the ship, as it will be the first thing that no longer has to face the incoming barrage of interstellar particles?

2) The obvious alternative to “turning the ship around faster” would be “let’s keep coasting until we’ve passed the dust cloud, and only rotate the ship once we’ve made it through, at the intended rotation speed”. This would be the more cautious way of doing it, so I need to find a way to rule out this option in order to not make my commanding staff come off as reckless for deciding to turn the ship when it’s at its most vulnerable.
The easiest way would be to simply postulate that this dust cloud is so big that the ship would overshoot the target star by several decades if it kept coasting through the entire dust cloud. Even then, though, some could frame this as the preferable alternative to risking the lives of crew members.

Hence, if the commander decides, “this takes too long, we take the risk”, she could come off as selfish / impatient for prioritising getting to the destination star on time. Her own commitment to the mission is in fact more in line with “keeping everyone alive” than with “getting to the planet as fast as possible” — the latter would fit the pilot’s motivation, though, so I could let the pilot make that suggestion.



Two arguments that could convince the commander to take the rest of turning the ship around now and fast, rather than impatience on her own part, would be:

a) The current generation of crew members were promised they would be the ones to land on the surface of the planet. This is amplified by the fact that the commander raised the number of allowed (and suggested) children per family from 2 to 4 (the inciting incident of the plot).
If she now has to backpedal and say it will take much longer, and that this generation won’t be the one to land on the surface, after all — because they must overshoot the destination star in order to only brake once they’ve made it through the dust cloud — she will face a very disappointed and probably angry crew, because they were promised something else. The commander might also find herself having to take back the four-child policy (which would indeed go against her personal convictions).
Of course, all of this ends up backfiring, because the drive takes damage in this disaster, reducing its braking force, and thereby causing the ship to overshoot the target anyway — in fact, by a century. (This is something we developed in an earlier thread.)

On a thematic level: The commander could then conclude that she prioritised the crew’s well-being — their desire to be the ones to land on the surface — over the survival of everyone. This goes against her personal convictions (she’s all about “sacrifice of well-being in the name of preserving life”); however, her choice could be a result of listening to her bridge officers. Namely, the pilot and the navigator, both representing the “well-being” side of the argument.
With this quick-rotation move backfiring on everyone, it would incentivise the commander to not only double down on her own “survival above well-being” convictions, but it would also give her a reason to become less democratic in the wake of this event: If she hadn’t listened to her bridge staff, they would probably have overshot the target by just a few decades, not a century — and everyone would still be alive.

The “well-being” side, in turn, gets to point to an earlier situation, in which somebody suggested braking a little earlier so that the ship would be slow enough to one day pick up an ice deposit at the edge of the target solar system — extra water which could be stored in some of the depleted fuel/radiation-shielding tanks, and then pumped into the system to allow everyone a few more minutes of shower time per day. This is a suggestion that the commander rejected in order to make it to the target planet on time — after all, it was merely about convenience for the crew, a mere luxury, not essential to the success of the mission. However, in hindsight, if the ship had started braking that early, they would have turned around before even encountering the dust cloud.


b) The primary “selfless” reason to make it to the destination planet as quickly as possible is not what the crew members want, but what humanity back on Earth expects the crew of the generation ship to do: Colonise the planet to create a safe haven that more humans from Earth can escape to, before the impending gamma-ray burst from WR 104 hits the entire solar system.

Thus, there are still also good survival reasons to be “in a rush”. This is something a bridge officer on the “survival over well-being” side could invoke, while still arguing for “let’s turn the ship around now, and fast”. Same conclusion, different motivation. I think this would suit the commander’s first officer.


And the best part: For all the parallels I’ve set up between my ship and the Titanic (even though mine doesn’t get destroyed in this event), the course of events looks quite comparable: The Titanic crew used the fatal combination of “hard-a-starboard” and “reverse gear”; some have suggested the ship would have taken less damage even if it had passed through the iceberg head-on.
Turning the Exodus around in a rush and trying to brake, rather than coasting through the dust cloud at the previous speed while firing all lasers, is ultimately the decision that causes more damage to the ship. The Titanic parallels are also why I’d like to keep the part with the dust particle piercing the ship hull. However, that particle alone isn’t going to kill a lot of people (it doesn’t even have to kill anyone; it could just pierce a bunch of layers which then require quick fixing).

The damage to the ship’s structure as a result of rotating faster than intended is going to be the primary problem. If I set up the warning that the ship wasn’t built for this level of stress, that may give me some leeway to render the potentially ensuing problems as unpredictable. If the reader buys that, I can have a bunch of different, seemingly unrelated issues pop up on board, as a result of this fast turnaround: fires breaking out, pipes bursting, power cuts etc.

The cause is an external threat by the universe, but the consequences ultimately still stem from the characters’ decisions… Sounds like an optimal combination of what people commonly consider “good writing”.

As I’ve said: I really like where this is going now! It finally feels like all the pieces are coming together, both on a plot and character-motivation level / in-universe and on a thematic level.

 

[ShadowKraz]

wow... I'm already hooked on this trilogy and you haven't even published it yet. When you do, I hope you post something tagging me so I can rush out, buy a copy, mail it to you, and have you sign it. I'll include postage to get it back to me.

 

[DaveC426913]

The primary “selfless” reason to make it to the destination planet as quickly as possible is not what the crew members want, but what humanity back on Earth expects the crew of the generation ship to do: Colonise the planet to create a safe haven that more humans from Earth can escape to, before the impending gamma-ray burst from WR 104 hits the entire solar system.

Thus, there are still also good survival reasons to be “in a rush”

Ehh...

Except that the goal of a "safe haven" was met as soon as the ship left Sol system. They're safe from the GRB.

Their highest priority switches to ensuring they survive to establish planetfall and rebuild. It would be counterproductive to do anything that might risk their safe colonization - including rushing it.

 

[Strato Incendus]

That's why I said "safe haven that more humans from Earth can escape to". Obviously, the crew themselves are safe once they leave the Sol system - or, more accurately, the area of the cone of the gamma-ray burst (which is likely to extend a little beyond the Sol system).

However, the "duty" to even build the colony on the target planet in the first place - and do so quickly - arises from the responsibility the crew have to the people left on Earth. Otherwise, if it were just about their own survival, they could turn the generation ship into a permanent habitat, much like an O'Neill cylinder.

This gets more interesting once the crew must assume a different disaster struck Earth in the meantime - we've been going back and forth between the gamma-ray burst going off and a massive solar storm hitting Earth. Because now, the more individualistic people on the ship conclude their duty to the people on Earth - and thereby, their duty to the mission - has been rendered void. Whereas the more collectivist people on board conclude that it's now more important than ever that they ensure the survival of humanity - even if "humanity" only includes them.

wow... I'm already hooked on this trilogy and you haven't even published it yet. When you do, I hope you post something tagging me so I can rush out, buy a copy, mail it to you, and have you sign it. I'll include postage to get it back to me.

Thanks for your enthusiasm! Obviously, I will inform everyone on this forum if and when the first volume does eventually get released... the whole ship wouldn't exist without all of you.


So, getting back to these remaining to questions:

1) Where would a responsible commander have the crew members go inside the ship if she must factor in that the lasers might not be able to vaporise all the dust particles in this dense cloud during the rotation process? Would they be safer in the ring sections, or would the commander send everyone who isn’t needed elsewhere into the central trunk (“pipe”) of the ship, around which the rings rotate? Or maybe even to the front sphere of the ship, as it will be the first thing that no longer has to face the incoming barrage of interstellar particles?

2) The obvious alternative to “turning the ship around faster” would be “let’s keep coasting until we’ve passed the dust cloud, and only rotate the ship once we’ve made it through, at the intended rotation speed”. This would be the more cautious way of doing it, so I need to find a way to rule out this option in order to not make my commanding staff come off as reckless for deciding to turn the ship when it’s at its most vulnerable.
The easiest way would be to simply postulate that this dust cloud is so big that the ship would overshoot the target star by several decades if it kept coasting through the entire dust cloud.

Question 1) assumes they've already decided to turn the ship within the dense dust cloud;
Question 2) is the more pressing one - the last remaining puzzle piece - as this is the one potential plot hole that will prevent the reader from believing any of this if I don't address it.

 

[ShadowKraz]

Question 2) is the more pressing one - the last remaining puzzle piece - as this is the one potential plot hole that will prevent the reader from believing any of this if I don't address it.

I think your postulate, that the cloud is much bigger than was previously estimated, is the best solution. I would point out, however, that coasting through it before turning the ship could be the factor that causes the crisis.
In order to not over shoot the destination, perhaps they use higher thrust and therefore expose the ship's structure to higher stresses than designed for... possibly causing several breakages or mis-alignments. Even a short period of higher thrust could cause these. The fire(s) could break out due to this; the fire systems fail or are at reduced function, other systems fail or have reduced function, etc. The higher g-force the crew experiences while trying to deal with these issues could lead to accidents among all of the repair crews. You won't need to have one big accident, but many smaller accidents.
Just spitballing while the coffee kicks in.

 

[Strato Incendus]

I think your postulate, that the cloud is much bigger than was previously estimated, is the best solution.

While beginning to write the scene where the characters first discover the cloud, I started wondering whether this dust cloud might be to the destination star system what the Oort cloud is to the Sol system?

At the point of encountering the dust cloud, the ship has 25 years left to go, according to the original plans. The last 25 years are the braking phase, just like the first 25 years were the acceleration phase. Based on the Relativistic Rocket calculator, the ship would cover 1.5 light-years during the acceleration phase, and the same distance during braking, for a total of about 3 light-years under power. Meaning, they discover the dust cloud at roughly a distance of 1.5 light-years to the destination star.

1.5 light-years is about the distance of the Oort cloud from Earth - this is in fact crucially relevant for the second prequel, where someone attempts to destroy the ship by having it collide with some object in the Oort cloud.

Of course, a G-type star like the sun may have a larger cloud, compared to an M-type red dwarf like Teegarden's Star. So the question is whether 1.5 light-years away from Teegarden's Star, the ship would already run into the outskirts of this star's "Oort cloud". I discovered that red dwarf stars have a much higher surface gravity than the sun; however, I'm not sure whether this would somehow still affect matter so far away from the star?

I would point out, however, that coasting through it before turning the ship could be the factor that causes the crisis.

Thanks for the alternative suggestion! ;) I think this is contingent on my question described above?

Since if this dust cloud isn't just "a random obstacle in space", but already marks the beginning of the Teegarden system, chances are the density of matter per unit of space is going to increase, the further the ship ventures into the Teegarden system, right?

 

[gmax137]

I discovered that red dwarf stars have a much higher surface gravity than the sun; however, I'm not sure whether this would somehow still affect matter so far away from the star?

The high surface gravity is due to the small radius of the star. At solar system distances the low mass of the red dwarf means its effect on other bodies is less (compared to more massive stars such as our sun).

 

[Strato Incendus]

The high surface gravity is due to the small radius of the star. At solar system distances the low mass of the red dwarf means its effect on other bodies is less (compared to more massive stars such as our sun).

Thanks for the quick reply; indeed, I didn't really expect the surface gravity to still have an effect this far out - I was just hoping to somehow justify the range of this Oort cloud (and by "hoping", I mean "grasping at straws" ;) ).

Is there any way to calculate how close to an M-type red-dwarf star you'd have to get before encountering its equivalent of the Oort cloud (if it has one)?

 

[DaveC426913]

Of course, they will be expecting to encounter Teegarden's Oort Cloud so it can't exactly catch them by surprise. It would be a mission planning flaw to wait until they were almost on top of the target system's outer cloud to do their turn around procedure.

Here is a question: if some fraction (50%?) of the journey is spent coasting, when is the optimal time to turn the ship, all factors considered? As soon as feasible, as late as feasible? Somewhere in the middle?

 

[Strato Incendus]

I'm glad you once again independently from myself came up with the same follow-up question that popped up in my head as I was writing this scene : Why not simply turn the ship around at the halfway point of the journey, in the interstellar medium, without having to brake right away?

The dust cloud can of course still be a problem, but only in the sense of "one speckle of dust might pierce the ship hull" - i.e., exactly what I had happen so far, except it would now not be happening while turning the ship around; rather, the ship would already be facing backwards, and the dust cloud would simply be so dense that it depleted the ship's own dust cloud, plus one speckle would also make it past the deflector lasers.

However, that once again restricts the damage the ship can take from the dust cloud to that of the impact of the speckle itself - the extra damage that turning the ship around too quickly would cause would now be off the table again, if the ship has already turned around several decades prior to that.


I guess I should have figured this idea sounded to good to be true... or rather, too good to actually work in the context of the story. Turns out, if you allow your characters to be smart within your head, they will try everything in their power to prevent the disaster from happening. I feel like a dungeon master who is constantly being outsmarted by the characters of his playgroup... and these characters don't even have other players steering them!

 

[ShadowKraz]

I feel like a dungeon master who is constantly being outsmarted by the characters of his playgroup... and these characters don't even have other players steering them!

Those darned players always screw things up! (long story about players outsmarting me by accident and completely ruining the dungeon)

As for the turn around...
the ship gets turned after the initial acceleration ends - it doesn't matter when, but we still have the issue with *something* going out of alignment and it doesn't get detected for the same reason as the kidney issue from post #49; it doesn't get detected because it doesn't look or act out of alignment with no acceleration applied. Once the braking acceleration is applied... it goes out of whack and crisis commences.
Yes, I know, design, engineering, and quality control are tight but errors and sabotage do happen even under the tightest regimes. Maybe sabotage during construction?

Yeah, I am kinda married to the idea. Tell me, however, to give it up and I will.

 

[gmax137]

As for the turn around...
the ship gets turned after the initial acceleration ends - it doesn't matter when

Maybe over the generations the "turn around" takes on a kind of religious or faith-based aura. Some people want to do it as soon as the coast period begins, others want to wait, others think it signifies a lack of trust in the grand plan.

 

[DaveC426913]

the ship gets turned after the initial acceleration ends - it doesn't matter when,

The mission would be planned to turn the ship around at the optimal time, whch is not necessarily right after the onset of the coasting leg.

The question is: what factors would or could arise duing that time that should be taken into account. Obviously, safety of the ship and crew are paramount, but what occurences could be anticipated that might require the ship to remain in Acceleration Mode? Are there alternate mission configurations? Say, a backup in case higher-rez data of the taget system shows it to be uninhabitable? Do they account for interlstellar dust couds and be ready to go around them? (Note that whether they do or not, isn't the point. The point is what would they be planning for in Mission planning?)


It's not a great analogy, but when I am out sailing, and it's time to come in to the harbour, I switch to my motor and drop the sails. Despite the fact that I won't be needing the sails, it is my habit to not lash down and store the sails until I am at-dock. The reason for this is as a backup, in case my motor dies at the worst possible moment. I need to be able to raise the sails at a second's notice if I suddenly find myself drifting toward a lee shore. That's the kind of precautionary wisdom that has kept sailors alive.

This can be generalized to a principle about any shipboard activity: what if I do this now? What is the worst that can happen? What if I do it later? What is the worst that can happen? If there is no upside to stowing my sails early, but a very definite downside (no matter how unlikely), then the advantage weighs in favour of holding off.

But that works the other way for other tasks. Some tasks you want to do right away in case something unexpected happens. For example, reefing the sail (ie. shortening it) in anticipation of high winds. It is always better to reef early and decide to take it out if winds don't build (big upside, small downside), than it is to wait and have to reef in rising winds (small upside, very big downside).

 

[ShadowKraz]

The mission would be planned to turn the ship around at the optimal time, whch is not necessarily right after the onset of the coasting leg.

The question is: what factors would or could arise duing that time that should be taken into account. Obviously, safety of the ship and crew are paramount, but what occurences could be anticipated that might require the ship to remain in Acceleration Mode? Are there alternate mission configurations? Say, a backup in case higher-rez data of the taget system shows it to be uninhabitable? Do they account for interlstellar dust couds and be ready to go around them? (Note that whether they do or not, isn't the point. The point is what would they be planning for in Mission planning?)


It's not a great analogy, but when I am out sailing, and it's time to come in to the harbour,

Excellent points and I think the sailing analogy is good. I used to sail under Capt. Bligh... um, I mean, my Dad. He was ALWAYS about doing, or preparing to do, things earlier than absolutely necessary, such as reefing the sails. The boat was an old O'Day Daysailer, but it was good practice for life.
"The best laid plans of mice and men oft go awry."

 

[Strato Incendus]

the ship gets turned after the initial acceleration ends

This would fit the goals of the youth rebel organisation in prequel 2, Turning Point, who are unhappy about having been turned into the first generation of unwilling crew members, and are trying to make the ship return to Earth.

Whether or not this goal is realistic or not is secondary (one forum user here has criticised a story with a plot like this as nonsensical in the past); Turning Point do not have to be guided by reason. In fact, their youthful passion may be the counterpoint to the ship's establishment, doing everything based on "the science".

However, even Turning Point understood that, if they wanted to have any chance at all to actually accelerate the ship back towards Earth, they'd have to turn it around before it reaches full coasting speed. After that, braking would merely cause it to get stranded in the interstellar medium.

Thus, their time of trying to make the ship brake and turn around early coincides with it traversing the actual Oort cloud. Therefore, a lot of the things we've discussed so far are not irrelevant - they might merely become crucial for the second prequel, rather than for the first main book. :)


If the ship turns around right after leaving the Sol system, the question is whether this happens as an intentional action on part of the ship's commanding officers - or if this is the consequence of Turning Point's actions: They may have succeeded in flipping the ship early (and perhaps, faster than they should have, given they were about two dozen plucky teenagers and twenty-somethings), but were stopped by security before they were able to complete their plan.

Then again, this doesn't make sense, as turning the ship around while it's accelerating will make it veer off course. This is one crucial difference to flipping the ship at the end of the coasting phase, since there is no continued acceleration as the ship is being rotated.

Thus, the more straightforward and believable explanation would be that the ship was rotated on purpose by the ones in charge, early after leaving the Oort cloud - which is simultaneously shortly after ending the acceleration phase - once they had entered the interstellar medium, where a lot less space dust could get in their way.

If they don't flip the ship right there and then, the question is indeed, as @DaveC426913 has asked:
What would be the upside of flipping it at the midpoint of the coasting phase, or even later?
Or conversely, what would be the downside of flipping it early?

 

[pinball1970]

So the question is:
1) How does fire behave in zero gravity vs. in an environment of centrifugal gravity (=on the ring sections of the ship)?
2) What safety technology would the ship have against cases like this (maybe starting with whatever the ISS has for preventing fires on board)?
3) What levels of casualties would you expect, assuming a bunch of people are sent in to extinguish the fire as quickly as possible?

Looking for holly wood portrayals I came across the Apollo 1 accident in 1967.
Not something I was aware of till I saw the Apollo 1995 film.

If you want to take from real life.

The craft was on the ground doing tests and the fire started, the crew were dead before engineers could get the doors off which was 5 minutes later.

V50 mentioned the sub fire, I cannot imagine many things more horrific, trapped in an enclosed space with a fire rapidly spreading.

The “Gravity” fire was pretty cool looking, imagining this was not.

 

[Strato Incendus]

Thanks for getting us back to the main topic! ;) After all, we have been talking more about the origin of the damage to the ship, rather than about what the damage occurring inside the ship will actually look like.

To recap: The dust-cloud explanation is a good way of justifying why a dust speckle may pierce the ship at this specific point in time (rather than at any earlier point over the course of the coasting phase) — namely, because the ship enters the outskirts of the Oort cloud of Teegarden’s Star. If I set this up properly, not only should it feel less like plot convenience, but actually more like straight-up realism:
(“Yes, of course, once they enter the new star system, the density of matter per unit of space will increase, compared to the interstellar medium, because of the star’s gravity.”) Thinking about it, re-entry into a star system at full coasting speed (0.125 c) should be more dangerous, compared to accelerating out of a star system into the interstellar medium from a lower speed (assuming the low g forces that we’ve established for the acceleration, which is 0.048 m/s2).

However, ultimately, the damage done to the ship must probably occur from the dust speckle alone, rather than from the rotation process. Since my conclusion from the comments so far is that the ship would realistically be rotated at an earlier point in the story, while it is somewhere in the interstellar medium, so the risk of damage is lower. In fact, the exact point in time when to rotate the ship could be determined by noticing, “We’re in a particularly empty pocket of space right now, let’s use the opportunity to flip the ship!”

The ship’s range of vision is fairly limited, though, due to its own travel speed (0.125 c) compared to the speed of its sensors (1 c).

Hence, as far as how quickly the crew notices the higher density of the dust cloud:

1. With the ship coasting at 0.125 c, they would cover 1 light-minute of distance within 8 minutes of ship time. The sensor signals can only work at light speed, so for any given speckle of dust in front of the ship, it would take one minute for the sensor signal to reach it, another minute for the reflected signal to get back to the ship. That would only leave the ship crew a time window of 6 minutes between first noticing the dust cloud and entering into it, right? Of course, they will expect the dust to get denser in general as they approach the target system. However, it may not be until they get the sensor data that they realise it’s denser than they anticipated.
2. The deflector laser beams obviously can’t move faster than light either, so even if they failed completely, after having vaporised everything perfectly up to that point, the ship would have 8 minutes of reaction time left before encountering further dust speckles, correct?
3. The higher density of the dust cloud as they enter the target star system no longer requires a failure of the deflector lasers in order for something to slip past, as @DaveC426913 pointed out. However, if the density of dust alone is what causes the problems now (rather than flipping the ship within such a dust cloud), I need an explanation why the ship doesn’t keep getting hit by more and more dust particles over the course of the story from then on.
   1. Perhaps some genius engineer makes a modification to the deflector lasers on the fly — perhaps within that critical time span of 8 minutes, before further impacts occur? Bonus points if the engineer sacrifices himself in the process. Perhaps he has to go to the back of the ship (which is now pointing forward) to manually adjust something on the deflector lasers?
   2. Spacewalks at this speed aren’t really possible, I’ve heard — however, that’s assuming a spacewalk that a character would survive. If he has to go outside to do something manually, he could die by radiation (because he’d be in front of the protective water tanks in the forward-pointing aft sphere), he could get pierced by the incoming barrage of dust speckles (even just a single one of them piercing his helmet would be enough), he could get fried by the engines as they turn on to brake (though in this scenario, there’s no reason to start the 25-year-long braking process while a crew member is still working outside), or he could simply slip and float away from the ship (which is kind of the biggest cliché, but of course an omnipresent danger in space).

For the rest of the crew, we need to get back to the question what exactly gets damaged on the inside, by the dust speckle that pierces the ship hull. I could have someone get ripped to shreds by the dust speckle passing through them — depending on whether this is the fate that befalls the engineer or not (I don’t wanna pull this twice in the same event, because “law of diminishing returns” in writing :D ). But either way, the speckle alone isn’t going to cause mass casualties, because the ship isn’t sufficiently densely populated for that.

I still like the idea of the speckle piercing some tank or pipe that contains an explosive gas. All it has to do on top of that is to also damage some wiring close to it, then you get some sparks, and boom, fire onboard galore. The obvious candidate here would be hydrogen, but pure hydrogen is of course hard to store, and not what you would want for the nuclear-fusion reactor anyway.

So I guess we’ll finally have to dig into the specifics of different types of nuclear-fusion reactors next.
But first, let’s address the remaining questions about the dust speckle listed above.
Once we know how the dust speckle got into the ship, then we can focus on the inside and imagine all the damage it can cause on its way through the ship.

 

[DaveC426913]

so even if they failed completely, after having vaporised everything perfectly up to that point,

Um. Vaporizing everything doesn't make it disappear. The vaporized components contain the same kinetic energy as the unvaporized components (minus whatever the laser pulse imparted on them). Ideally, you'll want both the radiative energy and the physical components to disperse, out of the ship's path. Hopefully, what's left will be spread over a wider area of the ship's proximal defenses. Just one more headache for you.

 

[pinball1970]

Apologies if this has already been mentioned.

Another example of a fire on a space craft.

https://www.nasa.gov/history/25-years-ago-fire-aboard-space-station-mir/

This was a happy ending. Note how long it took to remove toxic fumes from the craft. The escape capsule Soyuz has no fire extinguishers apparently according to Tim Peake. They depressurize the vessel extinguishing the flames.

 

[Strato Incendus]

Um. Vaporizing everything doesn't make it disappear. The vaporized components contain the same kinetic energy as the unvaporized components (minus whatever the laser pulse imparted on them). Ideally, you'll want both the radiative energy and the physical components to disperse, out of the ship's path. Hopefully, what's left will be spread over a wider area of the ship's proximal defenses. Just one more headache for you.

Thanks for pointing this out! ;) On that note, let’s get back to the question of where the captain would send the crew members to be as safe as possible from the barrage, keeping the dumbbell-structure of the ship in mind: In case one or several dust speckles to pierce the ship hull, would citizens be safer in the central pipe, around which the rings rotate? Or would they be safer on the rings themselves?

The holes the speckles would punch into the ship hull are likely so small that they won’t allow a lot of air to escape into space that quickly, I assume? They would detect slowly dropping levels of air pressure, and would quickly send technicians to fix them.

If there are a bunch of speckles punching holes into the hull in different places, that would perhaps finally be one way of getting me to that “disaster which requires a lot of helping hands to fix, and is dangerous” scenario that I need, since it would incentivise the commander to send a lot of male officers “into battle against the universe”. Quite literally, in case some of them end up getting pierced by dust speckles themselves — getting hit by a bullet will seem harmless in comparison, given the speed of the speckles, and what they would do to the human body as a result (we’ve discussed that part before).

Apologies if this has already been mentioned.

Another example of a fire on a space craft.

https://www.nasa.gov/history/25-years-ago-fire-aboard-space-station-mir/

This was a happy ending. Note how long it took to remove toxic fumes from the craft. The escape capsule Soyuz has no fire extinguishers apparently according to Tim Peake. They depressurize the vessel extinguishing the flames.

In fact, it hasn’t! Thanks a lot for this real-world example! :) In particular, this is useful for thinking about “stuff that could ignite”.

The part about the route to the evacuation shuttle is not that useful in my setting, since getting to one of the generation ship’s landing shuttles is still a death sentence if you flee the ship while it’s still in the interstellar medium — you won’t arrive anywhere with those landing shuttles.

Even if the air inside them never ran out, you’d die of old age, much like the older generations on the generation ship itself — except you can’t raise your entire family inside such a shuttle. Even if several generations somehow could survive inside a shuttle, a single shuttle probably does not have enough fuel to decelerate it from the mothership’s 0.125 c coasting speed all by themselves, in order to eventually brake at the target star.

 

[DaveC426913]

...the question of where the captain would send the crew members to be as safe as possible from the barrage, keeping the dumbbell-structure of the ship in mind: In case one or several dust speckles to pierce the ship hull, would citizens be safer in the central pipe, around which the rings rotate? Or would they be safer on the rings themselves?

Def safer in the pipe.

The holes the speckles would punch into the ship hull are likely so small that they won’t allow a lot of air to escape into space that quickly, I assume?

At relativistic speeds, I'm not sure particles would drill holes so much as explode, vaporizing chunks of ablative shielding and leaving craters.

That is, after all, the point of shielding - to
1. absorb and spread the damage out laterally so it doesn't reach the inner hull
2. carry away the kinetic and heat energy with the ablated material.

 

[Strato Incendus]

Def safer in the pipe.

Perfect, thanks a lot! That allows me to keep my evacuation scene, where a security officer guides a bunch of school children away from the ring and to the elevators that lead to the central pipe.

At relativistic speeds, I'm not sure particles would drill holes so much as explode, vaporizing chunks of ablative shielding and leaving craters.

That is, after all, the point of shielding - to
1. absorb and spread the damage out laterally so it doesn't reach the inner hull
2. carry away the kinetic and heat energy with the ablated material.

Sure, and usually, the shielding works. The point is that the sudden increase in density at the outskirts of the star system becomes too much to handle for both the protective cloud in front of the ship (which is being depleted fast) and the deflector lasers, so something does get past.

"Craters", while more destructive than "tiny bullet holes", is still better than "micro-meteor", because the latter would probably be enough to destroy the entire ship. So perhaps, "craters" is exactly the level of destruction I need? How large exactly the craters would be will depend on the individual speckle, I assume - and since they're too small to be seen with the naked eye, the reader has no way of observing where the speckles are coming from.

Hence, I would conclude I can just place and shape my craters wherever I want on the ship, as long as the speckle trajectory makes sense? (Meaning, they should traverse the ship from aft sphere to fore sphere, since, as we established, the ship is already facing backwards at this point.)


Speaking of the ship's own protective dust cloud: How would this be used in conjunction with deflector lasers? Specifically, how can the ship stop its own deflector lasers from depleting its own gas cloud, rather than whatever natural interstellar dust is waiting beyond the ship's own protective dust cloud?