It is known that Alpha Centauri A & B both have habitable zones that could be as comfortable as the one around Sol. To reach Alpha Centauri would take at least 860 years at 1500 km/sec (0.5% lightspeed). This calls for at least a 30-generation starship, where each couple, perhaps representing 1/3rd of the crew, aboard waits at least until age 28 before having children, for a total of perhaps 3 children per couple.

Besides getting Starship "Generations" up to cruise speed, what are the problems associated with this approach to interstellar travel?

1. Heat
2. Recycling
3. Zero growth

The first problem exists because the heat loss by radiation is substantial in interstellar space, where the outside temperature is only 4 degrees Kelvin above Absolute Zero. The best shape for retaining heat would be a spherical ship which is then coated with a polished metal with an ultralow emissivity around 0.01. The surface must be polished regularly to prevent an ice film
from accumulating which would then radiate heat much faster. Then a Uranium nugget is placed at the geometric centre of the spherical ship where it will naturally radiate heat to compensate for radiative heat losses. The ship must be isolated from redundant structures such as the Whipple Shield, Engines, and other external structures. These could be rigged to fly in formation with the habitat structure without touching it. For a
rotating spherical ship with a diameter of 500 meters, a radiative heat loss of 3.282 megawatts would occur, and would require 5.744 million tonnes of 4%-enriched Uranium Dioxide to compensate. This amount of Uranium would take up only 0.46 percent of the total volume of the habitat, if configured into a spherical nugget with a diameter of 83.194 meters. At current market prices this much Uranium would cost at least $517 billion US.

The second problem is recycling. The ship must recycle 100 percent of all materials. I think that this is simply a matter of energy. I think that with enough energy even the most difficult materials can be recycled. However the ship should be designed so that difficult materials are produced in minute amounts. After all, Starship Generations is not supposed to be a "growth"
environment. Zero growth is essential. Of course I have no idea how much more energy would be required above & beyond what would be needed to keep the habitat warm.

I should also point out that it might be very difficult to get a generation starship up to even a modest speed because of the enormous mass required, i.e. structure + uranium core + biomass + machine equipment. This is obviously something we would need substantial experience in understanding what we would need, how much redundancy, etc.

I like this. Let me think a bit and post some thoughts.

Shadow

The engines really are the biggest factor to worry about. If the ship could accelerate at a continuous 1g, then it wouldn't have to rotate (the thrust would produce inertial pseudo-forces that would take the place of gravity) and the ship could get ther in <i>under</i> four years. Thanks to relativity slowing down the time on board the vessel (or contracting the space between the stars from the ships point of view).

Of course a continuous 1 g propulsion (accelerrate half way, turn, decclerate the other half) would require impossibly large masses of conventional fuel. The only thing that would come even close to being reasonable would be nuclear fussion/fission, or matter antimatter annhilation. And producing that much antimatter would be even more expensive than that uranium. Particle Accelerators only produce microscopic amounts of antimatter, and thousands of tons would undoubtedly be required. Storing it is another problem altogether, as antimatter tends to "evaporate" quite rapidly while being stored in cryo-magnetic chambers. Of course, it would seem logical to scale down the acceleration to say 1/2, 1/3, or even 1/4 g. This would sacrifice some of the effect of gravity, and some of the speed, but it would reduce the amount of fuel needed without too great a loss to the trip time.

For a discussion of relativistic interstellar travel, checkout:
http://www.scientium.com/essays/startrip/startrip.htm

They also include the relativistic rocket equations, so you can calculate things such as travel time, max velocity, and mass ratio required to fit a certain travel profile.

~Caleb

I don't actually believe that relativistic interstellar travel is possible because the energy requirements for propulsion increase with the square of the velocity. This becomes absurdly large IMO at speeds exceeding 0.5 percent cee. Therefore I wishfully set my Generation Starship cruise speed at 0.5 percent cee (1500 km/sec), which is also a little more than double the escape velocity of the Sun. Also a "constant power" approach to propulsion would be expected, rather than "constant acceleration", since the most efficient propulsion systems tend to be electrical in nature. With a "Constant Power" propulsion system acceleration is highest initially and drops off exponentially with time. I think you will find the kinematic profile versus power output for the constant acceleration propulsion approach unrealistic.

I previously stated that using 4% enriched Uranium fuel rods typically used in commercial nuclear power plants would provide naturally radiated heat while "unstacked" to prevent a chain reaction. However if the Uranium were further enriched to produce weapons-grade material (95% U-235 isotope) then the mass of the core could be reduced 23-fold. Therefore a Weapons-Grade Uranium Core would mass a comparatively small 242,000 tonnes. Because Uranium is so dense this core would take up only 0.02 percent of the space inside the Habitat. In an "unstacked" configuration the core would radiate at a "natural" rate and keep the 500-meter diameter Habitat at a balmy 20 deg.C for millions of years. However in a stacked configuration a chain reaction would ensue giving this material obvious alternative purposes such as additional electrical power, astroid mining explosives, Orion-type propulsion, asteroid deflection, etc. However stacking the fuel rods, as in a nuclear power plant, would accelerate depletion of the radioisotope and it would be useless in as little as 1 year. Unstacked the uranium fuel would last millions of years.

Weapons-Grade Uranium would provide an efficient, low-mass, and reliable heat source for the Habitat.

Before we head out in this direction, can we at least check out a bio sphere in antratica for 30years with a dozen couples? It will make good drama if we broadcast time to time what is happening and money could be raised to support such a program. After 10 years, we could send the that or another team to Mars as the first colony. Then we talk about a deep space journey. We could go to a satellite of jupiter and settle down there too.

Success_Machine

I tend to agree with kmguru on this one. As bad as I would wish to see the start of interstellar travel (especially within my lifetime) I think that we will have to fine tune up to it. There are still a bunch of problems to be wrestled with and reasonable solutions to dealt out before we can jump to the task of long distance travel. Dang I hate to say that!

...but with that a given, please continue on with this discourse. It educates even so.

The question that underlies many discussions about interstellar colonization is: How many people would we send? What is the minimum viable population that would guarantee genetic diversity and survivability under environmental stress? There are literally thousands of statistical studies on this subject and they all pretty
much agree:

1. To maintain a high level of genetic diversity requires at least 1000 individuals.
2. To guard against common environmental effects requires 1500 individuals.
3. A population of 10,000 individuals would have a 99% probability of not going extinct within the next 1000 years even with extreme environmental catastrophes (of the natural sort).

References:
MVP Under the Endangered Species Act


The living quarters for 10,000 people could easily fit inside a 500-meter diameter sphere. Under 1-g rotation each person could enjoy a 1000 square-foot bungalow-style home with 10-foot ceilings, and still take up less than 1.2 percent of the Habitable Volume. Of course there must be larger areas for hydroponics, recreation, industrial machines, etc.

With a 242,000 tonne weapons-grade uranium core to keep the temperature steady at 20 degrees C for the entire 860-year trip to Alpha Centauri (and thousands of years thereafter) I see no reason to expect environmental catastrophe - except those that would kill everyone on board instantly.

A fleet of ships numbering from 50-100 vessels should be sent IMO to guard against those most lethal catastrophies such as meteor impact, civil war, nuclear meltdown, lethal plague, etc. These city-ships would maintain a respectful distance while flying in formation on their way to Alpha Centauri. Their territorial isolation would foster diplomatic communication skills, diversity of
governance & law, and variety of lifestyles - even resettlement and migration from one generation to the next. For example if one ship had to be abandoned then the 99 other ships could each accept 100 people with minor effect. The Generation Starships would take 860 years to reach their destination, for a total of 30 childbearing generations, or twelve human lifetimes of 75 years. A proper age pyramid should be built into the population to ensure that the number of people on board will tend not to change dramatically, and that childbearing & death
happen regularly rather than in spurts every 28.6 years.

An interesting aspect of this is that the same requirement exists to have a viable colony on Mars, or the Moon. Wherever we go we need to settle at least 1,000 and preferably 10,000 people. Add this to the requirement for artificial gravity: Since humans cannot withstand more than 2 rev/min a rotating spacecraft has to be at least 1/2-kilometer in diameter. NASA did not build such a monstrosity in low-earth orbit let alone one that could blast off to another planet carrying 10,000 people.

We are a loooonnngggg way from being a spacefaring civilization. Hopefully we can do something to expand our seemingly recreational forays into space. Gotta think about that one!

It is a well thought out plan. I can not find any major problem here. It is just that, it is too hard, like sailing around the world on a dingy. Yet people do it. Never underestimate the human aspirations.

Now, I have seen this somewhere. Ahh! could be Battlestar Gallactica TV series. With the topic scenario, there are two issues I would like to know.

1. Can you educate specific children to take over the duty of the elders? and pass the same understanding of the elders about the planet, solar system and world as a whole to the progeny? The kids and subsequent generation may not have the same reality as the elders will know. How that will affect when they reach a planet? Would they know what it is? What if they hate to get out?

2. Our cars breakdown to a pile of junk in 15 years. Who can design a system that has a MTBF of a 1000 years? Specially moving parts and hot parts?

There are several sci-fi novels that play with this idea of generation ships. One goes like this...

As long as the younger folks are alive that started the voyage, everything is relatively cool. There becomes jealously at who has the prestige, what is envisioned as the cushy jobs, and who has the political influence. And as communications becomes more of a hassle to perform with an ever farther home world, the home world becomes more and more out of touch with their ship board reality. It isn't long after that things start to break down and after some skirmishes within the confines of the ship critical knowledge is lost. (Machining replacement parts, navigation, repair ability, life support maintaining capability) The knowledge is there to be regained if they can access the learning centers but most simply do not care. What they know now will be all they need as their world has continued for several generations and so will likely continue to do so. Just because some nut says they are approaching their destination and need to be prepared to do something to stop the ship isn't necessarily to be paid attention to. The social system set up looks something like tribal system with priests reading from the good book on how they should act/react to each other while several of the tribe are in competition for the leader job. It gives you the impression that space traveling is a forgotten task and that everything is achieved by rote. (Daddy said do it this way).

So how do we avoid something like this? Is this even a conceivable scenario?

There are somethings that just would not work. This could be one of them. So you have to find an alternate plan.

So what social system might be the most stable out of all of humanity's tries at it? What might give the best chance of arriving intact?

Cars are designed with long term stability of the manufacturer in mind. After all, if they built a car that didn't need parts or replacement after 10 years they'd run out of a market. (Built in obsolescence) Obviously this could not be the case in the area of a generation ship. But I would think that even here most components that arrived would not be the original ones if they were used much. Simply to much wear and tear, metal fatigue, and time of use to make it dependable.

If I'm not mistaken, wet1, the Chinese prior to 'democracy' or 'socialism', to wit: An emperor backed up with a bureaucracy based on merit.

The Whipple Shield is a relatively simple shield concept that uses separate shield plates placed in the path of a projectile. The projectile punches a hole through the first plate but then shatters into a fine dust. The dust impacts over a wide area on the second plate inflicting little or no damage whatsoever. The Whipple Shield is a recent development following breakthroughs in hypervelocity projectile accelerators able to shoot projectiles at up to 20 km/sec and patents have been awarded for various improvements on the basic design. The shield was even utilized by a Canadian spacecraft a few years ago. It is expected that the velocity that available systems can test will quadruple within a few years to 40-80 km/sec, and eventually a more advanced version of the Whipple Shield might protect an interstellar Generation Starship at velocities exceeding 1500 km/sec from micrometeorite impacts.

http://hitf.jsc.nasa.gov/hitfpub/shielddev/whippleshield.html

Here are some of the present materials used in the construction of Whipple Shields (taken from the same source)

http://hitf.jsc.nasa.gov/hitfpub/shielddev/materials.html

Elsewhere in these threads the mention of the Whipple Shield has come up. The Whipple shield is now being encorporated into ship and probe designs.

It is an excellent idea. Which means no more "raise the shield or shield is down 80% and up now or switch to backup Mr. Tuvok" ....

Another solution to the genetic diversity problem would be to carry an onboard gene bank.

~Caleb

Very good idea. But since we are not going anywhere, anytime soon, HOLD the thought....

INTERBREADING!

If you have a few thousand people, they may not interbread with all of eachother in three generations, if they don't have a lot of kids. But what happenes in a century in Alpha Centauri. Without naturall diversity, even the best and brigtest will become stupid, and there are a ton of genetic defects that come with interbreading.

You meant to say interbreeding not breading....

Anyway, if we take a large genebank (most of the movies are now favor this) this interbreeding problem can be solved as Caleb pointed out. Thanks

And what are the chances of the gene bank arriving in an unusable form? We doom our pioneers without it. What do we do to ensure that it arrives at the end of such a long journey intact and with no problems? How do we make sure that the knowledge to use it is not lost in the process?

And same thing could happen to your you-know-what. It could shrivel up due to the radiation storms or space microbes or who knows what.....

Don't beat around the bush, just come out and say it! :)

And if we interbread, what kind of wheat shall we use?

This kind of gets me wondering. In another post about early humanoid we are talking limited population. Where did the diversity come from? After all there were not many at the start.

We evolved and bread at the same time, this helped us not interbred with small groups. As for the Starship Generations, if I had the choice, I would decide on something a little less incestuous. Maybe we could store hundreds of baby embryos from different people, implant them in surrogate mothers so that we at least avoid the first and second generation's breading with each other. Just an idea, don't know if it'll work.

The diversity comes from groups moving away from each other and settled for a few generations. That produces gene diversity due to minor mutation.

If Bible is right that we started from only one couple, then there must have been a lot of inbreeding in the beginning until diversity takes over. The first generation may not damage the gene but subsequent will. So there you have it.

Sorry, but I have to add my ideas based on how I see our future development.

You’re all assuming that we retain biological forms. That will not be realistic for long-term space travel. Zero gravity has been shown to cause extensive bone loss even with vigorous daily exercise. And that activity itself requires more energy to be consumed than would be desirable.

Humans have evolved to exist within a very specific gravity and biological environment. Our bodies would degrade significantly outside of such en environment. We must take such an environment with us during travel and then find an equivalent planet at the end of the journey with a similar environment. Artificial gravity outside of sci-fi doesn’t exist yet, and there is no real hope on the horizon. The giant wheels of the 2001 movie (hmm that’s this year) would be impractical for high-speed flight – i.e. acceleration and deceleration would have to be extremely gradual to prevent a break-up. But I guess we might be able to build something. But the real problem will be finding an ideal planetary environment at the end of the journey.

Will the atmospheric conditions be just the same as the earth and will the amount of heat and radiation from a sun be adequate, plus the gravity of course. And would plants and vegetation that we take with us survive in less than ideal conditions. I believe there are a vast number of factors that makes finding an earthlike environment within a few light years near to impossible.

The only real practical solution, if we want to explore our neighborhood say within a 50 light year radius will be to free ourselves from our biological limitations. Making ourselves independent of a specific gravity, or atmosphere, or bio-base foods will enable us to survive on numerous and very different planetary systems.

OK so I suspect that many will not like my next suggestions but I suspect the path we take will be inevitable.

As an aside, genetics and anti-aging research indicate a high probability of very long biological lifetimes in the near future – many hundreds of years, if not indefinite. That would pretty much solve problems of ‘generations’ in long-term space flights.

The issue I have is with the expected rapid development of machines with their own intelligence equal and greater to our own, and most likely within the next 50 years or less. Their continued increase in intelligence will put our own survival at risk such that we would be forced to adopt the same technology just to stay level with these superior beings. That really means discarding our fragile and planetary dependent biological forms.

At that point our only requirement for long-term travel will be a long-term energy source, and that has to be nuclear power. Note that such energy will not be needed to provide heat, bright lighting, or food generation. As Robo Sapiens we would not need such things. So energy consumption should be very low. Note also that in this new form we would be able to tolerate much higher accelerations and decelerations, changes in speed that would probably kill biological lifeforms, and this would make the journey times much shorter.

And where would we go? Probably any planet that looked interesting. No atmosphere would be needed of course, and the gravity variations could be quite large. We would probably want to avoid environments that were highly acidic or corrosive to our metal bodies. But other than that we would have a colossal choice. And if there are many planets, then how about 1 planet per person?

Cris

I believe that in the long haul you are probably right. But it will most likely be a game of catch-up. If your scenario is correct we will have the intelligent machines on our doorstep before we are ready with the technology to convert bio to machine. This will require the help of the more intelligent machines to assist in the discovery of what will work to design such that can house our brains/conscious in some compatible housing that will not give repercussions later.

It could well be that before this is readily that we could be faced with the choice of what to do with intelligent machines. Do we pack them up and send them out when they reach a certain level of awareness to become our explorers? Do we eliminate the competition before it becomes a survival thing that we might not stand the chance of winning? In the contemplating phase do we take the chance of them “finding out” what we plan and risk repercussion?

Overtones of terminator.

Replacing our bodies with robotic forms I don't think will fly, this brings a Pandora's Box of issues if we'd be alive, where the spirit would go and other things. Currently I'm a bit to tired to get in depth, but I think humans are too conservative to do that (If anyone wants to spin a new post off that great).

Humans have adapted to many environments, almost equally alien and harsh as outer space and zero g. Humanity started in what is currently the Sahara desert, which then was a lush jungle. We moved into the drier middle east, through the mountainous central Asia, lived in eastern Asia, flourished in cold ancient Europe and Canada, and even spread our seeds all the way down into South America. If there's one things humans can do is adapt. Adapting to different environments isn't an easy thing, but that's the point. Where's the fun, and virtue in doing something that is easy to do. That would be like staying in the same grade, just because it is easy, and you don't feel like challenging yourself. Even though in the long run you'll be better off moving into a new situation. See where I'm going? Thanks guys.

The gene bank is the answer. However would the genetic material arrive in a usable state?
Firstly a novel idea is the the DNA sequences could be stored DIGITALLY and recreated and implanted in embryos. Perhaps fresh DNA could be encoded and transmitted from earth?
Well a few MILLION sperm and a similar number of eggs would take up a very small volume. There are up to 10 million sperm in 5mls of semen. So we have some idea of how much room it would take to store enogh genetic material.
Then we need only to enshroud this cryogenicly forzen cargo in a few feet of lead or some other sheilding and would have gaurded against almost all radiation.

Then we only need a 'maintenance' crew, perhaps a 100 people, to be alive and to provide wombs upon colonisation.

As I see it the only way to accomplish interstellar travel is to become space-living FIRST. We need to build our O'Neil halo, and have many established and politcally stable space habitat nations.

Humanity would adapt to living in small groups of thousands and even hundreds. Its not like they wouldn't be able to communicate with anyone. After all many human tribes in the past existed perfectly fine as isolated groups of less than 1000, of course they did have contact and genetic mingling with other tribes.
Take your space habitat, attach fusion rockets and nice thick whipple shelid and you have a interstellar spacecraft.

We are planet-lubbers at the momment. "fresh-of-the-planet" humans don't do to well spacefaring. But in 500 perhaps a 1000 years time we would have adapted socially as well as a small ammount genetically to living in space. Perhaps the effects of microgravity will be solved?

Interesting point:
Dolphins would make better space travelers as they would be immune to microgravity and the resulting bone and heart weakening. David Brin used this theme in Uplift series or novels.
Perhaps we should train dolphins to fly our starships?

So, what is an O'Neil halo?

How much salt water would have to be taken to keep a dolphin alive? What would happen if he dies in transit?

Transmitting digital dna? Original, but I don't understand how this would work other than as a pattern. Explain please.

Wet1, curly,

I’ll try not to extend the robosapiens ideas too much further here since we have another forum for that. But there are many who have influence in science, and industry, and I include myself, who are positioning to make this happen. Wet1, once the processing power exists then as a society we will not be able to control it, someone somewhere will write the software that produces super-intelligence – and that makes the human race a second class species on the planet. Curly, whether you believe in a soul or not there are many who do not and they will be the ones that move rapidly to the robosapien phase, including me if I can survive long enough. Among those of us who plan to take this path there is very little concern for those who do not want to change.

Human Adaptation: Humans cannot adapt outside of a very narrow range of temperature, pressure, atmosphere, and radiation. Most of this planet is covered in water, how many humans have adapted to live in an underwater environment? If the ozone layer disappears then that will be the end of exposing bare skin in any form of daylight, and most animals and plant life won’t do very well. And another ice age won’t help much either. How well do you adapt to starvation?

In the past the earth was not very hospitable and life did not exist, at some time in the future, a sizable asteroid will hit the planet, if we are still here then it is unlikely that any will survive. Looking further out the sun will start to shrink and then expand rapidly to engulf the earth and all the planets – we will cease to exist at that point. So yes have fun within the narrow range of conditions that currently exist on earth for as long as you can. As for me I’ll be willing to adapt and augment myself in any way possible so that I can expand my scope for exploration, fun, and appreciation of the other parts of the galaxy.

Moving away from earth towards other planets is inevitable. I am sure there are many now who would jump at the chance to explore deep space, in the same way that Europeans set out for the Americas a few hundred years ago. Many of us are full or curiosity and have a love for exploration. But if we do not augment ourselves quite extensively then the long journeys will be very troublesome and the choices of eventual compatible habitable planets will be extremely limited.

Yes humans may well adapt to hostile locations and uncomfortable journeys, but that doesn’t sound like too much fun. Let’s face the inevitable and enhance ourselves so that we can enjoy almost anywhere we choose to go.

Cris

Cris,

Re. your comment:
Artificial gravity outside of sci-fi doesn’t exist yet, and there is no real hope on the horizon. The giant wheels of the 2001 movie (hmm that’s this year) would be impractical for high-speed flight – i.e. acceleration and deceleration would have to be extremely gradual to prevent a break-up. That giant wheel was an in orbit space terminal, the space ship was dumbell shaped (crew at one end, propulsion at the other) I believe. Maintaining a fractional g acceleration, like about .6 g, would suffice. Naturally with a similar rate of deceleration.

Do agree with the need for a very, very limited range of environmental conditions to survive once we got there but can't buy the 'robohuman' bit.

I don't think that it would pose any great problems to simulate gravity by rotation. If you rotate the craft along the axis parallel to forward motion it shouldn't be a big issue. Infact I would even suggest that it would be benefical to simulate the gravity of the target planet to give the travelers time to adjust during the journey. Actually simulating seasons, day/night periods etc might be of great advantage also.

On a side note: if these ships were true generation ships the decendents of the original crew would probably look VERY different...they'd possibly be slimmer, taller, have larger lungs, pale skin etc all things that would be directly affected by a low gravity low pressure environment (if pressure were to be simulated also...and I'd think if you want to simulate gravity why not gradually introduce pressure) they'd be <drum roll> ALIENS.

Robo-Humans
Personally I think human's would be more inclinded to find a better life-support system rather then abandoning our bio-bodies. I agree with Cris that eventually robo-human's will be a reality, but I think that will be a very gradual process...we'll probably start with nano-type enhancements especially for intellect etc and in time the line between bio and tech will become blurred and people will opt for full robo bodies...but I really think this will be a very long process....


Anyway's just thought I'd throw my 2 cents in.

Hi chagur,

To be comfortable regarding gravity I believe we would need a very large rotating wheel much like the orbiting wheel from 2001. Smaller wheels would need to spin faster and would produce constant dizziness and sickness. Zero G would be more comfortable.

So I guess an interstellar craft would need to be very large.

Having something that constantly accelerated would need a prohibitivly large quantity of fuel and then of course we'd hit problems trying to approach the speed of light. Not sure if that was what you meant though.

As for robomen, yeah well don't worry. I've yet to figure out why some love the idea and others have a big issue with it. And I don't think you have an issue with the soul or no soul bit.

But would you agree that our final destination options are going to be very limited if we are going to insist on planets similar to earth?

Cris

Rambler,

I have a few problems for you.

Regarding gravity: A rotating platform will simulate gravity OK and will feel comfortable providing the users are not aware of the motion, that means a relatively slow moving platform but moving through a large arc. The forward motion of the craft will have no relevance or effect since the passengers will be moving at the same speed, exactly like being a passenger in an ordinary aircraft. The circular motion of the wheel is effectively constantly throwing its passengers outwards giving the effect of a pulling force that can be made to feel like gravity.

Regarding changes through the generations: Here you are talking about evolution and typically substantial structural changes to the body will only take effect after hundreds of generations. For example, all original humans appeared to have had blood type O, it took a further 30,000 years before blood type A evolved.

How many generations: In our generation ship we are only talking of a few generations. If you attempt to alter the environment and force new offspring to live in such conditions you will produce numerous and substantial medical conditions. If the gravity is too low then the first 20 or so generations will suffer from significant calcium loss, weak bones, and frequent bone fractures. Reducing oxygen levels will result in brain damage. The first 50 or so generations will suffer terribly and many will perish due to other medical complications. Only a few will survive and will be able to adapt to the enforced new conditions. The price will be very high. It will take many thousands of years to adapt in such a way.

While I agree that it would be great if robo-humans could be integrated gradually we simply won’t have the opportunity. Our own very rapid development of technology will force us to adapt very quickly. I suspect less than 100 years while I suspect you are thinking in terms of many hundreds.

Cris

Lo Cris,

Okay, let's see ... If the wheel is spinning, regardless of size, wouldn't there be a problem regarding maintaining mass distribution (thinking of a spinning clothes dryer and what happens when the contents aren't distributed evenly) so as not to induce stress?

Regarding fuel: Since we're thinking in terms of hundreds of light years of distance I would imagine the fuel bit would have been solved - like maybe fusion - so that shouldn't be a concern. And without fuel being a concern, upon having attained 1/2c for instance, a routine flip-flop could maintain a 1/2c average while also maintaining a .6g acceleration/deceleration except for the brief transition period.

Robomen I won't even touch - we've been around that maypole before:) And as far as the 'soul' bit: What's that? And, yes, I will insist on planets similar to Earth. How else can we survive without major genetic modification? That's taking for granted that a carbon based organism is what we want to remain. Otherwise, why make the trip?

Chagur

Chagur,

Don't think I have any good reasons to disagree with you.

On the wheel thing: If the wheel is relatively large then the relatively small mass of a few passengers should not cause any significant distortion. The tumble dryer is a problem because of the small radius and the very high spin speed.

Carbon based: You must be fit. I'm only 48 and I'm seeing my fitness and abilities decline. I'd be very happy to trade in my decaying carbon shell for something more resilient, stronger, and longer lasting.

Take care
Cris

Not to knock any atheists out there, but most of humanity believes in a supreme being. In almost every religion, the soul, the spirit is a pillar of that religion. If you create robosapiens, or whatever name they may be called, and "transfer" your likeness onto them before you die, most would interpret this as just a copy. We could program a robot or computer all the knowledge about say JFK or Anne Frank. After the point of their deaths, everything afterwards would be a speculation of how they would act, for they aren't alive any more.

Being alive constitutes the following:

Being a DNA based thing. Reproduction therefore involves making copies of the molecules constituting an organism and ultimately results in copies of the organism itself.

The other major activity of living organisms is metabolism, the physical and chemical processes by which energy from the outside world is used in such activities as reproduction (including growth), locomotion, and responsiveness to the environment

A precise definition of life is difficult, but, in a rough sense, an organism is considered alive if both metabolism and reproduction are active.

Based on a few of these points we can speculate that robots won't by scientific means be considered living. Therefore, you can't be alive inside, that means you're still dead, and your soul isn't transferred. Just a theory.


Works cited: "Life," Microsoft® Encarta® Encyclopedia 2000. © 1993-1999 Microsoft Corporation. All rights reserved.

When you mix up philosophy with technology you get neither philosophy or technology....let us keep them apart.

phi·los·o·phy n. pl., phi·los·o·phies. Abbr. phil., philos. 1. a. Love and pursuit of wisdom by intellectual means and moral self-discipline. b. The investigation of causes and laws underlying reality. c. A system of philosophical inquiry or demonstration. 2. Inquiry into the nature of things based on logical reasoning rather than empirical methods. 3. The critique and analysis of fundamental beliefs as they come to be conceptualized and formulated. 4. The synthesis of all learning. 5. All learning except technical precepts and practical arts. 6. All the disciplines presented in university curriculums of science and the liberal arts, except medicine, law, and theology. 7. The science comprising logic, ethics aesthetics, metaphysics, and epistemology. 8. A system of motivating concepts or principles: the philosophy of a culture. 9. A basic theory; a viewpoint: an original philosophy of advertising. 10. The system of values by which one lives: has an unusual philosophy of life.

tech·nol·o·gy n. pl., tech·nol·o·gies. Abbr. technol. 1. a. The application of science, especially to industrial or commercial objectives. b. The scientific method and material used to achieve a commercial or industrial objective. 2. Anthropology. The body of knowledge available to a civilization that is of use in fashioning implements, practicing manual arts and skills, and extracting or collecting materials.

I think that I shall try a little of the “devil’s advocate” with thecurly1.
While technically accurate as far as it goes I think that it looses some of it’s applied meaning when associated to the subject at hand. To wit:

The soul

There is no yardstick to prove or disprove the existence of the soul. Who is to say that a copy of your intellectual being would not include a copy of this “soul”? We simply do not know at this stage of development. I will not drag religion into the discussion.



Reproduction therefore involves making copies of the molecules constituting an organism and ultimately results in copies of the organism itself.


So after I have lost the ability to procreate I am no longer living? We all age and in that process at some point we lose the ability to procreate at some age. In the time between being young and extremely fertile and that point of the aged is a slow process of losing the ability. Some refer it to as the biologic clock. I think you meant something else.




The other major activity of living organisms is metabolism, the physical and chemical processes by which energy from the outside world is used in such activities as reproduction (including growth), locomotion, and responsiveness to the environment

This is a matter of semantics or definition. The chemical process of the body is biologic. This is not the only process that can be had when viewing the mechanical. Electric potential is within the body for use as nerve transmissions along synapse. While mechanical electrical transmissions may or may not be biological in origin it in no way reduces it’s effectiveness towards producing a walking, able to respond to the surroundings (environment), being. Growth to is a matter of definition. You start out in one physical condition and wind up in another. For biologic it is called growing, for mechanical it is called adapting.



A precise definition of life is difficult, but, in a rough sense, an organism is considered alive if both metabolism and reproduction are active.


Part of this was covered in the first point. To the rest, because of the very vagueness of the definition, it leaves a lot of space that can be covered. This includes the ability to lump mechanical forms in as living. (I’m sure that you didn’t intend it this way but…) After all the mechanical satisfies the reproduction requirement by making instead of growing it’s replacement. It satisfies the ability to respond to its environment. It satisfies the ability to think and come to some independent results based on the facts (otherwise being loaded into a mechanical body is the equivalent of death).

As thecurly1 stated, this is just a theory. (admittedly an opposing one for discourse purposes)

First I would like to say that I cited much of my material from the Microsoft Encarta Encyclopedia, and yes I did look it over.

1) What I and the encyclopedia ment was that the organism and its species in general should naturally be able to procreate/reproduce by sexual or asexual means. Through the exchange of DNA. Because a DNA based entity constitues life.

2) Once again the base definition of a living entity would be a DNA based organism. One that trades DNA to reproduce, and also can metabilize OUTSIDE energy for its personal useage.

Did you know "Devil's Advocate" is my favorite game?

LOL :D :D

OK...

Natural is a matter of accepted viewpoint. When some new species comes along, after studying it and it's method of coping and surviving the accepted viewpoint is taken from what it does. So in this sense a mechanical being would be the same.

As for DNA. Not all life through out the history of the earth has been based upon DNA. Early life forms did with the rudiments of such (if memory serves correctly) but were not precisely DNA. By that definition it is not life. I beg to differ on that point. Further if alien life is ever found, how will that change this definition? I would think that there is no guarantee that any such life would be based on anything we know to be true within our boundaries. (stretching it a little I admit)

Do you not think that mechanical life would not have to convert/make use of outside energy? I doubt that it would be able to carry all the energy it needed to sustain itself throughout its expected lifecycle.

Yes, I recognized the definition as encyclopedic in nature even without the source reference. Had that ring to it.

Curly,

Looks like we need a new thread in the religious debate or general philosophy to cover what is life and what is a soul. It's been covered here in the past, but everyone is pretty new at the moment, so it is worth a revisit.

Curly, you state most people believe in a soul and/or a god, and you imply that makes it true. Consider that a few hundred years ago virtually everyone on the planet believed the world was flat. Truth cannot be determined by a democratic vote, and the majority can be, have been, and are often wrong.

Also supernatural entities are not biological based, they have no DNA since they are immaterial and invisible and do not seem to reproduce, so I think by your definition Gods are dead.

However, I agree with kmguru we should try not to mix the forums, but there is overlap sometimes, let’s try to keep to tech and science here.

On other planets we might find life forms that have evolved from very different structures. For example there is nothing particularly great about human metabolism; asked those closely involved, it is a real mess. I’ll quote you some stories if you like. Some of it’s mechanisms are redundant, some duplicated, and some are counter-productive. Consider obesity and diabetes as simple examples of metabolism malfunction, and these are widespread.

If you visit any of the major aquariums you will see a vast number of very strange looking creatures, many are quite bizarre, but all are based on DNA. Consider a planet with life that is not DNA based or where an equivalent mapping mechanism is very different – then I think the lifeforms would be beyond our imagination.

But back to the starship.
Cris

Cris
Ahhh, indeed what you say is true. We have diverged from the original topic. (Though I had the sneeking suspicion you would be along shortly) :D

I tend to wander and ramble sometimes. Personality trait. After this round of discourse I believe I need to participate a bit more within your realm. To round out the education so to say.

wet1,

Yes I must also learn to stay with the spirit of the topic more. Nuts, did I say spirit? :D

Cris

That sounded like an opening to me! Where's Sir Loone when you need him?? :)

I said that most people believe in a god of some sort, that doesn't make it true or false, I'm saying that billions believe in a higher power. Though the majority may not spell truth they have a lot of power, i.e. I don't think that most thesis people will accept the theory that a robot with an downloaded version of a person will be alive. I didn't say or mean that because people believe in God, or the soul means its true. Though you do know my personal opinion.

Dead means no longer living. In order for something to be dead in that sense would mean it was living in the first place. Gods aren't generally alive, or biotic creatures to begin with. Now, in a physical way after we die, even if there is a spirt, we are technically dead, because our spirt isn't a DNA based biotic entity. This once again means we have to check our intellect at the door, if you believe that a body is just a shell and the spirit is the important part, than by technicality we are all abotic.

What I'm trying to express originally is that robots can't in a scientific sense can't be a living entity because they don't meat the scientific criteria.

As for metabolism we can't say that obesity and diabetes is a defect of our metabolism. The human metabolism hasn't evolved much in the past million or hundred years. In the early twentieth century everyone eat considerably less simple carbohydrates, i.e. starch, sugar. Some may drink a lot of alcohol, smoke, or get to little physical activity. To say that we should all be skinny no matter what, because our metabolism should operate one way is narrow minded. That would expect every woman to be roughly 36-24-36 even if she was bed ridden. Our technology has surpassed our evolutionary mechanisms, our bodies haven't caught up and probably won't.

Can the human metabolism be a imperfect thing? Of course, that's a part of being fat, but a larger part is what we eat versus what we do to the food. All in all the metabolism has worked well enough for humanity not being killed off by natural selection. In that case I'd say its worked pretty well for us.

I'll take the blame for deviated from the Starship thread and creating a religious tangent. Then again let's not limit our thoughts, we have to have an uncensored and uninhibited form of expression. That's the best thing.

Curly,

Yes we are off topic, so I’ll keep this as brief as I can.

Life, as you have described is biological life, scientifically defined or otherwise, it is a qualified view. Gods, spirits, intelligent robots, do not conform to that definition. When we develop autonomous mobile machines that can outthink us then we will need to re-consider how we define life as a more general concept. Most people have not yet seriously considered the potential future of machine intelligence or how to view it, for most it remains science fiction, so their views are irrelevant at the moment.

Metabolism is way-off topic; and you have some serious misconceptions, I’ll help you out there at another time. But obesity and diabetes are life-threatening diseases related to insulin, a key hormone in metabolism. Look also at the scientific studies of the thousands of mummies of ancient Egypt to help you put 20th lifestyles in perspective. But this has little to do with our starship.

Depend less on what the sheep of the world think, that is most people, and decide for yourself, make your own evaluations.

Cris

Back to generations.

If we do develop the means to travel to the stars in search of other planets, and where these journeys may take many generations then there are some other issues to consider –

1. Would it matter that by the time we reached our destination, possibly several hundred years later, people back on Earth had developed much faster propulsion systems and had overtaken us and had already reached where we were headed?

2. If we do genetically engineer ourselves or force ourselves to adapt to an alien environment, then does it matter that later visitors from Earth who had not adapted would see us as incompatible.

3. What if we didn’t try to adapt but couldn’t find any compatible earthlike planets, would we simply drift aimlessly in space forever?

4. And perhaps we don’t need another planet, perhaps we could build a drifting city in space where we visit occasional planets to extract fuel and other mineral resources.

Just some thoughts.

Cris

IMO, I think your point (4) is probably necessary even if the ultimate goal is to find earthlike (or more generaly: compatible) planets. We could call this ship ARK II (LOL, for all the god lovers :) ) and just find new planets and colonise them (if of-course there are no complex life forms already inhabiting the planet). Then we could re-trace the journey back and visit the planets generations upon generations later and see what aliens we've created :D . Actually I tend to think life on earth started that way (well complex life anyway)....

Another 2 cents in the hat :)

Originally posted by Cris
Back to generations.

If we do develop the means to travel to the stars in search of other planets, and where these journeys may take many generations then there are some other issues to consider –

1. Would it matter that by the time we reached our destination, possibly several hundred years later, people back on Earth had developed much faster propulsion systems and had overtaken us and had already reached where we were headed?


Well hopefully the faster travelers, with fancy FTL spaceships would stop to collect the passengers of 'starship generations' and take them to where they were headed. It'd be a bit rude to zoom on past.
How does a great lumbering RV's driver whos yearning for a coffee at the next stop in the desert feel when a Porsche 911 zips by at 120mph?

I think a more likely scenario is that the designs for the new propulsion system would be transmitted to the generation ship where they could upgrade their drive systems on the spot. It would be stupid to send off a ship on a thousand year journey without suficient science and manurfacturing equipment, as well as raw materials.
This of course makes one think perhaps the scientists on board the ship (with nothing better to do other than look at stars) find a way to go faster.



2. If we do genetically engineer ourselves or force ourselves to adapt to an alien environment, then does it matter that later visitors from Earth who had not adapted would see us as incompatible.


Hmmm perhaps a group that has adapted itself to life in a alien enviroment would technically have become another subspecies of human - artificial evolution in a sense. So yes this would bring about big incompatibilities. As if cultural seperation for thousands of years wouldn't cause problems with language and culture etc.




3. What if we didn’t try to adapt but couldn’t find any compatible earthlike planets, would we simply drift aimlessly in space forever?


Well I'll try answer that question with a question. Why do we need planets? As you say below we don't need another planet.

Living at the bottom of a gravity well is expensive in terms of energy getting in and out of the gravity, also it ages our bodies, breaks our bones and is not very safe if your up somewhere high.

Moreover, gravity acts as a very large magnet for meteors & comets which are usually large, unfriendly and intent on making something extinct. The managable extremes of space are actually much safer for a civilisation long term.

In short: gravity sucks. Especially for skateboarders.

Its extremely impractical to build giant rotating starships that must be hauled across impossible distances to find a earth-like planet. If not then terraformable and at worst something that you could put domes or underground habitats on. Instead of seeking out other graivty wells it would make more sense to hollow out asteroids and mine comet for resources.
Then wander about as a race, perhaps seed some planets with life then move on.

I forsee that we will end up with a 'spacefaring' population of mankind, that is geneticly modified for zero g, low g or as mastered large rotating space habitats.
These are the people that will be born and live in space, and may never see the need to visit the bottom of a gravity well.

As we pass planets we may terraform them and seed them with life to start the process of evolution all over again. Or perhaps take other earth species and let the loose in their own world.
The ultimate nature park project?

So its the space dwelling humans that will go anywhere.

This brings to mind Roswell - how could advanced aliens that can obviously cross light years of deep space crash like a TWA jet? Well perhaps they are spacefaring, and seldom bother with big gravity wells, and this lead them to plough into a hillside. Indeed after 100 years of going from a ricketty wright brothers flyer to the Boeing 747 we still have major technical issues with hitting the ground.
The point is this would be the same would be for humans in the far future, planets would be a dangerous and inaccesable place. Only good for "scientific sightseeing" and impractical for mining. Much as space is to us now.



4. And perhaps we don’t need another planet, perhaps we could build a drifting city in space where we visit occasional planets to extract fuel and other mineral resources.


I agree
:-)

Its interesting to imagine what kinds of bizzare technology nanotechnology could bring us for space travel in the far future.

Imagine that starship compents or even the whole thing grows out of a flat smooth surface covered with trillions of nanobots assembling atom by atom, extruding a atom wide cross section at a time, billions of times per second?

All that kind of thing... but a interesting idea

In 2300 AD maybe we'll have space suits made from ultra strong nano-materials - probabliy with a thickness measured in molecules thus giving the wearer full sense of touch, perhaps taste even. It would have all functions built into this "smart skin". Likely powered by sunlight or ambient heat. Would recycle all bodily waste, break CO2 back to oxygen, provide heating or cooling. The material would be strong and tight enough to "squeeze" the body, simulating atmosphere pressure.
We wouldn't need clothes, just a coating of this nano-stuff.

Why send a whole starship, when you could put a human in a bare few-metre wide shielded cockpit atop a big antimatter rocket and have them travel at very high % C?? They would of course be dressed in a nano suit that takes care of all bodily needs, that also provides an amusing VR enviroment to pass the time (So it's bit like being in The Matrix) :-). Then accelerate them to 99.99% C etc. getting to another star system in subjective days. The trip requiring roughly 0.1 to perhaps 10 times one's weight in antimatter (depending on how higher %C you want to travel at and assuming the rest of the vehicle is ultra light and strong nanotech material of negligable mass compared to the occupant).

Cris, I thought you were on vacation. No rest for the weary, eh? Anywho, just wanted to say that there were almost no heart disease cases in 1900, versus millions in 1999. Second of all, I wasn't depending on the "sheep" of the world, or any other livestock that has any Earthly origin. I stick to my guns, look at the SDI thread. Haven't budged one bit, sometimes that's good and at others its bad.

I'm stubborn as a mule.

He haw, I'll be heading off into the digital sunset. For Don Quixote, good night compadres.

I envision a way to slowboat (STL) to nearby stars. You take a really big vessel, like a habitat, insulated from heat-loss, a large reactor inside, as indicated in earlier posts. Inside this structure you can do all sorts of breeding and wheat consumption and whatnot. I'd suggest taking aboard a lot of chicken eggs for the breading and fertilized human eggs to implant in the women onboard to avoid inbreeding.

Then you attack a whole bunch of robot ships. You launch these whenever you detect any tangable mass. The'd deccelerate from .15C to zilch with an astronomical waste of fusion power, and then grab hold of whatever they'd find. Most of it will be cometary stuff. The idea is to mine these comets with robots and pellet the resources gained to the mothership at just about the right speed and small pelletsize for the mothership to pick 'em up; from then on use these these substances as raw material for industrial development and - growth !

It's like living of the land. The slower this habitat moves, the more efficient it is. The faster, the more infrared radiation it'll leak. Halfway during the voyage, when it flies at top speed, it'll be a huge fat blob. In growing it will have swollen like an onion, having expanded, adding onion layers onto itself over and over again. The trick is that on decceleration the vessel will use all this padding as reaction mass for the reversed thrust. By that time there will be a lot of colonists on board (hopefully not slanted-browed inbreds) who, if they behave, will not be used as reaction mass.

A slimmed down mothership will then fly onward to the final destination.

My guess is that this structure would be similar to a large city, with refineries and docks and civil servants and movie studio's and chinese laundries etcetera. And can even be a pretty cool place to go out on a friday night.

The generation ship is unlikely in my opinion; the biosphere needs to be so massive that the fuel and drive systems end up being the size of a small moon.
Nevertheless you might find that a number of examples are built; with a small rate of acceleration, it will take about a thousand years to get to a suitable Sunlike star...
during that thousand years lighter, more compact and faster ships would have arrived and hopefully will be preparing inhabitable areas for the slowboat colonists;

faster and lighter doesn't mean star trek type drives, it just means intelligent use of payload space.
automatic and autononous systems would take up little room, while a small complement of crew could be kept alive using longevity treatment, or with Drexler's concept of Biostasis (http://www.orionsarm.com/eg/b/Bi.html#biostasis) the crew can be suffused with biostatic nanotechnology, and kept alive without freezing for the mere hundreds of years a faster voyage would take.
in many cases, the faster ships will have genetic databanks themselves and will be busy populating these habitats already.
Sometimes the slowboat colonists would find themselves welcome in the developing system when thy finally get there, sometimes not.

The future of interstellar colonisation will be complex and surprising, but I think using some or many different methods we will be able to do it.
the Orion's Arm Timeline (http://www.orionsarm.com/timeline.html)

About that genetic problem..


I believe there is a simple solution to it..

Just pick up 10 people from each "race"
(nordic,hispanic,african, indian and asian)
each one of those 10 persons must have a comproven
genetic difference, and be completely healthy with low genetic
diseases

So we have 50 human especimens each other with completely
compatible (low probabilities of malformations) breed.

From those we have a probability of 50! of different genetic
makeups for their children..

The ship would have the family tree so It would only permit the
crossing of those 25 families possible (with a lot of variation between them)

After about 100 years (4 generations of 25years) the computer
would calculate new families and low probabilities for interbreed anomalies by comparing DNA. Trying to reduce interbreed in the future and keeping the DNA variation high.
So it can be possible with only 50 persons for a period of 100 years, the more years pass the more different genetic families arise and new breeds can be done with no harm.


About the power source..
About 5 Fusion Engines (in 50years fusion energy can be possible eventually) providing unlimited energy for all the trip..

Now for the Propulsion its a little trickier... but capturing hydrogen in the travel and using ion engines we could pull the ship slowly for hundreds of years with an always increasing speed..
I dont see why in a 200 year trip we could not reach about 0,5c or 0,3c with a constant and cheap multiple ion engine pull
(no liquid fuel needed)

About the food...
Beef Vat ! In our days we can almost sintetize the basic meat components and nutrients, the problem is to feed the beef vat..
Of course we would have a kind of above 90% recycle system..
nanotechnology could help us with this..
manipuled plants and fruits could be grown in a Vat too

I believe in about 50years we will be able to pull distant lower than lightspeed travels to other solar systems..
Of course nobody will want to do it because of the money involved but it will be theorically possible..

Over and out..

[QUOTE]Originally posted by eburacum45
[B]The generation ship is unlikely in my opinion; the biosphere needs to be so massive that the fuel and drive systems end up being the size of a small moon.

Actually it would just need enough fuel to take off and get on the right trajectory, then it really wouldnt need fuel and it could just coast to its destination, but you would still need some fuel for landing.

I also heard that nasa may switch to nuclear powered shuttles

I don't hold much hope for massive bussard ramscoop ships either...the interstellar density is very low, and for an enormous generation ship you would need a magnetic scoop thousands of kilometers in diameter to even get 0.01g acceleration; the magnetic field acts as a brake as well, due to friction
http://www.wikipedia.org/wiki/Bussard_ramjet


it would just need enough fuel to take off and get on the right trajectory
That's right, it only needs enough fuel to reach the escape velocity of the solar system, which is about 500 million km per year; the generation ship will take 70,000 years to get to Alpha Centauri.
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