Inhabitable Planets Too Close Together?

swalke813 wrote:One issue people forget about those cryogenic ships is that the ship itself wasn't preserved. Material ages, even with the best designs. And that is an issue that won't likely change. Even in the Honorverse, they are clearly ships removed from service due to age. An age measured in decades, but still there. And ALL the ships need regular maintenance.
And don't get me started on the likelihood of a computer running that long, hundreds of years, without locking up. I can see Microsoft bidding on that contract. "Hell, but hell no!"


The likelihood of a sleeper ship or generational ship is nill. It would more likely reach its destination as nothing but an odd asteroid with a dead cargo.

No, maybe 1 in 10 or 1 in 50 will end up as dead ships, but it´s extremely unlikely to happen because of computers locking up.

Even with Microsoft and Windows, well lets say it like this, I know people who has kept old Windows machines running without breaks for both 10(-XP ), 15(-98 ) and 20( DOS-6.2 ) years.
With standard commercial hardware and software.

And in a sleeper ship, you´re NOT going to use standard commercial hardware or software!

Do recall early space probes, THEY still work after decades of time in space.

There´s a lot that can go wrong, but it´s fairly easy to set up redundancy for them.

Even today, it´s not hard to build a spaceship capable of surviving a few centuries. It´s EXPENSIVE, but not really difficult.

Tenshinai wrote:Even with Microsoft and Windows, well lets say it like this, I know people who has kept old Windows machines running without breaks for both 10(-XP ), 15(-98 ) and 20( DOS-6.2 ) years.

And for mission-critical systems, you'll use *nix anyway.

Probably a lot of stuff will have all executable code stored in solid-state devices like SD cards that you can physically write-protect by flipping the tab, etc. You'll have extras that are locked away until you need them, with protocols that require two different people to unlock the access panel to even be able to change them out, and the firmware will refuse to load code that isn't signed by the right key.

Plus you'll have a lot of redundancy in the systems to allow any individual computer to fail and others seamlessly take over.

Also, you'll have fabrication facilities to allow replacement computers to be built as others age. You're going to need to be able to build things once you get to your destination, so the fabs need to be working all the way there.


Lastly, when it comes to the durability of the ship, the logical design for a generation ship is to hollow out an asteroid, leaving a large amount of rock as a shield against impacts along the way. It will have to be able to deploy "periscopes" (two or three at a time out of dozens ready to deploy in the event the originals get knocked out) out the aft end that extends sideways to look forward.

And for mission-critical systems, you'll use *nix anyway.

Or something else that you KNOW how it works.

Still though, the machines i mentioned were kept running like that exactly because they were missioncritical, and the software only existed as windows programs.

Also, you'll have fabrication facilities to allow replacement computers to be built as others age. You're going to need to be able to build things once you get to your destination, so the fabs need to be working all the way there.

Yup. And remember that what is commercially a good idea isn´t what would be used either.
If we take a common cpu of today, it might have a life expectancy of ~10 years, but if we take the same production ability and change it to make something optimised for longevity?

Heh, even just turning the clockrate and voltage down drastically on real modern cpu can up it´s life expectancy several times over even if we´re seriously pessimistic about it.

With some good selection of parts, even with stock commercial stuff you can probably put together a computer that can run fine for the next 50 years at the minimum.

leaving a large amount of rock as a shield against impacts along the way.

And cosmic radiation unless that issue has been solved some other way.

Lastly, when it comes to the durability of the ship, the logical design for a generation ship is to hollow out an asteroid

Not necessarily, that would depend on what kind of engines are possible, the amount of extra mass added by an asteroid is IMMENSE, and may cut acceleration to a tiny fraction of what is otherwise possible. And the speed lost is far more valuable in this case.

It´s much easier to build something.

Just to put the discussion in perspective, here is a link to a snippet on Polynesian Voyaging Canoes. These Neolithic people were voyaging thousands of miles across the Pacific between small islands in what were little more than dug out canoes at a time when the Europeans who afraid to get out of sight of land while paddling around in the Mediterranean wading pool.

http://pvs.kcc.hawaii.edu/ike/hookele/o ... nding.html

I think that if we can figure out how to build the propulsion systems to take usto the stars, we can figure out how to build computers and auxiliary systems that can function reliably for decades or centuries. Comparison to modern consumer electronics that are intentionally designed for planned obsolescence is not valid.

To get back to an earlier subtopic in this topic, Ars Technica just posted a review of an article on why Earth has plate tectonics while Venus doesn't. There's a fair amount of speculation that plate tectonics are a prerequisite for life as we know it.

http://arstechnica.com/science/2014/04/ ... tectonics/

A few weeks ago there was also a story about an asteroid impact that was a lot bigger than the one that marked the end of the dinosaurs; it gave what's now present-day South Africa a mighty wallop and possibly started the plate tectonic conveyer.

The take-home here is that the so-called "habitable zone" could be a lot smaller than we think, which has implications for what proportion of systems have a habitable planet.

JohnRoth wrote:To get back to an earlier subtopic in this topic, Ars Technica just posted a review of an article on why Earth has plate tectonics while Venus doesn't. There's a fair amount of speculation that plate tectonics are a prerequisite for life as we know it.

http://arstechnica.com/science/2014/04/ ... tectonics/

A few weeks ago there was also a story about an asteroid impact that was a lot bigger than the one that marked the end of the dinosaurs; it gave what's now present-day South Africa a mighty wallop and possibly started the plate tectonic conveyer.

The take-home here is that the so-called "habitable zone" could be a lot smaller than we think, which has implications for what proportion of systems have a habitable planet.

Technically, that does not affect the size of the "habitable zone". But we take your underlying point--it would instead affect the probability that a planet in the habitable zone actually produces life.

Yes, we have finally proven that planets in the habitable zone will be numerous in the galaxy (despite the unexpected discovery of giant planet migration). What we still don't know is what other factors are important for the development of organic life. Another factor that is sometimes suggested as important is the presence of tides. A few papers have proposed that a large moon may be important for early life, on the theory that life may have developed in tidal pools. Interestingly, a large moon is also useful for generating plate tectonics.

But we don't really know. Other papers have suggested that life will be nearly ubiquitous wherever there is enough ambient energy, liquid water, and organic ingredients.

Thank you everybody. I love this Forum! My first thinking was that as we learn more and more about what may be inhabitable planets, the more we understand that everything must be darn near perfect for even genetically modified people and things to survive, live and multiply there. Thus my default mode considering that such suitable planets may in fact be very scarce and hard to find ... thus the much greater distances involved. My read only and thank you. HB of CJ (old coot)

HB of CJ wrote:Thank you everybody. I love this Forum! My first thinking was that as we learn more and more about what may be inhabitable planets, the more we understand that everything must be darn near perfect for even genetically modified people and things to survive, live and multiply there. Thus my default mode considering that such suitable planets may in fact be very scarce and hard to find ... thus the much greater distances involved. My read only and thank you. HB of CJ (old coot)

You have a good point there, in that most modern life requires a fairly specific conditions. But it turns out that some of those conditions are produced by life. There is a hypothesis (called the Gaia Hypothesis) that life helps promote and generate better conditions for itself. This includes things like gas composition, pressure, temperature regulation, and soil. It is clear that life has altered the chemistry of the atmosphere and oceans, for instance. The early conditions under which life first developed were quite toxic and extreme compared to today. So, the extreme version of the Gaia Hypothesis is that life can develop in remarkably extreme conditions, and as life becomes more complex, it will produce conditions more suitable for even more complex life.

Making a soup can ship with a nuclear fission powerplant and ion engine is not overly hard. Expensive in our schemea but not overly hard. Add counter grav and the price drops rapidly. A ship 1-2 km in diameter, 10+ km long with a pod nuclear reactor / ion drive engine at one end. The further away from the habitable "soup can" the less shielding required. Still needs "dirt" several hundred metre thick shielding plus the externally armoured skin. Concrete clad in steel would be great.

Guns mounted in compartments with turrets for shooting obstacles, although a laser moving "tractor beam" plus a big spinal mount mass projector for nudging things out of the way. No one needs weapons to shoot anyone else, yet. Microwave transmitters to power remote things is more likely. Again. Nuclear power gives a long duration power source. An ion drive that can focus emissions is a simple long duration "engine". Big enough for long duration and with options with initial small populations and room to grow.