RuBisCO

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.

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.

Waste of hydrogen. NO2 will store fine enough in lunar soil, just heat it up to extract it.

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?

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.

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.

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.

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

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.

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.

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.

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)

No more then standard solid propellants possibly. I'm pretty sure electrics is not going to land MSL class rovers on Mars, or flying drone on Titan or provide attitude control and trajactory correction for such in transfer orbit, MSL by the way used hydrazine.

So I came upon Rocket Labs patent for their monopropellant, the one they may or may not have flown on their Photon Satellite Bus https://patents.google.com/patent/US20120234196A1/en To sum it up: the monopropellant consist of particles of solid oxidizer, particles of a metal to raise the temperature of combustion and be the primary combusted material (thermic agent) and a mix of binding liquids and dissolved gasses that act as propellant mass and turn what would normally be a simple solid fuel into a Non-Newtonian fluid or gell. This gell is pushed either via pressurized gas against a bladder membrane or a metalic piston that can be cranked mechanically (just like a caulk gun). Thanks to its Non-Newtonian fluid properties via the careful choice of surfactants, binders, Rheology Modifiers, it can be pushed into an atomizer, sprayed into the combustion chamber and burn without combustion blow back (it only combusts when atomized and thus the combustion front can't crawl back up the line and into the fuel tank and blow everything up). The gas dissolve in it is most likely Nitrogen Oxide which can be heated by the combustion chamber and sent back to compress the fuel tank. This stuff is pretty advance! Much safer then Hydrazine (stardard monopropllant) and way denser, up to 1.72 g/ml! Compared to other advance monopropellants such as ionic solution AF-M315E which is flying right now on Green Propellant Infusion Mission which was just launched into orbit, Rocketlabs fuel has higher density (~1.72 vs 1.47) and potentially has higher Isp, maybe, not known, nowhere can I find rocketlab reporting the Isp of their fuel. Also unlike AF-M31E this stuff can't be used as combustion chamber coolant, not directly at least, the gas in its can be heated and sent back as pressurizer or bleed off to wick heat. What we see now is a move to replace hydazine, the standard monopropellant, will it be RocketLab's VLM, will it be NASA AF-M31E, or the ESA's LMP-103S? LMP-103S has less Isp and density than AF-M31E, but VLM has even higher density and maybe even higher ISP. Rocket labs test rocket is claimed by the patent to use 30% carrier-fluid that would put the Isp somewhere between 250-260 if we count the carrier-fluid as binder in a standard solid rocket fuel, but the patant allows for a range of binder (carrier-fluid) types and precentages that could, possible, bring the ISP even higher: 10-15% binder/fluid would bring the Isp to over 300 if ammonium dinitramide is the oxidizer. In short Rocket Lab might have the monopropellant of the future.

Intresting, but AF-M315E seems to have better performance than LMP-103S at 12% higher ISP instead of 6%, and 45% greater density instead of 24% (over hydrazine).

Yeah I would like an option to make the ugly parachute pack invisible as well. Or at the very least make it blend in better with the EVA pack instead of looking like a leather WW2 era parachute pack glueed on to a space suit, so jarring! Really triggers my on-the-spectrum-ism

I actually calculated those numbers, on the first post of this thread.

This could be said of Chlorine tri/pentafluoride, room temp storable, improves performance and density, but the cost of it is too much.

Is there any way to have mechjeb maintain a roll attitude while thrusting at a maneuver node? For example here it keeps turning ever so slowly and thus the solar panels lose power and it loses thrust.

Look the reason I started this thread was to try to find other reasons then the obvious "Fluorine is demonic" (which frankly anything that burns on contact with concrete is). I think I hit on a fact that any propellant with a idealize price above $1 never flies, regardless if how hard it is to handle. Red fuming nitric acid and Hydrazine derivatives are corrosive and toxic too, but way cheaper.

There was alot of development in fluorine and fluorine/oxygen mixtures (FLOX) as oxidizer for rockets in the 1950/1960's, and a Atlas rocket supposedly once flew on a FLOX mixture, but it never was used again... why? A FLOX (69% LF2) with Kerosene supposedly has 12% more ISP, 17% greater density and 31% great ISP/density. Well aside for being more corrosive than LOX, deadly toxic, producing launch pad damaging hot HF gas and corrosive HF pollution, I think the biggest problem was price. Liquid fluorine is $6 per kg, compared with Liquid oxygen which is $0.04 per kg, Rocket grade Kerosene is $0.05 per kg and Liquid Hydrogen is $2.6 per kg. Using those numbers for LOX/Kerosene I get $0.043 per kg of propellant, but for FLOX(69%)/Kerosene I get $3.27 per kg! That is a 76 fold more money! Using those numbers it would cost $21,419 to fuel up a 500 ton rocket with LOX/Kerosene, but $1,636,970 for FLOX(69%)/Kerosene. And those are idealized prices (1950's dollars?), we know that Elon Musk claimed it costs roughly $200,000 to fuel up a Falcon 9 with roughly 500,000 kg of propellant, that means the price of LOX/Kerosene is $0.4, or ~10 fold the ideal numbers I linked. A FLOX(69%)/Kerosene version of the Falcon 9 would end up costing at least 16 million dollars to fuel! So then the propellant goes from costing 0.3% the launch cost to 26% the launch cost. LF/LH2 is not much better, costing 12 fold the cost of LOX/LH2 (0.46 $/kg vs 5.5 $/kg), all for a 5% improvement in ISP and 22% improvement in density and 25% improvement in ISP/density. The reason for this is it is very easy to make liquid oxygen, just cryopurify it from air, no need to ship it, just make it on site. Kerosene is refined from oil, Natural gas is cheap, hydrogen is reformed from either then liquified. Fluorine on the other hand has to be manufacture from electrolysis of potassium fluoride, and liquid fluorine is scary to transport. Even N2O4/UDMH is cheap in comparision at 0.42 $/kg, in fact I think there was no oribital rocket that used a propellant that cost more than 1 $/kg in those ideal prices (or 10 $/kg in realistic/today prices). So when considering rocket fuels ISP and density it not everything, clearly price is a big factor.

Yes well some satellites lack the power to run fly wheels and ion thrusters for attitude control. And yes the whole purpose of that launch is to have flight heritage to convince customers it is worthwhile.

Dragon will be outmodded anyways when BFS flies. That is why they gave up on propulsive landing with Dragon, it was not worth the effort trying to get approval, and certainly the fact of N2O4 and MMH being so nasty toxic was part of why NASA did not approve. Sure maybe Dragon on AF-M315E might work safety wise, but SpaceX has no interest in mono-propellants and by the time a Dragon on AF-M315E would be flying BFR will already be operational, using O2/CH4 for thrusters, take-off and landing. Fun Fact: there were some people crazy enough to propose mixing Liquid O2 and Liquid CH4 as a mono-propellant, turns out if you even shine a bright light on that mix it will explode. SpaceX will probably build O2/CH4 bi-propellant thrusts that are pressurized or electrically pumped and handle all attitude/maneuvering controls.

No that is outmoded, the most awesome semi-plausible engine idea ever is the continuous nuclear fission explosion/Zubrin drive/Nuclear salt-water rocket. Yes just spray uranium enriched water down a high neutron flux/neutron reflecting nozzle, ride the nuclear explosion and keep spraying water and uranium into it until you reach the velocity you want or you die, which ever comes first, either way: totally awesome!

YNM, Misinformation is Platinum: if you can say you have been doing [Y] for decades when you have really be doing [X] you have plausible deniability. So for example if you can say you been using [Y] for torpedo propellant then no one is going to question it unless they notice the torpedo has a speed and range that [Y] could not physically provide. So once again it is quite possible the military has had AF-M315E or equivalent for decades and no one noticed, perhaps not space proven, but working somewhere else. But then again there is infrastructure lock. Chlorine pentafloride never took off because it was too difficult and dangerous to handle, despite say Chlorine pentafloride/Hydrazine-Methanol would be 4% more ISP then N2O4/MMH, 25% more dense and 31% more ISP-density, that not enough improvement to warrant the danger of an oxidizer that burns through almost anything. AF-M315E on the other hand 5% more ISP then hydrazine, 45% more dense and 53% more ISP-density without any serious complications, in fact less complications then hydrazine, heck I would not be surprised if AF-M315E could not be used in propellant cooled engines unlike hydrazine.