Saturday, November 14, 2015

Interstellar Nomads – Part I – The Concept

One funny thing about asymptotic technology: it opens up so many possibilities for futures. An alien civilization can choose many, many different ways of planning their own future and fulfilling it. It’s a little like a young person on Earth who was lucky enough to gain an advantaged situation and can go on to choose a career. What to choose?

We on Earth have not given much thought to really exploring how aliens might choose to live. We can extrapolate from what we have now, we can imagine things based on some particular technology, or we can come up with various catastrophes and pitfalls that could force an alien civilization into some particular choices. But this may not cover the whole gamut of options that an alien civilization might choose.

One option was mentioned before, interstellar nomads. This was seen as a last-ditch attempt to have the civilization survive. Their home planet was rendered uninhabitable, and there were no places for them to go. In this scenario, the galaxy was full of solo planets – planets which had their own origination of life, and those planets which did not had already been colonized. They were late-comers to the star travel business, and there were no vacant properties available. So they stayed in space ships, and traveled from solar system to solar system, picking up what resources they could and then moving on.

Maybe this concept should be turned on its head. What if an alien civilization had developed interplanetary travel in their own solar system, worked out the bugs in it for some centuries, figured out how to build a really large starship and to power it, and then decided they would just rather live in space instead of on some planet. They decided to let their population on the home world drop to zero, and simply turned off the gestation machines. With some small residual population on star ships, they simply took off. Is technology, even asymptotic technology, capable of supporting this?

Before investigating how it might be possible, an immediate question pokes its head into the door. Why would any alien civilization, not in dire straits on their home world, want to do this? What possible reasoning could they have gone through to make this option their preferred choice?

First of all, isn’t this risky? Putting an entire population of an alien civilization on starships and then sailing off, never to return, and never even to land on a new planet seems to be risking the survival of the civilization. If there were several ships, that would mitigate the species survival question, but not the individual survival question. Wouldn’t a starship be like an airplane on Earth? There is some small non-zero probability that something would happen and there would be a crash. Everybody in the airline industry works diligently to ensure that probability is very small indeed, but it doesn’t go to zero.

Airplanes have four sources of problems. One is the failure of some critical component, another is an external event such as a collision, a third is the exhaustion of fuel, and the last is deliberate destruction or sabotage. The same division would hold for a starship.

A starship has many more critical components, all of which are essential for the survival of the population aboard. All the functions of a small city have to be included and they all have to work for indefinitely long periods. Just like airplanes have to land to be refueled and examined for problems, a starship would have to arrive at a solar system, or possibly a rogue planet, and obtain not just fuel, but also all other resources that it needs.

Recall that recycling is never perfect. It might be expressed as some number just below 100%, and the decrement below that limit depends on the materials involved. Everything on the ship would have to be recycled. There is nothing useful that does not age. Some things age more slowly and some faster, but everything has to be recycled. Recycling takes energy, and the closer the recycling fraction is to 100%, the more energy is needed. It is not a linear relationship at all, just the opposite. Going from zero to 90% might take so much energy, but going to 99%, ten times as much, and going to 99.9%, a hundred times as much, and to 99.99%, a thousand. These numbers are simple fabrications with no purpose other than to illustrate the problem. Higher amounts of recycling demand significantly more energy. There is an obvious tradeoff between the obtaining of new fuel and the obtaining of new resources.

When a starship pulls into a solar system, and finds an asteroid for resource extraction, it is going to have to dump the residual mass of material that could not be separated and recycled. If the level of recycling of a particular item is 99.9% over the course of the typical interstellar hop from one solar system to another, at the arrival time in the new solar system, the ship will have wasted 0.1% of that material, and it must be replaced. It might be they are still carrying it in the form of highly diffuse matter, something containing all of the elements and organics and whatever that the ship runs on. This could be dumped in space as they travel, or it could be dumped at the destination solar system. Then the new 0.1% has to be found, refined and cleaned up in general, and inserted into the recycling system on the ship.

Every single thing on the ship has to go through this recycling process. The hull is included. The electronics and sensors are included. The hotel facilities are included. The power source is included. The fuel tanks are included. The propulsors are included. The recycling equipment, including material transport and chemical treatment and biological vats and whatever else is use are all included. The living organisms on the ship are included, but not in the same way.

Biological organisms are constant recyclers, in that the atoms and organic compounds and structures in the body and its fluids are replaced at varying rates, and some residual excreted, to be replaced with the various inputs the organism needs, gas, liquid and solid. The ship would have to have an ecological component to it, so that all the input needs of the organic creatures could be met and their wastes recycled. This takes energy, and hopefully it can be done with the same energy source the rest of the ship uses.

In a sense, the entire ship can be thought of as a combined organism, mechanical and biological, which takes in pristine resources and energy-rich materials, and excretes diffuse waste matter and heat. The fraction of the ship that is biological is one variable that the designers have to decide upon.

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