RuBisCO

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  1. Rail guns would be able to accelerate a tiny package really fast into a orbit that would crash back down into the moon (from behind) if it does not have thrusters and fuel on it to circularized its orbit. Military rail guns can shoot a several kilogram tungsten dart at 2.4 km/s out of a gun that is only a few meters long, that would be more then enough to enter lunar obit assuming it has thrusters on it to circularize its orbit. The problem is we want to throw something bigger then a few kg, and it also has to withstand g-forces of > 100,000 G out a rail gun! A magnetic mass driver (without all the arcing/melting parts of a rail gun) say 100 m long throwing a 1 ton package, to 2.1 km/s would put it under 4500 G: that is way better then the rail gun, plus with some very good flight controls a package could come back from orbit and fly into a mass driver pointed the opposite direction and decelerate back to zero, bring cargo down (assuming it can withstand the deceleration) or at the very least recycling the package, and all of its orbital energy can be stored in capacitor banks to launch the next package! Such a mass driver system would be able to bring cargo up and down much faster than a bean stock, but would require some propellant in maneuvering and orbit circulation fuel. Obviously humans still can't be used with such a system. Another idea that would require less cabling then a bean stock is a rotovator: a space ship either flies straight up from the moon or is held there by a tower, and a spinning swing many kilometers long in orbit flies over and picks up the ship, swings it into lunar orbit above it. If it brings down cargo of equal mass no energy is lost, otherwise the swing loses orbital altitude that would need to be boosted slowly by an efficient propulsion system. If the swing is long enough and spins slow enough then it can lift humans with g-forces low enough. I calculate a 100 km long radius rotovator would put the end point at 2.74 G, at 200 km long it is 1.29 G and at 300 km long it is 0.82 G.
  2. Oh the LOX would be a tiny fraction of that, in fact there would be a huge oxygen excess, to dump I guess. Yes the ratio is far better on Mars, because CO2 is easier to get there by far than water is (just suck it out the martian air, digging/minning equipment is needed only for getting water), unlike the moon where the ratio of water to carbon is more than 20:1, hence why the moon makes sense to have a hydrolox economy and Mars makes better sense to have a methalox economy, hence why Elon is betting on hauling methane from earth to low earth orbit to refuel ships destine for Mars, although it could also haul fuel to cis-lunar space to landers to the lunar surface and back and likely would be competitive at that for many years before a hydrolox economy on the moon is started up. Problems with hydrolox is that hydrogen requires double stage cryogenic cooling which is heavier, needs more energy and has yet to fly in space. The colder a cryogenic fuel is the harder it is going to be to transfer and move about. Methane and oxygen have the nice feature of both being liquids in useful temperature and pressure ranges, they can be stored together with a uninsulatd bulkhead between them (Warning: do not mix together, if mixed forms extremely unstable explosive cryogenic liquid, they will explode if even a bright light is shined on them!) Which means one set of cryogenic equipment that needs to go no lower then 50 K can freeze both down to their freezing points. Obviously hydrolox requires thermally separate fuels tanks (for long term storage, so far common bulkhead tanks have been done for hydrolox for weight saving proposes but for short missions), more insulation, oh and much bigger tanks: liquid hydrogen has the density of cotton candy, while liquid methane near its freezing point has the density of gasoline. Huge fuel tanks are not so much of a problem if your not going to fly through atmosphere. There is another solution, one I have not touched on because it is so underdeveloped, or rather has only had fragmented development over many decades: Nuclear water rockets. It requires orders of magnitude less equipment to just mine water, purify it, refreeze and pile the unwanted extra volitiles, and just run it through a nuclear rocket engine, then to crack water into hydrogen and oxygen and cryo-liquify them, extract extra hydrogen from the extra volitles, etc. The first problem though is that to get a nuclear-water rocket up to the same Isp as hydrolox requires operating at temperatures that have yet to be achieved for nuclear engines, we are talking about the need for rotating cores in which the nuclear fuel gets so hot it becomes a goo that needs to be held in place by centrifugal force. The second problem is water at extreme temperatures of ~3500 k is very corrosive, much of the gas is radicals of oxygen and hydrogen at that temperature rather then water, and squeezing that through pores of nuclear fuel that already has the resiliency of putty at that temperature is likely an engineering nightmare. Alternatively nuclear engines on water could be run at much lower temperatures, much more reliably and well developed technologically, but at significant cost to ISP, at an ISP of 200 s, 3 times as much water will be consumed getting it to Low lunar orbit then if we burned it via hydrolox. Worse even if we had a nuclear rocket engine that could do 500 s Isp with water, that is only peak Isp, cooling down the nuclear rocket because of decay heat will mean significant propellant lose as lower Isp or just boiling off after it has landed. Nuclear rockets also need to carry a cooling system to deal with the decay heat without constantly boiling off propellant, which means big heavy radiator panels, but this comes at the advantage of being its own power source with each nuclear rocket engine likely providing excess dozen of kw of electric power at all times. Other advantages of nuclear water rockets are that water is dense and easy to store, meaning smaller and insulated tanks. There is an option for getting materials off and on the moon without costing any fuel at all, not even in maneuvering propellant: a bean stalk. Because of the moons low gravity and lack of atmosphere a space elevator made of Kevlar could haul ice from the poles to L, the problem would be the hauling rate: this system (http://www.niac.usra.edu/files/library/meetings/fellows/mar05/1032Pearson.pdf) claims 340 tons a year to L1, but would require thousands of tons of cable and counter weights in cis-lunar space, I calculate that a 100,000 km long ribbon climbed at an average speed of 15 m/s would take 77 days! Considering the mass of each climber is under 1 ton, there is no sane way humans would be transported via this means, cargo though sure.
  3. According to my calculations the hydrogen sulfide in the lunar permafrost would produce 15.7 kg of sulfur per 100 kg of water mined, oxidize that would mean it could store 15.7 of oxygen as SO2, 23.6 kg of oxygen as SO3 and 31.5 kg as SO4! Remember we have an extra 9 kg of oxygen after make proper ratio hydrolox from water and the volatilizes, so the sulfur could easily take it all and then some! Carbon we can store as carbon, nitrogen we can store as NO2 in lunar soil as nitrates, and sulfur we can store as sulfur or any range of SOx in lunar soil as sulfates to consume all extra oxygen. Also I am starting to think against N2O mono-propellant. The most efficient in propellant by mass for maneuvering thruster fuel would be hydrolox, but would have problems if running on liquid oxygen and hydrogen, boil off problems, or limited thrust on gaseous oxygen and hydrogen, which would need to take propellant from the main tanks and vaporize and compress them with electric pumps and heaters. Lets assume hydrolox maneuvering thrusters with Isp of 400 s on a 25 ton space craft, for 50 m/s of maneuvering delta-v that comes to 321 kg of propellant, with N2O at 175 Isp it comes to 739 kg of propellant, an extra 418 kg. But the N2O is a much simpler thruster system, single lines instead of two, no vaporizers or pumps as it is self pressurizing, none the less I doubt that would make up a mass difference of 418 kg, also the hydrolox propellant does not need a whole separated fueling up system as N2O does and having access to the main tanks means a lot more maneuvering delta-v potential.
  4. Well that is another problem, if we are going to extra metals from lunar mining to build actual things, we are going to have a huge excess oxygen problem, I'm thinking of saving nitrogen by reaction of NO2 with lunar soil to form Metal nitrates ([M]O + NO2 -> [M]NO3) I'm starting to think at a certain point we are just going to have to dump oxygen, either that or use it in electric propulsion systems off the moon. The carbon and sulfur are easy enough to store as elemental solid, in piles for future use someday, or not, but not the nitrogen and certainly not the oxygen, only together can as NO2 and then as metal nitrates can oxygen and nitrogen be stored and that is nitrogen limited, which can barely handle the excess oxygen from water processing to hydrolox. We could consider freeing out CO2 in the craters, just open storage of CO2 as dry ice, but I fear it will subliminate, and again not much carbon to work with. SO2 though we could probably freeze in the craters and it probably would not subliminate, yes you are right all the extra sulfur we could store excess oxygen as sulfates! Again I don't think we should burn metal as propellant, it is too energetic to make out of lunar soil anyways, much more useful to make things with it instead. Combined with lunar mining of water and hydrogen sulfide we can store the extra oxygen from reducing metal out of soil as sulfates.
  5. NO2 can be used later with 0 kg of hydrogen used. Alternatively we could use HCN, react it with lunar soil to get back water and metal cynides, the metal cynides we can dump or used for metal processing, but then we still have an excess oxygen problem.
  6. Waste of hydrogen. NO2 will store fine enough in lunar soil, just heat it up to extract it.
  7. I thought of that earlier but it is more efficient to use every gram of hydrogen for propellant in hydrolox, also N2O has a higher Isp then hydrogen peroxide and is more stable, only problem is the thrusters will run way hotter and are not as well developed as H2O2 thrusters which are nearly 100 year old technology by now. I did find a paper from 2007 that developed a N2O thruster: https://web.stanford.edu/~cantwell/Recent_publications/Lohner_Scherson_JANNAF_2008.pdf Anyways burning the extra nitrogen from lunar mining reduces having to store it in tanks in the craters, again I'm thinking in a "use every part of the buffalo" philosphopy, it might be more efficient energetically to just dump many of these as gasses. What nitrogen, carbon and oxygen is not used by lunar colonist and overfills the storage tanks just dump into space?
  8. So I finished by calculations on how much hydrogen we can get from the volatiles in lunar ice: For every 100 kg of water we can make 11 kg of hydrogen and 88 kg of oxygen, but we need only 66 kg of oxygen for 1:6 ratio rocket engines (the RL10 is 1:5.88 for example) at 1:8 our specific impulse takes a 4% hit and combustion temperature increase by 250°C, so it is simply a waste and wear on the engine to burn off the extra 22 kg of oxygen. For that 100 kg of water we get 33.4 kg of other volatiles, of which 2.8 kg of which is hydrogen and 3.9 kg is oxygen, of which 1.6 kg of that oxygen is in CO2 that we can just store as dry ice in the craters of perpetual shadow, so only 2.3 kg of oxygen then. If we extract all that hydrogen and are to burn it in a 1:6 engine it requires 17.1 kg of oxygen, leave just 7.5 kg of excess oxygen. If we take the ammonia and run it over a catalyses with that oxygen we rapidly get water and NO (Ostwald process), consuming 5.7 kg of oxygen, if we further oxidize it by cooling the freshly produced NO with water and excess oxygen, we get NO2 consuming another 5.7 kg of oxygen, so clearly we can make ratios of NO:NO2 to consumed all the left over oxygen, the NO we can store in the craters in pressurized tanks as a passive cryoliquid under lunar shadow, NO2 we can store in lunar soil as a solid. The NO and NO2 we can use later as a source of atmospheric gas, by endothermic reaction with catalyses at low pressure to get N2 and O2. So the end products extracting hydrogen and oxygen from the extra volatiles are sulfur (we can dump that in piles anywhere on the moon) carbon soot (again dump anywhere on the moon) and NO2 (react with lunar soil to make solid metal NO3 that we can dump anywhere and heat up later to extra the NO2 if we want) and finally anywhere between 0-10.6 kg of NO we need to store as a cryoliquid for future use. Some of that N we could use as attitude control and docking propellant as N2O mono-propellant, thus further reducing the need for NO we would need to store in tanks and more NO2 we could store passively in nitrite enriched lunar soil. Converting NH4 and O2 to N2O and H2O (water we would recycle via electrolysis) can be done in a single step with proper catalyses. So for a moon mining economy I propose hydrolox (of course) and N2O mono-propellant for attitude control and docking. And burning aluminium as fuel does not have the Isp of hydrolox. While metals like iron can be reduced with hydrogen gas (or carbon as on earth, because coke is cheaper then hydrogen here), aluminium and titanium would need molten salt electrolysis and halogens... then again maybe not. Theoretically with enough heat and hydrogen gas any metal can be reduced, but eventually you are heating up to 4000°C and your processes is grossly inefficient... unless you are using solar heating or something, then its just mirrors and free energy. Alternatively there is metal-carbonyl chemistry which could work wonders for both extracting iron and nickel and 3D printing, but is so damn toxic and flammable here on earth, but in the vacuum of space without oxygen to burn might have great potential. Under a metal-carbonyl atmosphere you can 3D print metal with a laser and a surface to beam on out of thin air, and you can tailor the alloy as your print by changing the atmospheres composition. All you need to do is run carbon monoxide gas over iron or nickel oxides and you can produce metal-carbonyl which you can collect via distillation. Does not work for Titanium or aluminum though.
  9. I agree on asteroid mining being better then lunar mining. The only problem is that the delta-v is much lower at the sacrifice of many year launch windows from NEO to/from earth. Moving a large enough NEO to earth to be viable as a fuel source would require an absurd amount of propellant. Lets assume a NEO that weighs 1 million tons (~100 m wide C-type asteroid), lets assume we use plasma-oxygen electric thrusters (using waste oxygen from refining that asteroid) with an Isp of ~1500 s, to move this asteroid just 50 m/s and perhaps swing by the moon to achieve an lunar gravity assist capture into high earth orbit, would require 3400 tons of propellant. Better would be to mine it at site via automated/AI mining and have it manufacture return ships, ideally solar sails out of cheap aluminium/magnesium refined as co-product of extracting rare metals, that can bring back those rare metals back to earth for profit, or solar electric propelled hauler that can bring thousands of ton of water and methane for a space economy. Solar sails require no propellant and can be reused and go just about anywhere in the inner solar system if given enough time, to Mars for orbital mirrors, etc, but are limited in that they can't carry much, which is fine if each is moving a few dozen tons of gold-platinum to earth in an entry capsule, but water is going to be many orders of magnitude bigger haul.
  10. Starship (I want to go back to calling it BFS ) has its own propellant economy based on bring liquid methane and oxygen from earth up. A moon based propellant economy would be based Liquid hydrogen and oxygen and be incompatible with Starship. I think Elon has the right idea though, in that the time to develop a moon based LH2/LO2 economy via ULA and Blue Origin, he will have his Earth based LCH4/LO2 economy already running and sending crews to Mars, which is his primary target, not the moon. Considering the infrastructure needed for a moon based propellant economy, Elon is going to have many years maybe even many decades of lead time, there will even be a time where he would be more economical landing on the moon and back, then the competitors, with him landing the equipment his competitors need to build and lunar propellant economy that would only be able to out-compete him in cis-lunar space.
  11. This is mining water from a polar crater that is in permanent darkness via using a mirror to beam light down into it, this is not mining water at the equator or any random place on the moon. There is billions of tons of water in permafrost in the dark craters on the poles of the moon. The LCROSS mission found 5.6% water frozen in the soil when it impacted a rocket stage in a shadowed crater on the moon's south pole. https://www.researchgate.net/publication/47520015_Detection_of_water_in_the_LCROSS_ejecta_plume
  12. Well the architectures are all over the place in design, ULA thinks this: I'm thinking simpler: just have a hauling robot go down into the dark craters, dug up a few tons of frozen soil, put it in a enclosed tank, and haul it back up to base on a "peak of eternal sunlight" at the south pole, there a processing facility can do all the work of heating it, boiling out the water and other goodies, make stuff out of the left over dirt, etc, a kind of "use every part of the buffalo" philosophy. As for Starship, that needs methane, which means carbon, and there is over 1 order of magnitude less carbon (As CO2, CH4, C2H4, CH3OH, etc) frozen in the polar soil than water. Thus LCH4-LO2 fuel economy does not work without a much more dominate LH2-LO2 fuel economy utilizing the water first. If we suppose that everyone ton of soil has 5% ice, and for every ton of water we get 40 kg of carbon volatilies, of which we can make into 53 kg of methane at a cost of hydrogen from water, then for every ton of lunar soil we get 0.265 kg of methane, and starship takes at least 240,000 kg... so a very big hole.
  13. Another problem I found, and sort of solved: The oxidizer to fuel ratio problem LH2/LO2 rocket engine does not work on 1:8 H2:O2 mass ratio that is in water, rather ideal ratio is somewhere between 1:6 and 1:5, these means we have excess oxygen to deal with. It turns out though that lunar ice is more then just water, according to the LCROSS mission spectral data, for every 100 kg of water, there was 16.75 kg of SH2, 6.03 kg of NH3, 3.19 kg of SO2, 3.14 kg of C2H4, 2.17 kg of CO2, 1.55 kg CH3OH, .65 kg of CH4, in short for every 100 kg of water there is an extra >31.2 kg of volatilies, most of which have hydrogen. If we oxidize all these with the extra oxygen not needed for propellant we get back more hydrogen then we need, we end up with an oxygen deficient! The SH2 and SO2 we can burn and convert to sulfur soot and recover all the hydrogen and oxygen, the organics we could pyrolysis to carbon soot and get back all the oxygen and hydrogen. Only the nitrogen we would need to convert to NO stored as a liquid in tanks in the permanent shadowed craters of the moon. Alternatively extra oxygen can be made by reducing lunar soil to metals, allowing us to make NO2 and then react with lunar soil to make solid nitrates that we can dump.
  14. There is lots of talk of returning to the the moon and mining its polar areas of water. Water can make propellant to bring cargo and crews back from the moon and propel a space economy, but specifics are not so good. You see Water needs to be converted to Liquid hydrogen and liquid oxygen, a rather energy intensive process. Lets say you have 1 MW thermal of power to work with, that could produce 100 tons of propellant at 10% efficency (electrolysis loses, coversion to electricity loses, power mining equipment, cryo coolers) in 155 days, or 235 tons a year. Half of that fuel is lost to get it to lunar orbit, only about 25% if we consider reusuable fuel shuttles from the surface and back, so that coming to ~56 tons of propellant in as far as Earth-Moon L2 per year. To provide that much power it is often assumed that requires nuclear reactors, its easily possible to do 1 kg/kw thermal, but the added electrical conversion equipment and radiators is going to bring that up to 20-40 kg/kw, so that comes to 40 ton power plant, landed on the moon. But wait that is not including the electolysis and cryoplant for making and liquifying the fuel. Solar panels can do at most 2 kg/kw, but at least that is as electricity, but that is not including stuctural mass which is going to be more on the moon then in zero gravity. Lets say 10 kg/kw and an efficency of 20% instead of 10% (so 500 kWe is needed instead of 1000 kWh) and that comes to 5 tons, not bad. At the poles of the moon there are places of "eternal sunlight" where direct sun light is available 80-90% of the time, so it may be possible with present day solar photovoltaics to buid multple megawatts worth of solar power farms at the moons poles. Lets say 30% efficent solar panels are used, hung from a mast a 35 m by 7 m array could produce 100 kw, this mind you is 2-3 times more efficient then the ones on the ISS. Add the mass for electrolysis and cyrocoolers and radiators, lots of radiators, we are likely talking about at least 100 tons of eqipment for at most 1 tons of fuel a day.
  15. If the base is at the south pole (or north pole) then orbital rendezvous make sense again, regardless of direct ascent or orbital rendezvous return to earth windows from low polar orbit open once every 14 days, or they can fly up to L2 and swing back to earth from there at any time with small added cost in fuel and up to doubling of flight time (up to 7 days instead of 3-4)