What can realistically go wrong on an interstellar journey?

[Strato Incendus]

Alright, since I’m still stuck on my sci-fi story because I can’t exactly outline the mid-point plot twist with a realistic catastrophe on board an interstellar spaceship, I thought I’d widen the scope a little — towards full-on open brainstorming:

What, if anything, can realistically go wrong on an interstellar journey?
(By “realistically”, I mean “without making any extra assumptions about aliens, unknown forces of physics etc.” — just based on what we currently know.)

I may have underestimated this challenge a little because, in real life, at least based on our current knowledge, there are of course several huge obstacles to interstellar travel: fuel and food supply, achieving a travel speed that makes the trip feasible (i.e., a significant portion of the speed of light), radiation, dust particles and micro-meteors, etc.

The problem is that all of these challenges are so big that, if a ship cannot handle them, there’s no point in it even leaving the solar system. For example, a micro-meteor hitting the ship out of nowhere mid-journey should not happen, because the ship will need some kind of deflector system anyway to deal with stuff like this countless times per day. And if it has a deflector system, but it randomly fails when the story needs it to, the resulting collision, given the intensity of the impact, for all I know wouldn’t just severely damage the ship, but would probably destroy it completely.

So these disasters are all kind of “too big”. When you have a story set on Earth, and you want to create a challenge for your characters, or come up with some catastrophe that leads to some severe casualties, you wouldn’t immediately jump to “meteor hits Earth and wipes out all mammalian life”, would you?

Once all of these major challenges are out of the way, though — those that wouldn’t even make the journey worth starting if they hadn’t been dealt with in advance — the emptiness of the interstellar medium, as well as the inability to stop without wasting fuel or exposing the crew to unsurvivable g forces, create a pretty non-interactive environment for any story set between two stars.

Even internal failures of the ship aren’t that easy to create. A hull breach, as it seems to happen quite frequently in Star Trek (or even more vividly in one episode of The Expanse), shouldn’t happen too easily, either: Not just because even minor collisions with dust speckles have to be avoided anyway; but also because the ship hull will have to be thick enough to shield everyone inside against radiation. And one effective way to do that is to place a layer of water between the hull and the interior.
Now it’s hard for any given crew member to just be “randomly blown out into space”, if there’s a thick wall of water in between. You could of course have that water seep into the ship, but most likely it would not happen in such quantities that anyone would drown in a corridor or something.

Radiation, even if the ship’s protective measures against it may fail to some reasonable degree, would be comparatively slow to kill humans — probably slow enough for the crew to notice the holes in the protective layers in time to patch them up.

Finally, deliberate human sabotage is also hard to justify — since anyone with such intentions is stuck on board the ship together with everyone else for the time of the journey. Even people with malicious intent still have survival instincts.

So, what likely “medium-size disasters” do we have available at all? It seems to me like I only have the choice between “something that would destroy the entire ship” and “nothing at all happens, because the ship can’t interact with anything around it”.

 

[Bystander]

Realistically? Every body changes their minds.

 

[Vanadium 50]

Interstellar travel is not realistic. So any modification of it won't be realistic either.

 

[anorlunda]

Think of the history of exploration and discovery on Earth. Many of those exploration ships disappeared and were never heard of again. Yet other ships kept trying.

I think that a flaw in your overall plan is that you think ships would not launch unless the chance of success was nearly 100%.

Also, I would expect that the number one reason for failure of space colony ships would be that there was no suitable place to land at the destination, or at the backup destinations.

But for an onboard disaster, how about a natural mutation in a virus causes a deadly disease to sweep through the crew?

Finally, deliberate human sabotage is also hard to justify — since anyone with such intentions is stuck on board the ship together with everyone else for the time of the journey. Even people with malicious intent still have survival instincts.

Think of just the most recent cases of mass shootings in America. The chance of survival for an active shooter is nearly zero. Some of them could be a variation of "suicide by cop."

 

[PeroK]

Interstellar travel? What could possibly go wrong?

 

[Strato Incendus]

Interstellar travel is not realistic. So any modification of it won't be realistic either.

Sure. We’re talking “conditional” realism here. Meaning “assuming we can find some ways to solve the K.O. criteria that, if left unsolved, wouldn’t even allow the mission to get off the ground”, which major problems can still occur along the way?

Realistically? Every body changes their minds.

That actually seems highly unrealistic to me — since I’ve yet to see a worldview on which *everyone* in a given society changes their minds.

But for an onboard disaster, how about a natural mutation in a virus causes a deadly disease to sweep through the crew?

A virus seems like the one go-to problem spaceship stories keep returning to. If you count all the generation ships in Elite: Dangerous, as far as I recall (there are videos on YouTube chaining the clips for all of those generation ships back-to-back), some virus-like thing always happens to be the most common. Meaning, it has become a trope at this point, if not a cliché.

I’m also wondering if we might be overestimating the likelihood of this occurring. In terms of crew size (anything between 1,000 and 2,000 people), I like to use the small island nation of Niue as an example (say, for how many doctors a ship would need — based on the report of a friend of my brother’s who went there, Niue has three physicians: a surgeon, a gynaecologist, and an anaesthesia specialist). It also fits nicely, since small island nations tend to be comparatively isolated.

I’ve googled a bit, but I couldn’t find any reports of virus epidemics or similar on the island. For Covid, they’ve had 104 cases total, 0 deaths. And island nations can at least still have some traffic exchange with other countries. An interstellar spaceship wouldn’t have any people going in and out of it at all.

 

[anorlunda]

I think we are wasting our time offering you suggestions.

 

[Vanadium 50]

Sure. We’re talking “conditional” realism here.

Then this just becomes a guessing game - "what do you think I would think is realistic"?

If the way you make interstellar realistic is the MacGuffin Drive, then your "realistic" answer is "a failure of the MacGuffin Drive."

 

[bob012345]

Is this a generation ship? People might lose interest in reproducing midway.

 

[Vanadium 50]

people might lose interest in reproducing

I think "realistic" precludes that.

 

[jrmichler]

What, if anything, can realistically go wrong on an interstellar journey?

1) Failure of the life support system. Consider the biodiversity of Planet Earth to that of your science fiction life support system. Biodiversity is what removes dead animal skeletons and teeth, deer antlers, turtle shells, and similar from the environment. Biodiversity keeps the system working when a particular pest (Dutch Elm disease, emerald ash borer, oak wilt) kills an entire species. Then think about what could go wrong.

2) A spaceship is a container full of air under pressure. Air will always leak out. How much spare air, how is it stored, what is the leak rate, and what happens if your design leak rate is less than the actual leak rate.

 

[bob012345]

I think "realistic" precludes that.

Oh, I don't know. Perhaps when the thrill of a new and historic adventure gives way to the realization that people are trapped for the rest of their lives in a tin can in the cold, dark expanse of infinite space, they may lose interest in everything.

 

[Strato Incendus]

As always, thanks for your many ideas!

I think we are wasting our time offering you suggestions.

No, you just happened to be the first person to make a particular suggestion - and it happened to be what I considered the most frequently used one. It was still good you brought it up - because the fact that this was the first idea mentioned in this thread actually supports my claim that an onboard virus is the "Ockham's razor" solution that a lot of authors tend to resort to.

Is this a generation ship? People might lose interest in reproducing midway.

Yes, in my case, it is a generation ship - and falling birth rates are indeed the core of the problem. I didn't mention this in the opening post for two reasons:

1) I've already created a bunch of threads on generation ships, and since it seems to be a fairly specific sub-genre, I didn't want to bother people with more of the same. In contrast, interstellar travel is a wider scope of potential problems, many of which should also apply to people writing about FTL spaceships. Thus, a thread that isn't specific to the problems of generation ships allows more people to contribute, and in turn, the results of this brainstorming session should also be useful to more people than just those of us who write about generation ships.

2) The falling birth rates on my generation ship are the overarching problem. However, I still need other problems to occur in the plot in order to slowly up the stakes of this overarching problem. In other words: External pressures that increase the need for the crew to reproduce (such as any kind of disaster that causes considerable casualties - without destroying the entire ship).

Without any such external space events influencing the society inside the ship, the story could just as easily take place on Earth. Then you'd get something in between "The Handmaid's Tale", "Equals", "The Giver" etc. If you take that concept and apply it to a generation ship, you get "Voyagers".

Interestingly, a lot of these "Grimbright" stories use the trope of having to suppress the crew's / citizen's emotions. To me, though, that's a quick and easy (and therefore cheap) trick to make a futuristic society totalitarian - and one which, when it comes to raising birth rates, is of course counter(re-)productive.

If you think of the genre founder Brave New World, there the preferred method of societal control is actually the opposite: Using people's susceptibility to various kinds of pleasure to keep them docile and compliant.

I think "realistic" precludes that.

The problem is of course not that the crew as a whole lost interest in reproducing - they just don't do it at the rate the ship's commander would like to see (in terms of what she considers vital for the success of the mission).

If the way you make interstellar realistic is the MacGuffin Drive, then your "realistic" answer is "a failure of the MacGuffin Drive."

Yes, we have discussed the idea of drive failure in a previous thread. Counter-intuitively, unless this failure happens at the start of the mission, this wouldn't actually lead to the ship stranding between the stars right away, though: Rather, once the ship is already coasting (=no longer accelerating), a failure of the drive would prevent it from slowing down again.

This would cause the ship to zip past its target star - and only after that could it get lost in between the stars. But until then, the crew would still have lots of time to solve the problem: In order to brake at g forces the human body can withstand over a long time, and still get the ship to slow down from relativistic speeds, it would have to start braking several years, if not decades in advance. (One friendly user here actually calculated this for my ship, with an acceleration phase and braking phase of 25 years each, and g forces in the range of ISS reboosts.)

1) Failure of the life support system. Consider the biodiversity of Planet Earth to that of your science fiction life support system. Biodiversity is what removes dead animal skeletons and teeth, deer antlers, turtle shells, and similar from the environment. Biodiversity keeps the system working when a particular pest (Dutch Elm disease, emerald ash borer, oak wilt) kills an entire species. Then think about what could go wrong.

2) A spaceship is a container full of air under pressure. Air will always leak out. How much spare air, how is it stored, what is the leak rate, and what happens if your design leak rate is less than the actual leak rate.

The biodiversity issue is an interesting one I hadn't thought of yet. Of course, I thought about maintaining genetic diversity among the human crew, as well as the need for lab animals to test medicine etc. (Animals for meat consumption are not required anymore, and would actually be an inefficient way of obtaining food, if lab-grown meat is available as an alternative - much like vertical farming is more efficient than traditional farming, especially since it means the ship doesn't have to carry around all that extra soil.) I wasn't quite sure yet about pets on the ship.

Your proposal 1) raises the idea that perhaps the ship should deliberately contain many different species - thus bringing it even closer to the concept of an Ark. (My ship already has the little gimmick that there's at least one couple from each country.) On the flipside, of course, where biodiversity on Earth ensures that "life itself will survive", biodiversity on a ship doesn't accomplish much, if none of the other species are capable of completing the mission. Then it will just be a massive tin can full of animals that will keep wandering through space until eventually the lights go out.

So the question is: What use would this larger on-board biodiversity have for the human crew if they went extinct? And therefore, (why) would they expend the additional resources to feed all of these animals on board?Point 2 is about the problem of hull breaches I mentioned in the starting post. These are of course a common, but believable way to have some casualties among the crew. As I said in the starting post, my main question here is: How much of a hull breach can a ship really have a) without external collisions causing them, and b) breaches large enough to cause human casualties before they can be fixed?

If, say, some of the protective layer of water that shields the inside from radiation were to leak out into space, the ship would certainly have water-tight compartments that could be sealed (even the Titanic had these already), so that only a small chamber worth of water would get lost. I don't see any crew members being blown out into space through such a breach. The area that lost its water shield would be exposed to radiation, of course, and would be off-limits to visit without protective suits etc. But ultimately, this leak would remain some minor damage on the ship, and perhaps not even a single life would be lost as a result of it.

In terms of storytelling stakes, this would make it "barely an inconvenience", as the guy on Pitch Meetings likes to say.

I could of course have a chain of failures - that's how most catastrophes happen in real life, after all: There are multiple layers of safety measures in place, and only if several of them fail at once can a big disaster occur. In this example, the water-tight compartments not shutting properly after a leak, and a majority of the protective water shield getting lost. As a result, almost the entire ship would be exposed to radiation.

The problem with that is, again, that it's too big of a problem - because there would almost be no way for the crew to survive anymore at this point. Especially since the water cannot be retrieved, and slowing down to pick up floating ice chunks etc. is not possible.

Thus, many of the challenges an interstellar spaceship would face seem to jump from 0 to 100 pretty quickly. As storytellers, however, we need medium-sized, somewhat solvable challenges for our characters. Something in between "barely an inconvenience" and "total annihilation".

Oh, I don't know. Perhaps when the thrill of a new and historic adventure gives way to the realization that people are trapped for the rest of their lives in a tin can in the cold, dark expanse of infinite space, they may lose interest in everything.

Yes, the crew losing their sense of purpose is another potential problem - and indeed an example of something that not just a generation ship would face. Even a ship that complete a journey to a nearby star at relativistic speeds in a span of about, say, 20 years could still experience this issue.

Trope-wise, this often seems to be connected to a loss of information about the mission's original purpose - the old Nietzschean spectre. I actually think it's more interesting if the crew loses their sense of purpose in full possession of this information: Precisely because they know how long the journey is, and how small their individual contribution to it (there we are back with the "Grimbright" genre).
TL;DR: Some of your suggestions go into the direction of what I have in mind for the second volume of my trilogy. This is encouraging, because the second volume is the one I'm least confident about so far - in terms of stakes - compared to part I and part III.
The fact that you came up with these suggestions independently of me (a ship zipping past its destination star; the crew losing purpose etc.) gives me hope that these further issues the ship could be facing after the mutiny in part I are indeed not just believable - but also serious enough to warrant a book of its own about how to address these follow-up problems.

Right now, however, I'm still looking for a medium-size cosmic disaster to happen to the crew during part I, in order to up the stakes for the overarching problem of low reproduction rates on a generation ship.

One would think that Star Trek already offered plenty of ideas of what external events could happen to a spaceship to put it in danger. But when you remove all of the scientifically shaky staples of sci-fi, namely aliens and FTL travel, and are dealing with a slowboat that's mainly surrounded by nothingness, coming up with such an external threat immediately becomes a lot harder.

 

[phyzguy]

Oh, I don't know. Perhaps when the thrill of a new and historic adventure gives way to the realization that people are trapped for the rest of their lives in a tin can in the cold, dark expanse of infinite space, they may lose interest in everything.

I hate to break it to you, but YOU are trapped for the rest of your life on a small ball of rock in the cold, dark expanse of infinite space.

 

[Strato Incendus]

I hate to break it to you, but YOU are trapped for the rest of your life on a small ball of rock in the cold, dark expanse of infinite space.

Shhh... don't give away the "secret" implications of my story.
I'm creating this ship in the spirit of Star Trek, merely so that people don't immediately notice how I'm trying to make them all miserable from behind the scenes...

In all seriousness, this obvious comparison between the state of an interstellar spaceship (especially a generation ship, because it makes "normal" family life a core element of its mission) and Earth is where the majority of the appeal of the sub-genre comes from.

 

[bob012345]

I hate to break it to you, but YOU are trapped for the rest of your life on a small ball of rock in the cold, dark expanse of infinite space.

Not true at all. We have the gift of sunlight to warm and cheer us as well as the wide expanse of land, sea and sky. Plus, we can move off this globe and have many nearby places to go. And if we do venture out into cold, dark space where will we likely go? To another sun warming its own planets with land and sky and perhaps even seas.

 

[pinball1970]

Alright, since I’m still stuck on my sci-fi story because I can’t exactly outline the mid-point plot twist with a realistic catastrophe on board an interstellar spaceship, I thought I’d widen the scope a little — towards full-on open brainstorming:

What, if anything, can realistically go wrong on an interstellar journey?
(By “realistically”, I mean “without making any extra assumptions about aliens, unknown forces of physics etc.” — just based on what we currently know.)

I may have underestimated this challenge a little because, in real life, at least based on our current knowledge, there are of course several huge obstacles to interstellar travel: fuel and food supply, achieving a travel speed that makes the trip feasible (i.e., a significant portion of the speed of light), radiation, dust particles and micro-meteors, etc.

The problem is that all of these challenges are so big that, if a ship cannot handle them, there’s no point in it even leaving the solar system. For example, a micro-meteor hitting the ship out of nowhere mid-journey should not happen, because the ship will need some kind of deflector system anyway to deal with stuff like this countless times per day. And if it has a deflector system, but it randomly fails when the story needs it to, the resulting collision, given the intensity of the impact, for all I know wouldn’t just severely damage the ship, but would probably destroy it completely.

So these disasters are all kind of “too big”. When you have a story set on Earth, and you want to create a challenge for your characters, or come up with some catastrophe that leads to some severe casualties, you wouldn’t immediately jump to “meteor hits Earth and wipes out all mammalian life”, would you?

Once all of these major challenges are out of the way, though — those that wouldn’t even make the journey worth starting if they hadn’t been dealt with in advance — the emptiness of the interstellar medium, as well as the inability to stop without wasting fuel or exposing the crew to unsurvivable g forces, create a pretty non-interactive environment for any story set between two stars.

Even internal failures of the ship aren’t that easy to create. A hull breach, as it seems to happen quite frequently in Star Trek (or even more vividly in one episode of The Expanse), shouldn’t happen too easily, either: Not just because even minor collisions with dust speckles have to be avoided anyway; but also because the ship hull will have to be thick enough to shield everyone inside against radiation. And one effective way to do that is to place a layer of water between the hull and the interior.
Now it’s hard for any given crew member to just be “randomly blown out into space”, if there’s a thick wall of water in between. You could of course have that water seep into the ship, but most likely it would not happen in such quantities that anyone would drown in a corridor or something.

Radiation, even if the ship’s protective measures against it may fail to some reasonable degree, would be comparatively slow to kill humans — probably slow enough for the crew to notice the holes in the protective layers in time to patch them up.

Finally, deliberate human sabotage is also hard to justify — since anyone with such intentions is stuck on board the ship together with everyone else for the time of the journey. Even people with malicious intent still have survival instincts.

So, what likely “medium-size disasters” do we have available at all? It seems to me like I only have the choice between “something that would destroy the entire ship” and “nothing at all happens, because the ship can’t interact with anything around it”.

Fire and or explosion. Two shuttles and two Apollo accidents so realistic in that sense.
I have not read every response but virus was mentioned, perhaps from research taking place on the ship?

 

[Vanadium 50]

What can realistically go wrong on an interstellar journey?

Run out of beer.

 

[gmax137]

Charismatic crewmember has a spiritual episode; proselytizes gaining converts. Conversion of entire crew would derail the mission, the guru and followers is the threat.

 

[Strato Incendus]

Fire and or explosion. Two shuttles and two Apollo accidents so realistic in that sense.

Coincidentally, I was just wondering about the opposite: Drowning in space (specifically, inside your space suit) is also a real danger, one which has both almost happened in real life (I saw the case of an astronaut named Luca, who fortunately ended up surviving this), and in fiction (such as in the space horror film “Life”).

I’m not necessarily planning to reuse this trope — mainly because spacewalks at relativistic coasting speeds may simply be impossible. However, given the large amounts of water my ship needs to have on board, and given that we’ve talked about the danger of leaks already, what would happen if some people got trapped inside a bubble of water that has leaked into the ship?

Going by ISS footage, the water would of course arrange itself into a perfectly spherical bubble. However, of course the water bubbles in these ISS demonstrations are very small. If enough water leaked into the ship, however, the resulting bubble could become large enough for somebody to drown within it.

If some people got trapped inside such a human-sized water bubble, could they swim out of it? Or would the water move along with them, keeping them trapped inside?

 

[pinball1970]

Coincidentally, I was just wondering about the opposite: Drowning in space (specifically, inside your space suit) is also a real danger, one which has both almost happened in real life (I saw the case of an astronaut named Luca, who fortunately ended up surviving this), and in fiction (such as in the space horror film “Life”).

I’m not necessarily planning to reuse this trope — mainly because spacewalks at relativistic coasting speeds may simply be impossible. However, given the large amounts of water my ship needs to have on board, and given that we’ve talked about the danger of leaks already, what would happen if some people got trapped inside a bubble of water that has leaked into the ship?

Going by ISS footage, the water would of course arrange itself into a perfectly spherical bubble. However, of course the water bubbles in these ISS demonstrations are very small. If enough water leaked into the ship, however, the resulting bubble could become large enough for somebody to drown within it.

If some people got trapped inside such a human-sized water bubble, could they swim out of it? Or would the water move along with them, keeping them trapped inside?

So lots of options, you have machines, fuel, people, radiation, animals/disease if you have a lab and water.
101 ways to die in space.

 

[PeroK]

What about if the ship picked up what it thought was a distress signal from a nearby planet and sent a shuttle down to the surface to help ...?

 

[pinball1970]

What about if the ship picked up what it thought was a distress signal from a nearby planet and sent a shuttle down to the surface to help ...?

Erm...

 

[DaveC426913]

It could be as simple as a paucity of a vital atomic micro-nutrient.

What if, for example, they didn't include enough vanadium, and have no way of getting more?

 

[256bits]

Run out of beer.

Likely not too far off.
How many re-runs of of Titanic, or The Three Stooges can one realistically endure
Endless boredom will creep in.

 

[DaveC426913]

_{...but it wasn't supposed to be funny,...}

 

[pinball1970]

View attachment 317817

_{...but it wasn't supposed to be funny,...}

I thought you were going to expand on it. Perhaps the third and fourth generation of kids without Vanadium had evolved without the ability to understand sarcasm or something.
By the time the older people realised what was happening they tried a meme approach and started showing them endless episodes of Mash and Frazier.

 

[DaveC426913]

Are you thinking of Valium??

Vanadium is element 23.

It is (according the source I used to make that infographic*) the least abundant element (0.11 micrograms) that has a known biologic role in the human body.

*

 

[DaveE]

Contractors built substandard storage tanks that are now starting to leak. Water, LOx, etc. Then you get to choose why, how fast, what consequences, etc.

Edit: Better yet faulty maintenance on the journey. The the culprit is still onboard. Sabotage, incompetence, bad management, false accusations, distrust amongst the crew...?

 

[pinball1970]

Are you thinking of Valium??

Vanadium is element 23.

View attachment 317818

It is (according the source I used to make that infographic*) the least abundant element (0.11 micrograms) that has a known biologic role in the human body.

*
View attachment 317820

You said Vanadium I said Vanadium. We all said Vanadium. The funny part reminded me of a poster ID, cant recall who right now.
It was funny in my head anyway

 

[Vanadium 50]

Say his name three times and he will appear.

 

[Drakkith]

What, if anything, can realistically go wrong on an interstellar journey?

The same things that can go wrong anywhere else. Everything.

The problem is that all of these challenges are so big that, if a ship cannot handle them, there’s no point in it even leaving the solar system.

When it comes to airplanes, ships, spacecraft , etc, disasters don't usually happen because people knowingly design things that can't handle tough challenges, they usually happen because people thought that what they were building could handle the situation, but it couldn't.

Some component or system going on the fritz halfway through a multi-generational voyage through space isn't bad storytelling or handwaving, it's an entirely plausible situation that is similar to those which have plagued engineers and production companies throughout all of history. Things break. Often unexpectedly and when they shouldn't. The bigger, more powerful, or more complicated the thing, the bigger the problems (and often fireworks) when it breaks.

Even internal failures of the ship aren’t that easy to create. A hull breach, as it seems to happen quite frequently in Star Trek (or even more vividly in one episode of The Expanse), shouldn’t happen too easily, either: Not just because even minor collisions with dust speckles have to be avoided anyway; but also because the ship hull will have to be thick enough to shield everyone inside against radiation.

Then you have a boring ship, a lack of imagination, and/or an unwillingness to handwave away something that should be mostly unimportant in its details. Unless you are writing a story about an engineer investigating the details of how some component failed, and those details are actually very important to the story, then just blow open a hole in the ship, start a fire somewhere, have a group of teens go on a rampage, make the captain go crazy, or use any of a million other possibilities.

Finally, deliberate human sabotage is also hard to justify

Human sabotage is quite possibly the easiest thing to justify, because it doesn't have to make logical sense or require that you make a leak-proof case about why some critical system blew up at an inopportune moment. I can literally start a story with this premise with no problem. I'll do it right now.

Bob turned over, grabbed his wrench from under his pillow, and hit his alarm clock as hard as he could. Yawning, he got up, wrench in hand, and went to his clothes locker in the corner of the room where he dressed. Afterwards he brushed his teeth, tossing his wrench into the air over and over again with one hand while he brushed with the other. He spit, rinsed, and then smiled into the mirror above the sink.

"Today's the day." He said quietly. "Today's the day they all meet the real me."

Bob chuckled and then turned around and walked to the door. He hit the open button and would, in a very short time from now, walk into the pages of history as the Wrenching Wreckman of Wickerson Way. Wickerson Way being the name of the ship he was about to empty of all life. Happy wrenching, Bob!

Granted, this particular style probably isn't what you're going for, but I'm using it to illustrate that there need not be any real justification at all. "And then someone blew themselves and half our food out of an airlock" is a perfectly good way of introducing a problem for your cast of characters to overcome.

The fact that people often do awful, terrible, illogical things is so well understood that your audience rarely requires an explanation as to why.

 

[Jarvis323]

Basically, it is difficult to engineer machines to be able to handle the unexpected. Humans with general intelligence ameliorate the problem by being able to assess an unexpected situation and respond with ingenuity. But humans, with their general intelligence, are imperfect, inexact, make mistakes, take risks, and become corrupted. Maybe an advanced AI could achieve a general intelligence more suitable for handling problems encountered on interstellar missions than people, but who knows how successful that will be, and as the author it’s your choice anyways.

Also, I personally don’t think that interstellar travel is unrealistic, not even by todays technology. Although, I see why people think it is unrealistic. I also think it is unrealistic that future civilizations will be limited by our current technology. Besides, our observational evidence suggests to some (depending on the interpretation how much) that game changing technology may actually exist already. The truth is that “realistic” is relative to the observer. Feasibility, or difficulty rather, is unknown in my opinion.

 

[pinball1970]

Basically, it is difficult to engineer machines to be able to handle the unexpected. Humans with general intelligence ameliorate the problem by being able to assess an unexpected situation and respond with ingenuity. But humans, with their general intelligence, are imperfect, inexact, make mistakes, take risks, and become corrupted. Maybe an advanced AI could achieve a general intelligence more suitable for handling problems encountered on interstellar missions than people, but who knows how successful that will be, and as the author it’s your choice anyways.

Also, I personally don’t think that interstellar travel is unrealistic, not even by todays technology. Although, I see why people think it is unrealistic. I also think it is unrealistic that future civilizations will be limited by our current technology. Besides, our observational evidence suggests to some (depending on the interpretation how much) that game changing technology may actually exist already. The truth is that “realistic” is relative to the observer. Feasibility, or difficulty rather, is unknown in my opinion.

Sci fi aside. What is the radiation like in-between stars? Based on radiation we measure on earth? Also Voyager 1 and 2 and what they have detected since they left the solar system?

 

[Jarvis323]

Sci fi aside. What is the radiation like in-between stars? Based on radiation we measure on earth? Also Voyager 1 and 2 and what they have detected since they left the solar system?

Why do you think that is a deal breaker?

If the bar is “seems too costly or challenging”, then by that logic the pyramids shouldn’t exist either.