1. Building enough trays to contain even six inches of water, over several square miles. 2. Pumping enough water to fill said trays 3. Pumping enough water to keep the trays filled against evaporative effects, or inversly to cover all the trays and keep temperature in the right range. 4. Stocking the trays with the right nutrient and algae stock 5. Collecting and refreshing the trays.
Power shouldn't be much of a hassle, solar panels and maybe a nuclear plant to handle night-time power demands.
As milamber3 said, it's the red blood cells they need, followed by platelets. If they could remove everything else, leaving a saline/glucose solution with rbc and platelets, they'd likely do it. Heck, there's situations where they'd want to remove the platelets as well.
In an emergency situation you wouldn't be worried about the nutritional substances. There it's about keeping oxygen flow up until they get to the hospital. Heck, with a working artificial blood substitute if that means they gotta run 5 gallons through you, they can do it.
Something I didn't know before that I learned from the article: Anyone can receive type O blood without risk
I got that from junior high biology. Actual issues are more complicated when you get in deep, of course. One oddball is that you can usually survive 1 non-matching transfusion, even if it's incompatible. After that your immune system is 'primed', much like for a vaccination, and will attack a second transfusion with extreme prejudice, likely resulting in your death.
And we are testing at least one blood substitute. The last one I read about(sorry, dead tree article), was intended for use in ambulances, which can't normally carry blood. Unfortuantly, it actually performed worse than saline IV's when it came to patient survival.
As for simply cloning a blood supply, it's difficult because you'd have to clone marrow, as blood cells no longer have a nucleous. Not insurmountable at this point, but currently unable to compete with donated blood.
Here's another link for you: Motor efficiency by load. Sorry about the pdf format, couldn't really find it elsewhere.
Taking a 'Best Case' 75-100 hp motor, at 20% load(15hp) would be 95% as efficient as at full load. We're down to about 90% efficient. Still pretty good. If we drop to a more realistic econobox level motor, 30-60 hp(6 hp at.2), We're loosing ~8% over it's max, which is 93-94% efficiency. Around 86% efficient.
One oddball thing: the 75HP motor is likely to be just as efficient in the 30-60 hp range than the one operating at full load. It started higher, and hasn't really started to loose efficiency yet.
Cars run over a much wider load range, and typically operated at between 20 and 40 percent of max load.
That's for a gasoline engine. Due to a gasoline engine's power factors, in order to give quick starts you have to massivly overpower it. Also, a gasoline engine is rated at it's maximum horsepower. A electric is rated at it's highest sustainable horsepower. Please not that the efficiency scale goes beyond 100%. It's perfectly possible to overdrive an electric motor quite a bit. While the chart only goes to 120%, it's possible to go way beyond that for short periods. Heck, run air through the motor to keep it cool you can raise the max sustained horsepower. Now where would I get air pressure at 75mph...;)
With the combination of 100% torque at 0 rpm and overdrive capabilities, the conventional sizing rule of thumb for people who convert cars to electric(sorry, no link atm) is to get comparable performance you need an electric motor of 1/3-1/2 the horsepower of the gasoline engine. So you size it to be able to sustain the car at 75-80 mph(use overdrive to get there), that puts your 20% level around 25 mph. You remain more than 80% efficient through the whole range.
Besides, if you're hanging around 25 mph for extended times, odds are you're not going to stress a 150-300 mile range.
95% efficiency in changing the rotational energy of the motor to electricity followed by 95% efficiency back to rotational at the wheels would be 90% efficient. The diesel engine only wishes it was so efficient. Add in that the diesel can be run in it's optiomal RPM range 100% of the time and you get a few more percentage points.
90% is better than many areas. Oh, and that's for a premium efficiency 250hp motor, I'd imagine that a train engine would be even bigger, and they increase in efficiency by size.
But, yeah, given the expense and weight for the transmission/differentials for a train gearbox; the series method makes sense. In many ways you could consider it an electric transmission.
With the amount of torque that trains need to get up to speed the gear box would need to be as long, if not longer, than the train itself. You'd need a 10000:1 (made up number) gear ratio to get the train moving, but that ratio would only be good for 1000-2000 RPM, so you'd have to shift to 9999:1, etc.
More to the point; the transmission required would be complex, and the torques involved would kill even an incredibly heavy one very quickly.
As you note; even a gear transmission such as what's in a manual transmission costs power.
Electric generators/motors scale well; at the size involved for a train, I can see 98-99% efficiency. So I'd imagine that something around 96% of the power gets to the train's wheels; actually better than most transmissions.
We haven't seen a diesel hybrid because of cost, mainly.
A hybrid, right now, barely makes economic sense in even optimal circumstances for it, IE lots of inner-city driving. A diesel is unfamiliar technology to most people in the USA, and while a diesel engine would increase the mpg of a hybrid, the gain from combining the two technologies would be marginal. The additional cost of a diesel engine would be a killer for the vehicle. The emissions requirements would be a killer as well, gasoline engines are currently cleaner in the tests than diesel.
Security is the only place where it becomes an issue - but seriously, it shouldn't be that hard. Google built an empire on white-box commodity-hardware. We can't build a machine that properly counts clicks?
Las Vegas manages to operate thousands of video gambline machines that are far more complicated mechanically speaking(it has to dispense stuff) that have to pass extremely rigorous standards, there are millions of ATM machines that have incredibly low error rates.
Sure, we could build it. It'd likely be more complicated to set up than the diebold stuff. It'd certainly be more expensive. ATMs used to have more problems and offer more limited service. There used to be some easy ways to fool with slot machines and such.
Still, right now I happen to like the idea of #2 pencil style OCR paper ballots. They're simple, human readable while still giving you most of the speed of electronic.
Besides, why do we need to know the winners *now*? They won't take office until months down the road anyways.
MAD has worked against the soviet union, but we face a number of other threats. North Korea as an example, China more long term.
I believe that maintaining the option is for the best, though we don't need thousands of warheads.
It's very high level at this point, but any country we deal with knows, at some level, that if we reach a certain point we can destroy them for virtually no cost for ourselves. Sure, a nuke is expensive, but it's dwarfed by the cost of an invasion/occupation force.
As I said before (not to you), it's the bold part I don't like. We should not have nuclear weapons.
And I think we should. MAD works/worked. We didn't get WWIII. Despite all the violence going on, the world is actually relativly peaceful for what you'd expect even a hundred years ago with our population.
We've already sworn off chemical and biological weapons. Besides, nuclear weapons could be usefull in space for non-warfare purposes.
Why should anybody pay attention to us when we ask them to stop making nukes?
Because we have nukes? Not to mention the largest navy and air force, and one of the largest armies?
Besides, our position is 'anti-proliferation', not 'anti-existance'. Our position is that we don't want anybody who doesn't already have nukes to get or build them. Those that already have them get to keep them. Though we generally also don't want them to be increasing their stockpile.
Lead(PB) is extremely common, used for all sorts of things from fishing weights, bullets, solder to radiation shielding.
Using a few tons of lead for radiation shielding isn't enough to impact the lead market in any meaningful way. Uranium is pretty much used solely in the nuclear industry, so a 50% increase in that will have a substantial effect.
But yeah, we've been living off of borrowed time for uranium for a while. We did a lot of exploration back during the WWII/early cold war period, found enough deposits to build enough bombs to blow up a good chunk of the earth, then pretty much quit because it wasn't economical to continue, we had enough stock for all demands for the next ~50 years or so.
Same story as oil, in other words. It's still going to take more than a 900% price increase to really start affecting nuclear power; The cost of the fuel is still considered 'insignificant'. It'd be like if gasoline for your car was one cent a gallon a decade ago and ten cents today. Paying somebody to refuel your car would still cost more than the fuel.
Not to put you down or anything, but any used product market is also driven by the primary new product market. In some ways it actually allows the producers of the product to charge more, in that the moderately wealthy trade up, buying a new product when they would have otherwise held onto their current product, and somebody who would have otherwise not bought buys the used product at a reduced price. As an example, I'd be willing to bet that new car sales would drop significantly if there wasn't a secondary market for cars.
If no new CDs were available, you'd quickly find the cost of your pawn shop CDs exceeding the $12-20 of a new CD today.
Besides, they've successfully pushed a 'New is better!' philosophy on much of the world.
If you go back to one of my earlier posts, you'll see that I mention that the 'hydroponics' might not actually be such. They may still end up using some sort of potting material, and I've seen some fascinating research on aereoponics, where the roots aren't even placed in water.
Yes, there are many complications, which is why I'd love to see some more serious research on it. A test module on the ISS, for example.
This single mix will work fine... for a while. However, the soluable ion ratios get messed up by the plants' selective absorption over time, in addition to plant waste products
A solar still shouldn't be hard, and that'll provide you will distilled water. There's various methods to seperate out the remaining stuff for re-use. Obviously you wouldn't bother until you're talking about a BIG installation.
As for the testing, we're developing silicon based test chips. You place a drop of liquid on them and they can perform hundreds of chemical tests that would normally take at least a milliliter each, and provide results in seconds rather than minutes/hours.
Anyways, back to the minerals. Where are you going to get all of them? You can't just "compost" plants in an isolated environment;
Remember the.1 per day? Plants do need minerals and such, but not much. As for composting, why not? Though I was imagining drying and processing via solar energy. Heck, you could even burn it once dry to reduce stuff out. Take more oxygen that way, but we're planning on feeding the stuff to plants eventually anyways.
waste gasses will build up quickly. Just one example: ammonia. Are you going to just vent it? Then you're losing your precious nitrogen. Going to refine it? Then you'll need a whole refinery, just for that one waste product. What you get out of compost is *not* something that you can just throw into the water for your hydroponics solution, anyways.
Why do you think that I have the 'greenhouse' version take up 1,000 times the initial mass as for traditional systems? Ten tons per person? For one I'm imagining a heck of a lot more air mass per person than the shuttle or ISS provides in it's pressurized spaces. I was half imagining a plankton type system used to bulk out the astronaught's diet for initial versions. And I left an out, in the form of the.1 per day. 100 grams of extras, per person, per day. My idea is that you pile on the resources(mass), until you DO have a sustainable enviroment. As for the chemicals, they haul plant life up fairly frequently in small containers for various tests, so they must have some of the issues resolved.
Heck, part of my idea, at least in station form, is to keep sending up supplies. The very food you send up helps provide the mass and chemicals necessary to eventually start a biological LS system.
Would you at least agree with my thought that a biological LS system doesn't make sense until you're talking BIG and LONG TERM? Even if you can't recycle everything, the fact that you'd only need to transport up suppliment nutrients and plant fertalizer minerals would be a great savings of mass in the (very)long run. Keep saving the waste(freeze dried) and eventually you'll have enough that sending up a reprocessing facility would make sense.
Plants don't actually need a wide variety of fertilizers to grow, especially if you select the right ones. They do need trace minerals, but that's far more compact than bulk food storage.
Besides, I'd envisioned it being a mostly complete recycling solution; most of the fertalizer would be obtained from traditional sources, though treated to prevent disease spread.
Hydroponics is not just "seed + water + carbon dioxide + light".
Duh... But you should be able to recycle just about everything else you need.
I'll fully admit that hydroponic type systems are going to be the most massive and bulky refresh systems for the the capacity (IE keep X people alive), but have the longest duration(effectivly indefinate). IE it scales up well, but not down. Meanwhile our current systems scale down well, but are pretty much linear for duration. Want to double the duration? Multiply everything by 2. You'll have some efficiency of scale, but not much.
Traditional LS: 10x+10xy (10 kilos per person, plus 10 kilos per person per day) 'Greenhouse' LS: 10000x +.1xy
Numbers are completely made up, just used as an example. I was thinking of examples for air, water, food, CO2 disposal, but not shelter, heat, or cooling. Actual equations would be far, far more complicated. In my example, traditional life support would make more sense until you're looking at a mission profile of greater than 1009 days, or 2.8 years.
Ummm... Because you'd not only get rid of your scrubbers and bottles* but a good bit of food storage?
Please note that in my context any sort of CO2 splitting by mechanical or biological means only comes into play for extremely long duration space habitation. The trip to Mars, the establishment of a moonbase, etc... Nothing less than 6 months between resupplies, preferably into the years.
I'd imagine that you'd be able to create a hydroponics bay fairly easily, whether you use direct exposure or some sort of light tube.
*Yes, you'd have reserves, and initial systems won't cover 100% of demand, but should cover much of it.
The efficiency of plants doesn't really matter as much; they're still our main source of food. You'd be able to supply sufficient solar energy to your hydroponic* bay on a mars trip rather trivialy, whereas creating a solar array to generate the necessary power to split CO2 would be a difficult tasking. At least with the hydroponics you'd be serving a double purpose-CO2&H2O scrubbing and generation of additional food for the journey.
You're right about methane production, though most uses of it would require O2 again. I had the oddball idea of the H2 being used as reaction mass in a fusion reactor, or as a propellent for a nuclear engine.
*Might not actually be hydroponic, but it's easier to say...
We could, but the reason we don't re-split in most cases is power.
For example, a spaceship on a journey to mars, powered by a nuclear reactor could indeed use a system to split CO2/H20 back into C, H2, and O2. It'd take loads of juice and likely be quite bulky, but it'd work. You stick the hydrogen into the fuel tanks, breath the O2 again, and either store or eject the carbon. It might even make sense over carrying six months to two years* of O2. This is, of course, assuming that we don't go the organic route and have some sort of greenhouse that'll do the splitting naturally, as well as generate food doing it.
Now, due to said power and bulk requirements, it's cheaper even for the shuttle to merely use CO2 scrubbers and compressed air cylinders to provide life support. This is doubly true for space suits where weight and size are paramount, duration not so much. You're not going to be spending weeks in a space-suit, nor are you going to be spending years in a space shuttle.
Slashdot Mirror
But are a number of economic ones...
1. Building enough trays to contain even six inches of water, over several square miles.
2. Pumping enough water to fill said trays
3. Pumping enough water to keep the trays filled against evaporative effects, or inversly to cover all the trays and keep temperature in the right range.
4. Stocking the trays with the right nutrient and algae stock
5. Collecting and refreshing the trays.
Power shouldn't be much of a hassle, solar panels and maybe a nuclear plant to handle night-time power demands.
The opposite, actually...
A Pos.
There's a chance anytime you inject something into the human body there of there being an immune response to it. Very few items are immune from this.
As milamber3 said, it's the red blood cells they need, followed by platelets. If they could remove everything else, leaving a saline/glucose solution with rbc and platelets, they'd likely do it. Heck, there's situations where they'd want to remove the platelets as well.
In an emergency situation you wouldn't be worried about the nutritional substances. There it's about keeping oxygen flow up until they get to the hospital. Heck, with a working artificial blood substitute if that means they gotta run 5 gallons through you, they can do it.
Something I didn't know before that I learned from the article: Anyone can receive type O blood without risk
I got that from junior high biology. Actual issues are more complicated when you get in deep, of course. One oddball is that you can usually survive 1 non-matching transfusion, even if it's incompatible. After that your immune system is 'primed', much like for a vaccination, and will attack a second transfusion with extreme prejudice, likely resulting in your death.
And we are testing at least one blood substitute. The last one I read about(sorry, dead tree article), was intended for use in ambulances, which can't normally carry blood. Unfortuantly, it actually performed worse than saline IV's when it came to patient survival.
As for simply cloning a blood supply, it's difficult because you'd have to clone marrow, as blood cells no longer have a nucleous. Not insurmountable at this point, but currently unable to compete with donated blood.
Here's another link for you: Motor efficiency by load.
.2), We're loosing ~8% over it's max, which is 93-94% efficiency. Around 86% efficient.
;)
Sorry about the pdf format, couldn't really find it elsewhere.
Taking a 'Best Case' 75-100 hp motor, at 20% load(15hp) would be 95% as efficient as at full load. We're down to about 90% efficient. Still pretty good. If we drop to a more realistic econobox level motor, 30-60 hp(6 hp at
One oddball thing: the 75HP motor is likely to be just as efficient in the 30-60 hp range than the one operating at full load. It started higher, and hasn't really started to loose efficiency yet.
Cars run over a much wider load range, and typically operated at between 20 and 40 percent of max load.
That's for a gasoline engine. Due to a gasoline engine's power factors, in order to give quick starts you have to massivly overpower it. Also, a gasoline engine is rated at it's maximum horsepower. A electric is rated at it's highest sustainable horsepower. Please not that the efficiency scale goes beyond 100%. It's perfectly possible to overdrive an electric motor quite a bit. While the chart only goes to 120%, it's possible to go way beyond that for short periods. Heck, run air through the motor to keep it cool you can raise the max sustained horsepower. Now where would I get air pressure at 75mph...
With the combination of 100% torque at 0 rpm and overdrive capabilities, the conventional sizing rule of thumb for people who convert cars to electric(sorry, no link atm) is to get comparable performance you need an electric motor of 1/3-1/2 the horsepower of the gasoline engine. So you size it to be able to sustain the car at 75-80 mph(use overdrive to get there), that puts your 20% level around 25 mph. You remain more than 80% efficient through the whole range.
Besides, if you're hanging around 25 mph for extended times, odds are you're not going to stress a 150-300 mile range.
This would only be true if Diebold wanted to make voting machines that work properly. They don't.
Conspiricy theories aside; by that logic diebold should have been able to produce machines that ARE secure; except for their little back door.
That way they could have continued to deliver elections to their republican masters for years to come rather than spark this stuff.
I know that you can't be 100% efficient, but 95+% is too low?
95% efficiency in changing the rotational energy of the motor to electricity followed by 95% efficiency back to rotational at the wheels would be 90% efficient. The diesel engine only wishes it was so efficient. Add in that the diesel can be run in it's optiomal RPM range 100% of the time and you get a few more percentage points.
90% is better than many areas. Oh, and that's for a premium efficiency 250hp motor, I'd imagine that a train engine would be even bigger, and they increase in efficiency by size.
But, yeah, given the expense and weight for the transmission/differentials for a train gearbox; the series method makes sense. In many ways you could consider it an electric transmission.
With the amount of torque that trains need to get up to speed the gear box would need to be as long, if not longer, than the train itself. You'd need a 10000:1 (made up number) gear ratio to get the train moving, but that ratio would only be good for 1000-2000 RPM, so you'd have to shift to 9999:1, etc.
More to the point; the transmission required would be complex, and the torques involved would kill even an incredibly heavy one very quickly.
As you note; even a gear transmission such as what's in a manual transmission costs power.
Electric generators/motors scale well; at the size involved for a train, I can see 98-99% efficiency. So I'd imagine that something around 96% of the power gets to the train's wheels; actually better than most transmissions.
We haven't seen a diesel hybrid because of cost, mainly.
A hybrid, right now, barely makes economic sense in even optimal circumstances for it, IE lots of inner-city driving. A diesel is unfamiliar technology to most people in the USA, and while a diesel engine would increase the mpg of a hybrid, the gain from combining the two technologies would be marginal. The additional cost of a diesel engine would be a killer for the vehicle. The emissions requirements would be a killer as well, gasoline engines are currently cleaner in the tests than diesel.
Security is the only place where it becomes an issue - but seriously, it shouldn't be that hard. Google built an empire on white-box commodity-hardware. We can't build a machine that properly counts clicks?
Las Vegas manages to operate thousands of video gambline machines that are far more complicated mechanically speaking(it has to dispense stuff) that have to pass extremely rigorous standards, there are millions of ATM machines that have incredibly low error rates.
Sure, we could build it. It'd likely be more complicated to set up than the diebold stuff. It'd certainly be more expensive. ATMs used to have more problems and offer more limited service. There used to be some easy ways to fool with slot machines and such.
Still, right now I happen to like the idea of #2 pencil style OCR paper ballots. They're simple, human readable while still giving you most of the speed of electronic.
Besides, why do we need to know the winners *now*? They won't take office until months down the road anyways.
31 machines out of 340 districts? How many were in each district?
Heck, from what I've read, they've had problems with more than 10% of the diebold machines.
At least with an automark type system you still have the paper ballots to fall back on, even if a voter might require assistance to fill it out.
When a diebold type device malfunctions you have the potential for lost and/or erronous vote information, not to mention that NO votes can be taken.
MAD has worked against the soviet union, but we face a number of other threats. North Korea as an example, China more long term.
I believe that maintaining the option is for the best, though we don't need thousands of warheads.
It's very high level at this point, but any country we deal with knows, at some level, that if we reach a certain point we can destroy them for virtually no cost for ourselves. Sure, a nuke is expensive, but it's dwarfed by the cost of an invasion/occupation force.
Minot, ND.
Do me a favor while you're at it though, please replace the coal plant south of us.
As I said before (not to you), it's the bold part I don't like. We should not have nuclear weapons.
And I think we should. MAD works/worked. We didn't get WWIII. Despite all the violence going on, the world is actually relativly peaceful for what you'd expect even a hundred years ago with our population.
We've already sworn off chemical and biological weapons. Besides, nuclear weapons could be usefull in space for non-warfare purposes.
Why should anybody pay attention to us when we ask them to stop making nukes?
Because we have nukes? Not to mention the largest navy and air force, and one of the largest armies?
Besides, our position is 'anti-proliferation', not 'anti-existance'. Our position is that we don't want anybody who doesn't already have nukes to get or build them. Those that already have them get to keep them. Though we generally also don't want them to be increasing their stockpile.
Of course it's hypocritical. Most nations are.
Inching away
Not me. I'm at a full bore sprint.
Lead(PB) is extremely common, used for all sorts of things from fishing weights, bullets, solder to radiation shielding.
Using a few tons of lead for radiation shielding isn't enough to impact the lead market in any meaningful way. Uranium is pretty much used solely in the nuclear industry, so a 50% increase in that will have a substantial effect.
But yeah, we've been living off of borrowed time for uranium for a while. We did a lot of exploration back during the WWII/early cold war period, found enough deposits to build enough bombs to blow up a good chunk of the earth, then pretty much quit because it wasn't economical to continue, we had enough stock for all demands for the next ~50 years or so.
Same story as oil, in other words. It's still going to take more than a 900% price increase to really start affecting nuclear power; The cost of the fuel is still considered 'insignificant'. It'd be like if gasoline for your car was one cent a gallon a decade ago and ten cents today. Paying somebody to refuel your car would still cost more than the fuel.
I buy them for a dollar at the pawn shop.
Not to put you down or anything, but any used product market is also driven by the primary new product market. In some ways it actually allows the producers of the product to charge more, in that the moderately wealthy trade up, buying a new product when they would have otherwise held onto their current product, and somebody who would have otherwise not bought buys the used product at a reduced price. As an example, I'd be willing to bet that new car sales would drop significantly if there wasn't a secondary market for cars.
If no new CDs were available, you'd quickly find the cost of your pawn shop CDs exceeding the $12-20 of a new CD today.
Besides, they've successfully pushed a 'New is better!' philosophy on much of the world.
If you go back to one of my earlier posts, you'll see that I mention that the 'hydroponics' might not actually be such. They may still end up using some sort of potting material, and I've seen some fascinating research on aereoponics, where the roots aren't even placed in water.
.1 per day? Plants do need minerals and such, but not much. As for composting, why not? Though I was imagining drying and processing via solar energy. Heck, you could even burn it once dry to reduce stuff out. Take more oxygen that way, but we're planning on feeding the stuff to plants eventually anyways.
.1 per day. 100 grams of extras, per person, per day. My idea is that you pile on the resources(mass), until you DO have a sustainable enviroment. As for the chemicals, they haul plant life up fairly frequently in small containers for various tests, so they must have some of the issues resolved.
Yes, there are many complications, which is why I'd love to see some more serious research on it. A test module on the ISS, for example.
This single mix will work fine... for a while. However, the soluable ion ratios get messed up by the plants' selective absorption over time, in addition to plant waste products
A solar still shouldn't be hard, and that'll provide you will distilled water. There's various methods to seperate out the remaining stuff for re-use. Obviously you wouldn't bother until you're talking about a BIG installation.
As for the testing, we're developing silicon based test chips. You place a drop of liquid on them and they can perform hundreds of chemical tests that would normally take at least a milliliter each, and provide results in seconds rather than minutes/hours.
Anyways, back to the minerals. Where are you going to get all of them? You can't just "compost" plants in an isolated environment;
Remember the
waste gasses will build up quickly. Just one example: ammonia. Are you going to just vent it? Then you're losing your precious nitrogen. Going to refine it? Then you'll need a whole refinery, just for that one waste product. What you get out of compost is *not* something that you can just throw into the water for your hydroponics solution, anyways.
Why do you think that I have the 'greenhouse' version take up 1,000 times the initial mass as for traditional systems? Ten tons per person? For one I'm imagining a heck of a lot more air mass per person than the shuttle or ISS provides in it's pressurized spaces. I was half imagining a plankton type system used to bulk out the astronaught's diet for initial versions. And I left an out, in the form of the
Heck, part of my idea, at least in station form, is to keep sending up supplies. The very food you send up helps provide the mass and chemicals necessary to eventually start a biological LS system.
Would you at least agree with my thought that a biological LS system doesn't make sense until you're talking BIG and LONG TERM? Even if you can't recycle everything, the fact that you'd only need to transport up suppliment nutrients and plant fertalizer minerals would be a great savings of mass in the (very)long run. Keep saving the waste(freeze dried) and eventually you'll have enough that sending up a reprocessing facility would make sense.
Plants don't actually need a wide variety of fertilizers to grow, especially if you select the right ones. They do need trace minerals, but that's far more compact than bulk food storage.
.1xy
Besides, I'd envisioned it being a mostly complete recycling solution; most of the fertalizer would be obtained from traditional sources, though treated to prevent disease spread.
Hydroponics is not just "seed + water + carbon dioxide + light".
Duh... But you should be able to recycle just about everything else you need.
I'll fully admit that hydroponic type systems are going to be the most massive and bulky refresh systems for the the capacity (IE keep X people alive), but have the longest duration(effectivly indefinate). IE it scales up well, but not down. Meanwhile our current systems scale down well, but are pretty much linear for duration. Want to double the duration? Multiply everything by 2. You'll have some efficiency of scale, but not much.
Traditional LS: 10x+10xy (10 kilos per person, plus 10 kilos per person per day)
'Greenhouse' LS: 10000x +
Numbers are completely made up, just used as an example. I was thinking of examples for air, water, food, CO2 disposal, but not shelter, heat, or cooling. Actual equations would be far, far more complicated. In my example, traditional life support would make more sense until you're looking at a mission profile of greater than 1009 days, or 2.8 years.
Ummm... Because you'd not only get rid of your scrubbers and bottles* but a good bit of food storage?
Please note that in my context any sort of CO2 splitting by mechanical or biological means only comes into play for extremely long duration space habitation. The trip to Mars, the establishment of a moonbase, etc... Nothing less than 6 months between resupplies, preferably into the years.
I'd imagine that you'd be able to create a hydroponics bay fairly easily, whether you use direct exposure or some sort of light tube.
*Yes, you'd have reserves, and initial systems won't cover 100% of demand, but should cover much of it.
The efficiency of plants doesn't really matter as much; they're still our main source of food. You'd be able to supply sufficient solar energy to your hydroponic* bay on a mars trip rather trivialy, whereas creating a solar array to generate the necessary power to split CO2 would be a difficult tasking. At least with the hydroponics you'd be serving a double purpose-CO2&H2O scrubbing and generation of additional food for the journey.
You're right about methane production, though most uses of it would require O2 again. I had the oddball idea of the H2 being used as reaction mass in a fusion reactor, or as a propellent for a nuclear engine.
*Might not actually be hydroponic, but it's easier to say...
We could, but the reason we don't re-split in most cases is power.
For example, a spaceship on a journey to mars, powered by a nuclear reactor could indeed use a system to split CO2/H20 back into C, H2, and O2. It'd take loads of juice and likely be quite bulky, but it'd work. You stick the hydrogen into the fuel tanks, breath the O2 again, and either store or eject the carbon. It might even make sense over carrying six months to two years* of O2. This is, of course, assuming that we don't go the organic route and have some sort of greenhouse that'll do the splitting naturally, as well as generate food doing it.
Now, due to said power and bulk requirements, it's cheaper even for the shuttle to merely use CO2 scrubbers and compressed air cylinders to provide life support. This is doubly true for space suits where weight and size are paramount, duration not so much. You're not going to be spending weeks in a space-suit, nor are you going to be spending years in a space shuttle.
*Margins, redundancy, and mission duration.
Soap box, the ballot box, jury box and ammo box
--To be used roughly in that order.