The Limitations of Intergalactic Travel

[shashankac655]

Remember we are going to need a comprehensive understanding of ecology far beyond that of today so that we can terraform (either partially or wholly) these planets to make them suitable. We can't live on worlds that have already evolved life (because the ecosystems would not mesh and we may have superantigenic problems) and lifeless worlds cannot support us.
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I agree

Of course it begs the question as to why you need a planet at all. To build an interstellar colony ship you need fantastic knowledge of…..
This confuses the issue because if you've got all of this there is no need to wander into space and colonise other planets at all. An interstellar colony ship is less of a vehicle and more of an island in space. Rather than fly off for millennia you might as well build these colossal ships and put them in orbit around the Sun. Ignoring what specific elements you need if we posit an O'Neill style colony ship 100km long, 20km wide, 1km thick with a mass of ~6e15kg then with the mass of an object such as Ceres (9e20kg) you could make 150,000 ships with a total of 9e8km2 of living space, 6x more than the land surface of Earth.
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I agree with all the points you have stated
Actually I was thinking about the possibility of humans outliving the Sun ,this might be ridiculously far away in the future and may even be impossible that’s why I talked about the need to travel to other solar systems.( i may be wrong)
I fully understand why we don’t have to abandon our solar system just because Earth becomes inhabitable and so your suggestion is better than what I thought of but I am not sure how we are going to create gravity in spaceship ,I have read about rotating spaceship inside which the centrifugal force can act like gravity and there are other ways like rotating electromagnets and stuff like that but can it really create gravity to the same magnitude as we experience on earth? How fast should the spaceship rotate ?
Is it easy to maintain the speed of rotation?

I'm confused as to why you think artificial intelligence would help? Sure more intelligent software would help with everything but why do you think it is necessary?

Considering such large interstellar ships we will be facing huge problems in maintenance, in such a large ship minute damages can prove to be disastrous.
Such a large ship will be constantly bombarded by tiny space rocks or asteroids traveling at very high speeds but may be the ship’s outer layers will be designed to withstand these collisions but it can’t withstand that forever(after repeated collisions on the same part) and solar winds or flares may overtime cause some kind of damages and even inside the ship somethings may go a little wrong and we may need a super computer to detect minute unintended changes in the ship. keeping an eye on every single miniscule corners of a ship (inside and outside)will be very difficult ,even if we have advanced surveillance systems (like we use in monitoring modern day traffic and security systems etc.) we will still have to depend on the ‘human element’ which may not be safe enough for example: in the Columbia disaster the hole in the shuttle was clearly seen by some people yet the crew were not informed about it and the consequence was fatal ,this kind of human error is something we cannot afford in our interstellar ship.
I don’t know of the possibility of this kind of AI but here it goes:-
We will need some kind of a super software which will make the ship behave like a huge artificial organism (not really an organism but only to a certain extent) which can detect and repair (or at least inform the inhabitants) when somethings go wrong in any corner of the ship or any point on the ship (inside and outside) this will considerably reduce the burden on the ship’s inhabitants and will improve safety.
Surely we can’t think of the interstellar ship to be just a hard and inpenetrable shell, inside which we can have an ecosystem can we? It has to be a lot more complicated than that.

Firstly the technologies you need to do it are orders of magnitude harder than those needed to keep Earth perfect (i.e. long before you have terraforming technology you have the ability to keep the worlds ecosystem perfect, long before you have propulsion technology you can deflect any asteroids, long before you have the ability to construct the societal models needed for generation ships you have a model for harmonious living on Earth).

The only time I see mankind achieving any of this is when the technologies are developed as a by-product of other scientific research and when the Earth is so much more prosperous than it is today that people are willing to commit resources to this endeavour.

I don’t disagree with any of these but the colliding asteroid problem was not what made me to think about why some day space travel or space colonization will become a necessity for humanity.
Harmonious living on Earth is possible and appears to be a better thing to do instead of dreaming of space colonization right now, I agree.

I also agree with 2nd paragraph, there are so many things to be done on Earth before humans can afford to live in space ,wealth distribution should become uniform and sufficient throughout the world ,scientific temperament and rationality has to cultivated among the masses especially in the developing world where religious superstitions, blind beliefs and discrimination on the basis of caste ,color or gender still dictates the lifes of millions of people.
The developed world should not only find more powerful energy sources (or renewable sources)but also try to put a limit on their consumption of energy and natural resources, for example if the countries in the developing world (with their huge populations)start to consume energy and natural resources in the way countries like the USA is doing right now we will need several Earth's to sustain humanity and human population has to greatly come down too.

 

[Ryan_m_b]

If the spin of the ship is big enough it will be barely detectable. I can't find a good calculator at the moment (feel free to google centrifugal calculator and find out how fast things have to spin for yourself) but there has been lots of speculative work done on the subject. The most famous of which comes to mind is Island Three.

EDIT: Here's a few more useful links
http://en.wikipedia.org/wiki/Artificial_gravity
http://en.wikipedia.org/wiki/Rotating_wheel_space_station
http://regentsprep.org/regents/physics/phys06/bartgrav/default.htm

 

[Chronos]

Blue shift would definitely be a problem traveling at .999 c. Not to mention random space debris. At that speed even a speck of dust would hit like a mountain.

 

[tkav1980]

I absolutely love these kind of topics. Being a huge Sci-fi nerd it's right up my alley.

I do have a question for all of the more knowledgeable people on this board. IF you were going to design a propulsion system for a future interstellar spacecraft how would you do it? Would you start with known technology or try to develop new technology? Is the idea of a "Warp Drive" purely science fiction and the Alcubierre metric no more than an exercise in mathmatics, or a viable basis for where to start from? Finally, What would your estimated timescale be for the development of efficient technology to travel to other solar systems be?

 

[Cosmo Novice]

I absolutely love these kind of topics. Being a huge Sci-fi nerd it's right up my alley.

I do have a question for all of the more knowledgeable people on this board. IF you were going to design a propulsion system for a future interstellar spacecraft how would you do it? Would you start with known technology or try to develop new technology? Is the idea of a "Warp Drive" purely science fiction and the Alcubierre metric no more than an exercise in mathmatics, or a viable basis for where to start from? Finally, What would your estimated timescale be for the development of efficient technology to travel to other solar systems be?

You should re-read this thread and pay specific atttention to the earlier posts on propulsion - namely that "warp" drive is purely speculative. Realistic propulsion methods are discussed in this thread.

 

[Ryan_m_b]

I absolutely love these kind of topics. Being a huge Sci-fi nerd it's right up my alley.

I do have a question for all of the more knowledgeable people on this board. IF you were going to design a propulsion system for a future interstellar spacecraft how would you do it? Would you start with known technology or try to develop new technology? Is the idea of a "Warp Drive" purely science fiction and the Alcubierre metric no more than an exercise in mathmatics, or a viable basis for where to start from? Finally, What would your estimated timescale be for the development of efficient technology to travel to other solar systems be?

I refer you to post 80, propulsion is the least of your issues. On this subject I strongly agree with SF author http://www.antipope.org/charlie/blog-static/2009/11/the_myth_of_the_starship.html" that the term "space ship" confuses the whole issue because it conjurs up the notion of a dedicated crew traveling between hospitable environments. In reality any kind of manned interstellar travel is going to be analogous to rolling up a small country inside a cylinder and giving it a slight shove in one direction. This is going to require some particuarly huge leaps in science, technology and especially social sciences because you have to;

• Build and maintain a viable ecosystem
• Design an ultra-versitile and ultra-diverse industrial complex capable of recycling and manufacturing almost anything
• Construct a socioeconomic and political system capable of maintaining a stable society over extremely long time periods with no failure

Technologies such as warp drives are almost totally speculative as they require negative mass and other such possibly non-existant unobtainium. Other technologies such as AI and Von Neumann probes may be possible but are essentially magic right now and can't meaningfully be discussed in this context.

 

[snackbardan]

Remember we are going to need a comprehensive understanding of ecology far beyond that of today so that we can terraform (either partially or wholly) these planets to make them suitable. We can't live on worlds that have already evolved life (because the ecosystems would not mesh and we may have superantigenic problems) and lifeless worlds cannot support us.
Of course it begs the question as to why you need a planet at all. To build an interstellar colony ship you need fantastic knowledge of:

• Ecogenesis to maintain both a stable ecology on the ship and build one when you get to where you are going.
• Manufacturing because your ship needs to build a new civilisation so it needs on it factories capable of building everything. No small feat as on Earth I suspect such factories would be gargantuan (in addition everything has to be 100% recyclable because the ship is a closed system.
• Cogsci knowledge so that issues of social/economical management can be so sophisticated that you are able to build long lived institutions (for a colony mission you're looking at a time scale measured in centuries-millennia and human institutions don't have a good track record of reliably embarking on projects that last longer than themselves)
• Propulsion technologies to get there in a reasonable time i.e. centuries-millennia

This confuses the issue because if you've got all of this there is no need to wander into space and colonise other planets at all. An interstellar colony ship is less of a vehicle and more of an island in space. Rather than fly off for millennia you might as well build these colossal ships and put them in orbit around the Sun. Ignoring what specific elements you need if we posit an O'Neill style colony ship 100km long, 20km wide, 1km thick with a mass of ~6e15kg then with the mass of an object such as Ceres (9e20kg) you could make 150,000 ships with a total of 9e8km2 of living space, 6x more than the land surface of Earth. I would argue the need for the three things listed above is more important than propulsion but I agree it is still important. Note that there are still huge complications with propulsion; even if we posit the creation of something as hypothetically good as an antimatter rocket (1,000,000isp, the best currently speculated with reasonable thrust) you still need an outrageous amount of energy to get anywhere. To boost one of our colony ships described above to .01c would require ~1.8e15kg of fuel (itself a 1:1 mix of matter and antimatter). Double that to slow down at the other end. That amount of Am/M fuel is equivalent to 3.2e32j of energy or 7.2e16 Tsa bomba's (I'd hate to be the enemy of that ship).

I'm confused as to why you think artificial intelligence would help? Sure more intelligent software would help with everything but why do you think it is necessary?If you read through the rest of the thread you will see that the "we will survive" idea doesn't really hold for space travel on this magnitude. Firstly the technologies you need to do it are orders of magnitude harder than those needed to keep Earth perfect (i.e. long before you have terraforming technology you have the ability to keep the worlds ecosystem perfect, long before you have propulsion technology you can deflect any asteroids, long before you have the ability to construct the societal models needed for generation ships you have a model for harmonious living on Earth).

The only time I see mankind achieving any of this is when the technologies are developed as a by-product of other scientific research and when the Earth is so much more prosperous than it is today that people are willing to commit resources to this endeavour.

We would first have to find a way to build that in space without it being affected by gravitational energy and such. We would also most likely need to colonize a planet before creating these ships because we would have to find a way to actually keep these in space without holding the risk of 150000 massive ships crashing into our home planet. The thing we should look for is a new propulsion source rather than building ships like "The Empire" in Star Wars. The near future should be full of rockets that can travel to near planets in a few weeks to months rather than trying to jump immediately to c speeds in space travel

 

[Constantin]

I previously posted a reply that was deemed over-speculative and deleted.
So I'll rephrase it, leaving some details aside:

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There's no limitation that says an intergalactic ship has to be large.
It can be a very small fully automated ship. And by very small I mean it can even be tiny. Artificial intelligence is enough, we don't need to bring humans, factories or any other stuff with us.

That circumvents any problems related to huge amounts of fuel needed as well as those that say the trip should be made in a lifetime.
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The original poster was talking about "limitation of human space travel".
That probably meant he intended such a ship to transport humans.

However there's no requirement that fully developed humans have to be transported.
Genetic codes and the information on how to develop life is all that's necessary.
---

So the problems discussed in this thread steam from the likely unfounded hypothesis that such a ship would need to transport a lot of stuff and thus be large.
I'm not saying such a ship can't be large, just that it doesn't have to be, and it might not be practical to be large.

 

[Cosmo Novice]

I previously posted a reply that was deemed over-speculative and deleted.
So I'll rephrase it, leaving some details aside:

---
There's no limitation that says an intergalactic ship has to be large.
It can be a very small fully automated ship. And by very small I mean it can even be tiny. Artificial intelligence is enough, we don't need to bring humans, factories or any other stuff with us.

That circumvents any problems related to huge amounts of fuel needed as well as those that say the trip should be made in a lifetime.
---

The original poster was talking about "limitation of human space travel".
That probably meant he intended such a ship to transport humans.

However there's no requirement that fully developed humans have to be transported.
Genetic codes and the information on how to develop life is all that's necessary.
---

So the problems discussed in this thread steam from the likely unfounded hypothesis that such a ship would need to transport a lot of stuff and thus be large.
I'm not saying such a ship can't be large, just that it doesn't have to be, and it might not be practical to be large.

A small ship will still need sufficient fuel - proportional to the mass of the ship. A small ship will still need adequate sheilding, adequate storage and adequete computational power - assuming light year distances it would need to be of sufficint sophistication to make decisions. The relevant AI systems are nowhere near that level of autonomy at the moment.

The information on how to develop life may be difficult - and where would this go?

If we are still talking intergalactic then bigger would be better - redundancy is a key concept especially when talking about intergalactic travel.

 

[Constantin]

A small ship will still need sufficient fuel - proportional to the mass of the ship. A small ship will still need adequate sheilding, adequate storage and adequete computational power - assuming light year distances it would need to be of sufficint sophistication to make decisions. The relevant AI systems are nowhere near that level of autonomy at the moment.

The information on how to develop life may be difficult - and where would this go?

If we are still talking intergalactic then bigger would be better - redundancy is a key concept especially when talking about intergalactic travel.

I'll take your arguments one at a time:

1: The amount of fuel will be "proportional to the mass of the ship", exactly as in your post, so rather small. Furthermore it is also proportional with the max speed of the ship, and we no longer have the requirement of a trip made within a human lifetime.

2: "adequate sheilding, adequate storage and adequete computational power"
The strength of shielding would be proportional with the leading surface of the ship and with the speed. The smaller this surface and speed, the smaller the shield needed.
As about "adequate storage and adequete computational power", even with our current technology level we're making very small computers and we have a tendency to miniaturize all the technological parts as our technology progresses.

3: "The relevant AI systems are nowhere near that level of autonomy at the moment."
That part is obvious. This thread doesn't refer to the present moment. But we are making very fast progress.

4: "The information on how to develop life may be difficult - and where would this go?"
It isn't difficult. Even with our limited technology level we can clone and genetically alter life forms.
This will easiliy improve.
I won't go into details of how I imagine it to be done, as that would be over-speculative and would likely get me a warning from the moderators. But feel free to use your own imagination.

5: "If we are still talking intergalactic then bigger would be better - redundancy is a key concept especially when talking about intergalactic travel."
Redundancy is very much different than big size. Redundant actually would mean a very large number of small ships.
What would provide better redundancy? One ship weighing 1000 tons or 1 billion ships weighing 1 gram ? This part is obvious.

 

[Ryan_m_b]

The obvious problem with a small ship is how you plan to actually do anything with it without megatonnes of factory tools, even if we did wave a magic wand and grant you practical artificial intelligence that doesn't have any ethical issues.

Also note that a genome is not enough, you're also going to need the epigenetics of a fertilised ovum as well as the complement of metabolites, proteins, sugars, etc as well as a way of actually gestating the organism. Lastly you're going to need a sophisticated way of raising organisms with healthy psychology and social interaction and a way of doing that billions of times as a part of or after creating a habitable environment.

 

[Constantin]

The obvious problem with a small ship is how you plan to actually do anything with it without megatonnes of factory tools, even if we did wave a magic wand and grant you practical artificial intelligence that doesn't have any ethical issues.

Also note that a genome is not enough, you're also going to need the epigenetics of a fertilised ovum as well as the complement of metabolites, proteins, sugars, etc as well as a way of actually gestating the organism. Lastly you're going to need a sophisticated way of raising organisms with healthy psychology and social interaction and a way of doing that billions of times as a part of or after creating a habitable environment.

Any tools, factories or life forms don't need to be transported physically. It is far easier to transport them as information on how to build them. The entire knowledge of a civilization, or just the necessary parts of it, can easily be transported.
There's absolutely no way an advanced civilization would transport bulky factories, and spend almost infinite amounts of energy in doing so, while building those at the destination is so much cheaper in every way.

The questions arises of course how can a small ship build big things.
If that small ship however has sufficient artificial intelligence to overcome any obstacles, it is doable.

I'll give a very simple way of imagining this. Imagine a simple ant, or a bee, a small insect, working tirelessly building something. That small insect will build structures far larger than itself.
And if that small insect has the ability to replicate, or if more of them are available in the first place, you can imagine your problem solved.

 

[Ryan_m_b]

Any tools, factories or life forms don't need to be transported physically. It is far easier to transport them as information on how to build them. The entire knowledge of a civilization, or just the necessary parts of it, can easily be transported.
There's absolutely no way an advanced civilization would transport bulky factories, and spend almost infinite amounts of energy in doing so, while building those at the destination is so much cheaper in every way.

The questions arises of course how can a small ship build big things.
If that small ship however has sufficient artificial intelligence to overcome any obstacles, it is doable.

I'll give a very simple way of imagining this. Imagine a simple ant, or a bee, a small insect, working tirelessly building something. That small insect will build structures far larger than itself.
And if that small insect has the ability to replicate, or if more of them are available in the first place, you can imagine your problem solved.

And how is that one ant going to use the bigger tools it is building, or apply the necessary force on objects when necessary, or build things like forges, smelters, chemical factories etc. If it takes a million man hours to get a job done that doesn't mean that one man will do it in a million hours, for many jobs the productivity of a group scales more than linearly when you add more workers.

This topic is going far too speculative. Let's try to bring it back or the thread will be locked.

 

[Constantin]

And how is that one ant going to use the bigger tools it is building, or apply the necessary force on objects when necessary, or build things like forges, smelters, chemical factories etc. If it takes a million man hours to get a job done that doesn't mean that one man will do it in a million hours, for many jobs the productivity of a group scales more than linearly when you add more workers.

This topic is going far too speculative. Let's try to bring it back or the thread will be locked.

As I posted previously:
"And if that small insect has the ability to replicate, or if more of them are available in the first place, you can imagine your problem solved."

If we get into details, it can only get speculative.

Back on track: there's absolutely no reason the ship needs to be large. Being small is much more practical, being cheaper and having redundancy by being able to send large numbers of ships.

But there's the added and not necessarily related fact that the ship can be fully automated and doesn't need humans inside.
And this by itself partially solves the fuel problem, as the trip can take far longer and thus be cheaper.

 

[Ryan_m_b]

As I posted previously:
"And if that small insect has the ability to replicate, or if more of them are available in the first place, you can imagine your problem solved."

If we get into details, it can only get speculative.

Yes if we had a fully autonomous and self replicating, intelligent workforce that can grow from a small seed and give rise to a society we could use a smaller ship. And yes, that is overly-speculative.