Why thinking about migrating to other planets?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Saint, Oct 16, 2017.

  1. Seattle Valued Senior Member

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    The conclusion of that article raises some of the problem. I don't begin to claim to be able to have any expert knowledge as to the physics. I have trouble with 1000 km lenses but that's just me.

    "Conclusion Laser-pushed lightsail systems provide a method for traveling to the stars that use known laws of physics and fairly reasonable engineering extrapolations of known technologies in thin films and laser power generation and transmission. They have a highly significant advantage over a standard rocket system in that the vehicle does not have to carry any reaction mass or energy source. In addition, the parts of the "engine" under the most stress and need of maintenance, the laser power generators, remain in the solar system where they can be repaired, replaced, and upgraded as the mission proceeds. Laser lightsail systems are wasteful of power, since the high "exhaust velocity" of the reflected photon "reaction mass" is poorly matched to the spacecraft velocity, except at nearrelativistic speeds. They also require the construction of very large but lightweight structures, since the optics must be of the order of 1000 km in diameter to enable us to carry out rendezvous and return missions from the nearest stars. The pointing and tracking requirements look formidable, especially considering the years-long time delays in the control loops, but with the use of a pilot beam they should be solvable. Making the ring-shaped lightsail act as a focusing lens in order to achieve the rendezvous and return missions is also a major unstudied problem. The present sail designs are not known for their optical quality, and to get focusing will require sensing and shape control systems or reflective holographic or Fresnel lens construction that will add weight. It may be that other techniques will be developed for interstellar travel that will require less power and mass, and be faster and less risky than subjecting an ultrathin spacecraft to 600°K for years at a time. But it is good to knOw that there exists at least one method, laser-pushed lightsails, that can take humans to the nearest stars and back in a reasonable time."

    I don't see this actually occurring. Do you?

    I did a quick search and I'll post this.

    https://arxiv.org/ftp/arxiv/papers/1308/1308.4869.pdf
     
    Last edited: Oct 29, 2017
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  3. Hipparchia Registered Senior Member

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    Exactly so. You are using personal incredulity in preference to the views of a physics expert with extensive experience in engineering space systems. For practical purposes we can disregard your views since they are, by your own declaration here, unsupported.

    Almost certainly not. This proposal is more than thirty years old. Technology advances. Ideas build upon ideas. The Apollo program only incorporated some of Tsilokovsky's ideas. When we eventually set out on an interstellar voyage it will take advantage of newer technologies and newer ideas.

    In the meantime, here is an update on how we might go about the first missions of robotic exploration. Note that this could take place this century.

    And here is a paper detailing how an interstellar robotic craft could reach a nearby system in 25,000 years using current technology.
     
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  5. Seattle Valued Senior Member

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    By all means, disregard my views. No need for any more discussion.

    25,000 years? By all means lets get started.
     
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  7. Hipparchia Registered Senior Member

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    You are offering opinions. I am offering analyses and reasoned projections. You respond with more opinions. That's not the grounds for a discussion. Do you intend to offer something more substantial than your own incredulity?

    Do you feel sarcasm and higly selective quoting is a serious response to a serious post? Did you even bother to read any of the papers? Did you fail to understand the point of presenting a proposal for a robotic probe that would take 25,000 years to reach its destination? Or were you simply repeating your own disbelief without justification?

    It seems to be the latter, so you are correct, there is no need for you to take part in further discusison.
     
  8. DaveC426913 Valued Senior Member

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    6,987
    I don't think you've actually spelled those out until now.

    Distance is not a hard stop, as witnessed by the fact that the next mile on the journey is only incrementally harder than the last - all the way up to the destination. There is no barrier in terms of distance; it's merely cumulative.

    Speed of light is not a hard stop on the journey - it is simply a rate limit.

    And frankly, it's only a rate limit in the case of anyone unrealistically hoping to make a return trip. Speed of light itself does not limit the ability of a single generation of crew reaching any destination. Hypothetically accelerating all the way to midpoint turnaround would reduce trip duration to mere decades. It's actually fuel that limits that, since we can't pack enough to accelerate all the way.

    Speed of travel in-and-of-itself is not relevant except inasmuch as the journey takes a along time - that's the one really tough factor - the one you should have mentioned. And yup, it's a doozie. Keeping people alive and fertile, all the supplies, and most notably the fuel. All a great amount of effort, to be sure.

    We can't predict what technology awaits us in the future, but any engineer will agree that we can certainly say with confidence that materials will continue to get both stronger and lighter, and propulsion systems will get more efficient, requiring ever less mass.

    And we won't necessarily have to take all our supplies with us. Resources - by far the largest being fuel - may be harvested along the way. But that part is still science fiction.

    As one solution, there is nothing physically impossible in our understanding of physics and engineering about generation ships. They're a huge undertaking and (note this especially) they require a lot of knowledge and technology we don't yet have (which is the point in learning stuff even before we are ready to start any kind of construction), but we don't need any new physics breakthroughs (such as magical warp drives) for the journey, just a heck of a lot of materials engineering.


    It's as if you're waving your hands in the air and sort of saying "All the details are just way too complicated. I can't be bothered thinking each individual component through, so I'm just going to lump it all under pretty much impossible, and certainly impractical, and be done with it."

    I don't really think it's beyond you, I just think you're being sort of lazy - you're only half-heartedly engaging here.


    To be clear, I'm not suggesting we should be building spaceships so's I can book my ticket. It will be a century or two before we can make such a trip in any way other than exploratory. I'm simply saying your categorical dismissal is overstated.
     
  9. DaveC426913 Valued Senior Member

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    6,987
    It's not your views, it's your categorical conclusion.
    "This is really really complicated. Therefore, lets not."
     
  10. Seattle Valued Senior Member

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    I'm just saying it's more difficult than many who are enamored with this premise may realize and the premise is a little faulty in the eyes of some (and not others of course).

    It's a solution in search of a problem. Sure it's possible and it's possible it may be needed or effective. It's not likely IMO.
     
  11. DaveC426913 Valued Senior Member

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    6,987
    Agree 100% on both counts.

    Fortunately, we don't yet have whole corporations devoted to such a project (unless they're privately funded).
    Orgs do have special projects, designed to explore such technologies, but they are kept under tight rein.

    And the plausibility of such an endeavour will surely grow as our technology advances.
     
  12. Seattle Valued Senior Member

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    2,241
    It's an assumption on your part that I"m being hysterical and uninformed and am overly simplifying. Of course I'm simplifying just as you are assuming. Both are necessary to have brief conversations.

    You have (as a species) to still be around when the technology is available. You have to use great resources (under some scenarios all of a planets resources) to accomplish some of these feats.

    There is the fuel, food, other supplies, the weight of all this to be carried a substantial fraction of the speed of light. You have to stay healthy. We may actually may not be designed well enough to survive a multi-year trip/stay on Mars.

    You can't just take two people and expect for the species to survive either. It doesn't work that way with darter snails and it takes a decent "sample" size for humans as well to be sustainable.

    They also have to stay alive on a planet not designed for humans.

    There is the issue of gravity, Gamma rays, space partials encountered along the way at those speeds. If it isn't a success than there may not be time to try again. It isn't a matter of trying it all. We can't do everything. Why do you think we aren't still on the Moon?
     
  13. DaveC426913 Valued Senior Member

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    6,987
    I was not suggesting either. I know you are informed. I meant this:
    .
    .
    The remainder of your post can be taken as granted. These are all challenges (will be challenges).
     
  14. Baldeee Valued Senior Member

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    1,104
    One quirk about travelling interstellar, when such occurs, will be that the first to leave might well be the last to arrive.

    Unless some paradigm shift in propulsion tech hits beforehand, the first pioneers will likely be on generation ships - taking 100s of years to travel even the few light-years to our closest suitable neighbours, but with the rate of progression in tech between when they leave our solar system and when they arrive at the destination, it may be that subsequent launches get there first, able to travel many times quicker due to technological advances.
    Not saying that it will happen, only that it's a wonderful possibility.
    Imagine if the first explorers to the Americas found that when they arrived there was a sea-plane at the shore, with people from their own country already having set up camp.

    So it may be that we never will get to the stars until travel becomes within a human life-span, or small fraction thereof, because we may always be thinking that we'll get overtaken, making the purpose of the trip redundant.
    Unless, of course, the journey itself becomes the reason, rather than the destination.

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  15. Seattle Valued Senior Member

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    The bummer will be those who leave on generational ships thinking the Earth was going to be destroyed only to find out that everything is fine back on Earth and they are left living on a space ship or trying to live on another planet that is not nearly as suitable as Earth.

    Kind of like preppers living in a bunker eating K-rations for years only to find out that everything is "swell" outside of the bunker.

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  16. DaveC426913 Valued Senior Member

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    That would make a great story.


    Imagine the GenShip colonists - all salt-of the-Earth explorer-pioneer-farmers - setting out on a one-way journey, destining their ten generations of ancestors/descendants to an uncertain future. Imagine how furious they would be upon arriving at their home world after centuries, to take possession of their 10 generational Birthright - only to find their world literally snatched from beneath them by a bunch of cocky, freshly-rested, perfectly-healthy and technologically-superior young d-bags.
     
  17. Baldeee Valued Senior Member

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    1,104
    Truth be told, either it was an idea from short story I have actually read (but if so I can't recall which or by whom), or it was something my friends and I have discussed when talking, as we do, about ideas for short stories.
    But when I write a version of it, I'll send you a copy!

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  18. ForrestDean Registered Senior Member

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    Magnetic Field Basics
     
  19. origin Trump is the best argument against a democracy. Valued Senior Member

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    What does the earths real magnetic field have to do with Seattle's strange claim that the Earth has a biomagnetic field.
     
  20. ForrestDean Registered Senior Member

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    I have no idea. I haven't read any of Seattle's posts in this thread.
     
  21. origin Trump is the best argument against a democracy. Valued Senior Member

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    OK let's see if we can make this easier.
    What does the earths real magnetic field have to do with the strange claim that the Earth has a biomagnetic field?

    Edit to add:
    Ha-ha, oh, now I see the issue, it was YOU that made the strange claim about the earth having a biomagnetic field!!!

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    Last edited: Nov 1, 2017
  22. origin Trump is the best argument against a democracy. Valued Senior Member

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    2 things:
    1. The planet was not designed for humans, we adapted to the planet.
    2. I accidently attributed the idea of a biomagnetic field to you and I am not at all sure you made. My bad.
    Edit to add: It was ForrestDean's claim.
     
    Last edited: Nov 1, 2017
  23. ForrestDean Registered Senior Member

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    291
    I agree.

    Not a problem. Basically, I was just saying earlier that through adaptation and evolution our body's magnetic field is linked to the Earth's magnetic field. And since I feel pretty certain that each planet has its own unique magnetic field, our bodies may not fair to well to be ripped away from this planet and placed on another planet who's magnetic field may be radically different than ours.
     

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