TheBlueKerbal

Generation Ships vs Cryogenic Sleep Ships

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1 hour ago, Rejected Spawn said:

 

As for cryostasis I'll touch on it a little again below... 

Regarding that plasma bubble, I'm gonna simplify the math a little and boil it down to what matters for those who may be interested but not *super* interested. First of all; some kind of non solid shield around the ship would be 100% essential for survival, we could get wiped out before even making it past the moon if we didn't have that since space does have tiny debris all over the place and the debris by itself is moving at deadly speeds. Let's look at what kinds of speeds we're talking about for the ship then. The speed of light with a bit of rounding is 300.000.000m/s. The speed of sound in our thick atmosphere is about 343m/s. When we fire a rifle bullet that travels at the speed of sound, that thing gets pretty gosh darn far and is still rather deadly. Increasing the speed of the bullet means it's going to break apart - higher speeds make it break apart more, but it will keep posing a major threat for a very long distance no matter what. Reach a high enough speed and the bullet essentially vaporizes in a microsecond but the individual atoms (or even ions) will still be travelling a very substantial distance and rip apart anything in their path as well as create a massive shockwave and releasing immense heat. Taking the speed up to just 1% of the speed of light, this bullet is going to be so deadly it's not even funny. That's in our thick atmosphere. How dense and big would the cloud of gas or plasma have to be to shield our precious ship from the impact of something like that? Don't ask me, I'm not interested enough to do the math properly to be honest, however using any ballpark estimate we probably all conclude that it would have to be impossibly huge, way beyond what seems to be within the realm of what we can build any decade soon. Interstellar space isn't empty, there will be pebbles far bigger than a meek bullet out there and we're more than a little likely to hit one dead on. My take on this is that we just won't be going anywhere all that fast. On a related sidenote, everyone keeps asking why the aliens that should be out there haven't come over to play... yeah, they probably like being alive and won't be going interstellar unless they have to for survival reasons.

I'm in agreement that planets solve a number of issues but don't forget that they also come with other issues instead. Any planet that has an atmosphere is most likely a toxic wasteland, any that doesn't have one is not going to provide much better shielding against radiation and space debris than if you were on a space station, it just limits how many directions you can get hit from. Sitting on a planet means that if there is an asteroid heading for it you have no choice but to drop everything and evacuate, a space station however is both a smaller target and can just get out of the way if need be. Now if we presume we find a planet like earth, it doesn't have terrible atmosphere and it has all the good stuff we liked about this ball of dirt, it may also have life on it... Does that mean we're better off or worse off? Probably worse off. If any complex life has evolved in a similar fashion to earth life there's a high probability some of this life will be bacterial, viral, parasitic or severely toxic - in an alien fashion that our bodies have never evolved to handle. There are tribes of humans on earth that can't be contacted because they'd likely die from exposure to the bacterial and viral evolution that's been going on in the rest of the worlds population, their immune system is just outdated by hundreds of generations... imagine your immune system being many times worse off than that. Our best planetary bet is to claim a guaranteed dead world, terraform it over a huge span of time and then hope we can stay there without any issues. Compared to that I think a colossal space station where hundreds of millions of us live in comfort and safety sounds like a much better idea. Keep in mind that the station might as well be as big as we can possibly make it, if we have the waste heat problem covered the upper size limit skyrockets.

Regarding non frozen cryostasis, there are loads of things in our blood other than oxygen carriers and immune cells, this video by Kurzgesagt covers a bit of the complexity involved: https://youtu.be/BSypUV6QUNw (good channel, usually almost completely objective, does inject opinion in some topics though so take those with a bucket of salt) Moving further from regular cells we are also home to a huge amount of bacteria that are essential to our health, if we modify our bodies and become an unsuitable home for them, there is substantial risk it will greatly affect our health. If you take an interest here's a rather amusing Joe Scott video on the topic: https://youtu.be/iytAHXo2_V8 Anyway I'd say cryostasis (as a broad term including just "chilling out") is way too dangerous to get into any decade soon, there are far too many factors that we know far too little about to safely mess with. I'd strongly prefer simply staying awake playing tetris for a thousand years instead of taking a potentially deadly powernap on the way over to the nearest star. :P

Well i always thought it would be arranged similar to a wipple shield; you'd have the primary "Impact" layer which is just intended to break the projectile apart . And the secondary interior "Absorption" layer which would essentially catch the debris; the idea isn't to burn it all up upon impact. That's like trying to put enough cars in front of a train to stop it; it's possible but better to just find the switch and send the train across a different track. The "Impact" layer could be much thinner and further out; allowing the "Absorption" layer to be much thicker and closer. But i'm not denying this would be a massive effort; especially since we haven't even cracked fusion.

As for the second; you make very good points. Especially since many of the planet candidates out there likely had their atmospheres blasted off billions of years ago.

And yeah; there's a very good reason we don't have synthetic blood. Though i didn't consider the effects that any form of cryo would have on the human microbiome.

So overall solid reply, and i don't disagree with much if any of it.

I do think eventually we would overcome many of these challenges, but like you i do wonder at what point you end up with technology so advanced that you either end up forgoing planets entirely. I also do wonder if perhaps many jump to higher dimensions; since even if they didn't exist properly you could just make them if you were a K III civilization. That's getting well off-topic though.

I'm also looking foward to any developments you have with your accelerator experiments; sounds like you may have something potentially interesting on your hands.

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Y'know interstellar? The movie? Yeah. They use cryogenic sleep. I think. On the transfer from (spoiler alert)

Spoiler

Earth to Saturn (If I remember correctly). At the end, when they get picked up be Cooper station, I'm rather sure that that was an generation ship. So for the masses, I'd say generation ships, but for a small group of people, cryogenic sleep. Which makes sence anyways, since cryogenic sleep is due to use a lot of energy.

 

Edited by έķ νίĻĻάίή

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5 hours ago, Rejected Spawn said:

  Regarding that plasma bubble, I'm gonna simplify the math a little and boil it down to what matters for those who may be interested but not *super* interested. First of all; some kind of non solid shield around the ship would be 100% essential for survival, we could get wiped out before even making it past the moon if we didn't have that since space does have tiny debris all over the place and the debris by itself is moving at deadly speeds. Let's look at what kinds of speeds we're talking about for the ship then. The speed of light with a bit of rounding is 300.000.000m/s. The speed of sound in our thick atmosphere is about 343m/s. When we fire a rifle bullet that travels at the speed of sound, that thing gets pretty gosh darn far and is still rather deadly. Increasing the speed of the bullet means it's going to break apart - higher speeds make it break apart more, but it will keep posing a major threat for a very long distance no matter what. Reach a high enough speed and the bullet essentially vaporizes in a microsecond but the individual atoms (or even ions) will still be travelling a very substantial distance and rip apart anything in their path as well as create a massive shockwave and releasing immense heat. Taking the speed up to just 1% of the speed of light, this bullet is going to be so deadly it's not even funny. That's in our thick atmosphere. How dense and big would the cloud of gas or plasma have to be to shield our precious ship from the impact of something like that? Don't ask me, I'm not interested enough to do the math properly to be honest, however using any ballpark estimate we probably all conclude that it would have to be impossibly huge, way beyond what seems to be within the realm of what we can build any decade soon. Interstellar space isn't empty, there will be pebbles far bigger than a meek bullet out there and we're more than a little likely to hit one dead on. My take on this is that we just won't be going anywhere all that fast. On a related sidenote, everyone keeps asking why the aliens that should be out there haven't come over to play... yeah, they probably like being alive and won't be going interstellar unless they have to for survival reasons.

It looks like our kerbals are going to need a 100 meter thick shield of boron nitride nanotubes, carbon nanotubes and/or Carbyne to travel 4.2 light years in 22 years, that is if the developers implement interstellar debris. or this:

Quote

Well i always thought it would be arranged similar to a wipple shield; you'd have the primary "Impact" layer which is just intended to break the projectile apart . And the secondary interior "Absorption" layer which would essentially catch the debris; the idea isn't to burn it all up upon impact. That's like trying to put enough cars in front of a train to stop it; it's possible but better to just find the switch and send the train across a different track. The "Impact" layer could be much thinner and further out; allowing the "Absorption" layer to be much thicker and closer. But i'm not denying this would be a massive effort; especially since we haven't even cracked fusion.

 

7 hours ago, Klapaucius said:

I think Kerbals have evolved an amazing capacity to just zone out. Mix that with genetics similar to those frogs that can freeze solid and thaw out again (explains the green pigment) and you have a species designed for space travel.

yes

 

5 hours ago, Rejected Spawn said:

I'd strongly prefer simply staying awake playing tetris for a thousand years instead of taking a potentially deadly powernap on the way over to the nearest star. :P

I would rather spend the 1500 year trip to Kepler-186f playing ksp.

Edited by Dirkidirk

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21 hours ago, Terwin said:

Even if you have a 100% recyclable system, you will still need energy inputs, and interstellar space in not a great place for sonar panels, so your vessel will have a finite duration unless you have some new sort of inexhaustible energy(ie a perpetual motion machine).

I honestly think this would be a good role for a Bussard Ramjet - Make the ship an open system with input being interstellar gas.  Siphon off heavier elements as it passes through, and use that to replace what is lost.  You'd still need a 99+% recycle system, but it no longer needs to be 100% and you can also siphon some power off the ramjet fusion.

There are complaints about Bussard Ramjets - but they mostly are that it's slower than other methods of traveling between the stars.  Take out the destination, and those complaints are no longer relevant.

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2 hours ago, έķ νίĻĻάίή said:

Y'know interstellar? The movie? Yeah. They use cryogenic sleep.

And Pandorum as well, including the sudden awakening in a company of earlier nonsleepers.

(Caution, violence)

Spoiler

"Say cheese!"
h2one2-pandorum-movie-review-1.jpg?w=497

 

2 hours ago, Dirkidirk said:

It looks like our kerbals are going to need a 100 meter thick shield of boron nitride nanotubes, carbon nanotubes and/or Carbyne to travel 4.2 light years in 42 years, that is if the developers implement interstellar debris. or this:

Or a cloud of ionized dust or protons in magnetic field.

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15 hours ago, Rejected Spawn said:

Biology Part Two: Guess you fellows don't check out much science that isn't about rockets, however there have been some major breakthroughs in figuring out why and how we age down on the molecular level, our life expectancy is quite possibly about to jump sky high and closely match that of Kerbals and we would easily live for multiple centuries - as long as our stupidity doesn't get to us first. Those who are interested in finding out more can check this video that does an adequate job of explaining it so the average person can easily understand; https://youtu.be/QRt7LjqJ45k Do note however that this isn't even the only stuff going on in the field.

This would be very nice, but it is not here yet, and might not be possible(but I hope it is).

15 hours ago, Rejected Spawn said:

Ship travel time: Since we won't be going extremely fast unless we want to die extremely fast the ship MUST have its own recycling system on an unprecedented scale, I've been saying a related thing for some time - "By the time we can reach planets in other solar systems, we no longer need planets at all." - because the immense scale of an interstellar ship and the mad timeframe involved make it ridiculous to get adamantly hung up on landing somewhere instead of just living on the ship perpetually. We'd be better off just migrating to a gigantic space station in the first place, hang out in nice scenic spots around this local star until it starts getting iffy and then pack up the entire station and migrate to the next star. By then the station might give the Death Star a real challenge in terms of size.

While I expect 80-85% recycling is probably fairly straight-forward(hydroponics or bacteria tank type set-up to recycle air and waste, but still needing some nutrients/vitamins and lots of spare parts), 100% recycling is not feasible(at a minimum you have gasses tunneling through bulk-heads and getting lost to space as well as parts wearing down and losing mass, even if you manage nearly 100% recycling of life-support), so I expect there will always be a need to harvest raw materials for any permanent or semi-permanent habitat(Asteroids are probably much more feasible then planets once we start getting good recycling however).

That said, we do currently have the technical capacity to assemble a (low-speed)generation-ship today, it would just need a very large volume of supplies to account for expected losses over time.(it might not be much better than frozen MREs, water filters, and chemical reverse-candles, but it could be done)

note: parker sun probe is ~68.8km/s relative to the sun, and is fastest human made craft relative to the sun.  At this speed, it would take ~8500 years to get to Alpha Centari(~4.3 ly)

A slow generation ship may not be practical, but we can at least be confident that it is possible.(and further developments will only make it more practical)

 

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On 1/28/2020 at 10:44 AM, mcwaffles2003 said:

Even sleeper ships are generation ships as crews will be required for maintaining and keeping secure those in cryostasis

 

Why would crew be required in sleeper ships? Obliviously we need crew for generation ships.  The 2 concepts have nothing in common. If ksp 2 has one of these it would be the sleeper ships similar to what deepfreeze does in KSP now. Generation ships are simply unpractical. They are also a waste of time and resources. 

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16 hours ago, Rejected Spawn said:

Biology Part Two: Guess you fellows don't check out much science that isn't about rockets, however there have been some major breakthroughs in figuring out why and how we age down on the molecular level, our life expectancy is quite possibly about to jump sky high and closely match that of Kerbals and we would easily live for multiple centuries - as long as our stupidity doesn't get to us first. Those who are interested in finding out more can check this video that does an adequate job of explaining it so the average person can easily understand; https://youtu.be/QRt7LjqJ45k Do note however that this isn't even the only stuff going on in the field.

We wouldn't really live that long though. You will just die from a bus knocking you over or your spouse murdering you. 

On 1/28/2020 at 12:26 PM, Rejected Spawn said:

Just an FYI here: Kerbals don't die of age. Ever. Will not change in KSP2. Also the only confirmed multiplying of kerbals is in colonies.

Guess the thread is over already.

That is only because no kerbal has ever lived long enough to prove otherwise. 

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On 1/29/2020 at 10:48 PM, OOM said:

Ships of generations is all nonsense. First, they are more complex, you need to create a fully reusable ecosystem. Secondly, problems with flight duration and ship reliability. Plus problems with the crew. A sleeping ship is much simpler, lighter. Only cryos technology is needed.

Kim Stanley Robinson's 2015 novel Aurora dealt with this. In human terms, what we do not consider is the social implications. What do you do when the subsequent generations have no interest in the mission their parents set out for them? Of course none of us ask to be born nor have any control over the circumstances we are born into, but a generational ship might put all that into a pressure cooker.

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2 hours ago, dave1904 said:

Obliviously we need crew for generation ships. 

DJ's, bartenders, room service.

We should presume that there will be not enough talented humans in some generation, so the ship should be fully automated in any case.

***

Harry Harrison's sci-fi novel
https://en.wikipedia.org/wiki/Captive_Universe

suggested another case: intended cultural degradation of the first onboard generation to let them think they just live in a perfect closed world, so it's ok.
At some moment a Chosen should be chosen. After the training and intellectual growth he gets access to the control room.

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Just now, kerbiloid said:

DJ's, bartenders, room service.

We should presume that there will be not enough talented humans in some generation, so the ship should be fully automated in any case.

***

Harry Harrison's sci-fi novel
https://en.wikipedia.org/wiki/Captive_Universe

suggested another case: intended cultural degradation of the first onboard generation to let them think they just live in a perfect closed world, so it's ok.
At some moment a Chosen should be chosen. After the training and intellectual growth he gets access to the control room.

I mean the sex part and I think we can both agree that talent in not necessary for it. Bartenders however essential :P 

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3 minutes ago, dave1904 said:

I mean the sex part and I think we can both agree that talent in not necessary for it. Bartenders however essential :P 

In this case we automatically get to the latter variant (Harry Harrison's), just without Aztec masks.

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