I toured Biosphere II twice in the late 2000s and took away a couple things-
*It is always on the ragged edge of cooking everything inside. With tremendous solar gain in the high altitude desert sun, the guide said it could reach 150 degrees or more in just a few hours if the power fails.
*That's why it has a huge set of power lines leading in from the local utility AND a substantial power plant on site, all to drive megawatts of heatpumps to provide chilled water for the many air handlers.
But those are just implementation problems.
The greatest problem with closed ecologies is the inevitable amputation of the atmosphere. In the open on Earth, a square meter of good farmland extends at least 30 cm into the surface and has a mass close to a ton, with perhaps 10 to 50 kg of water available. But the air on top of it outweighs everything else at ten tons. Putting a dome generously ten meters above the soil leaves at most twelve *kilograms* of air, nowhere near enough to buffer the daily flows of water, water vapor, CO2, and oxygen that must flow in and out of the soil and plants. All the ills of ECLSS stem from this desperately limited air supply.
For example, those ten cubic meters of air, at 400 ppm CO2, contain a whopping seven grams of CO2. The enclosed ecosystem is balanced on a knife edge. Any off-earth closed ecosystem will need a good buffer for oxygen, CO2, and nitrogen. All three gases must be able to be drawn from and returned to storage as the biosystems fluctuate in throughput due to seasonal and (on Mars) weather changes.
That is interesting, thanks. One advantage that you will have on Mars is that the internal pressure can provide support to your structure, so you can potentially build much larger.
Biosphere 2 got a lot of stick for pumping in extra gas during the first experiments, but it seems eminently sensible to have chemical production and storage of gasses rather than trying to rely purely on biology.
Oh, yeah, on Mars the problem is not to hold the roof up, but to hold it down. Even if you operate at less than one bar absolute pressure, the entire greenhouse has to be a pressure vessel, not a building.
In "The Martian," Andy Weil snuck in an oxygen compressor as a standard part of the hab that would not be needed for a short duration mission. To make potatoes from CO2 and H2O, a lot of oxygen is released 2CO2 + 2H2O > CH2O + O2, so as he grows spuds his oxygen supply is too much and has to be recompressed. On a flags-and-footprints mission such a compressor would not be needed and never sent.
On the point of space mining and trillionaries: this never made sense to me, as the quadrillions of dollars worth of, say, gold, in asteroids, would collapse gold prices to near zero. And a near infinite supply of a zero cost commodity does not a trillionaire make.
If the size of the economy were a few orders of magnitude bigger than it is today, then I could more easily see quadrillions of dollars of new supply of a commodity not collapsing the price of that commodity to zero.
Peter, it is great that you’re trying to reach outside the bubble! Frankly, I expect that you will find that some people just want to believe this isn’t possible. Perhaps they find comfort in believing so.
I toured Biosphere II twice in the late 2000s and took away a couple things-
*It is always on the ragged edge of cooking everything inside. With tremendous solar gain in the high altitude desert sun, the guide said it could reach 150 degrees or more in just a few hours if the power fails.
*That's why it has a huge set of power lines leading in from the local utility AND a substantial power plant on site, all to drive megawatts of heatpumps to provide chilled water for the many air handlers.
But those are just implementation problems.
The greatest problem with closed ecologies is the inevitable amputation of the atmosphere. In the open on Earth, a square meter of good farmland extends at least 30 cm into the surface and has a mass close to a ton, with perhaps 10 to 50 kg of water available. But the air on top of it outweighs everything else at ten tons. Putting a dome generously ten meters above the soil leaves at most twelve *kilograms* of air, nowhere near enough to buffer the daily flows of water, water vapor, CO2, and oxygen that must flow in and out of the soil and plants. All the ills of ECLSS stem from this desperately limited air supply.
For example, those ten cubic meters of air, at 400 ppm CO2, contain a whopping seven grams of CO2. The enclosed ecosystem is balanced on a knife edge. Any off-earth closed ecosystem will need a good buffer for oxygen, CO2, and nitrogen. All three gases must be able to be drawn from and returned to storage as the biosystems fluctuate in throughput due to seasonal and (on Mars) weather changes.
That is interesting, thanks. One advantage that you will have on Mars is that the internal pressure can provide support to your structure, so you can potentially build much larger.
Biosphere 2 got a lot of stick for pumping in extra gas during the first experiments, but it seems eminently sensible to have chemical production and storage of gasses rather than trying to rely purely on biology.
Oh, yeah, on Mars the problem is not to hold the roof up, but to hold it down. Even if you operate at less than one bar absolute pressure, the entire greenhouse has to be a pressure vessel, not a building.
In "The Martian," Andy Weil snuck in an oxygen compressor as a standard part of the hab that would not be needed for a short duration mission. To make potatoes from CO2 and H2O, a lot of oxygen is released 2CO2 + 2H2O > CH2O + O2, so as he grows spuds his oxygen supply is too much and has to be recompressed. On a flags-and-footprints mission such a compressor would not be needed and never sent.
Still you need a very closed economy. But where is the new Biosphere 2 project?
https://forum.effectivealtruism.org/posts/QianitTHjKBSH2sXC/space-colonization-and-the-closed-material-economy
There is lot of attention to the carriage, but nobody cares about the settlement…
On the point of space mining and trillionaries: this never made sense to me, as the quadrillions of dollars worth of, say, gold, in asteroids, would collapse gold prices to near zero. And a near infinite supply of a zero cost commodity does not a trillionaire make.
If the size of the economy were a few orders of magnitude bigger than it is today, then I could more easily see quadrillions of dollars of new supply of a commodity not collapsing the price of that commodity to zero.
Peter, it is great that you’re trying to reach outside the bubble! Frankly, I expect that you will find that some people just want to believe this isn’t possible. Perhaps they find comfort in believing so.