Subject: Space-tech Digest #138 Contents: Lunar colonies, thermoelectric conversion, P2-E, low-pressure O2 (18 msgs) ------------------------------------------------------------ Date: Fri, 20 Nov 92 22:15:09 GMT From: amon@elegabalus.cs.qub.ac.uk To: space-tech@cs.cmu.edu Subject: Re: lunar construction materials You should also look at back issues of the L5 News for a paper by Larry Beyer on dry vibratables. (He was one of our founding fathers in our Pittsburgh L5 group) To make a long story short, the steel industry uses a powder technology in which materials are vibrated in a mold and form a strong material. This is used in patching things in which residual water is a complete no-no... Larry's doctorate area was ceramics and such. He calculated that the lunar soil, as it sits, is nearly ideal for dry vibratable technology. You scoop it into prefab molds, vibrate it for x hours and you have an engineering material. It is porous though, so you use a solar mirror to run a heat treatment profile on the surface to glaze and seal it. You include prestress members inside it so that cracks are self sealing, and also to handle any problems with brittleness. Dry vibratables is existing, old technology. It not only does not use water, but is in an environment in which water is an extreme danger. Anyone who group up in a steel town will know what I mean. Another related technology is a form of acoustic signature analysis that tells you if the properties of the material change. This can identify and localize cracks and other faults quickly. This is also an existing technology. I highly recommend his article. If anyone is really interested, I can get you in touch with Larry. He is not on email, to my knowledge, but I have his home phone number. ------------------------------ Date: 20 Nov 1992 17:53:28 -0500 (EST) From: "GORDON D. PUSCH" Subject: Low-pressure O2 (was: RE: Lunar "colony" reality check) To: space-tech@cs.cmu.edu >I believe the medical people do recommend normal air when practical, >because of long-term unknowns (not just low pressure, but lingering >suspicions of possible minor biological effects from nitrogen). Actually, I remember an article in _Science News_ a *loooong* time ago citing research that, even at 5psi, pure O2 *was* dangerous. For example, some workers found that rats in pure-O2 at 5psi developed emphysema-like lung-damage. Also, recall that the Apollo astronauts *always* had colds and respiratory problems (although I admit that that *could* just have been the logical result of packing three men into a sardine-can... :-T). When you get right down to it, oxygen is a *really* nasty, corrosive, substance. A faculty member at VPI&SU (sorry, don't remember the name) has spent his entire *career* cataloguing the deletious effects of O2; he concludes that most organisms on earth actually have to develop *defense* mechanisms against the stuff! Anerobic bacteria are *still* poisoned by O2 --- and so are *we* at partial-pressures of more than a couple of atmospheres. When blue-green algae stumbled across the trick of using the stuff, they probably wiped out most of the life-forms then on Earth (and without filing an environmental impact-statement first :-T). The main breakthrough of the eukaryotes was to wrap membranes about their nuclei *TO KEEP THE OXY OUT* (O2 *destroys* DNA). And most of the damage to heart-attack victims occur, not as a result of the *cutoff* of circulation to the heart, but from ``superoxide'' formation after circulation *resumes*... In summary, I believe there's now a fair amount of data arguing that pure O2 is bad for you, and *some* sort of dilutant should be included. (If nothing else, at such low pressures, it's hard to smell stuff, and one can't even *taste* a lot of things (many tastes are actually odors) --- which is not likely to be good psychologically in the long run...) Gordon D. Pusch P.S.: My contract has been extended for 2 mos (*again*), so I won't be leaving AECL until the end of 1993-Jan; however I'll be out of town until Dec-02, so I won't be able to respond to your flames until then... ;-) ------------------------------ To: "GORDON D. PUSCH" Cc: space-tech@cs.cmu.edu, gwh@lurnix.COM Subject: Re: Low-pressure O2 (was: RE: Lunar "colony" reality check) Date: Fri, 20 Nov 92 16:00:24 -0800 From: gwh@lurnix.COM As a counterpoint to that, recall that the undersea divers who work in very high pressure environments (at 20% O2, with PPO2 in the many many atmospheres level) are relatively healthy even with stays up to months at pressure (depth). -george william herbert ------------------------------ Date: Sat, 21 Nov 92 0:09:01 MET From: Magnus Redin To: John F Carr Cc: davidsen@crdos1.crd.ge.com, space-tech@cs.cmu.edu Subject: Re: Lunar "colony" reality check From: John F Carr >I thought the problem was using 1 atmosphere pure oxygen. Is pure >oxygen at 3 PSI dangerous? >Will plants grow in pure oxygen? Do they need nitrogen from the air? Plants needs CO2 from the air but no known plants need N2 exept those who have sybiotic bacteries who split N2 and make it available to the plant. (That is known by me. ) (*scream* My first posting is about farming and I want to build a small licuid fueld rocket motor for fun instead of working on a farm. But I will get time for it in a year when the campus network i built. Delurking in a year again. cu. ) -- Magnus Redin Lysator Computer Club redin@lysator.liu.se Mail: Magnus redin, Rydsv{gen 240C26, 582 51 LINK|PING, SWEDEN Phone: Sweden (0)13 260046 (Answering machine) ------------------------------ Date: 20 Nov 1992 19:19:27 -0500 (EST) From: "GORDON D. PUSCH" Subject: Re: For efficiancy of lasers we are contemplating a free electron laser... To: BEAUFAIT%CEBAFVAX.BITNET@BITNET.CC.CMU.EDU Cc: space-tech@cs.cmu.edu (who are you?) writes: >For efficiancy of lasers we are contemplating a free electron laser >to light energy out. With solar sails you still have to dock attach >and deploy a much mor difficult proccess. *boy i hate this editor* > Ah! something I actually *know* something about! 8-D Even FELs have pretty lousy efficiency. Assume yon FEL recovers uncoverted power from the "spent" e-beam for recycling. Considering power-balances, one has (pardon the psuedo-TeX notation): P_\lambda = \eta_{conv} P_{beam,in} P_\lambda := {power of light emitted} P_{beam,in} := {power of e-beam into FEL} \eta_{conv} := {e-beam-to-light conversion efficiency} P_{beam,in} = \eta_{acc} P_{acc} P_{acc} := {power consumed by accelerator} = P_{input} + P_{recov} P_{input} := {"wallplug" input power} P_{recov} := {power recovered from "spent" e-beam} \eta_{acc} := {accelerator "wallplug" efficiency} P_{recov} = \eta_{recov} P_{beam,out} P_{beam,out} := {power left in "spent" e-beam} = P_{beam,in} - P_\lambda = (1-\eta_{conv}) P_{beam,in} \eta_{recov} := {e-beam energy-recovery efficiency} Solving for P_\lambda in terms of P_{input}, I get: \eta_{acc} \eta_{conv} P_\lambda = ------------------------------------------------- P_{input} [ 1 - \eta_{acc} \eta_{recov} (1-\eta_{conv}) ] Best current "wallplug" efficiencies \eta_{acc} for "copper" accelerators are about 60%; recovery-efficiency \eta_{recov} about 90%; conversion- efficiency about 25% (try to load the beam more heavily than that and nonlinear harmonic-generation begins to dominate the light output). Total efficiency: about 25%. Assume a high-efficiency (60%) "topping cycle" Brayton or Rankine generator for your power supply; total system efficiency drops to only *15%* --- pretty stinky compared to 90+% for a simple mirror... You might argue that a *superconducting* linac provides superior efficiency; however the klystron driving the thing is only 70%--80% efficient, and since high-T_c superconducting cavities are so far not much better than copper, one must factor in the (significant!) power-cost of cryo-cooling the linac to "convetional" superconducting temperatures. Figuring the trade-offs isn't a back-of-the-envelope calculation so I won't attempt it; suffice it to say that even an *80*% "wall-plug" efficiency gives a total wallplug-to-light efficiency of only 43%. Having said all this, I must agree with your observation that "docking" a mirror to a rock *is* a nontrivial excercise, so *maybe* the FEL is still worth it. Also, rock-vapour at "solar-thermal" temperatures is likely to provide a pretty punk I_sp; one might boil most of the rock away in the process of bringing it home. *So*: use your FEL to zap the rock in the "laser-induced detonation" mode; this gives theoretical I_sp's in the 10--100 ksec (yes, that's *kilo*-second!) range... Bring that rock home to Mamma Terra... :-) Gordon D. Pusch P.S.: My contract has been extended for 2 mos (*again*), so I won't be leaving AECL until the end of 1993-Jan; however I'll be out of town until Dec-02, so I won't be able to respond to your flames until then... ;-) ------------------------------ Date: Fri, 20 Nov 92 21:48:32 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Thermoelectric conversion Henry stated that turbogenerators are more efficient that thermoelectric generators. There is one possible exception: the Alkali Metal Thermoelectric Convertor, or AMTEC. This device exploits a temperature gradient to pump sodium ion across a beta alumina solid electrolyte (the kind to be used in sodium-sulfur batteries). This electrolyte does not conduct electrons or neutral sodium atoms. Sodium loses electrons on the cold side, and is neutralized again on the hot side by a conductive grid on the electrolyte. Sodium atoms on the hot side evaporate, and are reliquified in a condensor. The molten sodium is pumped back to the cold side, either by gravity or by an electromagnetic pump. The only moving part in the whole thing is sodium. This is a thermoelectric device, as a thermal process is causing charged carriers -- sodium ions -- to move against an electrical gradient. Efficiencies of up to 45% are projected. For more information on the latest work, see the proceedings of the 1992 Intersoc. Energy Conv. Eng. Conf. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ To: dietz@cs.rochester.edu Cc: space-tech@cs.cmu.edu, gwh@soda.berkeley.edu Subject: Re: Thermoelectric conversion Date: Fri, 20 Nov 92 19:15:43 -0800 From: George William Herbert The Russian thermionic generator is comperable (roughly) in concept if not execution. The problem with these systems is that while they may be highly effecient and durable as hell (thermionic systems est. MTBF of 10+ years, which is the reactor pump lifetime... the thermal part should last 100 years...), they're pretty heavy for the power you get out. -george ------------------------------ From: henry@zoo.toronto.edu Date: Sat, 21 Nov 92 16:19:48 EST To: space-tech@cs.cmu.edu Subject: Re: Low-pressure O2 (was: RE: Lunar "colony" reality check) >As a counterpoint to that, recall that the undersea divers who work >in very high pressure environments (at 20% O2, with PPO2 in the many >many atmospheres level) are relatively healthy even with stays >up to months at pressure (depth). I think I want to see some references on this. The deep-sea projects I know about have used carefully-crafted air mixes bearing no particular relation to sea-level air. (For one thing, nitrogen becomes first an intoxicant and then an anesthetic at such pressures, so helium is usually substituted.) Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: henry@zoo.toronto.edu Date: Sat, 21 Nov 92 16:28:57 EST To: space-tech@cs.cmu.edu Subject: Re: Thermoelectric conversion >This is a thermoelectric device, as a thermal process is causing >charged carriers -- sodium ions -- to move against an electrical >gradient... Actually, some would debate (and Paul and I have in fact been debating, offline) whether this is "thermoelectric" in any sense in which a turbogenerator isn't. This is a concentration-gradient fuel cell; the use of heat, rather than chemical action, to create a concentration gradient is incidental. In any case, what it's called is second to the impressive efficiency. Similar fuel cells built in the past haven't done nearly as well. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Sat, 21 Nov 92 18:11 PST To: space-tech@cs.cmu.edu Subject: P2-E cousins From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) The material below was (I think) accidentally sent to Phil rather than being posted, about a week ago: > Phil G. Fraering writes: > > Is this your idea? For a while I thought I was looking > at George Herbert's latest revision... also, for a similar > design}i, look at the designs of... you know, that guy > whatshisname... If you remember who whatshisname is and where to find the information, please tell. I will avidly consume anything on the subject. Aside from George Herbert's design, the other two that I have on paper is the design for a very small "Liberty" vehicle by Gary Hudson, and a design by Wolf and Horne of Phoenix Engineering (circa 1983). The Hudson design uses LOX and kerosene, with aluminum tanks. Because the vehicle is small, the tank walls are a reasonable thickness. Pressurization is via gaseous helium from high pressure tanks kept inside the kerosene tank. He can get away with gaseous helium because he uses quite a low pressure (250 psi) and is willing to accept a rotten specific impulse in the atmosphere. The nozzle is ablatively cooled. Payload to orbit is about 0.25 ton. The Wolf design uses UDMH and N2O4, with pressurization by "main tank injection". The ullage space in each tank is filled with nitrogen at the beginning. UDMH is sprayed into the N2O4 tank and N2O4 is sprayed into the UDMH tank, with predictable results. The hot reaction products and the heated ullage gas provide the pressure. The authors note that because of the heat, the tank walls must be operated at a reduced stress. The lower stage tankage is HY-140 or maraging steel, and the nozzle is ablatively cooled. Gross liftoff mass is approximately 500 metric tons, and payload to LEO is approximately 7 tons. My design is independent of George Herbert's, although as he mentions there has been cross-fertilization. Below is a comparison of the two vehicles, using information posted by George in June with recent modifications by him. Apologies to George if I have any detail wrong. Item Dunn Herbert Tank material D6Ac steel high strength steel Tank yield strength 1340 MPa about 700 MPa Tank diameter 6 meters 1 meter Oxidizer H2O2 H2O2 (originally LOX) Fuel Propane solid hydrocarbon Pressurizing gas Helium ? Pressure gas heating Gas Generator Nozzle boiler Nozzle SRB derived ablative ablative Steering movable nozzle differential throttling # Lower stages 1 to 3 54 # Upper stages 1 6 LEO payload, tons 12 to 52 10 I think that George convinced me to back away from the costly and exotic maraging steel of my original design, while I convinced him of the virtues of peroxide as an oxidizer. -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ To: "Louis F. Adornato" Cc: cs.cmu.edu!space-tech@uunet.uu.net Subject: Re: Compare Russian RD170 engine to US F1 Date: Mon, 23 Nov 92 07:21:46 EST From: Chris Jones From: "Louis F. Adornato" Date: Fri, 20 Nov 92 08:59:53 CST The article says that the LOX/kerosene RD-170 is "considered the world's most powerful liguid fueled rocket engine", and that it has "a sea level thrust rating of 1.63E6 lbs with a growth potential to 1.76E6 lbs". There's no data on throttleability, restart capability, or firing time. The engine has an operational history of 16 Zenith and Energia flights. There's a breif mention of one Zenith launch failure due to an RD-171 (an RD-170 derivative), but the article quotes a rep from the manufacturer as saying that the problem was caused by a manufacturing failure, and not by a flaw in the engine or the manufacturing process (i.e., someone didn't follow the process). I have some information on the RD-170 from the July 23, 1990 issue of AW&ST: the engine can be reused in up to 10 flights (a capability which has never been used, to my knowledge). It has gradual acceleration and deceleration characteristics: it goes from 0% to 100% thrust "smoothly over a full 2 sec. interval", and decelerates from 100% to 70% over a 30 second interval, then to 50% in 2 seconds, stays at 50% for 10 seconds, then drops to 0% in 0.5 seconds. This is done to produce "less stress on the motor and the launch vehicle." The article says (love these units) that the "RD-170 achieves an unusually high pressure of 250 kg. of force/sq. cm. in the 480-kg. combustion chamber." It consumes 166.17 kg./sec. of kerosene and 432 kg./sec. of oxidizer, and burns for 140-150 seconds, including the acceleration and deceleration times. The article discusses more about the plumbing, development, and testing of the engine, saying that it's a very reliable engine (this was before the failure you mention) although its said they "are not completely satisfied with the current level of reliability and are already planning to develop a more reliable and economical version". ------------------------------ To: uunet!zoo.toronto.edu!henry@uunet.UU.NET Cc: space-tech@cs.cmu.edu, gwh@lurnix.COM Subject: Re: Low-pressure O2 (was: RE: Lunar "colony" reality check) Date: Mon, 23 Nov 92 13:31:23 -0800 From: gwh@lurnix.COM What I've seen on deep diving gas mixes indicates that 80% He / 20% Ox is the more common standard for mid depths and 80/20 Argon/Ox for deeper. Argon apparently has some problems of its own. But I've never seen any indication of serious changes in the ratio of filler gas to O2 from sealevel (~20% O2) conditions. Which indicates that the PPO2 is pretty high at depths. The point is sort of moot, though... 8-) High pressure is the enemy in spacecraft. Personally, I prefer lower pressures than SL (10-12 PSI) in craft, primarily to reduce prebreathe problems with low pressure suits. 10-12 PSI is a good tradeoff between prebreathe problems (pushing pressure lower) and equipment cooling and recertification costs (pushing sea level +- pressure). 12 PSI is about Denver if I recall right; 10.? is the top of Mauna Loa in Hawaii where the observatories are. They use relatively standard hardware up there. -george ------------------------------ To: space-tech@cs.cmu.edu Subject: Re: Low-pressure O2 (was: RE: Lunar "colony" reality check) Date: Mon, 23 Nov 1992 18:35:14 EST From: John Carr >> What I've seen on deep diving gas mixes indicates that 80% He / 20% Ox >> is the more common standard for mid depths and 80/20 Argon/Ox for deeper. >> Argon apparently has some problems of its own. A few years ago I read an article describing the effectiveness of inert gasses as anesthetics. I think there was good correlation with solubility in fat, and concerns that even Helium could be dangerous at high enough pressure. >> 10-12 PSI is a good tradeoff between prebreathe problems >> (pushing pressure lower) and equipment cooling and recertification >> costs (pushing sea level +- pressure). There are typically also humidity constraints. How difficult will humidity control be? There will be more volume than a spacecraft, and probably some very dry dust around to soak up water. I doubt the mass of water imported will need to be greater than the mass of air, so it shouldn't be a problem to transport it, but I'm not familiar enough with space life support systems to be sure. (This is assuming no lunar ice.) ------------------------------ Date: Mon, 23 Nov 92 15:52 PST To: space-tech@cs.cmu.edu Subject: RD170 vs. F1 From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) Chris Jones writes: > I have some information on the RD-170 from the July 23, 1990 issue of > AW&ST: the engine can be reused in up to 10 flights (a capability > which has never been used, to my knowledge). It has gradual > acceleration and deceleration characteristics: it goes from 0% to 100% > thrust "smoothly over a full 2 sec. interval", and decelerates from > 100% to 70% over a 30 second interval, then to 50% in 2 seconds, stays > at 50% for 10 seconds, then drops to 0% in 0.5 seconds. This is done > to produce "less stress on the motor and the launch vehicle." The > article says (love these units) that the "RD-170 achieves an unusually > high pressure of 250 kg. of force/sq. cm. in the 480-kg. combustion > chamber." It consumes 166.17 kg./sec. of kerosene and 432 kg./sec. of > oxidizer, and burns for 140-150 seconds, including the acceleration and > deceleration times. Doing some conversion to SI and digging up some information, the following comparisons can be made between the RD170 and F1: F1 RD170 Chamber Pressure, MPa 7.73 24.5 Mixture Ratio, oxidizer/fuel 2.60 2.27 Propellant Flow, kg/sec 2392 2605 Isp, vacuum 305 335 The "combusion chamber" at 480 kg must refers to 1 of 4 combustion chambers in the four barreled motor, as does the propellant flow. The propellant flow in table for RD170 is 4 times the amounts quoted by Chris, in order to give flow for the whole motor. The very high chamber pressure will allow a high expansion ratio to be used without flow separation when at sea level. This and the high chamber pressure (which supresses dissociation) will be the source of the high Isp. The higher mixture ratio (richer in dense oxidizer) is also probably attributable to the high chamber pressure, which allows a more stoichiometric mix to be used without excessive losses due to the increase dissociation at the resultant higher temperatures. -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ Date: Mon, 23 Nov 92 21:13:34 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: Diving gas mixes >From: John Carr >A few years ago I read an article describing the effectiveness of inert >gasses as anesthetics. I think there was good correlation with solubility >in fat, and concerns that even Helium could be dangerous at high enough >pressure. I've heard there's been speculation on using hydrogen for extreme pressures. Above a certain percentage, the mix stops being flamable. I *think* it's been tried in hyperbaric chambers. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Tue, 24 Nov 92 15:53:43 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Where is this program? Perhaps someone here could help me. I'm looking for an electronically readable copy of the program described in Gordon & McBride, "Computer Program for Calculation of Complex Chemical Equilibrium Compositions, Rocket Performance, Incident and Reflected Shocks, and Chapman-Jouquet Detonations", NASA SP-273 (1971). The report has a listing of the program and data, but that's too long to be helpful. Is the program (or a successor) available for FTP from somewhere? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Tue, 24 Nov 92 22:27 PST To: space-tech@cs.cmu.edu Subject: RD 170, F1 and P2E Comparison From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) This is a partial repost of previously distributed information, correcting an error (I had reversed the figures for the mixture ratio of the F1 and RD170) and redoing some awkward formatting. I have added some thrust information, and information on my proposed P2-E engine. Louis Adornato writes: > The article says that the LOX/kerosene RD-170 is "considered the > world's most powerful liguid fueled rocket engine", and that it has "a > sea level thrust rating of 1.63E6 lbs with a growth potential to 1.76E6 > lbs". Chris Jones writes: > I have some information on the RD-170 from the July 23, 1990 issue of > AW&ST: the engine can be reused in up to 10 flights (a capability which has > never been used, to my knowledge). It has gradual acceleration and > deceleration characteristics: it goes from 0% to 100% thrust "smoothly over > a full 2 sec. interval", and decelerates from 100% to 70% over a 30 second > interval, then to 50% in 2 seconds, stays at 50% for 10 seconds, then drops > to 0% in 0.5 seconds. This is done to produce "less stress on the motor and > the launch vehicle." The article says (love these units) that the "RD-170 > achieves an unusually high pressure of 250 kg. of force/sq. cm. in the > 480-kg. combustion chamber." It consumes 166.17 kg./sec. of kerosene and > 432 kg./sec. of oxidizer, and burns for 140-150 seconds, including the > acceleration and deceleration times. Doing some conversion to SI and digging up some information, the following comparisons can be made between the F1, RD170 and P2E: F1 RD170 P2E Sea Level Thrust, MN 6.76 7.24 13.5 Chamber Pressure, MPa 7.73 24.5 6 Mixture Ratio, oxidizer/fuel 2.27 2.60 7.5 Propellant Flow, kg/sec 2392 2605 5480 Isp, vacuum 305 335 290 est. The RD170 "combusion chamber" at 480 kg must refer to 1 of 4 combustion chambers in the four barreled motor, as does the propellant flow. The propellant flow in table for RD170 is 4 times the amounts quoted by Chris, in order to give flow for the whole motor. The very high chamber pressure in the RD170 will allow a high expansion ratio to be used without flow separation when at sea level. This and the high chamber pressure (which supresses dissociation) will be the source of the high Isp. The higher mixture ratio (richer in dense oxidizer) is also probably attributable to the high chamber pressure, which allows a more stoichiometric mix to be used without excessive losses due to the increase dissociation at the resultant higher temperatures. -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ End of Space-tech Digest #138 *******************