Closed Systems, Entropy, and long duration spaceflight(non-cyrogenic)

[OrtSurfer]

Aside from interstellar radiation, micro-meteors, and other things I know nothing about... plus the fact that we don't have the tech to accomplish the things im about to propose...

Is it actually possible to maintain generations of population (with very strict breeding laws of course) during a long, interstellar space flight. Moreover, what are the problems that would have to be solved in order to be possible?

First I see the absolute necessities: Food, Water, Oxygen.

FOOD: After finding the right ratio of plant life to human population to sustain at least (pull from a hat) 30 years, using waste to maintain fertilized and watered soil, what would be some long term problems?

I imagine that if the right proportion was found, you could go for quite some time. But eventually, wouldn't some mass (nutrients/sugars/and so on) be lost from the amount of heat produced by the human body? Thus defining a true limit on how long homeostasis could be maintained?

WATER: I think the same problem from food could be applied here. That at some point in bodily process, water is converted into heat or another form of mass that would be eventually loss to producing body heat.

OXYGEN: While CO2 scrubbers have been invented, they only work for so long. An alternative to using scrubbers would be massive algae farms on board (I read some where that algae is an important part of oxygen production on earth). But since there is no gravity in interstellar space (to speak of), how would air flow be regulated to into the farms? A certain amount of surface area is needed to provide a human with enough oxygen, but when surfaces are no longer guided by gravity, how might that effect oxygen production? Perhaps an artificial gravity wheel could aide in this.


Anyways, trying to make a long point short now... Wouldn't an unsustainable amount of mass eventually be converted into heat and be lost forever? Is there anyway to convert that energy back into mass?

 

[statickid]

any spacecraft is not truly a closed system unless it had totally perfect seal, insulation, and vacuum barrier, perfect radiation shield, and no contact with any of the structures that provide all of those properties. The spacecraft can collect stellar energy, collect free floating particles, vent heat with radiators, collect heat, etc... so the idea of entropy affecting a spacecraft as a closed system is faulty.

also the human body does not convert matter into energy to create heat, it uses exothermic chemical reactions

 

[paddy2]

I would suggest you would only need one thing / item / chemical to be out of balance and given the time span, a very slow but final problem would loom.

In the old day we could pull up sticks and move to the next valley!

What about taking 4 ships and always leaving one fallow like in the old crop rotation farming system.

 

[T.Neo]

also the human body does not convert matter into energy to create heat, it uses exothermic chemical reactions

Don't those involve a minute amount of mass being converted to energy?

 

[jedidia]

With current technology, you will already hit a bumper with the ecosystem. We have so far failed to create a closed, self-sustaining one even experimenting here on earth, much less aboard a spacecraft. Although that obstacle could probably be overcome relatively quickly if more research was put into it.

 

[Artlav]

At some point you would have to overcome material entropic decay - stuff just diffusing around in a way that can no longer be effectively extracted - oxygen getting absorbed into the walls, locked into hundreds of various components among the soil and machinery, trace elements being lost, and so on.

The only bulletproof way of dealing with that would be energy-matter conversion, to just make whatever atoms you need from any other atoms.
But with tech like that you could just build a total conversion drive, and fly to your destination in under a year ship time.

However, this might take centuries in a well designed system.
True entropic decay won't be a problem - you just dump the heat overboard.

Then, you have to prevent cultural decay among the crew - children have to be taught everything, not just which buttons to press.
Boredom handling is a problem as well - in a bulb mere cubic kilometres of volume there isn't much to do after a while.

There have to be some serious fabbers on board, and a supply of all the materials for them, to allow any damage to be fixed.

Lastly, there should be externally accessible docking ports, so that when back on Earth they would invent a warp drive, the would-be-colonists-still-on-the-way could easily be "rescued".

 

[Ark]

I would think the social and psychological problems would get you long before basic entropy and systems breakdown do. You wanna be the one to tell the kids they don't get to have any purpose in their lives other than to make more kids so they can be the ones to colonize Earth II? That they're doomed to live and die in the same crappy metal tube in space?

Don't come crying to me when they decide that reality is false, everyone is really trapped in a sim tank in Gunnison, CO and the only escape is to rip open the hull paneling.

 

[ADSWNJ]

You wanna be the one to tell the kids they don't get to have any purpose in their lives other than to make more kids so they can be the ones to colonize Earth II?

They would live Orbiter 24x7, and sneak away to use Real Life simulators when they get a chance.

No wait - that's us, isn't it?

---------- Post added at 11:37 AM ---------- Previous post was at 11:32 AM ----------

That at some point in bodily process, water is converted into heat

Einstein would be impressed! Humankind becoming nuclear reactors, E=mc2 style!

 

[statickid]

Don't those involve a minute amount of mass being converted to energy?

are you suggesting that every time an exothermic reaction occurs the atomic weight of the molecule is diminishing?

and that the rate at which this occurs is of a scale that will compromise a long duration (human perceived) spaceflight?

 

[Urwumpe]

are you suggesting that every time an exothermic reaction occurs the atomic weight of the molecule is diminishing?

Yes. E=mc² does even apply to HDDs (magnetic mediums get lighter, when they are formatted)

and that the rate at which this occurs is of a scale that will compromise a long duration (human perceived) spaceflight?

Well, theory aside, yes, you will get direct problems from thermodynamic aspects even after a very short time. Energy will get lost, reactions will require much more energy for being reverted, than you gained by it, other reactions will end in deadends - only very high energy use could turn them into something useful, and you could not control, what you get as result.

And then there is also radiation in space, which will corrode things. Mechanic parts will wear down and leave tiny bits of metal dust that you can't recycle.

 

[statickid]

then it follows that you are also implying that this degradation of matter is the principal source of the energy released by bodily chemical reactions and not orbital state changes

 

[Urwumpe]

then it follows that you are also implying that this degradation of matter is the principal source of the energy released by bodily chemical reactions and not orbital state changes

There is no source of energy. Yes, that term is usually used when handling practical problems. But in theory, as we are now, energy is neither created nor destroyed. And even the energy that you put into structuring matter is not created or destroyed as well, it is bound in the structure. Changing the structure absorbs or releases energy.

(It can be easily understood that constructing a building requires energy, while letting it collapse releases energy, but it releases of course less energy than needed for constructing it )

Now, with that in mind, what do you think, is a orbital state change?

 

[T.Neo]

This states that human heat output power is 70-870 watts. Assuming that the average is something like 150 watts, that's 0.72 MJ in an hour, 17.3 MJ in a day, 6.3 GJ in a year, and 442 GJ over 70 years.

My feeble math skills give a value of 5 milligrams of mass converted to energy over 70 years. For 10 000 people on a 400 year trip, it's something like a third of a kilogram. Considering that 10 000 people could weigh something like 700 tons and eat 20 tons of food a day, this amount of mass is likely inconsequential.

 

[Pablo49]

Don't come crying to me when they decide that reality is false

"I hope life on Earth is everything you remember it to be." -GERTY

 

[statickid]

i think the OP is seeking clarification on how thermodynamic laws affect the spacecraft, suggesting it is a closed system and that the integrity of the crafts matter itself will be of concern.

however, the spacecraft is not a closed system by the relevant definition.

I would say the spacecraft is an extremely limited ecosystem whose major concerns are resource recycling, biodiversity, and psychological integrity.

Its easy to say that the underlying reason for these systems falling apart is due to the spacecraft's improbable existence becoming homogenized; it's just not very useful to look at it this way, IMO.

 

[OrtSurfer]

I know that my use of Entropy and closed system is wrong. What I was trying to get at was no resupply operations.



As for the problem of psychological integrity, that brings me memories of a movie I saw once, called Pandorum.

Pandorum being a psychological illness that caused a captain to go insane (for an unspecific reason) and launch most of the population (which where in cryotanks) into outerspace, en route to a planet capable of supporting human life.

Also Forms of mutation ensued, ship degradation, and finally at the end of the movie (spoiler alert) they were at the bottom of Earth II's ocean the whole time!


Speaking of mutations, how many generations are necessary to negate the effects of incest or to avoid it all together? Like 3rd or 4th cousins, perhaps?

Any biologists in vicinity? :lol: