Subject: Space-tech Digest #135 Contents: Lunar colonies, lunar construction materials (18 msgs) ------------------------------------------------------------ From: szabo@techbook.com (Nick Szabo) Subject: Lunar "colony" reality check, part 2 To: space-tech@cs.cmu.edu Date: Sun, 15 Nov 1992 03:53:47 -0800 (PST) Lunar "colony" reality check, part 2: * The claim that solar energy will be so cheap on the moon as to be an advantage, is absurd. A lunar site spends a half-month long stretch every month out of sunlight. Solar cells are not economical for most uses on earth and would cost far more to transport on the moon. Making them on the moon is even more absurd, see following comments on industrial capabilities. * Lower launch costs benefit all large space operations, from DBS to comet mining. Lunar bases do require a much larger and more improbable fall in launch costs than dozens of other space development activities which would actually make money. * In addition to hydrocarbons or polymers, urea is a good bulk way to supply lunar operations with essential volatiles from earth. However, these schemes require huge ongoing launches from earth. They require large-scale, messy, difficult to maintain chemical plants designed for 1/6 g, as does the cracking of oxygen from lunar regolith. * The industrial environment on the moon is vastly inferior to that on earth, and to that in space where there is microgravity, high-grade metal regolith and abundant volatiles. The energy and thermal environment of the moon, as well as the lack of cheap volatiles, makes it an extremely poor place for chemical and industrial operations. * Just as with Shuttle, astronauts will not be able to fix most broken equipment. Most disabling breaks, no matter to how small a part, will require an entire replacement unit to be shipped from earth. Since the astronaut's very lives will depend on recycling equipment, large numbers of spares will have to be shipped on the first trip. * Redesigning equipment for 1/6 g will cost _more_ than redesigning it for 0 g, because the latter has been done for a much wider array of equipment on satellites & stations. * Unlike the intrepid Biosphereans, lunar astronauts will not be able to cheat and come back to civilization to find good medical care. In a lunabago will be found little more than a part-time doctor and a first-aid kit. * There are no "resources" on the moon that could not be provided at lower cost from asteroids or comets, and the most important materials like volatiles and high-grade metal regolith are available only from the planetesimals. * Transport costs to the moon are six orders of magnitude greater than transport costs to the North Slope. Not only Ed's toilet paper but also the recycling equipment, spares, and volatiles (if brought from earth) will make the cost of supporting astronauts at least six orders of magnitude more expensive than the cost of hosting a worker at the North Slope. It should be noted that no families have permanently relocated to the North Slope; even the industrial workers themselves commute by airplane rather than live without their families for years on end. * Submarines get to surface every month or more, and can come back to port for food & sex. Nobody has a "submarine colony", even though it would be far less expensive and more functional than a lunar "colony". * If scientific knowledge is an "economic resource", then what happened to NASA's planetary science budget? Why can't they even find money for a lunar polar orbiter, which costs many orders of magnitude less than even a minimal lunar base? Why not let scientists decide where to spend the science budget? (Hint: lunar base isn't even _on_ their long list of priorities). * Microgravity manufacturing, large platforms and other space industries could export $10's of billions per year to earth by using a large supply of cheap volatiles and high-grade metal regolith, available in abundance from planetesimals but absent on the moon. With low thrust in microgravity, the power needed to move this material to earth orbit is orders of magnitude less than needed to get useless lunar material out of the moon's gravity well. Our obsession with the Death Valley in front of us continues to blind our eyes to the fertile valleys beyond, and the space colonization movement remains mired in failure. Nick Szabo szabo@techboook.com ------------------------------ Date: Sun, 15 Nov 92 13:13:03 -0500 From: Jon Leech To: space-tech@cs.cmu.edu Subject: Re: Lunar "colony" reality check, part 2 >* If scientific knowledge is an "economic resource", then what > happened to NASA's planetary science budget? Why can't they > even find money for a lunar polar orbiter, which costs many > orders of magnitude less than even a minimal lunar base? Perhaps because they're spending $1.7 billion on a Saturn orbiter (just for example). NASA's planetary science budget could stand to be increased, but then the planetary scientists haven't made all that good use of the budget they already have. Jon __@/ ------------------------------ Date: Mon, 16 Nov 1992 10:28:07 -0600 (CST) From: SMITH@EPVAX.MSFC.NASA.GOV (The Ice-9-man Cometh) Subject: Re: lunar vs. asteroidal industry >From: Nick Szabo > * The claim that solar energy will be so cheap on the moon as > to be an advantage, is absurd. A lunar site spends a > half-month long stretch every month out of sunlight. > Solar cells are not economical for most uses on earth > and would cost far more to transport on the moon. Solar cells aren't the most efficient way to use solar energy, especially if they've got to be transported; their power output to weight ratio is low. A better method would be using mirrors to heat a fluid or slurry and then operating a heat engine of one sort or another. An advantage would be that the heated fluid could be stored (say, in a discarded cryogen tank, if the temperature isn't TOO high) through the dark period. This sort of method requires a lot of active control, which is probably why nobody uses it in orbital systems; too much vibration and stationkeeping hassle. Shipping a Stirling engine/generator combination, some VJ plumbing, a few servos, and a lot of aluminized Mylar shouldn't be a problem; structural materials can be lunar (rock pylons, rockfoam etc). Does anyone remember reading about a new sealed-cylinder, linear-alternator Stirling cycle engine/generator a few months ago, and what the reference was? (My memory is like a wicking screen and its retention is failing. :) >* The industrial environment on the moon is vastly inferior to that > on earth, and to that in space where there is microgravity, > high-grade metal regolith and abundant volatiles. The energy > and thermal environment of the moon, as well as the lack of cheap > volatiles, makes it an extremely poor place for chemical > and industrial operations. Most of the cost in space can be expressed in terms of delta-V. Including the cost of processing equipment f.o.b. Moon/asteroids, and return of materials to where we want them, how do they compare? How about the time factor (i.e. how long do you want to wait for your products to show up in a cheap orbit)? By the way, microgravity is not an advantage in most industrial processes as we know them today. Simple things such as slag separation in smelting are not simple when mixtures do not automatically sort themselves out by density. Microgravity allows us to do many new things, but by the same token, it requires us to find new ways to do old things. Not all of these will be cheaper or easier. >* Redesigning equipment for 1/6 g will cost _more_ than > redesigning it for 0 g, because the latter has been > done for a much wider array of equipment on satellites > & stations. See above. Any gravity is a lot more familiar to industrial designers than no gravity. I would guess that the biggest problem with moving-parts machinery on the Moon would come from fine rock dust working its way into things and abrading polished surfaces, which is one thing that space factories wouldn't have to contend with. >* Transport costs to the moon are six orders of magnitude > greater than transport costs to the North Slope. Not only > Ed's toilet paper but also the recycling equipment, spares, > and volatiles (if brought from earth) will make the cost of > supporting astronauts at least six orders of magnitude more > expensive than the cost of hosting a worker at the North Slope. I don't understand how this problem is solved by turning to planetesimals. Is the suggestion that everything should be autonomous, not requiring onsite people? If so, we're going to have to wait a while, and spares will become much more important; robots will need modular parts and a "just replace it if it gives trouble" philosophy, where a technician might repair a part or work around it. > ... Nobody has a "submarine colony", even though > it would be far less expensive and more functional than a lunar > "colony". Well, we don't put them underwater because it's cheaper to put them on the surface, but what about offshore drilling platforms? Living on one of those is about as cheerful as living in a Moon colony, and some of them operate on six-month shifts. I wonder if anyone has done a psych analysis of these guys? It might prove valuable. >* Why not let scientists decide where to spend the science budget? Congressional question (and a good one). Is this the place for it? On that subject: I agree with the person who thought that making proposals was more productive than trashing everyone else's. Specifically to the subject of this post, I'd like to see a detailed analysis of the asteroid- mining problem, with costing and a timeline, similar to the booster proposals we've seen recently. This would impress me more than generalized "this is the wave of the future" articles. I can't evaluate the worth of a proposal until I've seen the above analysis, whether it's a backyard grill or a Lofstrom loop. | James W. Smith, NASA MSFC EP-53 | SMITH@epvax.msfc.nasa.gov | | "This is your pilot. We are about to attempt a crash landing." | | And I said "Uh oh...this is going to be some day...." | | --Laurie Anderson, _From the Air_ | | Neither NASA nor (!James) is responsible for what I say. Mea culpa. | ------------------------------ To: Nick Szabo Cc: space-tech@CS.CMU.EDU Subject: Re: Lunar "colony" reality check, part 2 Date: Mon, 16 Nov 1992 11:45:27 EST From: John F Carr > * The claim that solar energy will be so cheap on the moon as > to be an advantage, is absurd. A lunar site spends a > half-month long stretch every month out of sunlight. > Solar cells are not economical for most uses on earth > and would cost far more to transport on the moon. Whenever I hear proposals for large scale solar power generation, on earth or in space, I assume solar thermal power, not photoelectric cells. I wonder how effective lunar rock would be as a heat sink? I expect it is a poor conductor of heat. Even so, a lunar power generator should be more efficient during the day than an orbital power station. ------------------------------ From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) Subject: Re: lunar vs. asteroidal industry To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Date: Mon, 16 Nov 92 12:53:20 CST James W. Smith (SMITH@epvax.msfc.nasa.gov) writes: > Solar cells aren't the most efficient way to use solar energy, especially > if they've got to be transported; their power output to weight ratio is > low. A better method would be using mirrors to heat a fluid or slurry and > then operating a heat engine of one sort or another. An advantage would > be that the heated fluid could be stored (say, in a discarded cryogen tank, > if the temperature isn't TOO high) through the dark period. This sort of > method requires a lot of active control, which is probably why nobody uses > it in orbital systems; too much vibration and stationkeeping hassle. Storing excess generating capacity: How about electrolyzing water, pressurizing and storing the H2 and O2, and then feeding it back through a fuel cell during the night. Getting rid of the waste heat during pressurization (and making it up during the night) presents something of a problem, but the equipment is fairly low maintenance; fuel cells don't wear out and, in a gravity field, there's no need for a purge, while compressors are fairly easy to keep running. As long has you have to have a water asset around anyway, might as well make it useful. Unless my memory has completely collapsed, the solar constant on the lunar surface is about 10 times what it is here. Can anyone verify this? Lou Adornato uunet!ssi!lfa | The secretary (and the rest of the company) Supercomputer Systems, Inc | have disavowed any knowledge of my actions. Eau Claire, WI | ** Space IS our future! ** ------------------------------ To: "Louis F. Adornato" Cc: space-tech@cs.cmu.edu Subject: Re: lunar vs. asteroidal industry Date: Mon, 16 Nov 1992 15:38:47 EST From: John F Carr > Unless my memory has completely collapsed, the solar constant on the lunar > surface is about 10 times what it is here. Can anyone verify this? It may be 10% greater, but not 10 times greater. That would mean the atmosphere aborbs 90% of solar energy. ------------------------------ Date: 16 Nov 1992 16:56:10 -0500 (EST) From: "GORDON D. PUSCH" Subject: Re: lunar vs. asteroidal industry Louis F. Adornato writes: > ... the solar constant on the lunar surface is about 10 times what it is > here. Can anyone verify this? > Last I heard, the solar constant was 1370 W/m^2 "in vacuo" at 1 AU from Sol; on a clear day in the desert, it's about 700--1000 W/m^2. Most other places, it's a lot less *on the average*, because of clouds, haze, dust &c., &c... Maybe that's where your factor of ten is coming from... Gordon D. Pusch ------------------------------ Date: Mon, 16 Nov 92 13:24:58 -0800 From: gwh@lurnix.COM Subject: Re: lunar vs. asteroidal industry >Unless my memory has completely collapsed, the solar constant on the lunar >surface is about 10 times what it is here. Can anyone verify this? 1.38-1.4 kW/m^2 Same as in free space. On the earth's surface, it tends to be closer to 1.2 to 1.3 kW/m^2 on median good days. Weather drops that a whole lot. -george ------------------------------ Date: Mon, 16 Nov 92 16:14:34 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: lunar vs. asteroidal industry Lou Adornato wrote: > How about electrolyzing water, pressurizing and storing the H2 and O2, > and then feeding it back through a fuel cell during the night. > Getting rid of the waste heat during pressurization (and making it up > during the night) presents something of a problem, Actually, an electrolytic cell can operate at elevated pressure; this just raises the voltage a bit. So no separate compressors are necessary. You do need to dissipate the heat from losses in the system, which come to about 50% in an electrolysis/fuel cell system. BTW, the talk about solar-thermal on the moon seems pretty senseless. As long as you are operating a thermal powerplant on the moon, you might as well use a nuclear heat source. See the latest Intersociety Energy Conversion Engineering Conference for some designs. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ To: John F Carr Cc: Nick Szabo , space-tech@cs.cmu.edu, gwh@lurnix.COM Subject: Re: Lunar "colony" reality check, part 2 Date: Mon, 16 Nov 92 12:03:55 -0800 From: gwh@lurnix.COM The primary problem with any lunar solar power source is that you get two weeks of dark. Any thermal or other storage system for two weeks of ops is likely to be unmanageable and too heavy to fly there. You save a lot if you just run life support during the night phase, but it's still a pain. Once a certain level of lunar colonization is in place, you can get around it by just running a belt of power plants around the equator and running power cables to match, so that you've got continuous exposure. However, the level of industry needed to lay down thousands of miles of cable on the moon is quite a hurdle. Everyone I've seen talking seriously about the Moon presumed that you get electricity from a nuclear plant and got heat for industrial processes from the sun during daylight (and didn't run them at night). That's the current NASA plan, and until you've got a whole lot of equipment there, looks to be the most effecient and painless. -george william herbert gwh@lurnix.com gwh@retro.com coming soon ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 17 Nov 92 14:46:55 EST To: space-tech@cs.cmu.edu Subject: Re: lunar vs. asteroidal industry >> How about electrolyzing water, pressurizing and storing the H2 and O2, >> and then feeding it back through a fuel cell during the night. > >BTW, the talk about solar-thermal on the moon seems pretty senseless. >As long as you are operating a thermal powerplant on the moon, you >might as well use a nuclear heat source... Nuclear power might be the right technical solution but it has obvious political problems at present. People have done serious work on energy storage as a result; Geoff Landis's talk on this is very interesting. There are actually a lot of possible methods, many of which don't work well except on a very large scale. Regenerative fuel cells, as in Lou's suggestion, currently get the nod as the best small-scale system. An alternative, which has received serious attention, is beaming power from Earth! Laser illumination of a solar array looks quite feasible; it's even better than you think, because solar-cell conversion efficiency at a single well-chosen laser wavelength is much better than for sunlight. This probably isn't suitable for Luna City, but it might be just the thing for small early bases. People are also investigating the idea for other applications, such as laser-electric OTVs and battery elimination for Clarke-orbit comsats. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 18 Nov 92 13:00:22 EST Subject: Re: lunar vs. asteroidal industry To: space-tech@cs.cmu.edu > Some of the batteries used on unmanned spacecraft appear to have operating > temperature ranges much greater than that of fresh water - which might be > helpful given the day-night cycle on the moon. Hmm, I'm not sure what this would be referring to. Batteries are one of the two components (the other being fuel tanks and plumbing) that are least tolerant of temperature extremes. They are also inordinately heavy and have quite limited lives. Most batteries *contain* water in some form (although it's often in the form of a pretty thick chemical paste), as the medium for the electrolyte. A battery is basically just a fuel cell that also serves as the storage vessel for both the fuels and the reaction products. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Wed, 18 Nov 92 22:32:29 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@cs.cmu.edu Subject: Re: lunar vs. asteroidal mining >You don't run water through the fuel cells, you take water out. A >damaged fuel cell _might_ contaminate the water it produces (with >potassium), but since every manned American spaceflight since the >Gemini program produced drinking water through the fuel cells, I don't >think this is highly likely. I guess electrolyzing (or otherwise separating) the water to get hydrogen and oxygen would tend to remove the impurities. >> Some of the batteries used on unmanned spacecraft appear to have operating >> temperature ranges much greater than that of fresh water - which might be >> helpful given the day-night cycle on the moon. >I don't understand how this applies; I'm assuming that the fuel cells >and the tank farm will be inside habitable volume (to make maintenance >easier), so the operating temperature won't be a problem. Under ordinary operating conditions, I agree. But I've had a sufficient number of things I designed fall apart when conditions went out of the range I expected that I prefer to design conservatively when I can't be sure that the expected conditions will be maintained. We can presume that an inhabited lunar station will maintain an acceptable temperature range under normal conditions - but what if something unexpected happens? Are there scenarios in which the temperature control would fail (i.e. for a few days), but we would like the power system to resume operation later? (Perhaps the power system fails, but the inhabitants have sufficient stored oxygen to get by until they can fix it.) If the fuel cell contains water, and the water freezes, it could rupture the plumbing. I wouldn't say that potential problems will necessarily make the approach impractical - but precautionary measures should be taken. For instance, antifreeze could be kept on hand to pour into the fuel cell system in case of heater failure. Backup power systems should be available. If the station is to be abandoned for an extended period of time, perhaps the fuel cell plumbing could be heated and exposed to vacuum to drive out all the water. Here's a paragraph from "Lunar Science: a Post-Apollo View" from which one should be able to derive the equilibrium temperature of an unheated lunar base and the thermal conductivity of the lunar regolith: Measurements of conductivity indicate that the top layer is strongly insulating. There is an increase of about 47K in the top 83 cm. The top surface (2-3 cm) is a loosely packed porous layer. Surface temperatures are extreme. At the Apollo 17 site, the surface reaches a maximum of 384K (111C) and cools to 102K (-171C) at the end of the lunar night. The near-surface temperature is 216K (-57C). These temperatures are about 10K higher than those observed at the Apollo 15 site. The agreement with previous estimates based on terrestrial observations was very close. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Mon, 16 Nov 1992 17:20:17 MST From: "Richard Schroeppel" To: space-tech@cs.cmu.edu Subject: lunar construction materials I sent this to space digest, but maybe space-tech is more appropriate. [An aside: I don't like Szabo's tone, temperment, and monomania, but he brings up some relevant objections (mixed in with some irrelevant ones). I've reached the point where I skip over his jeremiads, though.] ================================= In a slightly different context, John Roberts & Henry Spencer write ... JR> >... Here's the composition for the Apollo 11 site: SiO2 (42.04%), >TiO2 (7.48%), Al2O3 (13.92%), FeO (15.74%), MgO (7.90%), CaO (12.01%), >Na2O (0.44%), K2O (0.14%), P2O5 (0.12%), MnO (0.21%), Cr2O3 (0.30%). >(There are also tables for overall highland and maria composition.) Does >anything in there sound like it would be flammable... HS> Note, straight oxides. One or two of them could add a bit more oxygen, but overall this is *not* a flammable mixture. Some of them would react a bit with atmospheric water vapor to form hydroxides. This raises a potential problem with some desirable uses of Lunar regolith for construction materials. We'd like to just fuse a bit of the regolith and use it as construction stone. But several of these minerals *want* to pick up water. In their present setting, they are "dry as dust". But in the interior of any human-occupied environment, they will pick up water from the air. This will lead to a change in volume, and the material will corrode, probably flaking. (It will also act to keep the humidity down, which might be either good or bad.) Even outside a human habitation, there will be stray water vapor, from the airlock, from the surface of anything that was inside, waste dumps, maybe occasional spills, etc. Given "water to burn", mixing regolith dust with water might make a good cement, although we'd have to worry about it drying out. A possible way to look for hidden water (subsurface ice?) would be to look for spectral signatures of hydrated minerals. Rich Schroeppel rcs@cs.arizona.edu ------------------------------ To: Richard Schroeppel Cc: space-tech@cs.cmu.edu, gwh@soda.berkeley.edu Subject: Re: lunar construction materials Date: Mon, 16 Nov 92 18:39:06 -0800 From: George William Herbert Turning regolith into cement is a proven process. The best method is to take regolith, put it in a pressuretight mold (low pressure) and inject steam. Tests with regolith simulant were highly successful (in a vaccum chamber) and small-scale testing with several grams of actual lunar soil gave a verifying datapoint. Regolith in fact makes better cement than earth-based materials due to vaccum welding of small grains to larger ones, forming a material very strong to bond with. The Japanese materials scientist who did the work is exceptional to listen to; he's onto something, if the cost of bringing water to the moon comes down (or we find it there), and he's very enthusiastic about every step he's taken. A great lecturer. I can get name & references later (they're at home in a sedimentary filing system heap). -george ------------------------------ Date: Tue, 17 Nov 92 21:31:15 -0800 From: George William Herbert To: space-tech@cs.cmu.edu Subject: Lunar Concrete info Ok, I dug through several piles of materials and found my references on Lunar concrete. The guy who gave the lecture and did the experiments was T.D. Lin (affiliation unknown, look for a Japanese materials scientist or in American Concrete Institute publications). I misspoke slightly in describing the process he suggested, so let's start from scratch. What he investegated was making cement from ground lunar basalt, and adding in more ground basalt as filler to make concrete. The process involves heat-evaporating some of the basalt's constituents using solar thermal processes; a cook-out at 2000 K leaves a residual content of 40% CaO, 49% Al2O3, and 11% SiO2. At 2200 K the percentages are 43:53:5. Both of these are within industry tolerances for the production of alumina cement on the earth. The production process for making concrete involves mixing the cement with whatever soil is around. Using a 40 g sample from Apollo 16, a small sample was produced to compare the properties of earth and lunar material based cements. The results were very positive; the lunar cement/concrete combination is stronger (up to 75 MPa compressive yield strength (about 10,000 PSI) versus 5,000 PSI for terrestrial concretes) and as tough and durable as earth-based concretes. There was minimal strength loss when samples were exposed to vaccum for extended periods of time, which tailed off and is presumed to level out at some value about 80% of the maximum. The curing method was to use steam at mid pressures after drymixing the concrete. Lin proposed generating water by mixing hydrogen with Ilmenite from the lunar surface at 800 C; the result is Titanium Oxide, Iron (which he thereafter referred to as "rebar" 8-) and water. The amount of hydrogen that has to be brought is about 0.3 % (three parts in 1000) of the final mass of concrete to be produced, quite a leverage. Especially if the iron coming out the side is useful 8-) Ok, is that a good enough summary? 8-) -george william herbert Retro Aerospace gwh@soda.berkeley.edu gwh@lurnix.com gwh@retro.com coming real soon now ------------------------------ To: George William Herbert Cc: space-tech@cs.cmu.edu Subject: Re: Lunar Concrete info Date: Tue, 17 Nov 92 21:34:02 -0800 From: George William Herbert Slight clarification. The vaccum strength loss is presumed to be less than 20% ... with final strength about 80% of reference value. NOT a loss of 80% of the reference value... 8-) -george ------------------------------ End of Space-tech Digest #135 *******************