Generation vs Colony vs Cryo

penny wrote:3D printers are not magic bullets. A 3D printer needs building blocks. The building blocks of a 3D printer are the materials. The materials have to be mined for. Either on planet or in space. For sake of simplicity, let's say that the materials of an HV 3D printer are akin to the ink of present day inkjet printers. Have you ever known an inkjet printer to be worth a damn without any ink? And the ink is specialized for high tech models. They use ink from a "cartridge." This cartridge has to be ordered from a specialty store. Or in our case, made from specific materials that have to be mined. Either in space or on the planet. A generation ship is ever moving. It is impossible to mine for everything while literally on the fly. The ship has to come to a full stop to mine for some materials. And if you fail to pack enough of that material initially, then the overall plan begins to go off the rails. It is impossible to plan for the unseen, the [un]experienced, the unexpected, the unanticipated and the unleashed. And when we run out of ink, we can't make any more Philip heads. And the damn ship didn't leave us one. We could jury rig a solution in a pinch. But we don't have any duct tape. The duct tape is in the tool box too. Right beside the Philips head.

penny wrote:But I do not agree that colonizing the planet should be put on hold after arriving. And if the planet is being settled, I do not agree with mining for water in space for the colonists when a ready source of clean, naturally filtered fresh water is available on the planet. Mining for water in space for the space population, yes, but not for the population groundside.

ThinksMarkedly wrote:Everything in that list should be recyclable. It's just a matter of effort and energy expenditure.

penny wrote:For the most part, I agree. However, recycling water is never going to be a 100 % efficient process. If a gallon of water is consumed, we will not get a gallon of water back in urine. The body needs some of the water for itself. The body will lose some in cooling itself off, sweat. We shed tears, etc.

The same with cooking. Foods absorb water while cooking. Plants need water for photosynthesis. 100 % will not be reclaimed.

I don't think it makes sense to recycle water that is utilized for tools and manufacturing because that water becomes contaminated with hydrocarbons and a host of other pollutants which require advanced filtration systems. But let me clarify that statement. I agree that even that water can be recycled. But not for consumption. It should be recycled for further use in manufacturing.

The water for radiation shielding cannot be recycled for drinking as it already has a critical use.

Whatever the manufacturing process is (whether 3D printer or something more primitive), there will be a need for some manufacturing in flight. Since raw materials cannot be acquired in flight, there will be a need for some stored raw materials on board to make up for things that cannot be immediately recycled. I think most everyday items could be made from stainless steel or glass, both of which lend themselves to recycling (glass having been recycled through almost all of its existence). But there will also be a need to rebuild electronics and other more complicated items.

In a closed system, water is not lost and can be completely recycled. Whatever is not eliminated through digestion, will eventually emerge as respiration or sweat. There is a retention period in plant or animal cells, but eventually those break down also. Even today there are processes that can cleanly recycle water with industrial contaminates.

I do not think anyone in the forum has suggested getting water for planetary colonists from space. That might only be needed for some place like Mars, but I would hope most planets planned for colonization would have available surface water. So it would also need a magnetic field to protect against erosion from the stellar winds.

tlb wrote:

penny wrote:3D printers are not magic bullets. A 3D printer needs building blocks. The building blocks of a 3D printer are the materials. The materials have to be mined for. Either on planet or in space. For sake of simplicity, let's say that the materials of an HV 3D printer are akin to the ink of present day inkjet printers. Have you ever known an inkjet printer to be worth a damn without any ink? And the ink is specialized for high tech models. They use ink from a "cartridge." This cartridge has to be ordered from a specialty store. Or in our case, made from specific materials that have to be mined. Either in space or on the planet. A generation ship is ever moving. It is impossible to mine for everything while literally on the fly. The ship has to come to a full stop to mine for some materials. And if you fail to pack enough of that material initially, then the overall plan begins to go off the rails. It is impossible to plan for the unseen, the [un]experienced, the unexpected, the unanticipated and the unleashed. And when we run out of ink, we can't make any more Philip heads. And the damn ship didn't leave us one. We could jury rig a solution in a pinch. But we don't have any duct tape. The duct tape is in the tool box too. Right beside the Philips head.

penny wrote:But I do not agree that colonizing the planet should be put on hold after arriving. And if the planet is being settled, I do not agree with mining for water in space for the colonists when a ready source of clean, naturally filtered fresh water is available on the planet. Mining for water in space for the space population, yes, but not for the population groundside.

ThinksMarkedly wrote:Everything in that list should be recyclable. It's just a matter of effort and energy expenditure.

penny wrote:For the most part, I agree. However, recycling water is never going to be a 100 % efficient process. If a gallon of water is consumed, we will not get a gallon of water back in urine. The body needs some of the water for itself. The body will lose some in cooling itself off, sweat. We shed tears, etc.

The same with cooking. Foods absorb water while cooking. Plants need water for photosynthesis. 100 % will not be reclaimed.

I don't think it makes sense to recycle water that is utilized for tools and manufacturing because that water becomes contaminated with hydrocarbons and a host of other pollutants which require advanced filtration systems. But let me clarify that statement. I agree that even that water can be recycled. But not for consumption. It should be recycled for further use in manufacturing.

The water for radiation shielding cannot be recycled for drinking as it already has a critical use.

Whatever the manufacturing process is (whether 3D printer or something more primitive), there will be a need for some manufacturing in flight. Since raw materials cannot be acquired in flight, there will be a need for some stored raw materials on board to make up for things that cannot be immediately recycled. I think most everyday items could be made from stainless steel or glass, both of which lend themselves to recycling (glass having been recycled through almost all of its existence). But there will also be a need to rebuild electronics and other more complicated items.

In a closed system, water is not lost and can be completely recycled. Whatever is not eliminated through digestion, will eventually emerge as respiration or sweat. There is a retention period in plant or animal cells, but eventually those break down also. Even today there are processes that can cleanly recycle water with industrial contaminates.

I do not think anyone in the forum has suggested getting water for planetary colonists from space. That might only be needed for some place like Mars, but I would hope most planets planned for colonization would have available surface water. So it would also need a magnetic field to protect against erosion from the stellar winds.

If the ship is sealed, all water is recycled. Some comes out of air conditioners rather than other systems. One reasonably packs a minimum of a couple of tons of each element, as reserves. The properly designed interstellar 3D printer does not need fancy ink bottles as inputs, any more than current 3D printers do.

penny wrote:For the most part, I agree. However, recycling water is never going to be a 100 % efficient process. If a gallon of water is consumed, we will not get a gallon of water back in urine. The body needs some of the water for itself. The body will lose some in cooling itself off, sweat. We shed tears, etc.

See answers above about a closed system and making water potable again. There may be some water lost through outgassing to space, but it should be minimal and negligible even over centuries. And even if it isn't, getting some more water from some comets in the destination system is easy. Where do you think those ships would get their water in the first place in the Sol system? Hint: it's not going to be by lifting out of the deepest gravity wells.

PS: I understand what you meant, but you did not mean "100% efficient." Nothing is 100% efficient due to the Second Law of Thermodynamics.

The water for radiation shielding cannot be recycled for drinking as it already has a critical use.

Radiation shielding is a matter of probability. The thicker or denser your layer of matter, the higher the probability that radiation will be stopped. So you will have a lot of water in those tanks.

I agree you can't diminish it by constantly dumping water overboard. But outside of some small outgassing and minor losses due to imperfections, the only thing that the ship would be throwing overboard would be reaction mass, and in cruise that's going to be very minimal. They need to have a lot of hydrogen to use for deceleration, so if that came from the water tanks after electrolysis, you're left with a lot of oxygen. Add hydrogen again and you've got water.

And we're told ships as ancient as Calvin's Hope had the ability to replenish fuel (hydrogen) from the Calvin System.

So the ship should be running with full water tanks practically all the time. Since it's a closed system, you take water out of them and add water back in. And if there's any water you can't treat, al you need is to keep it segregated from water you can still use.

I certainly agree. Generation ships should be able to produce water, I am just not sure at what rate of production. There are science fiction stories that deal with this utilizing current technology. The Mars Trilogy comes to mind.

We may not have the technology for this now, but we have line of sight to everything we need to build an interstellar generation colony ship. It requires no new science and no new materials, just application of what we know. And money, lots of it.

The one thing we really would benefit from is fusion power. But even without it, we can do with fission.

However, employing the analogy of a computer, the available user storage space is missing the amount of "storage space" that is always used "by the operating system."

I am a civil engineer and there are all kinds of studies which analyze the available land mass of a city that is or must be allocated for use by the city. For example ...

Yes, in those 300 m²/person, the overhead of the ship's structures must be included too. But it's not a lot.

Also note the engines are not on the cylinder, so they aren't part of the 14 km² of area available. The entirety of the central spine is not included there. Plus, you can put a lot of stuff under the hard metal floor, of which I left 6 m (between the 894 and 900 marks). But I am not a starship engineer, so I can't be sure this would work.

I would refer you to an expert, but job applications for starship engineers have gone unfulfilled.

Transportation is definitely going to be important aboard ship. Is there any public mode of transportation? If not, then technically there are going to be small cities by population if you are limited to meeting new people by walking. Bus system? Trolley system? Tubes? Chutes?

That can be under the inner cylinder deck, but can also be above. There will also need to be pylons connecting the drum to the central spine. If there are public trams that go up to the spine, then the central spine can then be used as rapid transit too. It may not be the preferred mode of transport because people would experience weightlessness.

ThinksMarkedly wrote:

penny wrote:For the most part, I agree. However, recycling water is never going to be a 100 % efficient process. If a gallon of water is consumed, we will not get a gallon of water back in urine. The body needs some of the water for itself. The body will lose some in cooling itself off, sweat. We shed tears, etc.

See answers above about a closed system and making water potable again. There may be some water lost through outgassing to space, but it should be minimal and negligible even over centuries. And even if it isn't, getting some more water from some comets in the destination system is easy. Where do you think those ships would get their water in the first place in the Sol system? Hint: it's not going to be by lifting out of the deepest gravity wells.

PS: I understand what you meant, but you did not mean "100% efficient." Nothing is 100% efficient due to the Second Law of Thermodynamics.

The water for radiation shielding cannot be recycled for drinking as it already has a critical use.

Radiation shielding is a matter of probability. The thicker or denser your layer of matter, the higher the probability that radiation will be stopped. So you will have a lot of water in those tanks.

I agree you can't diminish it by constantly dumping water overboard. But outside of some small outgassing and minor losses due to imperfections, the only thing that the ship would be throwing overboard would be reaction mass, and in cruise that's going to be very minimal. They need to have a lot of hydrogen to use for deceleration, so if that came from the water tanks after electrolysis, you're left with a lot of oxygen. Add hydrogen again and you've got water.

And we're told ships as ancient as Calvin's Hope had the ability to replenish fuel (hydrogen) from the Calvin System.

So the ship should be running with full water tanks practically all the time. Since it's a closed system, you take water out of them and add water back in. And if there's any water you can't treat, al you need is to keep it segregated from water you can still use.

I certainly agree. Generation ships should be able to produce water, I am just not sure at what rate of production. There are science fiction stories that deal with this utilizing current technology. The Mars Trilogy comes to mind.

We may not have the technology for this now, but we have line of sight to everything we need to build an interstellar generation colony ship. It requires no new science and no new materials, just application of what we know. And money, lots of it.

The one thing we really would benefit from is fusion power. But even without it, we can do with fission.

However, employing the analogy of a computer, the available user storage space is missing the amount of "storage space" that is always used "by the operating system."

I am a civil engineer and there are all kinds of studies which analyze the available land mass of a city that is or must be allocated for use by the city. For example ...

Yes, in those 300 m²/person, the overhead of the ship's structures must be included too. But it's not a lot.

Also note the engines are not on the cylinder, so they aren't part of the 14 km² of area available. The entirety of the central spine is not included there. Plus, you can put a lot of stuff under the hard metal floor, of which I left 6 m (between the 894 and 900 marks). But I am not a starship engineer, so I can't be sure this would work.

I would refer you to an expert, but job applications for starship engineers have gone unfulfilled.

Transportation is definitely going to be important aboard ship. Is there any public mode of transportation? If not, then technically there are going to be small cities by population if you are limited to meeting new people by walking. Bus system? Trolley system? Tubes? Chutes?

That can be under the inner cylinder deck, but can also be above. There will also need to be pylons connecting the drum to the central spine. If there are public trams that go up to the spine, then the central spine can then be used as rapid transit too. It may not be the preferred mode of transport because people would experience weightlessness.

Indeed. The Second Law of Thermodynamics is why I made the statement. As it applies to the rate of loss of each process, accumulatively, over 600+ years. In addition to the natural rate of loss because of the requirements of each process, accumulatively, over 600+ years.

I still think the natural requirements of a city proper would necessitate smaller cities. Some of the population would live near the livestock, becoming farmers. The needs of the ship would require workers as well. The population would be spread out over the entire available volume of the ship.

It might be more appropriate to refer to them as small towns, rather than cities.

penny wrote:Indeed. The Second Law of Thermodynamics is why I made the statement. As it applies to the rate of loss of each process, accumulatively, over 600+ years. In addition to the natural rate of loss because of the requirements of each process, accumulatively, over 600+ years.

The Second Law of Thermodynamics only talks about energy efficiency. The ship is still a closed system, so both Conservation of Energy and Conservation of Matter apply. There's only one process aboard the ship that will not conserve energy or mass individually: the nuclear fusion. It will fuse hydrogen, deuterium and/or helium into slightly heavier elements, producing a net gain of energy and a net loss of mass.

Aside from that, every single process aboard the ship will conserve mass. It will consume energy from the fusion plant and transform said energy into waste heat, which may be partially absorbed and repurposed. It's at this point that the Second Law applies because not all energy can be reused; some of it will only be unusable waste heat, which the ship will need to radiate out to space.

Everything else conserves mass, including water recycling. It's not 100% efficient in the sense that you can't reverse the process and get the original energy back in the reusable form. But it must conserve 100% of the water and 100% of the impurities that you're trying to get rid of.

If you talk about efficiency in the sense of removing those impurities, then I could agree: the efficiency may be very near 100%, but may not be 100%. However, I need to point out that we've been effectively recycling the same non-salty water on our planet for billions of years, through natural and artificial means. Water treatment plants are well-known and highly efficient, if slow and possibly energy intensive. So it's a matter of how much effort and energy you want to apply to the process. Given that my calculations showed you could make the trip with no water recycling at all, even a poor recycling process would add tremendously.

I still think the natural requirements of a city proper would necessitate smaller cities. Some of the population would live near the livestock, becoming farmers. The needs of the ship would require workers as well. The population would be spread out over the entire available volume of the ship.

It might be more appropriate to refer to them as small towns, rather than cities.

Do note I talked about area, not volume of the ship. If you want 1 Earth Gravity, you need a specific distance from the central axis. And I'm assuming the majority of this volume is actually open space, not ceiling or overhead lamps. That is, if you're standing on your backyard and look nearly straight up, you'll see a neighbour nearly 2 km up, hanging upside down. Straight up there should be a sun-analogue, providing day-time and night-time cycles (which may or may not be 86400 seconds long).

I don't know how the area is going to be utilised. I think you're right and it's not going to be homogenous. It might look indeed like the suburbs in the US, with cul-de-sacs and neighbourhoods, with supporting services, like food distribution, community gathering places, places of worship, parks, etc. There may be also "downtowns" for non-ship business activities, with fancier restaurants, ateliers, workshops, offices, etc. The population is not sitting idle and may be doing science and technology, both on their own and with information beamed from Earth.

But I don't think it will have a proper capitalist economy. There's no sense in having an Apple and a Samsung aboard ship, both making nearly entirely different products which do otherwise serve the same purpose. That would only be allowable to happen if you had multiple ships, at which point you can allow them diverging on what they produce, so long as no one becomes a single point of failure.

ThinksMarkedly wrote:

penny wrote:Indeed. The Second Law of Thermodynamics is why I made the statement. As it applies to the rate of loss of each process, accumulatively, over 600+ years. In addition to the natural rate of loss because of the requirements of each process, accumulatively, over 600+ years.

The Second Law of Thermodynamics only talks about energy efficiency. The ship is still a closed system, so both Conservation of Energy and Conservation of Matter apply. There's only one process aboard the ship that will not conserve energy or mass individually: the nuclear fusion. It will fuse hydrogen, deuterium and/or helium into slightly heavier elements, producing a net gain of energy and a net loss of mass.

I disagree. You are making the same consistent mistake of disregarding how things work in the real world. First off, the ship is not a closed system. Your very own outgassing negates that very optimistic plan on its own. But there is more. See below.

Thinksmarkedly wrote:Aside from that, every single process aboard the ship will conserve mass. It will consume energy from the fusion plant and transform said energy into waste heat, which may be partially absorbed and repurposed. It's at this point that the Second Law applies because not all energy can be reused; some of it will only be unusable waste heat, which the ship will need to radiate out to space.

Everything else conserves mass, including water recycling. It's not 100% efficient in the sense that you can't reverse the process and get the original energy back in the reusable form. But it must conserve 100% of the water and 100% of the impurities that you're trying to get rid of.

Not exactly. Technically, I agree. But at the end of the day, some processes will result in the loss of mass, by necessity.

Take for instance wastewater treatment. Sewage plants produce a lot of sludge. This sludge has been a problem for humanity even before the addition of wastewater treatment plants. Wastewater sludge continues to be a problem today.

Man flushes a slew of pollutants down the toilet. What ends up at the treatment plants is water with high levels of very dangerous pollutants. Some of it radioactive from hospital waste. Hydrocarbons and other pollutants simply take a very long time to filter to acceptable legal limits as well as heavy metals, etc. That is why unacceptable limits of pollutants is consistently found in drinking water across the country. Do absorb the wiki article.

Thinksmarkedly wrote:If you talk about efficiency in the sense of removing those impurities, then I could agree: the efficiency may be very near 100%, but may not be 100%. However, I need to point out that we've been effectively recycling the same non-salty water on our planet for billions of years, through natural and artificial means. Water treatment plants are well-known and highly efficient, if slow and possibly energy intensive. So it's a matter of how much effort and energy you want to apply to the process. Given that my calculations showed you could make the trip with no water recycling at all, even a poor recycling process would add tremendously.

Not exactly! Water treatment plants can be efficient. If the municipality spends the necessary funds for an appropriate system, and or, if the water source is fresh and contaminant free to begin with. Some towns take pride in the purity of their water; especially when the source is a high water table of very clean tasty drinking water underground. But that is frequently not the case. I was looking at TV just yesterday and this community sued the town for paying a premium for tainted unhealthy water. Many communities across the US suffer from tainted water. PFAS is the latest problem that has been unearthed. You might want to have your own water tested lest you have well water. Even well water can be contaminated. But I digress.

If you absorbed the link you know that sludge contains some very nasty stuff. We have the same problem as we do with radioactive waste. Disposal. Treating sludge is a time consuming process (see link). That is why acceptable legal limits are rarely achieved. After treatment, what do we do with the sludge? Some places utilize it as fertilizer. Some municipalities dump it into the ocean. Some cities dump it in landfills. Many cities are banning its use as fertilizer because the sludge is found to still have high levels of heavy metals, etc., then the plants absorb it and then we eat the food. Representing a dangerous link in the circle of life. Dumping it in the ocean has its own problem of contaminating the ocean and the fish. Dumping in landfills damages the soil. So, aboard a generation ship, why go through all of the trouble to filter wastewater sludge when it can simply be dumped into space. An option that is not available on planet. And the traditional methods of disposal are not an option aboard the ship. If it is being dumped into space, that nullifies the notion of a closed system. And as you can see, at the end of the day, the loss of the sludge negates the idea of the conservation of mass.

penny wrote:I still think the natural requirements of a city proper would necessitate smaller cities. Some of the population would live near the livestock, becoming farmers. The needs of the ship would require workers as well. The population would be spread out over the entire available volume of the ship.

Do absorb the link for the problems that could be disastrous for the ship. A major accident that destroys the wastewater holding tanks and introduces the bacteria laden sludge at the wrong time, and you have a very sick ship. There may be deaths.

Thinksmarkedly wrote:

penny wrote:It might be more appropriate to refer to them as small towns, rather than cities.

Do note I talked about area, not volume of the ship. If you want 1 Earth Gravity, you need a specific distance from the central axis. And I'm assuming the majority of this volume is actually open space, not ceiling or overhead lamps. That is, if you're standing on your backyard and look nearly straight up, you'll see a neighbour nearly 2 km up, hanging upside down. Straight up there should be a sun-analogue, providing day-time and night-time cycles (which may or may not be 86400 seconds long).

I don't know how the area is going to be utilised. I think you're right and it's not going to be homogenous. It might look indeed like the suburbs in the US, with cul-de-sacs and neighbourhoods, with supporting services, like food distribution, community gathering places, places of worship, parks, etc. There may be also "downtowns" for non-ship business activities, with fancier restaurants, ateliers, workshops, offices, etc. The population is not sitting idle and may be doing science and technology, both on their own and with information beamed from Earth.

But I don't think it will have a proper capitalist economy. There's no sense in having an Apple and a Samsung aboard ship, both making nearly entirely different products which do otherwise serve the same purpose. That would only be allowable to happen if you had multiple ships, at which point you can allow them diverging on what they produce, so long as no one becomes a single point of failure.

Agreed.

penny wrote:I disagree. You are making the same consistent mistake of disregarding how things work in the real world. First off, the ship is not a closed system. Your very own outgassing negates that very optimistic plan on its own. But there is more. See below.

Whether it's closed or not depends on where I draw the boundary. Every system is closed if we extend the boundaries far enough.

I am including outgassing and losses to space due to imperfections in the process. They are negligible. Over a millennium they will indeed accumulate, but the ship's Bussard scoops will replenish hydrogen. Other metals would be more difficult, of course.

Not exactly. Technically, I agree. But at the end of the day, some processes will result in the loss of mass, by necessity.

Mass is only lost if it's either a) fused into heavier elements whose total mass is lower than the elements being fused (everything below Iron) or b) it's lost to space either via reaction mass (hydrogen only) or outgassing (negligible).

All other processes inside the ship conserve mass. This is pure Physics.

In the real world, I agree that we won't be able to engineer everything to the theoretical physical perfection. But the vast majority of the overall losses is in the form of energy expenditure, not mass that can't be eventually reused. There will be some of it, I agree, but I don't expect it to account for a lot, especially not everything relating to life-support.

Take for instance wastewater treatment. Sewage plants produce a lot of sludge. This sludge has been a problem for humanity even before the addition of wastewater treatment plants. Wastewater sludge continues to be a problem today.

Man flushes a slew of pollutants down the toilet. What ends up at the treatment plants is water with high levels of very dangerous pollutants. Some of it radioactive from hospital waste. Hydrocarbons and other pollutants simply take a very long time to filter to acceptable legal limits as well as heavy metals, etc. That is why unacceptable limits of pollutants is consistently found in drinking water across the country. Do absorb the wiki article.

I hear you. I don't know if we'll ever be able to recycle all of that so that the entire mass can be reused. Do note that it's mostly still a matter of how much effort/energy one wants to spend on the process, not the feasibility of it.

And we are talking about technology some 350 years in the future.

If you absorbed the link you know that sludge contains some very nasty stuff. We have the same problem as we do with radioactive waste. Disposal. Treating sludge is a time consuming process (see link). That is why acceptable legal limits are rarely achieved. After treatment, what do we do with the sludge? Some places utilize it as fertilizer.

Using it as fertiliser is recycling, just with a longer cycle.

Some municipalities dump it into the ocean. Some cities dump it in landfills. Many cities are banning its use as fertilizer because the sludge is found to still have high levels of heavy metals, etc., then the plants absorb it and then we eat the food.

Separating heavy metals is easy. Just expensive.

Starships will need to be designed for the long haul. If you need to remove the heavy metals in treating your waste, then you will need to have the heavy metal separation equipment, however expensive they are, if your voyage is above a certain time threshold.

Representing a dangerous link in the circle of life. Dumping it in the ocean has its own problem of contaminating the ocean and the fish. Dumping in landfills damages the soil. So, aboard a generation ship, why go through all of the trouble to filter wastewater sludge when it can simply be dumped into space. An option that is not available on planet. And the traditional methods of disposal are not an option aboard the ship. If it is being dumped into space, that nullifies the notion of a closed system. And as you can see, at the end of the day, the loss of the sludge negates the idea of the conservation of mass.

Because you need that material. Dumping it into space is a waste and possibly even a navigational hazard for other ships coming after you. Worse: it will go with you to your destination system: we're talking about ships moving at half light or better. The ship will decelerate to make orbit... the waste will not.

You could impart a sideways velocity, but you're not going to expend the energy necessary for it to have sufficient separation to miss the system entirely. The course is still too coarse at the beginning to know where it's going to hit.

No, the only option is that you carry it with you all the way to the destination, with all the ills of hauling trash entail. As you said:

Do absorb the link for the problems that could be disastrous for the ship. A major accident that destroys the wastewater holding tanks and introduces the bacteria laden sludge at the wrong time, and you have a very sick ship. There may be deaths.

If your material is untreated radioactive, it's radiating for all that long. If its storage holds leak, it could contaminate the good supply. Therefore, it behoves a good starship designer to actually treat those things.

Another point is that anything you will not recycle implies you need more of it at the start of your voyage, which means a higher fuel consumption to get up to cruise speed. In today's space industry, we make a lot of astonishingly expensive things that will save a handful of kilograms or pounds, because the fuel is expensive and you must have fuel to lift fuel too.

penny wrote:If you absorbed the link you know that sludge contains some very nasty stuff. We have the same problem as we do with radioactive waste. Disposal. Treating sludge is a time consuming process (see link). That is why acceptable legal limits are rarely achieved. After treatment, what do we do with the sludge? Some places utilize it as fertilizer.

Some municipalities dump it into the ocean. Some cities dump it in landfills. Many cities are banning its use as fertilizer because the sludge is found to still have high levels of heavy metals, etc., then the plants absorb it and then we eat the food. Representing a dangerous link in the circle of life. Dumping it in the ocean has its own problem of contaminating the ocean and the fish. Dumping in landfills damages the soil. So, aboard a generation ship, why go through all of the trouble to filter wastewater sludge when it can simply be dumped into space. An option that is not available on planet. And the traditional methods of disposal are not an option aboard the ship. If it is being dumped into space, that nullifies the notion of a closed system. And as you can see, at the end of the day, the loss of the sludge negates the idea of the conservation of mass.

ThinksMarkedly wrote:Using it as fertiliser is recycling, just with a longer cycle.

Separating heavy metals is easy. Just expensive.

Starships will need to be designed for the long haul. If you need to remove the heavy metals in treating your waste, then you will need to have the heavy metal separation equipment, however expensive they are, if your voyage is above a certain time threshold.

Because you need that material. Dumping it into space is a waste and possibly even a navigational hazard for other ships coming after you. Worse: it will go with you to your destination system: we're talking about ships moving at half light or better. The ship will decelerate to make orbit... the waste will not.

You could impart a sideways velocity, but you're not going to expend the energy necessary for it to have sufficient separation to miss the system entirely. The course is still too coarse at the beginning to know where it's going to hit.

No, the only option is that you carry it with you all the way to the destination, with all the ills of hauling trash entail.

Municipalities have trouble with sludge, because they have no control over what people are eating or otherwise disposing; that will not be true on a colony ship.

Anything organic in sludge is potential fertilizer for the hydroponic gardens. Anything inorganic needs to be separated and stored for reuse. The main sources of problems in sludge involves heavy metals. Most of these should have been eliminated in the building and loading of the ship. Any heavy metal not absolutely needed to sustain life, should have been purged from the ship before it launched. There may be radioactive materials that build due to bombardment of the ship, but these should be kept away from the living areas.

Note that the people also need to go through a purging process to eliminate any heavy metals that they previously ingested before they board the ship.

tlb wrote:Note that the people also need to go through a purging process to eliminate any heavy metals that they previously ingested before they board the ship.

The trace amounts that they have in themselves is not lethal, otherwise they'd already be dead. If it's all they bring aboard, then it'll disperse over the ship over a few years and shouldn't contribute much to their offspring.

I'd be more worried about bacteria and viruses,

tlb wrote:Note that the people also need to go through a purging process to eliminate any heavy metals that they previously ingested before they board the ship.

ThinksMarkedly wrote:The trace amounts that they have in themselves is not lethal, otherwise they'd already be dead. If it's all they bring aboard, then it'll disperse over the ship over a few years and shouldn't contribute much to their offspring.

I'd be more worried about bacteria and viruses,

It's not lethal unless it get concentrated; several thousand people (?), each with some heavy metal adds up to an appreciable amount that some plants can extract. Safer to get rid of it before launching.

Yes, medical checkups should be done at the same time.