Generation Ships: Would You Go On One?

[wolram]

I have just been reading this https://arxiv.org/pdf/1901.09542.pdf It makes me wonder if anyone would go on a generation ship, What about you? I would not.

 

[stefan r]

Planet Earth is a type of generation ship. It's course is set for orbit around the Sun. It is the act of leaving one that is debatable.

Before moving to any specific ship (or city, or country) I would want to know the conditions of the place I was moving too. The conditions/circumstances at my current home would also be a major factor. I have no current plans to move away from the Eastern USA. If I have a choice I would not move to Guatemala or Idaho. I could definitely think of scenarios where I could be convinced to move to Idaho.
When I was young and unmarried a ship full of attractive young coeds who are intending to breed would have been very appealing. The consequences of not being able to get out may not have been enough of a deterrence. Being a male minority in a floating garden has some fantasy potential. I think there would be serious competition to get onboard.

 

[Janus]

By the time we ever were to get around to launching a generation ship, we are likely already going to have a fairly large number of people living in space. You are going to want to make sure that a bio-system can be maintained for a sustained period. Orbital space colonies would be a way of doing gaining the practical experience of doing so and uncovering the pitfalls. By launch time you will have a subset of the human population for which moving onto a generation ship would not be all that different from the life they already lead.

 

[ohwilleke]

FWIW, I think that the article's estimates are very optimistic. It doesn't leave much slack for disruptions or disasters en route over hundreds of years and even if 500 people are enough to maintain genetic diversity in the face of inbreeding, this isn't a big enough population to maintain the body of knowledge and skills and experience necessary to maintain an advanced civilization for multiple generations.

 

[phinds]

I have just been reading this https://arxiv.org/pdf/1901.09542.pdf It makes me wonder if anyone would go on a generation ship, What about you? I would not.

Since it's not going to happen in our lifetimes, who cares? Let our great, great, great ... great grandchildren worry about it.

 

[anorlunda]

Consider four options.

1. Make a generation ship massing ? tons. It will take a large fraction of the world's resources to build it and launch it. It has a chance of establishing a human society on another planet a few thousand years from the date of launch. Today's voters, and their cultures will be long dead and buried by then.
2. Make a ship massing 1 kg containing zygotes, seeds and incubators. It is a low budget thing. It has a chance of establishing a human society on another planet a few million years from the date of launch. Today's voters, and their cultures will be long dead and forgotten by then.
3. Wait an indefinite time until we have the technology to beam Earth to other star systems or to beam Mars and Venus to more favorable orbits.
4. Do nothing.

Which do you think the citizens of Earth will vote for?

 

[ohwilleke]

Since it's not going to happen in our lifetimes, who cares? Let our great, great, great ... great grandchildren worry about it.

A generation ship is also a thought experiment that requires thinking about human society and its ecology as a closed system like the real generation ship which is planet earth, and by thinking about it we consider the vulnerabilities facing our species in terms of long term survival.

 

[phinds]

A generation ship is also a thought experiment that requires thinking about human society and its ecology as a closed system like the real generation ship which is planet earth, and by thinking about it we consider the vulnerabilities facing our species in terms of long term survival.

Perhaps, but that was not the point of the quoted article that started this thread. If you want to talk about / think about Earth as a closed system, fine, but why not do so directly instead of bringing in some indirect mechanism?

 

[DaveC426913]

Planet Earth is a type of generation ship. It's course is set for orbit around the Sun.

As the risk of derailment, I would argue this is not so.
Earth is highly dependent on the Sun for its energy.
Nevermind the issue about a "ship that cannot move", the point is that the erstwhile Earthship's power source is external - and fixed.

 

[stefan r]

As the risk of derailment, I would argue this is not so.
Earth is highly dependent on the Sun for its energy.
Nevermind the issue about a "ship that cannot move", the point is that the erstwhile Earthship's power source is external - and fixed.

I did not see a power source listed in the article. Columbus crossed the Atlantic using an external power source (wind). I thought that was on "3 ships".

Is there a precise definition of "generation ship"? I assumed the only qualifying trait was that the crew died and were replaced by at least one new generation while on the mission. So, for instance, you could have generation ships scavenging the Oort cloud. You can escape the Sun's gravity using gravity assists. Large mirrors can concentrate sunlight.

We could have laser highways strung across the galaxy. (very distant future) The highway posts would need to be generation ships themselves or fully automated AI. A [craft?] traveling the route would be accelerated by external lasers or particle beams. It is externally powered. They may be highly dependent on the sun (or a star) for power. Is such a thing "not a ship"?

Breakthrough starshot claims to be near future. Each probe is accelerated by a fixed external power source. They would be decelerated by Alpha Centauri. The probes would be microchips not generation ships but what if it was scaled up.

 

[phinds]

I did not see a power source listed in the article. Columbus crossed the Atlantic using an external power source (wind). I thought that was on "3 ships".

And you think there would be wind without the energy from the sun? Really?

 

[stefan r]

And you think there would be wind without the energy from the sun? Really?

No, the post from Dave is the first time I have seen someone claim that ships needed to be internally powered. I see nothing wrong with a solar powered ship. We can call Earth a solar boat or solar raft.

I am not completely clear on the difference between boats and ships either. The U.S. Navy has some sort of pride thing between being captain of a ship vs being captain of a boat.

I would not want to be confined to a prison cell and eat only yams for the few years I suffer from slow death by radiation poison.
Living in a spacious garden with grapes, olive trees, bees, wildflowers, and a sizeable harem sounds very appealing. Call it a ship, boat, raft, tub, can, I do not care much.

 

[phinds]

I am not completely clear on the difference between boats and ships either.

A boat is something you can carry on a ship. That's why they are called lifeboats, not lifeships.

 

[Rive]

...It will take a large fraction of the world's resources to build it...

Considering the technology level required for building it I think it is safe to replace that 'world' with 'solar system' instead. And that's a lot of resource.
I think it's just that type of question which will be just trivial once the technology and the background is available: but before that it is too big for even a dream.

 

[ohwilleke]

Perhaps, but that was not the point of the quoted article that started this thread. If you want to talk about / think about Earth as a closed system, fine, but why not do so directly instead of bringing in some indirect mechanism?

The same reason the physicist starts off modeling spherical cows. It is more tractable to deal with.

 

[phinds]

The same reason the physicist starts off modeling spherical cows. It is more tractable to deal with.

A reasonable point

 

[jrmichler]

Being a male minority in a floating garden has some fantasy potential.

Fantasy, yes. The reality is that they will gang up on the men. I once went on a canoe trip with three women, so have some practical experience with this.

 

[russ_watters]

No, the post from Dave is the first time I have seen someone claim that ships needed to be internally powered. I see nothing wrong with a solar powered ship. We can call Earth a solar boat or solar raft.

I didn't read the whole discussion, but to me the relevant factor is the voyage, not what you call the vehicle. An interstellar ship is unlike Earth in that it cannot be externally powered. That may have been @DaveC426913 's point.

It's also large enough that we don't have good/direct control over its systems. So I'm not sure it tells us much of value.

 

[Al_]

I suspect that Janus is right - by that time living in "ships" or habitats will be considered preferable to life on a planet, and they will make long trips between Kuiper belt objects to gather resources. In that scenario, a generation ship is not so far from what is already common.

 

[jrmichler]

I have had idle thoughts at various times on the general subject of space habitats and starships, where a starship is a space habitat with a propulsion system. My thoughts tend to such dull, boring, practical realities as:

1) Atmosphere. The generation ship in the OP's referenced paper is 448 m diameter by 320 m long. At STP, the atmosphere masses 62,000,000 kg. Air under pressure is always trying to leak out. There is not such thing as 100% perfect seals, nor is there any way to 100% guarantee zero accidents causing air to leak out. A leak rate of 0.1% per year would require spare air inventory of 62,000,000 kg plus reserves for a 1000 year mission. I found one reference stating that the leak rate of the ISS is 1% per month, or 12.7% per year. A generation ship will have a lower leak rate because it will have a higher volume of air per square meter of pressure hull, but still...

2) Same calculation for water. And every other consumable. Don't forget nuclear reactor fuel.

3) Since few electronics last more than 20 years, it is necessary to have the capability of manufacturing replacements for every single part on board the ship. That includes the most complex microprocessor, and especially the machine that manufactures that spare microprocessor. Nothing is discarded, everything is recycled right down to the atomic level.

I have never tried to estimate the sum total of consumables needed for a generation ship, but suspect that passenger and life support volume would be a small fraction of the total volume.

 

[gmax137]

The linked paper, and its references, are talking about a 6300 year trip. Think about that. 6300 years ago (4281 BC) was 1700 years before the Cheops pyramid was built. And the pyramid is looking a little ratty today. You can't expect any machine to operate for six thousand years. Much less an isolated device that must be self sufficient.

Also, if the generation ship crew ever arrives at Proxima Centauri, after a 6300 year trip, I would expect them to be greeted by the descendants of the (much) faster ships who left earth, say, 4000 years later.

 

[phinds]

Also, if the generation ship crew ever arrives at Proxima Centauri, after a 6300 year trip, I would expect them to be greeted by the descendants of the (much) faster ships who left earth, say, 4000 years later.

I vaguely recall a couple of science fiction stories that use that as their central premise.

 

[russ_watters]

Also, if the generation ship crew ever arrives at Proxima Centauri, after a 6300 year trip, I would expect them to be greeted by the descendants of the (much) faster ships who left earth, say, 4000 years later.

Well that's rude!

 

[Janus]

The linked paper, and its references, are talking about a 6300 year trip. Think about that. 6300 years ago (4281 BC) was 1700 years before the Cheops pyramid was built. And the pyramid is looking a little ratty today. You can't expect any machine to operate for six thousand years. Much less an isolated device that must be self sufficient.

Also, if the generation ship crew ever arrives at Proxima Centauri, after a 6300 year trip, I would expect them to be greeted by the descendants of the (much) faster ships who left earth, say, 4000 years later.

That's the conundrum of slow interstellar travel. Do you launch now and have the trip take 6000 yrs, or do wait 100 yrs until your propulsion methods have improved enough to reduce the trip time to 5500 yrs, getting you there 400 yrs earlier? At what point can you assume that further propulsion improvements won't allow a later launched ship to beat a earlier launched ship?

 

[DaveC426913]

That's the conundrum of slow interstellar travel. Do you launch now and have the trip take 6000 yrs, or do wait 100 yrs until your propulsion methods have improved enough to reduce the trip time to 5500 yrs, getting you there 400 yrs earlier? At what point can you assume that further propulsion improvements won't allow a later launched ship to beat a earlier launched ship?

It's only a conundrum if one posits the creation of the ship in a vacuum of motive. i.e. that you have a choice of when to launch.

Such ships are so fabulously expensive in resources and effort that, generally, the few motives that are strong enough to start them are things that drive people off Earth to save their lives* - such as overpopulation, ecological collapse, or other disaster that makes life on Earth untenable.

In such cases, the issue of how soon you can arrive is irrelevant; the only issue is how soon you can leave.* speculation of course, but so is the conundrum

 

[phinds]

Well that's rude!

More like embarrassing, I think

 

[stefan r]

...

1) Atmosphere. The generation ship in the OP's referenced paper is 448 m diameter by 320 m long. ...

The 448 diameter was there assuming that you need 1 g. The volume only needs 3m height per deck unless you are bringing giraffes. With 8 decks the top floor is in the 0.9g area. You could grow yams on a shorter deck too.

... Air under pressure is always trying to leak out. There is not such thing as 100% perfect seals, nor is there any way to 100% guarantee zero accidents causing air to leak out. A leak rate of 0.1% per year would require ...

I think we would want several outer decks that are under vacuum and at cold temperature. The outer decks may not need to be rotating. If the temperature is below freezing temperature the leak rate is much lower. At 37K the vapor pressure of nitrogen is 1 pascal.