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When can mankind reach the nearest stars?

Discussion in 'Sci-Fi and Fantasy Talk' started by hotenka, Mar 12, 2013.

  1. hotenka

    hotenka Scout

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    There are a number of milestones and challenges for mankind if we are to contemplate travelling to our nearest stars, 5-20 light years away.

    We must first establish a large moon-base towards mid/end of this century. This is feasible because we have discovered vast amounts of ice at the poles giving us water to drink, oxygen to breathe and hydrogen for power. Structurally, moon-base would look like a huge Eden Project with specially designed plastic interlocking blocks to resist the vacuum.
    Then in the early 22nd century we would have a base on Mars. This would be the nerve centre for a star mission and a suitable starship would be constructed in weightless orbit around the planet. Our mission would launch from here and use the huge gravitational pull of Jupiter to accelerate our craft.

    Now there are 3 key technical challenges for us to solve over the next century to make a mission lasting 20 years feasible. Firstly, we have to be able to travel at a significant fraction of the speed of light and secondly we have to develop technology for extended human hibernation by cryo or other techniques. Thirdly, and absolutely vital, we must develop artificial intelligence - computers so powerful and reliable that we can trust them to look after a starship with its precious cargo of hibernating humans throughout a 20 year voyage. I will talk in more detail about each of these in my next 3 blogs.

    To answer my question - I think in about 150 year’s time but I would be fascinated to hear your views.

    I have visualised such a journey to the stars in my book - The Blue People of Cloud Planet- available as an e-book on Amazon Kindle [eleven 5* reviews] and shortly to be available in paperback from Feedaread.
     

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  2. Acclamator

    Acclamator Ensign

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    150-200 years. IMO, it's could be possible to make first interstelar trips in 23 century. And, I could add some points here, which I see critical too. The first point, I would add- find ultra cheap way to get to orbit. Like, long trip requires bigger plane or ship. So, even with usage of cryo sleep technology, ship need to have lots of space to cary stuff. Bigger size=bigger mass=harder to lift it. Now, with our technology, even if it could be possible, we would need astronomical resources to perform lifting massive ship for long trips from Earth's ground into our orbit.
    Second point, and It's my opinion, which you may not share- establish orbital "shipjards". Yes, shipjards, where we could make final assemble of ships, which could fly for long period of time with astronauts on board. Still, it's much more easer to lift massive constructions in space by parts or modules. When we going to have such technologies, industries and raw materials (yeah, I belive that also need), then interstelart travels will be much couser to us.
    The last problem for me, that Im not sure, that Im going to stay alive after 200 years... But I SOOO want to see this...Eh...
     
  3. hotenka

    hotenka Scout

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    Let us imagine a journey to a star 10 light years away. We start from Mars orbit and outside the planet’s gravitational pull and use advanced rocket technology to reach Jupiter. This is a journey of 555 million kilometres [km] taking 7-8 months at 100,000 km per hour. [Approx. estimate of future capability]
    We use the immense mass of Jupiter to attract and accelerate our craft onto a collision course [initially] and at the critical moment re-fire the advanced rockets to sling our spaceship around the gas giant and onto its new trajectory and new speed of 1 million km/hour.
    Now we start the nuclear reactor, the only power plant capable of sustaining thrust over a 20 year journey [unless we discover something remarkable during the next 100 years]. The heat output from this reactor would be used to power a new type of drive capable of pushing our craft towards light speed. I will describe one concept which has been around for decades, surprisingly – the ion drive.
    Here a stream of positively charged hydrogen ions [H+] is ejected at high speed from the rear of the object being propelled. The thrust is small but in the vacuum of space even a large object can be manoeuvred and accelerated provided you have enough thrusters. The ion drive of a starship is likely to be 50-80 metres in diameter and each of the thrusters say 10 cm round. You could get over 500,000 thrusters in this drive [clustered around the advanced rockets] all contributing their power from the emitting stream of hydrogen ions.
    By providing constant sufficient acceleration you would design to accelerate from 0.001c to 0.5c in 1 year [c = speed of light – see my previous Blog].
    Thus our journey to a star 10 light years away would be approximately 23 years – 2 years to accelerate, 20 to get there and 1 year to slow down to a manageable speed to orbit around a target planet of our destination star.
    I’m sure the mathematicians among you can calculate the acceleration required and the typical thrust needed from each tube – can we achieve this in 150 years time?

    I think we can and in 2150 my starship leaves Mars for the star Seren, 10 light years away, in search of - The Blue People of Cloud Planet.
     
  4. Mirelly

    Mirelly Mouthy Cow

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    Sorry for two reasons.

    First this looks like a spammy sales pitch. I am always suspicious of ebooks with 100% 5* ratings. Nothing is that perfect.

    Second ion propulsion for a starship is not a believable technology for the time-scale you suggest. Ion engines have a limited lifetime -- admittedly they might easily last for the duration of burn your outline proposes, but there is a major problem with you acceleration, Ion propulsion thrust is extremely small: 1E-6 g for a single thruster acting on 1,000Kg payload. Any believable starship would mass in the 500,000 ton range (including the ion engine propellant), so your 500,000 thrusters would be no more effective. So, sadly, at that level of thrust, 2 years acceleration would probably not achieve escape velocity from the solar system, let alone 0.5c (and yes I know your outline describes the achievement of solar escape velocity by the gravitational slingshot employed by NASA in numerous missions -- including Voyager and Pioneer), but the plain fact remains that acceleration from cometary velocities to significant fractions of lightspeed cannot be achieved in meaningful timeframes at accelerations of 1E-6g. To achieve 0.5c in two years you would need to accelerate at 0.24G which is some significantly larger degree of improvement over the power of current designs and theoretical possibilities.

    The novel would need to be as good as your reviews suggest it is -- and some -- for one to suspend the disbelief that in less than 150 years technology could boost the output of such feeble propulsion units to such a level.

    A more believable technology might be inertial confinement pulse fusion, or even Bussard ramjets or anti-matter catalysed fusion.

    Sorry if this seems blunt, but you did ask. ;)
     
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  5. Kevin

    Kevin Code Monkey Staff Abductee

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    Yep, the first post appears to be a copy & paste from another location for the purpose of including the link at the end. :(

    {Kevin makes mental note to double-check any tech facts before he ever writes & releases any speculative fiction pieces...}

    Sometimes blunt is good. :)
     
  6. Acclamator

    Acclamator Ensign

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    Sorry for not patriotic minds, but I belive, we gona find/adapt some kind of alien tech for interstelar travels to our ships. May be, we could try to reach nearest stars with our own tech, but for longer travels we need something other than propulsion way of move.
     
  7. Mirelly

    Mirelly Mouthy Cow

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    LOL ... I omitted to mention that I attempted to read the Amazon "look inside" sample. Yeesh. It was grammatical and properly spelled ... but architecturally it hurt the eyes. Dedications, intros, prologues, flashbacks, flashforwards, anachronistic impossibilities (without explanation). It was about as gripping as a bout of gastric flu.

    The Martian by Andy Weir (so not by me ... nor by anyone I know) is a fabulous self-published novel which had me gripped from the first sentence. Unlike the OP's novel it has a range of ratings from 1 to 5 stars. It was also recommended to me by a good close RL friend whose opinion I value and who has two self-published novels of her which are receiving encouraging reviews (I have been forbidden to rate them, for obvious reasons!) :whistle:
     
  8. Kevin

    Kevin Code Monkey Staff Abductee

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    [ NOTE: I merged the OPs two original threads together since they are the same topic. ]
     
  9. hotenka

    hotenka Scout

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    Thank you, Mirelli, for your observations, I did want someone to respond with thrust figures for ion drive and you have done this in detail. I agree that I would need a lot more thrusters or a different method of propulsion and I will research your suggestions. I disagree with your weight of a starship. I think that in 100 years from now we will have developed incredibly strong light-weight composites enabling a much lighter large structure to be fabricated in space and then propelled towards the stars. Can't wait for your views when I post on cryo-hibernation!
     
  10. Mirelly

    Mirelly Mouthy Cow

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    Cryo-sleep ... hmm. My degree was biological. I believe it is probably possible now to suspend life, by a relatively simple method of replacing the entire blood volume with a substitute fluid, chilling the body to 1 degree Celsius, and then immersing the subject in a suitable liquid. The circulation should be maintained mechanically by an external heart/lung/kidney doo-hickey. Of course with 25 year flight times, the crew could travel awake and arrive young enough to raise the first generation of starborn (assuming advances in anti-aging medicine).

    Mass of the ship? At 0.5c, the interstellar medium will be impacting the bow of the ship with x-ray energy. If I were thinking of boarding such a vessel, I'd want something a bit more low-tech metallic between me and cold space than some superannuated ultra plastic. :p

    Pulse fusion is a well established theoretical technology with phenomenal thrust possibilities. The actuality is presently stymied by a, so far, lack of progress in creating a working light-weight ignition system. Laser ignition seems most promising, although the power requirements would require a decent fusion power plant. All told we're talking about one hell of a lot of mass; and let's not forget the thousands of tons of deuterium fuel pellets!

    A final caution to consider is the all-in-one and one-way-trip nature of a manned interstellar expedition. It would be foolhardy to send supplies separately (unnecessary duplication of engines compounded by the need to rely on automatics still working decades later to deliver the package at exactly the right place at the right time. It's acceptable to plan a Mars trip that way, but out of the question to consider it a viable way of getting to another star. Therefore the ship must carry everything. Shuttles to get the colonists down. One-way bulk landers to land large plant and materiel.

    Many SF writers like to use artificial wombs for raising frozen embryos. Frankly I have grave doubts that we shall be able make such technology workable any time soon. What Nature does so effortlessly we poor monkeys still barely comprehend how it all works in any meaningful sense which would lead any rational person to imagine we're on the threshold of getting there. Not only are we not on the threshold, we've not even found the door knob to crack the bloody door open for a sneak preview. I have a much more inventive -- and technologically possible -- solution to the problem of raising animals from frozen embryos. Raising humans will just have to be done the old fashioned way only the first generation would have to be shipped as frozen embryos; it's conceivable that the human cargo could be kept alive, but their gonads would take far too much cosmic ray damage however well shielded the craft. The expedition medic would be busy curing all sorts of tumours and cancers. Furthermore, places for men in the ship would be at a premium. Their sperm would travel well in liquid nitrogen, and after that contribution their use in procreation is pretty much done. I suggest a ratio of 2 or 3 females to one male; and as a woman, I'm not that happy about that ... but it's what works, rather than what's best for the individual.
     
  11. Birdman

    Birdman Birdman

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    Or....we could just wait for alien contact and use their tech.

    I also find it somewhat disturbing that everyone failed to mention the stargate system used in the tv series. That was already developed and put in place by 'ancients', we might as well make use of it.:cautious::ROFLMAO:

    Now of course I'm just kidding, which I can afford to do since I have already completed my starship. I just used a telephone booth. :whistle:

    Lol, I'm sorry, I just thought the thread needed a bit of humor and I've not been on the forum in a long, long time. Still a good thread and I enjoyed reading it. Sorry that I can't contribute more, sadly I'm not smart enough to throw out any revelations on the matter. I love the idea of traveling to the stars (would rather see habitable planets) but until we get things in order here on planet earth, I think the doorway to the heavens will remain shut.

    Realistically, Gene Roddenberry was probably the most realistic, there isn't enough money in existnce to fund such endeavors so it'll probably take a fundamental paradigm shift in the way we view currency before we can even dream of building space stations or space harbors or intergalactic travel. Of course I guess we don't worry too much about paying debt now so I could be wrong about that.

    Secondly, I think it's safe to say the first three things we'll have to develop is a safe and easy way to reach orbit and re-enter orbit. Some form of energy shielding so that we aren't all rendered sterile and cancerous...good gawd Mirelly... Thirdly an antimatter generator and/or similar drive, carrying fuel so far in every senario I have ever read, is probably the biggest limiting factor next to overall empty ship weight vs thrust. Even if we should happen to develop some form of propulsion with plenty of thrust, it'll be difficult to use it without tearing the ship apart and we don't know for sure what kind of gravity wells we may encounter so any honest attempt is going to need a starfighter mentality that is powerful enough to be piloted within reason. I don't like the idea of a priceless mission and ship being unable to escape an unseen gravitational force 8 light years from home because an ion drive didn't have the power to escape it. The propulsion system needs to use some element harvestable from space itself to be feasible.
    Oh, and a fourth actually, we'll have to develop some sort of artificial gravity system for the ship. I'm thinking possibly the same system tha tgenerates the protective shielding may also actually end up providing the artificial gravity and probably be integrated into the propulsion system in some manner.
     
  12. Mirelly

    Mirelly Mouthy Cow

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    Nothing wrong with humour, Birdman. SF doesn't need to be bone-dry and there's plenty of comedy SF to rpove the point. Moreover SF doesn't need to be feasible or believable to be enjoyable. The only time SF needs to be grounded in reality is when one is writing what I call "hard science fiction" in which the science needs to remain more or less firmly anchored to the laws of physics.

    Such a system exists and I have mentioned it before. The Bussard Ramjet was proposed in 1960 by a serious physicist (Richard Bussard). It proposes using magnetic fields to capture interstellar hydrogen and compress it to power a fusion drive. Sadly hydrogen is not easy to get fusing ... if it were stars would go KAPOW rather than last billions of years! Moreover once the ship gets really shifting the incoming hydrogen atoms would be "coming in" at gamma ray energies ... sort of dangerous.

    Artificial gravity doesn't have to be invented. One can either spin up the ship, or have an engine powerful enough to give you a one gravity acceleration and keep it on all the time. That has the additional benefit of getting you up to relativistic velocities (greater than 90% light speed). At 90% the speed of light, you would travel the 4 and bit light years to Alpha Centauri in just 2 years ship's time with additional benefit of "artificial" gravity all the way and without actually breaking any laws of physics. :cool:
     
  13. Birdman

    Birdman Birdman

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    I don't see the Bussard system as practical enough to work or powerful enough to be comfortable.

    But...it's something real to work with and has a few concepts that may be hybridized with some other proposals to make a unified and realistic system. Maybe collecting the space medium and using lasers to manipulate it would be more efficient and sustainable. Can low powered lasers be amplified using something like ceramic mirrors to create a 'light combustion chamber' ?

    How about a magnetic field that ionizes at one end and deionizes at the other to create a pull/push effect through the space medium itself? I know they are working on space time warping to achive this affect but the power requirements are unrealistic so far.

    Still have the problem of shielding. I wonder is a material could be developed that generates power. Maybe something like a solar cell carbon fiber skin that also neutralizes radiation or counters it?

    As far as artificial gavity goes, I don't like the concept of centrifugal gravity, it makes full use of the ship space too challenging in my opinion and neither of the solutions listed are sustainable at static ship states. I'd prefer an artificial gravity option that works all the time, moving or not and that is constant strength the breadth and length of the ship. Otherwise, eventually in ship design, one ends up with areas that are under gravity and some that aren't and it makes engineering ship sytems exponentially harder and inefficient. Simply systems to move around the ship become weight challenging to work around the transition areas.
     
  14. Mirelly

    Mirelly Mouthy Cow

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    You make some good points. However do not dismiss centrifugal gravity too lightly. For sure it is a dead cert which is energy cheap. Any possible future-tech which can generate a gravity field is not likely to be nearly so energy economical. The main problem with spin-gravity is the radius of rotation. If that radius is too small the gravity gradient will be steep ... one's head would be substantially lighter than one's feet ... nauseating.

    An ideal diameter would exceed 300 metres. This presents a lot of opportunities for efficient ship design. All the radioactive engine components can be at the hub; and an engine can thrust just as well if it's spinning as it could not spinning, so no need for ornery bearings. A simple toroid would not have substantial gravity variations and would thus not have engineering problems you worry about.

    Good to exchange view with you. This is what I joined for! :)
     
  15. Birdman

    Birdman Birdman

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    Likewise.;)
    Thanks, well this is one area that I find exceedingly exciting and interresting and I love thought experiments and exercises. I just wish I had the IQ to do some good....I'm generally long on concept and short on technical data and calculations...blah.:X3:

    Oh I haven't discounted centrifugal gravity, I'm afraid we're probably confined to using it actually, I just don't like the concept because it presents a lot of complications at the engeneering level for things like elevators (unless the entire ship is spinning) If the entire ship is spinning then the low gravity areas and the transition areas become hard to work in and deal with...still it's not impossible and it's pretty unlikely we'll have anything else for quite some time if ever.

    The 300 meter figure is one I've seen thrown around before and is one thing I didn't care for. I know a ship doesn't need necessarily to be arodynamic in space but the larger the surface area exposed toward direction of travel, the more likely a hull breech will be by some unpredicted particle or body. If that is countered with some sort of energy shielding, more than likely that will cause a significant drag in some form or another. Whenever simple hydrogen collection from a magnetic collection field can become an issue obviously a 300 meter wide ship could have a lot of issues. I think any design will end up having to be cigar shaped to an extent.

    G-force gravity from thrust will be hard to dampen at some point and I don't like the potential consequences at the end of the trip.:eek:

    The key will be finding an absolute in what actually makes gavity work. Just when we think we have it pinned down some darned genius seems to walk up and say uhm...thats not right but I don't know what makes it work either. I never liked the thought of Einsteins concept of warped space time...always seemed mechanically flawed to me for some reason. Lack of degrading orbit between us and the sun for one thing as well as a clear concept of exactly what space time fabric is, how it's layered to allow specific equilibrium...I don't know...just seems out of mechanical sinc to me. Newtons initial thoughts seem more consistant but probably because I'm a step above the IQ of an ape (maybe).

    At any rate, I almost like the thought of clothing infiltrated with magnetic particles and magnetic deck floors better than any other practical options so far. Cheap and easy with no power requirements at all. Or maybe an electromagnetic flooring. Inertia dampening could be achieved to a certain extent by computer, increasing or decreasing the amount of pull....could even be directional if engineered correctly and integrated into the compartments...though it may be tricky to not interfere with electronics (?).

    Has anyone ever experimented with a heavy spinning orb of iron in space? I wonder what would happen?

    Still doesn't solve a problem of plants not growing worth a darn in zero gravity.....Perhaps that would be solved in travel with simple G-force accelerational gravity in a sidways setting biodome compartment.
     
  16. Mirelly

    Mirelly Mouthy Cow

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    Ah .... you might think that a 300 metre diameter ship presents a big fat target, but mounted to a Bussard ramjet the ship would be dwarfed by the width of it electromagnetic ramscoop which would need to suck in mega quantities of space to get the hydrogen fuel. We're unfortunate in that our bit of the galaxy is called the Local Bubble ... 300 light years across with only half a hydrogen atom per cubic centimetre. This means you'd need a billion cubic kilometres of space to get just two grams of H ... luckily at the start and end of the mission you'd be close to a star, so hydrogen density would be a lot greater.

    A 3oo metre diameter habitat would measure a kilometre around. Even if there only one deck, if we made it 50 metres wide, there would 5 hectares of "flat" ground. Enough for hydroponics to supply food and oxygen for a crew of perhaps a hundred or more.
     
  17. Birdman

    Birdman Birdman

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    The ramscoop probably wouldn't be sufficient to protect the ship from heavy particles or chunks...even if it was, there's no way the Bussard would have power enough to ever be feasible. It would never yeild a net gain in acceleration for a ship that size and if you used a larger engine, there wouldn't be enough fuel collectable to fuel it.

    Yes the Hydrogen content in our area of space is relatively low and the Bussard was only proposed using the ionized hydrogen to make matters worse. Which is why I discounted the Bussard as we know it so far. The basic concept is still possibly viable in some form but the ship configuration won't be very forgiving due to the net size and thrust limitations. To make matters worse, any return trip will be incoming against solar winds.

    It's not impossible, we just have to find the way ...just as man did when he first braved and conquered the oceans.
     
  18. Mirelly

    Mirelly Mouthy Cow

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    Yup. You're quite about the heavy chunks. However the same ancient supernovae which thinned out this area of the galaxy would also have cleared away the dust and chunks. The only real threat would be an unlucky encounter with a wandering comet. That would just be unlucky, because the odds of finding one would have to be in the billions to one against. However we can agree that good old Bussard is thoroughly impractical -- I never said otherwise -- I merely argue that it doesn't actually break the laws of physics.

    Of course you could go all cutting edge and think about an EmDrive (a reactionless drive??) Plenty of research on that.

    Sadly hyperspace refuses to add itself to the laws of fizzix ... the LHC's recent results have, apparently, made the existence of large scale additional dimensions even more unlikely -- theoretically -- than previously thought. Current thinking is that any additional dimensions are folded up tight at the subatomic scale ... not very useful.

    I'm happy with the tech I am using in my own novel. Two ships. One powered by anti-matter catalysed fusion, the other a pulse fusion powered ship using lithium-deuterium fuel pellets. Both are shielded by their own fuel tanks and take 40-50 years to reach the Centaurus system.
     
  19. Birdman

    Birdman Birdman

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    Very interesting stuff. I had not seen the EmDrive. I looked into it a little, I can see why it caught such flak being a closed system, among other things... I'm not smart enough to give much of an opinion on it sadly. Development seems to continue along despite a lack of acceptance or local peer review. I can see both sides of the debate, the ultimate authority is if it's tested and works and is open for scrutiny I guess. Very very interesting though. I've lost count of the number of supposed breakthrough propulsion systems though at this point. Peoples propensity for deciet is awe inspiring, lol.

    We'll see what the future reveals about hyperspace. It's a rough concept to fathom for three dimensional beings such as us. Even if an alien race gave us the technology it may well be beyond our understanding.

    40-50 years...not bad considering it's what..over 25 trillion miles. Still, I'm not happy with that, that should be a day trip.:ROFLMAO:
     
  20. Ken Jeavus

    Ken Jeavus Scout

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    Interesting discussion. But whenever I think about this stuff I wonder if we're not just thinking about creating "faster horses" so to speak. So for example say 3000 years ago we're all thinking of a way to get a message to the next city. I suggest we run instead of walk. You suggest we train dogs to carry messages. Another suggests horses. So we train horses but we're not satisfied, so we think of things we can do to the horse, like no rider, file their hooves, etc. You get my point.

    But now we're visited by someone from the distant future and they say, gee why not just fax it! Not only wouldn't we be able to understand him, we wouldn't be able to understand his explanation. It's sorta like the thing Donald Rumsfeld said awhile back about Not knowing what we don't know. Everybody laughed at him but he made a great point. (BTW, please don't think for even a second that I like/endorse/stand behind anything he stands for). We can only discuss issues in the context of what we know or can extrapolate from.

    For all we know there may be ways to travel we can't even conceive of. There may be notions/technologies etc. that make the idea of travel itself rather outdated. I think Arthur C Clarke kind of comes close to this in Childhoods End.

    (BTW if anyone knows of a book where this kind of ultra-travel is explored please post)
     

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