If you consider that how damaged the entire expedition is (it consists largely of hippy dropouts, ethnic refugees, criminals, and people with personality problems; their leader is a washed-out ex-soldier with PTSD), suddenly it all makes more sense. The reason why they make so many poor decisions is because there's nobody capable of making good ones!
Taking your second-hand colony ships on a one-way trip to a world so far away from anyone that you're years from help? Check. Deliberately picking a world that's got no useful resources? Check. (According to McCaffrey, though.) Basing your economic future on an idealised back-to-the-soil view of the Good Life? Check. Not taking the means to build, repair or refuel the machines that make your civilisation run? Check. Not taking enough people to be able to do things the hard way when the machines do fail? Check...
Of course, this may not have been intentional. McCaffrey is not known for thinking hard about the consequences of her worldbuilding and this could all have been happy coincidence. But it does all fit together.
Threadfall was probably the best thing that could have happened to them; without it they'd have probably have lasted a few generations and reverted to scattered peasantry working hand-to-mouth...
]]>1.And classification systems will need another level above domain or superkingdom to designate which form of life an organism comes from.
]]>There's also Eric Flint's The Mother of Demons, which I consider generally hard SF... just with the sciences being biology and history.
]]>I would have liked to have seen other books in that universe, I think. Maybe books set a thousand years after Pern was re-discovered. Now it's a moot point, of course.
]]>The individual posting here as Anonymous is banned, and if they post here again their comments will be deleted on sight. (If they sprout sock-puppets ... well, if they can be identified as such, they're banned too.)
Reason: egregious trolling, and an attempt to divert an interesting discussion of planetary colonization into a political flame war on territory of their own choosing, followed by attempting to argue with the moderation policy (hint: deleting your comments isn't censorship, you're welcome to go get your own blog and I have no way (or desire) of stopping you from saying anything you want on such a platform). Oh, and all of the above is aggravated by doing it behind my back, while I'm AFK and extremely busy for a week.
]]>Alex Tolley & Heteromeles @ 15/16 U.K. le Guin: "Planet of Exile" ( I still have my ancient, signed copy ) .... Where the colonists and the natives have to join, especially as the colonists are becoming vulnerable to the local nasty biota - eventually.
Markham @ 30 "Surface Tension" ( James Blish? )
]]>Well, efficiency has to be measured relative to the emitter, yes? Even a very primitive single-junction photovoltaic cell can get "efficiencies" in excess of 80% provided the ambient light is tuned to it's particular bandgap, say with a laser.
Same with chlorophyll, I'm told; it would be much more "efficient" under the light of a red sun (making Earth a sort of anti-Krypton). That's not as facetious as it sounds; in times past the notion that chlorophyll works better elsewhere has been cited as evidence of panspermia.
]]>Assumptions:
Average surface insolation of 5 kilowatt hours per square meter. Target oxygen production: 10^18 kilograms (approx. 1/5 of total atmospheric mass of Earth). Photovoltaic conversion efficiency of 15%. Panel lifetime of 27 years. Panel energy payback time of 3 years. This is also the doubling time, if the panels are dedicated to power panel factories. Oxygen production by water electrolysis: 6.25 kilowatt hours per kilogram of oxygen produced.
Starting with a single square meter of panel, it takes 47 doublings (141 years) to cover 140 million square kilometers (approximately equal to all land area on Earth, but floating panels on ocean are preferable to taking land near the poles due to low insolation there).
Each square meter of panel surface can produce 0.75 kilowatt hours of electrical energy daily, though 1/9 of that is budgeted to self-replacement, leaving 0.666 kilowatt hours of useful surplus energy per square meter per day.
If dedicated to water electrolysis, the array's output can produce 1.48 * 10^13 kilograms of oxygen per day. In 185 years it produces as much free oxygen as currently exists in Earth's atmosphere. If released into the atmosphere, the hydrogen should eventually escape the planet's embrace due to its very low molecular weight. Unfortunately, the kinetics of this process are probably too slow to dissipate the hydrogen fast enough to prevent the formation of an explosive atmosphere. Either the process needs to operate sufficiently slowly that the atmospheric composition does not become dangerous or the hydrogen should be used to reduce carbonates and produce stable hydrocarbons**.
I have no idea how much additional oxygen is needed to oxidize low-valence iron. The speed of the process is determined by geological processes after an initial surface oxidation, so that while a large additional amount is needed in geological time it is slight on human time scales. After 185 years the vast majority of the solar array can be dismantled or devoted to other purposes, only a small fraction of the original productive capacity needed to supplement atmospheric oxygen beyond what imported terrestrial phototrophs can do.
*Compared to traveling interstellar distances in the first place.
**Due to the tremendous scale of the project, I am not sure if this is plausible. The limiting factor may not be energy production but safe disposal of byproducts. Incidentally, I feel that this is the same limiting factor that confronts current industrial civilization.
]]>Human in space ship crashes on alien planet, waits without result for rescue, waits as the ship's systems eventually fail around him, wanders around the planet in an environment suit, and (when that and its supplies finally give out too), exposes himself to the local environment on a sea shore, where as he dies he has some sort of shared recognition as life with indigent sapients who witness his demise.
It struck me then, and has stayed with me since, because of its realistic portrayal of incompatibly alien biospheres, and its refusal to supply any deus ex machina happy ending.
Pete Jordan
]]>The machines you are creating need to both self-replicate and move, so 1 cm seems like a probable minimum thickness. So, to cover the planet you need 1,400 cubic km worth of raw materials to make these machines (not counting the mass of materials you need to make the self-replicating mining and refining machines). Now consider the mass of the other materials that isn't easily available silicon. Think about how much earth might need to be moved to extract the aluminum, boron, gallium, arsenic, copper, and whatever else might be needed. That's a whole lot of cubic kilometers of rock and clay to mine.
Life cycle analysis for solar panels doesn't assume that you have refined silicon, wiring, glass, and assembly plants already sitting around; the precursor stages are part of it. I based my energy payback time (e.g. doubling time) on modest real-world figures for current commercial PV tech. I could have assumed better technology that leads to a shorter doubling period, or assumed a longer doubling period to give a larger safety margin, but even if self-duplication takes twice as much energy as I've budgeted that is still lightning-quick compared to the natural processes that oxygenated Earth.
Crushing and refining 1400 cubic kilometers of rock (~4 trillion metric tons) is no big deal in this context. Double or triple that figure if you like. Keep in mind that it's more energetically expensive, gram for gram, to decompose water into hydrogen and oxygen than to mine and process hard rock, and the solar array's main job is already to split 1125 trillion (1.125 * 10^15) metric tons of water.
I don't think that rare elements are going to be a big holdup. Silicon, oxygen, and aluminum are the 3 most abundant elements in the Earth's crust. With these 3 elements you can produce glass, the actual silicon for cells, structural supports, and electrical connections. Silicon PV doesn't require arsenic or gallium. Aluminum can be used instead of copper for electrical conductors at a moderate performance penalty. The electrolysis process can use iron cathodes and carbon anodes -- again, very abundant and widely distributed elements.
The rarest elements you need in the panel assemblies are phosphorus and boron for doping silicon, but only at ppm levels. If you take a kilogram of homogenized terrestrial crust and use only the silicon and dopant elements (phosphorus and boron) in it, you'll actually have a surplus of dopants left over after turning the silicon into purified PV material.
]]>How about high-temperature fuel cells and chemical energy storage for the minority share of energy that does need to be supplied continuously? You don't need any rare metal catalysts for them and you're already going to be producing hydrogen and oxygen from water. Until the atmospheric conversion process is well along you can even store the oxygen alone and get "free fuel" from the atmosphere* (the opposite of Earth, where the oxidizing atmosphere means you have to store fuel but oxygen is "free"). This is advantageous because oxygen is much easier to store than hydrogen. The round-trip electrical storage efficiency is worse than with flywheels or batteries, but the total mass and space requirements are considerably lower. If you need thermal energy rather than electrical, chemical energy storage is actually perfect and requires only a burner to recover that stored energy.
*If the planet has a reducing atmosphere something like the composition used in the Urey-Miller experiment, then you can substantially increase efficiency by always (or at least until bulk atmospheric change renders it infeasible) using the electrolytically produced oxygen in high-temperature fuel cells to recover some useful heat and electricity. The oxygen's going to release the same amount of energy on oxidizing the atmosphere whether it happens naturally and slowly or swiftly and in your fuel cell. But in the latter case you get some useful work out of the reaction. If the planet has a reducing atmosphere to start with it will also take longer to oxidize it and start building up free oxygen in the atmosphere, so in that case the process will take longer regardless of any cleverness with partial energy recovery using the oxygen.
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