Subject: Space-tech Digest #91 Contents: Nick Szabo Re: Plastics in space Paul Dietz Re: Plastics in space Phil Fraering Re: Plastics in space John Roberts Re: Plastics in space Paul Dietz Re: Plastics in space Nick Szabo Native fuels from ammonia Henry Spencer Re: Native fuels from ammonia Paul Dietz Re: Native fuels from ammonia Jonathan Leech Re: Native fuels from ammonia Paul Dietz Keeping cool at 1 AU (was: Re: Native...) John Roberts Temperature "in the shade" at 1AU Paul Dietz Re: Keeping cool at 1 AU (was: Re: Native...) ------------------------------------------------------------ From: sequent!techbook.com!szabo@uunet.UU.NET (Nick Szabo) Subject: Re: Plastics in space To: dietz@cs.rochester.edu Date: Wed, 11 Dec 91 0:33:44 PST Cc: space-tech@cs.cmu.edu Paul Dietz writes: > [making formaldehyde, phenol, and urea from native ices] > [formaldehyde by partially oxidizing methanol] > Getting phenol or urea could be challenging Is there any way to make benzene and propylene from CH4,H2O,CO2 and/or CO? These can be oxidized to form cumene hydroperoxide, which is then concentrated and cleaved to phenol and acetone by acid catalysis. Assuming the ice contains NH3 & CO2 (most comet ices do), urea can be made in several different ways: (1) from ammonia and cyanic acid. (2) by electrolysis of cyanimide CNNH2 + H2O -> CO(NH2)2 (3) by heating ammonium carbonate at 33-53 atm. (4) from ammononia, carbon monoxide, and sulfur dissolved in methanol. (operates at 100C and 20 atm, -> urea+H2S) (5) [most common method] ammonia and carbon dioxide under pressure, to form ammonium carbamate, which is then decomposed into urea and water: 2NH3 + CO2 <=> NH2COONH4 (exothermic) NH2COONH4 + heat <=> CO(NH2)2 + H2O (endothermic) For a total recycle plant typical consumption per metric ton of pure urea product in process (5) is as follows: kgs CO2 755 kgs NH3 570 kwh power 135 m^3 cooling water 65 (assumes delta-T = 11C, recycled) kgs export steam 350 The inputs for (4) and (5) can be distilled in situ from most native ices except for sulfur, which (along with the the inputs for (1)-(3)) can be prepared from these ices with some chemical processing. I have little data on plant mass and design. Going to microgravity and vacuum will probably involve extensive redesign of material flow and minimization of net exothermic reactions to minimize cooling needs. Most of the power requirement is actually heat, which can come from solar mirrors. If we can substitute a large, cold heat sink and solar-thermal driven heat pump for electric refrigeration, the rest of the electric power requirement goes away. ------------------------------ Date: Wed, 11 Dec 91 10:28:16 EST From: dietz@cs.rochester.edu To: sequent!techbook.com!szabo@uunet.UU.NET Subject: Re: Plastics in space Cc: space-tech@cs.cmu.edu More on plastics in space... Polyethylene might be a useful material. One way to make it is as follows: (1) Heat carbonaceous material to high temperature to drive off volatiles. The result should be mostly carbon -- coke. [ Note: the first commercial source of phenol was from coal tar. It would be interesting to examine the pyrolysis products of carbonaceous asteroidal material to see if one could obtain useful feed stocks. ] (2) Mix the carbon with calcium oxide. (3) Heat, driving off CO2, yielding calcium carbide. (4) React with water to form acetylene gas. Hydrogenate the acetylene to make ethylene. (5) Heat the resulting calcium hydroxide to regenerate calcium oxide. [ Can acetylene be condensed to form benzene? ] [ I imagine other oxides would also work. ] Once ethylene is available, simple polyethylenes can be made (although some advanced forms require different monomers). Note that steps (1), (3) and (5) can be performed in a vacuum, if one does not want to recover the volatiles. If benzene is available, ethylene and benzene can be reacted to make ethylbenzene, which can be dehydrogenated to make styrene. --- It would be nice to have really simple systems for making polymers, though. Complicated chemical systems with lots of catalysts, separators, etc. seem breakdown-prone to me, although perhaps if they are located in earth orbit they could be maintained largely by teleoperation. One alternate approach would be to grow organisms that could make useful chemicals (in effect, getting self-reproducing, self-regenerating chemical factories). Two questions arise: what conditions are required for growth, and what chemicals can be made this way? Photosynthetic organisms are a possibility, but this would require large, transparent pressure vessels. Perhaps more practical are chemotrophic organisms that can grow on mixtures of simple compounds in a compact bioreactor. For example, there are bacteria that can grow on methanol and oxygen, in a medium containing ammonium, phosphate, sulfate and some other simple ions. Other bacteria exist that metabolize hydrogen gas itself (with CO2). The energy sources here would be produced artificially. Even better, perhaps (anaerobic?) bacteria can be found that can grow directly on carbonaceous asteroidal material. Compounds that organisms could conceivably produce include (but are not limited to): polyester plastics (polyhydroxybutyrate and polyhydroxyvalerate, for example), ethyl alcohol, acetone, carboxylic acids, ethylene and perhaps cellulose or lignin. Genetic engineering could be used to optimize output of particular compounds; perhaps one could even include artificial enzymes catalyzing particular desired reactions. The biological approach has the advantage of being simple and potentially flexible, but it would likely be less efficient. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 11 Dec 1991 09:51:34 -0600 From: Fraering Philip G To: dietz@cs.rochester.edu, szabo@techbook.com Subject: Re: Plastics in space Cc: space-tech@cs.cmu.edu Actually, since you're using native materials, it sounds like a good assumption to make that you have access to lunar and/or asteroidal s-type materials or metals for making some sort of radiator equipment from for a conventional heat pump. What's more, you could actually consider using CFC's as the working fluid again. Let's have the lack of an ozone layer in space be an asset and not a liability :-). By a solar-thermal driven heat pump, do you mean something along the lines of the old natural-gas powered refrigerators? What sort of temperatures were you thinking of? Phil ------------------------------ Date: Wed, 11 Dec 91 16:33:31 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: Plastics in space >...Compounds that organisms could conceivably produce include (but are >not limited to): polyester plastics (polyhydroxybutyrate and >polyhydroxyvalerate, for example), ethyl alcohol, acetone, carboxylic >acids, ethylene and perhaps cellulose or lignin. Genetic engineering >could be used to optimize output of particular compounds; perhaps one >could even include artificial enzymes catalyzing particular desired >reactions. Please bear in mind that there is a certain amount of risk associated with genetic engineering, and that risk is perhaps greatest when dealing with microorganisms. I'd hate to see something get loose on Earth that thrives outside the reaction vessel and gradually converts Earth's organic matter into non-biodegradable plastic. There *are* safety precautions that can be taken (i.e. use large, slow- reproducing organisms, or organisms that need some nutritional supplement not found in nature), but I'm not sure current safety precautions are good enough to allow us to tailor microorganisms to produce just any arbitrary product. In addition, it will be necessary to verify that the precautions chosen are effective in the environment of space. If adequate safety measures can be established, and if these measures are taken very seriously and followed completely, then I'd say genetic engineering offers considerable promise for processing of materials in space. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Wed, 11 Dec 91 17:51:33 EST From: dietz@cs.rochester.edu To: roberts@cmr.ncsl.nist.gov Subject: Re: Plastics in space Cc: space-tech@cs.cmu.edu John Roberts wrote: Please bear in mind that there is a certain amount of risk associated with genetic engineering, and that risk is perhaps greatest when dealing with microorganisms. I'd hate to see something get loose on Earth that thrives outside the reaction vessel and gradually converts Earth's organic matter into non-biodegradable plastic. But all of the materials I've mentioned are biodegradable. The particular polyesters I listed are natural polymers used by some bacteria for food storage (they serve a function analogous to starches in higher plants, but have better physical properties for use as plastics). They are present naturally all over the world. These particular polymers have excited considerable interest recently; the synthetic pathway for PHB is coded by just 3 genes, all of which have been cloned. The hope is to splice them into green plants, so the plastic can be produced on a large scale for a price comparable to starch (~ 10 cents/pound). Moreover, any organism that produces a nonbiodegradable polymer is going to be at a disadvantage in the wild, in general, since it is wasting energy and materials on something that does not further its own reproduction (the exception would be if it were a macroscopic organism which the polymer made inedible to predators; trees already do this with lignocellulose, for example, which many organisms have a hard time handling). A problem with a biotech approach would be that occasional back mutations would slow or eliminate the desired reaction; this more fit strain would take over the bioreactor, ruining the batch. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: sequent!techbook.com!szabo@uunet.UU.NET (Nick Szabo) Subject: Native fuels from ammonia To: space-tech@cs.cmu.edu Date: Wed, 11 Dec 91 1:20:11 PST An accessible source of ammonia-containing ice in space lets us set up a native-fuel scheme with the commonly used liquid fuels hydrazine monopropellant (N2H4, Isp 220) and monomethyl hydrazine/nitrogen tetroxide bipropellant (MMH/N2O4, Isp 310). These may be preferable to H2/O2 (Isp 460) due to difficulty of handling and cryogenic mass loss during storage and long duration missions of LOX and LH. A bonus is that space-refueling technology already exists for hydrazine, implemented on the Compton Observatory (GRO). A second bonus is that hydrazine makes great fuel cells because of its reactivity: Anode: NH2NH2 + 4OH- -> N2 + 4H20 + 4e E = 1.16V Cathode: O2 + 2H2O + 4e -> 4OH- E = .4 V Overall: O2 + H2O + 4e -> 4OH- E = 1.56V Direct synthesis of hydrazine and hydrogen can be obtained via passage of ammonia through an extended glow discharge, with hydrogen byproduct: 2NH3 <=> N2H4 + H2 Highly turbulent flow and effective cooling are required. This is not commercially used on Earth, but is the simplest path to hydrazine. Earth industries use the Olin process: NaOH + Cl2 + NH3 -> N2H4 and the urea process: urea + NaOCl + NaOH -> N2H4 These reactions require only low temperatures but are more complicated, requiring several steps, use of inhibitors like glue or albumin, and vacuum distillation. Sodium and chlorine can be recycled. See previous post for methods of making urea from NH3. MMH is derived from hydrazine. NO2 can be obtained by heating and passsing NH3 and O2 through a catalyst mesh, or it may be frozen in native form in the ice. When cooled NO2 dimerizes to N2O4. ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 11 Dec 91 11:24:42 EST Subject: Re: Native fuels from ammonia To: space-tech@cs.cmu.edu >These may be preferable to H2/O2 (Isp 460) due to difficulty of handling >and cryogenic mass loss during storage and long duration missions of >LOX and LH... Bear in mind that the equilibrium temperature of a well-shaded object in space circa 1 AU is roughly LOX temperature. It's only hydrogen that really has problems with in-space storage. NH3+LOX or CH4+LOX may be better choices than MMH+N2O4. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Wed, 11 Dec 91 20:38:37 EST From: dietz@cs.rochester.edu To: henry@zoo.toronto.edu Subject: Re: Native fuels from ammonia Cc: space-tech@cs.cmu.edu > Bear in mind that the equilibrium temperature of a well-shaded object > in space circa 1 AU is roughly LOX temperature. Actually, a really well-shaded object could be much cooler than this, couldn't it? The object would be heated a bit by radiation from the shield itself, but there is no reason why the emissivity of the back side of the shield need not be very low; one could also use multiple shields of progressively lower temperature (arranged as slices through a cone so that each can "see" only the next hotter and next cooler shield, and only one is in sunlight). Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 11 Dec 91 21:11:23 -0500 From: Jonathan Leech To: space-tech@cs.cmu.edu Subject: Re: Native fuels from ammonia Paul Dietz: >but there is no reason why the emissivity of the back >side of the shield need not be very low; one could also use multiple >shields of progressively lower temperature Or a skinny tank, oriented with one of the narrow ends face on to the sun. This gives you (almost) arbitrary emitting surface relative to the amount of sunlight absorbed. I don't know how difficult maintaining this in Earth orbit would be, but it should be easy in deep space - solar gravity gradient might eliminate need for active control. Jon (leech@cs.unc.edu) __@/ ------------------------------ Date: Wed, 11 Dec 91 22:14:33 EST From: dietz@cs.rochester.edu To: leech@cs.unc.edu Subject: Keeping cool at 1 AU (was: Re: Native...) Cc: space-tech@cs.cmu.edu > Or a skinny tank, oriented with one of the narrow ends face on to > the sun. This gives you (almost) arbitrary emitting surface relative > to the amount of sunlight absorbed. In fact, it doesn't give an arbitrary emitting surface, because of the nonzero angular size of the sun. Suppose we want to maximize the emitting surface behind a flat circular plate. This can be done by extending a cone back from the plate. At 1 AU, the emitting surface of the sharpest cone shadowed by the plate is some 214 times the area of the plate (this being the ratio of 1 AU to the diameter of the sun). If the entire cone, including base, is perfectly black, and the cone is isothermal, its surface temperature is about 103 K. If the base of the cone is highly reflective then the equilibrium temperature is lower. One can obtain lower temperatures by relaxing the condition that the system be isothermal. This way, more of the heat is radiated at higher temperature, where radiation is more effective. Paul ------------------------------ Date: Wed, 11 Dec 91 23:05:33 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: Temperature "in the shade" at 1AU An object in Earth orbit has the additional problem of heat radiating from the Earth. COBE needed both a sun-synchronous orbit and an onboard cryogenic source. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Wed, 11 Dec 91 23:03:05 EST From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: Keeping cool at 1 AU (was: Re: Native...) I mistated the ratio of 1 AU to the diameter of the sun: the ratio is about 107, not 214. So the eq. temperature is not 103 K, but rather 2^(1/4) times this, or about 123 K. One simple case is a planar shield much larger than the payload, placed so that it covers the sun. If the shield is a perfect blackbody, it will reach a temperature of about 331 K. This will subject the shielded object to a radiant flux of about .07 W/m^2. Since the shielded body is irradiated on one side only, it could achieve a temperature of about 24 K. Making the shield more reflective would reduce this still further. Paul ------------------------------ End of Space-tech Digest #91 *******************