What are the odds for "close contact"?

[danscope]

I wonder if anyone who advocates traveling for centuries in a starship has ever been to sea....... for even a week, never mind 3 months ...
or 6 months...... or a year. Hmmmm..........
I would suggest that as a matter of fact, you would regret your choice in a very.... very...short time.
And when you close the hatch,.... that's it, .............for a very...very ...very long time indeed . And like Janis Joplin said:
" It's all the same day . "
It's really quite an interesting phenomena . Going on really long journeys , just like going to serve in the trenches is a lot easier to talk about ,
and a lot harder to actually do. I challenge any one of you to try it sometime. I should think that after the experience, you may perhaps
..."Think " differently.

[ravens_cry]

The thing is though, these things have been done without psychological harm to the participants. In fact ,there are those who have volunteered, and gladly, for such experiences. There are people who have sailed, alone, around the world. There are people who have uprooted their entire vies to move to a whole new continent, with any help as out of reach as to be on a different planet, and with less contact.

[theNater]

So you want to carry supplies for 1000 for a century, that is a very large ship, but it does reduce the probability of no more births ever.

Carrying that much in supplies invites some problems. Better to put the ability to grow food on the ship. Probably carry some seeds in case one kind of crop all dies out for some reason, and replace the seeds with new seeds from the first harvest.

Bigger ship means a bigger target for a small space rock.

Bigger ship also means more space for redundant systems, meaning one small space rock is less likely to be catastrophic.

Bigger ship means the children will usually have at least one playmate about the same age and twins or triplets can be compensated for by skipping up to 25 years of births. Skipping 25 years of births means a generation without any children which may produce unknown consequences.

Where are you getting 25 years of skipped births from? By my count, if you have 1000 people with life expectancy 100, you've got an average of 10 people each age. So you expect 10 births(and deaths) each year. Even if every pregnancy in a particular year results in triplets, you only need to go without births for two years to get back on track.

Large population also means that at least one person will have the drive and natural born talent to deal with difficult problems which will occur enroute and at the destination.

At least one; probably many. Especially with teaching that emphasizes problem-solving ability.

Large population means reduced inbreeding after the sperm bank and embryo bank become unreliable.

Large population even means the sperm and embryo banks can be backups, instead of primary population source. Having an all female crew becomes less necessary as total population size increases; 500 women on a ship of 1000 is a sufficient pool for confidence that there will be some able to bear children.

Is it reasonable to expect that several percent of those born on the ship can learn to do IVF skillfully?

Yes. It's a learnable skill, and would be highly valued. It would be reasonable for all children to be taught IVF procedures right along with other emergency procedures.

We maybe surprised that the average life span is about 100 instead of 50, but that perhaps does not matter if we have accommodations for 1000 people. How can we ensure that the passengers won't be extravagant with the supplies rather than minimalist?

One of the advantages of growing the food on-ship rather than carrying it all is that it prevents the perception of surplus. With the food grown each year being roughly enough to feed 1000 people, it encourages people not to be wasteful.

Hibernation of perhaps 2/3 of the crew may solve problems, as the useless eaters and non-conformists can be hibernated, if we ever have reliable hibernation for humans.

Hibernation is unnecessary. Given that food will be fairly scarce from year to year, a no-work, no-eat policy should severely limit the number of "useless eaters" around. I'm not sure what putting non-conformists into hibernation is meant to achieve, as they'd still have to be awakened eventually, and would be unlikely to develop a hankering for conformity in their sleep.

[theNater]

I wonder if anyone who advocates traveling for centuries in a starship has ever been to sea....... for even a week, never mind 3 months ...
or 6 months...... or a year. Hmmmm..........
I would suggest that as a matter of fact, you would regret your choice in a very.... very...short time.
And when you close the hatch,.... that's it, .............for a very...very ...very long time indeed . And like Janis Joplin said:
" It's all the same day . "
It's really quite an interesting phenomena . Going on really long journeys , just like going to serve in the trenches is a lot easier to talk about ,
and a lot harder to actually do. I challenge any one of you to try it sometime. I should think that after the experience, you may perhaps
..."Think " differently.

Who suggested that this would be fun or easy? All I've said is that it would be possible, which means that close contact with aliens is possible, so long as aliens exist.

[IsaacKuo]

Is it reasonable to expect that several percent of those born on the ship can learn to do IVF skillfully?

The challenging parts of IVF would all have been done back in the home system before freezing the embryos. The only part of IVF which needs to be done on the generation ship is thawing out the embryos and implanting them. This is essentially the same procedure as an IUI, and requires little more than a syringe with a long thin tube.

How can we ensure that the passengers won't be extravagant with the supplies rather than minimalist?

By only providing resources at a limited rate. A mission of this length won't be supplied using expendibles, but rather by recycling air/food/water.

This should be done using aeroponics--a high maintenance low tech method. High maintenance is good because it keeps the colonists experts at maintaining the system as well as giving them a full appreciation of how limited their resources are. In theory, a highly automated system could be designed which works for decades. But when it first breaks down, no one knows how to fix it!

The thick outer hull would be zero maintenance. The power source would also be zero maintenance--just a few big chunks of radioisotope. As far as the colonists are concerned, they're just eternally hot glowing rocks outside the greenhouse windows.

The embryo banks would be kept cold with passive radiator fins rather than refrigeration hardware--so they're also zero maintenance.

The big question is braking at the destination system.

[danscope]

I think your embryos etc would become sterile from expoosure to cosmic radiation. And I submit you will not get any radiation protection from some of the extraordinary radiation you will be exposed to on that journey. Your ship may coast to it's desination centuries from now.
It will have a cargo of dust.

[IsaacKuo]

I think your embryos etc would become strerile from expoosure to cosmic radiation. And I submit you will not get any radiation protection from some of the extraordinary radiation you will be exposed to on that journey. Your ship may coast to it's desination centuries from now.
It will have a cargo of dust.

Absolute nonsense. Cosmic radiation is not any stronger in interstellar space. There is no "extraordinary radiation".

You need about 5 tons per square meter of radiation shielding to reduce radiation levels down to sea level (note that there are people who live at high altitudes where exposure is much greater). The embryo banks could be worthy of 10 tons per square meter of cosmic radiation protection, which would reduce exposure down to practically zero.

[danscope]

So.... you think that you can build a ship with 6 tons of shielding plus the ships structure per square meter times .......
let's see: a ship 50 meters across and 500 meters long.......75,000 square meters.... times 3tons per sq meter....225,000 tons ; and that's just shielding, plus everything else, and you are going to accelerate this thing to 20,000 miles per hour.....yea 100,000 MPH?

Really? This thing makes Noah's ark weigh like a pingpong ball. Really. This would appear to be an insurmountable problem incapable of any real acceleration , even if you built it in orbit. And you might want to stop at the other end. Hmmm...

[theNater]

So.... you think that you can build a ship with 6 tons of shielding plus the ships structure per square meter times .......
let's see: a ship 50 meters across and 500 meters long.......75,000 square meters.... times 3tons per sq meter....225,000 tons ; and that's just shielding, plus everything else, and you are going to accelerate this thing to 20,000 miles per hour.....yea 100,000 MPH?

Really? This thing makes Noah's ark weigh like a pingpong ball. Really. This would appear to be an insurmountable problem incapable of any real acceleration , even if you built it in orbit. And you might want to stop at the other end. Hmmm...

You don't need much acceleration, you've got time. 100,000 MPH is about 44,704 meters per second. If you can swing an acceleration of just 0.001 meters per second per second, it takes 44,704,000 seconds to get up to speed. That's about a year and a half. Spending 18 months accelerating to start and another 18 decelerating at the destination isn't a major hindrance for a century long trip.

[IsaacKuo]

This would appear to be an insurmountable problem incapable of any real acceleration

Why, exactly? There is no magical physics limitation on acceleration just because something is very heavy.

[danscope]

It probably has something to do with " F U E L " . Rockets use this stuff in a big way.
In the real world, that is what makes things go.

[IsaacKuo]

It probably has something to do with " F U E L " . Rockets use this stuff in a big way.
In the real world, that is what makes things go.

And so what? Fuel requirements are linear with the payload mass. In no way does this imply a magical physics limitation on acceleration just because something is heavy.

[Murphy]

I think the point is that the shielding for Embryos or live passengers, doesn't need to be uniform across the entire vessel. For embryos you only need to shield a single room where they are stored, and that doesn't have to weigh much at all.

Anyway, any type of interstellar spacecraft capable of transporting all the equipment needed to set up a colony in a distant star system is going to be enormous, no matter what.

[danscope]

All we need are fuel tanks the size of Pennsylvania. That's all.

[theNater]

All we need are fuel tanks the size of Pennsylvania. That's all.

Which, while expensive, is not insurmountable.

[IsaacKuo]

All we need are fuel tanks the size of Pennsylvania. That's all.

Why so big? Maybe the size of Philadelphia, for a Manhattan-sized habitat.

[astromark]

Morally wrong on any level. "What did I do to deserve this ?" rebellion and mutiny a certainty. 'Take me home'...

The thought process is faulty. This topic has swept aside the OP... Odds of close contact... almost but not quite zero.

[danscope]

Yes..... I suppose it reflects the problems that some race on the "other end" will encounter if they should choose....amoung the countless billions of stars and galaxys..... to 'attempt' to travel 'amoung the stars' .
This concept is driven more by television and science fiction than by practical scientific application and anything approaching existing reality.
I should think that the fantastic concept is fun and a passing fancy for many, but it remains about as real as a 'magic carpet' .
Look: most of us enjoy....thoroughly enjoy...science fiction. And no one enjoys Robert Heinlein and Arthur C. Clarke more than I do.
It is entertaining and inspirational, to say the least. And we can point to many of the gifts of modern science which we enjoy as a direct spin-off of that body of work.
But the concept of accelerating large, massive vessels capable of supporting a mass of peoples and keeping them healthy and sane for
thousands of years in the blind faith of finding someplace somewhere that is just a teency bit like Earth that will support life as we know it
is just that. Fantasy. So.... when you talk about such things, at least be up-front about the basic tennents of the op. It is irrational to expect
a nation or bunch of nations to build a bonfire out of thousand dollar bills the height of the Empire State Building simply to sign the death warrants of several hundred people willing to die for science fiction.
It's one thing to preface a post with "Imagine if we could....." .
We have much to work at .... right here.
Earth, itself, is a space ship. Do you see ?

Well..... it shall be Father's day in a few hours. Thank you for suffering my humble opinion.
If you are going to talk about rocket science, you can expect the odd realist to show up now and again.

Best regards to everyone,
Dan

[astromark]

And well said Dan. I could not agree more. Stub this ridiculous idea out before some fool thinks its real.... It never can be.

In this forum we seem to be able to wonder away a little from the point as we have again here.

back in post 31 there was a comparison made with shipping... I like that line of thought as I have spent some months at sea.

Ask any one of the Apollo program astronauts what the isolation was like, going around the moon.

So the next step is to build survivable environments here on Earth., and then take us out of orbit... zoshhh...
>>>>> and off we go. Mark.

[A.DIM]

And well said Dan. I could not agree more. Stub this ridiculous idea out before some fool thinks its real.... It never can be.

"I believe the numbers work out in such a way that UFO's as interstellar vehicles is extremely unlikely, but I think it is an equally bad mistake to say that interstellar space flight is impossible." - Carl Sagan

"Who's the more foolish, the fool or the fool who follows him?"

[IsaacKuo]

The issue is not whether or not the idea is a "good" idea on moral grounds, but whether or not it is technically possible. Danscope claimed it was impossible, but then had to backtrack on that.

As it is, I don't favor the generation ship concept either. But I don't mind calculating out how to do it. Rather than erroneously claiming it's impossible, you need to use valid arguments.

As for whether or not "It never can be"...why not? Because isolation feels bad? That may or may not be an argument that it's not a good idea, but it's certainly not an argument of impossibility.

Because there will be a rebellion and mutiny? So what? The rebels will take over the mission whether they like it or not. The ship may have enough fuel to stop at the destination system, but it doesn't have enough fuel to turn around and stop at the source system (requires 3x as much fuel).

[danscope]

Like General Yeager said: " Spam in a can."

[IsaacKuo]

What is your point, and can you back it up with any valid argument?

[theNater]

Morally wrong on any level. "What did I do to deserve this ?" rebellion and mutiny a certainty. 'Take me home'...

The thought process is faulty. This topic has swept aside the OP... Odds of close contact... almost but not quite zero.

This topic is directly relevant to the OP, as danscope's claim seems to be that intelligent life cannot cross interstellar space. If danscope is correct in that assertion, then close contact is impossible.

However, interstellar travel is prohibited by financial, societal, and psychological factors, not by physics. As such, it is possible that, if we discover other intelligent life in the future, humans may launch an interstellar expedition to meet them. Similarly, if there is an extraterrestrial intelligence out there, it is possible that they have launched or will launch one headed here.

[danscope]

The argument is that human beings don't can very well.

[ravens_cry]

The argument is that human beings don't can very well.

Then take humans out of the loop. Include a AI to run the ship, while the spam snoozes on ice the trip away.

[IsaacKuo]

The argument is that human beings don't can very well.

Humans have been put in prison or exiled to islands for life. Do they like it? No. Is it an insurmountable problem? Of course not.

Besides, a typical proposal for a generation ship would be to use a large habitat the size of Manhattan or so. Plenty of people have lived their entire lives in an area that "small".

[Hlafordlaes]

OTOH, what alternatives to generation ships exist for avoiding species extinction when the local star reaches the end of its life cycle? I think we may find the center of the Milky Way a likely destination for farming energy and/or matter to supply such ships, attracting wayfarers from across the galaxy. We may yet meet a few in another couple of billion years when our turn to wander comes up.

[IsaacKuo]

OTOH, what alternatives to generation ships exist for avoiding species extinction when the local star reaches the end of its life cycle?

The option I like is "fast" interstellar ships. You don't need "generation" ships if your starships can travel between star systems within a decade or two. There are a number of possible methods for implementing such "fast" starships--my favorite method is a technique I call double stream propulsion. It involves streams of relativistic sailbots which are initially accelerated by long range x-ray lasers.

There are other options, also.

One option is to cling onto the original star system, and use gravitational potential energy to power a (severely reduced) civilization after the home star dies and becomes a white dwarf. It may be possible to survive for many billions of years after the star's "death", before it's absolutely necessary to move on.

Another option is slow outward colonization. Oort cloud objects have orbital periods on the order of a million years, so it would take on the order of millions of years to colonize the Oort cloud by expanding from object to object. Power for an "oort cloud" civilization could come from fusion power, if it's possible, or it can be beamed from the home star system. As the solar system orbits around the galaxy, its oort cloud actually intersects the oort cloud of other star systems. As such, "slow" colonization could actually expand from star system to star system without ever actually doing any long range colonization missions.

[Noclevername]

Actually, if my calculations are correct the odds of rolling a 1 with a die fifteen times in a row is 1 in 470184984576. Just sayin.

That assumes unloaded dice, which has not been established.