What would be the psychological effect on the inhabitants of a generational starship, if they discovered that powerful pirates were on course to intercept them 20 generations hence (~600 years), and there was no way to outmaneuver them?

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    $\begingroup$ For 19 generations people will say "Not my problem". Then the last generation will curse their ancestors. $\endgroup$ Commented Dec 28, 2015 at 8:07
  • $\begingroup$ Where is the ship? In a solar system or interstellar space? Where will the be when they meet? What speeds are we talking about? What resources do they have available? $\endgroup$ Commented Dec 28, 2015 at 14:53
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    $\begingroup$ Piracy is generally seen as a way to make a quick buck, not a long term plan for your descendants. What motivation do your pirates have in waiting so long to intercept this ship? Why would these descendants still be pirates in 600 years? $\endgroup$ Commented Dec 28, 2015 at 18:56
  • $\begingroup$ @Stig Hemmer lol! There is so much painful truth in what you say... $\endgroup$ Commented Dec 28, 2015 at 21:59
  • $\begingroup$ Are the pirates robotic/automated? $\endgroup$
    – Anixx
    Commented Dec 29, 2015 at 6:28

6 Answers 6


You can make some pretty giant course corrections in 600 years, so I am going to assume you mean that both you and the pirates will be in the target solar system in 600 years, making the question of doing a rendezvous somewhat simpler (in relative terms).

The most likely answer is the passengers and crew will do nothing. There are plenty of examples in our own history, for example the expansion of Welfare, Social Security and Medicare in the 1960's were all correctly predicted to be unsustainable even then, and now the United States (and indeed every Western nation which followed similar expansions of welfare and entitlement benefits) is essentially bankrupt, with an estimated $100 trillion in upcoming unfunded liabilities coming due as the "Boomer" generation reaches retirement (the problem will "solve itself" in the 2060's, when most of the boomer generation will have passed away...). So we have had 40 years to prepare, but both voters and politicians have chosen to ignore the issue or kick the can down the road a bit longer. Even the 2008 financial crisis should have been a very clear warning, but what effective steps were taken to deal with the underlying crisis of unsustainable debt?

Since most humans have a time horizon measured in months and years rather than decades or generations, the starship will see every generation have a handful of Cassandras trying to warn everyone about the upcoming problem and everyone else ignoring them.

This also makes the second assumption that a human society can function intact for such a long period of time. The Roman Republic lasted for about 400 years and the Empire another 400, but the Republic was radically different at the end than from the beginning, and the Empire changed almost beyond recognition during its time as well (and the Eastern Roman Empire was also dramatically different from both the Western Roman Empire, and institutionally and culturally very changed when it finally was overthrown in the 1400's). It is quite possible that the internal society of the starship will change quite radically in the intervening time and the concerns and issues of the landing crew will be far different from that of the launch crew. Indeed the Pirates might not be a threat in 600 years either, since there is no guarantee that they will have the same issues or mission objectives by that time.

Indeed, it might be interesting to look at the problem from the POV of the pirates. What is keeping them focused on boarding and plundering 20 generations in the future?

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    $\begingroup$ +1 for the Pirates POV. Why would they spend 600 years of travel? Maybe they want the super computer :D $\endgroup$ Commented Dec 28, 2015 at 12:00
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    $\begingroup$ Considering that with known technology it would take about 1000 years to get from here to Alpha Centauri, the pirates may simply be a mission that launched a bit later than the starship, but realize they diid not take enough of the correct supplies and equipment. The solution to the problem is heading right to the same star system... $\endgroup$
    – Thucydides
    Commented Dec 28, 2015 at 21:41
  • $\begingroup$ Space is big. Like really big. The idea of trying to intercept a generation ship with another generation ship is absurd, even in the same star system. Play KSP for a few hours and try a planned docking in orbit. $\endgroup$
    – Aron
    Commented Dec 29, 2015 at 4:52
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    $\begingroup$ @Aron Actually now that you mention it, while delta-V would not be a problem for colliding with the target if you have a reasonable Predicted Intercept Point to launch from, there is a funny issue here I didn't think of. The kinetic kill vehicles which demonstrate that this sort of intercept is possible today don't care to match velocities to dock. The delta-V required to guide would be trivial, but the delta-V required to remove any excess intercept velocity without plowing through the target could be brutal. $\endgroup$
    – Cort Ammon
    Commented Dec 29, 2015 at 17:47
  • 1
    $\begingroup$ @CortAmmon My advice. Blow the Vehicular AirLock on the nosecone. That or IronMan it... $\endgroup$
    – Aron
    Commented Dec 29, 2015 at 17:51

In our world that means a lot of computer power

You postulate, that we cannot do anything with attack in 600 years. I am going to question that idea a bit:

To be able to know, that something is going to get us in 600 years in space means a heck of computer power, because everything moves pretty fast in space

But, your ship was able to calculate with exact precission, that the pirates are going to get them. No matter the changed stars, no matter if the ship is going to sacrifice one or two generations in getting from A to B by slightly changing the course.

Space rendezvous is quite difficult maneuver. Especially if one of the ships does not want to rendezvous. In our world you could change trajectory of ship in very small order now and get more than million kilometers of difference in 600 years.

Yes, as I said earlier. If goal of the generation ship is getting from A to B, this change of course would mean having the trip being longer by (say) one or two generations. Still better than to be attacked.


But you said that even if my generation ship is going to do such small change now, the pirates are going to get them anyway. (Because you calculated that on your nearly impossible computer).

You have these choices:

  1. Party wild for 19 generations and let "them" deal with that. This is most believable approach, because on Earth and global warming, loads of people have exactly that approach. And if you do not sort your waste, welcome to that group
  2. Use your super computer to help you get an solution. If it can calculate trajectory to rendezvous in 600 years, given the speeds and vast emptiness of space, it is perhaps time to use it wisely and provide you weapons, or solutions
  3. Think about how trajectory changes work and decide if the pirates can work out "small change now but huge difference in 20 generations" or "do nothing now and have huge change of trajectory in 19th generation". If they can, then you basically have only option 1 or option 2.

Given human psychology, I can assure you that chosen solution would be number 1

  • $\begingroup$ Terrific answer! Needs a few small edits for syntax and such. I'll do it soon if someone else doesn't. $\endgroup$
    – CAgrippa
    Commented Dec 28, 2015 at 9:46
  • $\begingroup$ I don't buy it. If we're talking realistic space travel then the generation ship was designed with a particular course in mind, which is basically a straight line: accelerate to top speed, optionally wait a while, then turn around and use the remaining fuel to decelerate. Any deviation from this would result in missing or overshooting the target system; the tyranny of the rocket equation would completely prohibit brining extra fuel to turn around and come back. If the pirates are on a rendezvous course there is nothing you or the pirates can do to change that. $\endgroup$
    – N. Virgo
    Commented Dec 29, 2015 at 4:21
  • $\begingroup$ I agree with you, but still you should get idea how hard randezvous actually is. Even if you end orbiting same planet in same solar system, randezvous can be nearly impossible $\endgroup$ Commented Dec 29, 2015 at 11:44
  • $\begingroup$ Isn't global climate change kind of a bad example? Firstly, the conflicting opinions about what's causing it, though lets not get into those opinions here (whereas the inhabitants know for certain that the pirates will be there), and secondly, because we are reducing and may be able to eliminate the burning of fossil fuels by 20 generations (which, so long as it hasn't caused a chain reaction by then, would stop the climate change if the greenhouse gases are the reason?) $\endgroup$ Commented Dec 29, 2015 at 19:22

It really depends more on the type of generational starship. If we're talking about a Traditional Generation ship, a massive one-way vessel designed to keep hundreds or thousands of people alive for hundreds of years then colonize, there are very few reasons to engage in piracy. Since a Generation ship is so massive, you'd have to have an equally massive empty ship to take on the spoils... if you have anything smaller, the generation ship would just grow back the loss over time. It would be different if it is a Suspended Generation Ship (Such as in Hugh Howey's Half Way Home), because the colonist's ship is going to be growing the colonists in a vat, matrix-style, only when they get close to the destination. Pirates can board and take what they like due to a skeleton crew (if there is a crew) onboard, with almost no pushback.

Going back to a traditional Gen Ship, the massive time difference would psychologically impact both crews, not just the colonists. Over twenty generations (~500 years), the "incoming pirates" may

  • Divide the colonists on what procedure to take, resulting in a civil war of sorts

  • Spur the colonists to become more militant, ready to defend from the pirates, giving the entire society a militaristic bent. This could generate a society of warriors, think of it as Spartans (in Space!) at best, or at worse, destroy themselves before they even arrive.

  • Change in the eyes of the colonists, almost to diety-like status. The pirates may turn into avenging angels, messiah-esque saviors, the denizens of the underworld, or just be representative of a coming judgment. They also may just fall into myth, so the colonists largely don't believe that they're coming.

What I would think would be the most interesting is if you also show the opposite happening with the pirates themselves, because 500 years would also do a number on them. They may go through similar social evolution. It could be interesting if, for example, the colonists militarize waiting for these pirates, but the original pirates go in a spiritual direction and view the generation ship as a promised land of sorts.

  • $\begingroup$ When you said "divide" I wondered if the colonists could actually split their ship into two or more pieces during the 600 year wait. Then it might be possible for the pirates to capture one or two of the colonist ships, but not all of them. They could also create decoys, and ships could carry and burn different amounts of fuel. (E.g. a small ship with a few people could get boosted ahead of the rest, so they will definitely survive but the rest will be caught.) $\endgroup$ Commented Dec 28, 2015 at 15:14

One purpose of a generational ship, besides colonization, might be 1st contact with other species. Pirates may be a scary thing to consider, but with 20 generations of advanced warning, a plan to "talk to them" might be considered.

People may already consider themselves "slaves" to the ship for the next 20 generations. A pirate takeover could be considered "liberation" to some. Explaining to the pirates your people have used these supplies and technology for 20 generations might make it easier for you to let you live and "run things for them".

At the very least, maybe they will agree to drop you off at the nearest inhabitable planet if you give up without a fight? Spending resources to fire a big weapon, or risk of possibly damaging their prize, might be a fair trade for a little cosmic "bus fair" Thus: Colony successful. Although, maybe with less supplies.


What is the pirate's motivation?

I presume by the word "pirate," they intend to plunder the contents of the ship. On the sea, this involves disabling the enemy and then sliding up to board them.

.. but what's this board thing involve anyway?

One of the fundamental requirements to board and steal stuff is that your relative velocities have to be really small. But that's in direct conflict with the nature of intercepting the generation ship, which requires a large closing velocity.

The only way this could happen is if the pirates were close enough. Interestingly enough, this also implies that the pirates must also either be launched in a generation ship themselves, or have not yet launched, but intend to launch from a point directly on your path. If they are a generation ship, their acceleration is probably not all that hot, so they would have to have been launched really-really close to you. You probably know them. Go hail them, use a personal solution because you probably know the faction that launched the pirate ship. There cannot have been much of a time gap between launch times, or the relative velocities required for intercept would be excessive to bleed off for boarding.

This leaves the last possibility, that they are almost perfectly along your path, and intend to wait for you to race by before launching their pirate ship after you (using a ton of fuel to accelerate rapidly). This is where the 600 years can be a godsend. If you vector around them, they will be forced to move not just the high-acceleration pirate ship to keep it near your intercept course, but move whatever platform it's waiting on.

At some point, scorched earth becomes a valid approach. As you vector off course, and they align with you so that intercept is possible, they burn lots of resources. At some point you can communicate with them, and offer to split the resources you have. Make it clear: if they don't leave you with enough resources to make the trip, you'll just scuttle the entire generation ship (why bother continuing a journey, no matter how important, if you can prove you lack the resources to make that journey worthwhile). They're having to expend resources because you're not making it easy on them. Pirates who are moving entire launch platforms into the path of oncomming generation ships can't afford to be wasteful with their fuel. They need enough to make a profit.


Interesting read and replies, however in my opinion generational starships are already dead before they even exist.

Whizzing through space at high speeds, for several 100 years is NOT the way we will get around the universe. We will be stuck here on earth until we figure out teleportation/wormhole/jump/warp or some other mode of transportation that enables us to ignore the current laws of physics as we know them.


Because near light travel is dangerous, slow, impractical and even more poignant: socially and politically unpredictable. If we ignore the distances, the odds of hitting something, and even the best case travel times (all of which are all terrible) think about how much society has changed on earth in the last six hundred years. We went from religious zealot misogynistic warmongers to moon walking entitled vain sedentary consumerists intent on our own extinction through sheer consumerism.

You could put the brightest, kindest, most peace loving individuals on the ship at the start of the voyage, but by the time they arrived, they could turn into racist war hungry cannibal murderers...there would be no way to control the outcome, so why even bother to begin with?

  • $\begingroup$ It doesn't answer the question that is asked $\endgroup$
    – bowlturner
    Commented Dec 29, 2015 at 3:35
  • $\begingroup$ Wait, we're not religious zealot misogynistic warmongers? $\endgroup$
    – NPSF3000
    Commented Dec 30, 2015 at 11:43

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