NationStates Jolt Archive

A short article-type passage which I wrote exploring such a concept. As far as I know the little science which I refer to is presented correctly; bear in mind, though, that I wrote this several years ago and now have vastly improved knowledge of physics.

Apologies for any formatting errors; I copied this from my blog, not having enough energy to open the original OpenOffice.org document, so it may still have the formatting from there.

An exploration of the concept of ‘Generation ships’ and their feasibility, uses, potential and effect upon mankind

By Daniel Rhodes-Mumby
Perhaps so-called ‘Generation ships’ will someday become reality. I myself have no doubt, if only because they are, in many particulars, quite possible now.
For those who have not heard of the term, a ‘Generation ship’ is the name given to a (typically extremely large) spacecraft of any sort on which there is placed a large population of a specific creature, along with everything that the creature needs to survive for a long period of time. They are envisaged as the most technologically, if not financially, feasible methods of colonising new worlds. If the population is large enough for both a replacement rate of breeding and to offer enough choices of mate that aren’t incestuous then these craft, provided that they have a renewable source of air, water, food and other gewgaws necessary to survival, can potentially last for thousands of years, enough time to travel to some of the nearer solar systems and find a colonisable planet. The original travellers are long since dead, but their descendents can still colonise worlds. Virtually the only thing that can halt such a project once it is started is the craft or one of the vital components within being damaged severely enough to endanger the population on board; there is also the possibility of falling population levels or a significant level of incest destroying the creatures on the craft, thus rendering the ships pointless. The latter two can be quite easily prevented; the first is largely down to luck.
Generation ships can, therefore, become mankind’s path to interstellar colonisation. Imagine them as smaller, completely mobile Earths, capable both of sustaining anything alive on it and transporting those inside to a specific destination.
Of course, Generation ships thus prove to be remarkably like a planet in sustaining the population aboard.
This leads to a new concept: artificial ‘planets’. Admittedly they’re a lot less hardwearing than the Earth or Jupiter, but they can reliably sustain a populace with the ability to fix them should anything routine go wrong. Now follow the thought of an artificial planet like this to its logical conclusion: instead of spending millions of pounds on fuel and so on to enable the Generation ship to actually move to another solar system, just give them a supply large enough to maybe move out of the way of asteroids and similar things. A huge saving that also eradicates the need to find natural, human colonisable planets, which are thought to be relatively rare.
Eventually, the Solar System may have hundreds of Generation ships just sitting there motionless, each acting as a tiny planet. Humanity finds a way to solve all of its population and survival problems in one stroke, just like that.
Of course, there is always the building of Generation ships in the first place. This could turn out to be a long, difficult project for the first but others, easier, faster, cheaper to create, would be built soon after. The only limitation here is finding the resources to undertake such a colossal project, which is where the original purpose of the ships comes in: build a few with the necessary supplies of fuel and send them to find resource rich worlds; once such planets are found, harvesting from them would be a relatively easy
process.

Gradually the number of ships would increase, slowly at first, but speeding up as technology improves and more mineral rich planets are utilised. Humanity would have established the beginnings of a space empire.
It is at this point that things turn dangerous. Perhaps we make contact with other civilizations at this point, or perhaps we established contact a few centuries before, but eventually humanity might decide that it likes the idea of having a space empire, and so it develops powerful weapons, perhaps even designing and creating a new type of Generation ship specifically to transport and feed armies. Weapons would be relatively simple with the advances already made and eventually our destructive potential outweighs anything else nearby. At this point we begin a bloody conquest of our alien neighbours’ civilizations.

Of course, such a scenario depends on both the existence of alien civilizations and the ability of mankind to overcome its natural survival instinct, greed. For the first, the likelihood of humanity being alone in the galaxy, never mind the universe, is so miniscule that it can almost certainly be discounted; the technological level and closeness of any other lifeforms remains, of course, unknown. As for the latter: humanity has been responsible for more deaths than virtually any asteroid in history, all in the name of progress; and we don’t exactly have a great track record when it comes to controlling ourselves when we get a new toy to play with. First it was steam power: imagine the effect the Industrial Revolution had on the environment. Then we came across oil and the concept of burning it and making things out of it; then it was nuclear power: think of the sheer destructive power inherent in strong radiation and, by extension, nuclear weapon fallout and you’ll soon see why the initial explosion is perhaps akin to the frying pan in the classical proverb; the explosion is probably preferential to the ‘fire’, the radiation afterwards.
If alien civilizations exist close enough then you can be sure that one day there will be a war; the casualties likely being some hundreds, possibly thousands, of times greater than World War I, World War II and a hypothetical World War III combined.
The victor in such a war? Who knows? Humanity is certainly very resourceful, but superior technology will play a great part, depending on which side possesses it.
But I digress.
The point is that Generation ships will be at once the result of an event that will act as a catalyst (the development of cold fusion, perhaps, enabling the ships to be very easily powered) and will themselves be the catalyst for further expansion. From the Earth as original home to the Moon as forward base to real planets as gigantic mines to artificial constructs as worlds to live on. The next chain in the sequence may be something even more wondrous: perhaps, with resources and manpower being no object, the first steps toward FTL travel and manipulation of gravity (including the creation of antigravity
and, perhaps more useful in some ways, artificial gravity [current theories for the creation of artificial gravity generally assume that a way to work neutronium will be discovered, but will this be necessary as other, more pliant suitable elements are discovered? (perhaps as the cold remnants of the cores of dead neutron stars?)]) will be made, and humanity will eventually end up being able to travel the massive distances involved in space without resorting to concepts like Generation ships; the advantages of FTL travel are immense, including the (to outside eyes) extension of life granted to those who approach and even surpass light speed1 .
The entire concept of Generation ships can thus be explored to give some fairly amazing results. What is more interesting, though, is that work on a Generation ship could be started now with a reasonable chance of success. Plants could be taken aboard to recycle the CO2 produced by humans back into breathable oxygen. The oxygen, combined with hydrogen (the most common element in the universe) could be used to create drinkable water, which could in turn be used to water the plants. The plants could be various types of food crop, thus solving the problem of food, and there are many byproducts of human activities that could potentially nourish such crops. Metals of all types are present in large quantities to build the actual craft, which could be any shape imaginable if it were to be built in space or even on the Moon (on Earth there are two possibilities: either the craft is launched directly into space from the surface, thus requiring a standard space shuttle shape or it could be taken into orbit in the hold of a large space shuttle, requiring no actual launch under its own propulsion whatsoever) as friction and drag are not a problem once in space.

Communications could be done using radio or laser pulses in certain codes, perhaps even an adapted version of Morse Code. The only difficulty of any importance is fuel; perhaps nuclear fission, or solar cells, could provide the energy required (solar cells being particularly good in space where there is not an atmosphere to block the Sun’s light). Indeed, there are many satellites utilizing solar power with far greater efficiency than on Earth.
Getting an initial population might prove to be difficult; the idea of dying before the journey’s end would quite quickly discourage those desiring to see new worlds, while very few people would desire the danger posed to such a craft by space debris; small particles of asteroid dust and so on or even a full-blown asteroid itself, if the course is calculated wrongly. The prospect of helping humanity to reach for the stars, as it were, might encourage a bold minority to step forward, but otherwise there is very little incentive for a sane person to go until there is a reasonable prospect of the journey lasting a much shorter time; although the sights, of course, would be stunning.
Assuming that an initial population large enough to prevent inbreeding and population decline could be found, though, we could, as has been said, start building Generation ships now. Indeed, the benefits to such a project are tangible and enormous, thus leaving the question: why isn’t more research being concentrated on the topic, and why hasn’t work on a suitable craft been started already?

The most obvious reason is, of course and as per usual, money. Research is expensive, especially if the work done is of a practical nature, as it would be by necessity for Generation ships. The actual building of a Generation ship would, similarly, be enormously expensive for the government involved. The lack of Generation ships could also be attributed to the essentially short-term thinking done by the leaders of the nations most able to build a Generation ship; most of these nations are democracies where the public are permanently demanding better healthcare, better education, a better police force and so on. The government of such a nation can only ultimately be interested in staying in power and being reelected; under such circumstances long-term views are a disadvantage; they get in the way of pleasing the populace.
Generation ships are an essentially long-term concept. No immediate benefit would arise from building one, except perhaps an increase to national reputation in diplomatic circles, but even this would be minor. On the other hand, the short-term disadvantages to starting such a project are, though relatively few, quite profound. As with space elevators (which as of yet are infeasible due to the properties required of any material used in it, unlike Generation ships, although we are getting close to the ideal materials for a space elevator with the gradual refining of carbon nanotube technology) the initial cost would be amazingly expensive (although with both concepts the initial cost is really all that matters; in the long-term you actually get far more back than you put in; maintenance is simple and, thus, inexpensive) and any government spending such an amount of money would either be ridiculed by its own press for spending so much on something which (to them) has no discernible advantages, compared to spending the money on something useful such as, oh, education or the healthcare services.

Which is not to say that there’s something wrong in valuing a good health service or education above a Generation ship; indeed, quite the opposite. It is just that the long-term advantages to building a Generation ship are immense and, perhaps, a small portion of the national budget each year could be thrown into the building of one. Admittedly it would probably get scrapped by the next different government to come into power, but it might not…
The future of the Generation ship concept is uncertain. Though it is extremely likely, it cannot be said for certain that even one will ever be built. If it is built though, then it will indubitably be the defining moment of that era; it is difficult to imagine anything which could even come close to the amazing effect a successful Generation ship could have on humanity. It would certainly increase the likelihood of survival for the human race; if the Earth is hit by an asteroid then the colony planets would survive and could soon reclaim Earth. Generation ships offer us a way of exploring the furthest reaches of the Galaxy and, eventually, the Universe itself, without resorting to the traditionally impractical science fiction technologies (such as ‘warping’ by any means up to and including the joining of two wormholes to travel through, a task that would not only require a stupendous amount of energy but also faces major technical difficulties [the sheer danger being one]) or possible but impractical technologies that we already have.

1 ‘Outside’ being the operative word; according to Einstein’s Special Theory of Relativity, time is experienced differently depending on an object’s speed; as you approach light speed time slows down immensely for you but not others who aren’t travelling at near-light speed (so that fifty years for everyone else could pass in a matter of seconds to yourself). In this way a person can travel at light speed and come back being younger than those who were younger than he when he left (in other words, a sixteen year old
father could come back to a son who is, say, a year older than himself).

So.... That was it. If you understood it, then well done. If you didn't then I suggest that you visit Wikipedia and get yourself some knowledge.

Just wondering what you think. Good? Bad? Too long? Too short? Doesn't touch the right subjects? Science is horrifically wrong (I certainly hope not! Physics is one of my specialities.)?

Right now, we have only one thing preventing us from feasibly doing a generation ship: a sufficiently non-porous and radiation resistant hull material. Nothing we have today, short of masses of rock (and I'll explain why that isn't a great idea in a minute) will prevent nitrogen loss and stop cosmic ray bombardment.

Nitrogen has an amazing ability to slip through even apparently solid materials. It does this quite well with metals, somewhat less well with ceramics, but it still gets through. And we need nitrogen as the primary buffer gas in the air we breathe.

Cosmic rays (VERY high energy wavicles) go through our current spaceship and spacesuit structures without even really noticing them. The only thing that stops them on earth is our nice thick atmosphere and radiation belts/magnetic field. Fortunately, they don't do much damage; our astronauts can be (and in some cases, have been) exposed to them for a year or more without demonstrable side effect. But exposure for generations is another question entirely; increased cancer and mutation rates could bring about exactly the kind of declining population that would doom any mission.

Massive rock cladding would seem the obvious solution, but actually isn't a solution at all. It's just too heavy. The heavier you make the ship, the more fuel you'll need; the more fuel you need, the more WEIGHT of fuel you must carry; the more weight of fuel, the EVEN MORE fuel you need. This kind of calculation can spiral out to the utterly ridiculous far too quickly.

So, until you can find a material that's nitrogen non-porous, cosmic ray proof and light, a generation ship remains non-possible.

Right now, we have only one thing preventing us from feasibly doing a generation ship: a sufficiently non-porous and radiation resistant hull material. Nothing we have today, short of masses of rock (and I'll explain why that isn't a great idea in a minute) will prevent nitrogen loss and stop cosmic ray bombardment.

Nitrogen has an amazing ability to slip through even apparently solid materials. It does this quite well with metals, somewhat less well with ceramics, but it still gets through. And we need nitrogen as the primary buffer gas in the air we breathe.

Cosmic rays (VERY high energy wavicles) go through our current spaceship and spacesuit structures without even really noticing them. The only thing that stops them on earth is our nice thick atmosphere and radiation belts/magnetic field. Fortunately, they don't do much damage; our astronauts can be (and in some cases, have been) exposed to them for a year or more without demonstrable side effect. But exposure for generations is another question entirely; increased cancer and mutation rates could bring about exactly the kind of declining population that would doom any mission.

Massive rock cladding would seem the obvious solution, but actually isn't a solution at all. It's just too heavy. The heavier you make the ship, the more fuel you'll need; the more fuel you need, the more WEIGHT of fuel you must carry; the more weight of fuel, the EVEN MORE fuel you need. This kind of calculation can spiral out to the utterly ridiculous far too quickly.

So, until you can find a material that's nitrogen non-porous, cosmic ray proof and light, a generation ship remains non-possible.

The problem of increased cancer and mutation rates is slightly balanced by a large population, though; I really don't know how large, so it might be infeasibly large anyway.
As for the problem of material: I didn't consider such a thing. Darn it.
And I can't think of an answer.

I'm not sure how relevant the constraints of fuel are. i mean providing you don't want to do anything special, starship enterprise stuff, you only need to start off, and then decelerate when you reach your target, with a little bit of thrust to keep your speed up.
Starting off, the initial thrust can come from sort of catapult of some sorts, then perhaps some sort of breakaway boosters. Keeping the speed up probably won't take up a lot of fuel. Then the only thing you have to worry about is stopping when you get there.

I'd have a sort of system of probes, manned or unmanned that you can launch a few years before you reach your target system, to make sure it is where you want to colonise. if it isn't then you can try to bunce off in a different direction using the system's gravity. Actually stopping at the system of choice would be a bit more involved, youd want some sort of one off booster sysem or something.

Nice article...if you can find a material that would work according to Dododecapod's specifications and exposit on it in the article itself I'd say it'd be perfect.

I'm not sure how relevant the constraints of fuel are. i mean providing you don't want to do anything special, starship enterprise stuff, you only need to start off, and then decelerate when you reach your target, with a little bit of thrust to keep your speed up.
Starting off, the initial thrust can come from sort of catapult of some sorts, then perhaps some sort of breakaway boosters. Keeping the speed up probably won't take up a lot of fuel. Then the only thing you have to worry about is stopping when you get there.

I'd have a sort of system of probes, manned or unmanned that you can launch a few years before you reach your target system, to make sure it is where you want to colonise. if it isn't then you can try to bunce off in a different direction using the system's gravity. Actually stopping at the system of choice would be a bit more involved, youd want some sort of one off booster sysem or something.

Generation ships are expected to travel for thousands, if not hundreds of thousands, of years, though. That's a pretty major amount of fuel needed.

Nice article...if you can find a material that would work according to Dododecapod's specifications and exposit on it in the article itself I'd say it'd be perfect.

Yay! Some praise! :D

Generation ships are expected to travel for thousands, if not hundreds of thousands, of years, though. That's a pretty major amount of fuel needed.

The only fuel you'd need would be to do minor corrections. Once you're in space and out of Earth's gravity field, you can use the gravitational pull of the various stars on your way to get where you're going. IIRC, of course.

The only fuel you'd need would be to do minor corrections. Once you're in space and out of Earth's gravity field, you can use the gravitational pull of the various stars on your way to get where you're going. IIRC, of course.

Would the fields be really significant enough?
If, for example, we used Jupiter in such a way, how difficult would it be to get to the next planet while only making minor course corrections? And then there is the sheer openness of space; the nearest star to a given point is often many light-years or even parsecs away. Over such massive differences any movement caused by the gravity of as small an object as a star would be very slow.

Edit: What does IIRC stand for, by the way?

Would the fields be really significant enough?
If, for example, we used Jupiter in such a way, how difficult would it be to get to the next planet while only making minor course corrections? And then there is the sheer openness of space; the nearest star to a given point is often many light-years or even parsecs away. Over such massive differences any movement caused by the gravity of as small an object as a star would be very slow.

Edit: What does IIRC stand for, by the way?

Good point. I seem to recall a book where such a propulsion system was used, but only for inter-system transport, rather than going outside a solar system. Might no work so well in the vasty nothingness of space.

And IIRC stats for If I Recall Correctly.

Might of missed it but i'm suprised you did'nt mention the implementation of a Bussard ramjet.

Personally I've always thought an alternative to building such a ship would be to install a colony inside a large enough asteriod. Fit an engine and set it of into space. As the population grows they'd be able to expand through the asteriod, they be able to harvest useful resources from it, and so on.

The most reasonable source of materials for such a vessel is asteroid mining. No need to make planetfall anywhere.

Might of missed it but i'm suprised you did'nt mention the implementation of a Bussard ramjet.

Personally I've always thought an alternative to building such a ship would be to install a colony inside a large enough asteriod. Fit an engine and set it of into space. As the population grows they'd be able to expand through the asteriod, they be able to harvest useful resources from it, and so on.

Even with the engine there would likely be the danger of colliding with objects, and in any case the resources from a single asteroid, the useful resources for a colony at least, would likely not last long.
And I didn't mention a Bussard ramjet, no. :D

@Khadgar:
But another aim of Generation ships, the principle aim, is the colonisation of new planets.

Well, considering the leaps and bounds being made in the ceramics field today, we can vastly increase the storage capacity of our current batteries. This of course is not a solution for the entire energy problem of such generation ships, but a means to an end. In addition, to the battery type of ceramics, we have ceramics being created that exceed the heat parameters and structural parameters of most metals, in addition to having less mass per unit. Ceramics could indeed provide some essential portion of outer hulls on these generation ships.

I attended a seminar by some prominent research physicists from CSM who had some interesting models on wave-particles and how to manipulate them even more then we already do. One of the researchers suggested that within 10-20 years we could have energy-matter conversions taking place at a greater frequency then we currently observe. This means that we do have such conversions taking place, and it's only a matter of shrinking the costs of doing so.

In my mind these so-called "conversions" are really just a difference in orders of magnitude of energy. Matter being one of the lowest. So it could be possible to simply boost matter's energy level to such an extent and with the correct wavelengths/wave patterns as to cause energetic release which could then be used.

Generation ships might be dependent upon this type of knowledge in order to be practical.

The costs involved with a project like an orbital colony are truly staggering (before you even think about moving it). Aside from the cost in resources, the technological needs of such a ship are so far in the future it is not really worth considering as anything other than as intellectual masturbation. By the time humans are capable of traveling to another star, technology will have advanced so much we cannot realistically conceive of the capabilities today.

Someone has already pointed out that you will have some leakage through the hull. This is a basic fact you will need to deal with. While it can be made fairly irrelevant for short trips a ship capable of reaching another star system will need to be able to counter hundreds of years of loss.

There will be losses in every system – nothing has perfect efficiency (and today’s technology is far from it). Nutrients for organic life, energy to power basic systems, basic hull material for repair – everything will have to be brought along in absurd abundance to ensure viability. Long term maintenance will be a significant issue – since carrying enough spare parts for every contingency would be ludicrous, you will need fabrication systems available to reproduce the ship.

The hull will have to be practically self-healing to withstand long-term exposure to the constant collisions (space is not empty – even the smallest of particles causes damage at high speeds). It will also have to be able to shield the ship from radiation and electromagnetic disturbances.

While cosmic ray damage to healthy adults may be tolerable in the short-term, it will not be tolerable for a lifetime. It certainly will not be tolerable for breeding. Multi-generational ships will not be possible until the problems with outside radiation are solved. The first colonist outside the earth will have to be sterile as the risks of mutations and developmental problems would render reproduction too dangerous.

A potential exists for creating a humongous cylinder with a thick self-repairing structure filled with water as a hull. The water will help the radiation shielding as well as being a convenient place to store it. Spin the cylinder to provide some sort of gravity. Carry enough additional matter to counter loss into space, additional nutrients for organics, and whatever fuel you use to power the ship for the journey plus significant reserves (it would be too expensive to risk failure – significant redundancy would be needed).

Research has shown that a helium atmosphere would be preferable to a nitrogen one (human body actually works better) – thought this increases the loss through the hull, it should be easier to replace with either interstellar medium or solar wind.

The earlier suggestion of solar power is only feasible for a colony staying close to a star – you would not be able to get significant light during the journey. Not to mention the power requirements of such a ship would be immense – you would have to cover the ship in solar panels, which have to be replaced fairly often to compensate for damage and clean the dust off them.

This is such an immense undertaking that it will require volumes of information to discuss in any reasonable fashion – otherwise it is just a schoolboy’s musings.

NASA asked a few tentative questions on orbital stations – it is a few decades out of date now, but the issues raised would be a platform to build on. I recommend you lookup some of those papers.

Are you suggesting there's something wrong with incest?

Another problem with this is the number of people you need to support the ship's people. Not just the enginers, but teachers, doctors, dentists, cooks, and so on. Beyond that, how do you make sure that such jobs are filled after the first generation dies off? How will children be educated onboard to keep the ship in one piece and ship's personel happy (Not to mention how do you plan to keep them entertained)?

Another problem with this is the number of people you need to support the ship's people. Not just the enginers, but teachers, doctors, dentists, cooks, and so on. Beyond that, how do you make sure that such jobs are filled after the first generation dies off? How will children be educated onboard to keep the ship in one piece and ship's personel happy (Not to mention how do you plan to keep them entertained)?

I would bet that the people on the ship would do all of that without much help just to make sure they survive. I'd liken these to small, self sufficient villages that are far from human contact on Earth. Kind of. *Didn't read massive posts*

I would bet that the people on the ship would do all of that without much help just to make sure they survive. I'd liken these to small, self sufficient villages that are far from human contact on Earth. Kind of. *Didn't read massive posts*
The problem with that is the technology level needed to keep said ship going will require a pretty advanced education system and an open culture, the type that wouldn't be good with, say, forced learning or jobs.

Are you suggesting there's something wrong with incest?

I think the problem is that the OP is using the term 'incest' when they actually mean 'inbreeding'. Seems to make much more sense if you read it that way.

I'd rather wait until we can harness wormholes for effectively FTL transportation. Generation ships would be an interesting idea, but I could see a lot of psychological, health, and population problems stemming from that model relative to the benefits.

If you were to use slower-than-light means, I'd say suspended animation would be a better idea.

I think the problem is that the OP is using the term 'incest' when they actually mean 'inbreeding'. Seems to make much more sense if you read it that way.

Oh, so there isn't anything wrong with incest?

I'd rather wait until we can harness wormholes for effectively FTL transportation. Generation ships would be an interesting idea, but I could see a lot of psychological, health, and population problems stemming from that model relative to the benefits.

If you were to use slower-than-light means, I'd say suspended animation would be a better idea.

I'd say that suspended animation would be a great idea, insofar as it means keeping the body relatively inactive while the brain remains in use. i know I'd want to be learning while traveling. Perhaps some sort of induced connection to a computerized library. Sounds a bit matrix-esque, but I suppose it's not too far removed from stasis. In fact, I don't see why the suspended animation chambers couldn't be rigged to provide electrical stimuli to the various muscle groups to retain tone and structure.

*ponders the use of suspended animation to gain muscle mass while learning to use the internet with only the brain.*

I'd say that suspended animation would be a great idea, insofar as it means keeping the body relatively inactive while the brain remains in use. i know I'd want to be learning while traveling. Perhaps some sort of induced connection to a computerized library. Sounds a bit matrix-esque, but I suppose it's not too far removed from stasis. In fact, I don't see why the suspended animation chambers couldn't be rigged to provide electrical stimuli to the various muscle groups to retain tone and structure.

That would be a pretty good idea. And if you were to run the simulated reality so that the person was not aware they were in a simulation during that time, it could avoid psychological problems and boredom very easily. You would likely adjust the brain's subjective perception of time while in the simulation to make it last longer or shorter depending on the exact needs of the crew and the destination itself.

*ponders the use of suspended animation to gain muscle mass while learning to use the internet with only the brain.*

That would be pretty cool on Earth as well as in space travel...

The cosmic rays won't be much of a problem. The atmosphere has the same column depth as ten meters of water. Put the people at the center of the ship with more than 1000 g/cm^2 of equipment and supplies and hull and stuff around them.

Why settle for ships? Build a ringworld or dyson sphere, and use the star as the engine (sort of like a ramjet). Solves the problems of supplies, atmosphere, inbreeding and energy usage quite nicely.

I think the biggest hurdle is energy usage. How could you generate enough energy to maintain even a small society for several years, nevermind generations?

The atmosphere, radiation, hull and propulsion problems are, at least in theory, easily addressed. The former three is simply a matter of manufacturing an extremely large craft, spinning to maintain 1g, with an outer hull consisting primarily of a dense layer of ice, and the right combination of hydroponics to maintain the atmos, and a fucking huge ramjet.

Nitrogen has an amazing ability to slip through even apparently solid materials. It does this quite well with metals, somewhat less well with ceramics, but it still gets through. And we need nitrogen as the primary buffer gas in the air we breathe.I don't think we necessarily need nitrogen; helium for example has also been used (continuously, for a number of weeks, IIRC) in deep sea environments. Although I have my doubts whether helium, specifically, would be less prone to seep through the hull of a ship.

Why settle for ships? Build a ringworld or dyson sphere, and use the star as the engine (sort of like a ramjet). Solves the problems of supplies, atmosphere, inbreeding and energy usage quite nicely.I don't think a star has sufficient energy output to propel itself across the galaxy. It's rather massive after all. Although, admittedly I haven't done any calculations on it.

I don't think we necessarily need nitrogen; helium for example has also been used (continuously, for a number of weeks, IIRC) in deep sea environments. Although I have my doubts whether helium, specifically, would be less prone to seep through the hull of a ship.


Unfortunately, you're right about helium. It's actually more "slippery" than nitrogen. All of the Noble Gasses show this property, but naturally, the larger the individual atom the harder it is for it to slip through the interstices of the materials.

I wouldn't want to try with helium anyway. The experiments with it in the depths have shown some significant problems, ranging from core body chilling to bone necrosis.

So, until you can find a material that's nitrogen non-porous, cosmic ray proof and light, a generation ship remains non-possible.

Interesting problem. What about a laminate layer of liquid nitrogen surrounding the inner (pressurised) hull? Any leeching nitrogen would presumably merge with the liquid mass... and cosmic rays (from what I've read) primarily are stopped in our own atmosphere by oxygen and nitrogen.
I wonder how thick the layer would have to be to have the same effectiveness!

I think the liquid nitrogen would still leak out?

I think the liquid nitrogen would still leak out?

I'm not sure. With the relatively low energy state of the molecules in a liquid, I don't know how well the atoms would slip through...

This bears researching.

It would really help if we could get nearer to lightspeed for travel; not only would you get to a destination faster, but time would slow down for you as well. If we could get to within one thousandth of the speed of light (i.e. 0.999 c), that newly discovered earth-like planet would be reachable in a perceived year of travel (it's about 20 lightyears away, and at that speed time goes about 22 times slower for the traveler).

It doesnt matter what form it is in, you are still going to loose a lot of material out through the hull, including the hull itself (though perhaps not such a significant amount). Simple fact of traveling through space.

This means you need to keep a lot on hand. Helium and hydrogen you can pick up from the interstellar medium, but that is practically it. Anything heavier you will only really be able to pick up near a star.

As far as the 'suspended animation'/matrix comments go... how exactly do you expect to retard the body while still keeping the brain functioning? The brain is not some bit of computer circuitry housed in a biological body - either the entire body (including the brain) is frozen or none of it is.

It is certainly possible to freeze someone and revive them later, but though the body can be preserved and return to functioning, I have no idea if your mind will survive the process. Not much use if you have a bunch of brain dead but breathing bodies. Nevertheless, this is a possibility and far more practical than multi-generational ships.

As far as energy is concerned - it is plausible to consider hydrogen fusion. There is plenty to scoop up along the way so perhaps there is enough to power a sufficiently efficient ship for the journey.

I don't think a star has sufficient energy output to propel itself across the galaxy. It's rather massive after all. Although, admittedly I haven't done any calculations on it.Well... I haven't exactly done the math, but I'm thinking something like our own Sun has sufficient energy output to accelerate itself.

A stellar engine which converts a portion of the star's energy output into thrust is known as a Shkadov Thruster. Essentially, the idea is that you create a tremendous solar sail structure on one side of the star. The radiation on that side of the star is then redirected, causing a huge differential in the radiation pressures of each side. This radiation pressure difference would (very) gradually accelerate the star in the direction of the reflecting sail. It would take a while to get going, but make no mistake, it would provide sufficient energy to propel itself.

In regards to the hull, why not "grow" one. A biological hull would easily repair any damage and could also act as a massive air recycler?

Edit: Would look cool too
http://kofler.dot.at/40k/units/Tyranid_Leviathan_Hive_Ship.gif

In regards to the hull, why not "grow" one. A biological hull would easily repair any damage and could also act as a massive air recycler?

But how would it survive the vacuum of space or the extreme cold/radiation?

But how would it survive the vacuum of space or the extreme cold/radiation?

We have enough life forms of various types here on Earth that would most likely fit those requirements in one way or another. What you would have to do is bio-engineer the best traits of lifeforms on Earth into one new living organism that we could shape to our needs.

We have enough life forms of various types here on Earth that would most likely fit those requirements in one way or another. What you would have to do is bio-engineer the best traits of lifeforms on Earth into one new living organism that we could shape to our needs.

And what prevents it from attaining sentience and going "Time to poop humans."

It would really help if we could get nearer to lightspeed for travel; not only would you get to a destination faster, but time would slow down for you as well. If we could get to within one thousandth of the speed of light (i.e. 0.999 c), that newly discovered earth-like planet would be reachable in a perceived year of travel (it's about 20 lightyears away, and at that speed time goes about 22 times slower for the traveler).

Interesting, now question is why does time slow down at near the speed of light? I actually do not remember hearing this before. Is there a simple reason for it?

And what prevents it from attaining sentience and going "Time to poop humans."

Well was thinking of some kind of plant-fungi organism. Not a intelligent thinking animal.

I'm suggesting something like fungus grafted onto a metal frame. Not a giant space whale or anything.

We have enough life forms of various types here on Earth that would most likely fit those requirements in one way or another. What you would have to do is bio-engineer the best traits of lifeforms on Earth into one new living organism that we could shape to our needs.

Well, I do know that there are extremophile bacteria that can survive in space, as well as extreme heat/cold. If you were to find a way to scale that to a larger organism, you could probably do this.

Interesting, now question is why does time slow down at near the speed of light? I actually do not remember hearing this before. Is there a simple reason for it?

It's not so much that "time slows down" at near-light speeds. What happens is that a time dilation effect due to your near-light speed makes time everywhere that isn't moving at relativistic speeds occur at a "slower" rate than it does for you.

In fact, there's a nice, handy equation that can tell you how much of a time dilation effect you'll have based on your speed.

t = dt/(sqroot(1-(v^2/c^2)))

So if you were moving at, say, sqroot(0.75)c (I use this number because it makes the math significantly easier) then you'd have:

t = dt/(root(1-0.75)) = dt/(root(0.25)) = dt/(0.5) = 2dt.

So for every second that happens in your relative time frame, 2 seconds pass at considerably smaller velocities. So if you moved at a speed of the square root of 0.75 * the speed of light for 10 years, 20 years would pass everywhere else.

But how would it survive the vacuum of space or the extreme cold/radiation?

We're actually making steps toward a proper understanding of the current proof of concept right now in our study of extremophile organisms and their coping mechanisms. On a purely theoretical note, we could deal with vacuum by giving the vessel a dense, structurally reinforced hide/shell to withstand the vacuum pressures and having extremely high efficiency redundant sphincters at entry/exit points -- basically organic airlocks.

The cold is less of an issue than the radiation, as we have already discovered some terrestrial microbes able to withstand extreme temperatures in either direction. It would be a matter of extrapolating the factors contributing to their hardiness to a larger-scale organism. Difficult, perhaps, but doable.

Radiation is tough to deal with on several levels, but one of the better solutions would be some sort of robust self-repair mechanism with "auditing" measures (an improved version of our DNA proofreading mechanisms, for example) set in place to ensure that undue amounts of mutation and cancer don't run unchecked.

See: http://www.washingtonpost.com/wp-srv/national/science/daily/daily/oct99/spacebugs4.htm for reference to organisms surviving the vacuum of space for at least limited periods of time.

As well as http://en.wikipedia.org/wiki/Extremophile for the wikipedia index of organisms which are capable of thriving in patently unreasonable conditions.

I'm suggesting something like fungus grafted onto a metal frame. Not a giant space whale or anything.

That would probably be a good choice. Fungi eat dead organisms, so the hull itself could help manage trash and waste problems, and considering that fungi are considerably easier to bioengineer than a larger organisms, finding ways to make it resistant to space and other extreme environments.

Plus, the ship itself, if it were capable of photosynthesis of one form or another, it could be used to help terraform the new planet.

That would probably be a good choice. Fungi eat dead organisms, so the hull itself could help manage trash and waste problems, and considering that fungi are considerably easier to bioengineer than a larger organisms, finding ways to make it resistant to space and other extreme environments.

Plus, the ship itself, if it were capable of photosynthesis of one form or another, it could be used to help terraform the new planet.

They also tend to spore, and those spores tend to grow into new fungi in unpleasant places.

snip. .

Ahh I see what you talking about now. You could basically travel to the "future" using this method.

Interesting, now question is why does time slow down at near the speed of light? I actually do not remember hearing this before. Is there a simple reason for it?Yes. It happens because the speed of light is universal. The effect is known as time dilation. (http://en.wikipedia.org/wiki/Time_dilation)

I'm not sure if the simple explanation makes any immediate sense to you (it didn't to me), but a comprehensive explanation is.. Well.. Comprehensive.

They also tend to spore, and those spores tend to grow into new fungi in unpleasant places.

You'd need a protective layer between the hull and the inside. I don't think anyone would want to spend time inside an organic ship, with all the humidity, and the smell, and the growing stuff.

It reminds me a little too much of Aliens...

Ahh I see what you talking about now. You could basically travel to the "future" using this method.

Think of it more like...letting time flow faster around you. You're always moving to the future, just by sitting there, this just makes you move to the future at higher rate of change, if that makes sense.

Think of it more like...letting time flow faster around you. You're always moving to the future, just by sitting there, this just makes you move to the future at higher rate of change, if that makes sense.


Yeah I am understanding the principle. It is fairly basic as described.

Well I would suppose if one were to go just off earth in a craft and flew in a circle for a year at .999c. Then land back on earth you would be in the "future" and you would only be 1 year older. I would imagine it would be an easy way to invest money in land or the stock market. Over the course of 20 earth years you would get a decent rate of return. One could take a year vacation in a luxury spacecraft and come back a lot richer hopefully.

Yeah I am understanding the principle. It is fairly basic as described.

Well I would suppose if one were to go just off earth in a craft and flew in a circle for a year at .999c. Then land back on earth you would be in the "future" and you would only be 1 year older. I would imagine it would be an easy way to invest money in land or the stock market. Over the course of 20 earth years you would get a decent rate of return. One could take a year vacation in a luxury spacecraft and come back a lot richer hopefully.

the one problem is that to accelerate a vessil that one could live in for a year to .999c would take more energy than our sun would output in its lifetime.

the one problem is that to accelerate a vessil that one could live in for a year to .999c would take more energy than our sun would output in its lifetime.

I am assuming under our current technological know-how. I am also assuming that there is a large amount of science we have not discovered yet. There may be a easier way of doing just that out there.

Edit:

Also one could build a small ship and be in suspended animation for a year. Maybe a ship big enough to hold ones body in its cargo bay.

I am assuming under our current technological know-how. I am also assuming that there is a large amount of science we have not discovered yet. There may be a easier way of doing just that out there. It'll always take a near-infinite amount of energy to accelerate a human-sized object to that speed. Our technology doesn't have anything to do with it.
An added problem that technology might be able to solve at some point, is that the process of acceleration would either crush you to a pulp, or take a really, really long time.Edit:

Also one could build a small ship and be in suspended animation for a year. Maybe a ship big enough to hold ones body in its cargo bay.Only problem with that is... How do you wake up again?

But if you solved that, you wouldn't need ships or cargo bays. All it'd require to 'travel' a year into the future, would be a suitable freezer.

Only problem with that is... How do you wake up again?


Assuming you have proper resuscitation equipment? Probably on a timer basis.

A stellar engine which converts a portion of the star's energy output into thrust is known as a Shkadov Thruster. Essentially, the idea is that you create a tremendous solar sail structure on one side of the star. The radiation on that side of the star is then redirected, causing a huge differential in the radiation pressures of each side. This radiation pressure difference would (very) gradually accelerate the star in the direction of the reflecting sail. It would take a while to get going, but make no mistake, it would provide sufficient energy to propel itself.If my calculations aren't off, I get an acceleration of 6.42 10^-12 m/s^2 (assuming we can redirect the entire radiation output in one direction)
Which amount to a whopping speed of ~ 200 m/s in 1 million years. (For comparison the speed of sound is 344 m/s^2)

I'm not sure at what speed the universe is expanding, but chances are this will get you nowhere very very slowly. :p

I'm afraid that I haven't actually read Shkadov's proposal, so I've posted pretty much the sum total of what I know about it. I'm under the impression, however, that the time frame in which it operates is very long but not that long (more like tens of thousands of years rather than millions). Come to think of it, did you include the mass of the planets and asteroid belt? Because those would definitely be dragged along for the ride too, making matters even worse.

Right now, we have only one thing preventing us from feasibly doing a generation ship: a sufficiently non-porous and radiation resistant hull material. Nothing we have today, short of masses of rock (and I'll explain why that isn't a great idea in a minute) will prevent nitrogen loss and stop cosmic ray bombardment.

Nitrogen has an amazing ability to slip through even apparently solid materials. It does this quite well with metals, somewhat less well with ceramics, but it still gets through. And we need nitrogen as the primary buffer gas in the air we breathe.

Cosmic rays (VERY high energy wavicles) go through our current spaceship and spacesuit structures without even really noticing them. The only thing that stops them on earth is our nice thick atmosphere and radiation belts/magnetic field. Fortunately, they don't do much damage; our astronauts can be (and in some cases, have been) exposed to them for a year or more without demonstrable side effect. But exposure for generations is another question entirely; increased cancer and mutation rates could bring about exactly the kind of declining population that would doom any mission.

Massive rock cladding would seem the obvious solution, but actually isn't a solution at all. It's just too heavy. The heavier you make the ship, the more fuel you'll need; the more fuel you need, the more WEIGHT of fuel you must carry; the more weight of fuel, the EVEN MORE fuel you need. This kind of calculation can spiral out to the utterly ridiculous far too quickly.

So, until you can find a material that's nitrogen non-porous, cosmic ray proof and light, a generation ship remains non-possible.

you would need more fuel to propel it during acceleration, but once you're done accelerating, it doesn't matter. so you could just take an asteroid and build your ship inside it, then launch it.

I'm afraid that I haven't actually read Shkadov's proposal, so I've posted pretty much the sum total of what I know about it. I'm under the impression, however, that the time frame in which it operates is very long but not that long (more like tens of thousands of years rather than millions). Come to think of it, did you include the mass of the planets and asteroid belt? Because those would definitely be dragged along for the ride too, making matters even worse.No, I didn't include those. But it shouldn't make much of a difference since they're insignificant compared to the mass of the sun.

you would need more fuel to propel it during acceleration, but once you're done accelerating, it doesn't matter. so you could just take an asteroid and build your ship inside it, then launch it.

If you're talking about using basically strap-on disposable boosters, that's fine. But don't forget that however much acceleration you ramp up at the beginning of the trip, you have to kill that much velocity at the end. And that means fuel - and the more mass you have, the more fuel you need to make a velocity change, up or down.

Having consulted a set of chemistry texts - it appears that liquid nitrogen has the same "seeping" problem that the gaseous version does. Great idea, but not functional, apparently.

Oh, and unfortunately, Bussard Ramjets don't work in our universe. Friction slowdown kills all the advantage of the continuous acceleration, and particle densities in extrasolar space appear to be too light.

If my calculations aren't off, I get an acceleration of 6.42 10^-12 m/s^2 (assuming we can redirect the entire radiation output in one direction)
Which amount to a whopping speed of ~ 200 m/s in 1 million years. (For comparison the speed of sound is 344 m/s^2)

I'm not sure at what speed the universe is expanding, but chances are this will get you nowhere very very slowly. :pWhat's the basis for your calculation? - I just Googled and found an article (http://www.astronomytoday.com/exploration/solartravel.html) on exactly what I suggested... Obviously I'm not very original.