Saturday, September 8, 2012

Generation Ships

Warning: this post gets strange and creepy. Read your own risk

One of the great staples of science-fiction is human settlement of space. The protagonists are shown plying the cosmos in gleaming ships capable of conveniently violating the speed of light to have adventures on fantastic worlds far from our own. The unobtanium powered handwavium drives permit the ships to cross the incomprehensibly great vastness of space in a matter of plot moving months, days, or hours. This allows us to have homes on many worlds, and importantly, to travel between them. This is not possible by any method we are even close to understanding.

Space is big. I mean really, really big. Metaphors break down and the mind boggles with the sheer size of it all. The Voyager 1 space probe is traveling at 62,136kph (38,592mph) and was launched way back in 1977 and is only now at the edge of the solar system. That is only 11 billion miles away. If Voyager was going to pay a visit to the neighbors, then we could say in 35 years it opened the door and walked down the steps. It hasn't crossed the lawn or the sidewalk or the street. We struggle to reach the nearest body to us, the Moon, can you even imagine interstellar travel?

I sure hope so because that is what this post is all about.

In almost every Science Fiction story there is a reason to leave Earth. Maybe our home was destroyed, or we were lured off with riches, adventure, and treasure, or maybe we just out-grew the earth and had to leave for lack of room. Another good reason that they never seem to think of is just to have a back-up for the human species.

Let's say for a moment that we had a reason to leave our star-system. A planet wide evacuation would be difficult because I want this to be a near-future hypothetical situation. That many people would not be possible. So, for our purposes let's say it was a back-up of humanity just in case something happened to Earth - this lets us send a small group to colonize another world.

One of the biggest constraints in not technology, but budget. Apollo just sent four men to the moon, yet it strained the resources of our coffers, personnel, and our ingenuity to the limits. Any interstellar launch will be many, many orders of magnitude greater. All launches measure cost by weight. Take a space shuttle. Its purpose was to put cargo in space - human cargo and equipment or supplies. That total payload is the whole raison d'etre, so all cost of maintenance, procurement and launch costs are just for that cargo. If you take the total cost and divide by the weight of the payload, you get a cost per pound to low-earth-orbit. A single gallon of water cost $80,300 on the shuttle! Newer programs cost far less, but remember, it's not going to low earth orbit, but to another star-system. Again, we are not talking far future, but near future, so things like weight and fuel are all tied into a single problem: cost. We theoretically have the technology to build a star ship now, but there is not enough money on the entire planet to do so. Not money available - I'm saying in existence. A program to launch millions of people may not be possible for eons to come.

Let's pretend that we've found a world. The Kepler space telescope picked up an earth-like planet, and after years of observation with first; the Hubble, then the James Webb followed by even bigger and better systems, our scientists decided it would support a colony. It will be a new home for humanity, to hedge our bets and preserve us from extinction. Excitement builds on Earth. Humanity unites to build something truly colossal: our first star ship.

It has a tremendous amount of fuel to allow it to move at fantastic speed. Due to the immense distances involved, it will take hundreds of years for our ship to travel to its destination, a very short time when discussing interstellar travel. Decades, perhaps centuries will be spent accelerating, then that many more to slow it down as it nears the new world. This means that most of the ship will consist of its exotic fuel. Next is life support. This ship will be a home for the colonists for longer than most American cities have existed. There must be food, air, heat, power, and comforts for hundreds of years. There must be a shield on the front of the ship. A grain of sand at millions of kilometers an hour would have an impact like a warhead. This shield will be a heavy piece of ablative armor, perhaps with some sort of deflector field to improve our ship's chances. We should make our ship narrow enough to be protected by a small shield, to save on weight. The math says our ship will be kilometers long.

James Cameron's Avatar star ship is shown above. It actually has a good lay-out. Huge fuel tanks and engine in one end, debris shield, storage and habitat at the other. It's just a little small. A great feature is that the habitat spins to provide the illusion of gravity.


Because our ship will take hundreds of years to travel, the crew is an issue. Nobody on board will live to see the end of the journey. Only their descendants will make the trip. This is called a "Generation ship."

Construction of the ship will be largely done in space - it's far too big to launch from the earth in one piece. Much like we built the International Space Station, it will be launched as parts. The star ship will be expensive. Stephen Hawking talked a bit about this. He pointed out that the people who build the ship will spend a great deal of time and treasure on this huge project, only to see a few people board it, the engines power up and then move out of the solar system, never to return. It will have to be a selfless sacrifice, or perhaps an act of desperation.

Aside from the antimatter - or whatever fuel source we have - the ship must carry the colonizing equipment, life support and everything. Space and weight are at a premium here. We must deduce what the minimum we can send is, and then shave that where we can. The goal is to establish life, in a meaningful way, on this world. There need to be educators, doctors, nurses, engineers, architects - in short all the human resources of Earth. We don't just want this colony to survive, we want it to thrive. We don't need all of that immediately, but we need it when they reach the planet. In addition, we need to avoid inbreeding and the Founder Effect.

So the question is, how few people can we send? How broad a genetic base do we need, and how do we prevent gene pool deterioration? I don't really know. It's hard to find any info on this. I think, from what I've been able to find, that if you deliberately select for genetic diversity you can establish a population with as few as 6,000 - if you maintain a high birth-rate. This is a problem. That pushes the habitat size and needs way beyond what is reasonable. That is more than the crew of a Nimitz class super-carrier!  The big aircraft carriers are like a floating city, but are far too cramped. Even with an open deck, the crew needs shore leave and time off rotation. We can fix this by increasing the size of the habitat to three times the size of a Nimitz class carrier, or reducing the crew. Neither will work. Hold on to your hats, there's a solution, but it's kind of disturbing.

Do you remember the frozen sleep pods in 2001, A Space Odyssey? Yeah, those don't really work. It would be nice if they did. Maybe someday we'll figure out how to freeze people and keep them alive.

2001, A Space Odyssey also failed to have much of a back-up crew. Frozen sleep, if it even worked would not be without fatalities. Two guys left awake to run the ship is not a good idea.

Maybe I should say that frozen sleep doesn't work on developed humans. Embryos are a different story. This brings us to this freaky idea I got from the life cycle of some species of aphid.

In early spring the aphids hatch  out of eggs. They are small, but strangely are all female and born pregnant. They grow and give live birth to their young. These are clones of their mothers, also born pregnant. They give live birth to clones. The cycle continues with each generation producing the next by parthenogenesis until fall. In the fall a mutation occurs. Some are born male and some are born as unfertilized females. Sexual reproduction of these strange aphids produces eggs that can survive the winter.

Wow, you're still reading?

The idea is that you launch a ship crewed solely by young women, about 60 of them, and a hold full of frozen embryos. Of the passengers, only a few will be core crew. The others would be grunt labor or some other occupation like hairdresser. All crew would have time to pursue their own interests on the side, even change career if they wished.

In this plan there are two sets of embryos aboard, one for transit, one for re-population. The transit embryos are all female, genetically tested to ensure that they are similar to simplify medical treatment. They could even be clones. During transit each woman will impregnate herself with one by in vitro, and raise her child to replace her. Thus the population is maintained at a manageable size. As they near their destination they will begin to grow the population, each one having multiple children. They'll open up the habitat sections that were kept sealed to save supplies and expand their space to handle the new generation.

File:Transhab-cutaway.jpg
NASA came up with a concept of an inflatable habitat section for the International Space Station called a Transhab, a concept now being used by Bigelow Areospace to build their own station. This may be a good idea, the living area for the new generation. They can be kept deflated to conserve supplies and prevent transport damage in the hundreds of years before use.


After they land on the planet they will continue as they were. Once they hit about 3 thousand they will open the second batch of embryos. This batch contains genetically diverse male and female embryos, the base of our new population. There will be some cultural problems to sort out - after all these women will have never met a man before. There also will be a period of cultural change as they go from lesbian relationships (if any formed at all) to heterosexual. The shock would be great.

Now, I think this whole thing is a bad idea and really, really creepy. What I want to happen is I want to take my wife aboard a faster-than-light ship to a distant world, and go visit our parents on earth every Christmas. This whole thing was a thought experiment with foreseeable technologies. Who knows, when we leave Earth we might just beam straight to a new place instantly. Guessing the future never works as well as we think it will. Just look how much more advanced our cell phones are than Captain Kirk's communicator.

I can't wait to see the surprises that lie in store for us. How will we leave Earth and when? I would love to know.
 P.S. I promise that the next post will be less weird... well at least a little bit less weird.

2 comments:

  1. Good thoughts. Using forseeable technologies might go so far as to have digitized people manning the ship with artificial bodies as locomotion. With the advancement of computers and eve Augmented reality starting to become a thing of science fact i think that in time to come cyberized brains and even infomorphs of humanity are in the next hundred years.
    Though a major problem with your idea would be the going to a planetoid that is hypothesized to be able to support human life. you will never know until you get there. imagine the generation ship, ramping up its population only to arrive at a rock who's environment couldn't support life? do they stop and all die? do they try and all die? or do they re-outfit the ship and try another one, killing the surplus population? makes me think remotely of the short story "Cold Equations" math doesn't care about the individual.
    the only means i can see us leaving our solar system would be through autonomus means. Highly advanced AI, going out, finding the perfect place, building a relay station and having human intelligences sent into synthetic constructs and building a means to grow organic bodies to repopulate. but if we got to the point of being able to transfer ourselves via a digitized brain, then why would we want organic bodies back? For many i have already walked into the realm of scifi, but for how long?
    as for fuel, maybe a fusion engine using H-3? by then the actualization of room temperature superconductors (like possibly metallic hydrogen)would keep energy requirements very low.
    Here is an odd question (another mormon friend of mine says it kills you and thus those after are without a spirit and could not live), how would the matter to energy to matter effect one's religious views, in the case of Star Trek teleportation? i mentioned the other view i have been given. Also ththe new Twilight Zone episode with a form of teleportation where the body is recreated (personality and all) on the other side and once verified it was a success the "original" is then destroyed, only to have a mishap and leave the original alive. the moral conundrum this poses. But that leaves the scope of your post (oh and dinosaurs brought that technology to humans in the episode lol).
    oh, if you haven't figured out who this is it's Nick from Salt Lake. for some reason my handle is my high school handle. trying to correct it.

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    1. I see i mentioned H-3.. i meant He-3... my bad

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