PB666

At that level not alot. The biggest problem is secondary cosmic radiation getting into the living areas. It is almost always the case that adsorption, inhalation or ingestion of radiation is going to be far more toxic than EM radiation. There are exceptions, such as ultrahigh energy gamma. You need magnitudes more damaging ionizing radiation that you do the source of that radiation to get significant damage. There are situations where gamma radiation is a factor, for example, if the males in the colonies wait until their 40s and 50s to have offspring, in that case gamma radiation could be problematic.

Cosmic rays are radiation of the massive type not of the massless type. When they decay the decay products are short lived and exhibit some quantum and relativistic traits. Because of this they can pass right by a heavy nucleaus like lead and couple with lighter nuclei like hydrogen. Even in 1943 they were detecting cosmic rays that passed through 15 cm of lead. That was the point of the article. You still continue to pretend that cosmic rays have an unusual sensitivity to iron and lead. If a proton hits carbon fiber then it degrades. The level of cosmic radiation is 104 to 105 per meter squared per second, however those with energies capable of nuclear fussion are in the 100 to 1000 fold fewer. Carbon Fiber has a density of 1.7 grams per ml. It is largely composed of carbon with some nitrogen. The level of carbon is about 80% making the carbon density 1.36 gram per ml. Avagadros number is 6.0223 x 1023. This converts to 6.82E22 C per cubic centimeter. That translates into 6.82E28 per cubic meter of carbon fiber at a 0.1 M in thickness that translates into 6.8E27 C per meter of carbon fiber hull. Lets argue that a hull has twice the rated stress limit, and that a strand is structural if a million atom constituants are integral. So that in order for the wall to fail it means that roughly 1.364E23 carbons degrade per square meter of hull. In the original calculation give 102 to 104 how long would it take for the cosmic radiation take to 'f-up' the hull T = 1.364E23/10E4 = 1.364E19 seconds = 430 trillion years. Assuming that the vessel has 100 year life (and cannot be resurfaced) the carbon fibers would have to be fatally sensitive to one damage in 10E18 carbon molecules. So you can stop with the fluffy just so arguments. We got you Kerb, we know where you are coming from.

My thoughts on this: The least likely agency to make a near future moon colony is the ESA, The EU simply takes too long to do anything and everything is too political The second least likely is the current administration, In fact if they say there is going to be a space colony on the moon, it registers in my mind as most likely a colony at the Bal-Mara resort in Florida, complete with play-boy space vixens dressed up a venusians serving $1,000,000,000 cocktails to any international visitors that want "the very best [insert superlative] space experience in the Wwwwhhhhoooolllllleeeee Universe". The third least likely are the Russians, despite the past failures of the Russians, Putin generally does what he says (although check your pockets later because its likely he will not have paid for it [Proceeds on Moonland space resort in Bal Mara]). The most likely first new colony built on the Moon is likely to be the Chinese. (Expect a bunch of fatalities, but they got the guts we lost after the 70's), no big fan of Chinese science but they will get it done. Why is it that each new administration feels fit to jerk NASA's chain?

More Vapor-ware.

Delta VI has better mains.

Random jargon throw? How is oxygen purification going to get that water out of the Martian poles.

Solar power is not adequate in the region of Mars where water is most abundant. Settlements above latitude 65' N or below 65'S need another source of power. There is no nulcear power source at presence suitable for the extraction of water from is most abundant sources on mars. The space reactors discussed so far are less than 10 kw.

You are not familiar with gamma, I worked with gamma for 35 years, I was an RSO. 1. Gamma is all around you all the time. Most people are surprised to find there is more radiation already in a room than when they open a vial of isotope and start working with it. You actually have to be using millicurie amounts before you can see noticeable effects in ambient gamma rise. 2. Studies in N. Iran have demonstrated that people who have a 10 fold higher level of exposure to background gamma radiation are at no increased risk for birth defects or cancer. They instead increase the rate of DNA damage and repair and compensate. In fact at the sublethal dosage levels, it is not really clear what level of gamma is dangerous. Injestion of any isotope however carries increased risk 3. In an atmosphere gamma just doesn't travel that far, certainly not through a heterogeneous substrate. As I stated early tinting a 1 inch thick piece of plexiglass with a small amount of lead suffices to knock out almost all gamma radiation. Of course a mixture of metals is more effective but why do you need to, a heterogenous construct like the hull of such as ship will capture most of the gamma without any extraordinary effort, a good soil is compose of complex material. 4. In the area surrounding Chernobyl in Belarus there was a study done to find out why there was an increased level of radiation effects in some areas versus others after the fall-out was at ground level. The ground in these areas was radioactive, but that in-and-of-itself was not sufficient to increased risk of blood pathologies. Observers went to several farming communities, what they found was there was almost no risk in people ambiently exposed to radiation, but when people worked in the fields if they gathers stubble and burned it there was much higher risk. As it turns out the risk came not from exposure to the volatile salts liberated into the air by the piling and especially the burning process, and the risk turned out to be almost entirely an inhalation risk. 5. I used to work with so much radioactivity that if you sat a one side of a room (Geiger counter running) and me at the other with a , the radiation source I was working with while facing the other direction could ping that meter on the x/100 scale. It used to burn my finger where I held it for several days on occasion. Gamma is not the danger that you think. READ Second. Objects don't suddenly stop in space unless they collide with something mass. Rollers do not need bearing replacement they are only present to deflect imbalances, they otherwise are not moving because they are not touching (magnets are maintaining position, not the rollers). If the internal cylinder needs servicing just bring it to a stop Third. By building reasonably size communities it is not neccesary to build thermonuclear power plants, particularly since the outside hull is moving at a reasonable speed on can have Solar Panels. Fission power plants can be shielded, but the bigger problem is that they have maintanence issues so scrub these until better plants. If you spin a ship at 1g on the outside edge then adding more solar is problematic because of the g-forces. At 0.1g you can increase the area point at the sun by 3 fold. Forth. We have already discussed the fact that you do not understand cosmic radiation. Hydrogen is the best absorbent, you keep talking like its a gamma ray, its not. A cascade is just that, there are as many types of cosmic rays as there are clueless posts here by dreamy-eyed martian 'colonist'.(http://pdg.lbl.gov/2011/reviews/rpp2011-rev-cosmic-rays.pdf) Each energy level and type (proton, alpha, lithide, carbide, . . . ) can spawn different types of radiation. Antimatter in cosmic rays are rare, just as in the rest of the universe. You cannot keep shielding everywhere within a structure in space, weight is your enemy, more so than the radiation. BY having a sufficient amount of secondary absorbent (space and low mass nuclei) there is increased probability of reducing the KE of the secondary rays. As stated early 3 cm of water suffices to remediate primary radiation, so at that point you have only secondary radiation and space is your best friend. "Understanding Space Radiation" (PDF). Lyndon B. Johnson Space Center. NASA. October 2002. Retrieved 2012-07-25. FS-2002-10-080-JSC Galactic cosmic rays are the dominant source of radiation that must be dealt with aboard the International Space Station, as well as on future space missions within our solar system. Because these particles are affected by the Sun’s magnetic field, their average intensity is highest during the period of mini- mum sunspots when the Sun’s magnetic field is weakest and less able to deflect them. Also, because cosmic rays are difficult to shield against and occur on each space mission, they are often more hazardous than occasional solar particle events. They are, however, easier to predict than solar particle events. "Understanding Space Radiation" (PDF). Lyndon B. Johnson Space Center. NASA. October 2002. Retrieved 2012-07-25. "FS-2002-10-080-JSC" The production of multiple secondary particles by cosmic rays under thick layers of lead has been studied with coincidence counters and with a cloud chamber. Part of the coincidences obtained under 15 cm of lead is attributed to groups of particles of atmospheric origin associated with extensive showers. The other part is due to a local effect produced in the lead by single penetrating particles. Among the particles emitted in these processes, some have the penetrating power of low energy mesons. Multiple Secondary Effects of the Penetrating Cosmic Radiation at Sea Level. Available from: https://www.researchgate.net/publication/243691638_Multiple_Secondary_Effects_of_the_Penetrating_Cosmic_Radiation_at_Sea_Level [accessed Nov 12 2017].Multiple Secondary Effects of the Penetrating Cosmic Radiation at Sea Level. Auger and Daudin, 1942 Finally I am not going to deal with your what ifs, since you don't seem to read the literature. The primary component of cosmic rays is Hydrogen (540 parts), Helium (:26 parts), Carbon (:2.2 parts).(2. AMS Collaboration, Phys. Lett. B490, 27 (2000); Phys. Lett. B494, 193 (2000).3. T. Sanuki et al., Astrophys. J. 545, 1135 (2000)). The primary secondary CR from carbon collisions is oxygen not nitrogen and positrons is rare (10E-4 per secondary electron/beta) and is only observed in the >10GeV range. Antiprotons, antideuterons, and antialpha particles are rare with proportions of secondary cosmic radiation below 1 in 10 million (K. Abe et al. , arXiv:1201.2967v1 (2012)).

Isn't it time we put this thread to rest?

Water has a freezing from 6 millibars upward of 0'C Chlathrates will freeze before CO2 CO2 has a freezing point at 6 mBar of -110'C Methane has a freezing point of -182'C Nitrogen,Oxygen, Helium and Hydrogen all freeze at tempetures below -200'C The first ice that one is likely to find, and in particular seasonal ice on Mars is likely CO2 and CO2 chlathrates (because the H20 vapor pressure in martian atmosphere is close to zero) As one moves north or as Winter progresses there is likely to be a layer of CO2 on top of the chlathrate layer. The purest reservoirs of Martain ice a in the deepest layers of martian ice that fill permanently iced depression in the polar regions. These are probably mixed with martian dust.

How much iron do you need, space craft are made primarily of aluminum, not iron. Weight is the enemy of space travel. Beta is a skin hazard (risk of burns and skin cancers), Alpha can be skin or consumption hazard. The problem with your idea is that you think Iron is the best block agent, its not, the best blocking agent is liquid hydrogen. Your argument is akin taking a boomerang on an eel fishing trip. I repeat gamma is not the primary concern, cosmic rays are only radiation because of the velocity differential between the elements and the targets. If not for this they undergo electron capture and become hydrogen and helium. They are fundamentally different from gamma radiation and the method of remediating them is fundamentally different. The are fundentally different not because of the resting qualities but because of two KE, relative velocity and rotational velocity. The critical point that unless you get them to cascade before they reach the living target, no amount of lead will protect you from the radioactivity they generate within your body. Coaxial centrifuges are not neccesary in requiring bearing because of zero gravity one can use induction (https://en.wikipedia.org/wiki/Electromagnetic_induction) to maintain cylinders without solid bearings, In fact one can spin the inside structure by applying spin to the inside structure in the opposite direction, energy would be applied to resist the force of friction. When the structure needs to be move, just cancel (i.e. do nothing) and once they coast to a stop open the induction circuit and make the coarse change. ( You might want to drain bathtubs and sinks first). Induction circuitry has been used in the aquarium industry for a long time where the impeller needs to be in water and no-one wants to pass current through the water. They only requirment of a bearing less rotor is that you need a method of automatically balancing the rotor or risk the rotor glancing off the sides. This can be prevented by having rollers limiters along the sides at both ends of the cylinder. Of course entry and exit from the habitat cylinder would have to be from the top and bottom and people would have to climb to the habitation layer. The air mass in the cyclinder will be common and circulated between the two forcing air in from the top and exiting at the bottom.

And there is no adequate power supply to extract it.

There are many reasons why ION does not work with Oberth. 1. Typical power supply is solar, for most oberth effects of planets outside the earths orbit: a. The planet is between the bottom of the hyperbola and the sun. (no Light) b. there is not alot of light to use to begin with. c. there is generally not enough battery or NPG on board to have a significant effect. 2. RL is not KSP. (mu is the celestial's specific gravitational parameter) a. An OP 35kw high power light weight producing a piddly isp of 3500 generates this 2 * 35,000 w * .8 [efficiency]/ (3500 * 9.8) = 1.6 Newtons. b. If we assume an ION drive that has unlimited power passes at the minimum safe orbit it has a velocity close to that escape velocity. For Jupiter that would be ~60,000 m/s (see below). If we also assume that burn can be no longer than 20 degrees, thats about 400 seconds at that velocity. 500 seconds at 1.6N. 800N can be generated (at the cost BTW of 17,500,000 Joules of electricity) c. lets assume our space craft weighs a ton, that translates into 0.8 dV. d. So lets assume we reach jupiters SOI with 2000 m/s of velocity. this equals SKE of 2E6 J/kg. The potential energy is 2*mu/rorbit,min = 3.539E9 (this is the amount of energy that is borrowed and needs to be returned on exit). The exact velocities at minimum are: 59393 which is slower than the escape velocity because we are approaching Jupiter from a minimum safe orbit and not the designated surface (which is ephemeral at best). Lets say that our dV is added at 70% efficiency relative to adding all dV at 59392 this means we go from 59392.1352923818 + 0.56 = 59392.6952923818 velocity (the decimal places are kind of important. This translates to SKE at maximum velocity of about 1763746127.04686 and 1761712867.29429 is returned to Ju[iter as SPE as the ship leaves. You might be surprised that the space craft is now traveling 2016.35 m/s, 16.35 m/s faster. However this is not reality- land. As the ship passes behind jupiter is it using (most probably its NPG) at around 500 w for 500 seconds is 250,000 j. Thats about 1/80th the power it would need and it more or less would gain a fifth of a meter per second. So lets say the spacecraft had a 100lb nickel metal hydride battery capable of 2000kW of power production max for 500 seconds (again thats a fantasy, the battery would drain more quickly). at 1 million joules it would only run that ION drive at full for 28.751sec. HOw about the theoretical 40,104,000 J/kg https://en.wikipedia.org/wiki/Lithium–air_battery a theoretical discard over 500 seconds that does not destroy the battery (unlikely) would have enough power for 2.5 ION drives (25kg instead of 10, 15 kg more) increasing the amount of velocity imparted to 2049.6 on exit a gain of 50 m/s. Lets compare the same situation with a 10kg RCS thruster and 90 kg of fuel and ISP of 200. That generates a dV of 188. Using the same parameters of efficiency that RCS thruster would impart 2432 dV of exit addition bringing the rocket to 4432 m/s. This is the reason you don't use ION drives for Oberth. If you have RCS thrusters on board the dV you gain in the end beats the very high ISP of ION drive. That does not negate the other uses of ION drives (as demonstrated in the exploration of Ceres). It is also the reason they don't carry mega-OP batteries on board. The critical issue of ION drives is that the use a high density power source (nuclear) or external power (solar) to increase ISP such that the straitline dV for burns (such as at a systemic pe) can take days or weeks within that 20' burn window you can have very high ISPs and conserve alot of fuel (3 to 20 times as much fuel as the best chemical rocket engine). The very thing that makes ION drives useful for interplanetary travel station keeping makes them useless for Oberth effects. Here is the logic. THat oberth effect around Jupiter achieved 2234 dV, a good ION driven setup can have 10000 or 15000 more dV than a comparably weighted RCS based propulsion system. How many oberths does the RCS need to achieve before it reaches its destination, 7 or 8, this is unlikely. OTOH that rcs system does not need solar to run and does not have to deal with declining power in NPGs. 1-10 kW is nothing when if comes to ION powered systems. Its trivial power product and not worth the added effort relative to solar If solar is available. I have read up on the russian fission based systems. More or less they abandoned the systems. To many problems relative to solar. Again a 35 kw system at the low end of 3500 ISP _only_ produces 1.6 N of power, at the high end of ISP produce only 0.55 N of power. This is the reason people are not taking VASIMR seriously, it does not have a power supply. Plain and simple. Alot of weight and nothing to power it.

That future, I don't believe is far away. I am interested in Mercury, it has potential that others seem to ignore. There are two basic lines of electric propulsion systems. The first line are the solar driven systems. I expect that the application systems will slowly creep up in efficiency and plateau off around 60%. The research systems will always lead these in efficiency but they are generally not applicable for a variety of reasons, what follows the leading edges are non-OP systems that are better than application but are more reliable, durable or productive than the best efficiency models. At some point we may reach a performance of 1 kw/meter. This really does not solve the overriding problem with ION drives. Here it is . . .the reason to use ION drives is because for the dV that they can produce over their lifetimes both the units and their fuel is very light weight. The problem is that the power supplies are not light weight, and the more fuel efficient the drive the heavier the panels have to be. The second problem with ION drive also is related to their fuel efficiency, that is the issue of linear drop in thrust with increased ISP, that problem can be solved by increasing the number of drives. Some critiques about VASIMR are correct, the high power (35 kw) ION drives can have about the same fuel efficiency as VASMIR, but you need alot more of them (6) and these drives start to have a wide foot print. To have 210 kw of ION drive now you need 630 m2 of solar panels at more than 1kg per square meter. There are spatial limitations on the application of solar panels. IT can be done if you find a significantly high space port to launch from, if your launches lower MaxQ and delay passing the sound barrier (i.e. wasting about 1000dV of fuel 'hoovering' over the launch pad) delay the gravity turn. This means that such a space craft really needs to use its ION drive early in its life to poke its way into deep space. Once it gets inside the orbit of Venus such ships can shine with power the other ships don't have, but close to Mercury the panels need to be turned to prevent over heating. Solar power ION drive are really optimal for ship nonperishable between planets in which if it takes 5 years to deliver supplies in low orbit about Mars, no-ones going to have a heart attack. The other line is nuclear based propulsion. While NTGs can feed excess power to ION drives these generators are few and far between now. The fission based reactors (classic steam based design) are not very reliable, and more they are optimized for space applications (less-weight) the less reliable they become. They never have produced much power in space, they have leaked. Some have proposed using thermocouples instead of a steam/water cycle. This in not very efficient and there is alot of waste heat lost. If you need a source of heat for another reason it might be worth it. We could see something like a fast breeder reactor or waste fuel heat generators (Purified reactor waste) using thermocouples, you really are no better off than solar panels. From all the fission reactors I've seen I've never seen a composite generator that was better than a contemporary solar based power generation. There may be a need for electric power in the outer solar system, in which case fission is the only viable ION drive power source. The problem with fission in the US is that scientific institutions are running like mad from application of radioactivity in the research and engineering areas. The NRC has gone overkill in many aspects making the users lives especially difficult. The problem is in the on ground implementation of a fission reactor. It would almost have to be done by the US-DOD research arm (which Bush the second basically gutted for the two Wars) and plopped into a rocket, as a module, just before lift-off (Plug and prey astrotechnology). Then finally there is fusion. I don't think fusion will be light weight system under any circumstance. A space ready fusion module would at least need a Falcon heavy to get it into space, no accounting for the remainder of the rocket, such a device would need many ion Drive (100s) at 35 kw to push the massive reactor through space. The beauty of fission reactors is that they are completely non-radioactive until you flip the 'on' switch. Then they become a neutron factory. The bad part about fusions is that its longest living vapor-ware product of the modern age. Everyone seems to be waiting for the neeto-trick innovation that makes it works flawlessly. I wont be alive when that happens, but lets hope that they can get something working. A fusion reactor can drive all aspects of the ship, from ion driven RCS to main engines to computers to science, etc. An altnerative is fusion pulse engine in which you basically don't try to sustain a fusion reaction, just get it going for a moment, throw in the ejecta, let it all blast out and cool and repeat. This may be where the next century of spaceflight finally brings fusion in. All the Mars dreamers will be left figuring out how to fulfill themselves using solar panels. This is why I always have to ask the question, what is your power-supply for extracting water from Mars, or smelting metal in space, these operations may take more weight in solar-panels than just bring water from Earth to Mars. My Personal opinion is that near and mid future space is gonna be all about making panels lighter, work better and greater efficiency on the application side. @YNM, there is a ion drive metal that is very cheap to store and found in great abundance in asteriods (magnesium). You can basically have screws sticking out of a pole and twist the metal onto the screws and use a robot to remove magnesium and feed it into the ION drive. This solves many problems, it does not solve the problem of how to get robots and smelters to asteroids and how to power them once they get there. @ChrisSpace That 7000 dV assumes continuous thrust, if you pulse the ion drive as it passes through pE you can get it up with much less, the problem is that you waste alot of time. For such a system to work well we need a higher power density battery. It may be the case the graphene based batteries of the future can provide that storage density. @wumpus IT serves a ship well to have some chemical propellant to pulse dV going through oberth. But the whole thing about ION drives is that their ISP is so high you might not choose to use oberth. Oberth effects are really for rockets using monopropellent (hideously low ISP).

Lead would be a biproduct of asteroid mining just like any other metal. The amount of lead added to plexiglass shielding is surprisingly small and effective. Like I said gamma radiation is the least of your issues, the soil in such a structure would suffice to block most of the gamma without any particular effort. (In my layout I allow 3 meters for substrate so that you can grow healthy trees). Secondarily the humans I would place in an interior centrifuge so that protecting them is a priority. Plants are much more tolerant of ionizing radiation that humans are, in fact, they grow better with a healthy dose of UV. The other little known fact is that, due to more rapid gamete replication, human males germline is much more susceptible to the effects of ionizing radiation relative to females, so protection of the germline largely involves protecting the males, making females more suitable farmers. Just to debunk one of your myths. https://en.wikipedia.org/wiki/Health_threat_from_cosmic_rays "- Spacecraft can be constructed out of hydrogen-rich plastics, rather than aluminium. " Right now we are talking carbon-fiber which has moderate amounts of hydrogen. The soil of such a craft would have both water and CH hydrogen in the form of composting organic matter (Cellulose). A loose soil serves two functions. 1. to interfere with primary cosmic radiation creating secondary radiation and slow that radiation down. 2. to interact with secondary radiation and causing additional cascading at lower energy 3. to provide a space whereby secondary radiation can auto-decay. http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/cosmic.html Don't assume that just because something is protective on Earth that it also protective in space. Most of the radiation exposure on Earth comes from Radon gas which is an alpha emitter (adsorption hazard) and potassium (beta' and radiation hazard) which is a gamma emitter. While alpha and beta emitters in space are largely derived from cosmic radiation that can decelerate within the human body spontaneously producing radioactive isotopes that then decaym creating risk. To reduce risk in space what you really need it more space and elements that can undergo interferance and rapid acceleration (Hydrogen, helium, lithium) . A primary cosmic ray is composed of mostly hydrogen and some helium, they are traveling so close to the speed of light that speeds are indistinguishable until a cascade can be measured. The original particles leave their source in very violent circumstances and the rotational status is equally energetic. Looking at the combined energies it might appear that the radiation is moving at the speed of light, in actually the spinning protons (or alpha particles) are creating an electromagnetic field that is maintained because of the speed and lack of interactions. Thus cosmic hydrogen and helium are differentiated from material sphere that surrounds the earth. Upon crossing the psuedo boundary the longer distance electromagnetic/spin (magnetic field) interactionns slow c-hydrogen down, direct interactions also slow them down. The less massive the target the more energy it gains and the more energy the cosmic radiation looses. The rapid alteration of nuclear spin results in the ejection of particles (secondary) some of which interact more with the material mileau and some that do not (autodecay). " Attempts have been made to model how much ordinary matter would be required along their pathway for collisions to produce the observed population of these light elements. One study suggested that it is about equivalent to passing through 4 cm of water."-http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/cosmic.html. Secondary consmic rays are compose of high energy subatomic particles like muons, some are charged and can undergo interaction with charged materials loosing their energies and slowing them down where autodecay occurs. Others (like neutrons) will travel until they hit an unsuspecting nucleus. As we can see the need for radiation protection is not so much the exterior level but interior, between the 'slowing down material' (Water, hydrocarbons, etc) and inhabitants. Having a vessel within the vessel, properly spaced from primary and secondary remediation is the best protection from product radiations. That design is the least practical of the designs that I have seen.

The perchlorates are stable because of the high pH of martian soil (in the same way NaOH in chlorox makes bleach stable). If you acidify them they become unstable. You can force them to decompose. There is a climate forcing model working on Mars. We typically think of climate forcing as being man-made or inconstant (such as global warming or the procession of Earths orbit and axis). IN the case of mars the force created by the suns UV radiation and winds force hydrogen off the planets surface. This the cause an number of downstream effects, but primarily the loss of trapped heat (moisture buffers temperature drops at night). Because the retention of heat of the poles is insufficient the temperature drops below the sublimation point of carbon dioxide (which is an acid, forms H2CO3 in water). This has forced acidity away from the equatorial regions and to the poles. Since there is still CO2 in martian air all you need is to hydrate the CO2 (of course above 0.4'C) and then acidify the perchlorates. https://en.wikipedia.org/wiki/Perchlorate#Chemical_properties Note the single unit rise in redox potential once H+ is added. The end product is Cl2 which on earth is a bad-thing, but on Mars its something you would toss into the wind and steal the remaining water. I should point out that the vapor pressure of CO2 in martian atmosphere is not that much different than Earth, so you might want to find a place that has dry-ice nearby to expedite the process. Again, this is a concept of how to recover water, it is not a procedure or practice. For that to occur alot of gory details need to be worked out. No complex chemistry on Mars is going to be easy, you don't have a lab full of Ph.D.s sitting around writing papers on how to extract water from crude perchlorates at Martian STP. The most important problem is that Martian soil is loaded with Na2O. For those who are not familiar, this is what happens when you decompose Sodium hydroxide. You are going to need alot of CO2 and chemistry to turn this into Sodium Carbonate which can be set aside. There are alot of proto-basic chemicals in Martian Soil, to unlock those perchlorates these compounds have to be dealt with first. Its going to be a fight all the way to retain the catalytic water used to extract the chemical you want. The fact that the soil is so full of Na2O informs us on the prospects of life on Mars.

Yes and there are glaciers in the southern hemisphere of this planet. The _random_ probability of you finding one someplace useful for all other reasons is next to zero. You seem to like to confuse the idea of possibility with probability. Probably anywhere that has suitable energy source is bone-dry. There is a possibility that there are places that have subsurface brine and diurnal sunlight exposure all year long. That does not mean they are suitable for colonization in the same way that building a colony on the side of a steep mountain glacier in Peru is a suitable place to build a colony. For carbon fiber you can embed lead into the structure of the fibers (as is done with plexiglass to make gamma shields) as much less weight per gamma absorbent. In space your primary concern is not gamma radiation anyway, its cosmic radiation. Mass is not particularly the issue, cosmic particles shatter on impact, but they are traveling at the speed of light and produce exotic matter states that will decay and cascade over distances, so or even Aerosolids are suitable if properly designed to capture the subparticles that are generated. Not the least bit concerned with gamma radiation in any soil covered cylinder, its not a concern. If you are talking about Phobos as a source of materials, then I ask you again, where is the power supply for doing all this metal working? Phobos d(hv) = 0.4 Earth d(hv). If near earth it takes 50,000 square meters of solar to accomplish something on Phobos it would take 125,000 square meters of solar panels. The surface of neither Phobos or Deimos are stable.

Tidal forces exist not only where there is water but where there is inertia. The ground is less malleable and slower to respond than water but it is none the less responding. My problem with presenting concepts as facts is they almost never get their basic facts correct. There is much more that goes into making such structures than what immediately meets the eye. For example, an Iron clad structure a km across, how do you weld such a beast together in space. Remember that the first SS design was rejected because is required a prohibited number of space walks. Welding a structure like this together would have the same problem in spades. Of course now you have robots. But the problem is even a robot would have difficulty on the thickness of some of the welds. My point about the formation of the earth, when you start talking about putting celestial body magnitudes in space your are talking about heat of formation energies on the celestial scale . . . . .where is the freaking power supply to do this? This keeps coming up for everything, before you tell me something is doable, tell me where you got the power to do it from. If you say well we have to wait 20 years for fusion power, I'll accept that but tell me how much power and how heavy the reactor is going to be. I'm really tired of people making god-mode arguments about power. To achieve 5000 cubic meters of iron from an asteroid you need 20-25 MJ/kg. At 5000 kg per cubi meter this would require 625 terraJoules of power over a year ~20MW of power (50,000 sq.meter of solar panels). This is not the only power problem but a major one. Of course size has its benefits, but compromises have to be made. The first of which is that the size of the walls and the internal structures are going to be a function of reducing the amount of required material for a variety of reasons. For example if you can make 1 device of growable area, you can make 4 if each has half the growable area. . . . . . . Im not against building such things in space, but lets be reasonable in presentation of concepts, moon sized 'ark-ships' with earth like gravity are not feasible. The second thing is that plants don't really need a g of gravity, their needs are driven by light, its humans that need the gravity. So why would you stress a whole ship at 1 g when you can have a smaller cylinder inside reserved simply for satisfying human and animal needs. By reducing the rate of pressure vessel spinning you reduce the needed amount of material for the pressure well and you reduce the e=hv effects of spinning something in curved space-time. To support a human you need to have roughly 100 times the biomass of plants, its several 100 meters per human. Where as for humans you only need 30 or so meters, by reducing the area devoted for human survival you greatly reduce the mass required. This is also beneficial to the humans because they are on the very inside of the ship and all the walls and are least exposed to radiation (except when farming).

Lets say your are in earths orbital path at L3 so that you have the same amount of light density as earth. A spinning disk as has been presented would have a wall area of radius * 2 * pi * height. If you have a transparent central opening by which light feeds into the structure for growth (although now-a-days the choice would be LEDs) and that opening is half the radius of the disk with a cone shape reflector (0.25 * radius^2 * pi) And you want say 1/4 the sunlight density (24 hours per day). The height should be approximately 1/8th of radius. The use of Iron as case markedly limits the build size, thickness needs to be 5 to 10 times thicker than carbon fiber. The other problem with Iron structures in soil is corrosion, if you place something like that in space the intent is that it will last 1000 years or more. It does not need to be carbon fiber but its does need to be something resilient to the moisture/acidity/oxides in soil. Rate of oxidation increases as the inverse function of pH. The other thing about carbonfiber. You can place the device on a spindle and spin it laying out the fiber, for something like a km size disk welding Iron plating several feet thick is nearly impossible.

You forget about space-time. The inside of the centirfugal space craft is entirely in a non-inertial reference frame. Anytime you use the word gravity or artificial gravity for an object in stasis with a root object you are talking about non-intertial reference frames. E = hv, thus there is energy within the cycling of forces even small forces of gravity that act against the yield strength of objects. The design is not only silly but its wasteful. The thickness of the wall of a cylinder under constant pressure increases linearly with the diameter of the cylinder, it eventually reaches the point were no amount of material can keep the structure from blowing up because the material itself under centripetal force astronomically adds to the pressure. dV/dr = f(r2) therefore the increase in wall thickness . Given the strongest construction materials a cylinder of 10km radius and 50km length would need 2.7 trillion kg of carbon fiber casing. A cylinder with half the internal diameter (and half the cylindrical inner surface area] would use 1/4th the material. A cylinder with 10th (1 km diameter) would use 1/100th the material. If we set the limit at 1,000,000 kg (1 / 2.7000,000 the material) of material and set the length of the cylinder at 10 times the radius, then the cylinder of length 57 meters in radius (572 meters in length) [internal surface area 194801 meters at top of substrate] of will have a wall thickness of 0.0028 meters thick. Its surface area to weight. The weight to surface area is 5.2 kg/meter of wall mass. For the larger (10km radius x 50 km length) its 850 kg/ meter of surface area. Again, what source of material do you know of in space that can produce 2.7 trillion kg of carbon fiber (That is 103 million F9 launches). Sure I can set a practical limit for carbon fibering a hull and spinning the inside surface at g force, but there isn't a serious space engineer that would have propose such an incredibly wasteful monstrosity. Just go to spaceX or BlueO and propose building at trillion ton space habitat .. . . . .I wanna see the look on their faces. Here again another hand waving argument. Reaction wheels do not work in real life like KSP. In addition something rotating in orbit about a point mass has one edge that has a higher outward force than the other side. As a consequence it wants to flip over. In real life reaction wheels in space need RCS or ion drives otherwise they spin to max and stop working. I fear that Dal wants to play whack-a-mole with us. When we defeat one of his arguments he whips out another and we whack it down. None of his arguments are particularly strong in their merits. I believe he equates quantity of argument with quality.

Let me help you then @DAL59 The Martian surface gets 43% of the light than received from Earth. To generate a 24 kilowatt of power per day on Mars (assuming 10 hours of usable sunlight) at 30% panel efficiency (1.444 kw/panel-day) you need 16 one meter^2 panels. However because the latitude is 70' at this site you either need 45 panels or to space the panels out Over > 45 square meters. Mars tilt relative to its trip around the sun is 25.19 ' which means minimally this site goes dark tor for several months per year and has no solar power at all. 90-70 = 20 degrees. The difference is 5.19'. Comparable sites on Earth (Resolute, Canada) have about 3 mounts of darkness (1/4th of a year). 0.25 Martian Years is about almost half a years, For the purpose of solar power generation though it would be closer to 7 months without power. In the summer 4 months you would have power 24/7. Thus you probably could not have a permanent settlement on this site without some kind alternative power generation. Remembering that Mars does not have O2 shipping oxygen and hydrogen to power generators would be excessively expensive (since the amount of oxygen required is 2 to 5 times that of whatever fuel you drop). At least 6 months a year this site would need a Nuclear power generator.

Thats not an answer.

Your power supply for living at the poles?

Just to repeat there is virtually no water vapor in Martian Air. The air is too cold and too low pressure. Water was attracted to the Martian poles in the form of CO2 clathrates, because of the lack of sunlight water locked into the poles is more stable. I think some folks are getting confused, seriously, about water. Yes there is water (brine) on Mars, but it does not exist everywhere, and where it exists is for a short time being pushed up from some geological process is then oozes right back down into the substrate. Its not a matter of this is a nice spot, lets scoop up water. Its more like yuo have to anticipate where the brine will flow, capture as much as you can, then convert it into pure water. Nighttime temperatures of mars is -100'F close to -73'C. The vapor pressure of water at that temperature is 0.2562, the vapor pressure of Mars is 600 Pascals, the baseline proportion of water in Martian Air can never exceed p=0.00427, it can increase in the daytime, but over much of Mars there is simply no source for water. At 60% humidity (highest being at night) is p=0.000252 (in other words less than 2% of the mass of the air). Again 60% humidity is not likely near the equator. The pressure on earth 101,000 Pa in which 0.044 moles per liter. On Mars this would translate to 6.818x10-8Moles per liter. This translates to 0.0000012444 grams per liter of Martian air. To get a liter of water you would need to dehydrate 816 billion liters of air. In that process you would have to separated from several more magnitudes of toxic martian dust that you would also collect.

https://en.wikipedia.org/wiki/USS_Thresher_(SSN-593) I suppose that the critical limit of a submarine a feather dropping on the floor could cause an implosion (or overheating Ice cream machine on the interior wall of a submarine). The general opinion with regard to the Thresher is that the submarine program was being mismanaged with proper management the number of catastrophic events decreased so management strategies are something that needs to be take seriously even if they involve ice-cream machines. This I think is in line with the critiques of ISS management, that for a more safe and independent deep space voyage the systems need to be more robust. The problem with the Thresher was they were trying to do nuclear age stuff but with a legacy of WWII class submarine, which was a great improvement compared to early 1942 (Namely grossly malfunctioning torpedos).