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A spacecraft designed for interstellar travel is discovered 100 million years later. What pieces of it still work, what parts would be easily repairable, and what would still be even vaguely recognizably intact? Alternatively, if nothing would work, what percentage of the ship would even be left (after sublimation to the vacuum, bombardment of micrometeorites, etc.)?

Key pieces I'm wondering about:

  • The hull (how intact would it be?)
  • Macro-electronic components such as sensors, lasers, or other instruments
  • Micro-electronic components, such as CPUs, RAM
  • Digital data storage (reasonably shielded optical storage)
  • Physical data storage (printed signage, physical books, engraved plaques)
  • Thrusters (antimatter or ion thrusters)

Assumptions

  • This spaceship is designed with a technology level several hundred years in advance of what we have now (advanced enough to be able to do interstellar travel). In order to avoid the answer being "it depends on what your technology looks like", I'll make the known incorrect assumption that technology of the future looks like the present but with more energy efficiency, energy density, and precision manufacturing. So fusion power works, electronics have the same principles but are smaller, any material that we can make now at enormous expense (including moderate quantities of anti-matter) can be made fairly cheaply, etc.
  • The spaceship is adrift in interstellar space. It doesn't crash into anything large, but will go through a nebula at some point. A recent projection of the courses of the voyager spacecraft indicate they are won't crash into things for at least 5 billion years, and that the golden records will still be somewhat playable after that time, so I expect the ship to still be intact, but there will be a lot of contact with lose particles and whatever energies and radiation the ship is exposed to.
  • The spaceship was designed for interstellar travel and a 100-year service life but did not have any particular types of longevity engineering.
  • All electronics have reasonable degrees of magnetic shielding and durability to meet the intended 100-year interstellar service life of the ship. Their digital storage would be a material that combines the durability of optical storage with the read/write speed of solid state storage.
  • The people discovering this spaceship are willing to put a lot of effort into getting it working again.
  • The ship ran out of power slowly and in a non-hazardous manner (ex. no antimatter containment breach).
  • The spaceship is vaguely cylindrical, 1km long and 100m in diameter.
  • The spaceship doesn't have crew for most (if not almost all) of the intervening time interval.
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    $\begingroup$ Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Worldbuilding Meta, or in Worldbuilding Chat. Comments continuing discussion may be removed. $\endgroup$
    – L.Dutch
    Jun 23, 2023 at 6:58

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I think almost all of the spaceship will survive.

If it is travelling for a hundred million years at 1% of light speed it can get half the way to the Andromeda galaxy. Most of its flight will be spent far from any risk of micrometeorites. It will only meet the occasional hydrogen atom per cubic centimetre. Intergalactic space has to be pretty empty for us to see all the way back to the early universe.

The materials may degrade. However, we look at rocks that are 4 billion years old and try and deduce things from tiny features within them. Materials do degrade slowly at room temperature, but once the spaceship is in deep space, it will cool to the background temperature of 2.7 Kelvin. Almost nothing happens to materials at that temperature.

If it is not dead, the spacecraft may want to know where it is going. It might use could have a computer based on Josephson junction logic. This could operate happily at 2.7 Kelvin. The memory would be based on flux quanta, so would not degrade like normal magnetic memory either. It could use solar power using a telescope. This would be enough for the tiny amounts of power it might need to keep a clock running while it waited to get somewhere.

There might be a tiny amount of wear on exposed surfaces. If it had a camera, it would probably stow it so the optics kept their exact surface. The ship might lose a tiny amount of matter from the atoms it meets: the atoms are probably going quite fast relative to it, and this might sputter away a small amount of material in the large times.

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    $\begingroup$ I was just thinking to myself when reading the previous answers, "then how come we still have meteoroids in space if materials would be destroyed over millions of years?" I agree that activated circuits would corrode, but if the ship lost atmosphere to remove the gas that would initiate that corrosion process then you'll likely have a semblance of a ship after 100 million years with potential for a significant amount of hull damage from space debris. $\endgroup$
    – mkinson
    Jun 22, 2023 at 13:33
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    $\begingroup$ Something might survive, but will it be usable? Spaceships are incredibly delicate as they have to preserve a fragile species while keeping the weight to a minimum. Just one system failure caused a real problem with Apollo 13. $\endgroup$
    – David R
    Jun 22, 2023 at 14:00
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    $\begingroup$ Apollo took 3 days to get to the moon. This is travelling for 3*10^10 days. Most of that time it will be almost shut down, and close to absolute zero, and in intergalactic space. IMHO if it was going to take on the journey, it would have been built to survive, and the best way of not wearing out is by doing almost nothing. $\endgroup$ Jun 22, 2023 at 18:58
  • $\begingroup$ Re optics, glass is an amorphous liquid, if a crystallization center appears within it, the glass would deteriorate over several hundred years. So optics would fail. $\endgroup$
    – Vesper
    Jun 23, 2023 at 9:13
  • $\begingroup$ Yes. But devitrification, like any reaction, has an activation energy. The reaction rate goes exponentially with absolute temperature. At the background temperature, nothing will happen to glass over these timescales that would not happen in a day at room temperature. $\endgroup$ Jun 23, 2023 at 11:44
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Time is relative.

You may simply assume that the spaceship flew close to the speed of light (relative to the planets your people are living on) through a rather empty part of the universe (so it won't collide with anything) when suddenly everyone aboard died (or for some reason left the ship).

Afterwards, with no control inputs, the ship may simply have continued to fly in the same direction for some decades (shipboard time) and then, after some time, for some reason, an autopilot may have intervened, sending the ship back from whence it came, again at nearly the speed of light, making it fly back for some decades (proper time on the planets).

When the ship was back about where it started its journey, the autopilot may have decelerated it to slow speeds with respect to the planets your people are on, so your people can capture it.

Because the situation isn't symmetrical - the ship accelerates and decelerates, the planets don't - the amounts of time that passed on the ship and the planets (proper time) can differ, and just like in the twin paradox, the proper time having passed on the ship actually is far less than the proper time having passed on your planets, so while hundreds of millions of years passed on the planets, only decades passed on the ship, leaving it fully functional.

However, you'll have to explain how the ship manages to accelerate to such high speeds (which costs humongous amounts of energy), to which I would answer antimatter as fuel (which can be converted to light, which can theoretically as "exhaust" at the speed of light bring a ship as close to the speed of light as needed).

Some estimates for the actual numbers:

(Working in the frame of the planets, and using $m$ for the frame invariant mass)

Computing the speed (relative to the planets) neccessary:

$\frac{\Delta t}{\sqrt{1-\frac{v^2}{c^2}}}=10^7\Delta t$

(So we expect time to be $10^7$ times slower on the spaceship relative to time on the planets.)

Thus equivalently:

$\gamma:=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}=10^{7}$

($\gamma$ is a quantity known as the relativistic factor, see for example here)

We have for the total energy (relative to the reference frame of the planets, by the formulas here and here):

$E=\sqrt{(pc)^2+(mc^2)^2}=\sqrt{(\gamma m v c)^2+(mc^2)^2}\approx\sqrt{(10^7 m c^2)^2+(mc^2)^2}\approx 10^7mc^2=10^7E_0$

Thus, even when working with antimatter, the spaceship would have to "convert" at least $10^7$ times its (empty) rest mass of matter and antimatter 100% efficiently to momentum in order to reach that required speed once, and at least $10^{14}$ times as much in order to reach it twice, because the fuel for the second acceleration has to be accelerated too. Decelerations might be a problem, too, although one might be able to use huge sail-like structures capturing blueshifted background radiation or hydrogen atoms or something similar to decelerate at such high speeds (working out how that would function is left as an exercise to the reader).

This means by far most of the spaceships mass has to be fuel.

Thus does not necessarily tell you that much about the volume, because some "types" of matter (e.g. neutronium) have much larger densities than others.

Actually $1cm^3$ neutronium already weighs about as much as $10^{14}cm^3$ of water.

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100 million years? I think the spacecraft would be non-existent.

Why?

So, the primary drivers of corrosion are oxygen and water - and okay these don't exist in space...

But let's consider the 2 scenarios for your craft:

  1. It's drifting through space or
  2. It's in a stable orbit around something

In both of those scenarios, the 3 biggest factors that would (over such a long time frame) cause issues will be:

  • Unfiltered radiation. Without an atmosphere, all those ionizing particles given off by stars and other cosmic phenomena would slowly eat away at the hull. Think of how plastics break down when exposed to sunlight, only 10x worse (no atmosphere) and over that 100 million year timeframe.

  • micrometeorites. Think specks of dust travelling very fast - they hit the hull, they might only knock off a few atoms - but run that process multiple times a day, for 100 million years - that's 36.5 billion days. Over that much time they will weaken the hull to the point it fails

  • Metal fatigue from extreme temperature gradients. If we are in orbit around a planet or a star or we are just drifting casually, when we encounter something hot, the metal will expand, then it will cool down, it will contract - this is a major cause of metal fatigue in the real world and 100 million years is a long time for that to happen again and again and again and eventually fail.

That said...

If we drop our timeframes down a bit to something more reasonable (maybe 10-100 thousand years) and we place the spacecraft somewhere where it's relatively stable, shielded from radiation, not subject to any massive temperature changes (so not near a star) and has probably in orbit around a very large heavenly body that would shield it from most of the dust/meteorites etc. - then so long as the hull remains mostly intact (it doesn't even need to remain pressurized) - then I think you've got a good chance at having most major systems repairable - but once the hull goes, you're not going to have much luck.

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    $\begingroup$ Integrated circuits won't last 100,000 years, not even 10,000 years. Maybe one hundred years. The individual components in an integrated circuit are tiny; ordinary thermal drift will kill them. $\endgroup$
    – AlexP
    Jun 21, 2023 at 21:19
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    $\begingroup$ I second @AlexP. I designed integrated circuits for a living. We would design them with a mean time between failure (MTBF) rating of up to 15 years depending on the application, but we knew (and know) perfectly well that no technology is expected to last that long in a practical sense. It's obsolete in less than half that time. Chips wear out, just like everything else. The passage of electrons through a doped substrate will eventually compromise the substrate. But what's really hard is the OP is asking us to start from an unknown future. Could that work? Sure, if the OP wants it to. $\endgroup$
    – JBH
    Jun 21, 2023 at 22:03
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    $\begingroup$ @JBH - My thoughts were - without power and with a stable thermal condition, the circuits would be preserved - but yeah, if they are actively being used then no chance. $\endgroup$ Jun 21, 2023 at 22:19
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    $\begingroup$ @TheDemonLord I can see your point. But we're surprised the Voyagers have continued to work and they were specifically designed to survive. Hence my comments to the OP. He/she is already dealing with Clarkean Magic just to put the ship into space with a vague hope of the shell surviving 100M years (half of one rotation of the galaxy... land o' goshen). Science today can't envision anything surviving, so what's left is the OP picking what they need and moving on with their story. $\endgroup$
    – JBH
    Jun 21, 2023 at 22:56
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    $\begingroup$ There are massive space areas that are almost completely dark, without almost any form of energy or radiation and even less probability of find any hint of matter. Maybe a few atoms of hydrogen every... day? month? year? As this areas are massive and account for the majority part of the universe, it's not weird at all that it's where this spaceship has been resting all this time. In this situation (plus some occasional travels through gas nebulas) I think all structural metallic parts would be completely intact. If encounters with mass and/or temperature changes are somewhat often then not... $\endgroup$
    – Héctor
    Jun 22, 2023 at 7:31
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Earth is a spaceship, isn't it?

As far as we know, it works pretty well and it is already well past 100 million years of age.

In short, if intended, the spaceship can be made to survive this long. It is a matter of resources and an ability of dynamic self-repair (any big project implies the latter anyway).

On the other hand, if the particular piece of work is NOT intended to last this long (e.g. like modern cars or airplanes whose intended lifespan is in sync with the technology advance that makes them obsolete), there will be no much parts in working order.

In regard to nebulae:

The spacecraft will probably slow down in the nebula, probably to the point of becoming at rest in respect to the surrounding matter.

Depending on the initial conditions, it may:

  • completely disintegrate (high initial speed). A strong enough shock wave may even trigger a star formation.
  • survive relatively intact, in which case it will start to aggregate the surrounding nebula particles. Depending on conditions, it may become an asteroid, a rogue planet or a star.
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    $\begingroup$ I think self repair violates the "no longevity engineering" requirement. $\endgroup$
    – codeMonkey
    Jun 23, 2023 at 19:21
  • $\begingroup$ Earth is also hanging around a hostile environment and has a huge gravity well to attract debris. $\endgroup$
    – Yakk
    Jun 25, 2023 at 21:39
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No parts will survive 100 million years

Others have mentioned micrometeors, radiation and thermal drift. But on such a long time-scales there is another issue: radioactive decay. It is practically impossible to produce any element with only one isotope, so all those radioactive isotopes will decay in 100 million years. And even some (small) parts of non-radioactive elements will decay. Half life of those isotopes is suppose to be of the order of 10^25, which is a lot. But 100 million years is a long time, and a spaceship is massive. So some atoms will decay, probably into something radioactive, which will decay further. That will wreak havoc on any complex mechanism, and possibly compromise hull itself (which would make previously external hazards worse).

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    $\begingroup$ Radioactive isotopes are not typically major components in engineering. If the materials are not radioactive to start with, they're not going to become more radioactive over time. If the half-life of stable isotopes is 10^25 years, then after 10^8 years, you'd only expect one part in 10^17 to have changed. You have 3*10^13 cells in your body, so the comparable amount of damage would be something like minor damage to one of your cells. You wouldn't even notice. And unless OP's interstellar ship has a nuclear power source, it won't either. $\endgroup$ Jun 22, 2023 at 14:43
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    $\begingroup$ @SarahMesser And one mole of matter has 6*10^23 particles.... So the mass of changed, decayed matter would be significant. The result of that decay is most likely radioactive. Also, your first statement is simply not true. Radioactive isotopes are components EVERYWHERE. Because you cannot separate them from stable ones. And when a small part of your microprocessor change it's chemical and physical properties it will most likely not work anymore. $\endgroup$
    – Negdo
    Jun 22, 2023 at 14:52
  • $\begingroup$ @SarahMesser you missed the point: all things (eg. a lump of steel, or a wire) in a practical sense are(slightly) radioactive. Since the ship was designed for 100 years (+ safety margin i hope), this lowkey radiation was - as you said it already - not a concern in the engineering department, aka costly isotope-purification or similar was not attempted. $\endgroup$
    – Hobbamok
    Jun 22, 2023 at 20:17
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    $\begingroup$ I'll grant that delicate electronics would decay, but a few atoms here and there aren't going to matter much to the overall structure. Most of the atoms will be non-radioactive. As an example, and since you mentioned steel, about 94% of naturally-occuring iron is in stable isotopes: en.wikipedia.org/wiki/Isotopes_of_iron Another 5.8% is "observationally stable" according to that same page. The remaining iron isotopes mostly decay into Mn, Co, and Cr - all of which are commonly included in steel. So over millions of years, the steel might change slightly, but will still be steel. $\endgroup$ Jun 23, 2023 at 18:13
  • $\begingroup$ This plus cosmic radiation. High energy particles will cause work hardening / embrittlement of everything on board, as well as prompt more atomic reactions that wouldn't occur naturally on Earth. This will result in the chemical composition of everything changing slowly over time, leading to everything failing in one way or another. It'll still look like a spaceship, but the hull will explode if you pressurize it, the pipes won't hold water when you fill them, the wires will short when you power them, etc.... $\endgroup$
    – codeMonkey
    Jun 23, 2023 at 19:19
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Frame Challenge 1: You don't really need 100,000,000 years

For the sake of your story, is there any particular reason that drives the number of 100 million? What you probably mean is "long enough for the civilization that built it to be dead and gone," or some other qualitative measure. Human civilization could easily have been wiped out with the nuclear weapons in the Cold War era. We could be wiped out tomorrow, and Voyager would be less than 40 years old. Imho, letting the POV cast (and reader) know that "the ship is ancient, and this is what works" is sufficient. Use a qualitative measure of time, not a quantitative one.

Frame Challenge 2: The parts (probably) don't actually need to work

Unless you need to get your people off a doomed planet in a matter of months (my apologies if this is the case), it's not necessary that any part of the ship is truly functional. Even if not fully replicable, the bits of technology in good enough shape to reverse engineer would provide hundreds of years of technological advance in a few short years. There might be a couple of key hints today that are barely holding back quantum computing, or efficient anti-matter generation. The important thing is what can be learned. To that end, resilient diamond data storage containing technical and scientific encyclopedias could be the most useful thing your characters find, if all else is unsalvageable.

A parting encouragement: Don't let the impulse to have all technical details correct get in the way of writing the story you want to tell. Let some things go and enjoy the ride :)

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  • $\begingroup$ And any spacecraft is going to have a highly resilient distributed data backup system in an interstellar craft, unless they have magic force fields. Because data decays. So you'd make your copy of "the sum of all knowledge" be on multiple diamonds distributed throughout the ship, with high error encoding and cross-reading and replacing the fast, volatile storage that the main computer uses. Because it isn't expensive. Sort of like how Apple computers have ECC ram -- you don't really need it, but if you are going to throw an extra 200$ at a computer why not. $\endgroup$
    – Yakk
    Jun 25, 2023 at 22:56
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Two options: build the spacecraft from unobtainium, which will last as long as your story requires; or make the spacecraft a living thing, which builds copies of itself as often as needed. Of course you'll get mutations, which could fit into your story.

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Given your constrains of:

  • ship was designed to last 100 years with crew;
  • ship was not designed to replicate sensitive parts of itself;
  • tech level is several hundred years forward, with fusion available but no onboard antimatter production;
  • a non-destructive disaster that the ship's crew could not handle;

and assuming that the crew did not go into "salvage a part of the ship to escape imminent death", while probably suffering of other issues...

Only the hull woulld remain in working condition

As said in other answers, any nanomaterial would suffer thermal drift and destructurize, also random exposition to black hole jets, quasars, supernovae and even the normal starlight would degrade both outside and inside structure and fill. Thus, all plastics would decay, all foam would collapse, all resin and other sealing material would also lose quality, all gasses would get released, the fusion reactor would get depressurised if still working and perform a thermal explosion causing loss of power, any capacitors or batteries would meld into unusable and possibly indiscernible pieces of metal agglomerate, etc etc. Yet, hardened steel, monolithic structures made of titanium or probably some other solid materials would not deform beyond recognition. Yes, any micrometeorites would cause dents, cracks or breaches in the hull, a contact with a nebula would either cause the ship to slightly melt on the outside, or if it had breaches, also on the inside, possibly destroying traces of interior elements, still I think a single gas cloud collision would not be enough to cause major hull deterioration.

Exterior elements, such as engines, might retain overall structure yet also might get bent or pierced by space matter, although not into becoming completely indiscernible. The interior mechanisms such as pumps and intra-nozzle fuel channels might undergo chemical damage and also get melded with thermal drift AKA diffusion. Inside, any doors and hatches would also get sealed, but would remain discernible ("hey look, this should be a door" type), and whoever would explore the ship would still find most of the structure elements not deformed.

About plaques made of gold - not enough data, whether any dented markings would lose discernibility over that long but in a relatively sealed environment and zero gravity/microgravity. I think that if there would be a plaque made of bent/stamped steel of more than 1 mm thickness, like a car number, its contents would survive but it would lose all the paint that could be applied to its surface. So, the future explorers have a chance to find a decent amount of everyday words inscribed on its walls, including any markings that the desperate crew could etch. They might also find the reactor's ID together with some specs on such a plaque, like say on this one, such plaques were designed to withstand quite a lot of time.

And that is pretty much all that would have left on the ship that spent 100 million years in the interstellar space. In intergalactic space the damage expected would be a tad less, yet anything that's not dependent on impacts would still be applied.

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My ship would be nearly 100% intact after 100 million years. Here's how:

  1. Redundancies like a 3 level hull.
  2. Drones/internal sensors scan the hull every day
  3. People/AI for repair

Part 1

Team or system capable of harvesting raw materials from outer space. This includes radar for locating the needed resources. Smaller robots like a shuttle craft to mine and return the resources to the ship.

In 100 years metal 3d printers will be common if not everywhere.

Banks of metal 3d printers will be churning out spare parts.

Parts will be rated for criticality to determine there replacement cycle. Every part of the ship would be proactively replaced say every 5 years.

The crew/AI will be constantly doing research analyzing the parts for damage. It will try making new materials, and gradually it will come up with ways of improving everything.

A hole forms in the outer hull, no problem it is the 3rd outer hull send someone/robot to the 2nd hull pull down the old piece, and put up a new piece. The old piece is melted down and recycled.

Air locks to keep the whole ship from depressurizing. Portable air tanks for any crew long enough to make it to the nearest safe compartment.

You would need to be able to manufacture your own computer chips, and you would have repair bots to keep everything maintained.

Outer space has abundances of raw materials if your in the right place.

Even in the worst case, the 3d printers could print a brand new ship 1 component at a time. The 3d printers would of course print there own spare parts.

The AI could even redesign the ship to accommodate future needs.

The ship would probably look totally different after a few 1000 years of R&D.

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  • $\begingroup$ Ship of Theseus, anyone? $\endgroup$ Jun 25, 2023 at 1:31
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Unless we're presuming Clarkian tech-as-magic, you can presume that you're going to lose anything with molecular resolution below about a millimeter. All speculation is based on modern materials, but the concepts are applicable to any materials that aren't specifically designed to survive cryogenic conditions. 300 years is WAY too long a time in the future to reasonably speculate.

You can't reasonably keep something like that warm. Even presuming fusion or fission, you couldn't reasonably carry enough fuel to counter 10^8 years of bleeding heat off, so everything's going to drop to about 3 Kelvin. The differential expansion/contraction of materials will delaminate damn near everything.

Circuit boards, for instance, are multiple layers thick, and silicon would crack in a billion places. The crystalline configuration of most materials would shift, breaking connections. Things like human-scale wires and conduits would be fine, but the insulation around them would likely shatter. Anything that remained powered as it cooled off would be susceptible to changes in resistance and other properties, resulting in whatever passes for a "short circuit" in the year 2300.

If that isn't enough, you'd have to deal with cosmic radiation. These are super-high-energy particles that are constantly shooting through space. If you think you can keep things safe by encasing them in a few meters of iron, think again. Cosmic rays make it deep into mines.

They aren't frequent enough to upset most macro-scale processes because we have massive redundancy keeping everything ok by the laws of averages. They're known to flip bits on computers on a regular basis, and we have to build error checking into our computation processes to compensate.

In a frozen environment, they'll cause individual atoms to migrate, basically diffusing materials through each other. This means that complex systems that aren't destroyed by freezing would eventually be wiped out by radiation.

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A million years is absolutely doable. Throw in some AI and lots of self repairing/replicating parts and the thing could have been active right up to within a few thousand or hundred years of being found by your salvagers. It's total mass might have dropped a bit, but that shouldn't be a problem.

I am pretty sure we're already mounting ION plasma shields on some tanks, so a few hundred years from now, I'd expect those to be more sophisticated. We're also making meta materials that bend light today, so active EMR shielding is on the horizon, if not already deployed. Stopping relativistic nuclei is probably hard for low mass ships, but if you're building something that has to last a very long time, you need a lot of spare mass, and most of that can be incorporated into the hull of the ship.

That pretty much just leaves explaining how the energy supply lasted as long as it did It's possible to send a large fleet of fuel tankers to accompany the ship, as well as ahead of it. Based on similar technologies, but without the need for life support of any kind, they could refuel the main ship along the way, then disassembled and incorporated into the hull of the main ship. It's also possible they all receive beamed energy for tens or hundreds of thousands of years as well.

It might have been partially stripped down as its occupants entered smaller vehicles to ascend into one or more solar systems along the way, but having expended most of their fuel and getting to their destination(s) and the fact their home world stopped beaming energy at them, they might not have been able to slow their main ship, so it was left drifting in space. Maybe the occupants had become so attached to their beloved AI, they just couldn't bear to shut it down, and they left it operational, so it might have survived on its own for a very long time after it was abandoned.

They might even have continued using it as a remote probe. Perhaps they spotted your civilization and knowing the ship would soon exhaust the power supply keeping the AI alive, they suggested it should exhaust the last of its propellants, trying to slow enough that your race of scavengers would have a chance to find and revive it?

I am pretty sure we already have the capability to make things that last a million year, but we just don't bother expending the resources to do it. Under the right circumstances, perhaps 500 million years from now when the Sun is threatening to fry us all, we'll build such ships?

You really don't need to have a million year old ship at the end of a million year journey either. If the ship and it's supporting supplies are launched by a solar system scale gun, then you could easily have enough supplies nearby to build new ships every few hundred years. That also solves your long range energy supply problems. You could launch a million times more mass than the main ship, so lots of fuel for whatever kind of reactors you get your power from.

Technology doesn't stop advancing the minute the ship is launched. If it's a large collection of habitats travelling in close enough proximity, with enough brains and AI's, they continue to evolve their technology. After a few hundred thousand years, it would progress quite a lot, or they would likely all die. There's no way they could think of everything from the start, so adversity will bread adaptation. Perhaps this ship was abandoned because they simply didn't need it's antique technology and found better ways to make new materials?

So I'd ask, what parts of the ship you need to work in order to fit your story line? It's easy to explain how those could be still be repairable.

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