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Post by rmc on Dec 8, 2013 20:18:59 GMT
I once agreed that finding an Exoplanet with Oxygen in its atmosphere would be ideal for selecting a planet that we could one-day colonize. However, the existence of Oxygen in the atmosphere could be alerting us to the fact that life already exists on that world. The existence of microbial life, or any life for that matter, could be problematic for us for a number of reasons. So, after thinking it over again, for the purposes of future-colonization, I felt that finding planets lacking evidence of life would be more useful. The great distances would almost certainly ensure that we could not visit such worlds quickly, or, perhaps, not even allow us to colonize them with people directly. Also, if we are in any danger today from things like nuclear annihilation to any number of other extinction-level events, perhaps we should be thinking of starting this sort of journey sooner than later? In that case, perhaps it would be best to just send out our planet's DNA? It wouldn't ensure human survival, it's true. But, the continuation of what this planet has started may be important. If we are left with little time then, perhaps this sort of plan is all we have. If the DNA/RNA were properly stored, the journey could take as much time as necessary without involving the lives of people. And, since great expanses of time would be involved, selecting a young planet for the purposes of accepting such DNA/RNA may work well, actually. So, if Oxygen in the atmosphere is out, what sorts of things would be necessary for this sort of future-colonization, I wondered? Some of the things that I would agree should be present on such a target-world would be a strong magnetic field, the presence of water and the planet being in the habitable zone. So, if we need to get such a journey started as soon as possible, I began to wonder what sorts of vehicles would best be suited. A fuel-less system of some sort seems best to me. However, for the Solar Sail concept, we are still struggling to come up with the construction-means necessary for making a sail large enough for pulling a reasonably-sized cargo of any sort. And the immense time such a journey could take could leave the sail in tatters; pitted with holes and/or otherwise worn out (such journey, even at 10 percent the speed of light, could take 50,000 years or more) A destroyed sail would be useless for slowing the vessel down once reaching the target system. So, the concept of a hybrid vessel is also available. One that brings along just enough nuclear fuel for either slowing the vessel down, or achieving escape velocity from our solar system. If the sail did the job of accelerating out of our solar system, and then is cut away, the nuclear engines aboard could do the job of slowing down the ship, entering the target solar system. This way the amount of mass that the required nuclear fuel would have could be kept to a minimum. But, again, the sail would need to be enormous in order to carry both a cargo of DNA/RNA and even the least amount of nuclear fuel. So, we are back to finding a means for constructing a Texas-sized sail... Some of the engineering problems involved for such a sail are amassing the huge number of cables necessary for holding the shape of the sail against the right-angle forces involved (a bit like the arrangement found in parachutes) What if some sort of simpler design is found to work too? What if a streamer design could be incorporated instead? This way, instead of massive amounts of cables and a square areas the size of Texas being needed, a simpler system of long strands of material could be constructed, forming a long streamer; reaching some percent the distance between Venus and Earth for instance. Though not as efficient as a sail, if deployed closer to the Sun, perhaps such a streamer arrangement could receive the necessary initial acceleration to make it effective. As to the immense length require for such a streamer, extruding a material in a single direction likely offers fewer challenges than creating a potentially-unwieldy square structure. And, as far as a choice of nuclear motor, perhaps the Fission Fragment Rocket offers the earliest hope of getting on with this project soon Fission-Fragment Rocket. Merits of Hybrid systems |
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Post by Cybermortis on Dec 8, 2013 22:22:04 GMT
Why couldn't you design the sail so it can be furled and unfurled? Solar sails don't have to be thick heavy 'cloth', and in fact it is best if it isn't, so there is no reason you couldn't create a system that doesn't allow this. In fact it would be (relatively) simple since the sail would need to be designed so it can be moved during flight anyway.
Not sure why you think that you'd need a sail 'the size of Texas'. DNA (or much more likely engineered bacteria since DNA on its own will do nothing) doesn't take up that much space. You could fit the DNA of every person on the planet into a coffee mug if you wanted to. And if we are looking at simply seeding genetic material around the galaxy a mugs worth of bacteria time is just fine, after all time is clearly not an issue.
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Post by the light works on Dec 8, 2013 23:26:27 GMT
Why couldn't you design the sail so it can be furled and unfurled? Solar sails don't have to be thick heavy 'cloth', and in fact it is best if it isn't, so there is no reason you couldn't create a system that doesn't allow this. In fact it would be (relatively) simple since the sail would need to be designed so it can be moved during flight anyway. Not sure why you think that you'd need a sail 'the size of Texas'. DNA (or much more likely engineered bacteria since DNA on its own will do nothing) doesn't take up that much space. You could fit the DNA of every person on the planet into a coffee mug if you wanted to. And if we are looking at simply seeding genetic material around the galaxy a mugs worth of bacteria time is just fine, after all time is clearly not an issue. indeed: two sails. one to accelerate, one to decelerate. at this point, it seems the AI required to operate the craft will be the heaviest component. oh, but I would be inclined to question if a virus might be a better vector. can't viruses go dormant longer than bacteria? |
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Post by Cybermortis on Dec 8, 2013 23:45:50 GMT
You only need one sail to accelerate and decelerate.
What makes you think you need an AI to run this mission*? In fact given the length of time the craft would be in space the last control system you'd want to use is an AI. The more complex the control system the more there is to go wrong, so keeping things simple is only logical. Besides, the mission is basically 'fly here and drop cargo' - hardly something you need an AI for.
(*Also note that we don't HAVE AI systems, nor at this point do we have any real idea how to make one or even if it is possible. As such we also have no idea how an AI would respond to being asked to spend its entire life on its own and then dying for the sake of bacteria. I'd guess it would not be overly enthusiastic at the idea.)
A virus requires a host in which to reproduce, and into which it inserts its own (very short) DNA sequence. Therefore while a virus might be able to survive for millennia (bacteria seem to be able to survive this long) it would require a living creature (or at least bacteria) at the other end of the trip. If there was then A; The virus may to totally incompatible with that type of life or its biochemistry or (worst case) B; It infects a sentient species, who decide not unreasonably that this was a biological weapon...hopefully they lack the technology to work out where the agent came from and arrange a counter attack against the species who helpfully just provided them with a large chunk of its genetic code....
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Post by rmc on Dec 8, 2013 23:48:27 GMT
By saying DNA/RNA, I wasn't meaning just bare proteins. Some sort of vector would have to be figured. But, I'm not concerning myself with that part of the problem. A Virus does sound interesting.
If the size of the sail could be kept down, like the one the Japanese recently launched, then two sails may work. However, even after being stored carefully, there is concern that, after 50,000 years, the sail may not deploy properly. (Just as after 50,000 years the fission engine might not fire either). Plus there is considerable mass involved in larger sails (but, as we are now talking about smaller sails, that may not matter) Which deceleration means is more elegant is debatable, but I'd bet nuclear materials weather the trip better than a film of some sort. I could be wrong on that. Maybe nuclear fuels corrode components far easier than the simple, long-term decaying of thin materials.
Besides, if the sail is not in danger of decaying over time, and there is a means for deploying it, why not deploy it, retract it, and then deploy it again? Or, just leave it deployed and then try turning around some way, just before attempting to decelerate? That way just using the one sail. Probably because those means are difficult and the lone sail is in danger of decay.
Anyway, the merits behind such hybrid craft is detailed (or at least eluded to) in the link provided earlier.
EDIT:
Now I see an excellent argument for bacteria by Cybermortis. Which ever is used, I think it offers a better chance than waiting until cryo of people is available. Who knows, maybe this is how "we" got here. Several billion years ago some other civilization shot a virus/bacteria our way ( or, yes, the whole Mars and meteor thing )
Edit II: I also suggested searching for worlds that have no oxygen, a strong magnetic field and are in the habitable zone. IF life turns out to be there already anyway, it's not because we knew it was there.
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Post by the light works on Dec 8, 2013 23:56:11 GMT
You only need one sail to accelerate and decelerate. What makes you think you need an AI to run this mission*? In fact given the length of time the craft would be in space the last control system you'd want to use is an AI. The more complex the control system the more there is to go wrong, so keeping things simple is only logical. Besides, the mission is basically 'fly here and drop cargo' - hardly something you need an AI for. (*Also note that we don't HAVE AI systems, nor at this point do we have any real idea how to make one or even if it is possible. As such we also have no idea how an AI would respond to being asked to spend its entire life on its own and then dying for the sake of bacteria. I'd guess it would not be overly enthusiastic at the idea.) A virus requires a host in which to reproduce, and into which it inserts its own (very short) DNA sequence. Therefore while a virus might be able to survive for millennia (bacteria seem to be able to survive this long) it would require a living creature (or at least bacteria) at the other end of the trip. If there was then A; The virus may to totally incompatible with that type of life or its biochemistry or (worst case) B; It infects a sentient species, who decide not unreasonably that this was a biological weapon...hopefully they lack the technology to work out where the agent came from and arrange a counter attack against the species who helpfully just provided them with a large chunk of its genetic code.... 1: the OP's premise is that the solar sail will not survive the trip; hence his desire for a secondary system. based on that premise, you could not accelerate and decelerate with the same sail. however, a backup sail would allow the first sail to be jettisoned if it did not survive the trip, and the backup to be deployed. 2: the fact that unless you are better at reading a crystal ball than I am, we simply don't have the ability to predict what will happen at the other end of the trip. therefore we cannot simply set a control sequence in motion. we have to have something capable of assessing options and selecting one. I am not suggesting it be a high order AI. just enough to accomplish the mission. 3: do bacteria not require a survivable environment including a source of nourishment? the best option to ensure successful seeding would seem to me to include multiple forms of both. however, you bring up an important point - if there is a sentient species, it may decide that being seeded with either bacteria OR virii constitutes an act of aggression. the other side of the coin is that since the OP is suggesting a 500,000 year elapsed time in transit, and this is to be used as a last ditch effort to prolong terrestrial life; it is kind of a moot point if they come to retaliate. |
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Post by the light works on Dec 8, 2013 23:59:56 GMT
I think one critical word to keep in mind is "redundancy." It's like doing electrical work at the top of a radio tower: if you drop a tool, it's a long walk down to fetch it.
on a different note: setting off a fusion device to announce your arrival in the system is probably also not a good way to win friends and influence people.
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Post by rmc on Dec 9, 2013 1:20:45 GMT
It looks like the discussion is going to slow down, at least for a while. So, I'd like to say thanks for the good points -- especially for the ideas on a DNA vector. It was nice of you to spend time pondering this topic with me. Thanks!!
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Post by the light works on Dec 9, 2013 1:32:18 GMT
always glad to ponder.
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Post by User Unavailable on Dec 9, 2013 15:12:13 GMT
First, one has to ask themselves, "Why bother?"
Why can't we just be satisfied with letting our species die off completely, without contaminating the rest of the nearby galaxy with our DNA?
Then, you have to ask, "If it is so important that our species continue, why not figure out Human Colonization?"
If we are going to make the effort to send DNA willy nilly about the galaxy, we should be willing to risk the monies and human life to colonize with actual living humans.
If you are not willing to do that, why bother at all, because it obvious is not very important to begin with.
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Post by the light works on Dec 9, 2013 15:20:28 GMT
First, one has to ask themselves, "Why bother?" Why can't we just be satisfied with letting our species die off completely, without contaminating the rest of the nearby galaxy with our DNA? Then, you have to ask, "If it is so important that our species continue, why not figure out Human Colonization?" If we are going to make the effort to send DNA willy nilly about the galaxy, we should be willing to risk the monies and human life to colonize with actual living humans. If you are not willing to do that, why bother at all, because it obvious is not very important to begin with. well, yes, that is true. and I was focusing on the technical side of the puzzle rather than the ethical side. |
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Post by rmc on Dec 9, 2013 23:10:27 GMT
It's hard to say how future generations would feel if they knew they were about to be extinct and none of the earlier generations did nothing to keep "an Earth" of some type going when they had the chance.
I'd think if we shot as many of these off as possible (and reasonable) toward such target worlds, we'd be able to say at least our generation did what it could. Naturally, as better means come along to actually send people instead, we'd have the added advantage that many of these target worlds could be in the process of terraforming themselves into more suitable worlds for us purely due to this kind of project.
So, why bother? So that future teams of travelers have better odds of finding suitable worlds. (Not saying that the evolution started on these worlds might not also present some intense challenges too, but likely these would be less problematic challenges than trying to manage totally alien evolution).
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Post by wvengineer on Dec 9, 2013 23:13:42 GMT
Solar sails have a problem with their effectiveness diminishing rapidly the further you get from the home star. The force of solar wind on your sail is subject to the inverse square law. Somewhere out there you will reach a point where the force of the solar wind is so small that you do not get any acceleration from it. Plus once you get out of the solar system, you have to deal with the constant "wind resistance" of interplanetary gasses and the Ort Cloud that will start slowing you down long before you get to your destination. Is is possible that enough gasses along the way could slow you down to the point where you could be dead in space, adrift in the galaxy.
Even worse is the issue of slowing down once you get to your target. You can simply reverse the solar sail to get the opposite effect, but the size and discharge of the star will be a major concern. If the star is small than the sun, then you won't be able to stop. The total delta V you get from the smaller star will be lower than what you get from the home star, you would end up passing the star without slowing enough to get into proper orbit. With a larger star, you can manage your deceleration by managing how much your sail is deployed.
To me it seams like if you are going to the trouble of designing, building and launching a ship with fusion engine, why not use that as your primary propulsion system? KISS principle.
As to taking bacteria with you, the only purpose I could see with that is some form of terraforming project. Release the DNA to overtake and convert the current environment. That would require extensive knowledge of the target planet to know how to engineer your DNA to be able to grow off the native environment.
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Post by Cybermortis on Dec 10, 2013 0:48:57 GMT
DNA doesn't 'grow', it is basically just a chemical storage medium for an organism - one that manages to be both incredibly simple and astonishingly complex at the same time.
Dumping DNA into an ecosystem will do nothing what so ever, dumping organisms into an ecosystem...well the results will depend on how well adapted those organisms would be for the new environment. As our Australian members can attest the results can be devastating to the native creatures even when you know (or think you know) about the ecosystem in question.
In terms of settling other worlds dropping organisms onto them would require that you have information about that world, any life there and that life's biochemistry and genetics far beyond what we have on our own world. If we could get such information then 'dumping DNA' becomes redundant, since the technology needed would make interstellar travel practical. (Although technically colonising a world ourselves would qualify as 'dumping DNA'.) As it is chances are VERY good that any native life is going to be totally incompatible with Earth based DNA - maybe they use different base sequences, or maybe their DNA helix is twisted in the opposite direction or...well you get the idea. If you start changing Earth DNA to match this then you naturally have to ask if what you end up with is really Earth DNA.
The other problem is mutation in the DNA coding. No material we have or are predicted to have is capable of protecting cargo from radiation in deep space. A magnetic field *might* be capable of doing this for all but the strongest sources (the radiation from a supernova would sterilise Earth). But again, we have no technology nor any predicted that would be capable of maintaining such a protective field for 50,000 years...in fact we have no technology that could keep working for that length of time even in space. If we did...well again we don't need to send out ships to 'seed' other planets since we'd have the technology to get there ourselves. Although you could use such technology to terraform planets before you arrive and start to build a colony - in fact this was an idea touted for terraforming Venus and Mars back in the 1970's.
In essence you are trying to argue about the design of a car before anyone has invented the internal combustion engine or discovered gasoline.
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Post by rmc on Dec 10, 2013 1:17:08 GMT
WV - I think "they" are getting excited about the idea behind the hybrid sail/engine partially because those things supposedly get up to acceleration (somewhat near the home star) then jettison the sail so that it doesn't decay, cause drag and whatnot -- and then, by having a FISSION-fragment rocket, the craft can decelerate as needed (maybe accelerate too a bit, if needed?) This way, with the fission system, we are using nearly-current tech, enabling us to embark sooner, Instead of working a bit longer for a doable FUSION system -- and by incorporating fuel-less systems where possible, the amount of mass is reduced by around half. I think the premise behind this thread is basically there is some realization that we (the world) must to do something out desperation. And, let's face it - desperation is messy. Doing nothing is also an option too, as previously stated. We seem to be pressing right along on that course of inaction as is!  |
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Post by User Unavailable on Dec 10, 2013 5:25:06 GMT
My point earlier was rather elusive, I suspect. If you are nearing extinction and sending out DNA in hopes of "colonizing" and keeping the human species alive somewhere, then that is solely out of vanity or fear our race will be forgotten. This reason is selfish and unscientific and it doesn't matter if our species does manage to take root somewhere, because "we" will have long been forgotten. So what have we achieved other than contaminating another ecosystem, purely out of vanity? So, it only makes sense to actually send people out in an effort to colonize, thus insuring that "we" are not forgotten. (Though still having contaminated another ecosystem) This would also help insure that future generations of explorers/colonists, should there be any, would have a much easier time of it as they would be somewhat expected, whereas if a human "colony" had to go through millions of years of evolving from DNA laced bacteria or viruses, wouldn't be expecting us and would view us with suspicion and fear, just as we would view another race of humans or human like space travelers who showed up and said, "Hey, you don't know us, but we seeded this planet you call Earth with the building blocks of our species and now we are here to check up on (or move in with) our children!" There would be total chaos if that happened to us. Various religions would go to arms against those claiming to be God or the Creator. Many would go to arms just because they are different or are seen as invaders. Sure, some would be accepting, but the majority would never seen the new comers as anything but a threat. Worse still would be if "our parents" , now being millions of year further evolved than us and far more technically advanced, simply destroyed us as an experiment that failed, or viewed us as easily conquer able to take over this new home..... Which are options we would entertain as well, if we were the ones visiting our "children" on another planet. Of course we could just observe them and see how they are doing, which some say Aliens are doing to us now.... Here is an interesting link on Generation Ships and there are many links to and links to other links that makes the concept of actual human colonization very interesting. In my view, if it is worth colonizing, it is worth sending people with an actual chance of it happening, rather than relying on seeding our DNA around and hoping it "takes", somewhere. Actually, there are efforts to get "out there". Mars being the first and obvious choice as a stepping stone to the rest of the galaxy. |
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Post by the light works on Dec 10, 2013 5:31:31 GMT
I think his idea was that you send the genetic material out in the hope that it will evolve to the point of being a habitable wilderness by the time humans get there.
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Post by User Unavailable on Dec 10, 2013 5:47:09 GMT
I think his idea was that you send the genetic material out in the hope that it will evolve to the point of being a habitable wilderness by the time humans get there. Same deal. That's little more than wishful thinking. If you are going to contaminate a planet anyway, JUST DO IT and find one you already suspect or have confirmed can support life, instead of waiting around for millions of years and hoping evolution hooks you up. Heck, by the time you wait for for evolution, if you are still around and capable of traveling to the distant stars, it is likely you will be so technically and medically advanced that you won't have to worry about contamination or looking for habitable planets for that matter. In millions of years, you should be able to jaunt out to a inhospitable chunk of rock, on a 3 day weekend and utilize the Instant Terraforming Picnic Kit, you bought at Walmart in the camping section and spend quality time with your wife and kids,  |
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Post by the light works on Dec 10, 2013 6:28:47 GMT
I think his idea was that you send the genetic material out in the hope that it will evolve to the point of being a habitable wilderness by the time humans get there. Same deal. That's little more than wishful thinking. If you are going to contaminate a planet anyway, JUST DO IT and find one you already suspect or have confirmed can support life, instead of waiting around for millions of years and hoping evolution hooks you up. Heck, by the time you wait for for evolution, if you are still around and capable of traveling to the distant stars, it is likely you will be so technically and medically advanced that you won't have to worry about contamination or looking for habitable planets for that matter. In millions of years, you should be able to jaunt out to a inhospitable chunk of rock, on a 3 day weekend and utilize the Instant Terraforming Picnic Kit, you bought at Walmart in the camping section and spend quality time with your wife and kids, well, that's kind of why I've been ignoring the ethical side of the question. |
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Post by rmc on Dec 10, 2013 14:00:58 GMT
I wouldn't depend on the idea of life on the other world one-day becoming humans using this last-gasp colonization technique.
Anyway, the real irony here is that if the "world" had decided to embark on a one-way mission like this to send our planets "collective" DNA to another world, using a vessel that would get out to somewhere usable in around 50,000 years AND if the world then, soon after, went dark, there is still the chance that the so-called extinction level event merely turns out to be nothing more than something on the order of an ice-age, for instance, merely bottlenecking the population down to just one or two tribes, that somehow manages to survive. Then, after just the next 15,000 years, those survivors could have recreated civilization (like after our last ice-age), then rise up into a space age, solve space flight issues, make a craft fast enough to catch up and then pass the solar sail hybrid vessel still on its way (likely still having another 25,000 years to go) then those travelers land on the planet and end up dealing with the planet being too crude for their purposes and then start directly terraforming,
But, as I said. A desperate mission has the potential of being messy.
PS - the term "collective" DNA merely means that since most creatures here on Earth share a similar DNA code, whatever code gets sent, in effect, represents the planet, mostly on the whole. (not a big group of different DNA, unless that works)
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