I was thinking about the concept of space whales that are presented in some sci-fi universes. Usually, their origin is either unexplained or explained in some pseudo-magical way. As an example, it is good to present void whales from Warhammer universe.
There were some good questions that were asked about them in the past: one, two, but I think they are missing some key points to make these whales at least semi-realistic. There is even almost the same question as mine, but I believe there is something more to say about the idea of the void whales.
For example, there is no way to store enough energy in chemical form to travel between stars, as it will require very big amount of time to perform such a journey. The option to harvest energy from the stars seems promising, but the radiation energy density drops at least as the inverse square of the distance from the star, so there is no way to keep harvesting it on the way between them.
In my opinion, the only type of energy that is valuable to store and harvested in outer space is nuclear energy. At first, it may sound unrealistic even alongside space whales, but let me explain the details.
This is the reality check question, so I am asking, whoever will read all this nonsense below, to comment on how to improve my space whales and how to make them some more realistic. If realistic is the right word for a space whale. Constructive criticism is also very welcome.
The questions that really need an answer:
What form does the void whale have? (Spherical might not be the best answer)
How did the space whale evolve itself into existence?
Below is the description of some key aspects of the space whales as I see them.
They are harvesting uranium from space dust and fueling their organic nuclear reactor.
There are two elements(encountered in nature) that are known to humans that may be useful as an energy source: Uranium and Thorium. There are two problems with the nuclear reaction inside a living creature: radiation and temperature. But the radiation may be harvested as thermal energy and the temperature is just a direct energy source that can allow the creature to convert nuclear energy to chemical energy to power its muscles(or whatever it has instead of them), brain(if it has one) and to stay alive in general. There are some creatures that have such mechanisms, so void whale might use some of them. The most convenient part about a nuclear reactor is that it does not have extreme temperatures inside of it, comparing with a thermonuclear reactor, for example.
Another problem is that this whale must have the ability to enrich its nuclear fuel. Luckily, the centrifuge, which is not a very realistic semi-organic device by a long shot, is not the only way to do the enrichment. Diffusion is a slower, but more feasible way, to do it inside the void whale.
The question that is not yet answered is how this whale will obtain enough uranium and thorium in outer space. The answer is that all elements are belived to be formed during the stars' life cycle, so there are some places in space where these elements are presented and whales can harvest them, such as supernovas or protoplanetary discs fro example.
Jet force and relativistic time slowing are the keys to a successful space journey.
In my opinion, there are not many things to choose from. Jet force is the only known way to travel fast in space. There are a lot of things which space whale might want to get rid of. Radioactive waste is not a very smart thing to throw away as it might be used as a radiation source to harvest energy from it. Also if the whale's chemistry is complicated enough it might have a closed fuel cycle inside of it.
There is no friction in space, so the whale might want to throw away all stuff it found during his feeding process, which is useless for it. As it needs to process a big amount of matter to get fuel there will be no lack of jank to throw away. It may be enough to make it possible for it to reach high velocities that are required to surpass the gravitation of planets and stars.
One interesting thing about high velocities that the body that has them (even if they are close to light speed) does not care about them. The acceleration is the thing that matters, so in theory nothing fundamentally forbids the whale to move on near light speed as long as nothing will collide with it.
It opened very interesting opportunities for them. For example, if the whale can hibernate itself indefinitely long, then after it arrives so much time may pass then all radioactive material it stores had decayed a long time ago, so their half-life time would be the upper boundary of whale's travel time. But if the speed is big enough (relatively to destination object speed) the whale's time slows and this effect allows the whale to travel even between galaxies.
The mouth is crucial because void whales use jet force thus having a preferred direction of incoming dust.
The obvious decision is to make a whale's surface to be able to absorb dust particles, so the harvesting process will take advantage of the whale's own gravity. But as the whale is able to move using jet force it is convenient to give it something mouth-like.
The most valuable places for the void whale to pasture is protoplanet discs around stars. They are rich in elements and denser than the remainings of the exploded stars, where all those elements were born. So the mouth should play the role of a funnel. As the possibility of hibernation already mentioned, a whale might as well have the ability to close and open its mouth.
Another possibility is to let the whale the ability to harvest on asteroid fields. Then its mouth should play the role of blender for rocks.
This breaks the spherical symmetry of the whale, so it might have a complex form. One may say that the spheric form is the best form to minimize power leaks from the thermal radiation, but I think if an organism uses nuclear power as a food source it is ok for it to lose that amount of energy. The hibernation state might be a little different as the whale will be in such a state for really long time.
Spectral decomposition to search for needed elements. Gravitational field detection to use the gravitational maneuver.
The void whale should have some way to locate the food sources. It must have a complex brain to analyze light from the stars and perform spectral decomposition to figure out where it should go after this protoplanetary disk is finished.
The most convenient way to see light from all directions is to use your own surface as a giant eye. The problem with this solution is that light must be focused to analyze weak sources of light that are far away, so maybe there will be places on the whale's surface that will act as lenses and mirrors, to magnify light from distant stars.
Also, the void whale might use some knowledge about gravitational fields around it, so it may use the gravitational maneuver to accelerate itself with little to no loss of jank mass.
Not sexual reproduction as the population is very sparse. Spouse and parthenogenesis are good alternatives.
The void whale population is very sparse, so it might take a very long time for pair of whales to meet for them to have sexual reproduction. One way to make this problem a little bit less harsh is for them to breed in the same way as fish do. The female whale is making a capsule with all ingredients that are needed for a new whale to develop and then the capsule is waiting until the male whale will find it. The problem is that it is no way to locate such a tiny object for an organism designed for finding protoplanetary disks.
The sporogenesis looks very promising as the spore might contain fuel and other elements to sustain itself while traveling among stars and develop into a new void whale if it finds itself in an element-rich place. Another plus is that they are starting in a hibernation state so they will have a chance to live long enough to encounter a nice place even if it is very far away.
Also, the parthenogenesis is a good way to reproduce as it developing from species that use sexual reproduction, which is better from the evolutionary point of view.
So the most realistic way for the void whale to reproduce is to harvest a lot of useful materials, form spores, and then eject them with great speed for them to travel as far as possible. This way to reproduce also might form a defending mechanism to dive another whale away from the food/fuel source. Then these spores wait for the good times and during this waiting, they may be fertilized.
This is the most tricky part of the void whale design. How this enormous, complex creature evolve itself into existence?
In my opinion, is that the most complex part is the biological nuclear reactor inside of them. It is known only about one natural nuclear reactor on Earth. But maybe if our uranium was reacher and there was more of it, such nuclear reactors might be very common.
The chemistry inside such the void whale might be very complex and maybe it uses some other organisms to sustain itself. As was mentioned above there is a fungus that transforms radiation(some of it) into chemical energy, so the void whale may use it the same way humans use bacteria in intestines.
The water might be used as a moderator to start the nuclear reaction if the fuel is rich enough. So on the planet where uranium is common, rich with the right isotope, and life is used to radiation there might be species that just eating uranium and then the flora inside of them are converting heat and radiation to whatever is needed for this creature to move, jump and search for more. As uranium is heavy then the creature should be big and strong and might live in the water.
Then it needs to take one more step and go to space. It is not possible without some planet-wide cataclysm. It should not be too bad for life to stay alive, but impactful enough to open a way for organisms to slowly adapt to vacuum.
And in the end, there is another step where these whales will finally go to space and spread among countless stars and consume the neverending number of unborn planets.
P.S. Thanks for reading all this mess. English is not my first language, so let me apologize in advance for any mistake I have made in my question.