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I am playing with the idea of an alien ship landing on earth 130,000 years ago. Over time it's covered up with water and sediments and is eventually discovered in modern day.
It contains numerous hibernation chambers for aliens hence it would need an energy source to moderate and run the chambers. Scientifically how could a single energy source or battery last all that time?
We can generate pseudo-never-ending power from all sorts of particles impacting all sorts of surfaces. Starting with the most common - visible light photons. Earth-made photo-voltaic panels (aka - solar panels) can last 20+ years, turning photons to power for as long as the panels are in the sun, slowly degrading from UV exposure and hail impacts.
If we crank up the craftsmanship and keep the hail away, photo-voltaic panels should be able to last a long time. Cranking the craftsmanship is just a factor of the story telling - how well made was your alien ship? If the thing is still standing after 130,000 years, I'm guessing they're pretty good, so if the ship had solar panels, and it ever saw sun - they'd probably still work too!
Unfortunately, your ship isn't in direct sunlight, so we have to abandon photons and move to another particle.
You could use betavoltaic panels if you're near radiation. These are a real thing earthlings can make and can used to power low power device for long periods of time by converting beta radiation into power.
Alpha voltaic pannels are also a thing - we can use Alpha particles to generate power.
Gamma voltaic devices are also a thing, we can use gamma particles to generate power.
I think you see where this is going: Humans already have Alpha, Beta, Gamma, and visible light powered generators. You just need to find a particle that can get all the way down to the ship without wasting any energy hitting pesky dirt or water.
Neutrinos are your answer - they travel through basically everything, except the specially made panels on the ship, designed for exactly this purpose, which have been receiving power from the sun for a few hours every day when the planets rotation lines the panels up with the sun and they receive several kW of Neutrinos.
Copying some maths from PcMan:
7e10 solar neutrinos per cm2 per second. Most of these are from p+p fusion, thus 400keV. So 0.004486Joule per second per cm2. That's a small but respectable 44.9 watt per square meter.
You can tweak how much power the ship actually gets by varying the panel sizes, ship location, and ship orientation until the numbers make sense. (Optimal alignment is panels perpendicular to the ecliptic plane) If the ship has, say, 30 square meters of panels, that's a little under 1.5kW of power at peak alignment, but its probably following a sine wave up to its peak. If used to charge some capacitors that last the "night" it's able to put out a constant say 100 watts. That is not enough to power the computer or sensors or anything more than a few faint emergency lights, but definitely enough to keep the already frozen crew in insulated pods frozen for another 24 hours in emergency preservation mode.
It makes sense to include a power source like this. If I'm freezing myself for long distance space travel. I'd want to know that if the reactor scrammed and the backup generator ran out of fuel, there was another backup power source that work almost anywhere and wasn't going to kill me if in shadow.
A black hole with mass of 3.6 million tonnes has a lifetime of 130000 years and will emit $2 \cdot 10^{13}$ W. Slightly increase the mass and you can prolong the lifetime as you please.
Then apply the HandyWavy$^{TM}$ stack to convert the Hawking radiation emitted by the black hole into usable energy.
Don't forget to put into the balance also the maintenance and repair robots and their energy needs.
Geothermal power.
The ship has extended a long and durable metal spike down 20 km into the upper mantle. Heat is conducted up this spike to the ship, where it powers a Stirling engline on the temperature differential between the mantle and the cool waters where the ship is.
The ship came to rest in a place where the mantle was close enough to the surface to access. This was on purpose - the ship scouted for such areas before landing. This ship is purpose built to maintain the hibernation chambers using geothermal power.
You could use RTG, just as humans do for some of our spaceships. Only you need to select radioisotope which would last longer. Humans have used up to Americium-241, which has half-life of 432 years, but they could use radioisotopes with longer half-life, for example thorium-230 which has half-life of about 75 thousand years. But your power requirements should probably be modest to be running from such long-lasting power source (or have a lots of it).
If you need larger power surge capabilities though, you would use RTG to charge up a supercapacitor, which could then provide much bigger power at once - but would need long time to recharge again.
decay_energy / (atomic_number * 1.661e-27 kg) * log(2) / half_life -> kW / Mg
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May 11, 2021 at 13:14
I number, which I think tells you what fraction of decays have that energy.)
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May 11, 2021 at 13:20
((0.763*4.687 + 0.234*4.620) + (0.944*4.784 + 0.0555*4.601)) MeV / (230 * 1.661e-27 kg) * log(2) / (7.538e4 years) -> kW / Mg
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May 11, 2021 at 13:21
I think anti matter fits your use-case well.
Your energy extraction is directly proportional to the amount of mass you input into the system. Many other power systems like Fusion, Fission, or Hawking Radiation all have minimum output thresholds or require a minimum amount of energy to self-sustain.
If you don't want power out of an antimatter battery, you just don't input mass - so it has a minimum energy generation of 0, in principle.
Of course, containment fields etc. will still have some kind of 'vampire draw', but as a percentage of overall output it should be much lower than competing alternatives.
As a fuel source, it's nigh impossible to beat antimatter. If you want mass -> energy conversion of any kind, this would be how to get it done, as the energy contained by your reaction mass is equal to MC^2. It's difficult to quantify the energy demands of your space ship, but a gram of antimatter could power LA for about 2 years, give or take.
To trigger a reaction that generates energy, just touch the anti-hydrogen. Although containment fields are non-trivial to engineer, this is actually pretty simple - it's just a magnetic cage in a vacuum chamber. It could be completely solid-state, in principle. The hard part about generating power from anti matter is just getting antimatter in the first place, but your magic aliens have obviously solved that problem already.
An antimatter power generation system does not require any external force operating on it to produce power - it doesn't need to get hit by photons or neutrinos, experience significant gravitational interactions, etc. This means it can continue to operate anywhere, under any conditions, as long as the reactive mass doesn't run out. As a side benefit, because it's totally self-contained, it can also be nigh undetectable (with adequate shielding). A power source that reacts to external inputs such as a gravity wave generator or even Neutrino voltaic panels would leave a trace of some kind as it stole energy from it's environment, whereas this system would leave only waste heat.
There are, of course, some problems with this solution that may render it unsuitable for your story.
You need an amount of reactant mass equal to, well, E/C^2. So depending on total 'E' expenditures for 130 millenia, that could be quite substantial.
Your power source is a really great battery, but it's just a battery. It can run dry. Eventually.
This is not a drawback unique to antimatter, as it applies to all possible power generation options, but it is something to think about.
Entropy exists.
You can't escape it.
Everything, and I do mean everything, degrades to some extent over time. You can't run a constant current through a wire and expect it to stay pristine - you will need something to replace power conduits, electromagnets, etc. Even assuming exotic materials that mankind has never seen, 130,000 years is simply too long for something to exist without experiencing wear and tear.
Your ship will require some system or robotic staff that is capable, in principle, of replacing and retrofitting any individual component of the ship. Given advanced future tech like molecular printing and/or atomic forges, it's not inconceivable that a perfect (or near enough perfect over the course of this timeframe) repair crew could exist - but you'd need to have one, and it'd need to be active periodically to affect repairs.
A fairly small mass of antimatter, with a suitable (left as an exercise) conversion system, will keep a long time (assuming the magnetic bottle and vacuum hold) and provide energy enough to run minimal systems for that kind of time period.
Which begs the question why anyone would design a ship with that kind of endurance. Even though we build submarines that can go years without refueling, mission duration is typically six months because that's the limit on consumable supplies the boat can carry (frozen foods and ingredients for on-board cooking are the main limits).
One potential out is if the hibernation capsules require very minimal power compared with normal ship operation; for instance, if they have insulation capable of holding, say, liquid nitrogen for centuries without external input, the onboard power systems and refrigeration only need to remove the tiny residual heat leakage. That would allow a ship capable of a few years' voyage to rest this way for tens of thousands of years in an emergency situation.
There's no real free energy BUT maybe the aliens are able to harvest energy from sources that rarely run out:
The generators must be made of extremely durable materials and the energy conversions must be solid state to avoid corrosion and abrasion.
The hibernation chambers must be extremelly hermetic and must be able to reach 0 reactions inside it using very few energy to keep this state.
Technitium-99 atomic battery. It has a half life of 211,000 years. This is ultra simple technology that we can produce today. Your aliens keep an atmoic battery on every one of their ships for backup life support. Things go wrong in space; reactors meltdown, generators fail, and engines explode. It could be thousands of years before a rescue ship reaches you, or a hundred thousand years for your momentum to carry you back into a trade lane. When things do go wrong your aliens hunker down in the hibernation pods and wait it out. The atomic batteries are four times as large as they need to be, so that they could power your life support for up to 633,000 years. More than enough time.
Fusion power.
Nuclear fusion can run off water, so a low draw engine could last a huge amount of time, and if they needed more resources they could collect it slowly from ambient water, extracting the precious deuterium.
They could have nanites which drew from local earth resources to help repair any damage and replace broken parts, along with alien technology that made more use of non metal metal subsitutes so they didn't have reliance on special rare materials.
An ant colony is essentially a single organism: an organism with millions of eyes, limbs, and a voracious appetite.
These alien ships are controlled by some kind of shipboard intelligence -- AI or some horrific organic thing -- and all ship functions are performed by drones it controls. Each ship has a variety of drones to handle the variety of jobs on a ship: a small set of large drones for heavy tasks like waiting on the occupants, doing hard engineering, or loading cargo, and a large swarm of tiny drones to handle tasks like interior cleaning, exterior hull repair, or electronics work.
The ship's power source does not normally have an operational lifetime of 130,000 years. But when such a ship finds itself stranded on a planet, it naturally turns its attention to long-term survival -- its own as much as that of the passengers. It has been sending its army of nanomachines into the environment to scavenge for energy and materials.
Over the millennia, this ship has refueled, repaired, upgraded, and finally replaced its power supply many times. No doubt it has invented some truly novel ideas in its desperation. Perhaps in hard times it has even cannibalized a few of its slumbering passengers (or their cryo-beds) when badly-needed elements were in short supply.
The only way for a porchlight to stay on that long is for someone to be inside tending to it. So, make the porchlight be that someone.
It is possible to use radio isotopes with comparable half-lives ie half life of 100k years, and a large chunk of it, but that would require pre-planning to be stuck that long. So not plausible. Its possible to have large enough conventional batteries, if it was planned for and the draw low enough.
But the point is moot because it seems implausible for people to plan to stuck in a location not of their choosing for 100k+ years, little gain, lots of risk, lots of cost. Unless, perhaps they were deliberately trying to avoid something. That is to say, long term storage is not the answer.
Best bet in my opinion is just an low maintenance power supply with automated maintenance. With pairs and spare of all the components. This sort of system would be useful in almost all situations.
That is have three primary nuclear fusion power plants, pair and spare. A redundant automated maintenance and repair system. A redundant system that can manufacture more repair units that can repair the power supply and the manufacturing system, and any other shipboard systems such as the hibernation system.
There is available water so fuel can be collected and stored. IF the ship were in space comets, gas giants all have hydrogen for fuel. So lots of fuel.
A fusion power system such as this is good for all around active duty as a space ship. It can be used directly as propulsion system. A high utility system is more plausible then situational what if systems.
So with fusion and a really good automated maintenance system, it could sustain power very long time. With a maintenance system that due to some chain of events didn't wake anybody.
