PB666

If it will make you happy I will say Yes, maybe (I can't say on a keyboard, hmm I wonder if its because the keyboard is in a black hole and words don't escape?).

fixed it, You assume that these planets obtain all there mass when they were formed, what if these planets acquire mass from inner solar system and collisions with comets and other orbit crossing objects after they formed, the the planet mass to moon mass would have been initially lower. Are we measuring planet to rocky core? I think we are measuring apples to oranges.

Atomic weapons killed 150,000 Greed&Overpopulation&Ignorance will kill billions. Where from civilization erupts a plague that spreads, each cure morphs a beast with even more heads.

Copper can be completely recycled. Recycling glass is not profitable, since sand is basically granualized glass, there is little difference in energy cost. Plastic is barely recyclable, the problem is that there is not one kind of plastic, for plastic recycling be useful the user has to separate plastics by composition Polyethylene is basically thick wax, (oil at higher temperature), the polyethylene can be carefully recycled back to polyethylene plastics. the polycarbonates and the like can be ground into small particles and used in a variety of applications, these tend to lighten soils. They can also be burnt, reused, no. Cardboard is about 100% recyclable. In our household we recycle all the cardboard except the milk containers. This is profitable because cardboard takes alot of landfill space, and landfill cost money. Aluminum is mostly recyclable. The heavy organics (peels, rinds, ends) I recycle.

By far the relative abundance of hydrogen is greatest in comets. that goes for practically all the volatiles, as comets are largely composed of volatiles. You might get it from dirt back asteroids, but fused asteroids made of heated metalics are going to be very hydrogen pour. So I have to say that short period comets are the best source beyond a doubt. All it takes is the effort to pull something like 67p into a stable orbit (which basically tou tug it a little and let jupiter and saturn do the rest) is the best source for the volatiles. There is water on Mercury, but since you made the effort to go their that water would be also split for other duties. Near earth orbit asteroids are not good sources of hydrogen or water, there is some carbon dioxide but mars moons are better sources. So here is the basic problem with your thinking, which you should have detected before saying im doing it wrong. Moons, Asteroids, etc have alot of aluminum, nickle and silicon on the surface, but very little water. On the moon or mercury this water is precious, because this will be needed for the colony, and is only found in select places, like the caps. This is not the kind of water you want for making rockets to explore the system. This is the kind of water you want for building green houses and domestic use. Most asteroids will be wasted effort to get water, but are good sources of metals. The short period comets are the best source, have the lowest delta-v but require some effort and lots of time. This is where things like high efficiency solar panels and ion drives come into play. Even fusion if it ever comes about. Another strategy is to simply capture a comet, protect it from the sun and place it in a mars/earth orbit where it can be exploited, or even better place it in earth L2. Mercury is good because of simply the huge amount of power, you can set out voltaic potentials and capture plasma, giving you all the power you want. This is good for the development of Nerva, which Mercurians would not have any problems with. You don't have to worry about using water, save it for domestic use and skim protons from channels in mercury to use in rockets. The other thing about mercury is you have another advantage you can use solar voltaics and rf/laser power to basically accelerate your Nerva propellant to high ISP ION drive exhaust velocities. Mercury is more than about water and/or surface protons, its about power. For example a magnesium based ion drive that could develope say exhaust velocity of 1000000 m/s or even 10000000 m/s would have a solar usage zone after lift-off from mercury of millions of miles, some d/v to push its orbit in while it accelerates, it has 60 days of solar power at 4 to 8 times that of earth (provided solar panels). We can imagine how much dV that could development for travel to the outer system. HYdrogen is a poor propellant for Vasmir (storage is inefficient compared to other gases and solids, metalic magnesium is the best storage form), the best ion drive propellants store as solids (magnesium). Vasmir we don't have a power supply for, unless you are in mercurian orbit and high heat solar stability has improved and power to weight ratios increase by 10 fold. The thing about bring comets into stable orbits and covering them from solar radiation is that these are huge concentrated reservoirs of volatiles, but you have no cost at all for launching product and landing. If you placed one of these in Martain L2, its basically there for your mars moons needs. Sure you can invest 100 fold more effort trying to get hydrogen from Mimos, but you still have to launch it, were as on L2, you don't have to spend the effort and you don't have to pay much launch cost, and you can spend a tiny about of dV to send it to L1, or package it up and send it to earths L2, were it can be used. Again all this would be done utilizing the argon (comets have argon gas also) and other minerals you capture on the comet to basically run your ION drive, when and if fusion power ever becomes feasible. For a mercurian polar-crater colony we don't have to wait for fusion. There is also the potential of hunting down dirtballs in Jupiters orbit. Freddy your problem is that you tend to gloss over the problems in space colonization, you think that some webpages handwaving solution is a solution. Space colonization is hard, the best sources of resources are often the hardest to reach, the ones within reach demand such an energy cost to extract it makes expansion incredibly difficult. Your colonies are going to leak and lose material. But then you want to use water (2H2 + O2) as a launch fuel. To much competition for too little resource. When they say there is water on the polar moon or mercury, they don't mean lakes, they mean basically frost accumulated in between the dirt on the surface. When they talk about water on Mars, its in saturated solution with other minerals. H20 is volatile in the inner solar system, its stable on earth only because of Earths size (gravity) and bound atmosphere, and temperature. Simply using a drill is some of these locations to bring up dirt will supply enough instability that water basically vaporizes and blasts away into space. For 2H2, O2 based engines you need big sources of water, not trivial sources. You need to be able to find great sources of resources, so that a little waste does

Taking lots on how many more posts until this thread is closed. my lot is pi. :^).

There is power conversion on the front end to, since it is unlikely you could build solar panels to achieve a decent output for a photon drive the next choice in Nuclear (and no I do not accept direct current production nuclear because the current production is laughably low), which means you do have to have a heat sink to generate power. Have you seen my interstellar fusion driven ship? 1/10th scale model. big radiator fins on the sides, prolly not enough. Anyway fusion as a power source does not really exist yet.

As in you suffocate 30 seconds later, not to mention the pounding headache the CO2 gives you, and of course the hydrogen sulfide throws a few punches, Or are we talking about rapid dehydration due to the lack atmosphere. Or maybe the crushing heat and pressure of mercury venus,

Efficient photon drives don't need heat sink, althuogh the photons destination is likely to be much lower energy than its source. Solar sources of electricity effectively don't need sink, as per thread on Solar based ion . . . . .the wiring may have a source of heat that has to be dissipated.

This thread just begs for a political war.

Interesting, my count of habitable exoplanets is 0. Pluto is potentially habitable, provided we have really great compact fusion reactor.

you need your givens first, what is the exact radial velocity (omega) of the earth and what is the exact radial velocity of the satellite. w (omega) = v/r the earth rotates 2pi radians over 86163 seconds so omega is 7.2922 E-5 radians per second. Sat is 1.193E-3 rad/sec which means that if it is traveling west to east it will linger for about 207 seconds. The last element we don't know is that we know is north coordinate now, but we don't know what it will be after it has traveled 13.3 (+ correction) degrees east south eastward. Thats a bit more complicated, we know it crosses the equator it is 90 degrees from its current theta, We should be able to apply the cosine function and it maximum northern position to guess that it will be 27.63 N, which means it is about 30km south and ~1,600 km. If you are answering this for school the probably want 3 significant digits, the reality is the answer is only good for about 2 digits.

87.91 minutes means he is rougly a few 100 miles up because of that you cannot see 180 degrees. If we assume up is 0 degrees, then when the satellite is at 90 degrees he is signalling through the earth at 45 down. So it has to do with altitude. So lets assume its the earth. mu for earth is 5.9722E24 * 6.67408E-11 = 3.985E14 period = 2pi * SQRT(a^3/mu) 5274.6 = 2pi * SQRT(a^3) /SQRT(mu) 839.47 = SQRT(a^3)/SQRT(mu) 16757890306 = SQRT(a^3) 280826887538650000000 = a^3 a = 6548567 the radius of the earth is 6,371000 ( 6,353 km to 6,384 km ) so this means elevation is about 177560 meters. Thus the parameters are in earth orbit (clarified) his velocity is now calculable = SQRT(mu/r) = 7800 m/s. (how damn convinient) The view of his satellite is obstructed. While this seems difficult its actually not. There is a theta that is where cos theta = 6,371000 / 6548567 therefore the Arccos (0.9728) = 13.37 degrees. THis assumes the reciever is at ground level, and the ground is absolutely flat. This means he can recieve that he can recieve a satellite in 26.74 of 360 degrees. If the period is 5274.6 seconds he can send and receive for 391.8 seconds. You need to know how to calculate the Specific gravitational constant for point masses. See above, You need to know how to convert fractions into sin or cosine using an ArcCos or ArcSin (Acos or Asin) function. You need to know how many degrees are in a period. meh, if you cant figure it out with what I gave your doomed, :^). Since a degree is roughly 69 miles or about 100 kilometers, that satellite is like right over your head, so you will only be in contact for another ~200 seconds. As it moves to the edge of the range the, Here is how you know. 7.8 km sec * 196 seconds is roughly 1600 miles, the difference from its current N position is about 30 km due north of your position and the satellite is moving along a rougly east-west trajectory. Therefore it will disappear about the same time whether it passed directly over head or 30 km north or south, however due to is inclination and the difference in position you may have lost or gained some fraction of seconds. But BTW don't forget the earth surface is also moving about 1000 miles per hour at the equator and cos of 28.' x 1000 at your position. So if the sat is moving west to east across the sky, it not moving as fast away.

Well if the propellant cost were cheap the political will would be much greater. The problem is that right now all propellant needs to be lifted off the ground and slung orbitally at 7800 meters per second. dV = SQRT(2*orb. alt*g + u/r). Since even NASA is talking mars lander is a separate issue than the Mars flyby issue then I think we are talking about multiple missions for one Mars landing mission, we are talking lots of propellant. Again NASA is underfunded, no doubt about that but if you are underfunded to you do one very expensive landing mission or some much cheaper robotized mission. you mean 6,728 seconds (ISPg) exhaust velocity of around 67000 m/s

Before you can have a mothership, you first have to have a method to send a milligram from [whatever] between yourself and another distant (extrasystemic) objects.

Wiki pages - These are the basics for understanding how things work in interplanetary exploration. momentum (https://en.wikipedia.org/wiki/Momentum) [delta]V (https://en.wikipedia.org/wiki/Delta-v) [Tsiolkovsky] rocket equation delta-v budget Oberth effect Specific impulse (Isp), effective exhaust velocity Ellipses and orbits (used to be discussed alot but most everyone uses resources now that make this easier) https://en.wikipedia.org/wiki/Conic_section Defines circular, elliptical, parabolic and hyperbolic orbits. eccentricity, e The following are defined in the conic section major axis, minor axis latus rectum resulting in the following key orbital terms semi-major axis (a), semi-minor axis(b) and semi-latus rectum(l) mu (greek m, looks like cursive roman u) - is the Celestial gravitation constant is Mass(object) times the Universal gravitation constant. Keplers laws of planetary motion (must read) The orbit of a planet is an ellipse with the Sun at one of the two foci. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.[1] The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit. Note that the wiki pages are pretty fractured for information so there are many pages not mentioned here that will be required to predict velocities orbits, intercepts, etc. Hohmann transfer orbit Electric Propulsion systems (https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion) Ion thruster (and the equivilents) Ion thrust equations F = 2*η*P/(g * Isp) Laser propulsion, Photonic Laser Thruster, Photon rocket. Bussard ramjet Nuclear Propulsion systems Nuclear pulse propulsion NERVA Antimatter-catalyzed nuclear pulse propulsion These are the pages, I do not advocate any of these technologies except those I lend support for in the threads. The links to the threads above more than cover the theoretical transport systems (Warp drives, black hole drives, Fusion based electric thrusters)

Major outbreak of the transxenobiotic insanity virus, stay away, no cure.

These topics are not of the Interstellar film either, which probably means you are unfamiliar with the meanings of black-hole drive, alcubierre drive, fusion-electric propulsion. Which is all the more reason you should read these threads and do a wiki post before engaging in conversation.

There are several recent threads that deal with the topic of interstellar travel. The topic has been exhaustively discussed here.

Steel by definition is not pure, steel contains at least Iron and carbon. When you think iron think rot-iron. Presumbably even off-world most natural elements will be found in crystals, so isolating the crystals first helps A. Degassing - A process that requires the addition of heat close to the denaturation point of the crystals in a seal chamber with a vacuum pump differential gas collection a. presumbably the gasses have different liqification points, a still would collect these and separate them according to boiling point b. the next process is to sublime gases that do not liquify, like CO2 Crystal separation a - n. separated crystals would be place in helium driven tubes where they are sent to a devoted process module for that crystal Dust (ultrafine grain processing) anything that is not an identifyable crystal or gas. B. Differential crystal processing some crystals would be better treated with a strong monovalent acid like HCL some crystals would be better treated smelted other processes C. Sub processeing - these are processes that apply to what you have obtained from the first. Lots and lots of process modules, some need to be connected by lines to their destination (production modules, life support, bioproduction, etc). For example a module that makes stainless steel might make plates, curved plates, column stocks). A robot would come along and take the column stocks to a production machine that make nuts, bolts and washers, once these are made the bot then takes a container to the factory, where these are loaded into a robotized assembly machine. The plates would be taken to bender where the are curved and welded into structures, eventually welded into structures outside of the facility and attached. D. Dust extraction. Probably feed into an ISRU. Again ISRU is basically a (I only care for these things cause I am not going to build a space colony purification process). If your goal is to extract everything useful from a clump of dirt, in the end you probably will have decimeter cubed blocks of nickle and silicon wafers dotting the surface around your processor (you wont need as much of these as supplied)

[facepalm]

Uranium cannot be recycled so its a potential candidate. Splitting things into atoms for the most part is impracticle. Many elements are siderophiles which mean they will copurify with iron, if you want to get these you have to use a differentinal extraction process. The job of the smelter is basically to separate siderophiles from slag elements and gases, although the addition of graphite aids in the creation of steel (if you are interested in the rare elements this is not warranted at this step) and limestone the separation of slag. Slag can then be crushed into a fine powder and extracted with hydrochloric acid and thus leaving that acid stable silicates and solubilizing the alkali metals. These are then treated with base and the polyvalent cations generally precipitate leaving Li, Na, K+ chlorides in solution. Putting these back in elemental form is impractical, it requires electrolytic reduction, or excessive heating. Lithium is useful for making lithium ion batteries, sodium is useful as a system coolant (its vapor point in much higher than water). The smelter is designed to force disequilibrium between transition metals and alkalis such as the metals degass and become nonionic. To separate the siderophiles requires the acid based oxidation of the metals. This means that the metal needs to be pulverized into filings, treate with acid (like sulfuric which also acts as an oxidant, adding potassium dichromate would speed the process up) and bubbling pure oxygen into the mixture. Once oxidized you can neutralize the solution and do differential extraction. The vessel of choice for this is glass-lined, since glass is stable to a 300' c and is chemically stable up to about pH 12, but some care needs to be made to remove fluorine from solution early in the reaction. The washing elements need to be recycled, this will require an electrolysis to produce chlorine gas, sulfate can be precipitated with calcium . . . . . . . You have alot of process chambers that need to be created, laser 3-D printers is an end process, you have to get its reagents into forms it can handle. Some elements could be delivered in copper lines, glass lines with teflon connectors, or in cartridges. This means that some process modules can be separated and use common lines for application, while others need to juxtapose on corridors that bots would need to traverse, picking up cartridges, taking them to other locations, cartridges clean and prep, cartridge return. Presumbably you could use a host of tunneling lasers to pound the surface of dirt to create gases of all the elements, but they will sublime on contact with anything, including your lasers and the equipment.

Just like KSP shows more energetic hyperbolics with decreasing orbital period times. You ever here mark twains extrapolation of the lower mississippi growth rates. When you enter the event horizon, time is still moving for the rest of the universe but for you it has stopped, from our point of view what you see in the hole in meaningless because you have merged with a singularity, the information you add to the hole cannot be retrieved until the last bit of Hawkings radiation is emmitted. IOW you cross the event horizon and trillions of years later the black hole explodes in high energy gamma, and that was you. I think that schwartzfield radius and event horizon efficiently reduces the complexity of everything to atoms and passing the event horizon atoms are probably reduced to their subatomic energies in their time frame, and then reduced to pure energy at such time they radiate.

the reason I think bonafida space agencies don't have a colonization plan is that they are not sure how or that they can sustain them. Mars has a feature that the moon does not have, on the moon you can, given cumulative space docking land about any thing on the moon with a GPS system in place or even lorance like system, land just about any piece of equipment. Therefore we could dig down say 100 feet, or given time we could even reach the solid warm center of the moon and chances are you would find alot ot uranium and rare earths. That could justify a moon colony, say what you like about Nuclear energy, it beats the crap out of coal, and if we had a great supply it could pay off. But you would be building SRBs to get you back to earth with your load, which means small SRBs. As far as I know the space shuttle is the only vessel that could carry a good size load of uranium back to earth and make it profitable. Mars is a different story, even if you had pure uranium-235 (which is particularly dangerous) or pure platinum it would not be cost effective to ship it back to earth. One of the basic problems is that most board of directors expect now that an investment made today will pay-off in five years, this is not the case, you can't expect a 5 year payoff in a mars mining operation. The problem with mining economics off-world is that compared to other planets the earths surface is dynamic. This may also be true with other planets, but we have the whole collision thing that occurred after the earth had considerably cooled, then the biological epochs of earth and the fact that we have liquid water has created alot of deposites where killer contaminants are reduced. So you get iron deposits that are low silicon, you have gold deposits, etc. And there is alot of earth and 2000 years of prospecting to find these things, made more easily so by having breathable air and food and water availability. The second problem is that you set out on a 5 year mission to get platinum off of mimos, and year 3 in your mission someone finds a rare combination of palladium-tin and krypton does the same thing for 1/3 the price and you are SOL. Alot of the rare earth stuff is going to be functionally replaced by graphene, which is a cheap on earth as it is anywhere in the galaxy. The so called smart material, in which some very special property is caged and oriented by carbon-nitrogen is going to take alot of the pressure off the rare elements and make things stronger and lighter weight. Imagine that when you make a magnet, its almost impossible to get all the domains to align, but then you put a single atom in a cage which then orients the atom, and you can basically have cages on a string which you weeve into a cloth and connect together like a diamond. So the reality of interplanetary commerce is that its primary motivation is future growth off-world, what are future off-worlders willing to pay for something. If its not future growth and if someone isn't funding off-world growth, commerce does not make sense until there is growth, chicken-egg argument. So then the question is why NASA is right now only talking about a manned flyby (and later maybe a landing and reading the Orion page that sounds ify . . obviously we don't have a mars colonization plan because we do not have a manned mars mission plan with details). Because that is what they think they can do, they may have other robotic plans for mars and its moons, but everyone is interested in what their manned missions are. I would be more interested in do they intend to land on mars moons and bring back samples. The big payback from the moon. . . . seriously we could have sent five clueless missions to the moon where they tripped over themselves. . . . . all that would have still been good with the return of a single moon rock, even 40 years after the mission science papers are still being written on the rocks. So I think primary mission is to get samples from Mars, and if that is too hard then get rocks from the moons of mars, and from there we analyze and see what can be done. I could imagine some crude ore processing unit where tiny little nanobots pick little crystals and separate them one by on onto conveyor belts that then go to a chemical processing bath and separates the elements of the crystal, which is then made into pure samples. All of this would be tested on the mars rocks on earth before being sent to mars for practice. Someone made the point about why be in space, why should government support a space program. Other than being the heaviest payback welfare system, a space colonization system is a form of insurance against things like global nuclear war or asteroid impacts. These are the benefits now, but with good space science the colonization could have its own internal economics.

To be blunt here in the disclaimer, there is simply no possible way to replace all the elements that would be required to build and replicate space colonies. The key factor here is that with really efficient ION drives and solar panels we could ship the most rare elements to where they are needed. The basic assumption here is that if you have electricity that any form of an element can be converted to any other form. You might want to have a smelter, a greenhouse, a chemistry facility, milligravity, etc. Lets start with the basics. Hydrogen - storage form H2, H20, Pt-H - While hydrogen is the most common elements in our solar system, it largely resides outside of earth in inconvenient places namely the Sun and the gravitationally inaccessable gas giants. Its density in outer solar systems objects is higher then inner solar system objects (except the gravitationally heightened sun). The sun produces hydrogen, lots of it, problem is to get close enough to harvest it the level has already fallen. There is far too much need for hydrogen to bring it from Earth or other gravity wells. Hydrogen is the most basic reducing agent, it is the smallest and compounds in which it is found have the highest volatility and lowest viscosity. Because of its high energy per sp, sp2, sp3 and ss bond/mass hydrogen is a major component of rocket fuels, particularly first and second stages. It is also a component of fuel cells. Because of its volatility hydrogen is first lost from planets that a hot and/or have no atmosphere. Hydrogen H20 - water, required for life, electrolysis, chemical synthesis, air conditioning, greenhouses NH3 - Ammonia, required for fertilizers, used in air conditioning and cooling systems. CH4 - Methane, one of the simplist fuels, can be used to make higher organic compounds and ammonia. CH3CH20H - Ethanol . . . . . synthetic intermediate in the making of synthetic oils and other fuels. H2NCRHCO2H - Amino acids . . . .Required to make protein, R (CHOSN) containing side chains H2SO4 - sulferic acid . . . . required for life, to hydrogen to reduce sulfate is an essential process for biological oxidation HCl - hydrochloric acid . . .for the extraction of metals from high complexity ore. Required for life, a precursor for some refridgerants, for the preparation of some electronics. etc. H3PO4 - phosphoric acid . . . for life, for extraction purpose, fertilizer. Option 1. Mercury exploit, charged particles from the sun pound mercuries surface and slowing them down, using a pulse charge system protons and electrons can be directed into a set of channels where they can be pumped and collected. Critique- landing on mercury challenging,bringing the electrods, channeling the surface, etc more challenging. Option 2. Comet exploit, comets are occasionally thrown from the kuiper belt into the inner solar system where they degas, wrapping and heating the comet could capture these gases. Comets are generally are in high dV orbits relative to earth, stablizing those orbits so they can be harvested is difficult, stable zones are devoid of sustantial solar electric power, a nuclear electric power plant may be required. Option 3. Lunar option, problem is that the level of hydrogen in the form of sublimated materials is probably not enough to sustain a lunar colony, let alone expand. Carbon - Storage form graphite, diamond, organic compounds, dry-ice. Outside of the earth is one of the most frequent elements found in gases of non-gas giants with atmosphere in the form of CO2 and methane, also present on comets. Carbonates are also found bound to metals in asteroids and other soils. On hot planets like mercury and venus carbonates are driven off of metal into the atmosphere. Carbon also acts a reducing agent, although under some circumstances is can be an oxidezer, it is a general thicken of fluids, fluids with high carbon complexity tend to be more viscous and less volatile, diamond as a good example of the effect of branching sp3 bonds. Carbon CO2 - required for life, greenhouses, blood chemistry, concrete and basically stone based construction. CH4, Ethanol, amino acids, oils, see above - see hydrogen =C= (sp3) diamond, required for high end devices and for drills (embedded diamond dust) =C- (sp2-p) graphite, found in graphene and other modern graphene based structures. component of carbon-fiber, light weigh building materials. Option 1. Moons of martian planets Option 2. Short perioid comets. Oxygen - is the primary oxidant, diatomic oxygen (02) is rare where photosynthetic life is absent, the most common reduced form of oxygen is water, but oxygen is also a component of CO2 and is more stable in rocks (asteroids and rocky planets than hydrogen), it is also found in comets and is a small component of solar wind. Option 1. Moons of martian planets Option 2. Short period comets. Option 3. Kuiper belt planetoids and trojan objects of Jupiter and Saturn. Critique - transfer orbits take generations. Nuclear is an absolute requirement. Nitrogen- Nitrogen is a key component for life, it is also a major component of hyperglolic fuels as well as solid fuels, therefore it is almost essential to have nitrogen for deep space operations where main engine fuels may not be required, it is frequently used with oxygen, so demand for nitrogen also increases demand for nitogen. Nitrogen is a required component for atmospheres. It is relatively volatile, not as easily trappeds as carbon and oxygen. Option 1. Short period object Option 2. Kuiper belt planetoids and trojan objects of Jupiter and Saturn. Aluminum- Aluminum is a major component of light weight space craft, it is a fairly common element, but is hard to mine except from certain sources. Aluminum is the ultimate storage for rocket fuels such as for SFRB that might be used for landing ventures on planets. Option 1. Lunar harvesting. Option 2. Asteriod mining Option 3. Moons of martian planets Option 4. Mars. Argon (Xenon) - Xenon is widely used as an ion-(hall thruster or roses by any other name) however it is extremely difficult to find off earth, with solar efficiencies improving and Ion drives reaching higher ISP, the argon storage problem is less of a problem, many ion drives can burn Argon and Xenon. Argon is basically found whereever atmospheres are found, it tends to be a bit more common in the outer solar system, likely because of atmospheric loses from the inner solar system. Argon also prevents fast spoilage in artificial atmospheres. Essentially we need cold atmospheres were vapor velocity at ground level + solar wind is not sufficient to blow argon away, this represents objects very far away from the sun. Boiling point is at 87.302 K Option 1. Harvesting of just outer system planetoids, atmospheric purification Option 2. Harvesting of the asteroid belt objects. Option 3. Harvest from mars. Silicon - Silicon is very heavy, it is found in nature as an acid of Si04 which undergoes polymerization under pressure to form glass, silicon is a component of electronic circuit boards, glass windows in habitats and in space craft, silicon is a major component of asteroids. Silicons most important role is in building photovoltaics. Option 1. Asteroid mining Option 2. Lunar mining Option 3. Mars moon mining. Copper - copper is a major component of refridgeration systems, water piping, it is used because of its ease of repair compared to aluminum, as a water carrier it is fairly resilient to corrosion if the water is kept close to neutral and some divalent cation like calcium hydroxide, or finely ground calcium carbonate is added to the water supply. Copper is the primary metal used in electrical systems, it does not have some of the pitfalls of aluminum wiring. Namely there is little or no voltage on brass connectors. Option 1. Asteroid mining Option 2. Lunar mining Option 3. Mars moon mining. Nickle, Iron, Chrome - the various metals are all components of metals that are used in space craft, the alloys of steel are made from carbon, iron and other metals to obtain strength and heat resilience, these metals are required to build structures and more importantly efficient rocket engines. Metals are widely available in the inner solar system. Option 1. Asteroid mining Option 3. Mars moon mining. Option 2. Lunar mining Calcium, Magnesium, Sodium, Potassium, Sulfur, Chlorine. Important for life, but also useful in other processes magnesium is a solid fuel convienient for ION drives when argon is difficult to find, lithium and sodium can be used as heat exchange liquids in nuclear power stations. Sulfer and chlorine is used in chemical manufactoring, Calcium is used in making certain forms of sheilding. Option 1. Asteroid mining Option 2. Lunar mining Option 3. Mars moon mining. Platinum, gold, paladium, tellurium, uranium. Solar panels are not a neccesity but in the inner solar system they are the most cost effective means of electric power generation. The problem is that core components of these systems are made of not so easy to find minerals such as cadmium and semimetals (tellutium, gold). Platinum and paladium are used in fuel cells and for hydrogen storage, and is required for electrolysis of water into H2 and O2. The more stable metals are more resistent to acid solubilization that most metals, consequently some acid based purification is often required for extraction. Option 1. Asteroid mining Option 2. Lunar mining Option 3. Mars moon mining. Rare Earths. The primary use of rare earths Option 1. Earth sourced while other sources are found. In creating stand alone colonies what we see is that sourcing of elements is not quite as easy as on earth, if we remove earth from consideration one might have to travel the mercury/kuiper-belt transfer in order to find the best source for minerals What is also means is that somewhere along that ellipse needs to be a facility to process the crude material into refined starting materials that can be used to manufacture the various objects. There are alternatives, magnesium might be used instead of xenon or argon in ion drives, solar panels are made of different semi-metals (metaloids), different sources for magnet metal, multiple alloys can roughly generate the same functionality. The processing to final products for some of these items is a very extensive a popularly cooperative process, which all adds weight in space to do the same thing. Some things, like working with cyanide or other poisonous intermediates are to be avoided. This all translates to a fairly long period of dependency on earth. The question was asked about the stand alone profitability of going to mars, lets strike mars and ask any exploitable body, the answer is it would take a long time for the process to become profitable because, relatively speaking the energy invested to acquire the basic ingredients for building anything (complex structure) other than a solid block of nickle covered with silicon glass are spread widely across our solar system. We need to find more efficient and roboticized ways of covering these great distances. The other thing is that here on earth, the highest price you will ever pay for transportation is the fuel it takes for a 747 to travel from say Perth Australia to Los Angeles California. Where the cargo payload is say 10% of the weight of the fuel, most often you are paying 10% or 20% of the total cost of a good in transportation, once you start compositing structure, it would be as if every part has to be transported from Perth to LA 3 or 4 times over. Despite the high expense, its doable with an eye on conservation. If I recieve a tin of fresh fish eggs from Perth, I can throw the tin in the trash, not so in space, the tin is recycled, the CO2 is recycled, the N in the urine and sweat is recycled, the water is recycled, Poop would be recycled. To say that not-for profit needs to be involved emphasizes the point that the various connect the dots that we need to make a stable space-alone system work is not 'connected' not even started. It takes government and not-for-profit donors to establish the first connections, in fact all the connections, even if hair thin, for the commercial space ventures to be profitable for things like landing on mars or moons of mars. It is to say that once science is doing, well, science on many bodies that we will find alternatives to resources that I have stated above, so that maybe we dont have to mine Kuiper belt objects for Argon and Helium. But here again we may find something even more valuable harvesting hydrogen from say mercury (like maybe an abundant source of tritium and dueterium) or kuiper belt objects that makes it highly worthwhile to have Mercurian polar colonies or generational ships to the kuiper belt. The point is lets not put the cart before the horse, first we have to go to asteroids, see what it takes to mine them, go to comets, see what it takes to bottle their gases and package the metalics and metaliods. Go to the low gravity well moons and see what can be used. Space X can get your robot into space, but then its the government that needs to fund the science aspect of the mission, if they manage this time, instead of leaving a lander base on the moon, they leave behind a long duration robot that continues to work, drilling, preparing, etc for future landings, then you have begun the process of making and keeping a connection. [Note: I came to write this post after creating a rather massive colony on the pole (sink hole crater) of Moho, I chose moho because it takes the most important element out of the game, energy, infact, once you get your factories running full steam, there is too much energy and not enough negative energy. I have launched a rather big self modded space factory that allows for gilly back forth building of anysized object I can dream of, which means I come to Moho with basically everything, no longer thinking about kerbin (the only thing kerbin supplies is kerbals, adam and eve). But then I wanted to built a sort of reflective colony on moho from scratch on moho. What I came to see is that the tools provided feel well short of the task, a metal drill and a smelter create metal and rocket parts. The reality is that such a smelter would require calcium and create slag and gases, those gases would need to be separated into elements, the slag would be separated into elements, and thus many of these process need their own chemistry unit, that is not in the game, or in the add ons. Ore is composed of elements which can be separated into purified or enriched molecules, which can be broken down and reformed into what we need to build colonies. After sitting down and writing out a short list of the facilities need, I can to a short list about 50 or 60 parts that can be added as units to the colonization system modules - this was the answer to the profitability question - why private companies are not hopping over each other to go to Mars]