Date: Fri, 29 Sep 1989 17:46-EDT From: space-tech-request@cs.cmu.edu To: "~/st/lists/stdigest" Subject: Space-tech Digest #37 Contents: Mike Bird Re: home-built rockets Paul Dietz explosion hazards of hydrogen peroxide Paul Dietz Hybrid Rockets Henry Spencer Sutton Book Paul Dietz Re: Sutton Book Peter Scott Re: Lightweight mirrors Paul Dietz [Doug Price] NERVA with ET propellants Roger Arnold Re: NERVA with ET propellants Dunc Re: NERVA with ET propellants Paul Dietz Re: NERVA with ET propellants Roger Arnold Re: NERVA with ET propellants Steven Deterling Liquid motors, amateur rocketry, orbital debris... ------------------------------------------------------------ Date: Sun Sep 24 09:32:44 1989 CDT From: Mike Bird To: space-tech@cs.cmu.edu Subject: Re: home-built rockets In order to qualify as a model rocket, the entire rocket at lift-off must weigh less than a pound and have no metal parts. Only paper and plastic are legal. There's also a limit on the weight of the propellant. I have saved a discussion that went on a while back on sci.space and sci.space.shuttle about model rocketry. Here's an excerpt to answer the issue of liftoff weight (I just looked it up. I was wrong.) I also VERY STRONGLY recommend that ANYONE thinking of getting into Model Rocketry join the NAR (National Association of Rocketry) and a local Model Rocket Club (BAYNAR, NIRA, HARA, etc.). The NAR magazine "American Spacemodeling" is very helpful and interesting. The NAR can also give you the address of a local Model Rocket Club. National Association of Rocketry 2140 Colburn Drive, Dept. M Shakopee, MN 55379 Membership varies from $12 to $19 per year, depending on age. These prices may have increased, I don't have a current application right now. The NAR also provides $1,000,000 Liability Insurance to individual members to cover their Model Rocketry activities (as long as NAR safety rules were being followed) at a reasonable price (it was $11 per year the last I knew but this has probably gone up some). A couple of years ago the NAR increased the limits on the definition of a Model Rocket from 1 lb. (liftoff weight) and F engines to 3 lbs. (liftoff weight) and G engines. The last I had heard (about a year ago) the FAA was still discussing this change, but they might have OK'ed it by now. Anything over a G engine is NOT a Model Rocket!!! If anyone wants the whole discussion, (lot's of safety arguments about whether or not to make your own engines, as well as how model rocket engines can be perverted to terrorism), send to me and I'll e-mail it to you. If enough requests (>10) I'll post it. It's about 45Kbytes long. -- Mike Bird - B. Dalton, Bookseller UUCP: ...umn-cs!bungia!kksys!clavdivs!bird Helen Bird - Hummingbird Tailors Domain: bird@kksys.clavdivs.MN.ORG You can't call ME 'Books'! All opinions void where prohibited by law! ------------------------------ Date: Mon, 25 Sep 89 11:11:00 EDT From: dietz@cs.rochester.edu To: henry@zoo.toronto.edu Cc: space-tech@cs.cmu.edu Subject: explosion hazards of hydrogen peroxide >> I was under the impression that hydrogen peroxide cannot detonate, even >> if hit by a shock wave, but can decompose rapidly if heated to several >> hundred degrees C or if contaminated with any of a number of catalysts. >Peroxide can explode if pushed hard enough. Sutton (5th ed) cautions that >it must not be allowed to get too hot, or the rapid decomposition gets >into a positive-feedback region and becomes an explosion. He also observes >that almost any random contaminant will catalyze peroxide decomposition, >and indeed slow decomposition can be expected when the stuff is stored. I think we should distinguish between runwaway thermal decomposition and detonation. The latter is a different phenomenon, involving the propagation of a detonation wave. I looked up some information on H2O2 in an encyclopedia of chemical engineering... Decomposition and Explosion Hazards Hydrogen peroxide decomposes with the generation of heat and oxygen. Decomposition is promoted by catalytic impurities and proceeds at a rate that increases approximately 2.2 times for each 10 degree rise in temperature over the range 20-100 deg. C. The decomposition can become self-accelerating and must be controlled for safe storage and handling of hydrogen peroxide. Containers and equipment should be constructed of suitable materials, be adequately vented, and maintained free of contaminants. Decomposition hazards increase with increasing concentration. It is reportedly impossible to obtain a propagating detonation of commercial hydrogen peroxide at ambient temperature under normal conditions of storage. Concentrations of 86% and above detonate, but only with a high energy ignition source. In the vapor phase, explosions occur under certain conditions. The lower explosive limit at atmospheric pressure is about 26% mol % H2O2 which is equal to the equilibrium vapor concentration over a boiling solution of ca 75% H2O2. Explosive vapor concentrations with 90% H2O2 can be avoided by maintaining temperatures below ca 115 deg C. 2.2 times per 10 deg C is an increase of about 24 times from 20 to 100 C. I would store the peroxide in vented containers in a water bath to add thermal inertia and permit cooling by evaporation of the bath. The boiling point of hydrogen peroxide itself is 150 deg. C. It goes on to say that stoichiometric mixtures of peroxide and organic compounds are sensitive and explosive. I have read that the Germans in WWII experimented with a mixture of hydrogen peroxide and methanol as a monopropellant, but could not stabilize it sufficiently. (I wonder about the implications of this for airliners screening for nitrogenous explosives.) Henry mentioned before that commercial hydrogen peroxide is 30%. Actually, I think this is reagent grade; other commercial peroxides are available in higher concentrations (these may include stabilizers). However, 30% peroxide could be concentrated by vacuum distillation or by freezing. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Tue, 26 Sep 89 07:31:46 EDT From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Hybrid rockets Henry commented that a problem in hybrid rockets is the difficulty in getting the solid fuel to burn evenly. It occurs to me that this could be solved by breaking the motor into two parts. The upper part contains the fuel. It is burned with a bit of oxidizer, producing a relatively low temperature, underoxidized gas. The temperature is low enough for wall erosion to not be a problem. The gas flows into the second part, where the majority of the oxidizer is added and full combustion occurs. This combustion chamber would have to be cooled. A variant on this idea is to replace the first part with a solid rocket with less than the normal amount of solid oxidizer. Liquid oxidizer would still be used in the second part. If the solid fuel is properly formulated it could be made to stop burning when the liquid oxidizer is cut off (which would cause the pressure in the top part to drop). Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: henry@utzoo.uucp To: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Sutton book Date: Wed, 27 Sep 89 11:26:02 EDT A couple of people have inquired about the specifics of the Sutton book I keep citing, so here it is: George P. Sutton, "Rocket Propulsion Elements", 5th ed, Wiley-Interscience 1986, ISBN 0-471-80027-9. I don't know precisely what it would cost, but if you think $50 you won't be far wrong. (It's not that big a book, but it's a textbook for a rather limited market.) Unless you're near some place like MIT, you probably won't find it on the shelves of your local bookstore, but any decent bookstore can special-order any book that's in print. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Wed, 27 Sep 89 17:32:42 EDT From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: Sutton book Henry Spencer wrote: > A couple of people have inquired about the specifics of the Sutton book > I keep citing, so here it is: > George P. Sutton, "Rocket Propulsion Elements", 5th ed, > Wiley-Interscience 1986, ISBN 0-471-80027-9. > I don't know precisely what it would cost, but if you think $50 you won't > be far wrong. I just ordered a copy -- the price is $49.95+shipping. I got a 10% discount off that for some reason. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Thu, 28 Sep 89 11:28:12 PST From: Peter Scott Subject: Re: Lightweight mirrors To: space-tech@cs.cmu.edu X-VMS-Mail-To: EXOS%"space-tech@cs.cmu.edu" John Roberts writes: >Any large, thin-walled inflated object in space will eventually lose enough >of its gas through meteorite punctures and/or diffusion that it will lose its >shape. (I assume that's what happened to the Echo satellites, if they didn't >burn up first.) To assemble a really large reflecting surface in space, it >*might* be practical to inflate a pre-formed balloon, then spray the back of >the surface with a stiffening agent. A passive or active support structure >could possibly be added behind the surface. Precision would seem to be limited >only by the degree of control available. (How about a 100' open-frame telescope >at L5? :-) Side note here: Robert Forward's design for a solar-pumped laser operating around the orbit of Mercury (rated in the Terawatt range) included a lens on the order of kilometers across using a mesh held up by an aerosol. Afraid my memory's a little rusty on this, so I don't recall specific construction details if they were mentioned. The laser was for propelling a starship. Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: Thu, 28 Sep 89 11:44:33 EDT From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: NERVA with ET propellants You probably saw this message on sci.space, but here it is again... >From: price@chinet.chi.il.us (Doug Price) Newsgroups: sci.space Subject: NIMF proposal from Martin Marietta Keywords: NERVA rocket nuclear mars propellant Message-ID: <9681@chinet.chi.il.us> Date: 27 Sep 89 04:55:09 GMT Organization: Chinet - Chicago, Ill. Lines: 90 I have a copy of "The NIMF - Nuclear Rocket Using Indigenous Martian Fuel," by Robert M. Zubrin of Martin Marietta. As has been noted earlier, this is a fascinating paper on the use of NERVA-style nuclear rockets for missions to Mars and beyond. The most striking thing about this paper is that it completely turns the economics of interplanetary travel upside down. Of course, the word "nuclear" strikes terror into the hearts of all those neo-Luddites out there, so let's deal with the negatives before the positive components, and take a look at some of the salient comments in the paper: "... set against all these advantages (sic) for the NIMF is the fact that the NIMF carries a nuclear reactor. However the NIMF reactor carries a radioactive inventory about 6 orders of magnitude less than a power reactor, which will not only be a relief to the Martian Environmental Protection Agency, but eliminates the central engineering headache of nuclear reactors, to wit the possibility of meltdown caused by radioactive decay heat if cooling is lost. This small radioactive inventory represents a small hazard compared to that presented by the chemical alternative to the NIMF (a chemically powered lander, - DHP) which will be virtually a flying bomb, a lightly built structure filled to the gills with toxic gas and chemical high explosive." I talked to Zubrin at the Space Development Conference about the level of radioactivly that could be expected in the NIMF reactor at its return to earth orbit, and he said basically that the reactor operates for such a short period over its entire life that its total residual radioactivity amounts to the tens of curies. The worst case scenario of an uncontrolled burn-up in earth's atmosphere after one or more Martian missions would be trivial (though, of course, there are plenty of people out there that would find this concept horrific as well.) So, now that the "nuclear" debate has hopefully evaporated in a puff of logic, lets get on to the good stuff; what can this technology do for us? First, the basic parameters of the NIMF. Here is a table of ideal specific impulses for the variously available Martian propellants: Temperature CO2 H2O Methane CO or N2 Argon 2800K 283 370 606 253 165 3000K 310 393 625 264 172 3200K 337 418 644 274 178 3500K 381 458 671 289 187 2800K temperature output was demonstrated with NERVA. 3000K appears to be attainable with appropriate modernization of the NERVA technology. 3200K is possible with the use of modern ceramic fuel elements. 3500K can be considered the theoretical upper limit with a solid core nuclear rocket. CO2 is the easiest propellant to use, as it constitutes 95% of the Martian atmosphere. The specific impulse is on the same order as Oxy/Hydrogen chemical rockets, BUT, the point is that this reaction mass is easily available at the destination, rather that having to drag it all the way from earth. The electrical cost of liquifying the CO2 from the atmosphere is 84 kilowatt/hours per metric ton. The thermal output of the reactor would be on the order of 1000 Megawatts, so putting a relatively modest electical generation capability aboard the spacecraft would permit the NIMF to reload its reaction mass in extremely short order (Zubrin sights a figure of 14 hours for a 40 metric ton spacecraft with 1 Megawatt of electrical generating capacity.) Using indigenous propellants, the NIMF can hop all over the planet, as many times as it wants, while a chemically powered lander would only be able to land in one place, and be electically impoverished as well. Just think of what a rover vehicle could do if it had virtually unlimited electrical power from the lander. And here is one of the most interesting points. If water is used as the reaction mass, the NIMF can launch from Mars directly back into an earth return trajectory! While we could not depend on the availability of water on the first missions, later ones might be able to take advantage of this increase in specific impulse. NERVA style rockets used as interplanetary tugs could achieve specific impulses of 950 with hydrogen as the propellant. There are lots of other details in the paper related to the relative tradeoffs of specific mission profiles, propellant provisioning, spacecraft configurations, and possible multiple visits and sample returns from the outer planets (and a profile for a sample return from the surface of Venus!) Anyway, recommend that you send to Zubrin himself to get a full copy of the paper. Unfortunately, I believe the politics of the "N" word may easily put the kabosh on the whole thing. -- Douglas H. Price price@chinet.chi.il.us price@vfrot.chi.il.us -- Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: telesoft!roger@ucsd.edu (Roger Arnold @prodigal) Date: Thu, 28 Sep 89 11:17:58 PDT To: dietz@cs.rochester.edu Subject: Re: NERVA with ET propellants Cc: space-tech@cs.cmu.edu > >From: price@chinet.chi.il.us (Doug Price) > > I have a copy of "The NIMF - Nuclear Rocket Using Indigenous Martian Fuel," > by Robert M. Zubrin of Martin Marietta. [..] > > First, the basic parameters of the NIMF. Here is a table of ideal specific > impulses for the variously available Martian propellants: > > Temperature CO2 H2O Methane CO or N2 Argon > > 2800K 283 370 606 253 165 > 3000K 310 393 625 264 172 > 3200K 337 418 644 274 178 > 3500K 381 458 671 289 187 The numbers in this table don't make a lot of sense to me. I thought ISP should be mostly a function of the chamber temperature and the average molecular weight of the exhaust gasses. CO and N2 should be higher than CO2. I can't see any reason for methane to be so much higher than the others, unless it is decomposing to H2 and HC radicals. Maybe there's something else operating here that I'm not considering. The higher performances are for more complex molecules, which have more vibration modes available for storing and releasing thermal energy. Ugh! I never did like thermodynamics, but I may have to dig out my old text and do some actual work. > [..] The thermal output of the reactor would be on the order of > 1000 Megawatts, so putting a relatively modest electical generation capability > aboard the spacecraft would permit the NIMF to reload its reaction mass in > extremely short order [..] Thermal output from a NERVA type reactor and electrical output are very different matters. The NERVA reactors that were tested in the 60's had no capability for generating any electrical output at all. I suppose that a reactor could be designed in which the thermal output could be tapped for electrical power generation, but it would certainly make the reactor heavier and reduce its rocket performance. > Using indigenous propellants, the NIMF can hop all over the planet, as many > times as it wants, while a chemically powered lander would only be able to > land in one place, and be electically impoverished as well. [..] Nice idea, but it wouldn't work with a NERVA style reactor. Thrust to weight ratio isn't good enough to lift off, even from Mars. You'd gain something in that department from using a heavy reaction gas (like CO2) with low ISP (compared to H2), but you'd loose as a result of the much lower thermal conductivity. You might be able to bring it off with a DUMBO style reactor. I have some interesting references relating to DUMBO vs. NERVA that I will try to dig up. I presume they'll be of general interest to this group. > [..] Unfortunately, I believe the politics of the "N" word may > easily put the kabosh on the whole thing. > > -- > Douglas H. Price > price@chinet.chi.il.us > price@vfrot.chi.il.us I can get very irate over the politics of the "N" word, myself, but I think Zubrin's proposal may go too far in the other direction. I'm no expert on nuclear reactors, but I don't think it's possible to build them with arbitrarily low inventories of fissile material. The military space power reactors that I've read about use marginally subcritical masses of U235 or Plutonium. That's how they get high power output from a small package. The presence of moderators and berilium neutron reflectors does reduce the mass of fissile material required, but I don't think you can get by with much less than would be found in a tactical nuclear weapon. And certainly the radiation from an operating NERVA or DUMBO reactor is nothing to take lightly. (In fact, it has to be taken with a "heavy" dose of lead shielding, if your vehicles are to carry any living crew.) I should emphasize that I'm only responding to Price's reporting of Zubrin's paper. I haven't read the paper myself, and it's entirely possible that my reservations are addressed there. - Roger Arnold ucsd!telesoft!roger ------------------------------ Date: Thu, 28 Sep 89 15:00:10 PDT From: dunc@Sun.COM (duncs home) To: space-tech@cs.cmu.edu Subject: Re: NERVA with ET propellants >From mnr@DAISY.LEARNING.CS.CMU.EDU Thu Sep 28 14:12:35 1989 > ... >Thermal output from a NERVA type reactor and electrical output are >very different matters. The NERVA reactors that were tested in the >60's had no capability for generating any electrical output at all. >I suppose that a reactor could be designed in which the thermal >output could be tapped for electrical power generation, but it would >certainly make the reactor heavier and reduce its rocket performance. Perhaps the rocket itself could be throttled down and run as an MHD generator. With three orders of magnitude between the thermal energy available and the electrical energy desired it needn't be very efficient. --Dunc ------------------------------ Date: Thu, 28 Sep 89 19:53:35 EDT From: dietz@cs.rochester.edu To: telesoft!roger@ucsd.edu Cc: space-tech@cs.cmu.edu Subject: NERVA with ET propellants Roger Arnold criticized the idea of using a nuclear thermal reactor for electricity generation. I have not read the article, but it seems clear to me that the idea would be to run the reactor at reduced power, say 10 MW, and use a compact system -- say a thermoelectric generator -- to make 1 MW or so of power. NERVA was my interpolation; I don't think the original message said NERVA, just nuclear. About how much fissionable material is required: a thermal reactor requires much less fissionable material (if pure) than a bomb. I forget the exact number, but less than a pound of U235 nitrate dissolved in water can go critical. Also, a reactor that is not designed to operate at full power for a long time can carry less fuel -- burnup will not be significant. Paul ------------------------------ From: telesoft!roger@ucsd.edu (Roger Arnold @prodigal) Date: Fri, 29 Sep 89 11:02:09 PDT To: dietz@cs.rochester.edu Subject: Re: NERVA with ET propellants Cc: space-tech@cs.cmu.edu > Roger Arnold criticized the idea of using a nuclear thermal reactor > for electricity generation. I have not read the article, but it > seems clear to me that the idea would be to run the reactor at > reduced power, say 10 MW, and use a compact system -- say > a thermoelectric generator -- to make 1 MW or so of power. Uhmm, I'd be happier if you had said I "questioned" it, rather than "criticized". My point was only that the design requirements for a reactor intended to power a reaction engine at a thrust to mass ratio sufficient for use in a Mars lander are very different from those for a reactor intended to generate electrical power. Merging the two is going to require compromises. Achieving the thrust to mass ratio needed to operate a Mars lander will be technologically challenging, at best; NERVA didn't come close. Carrying along an inefficient, high power electrical generating system won't make it easier. How "compact" a system capable of delivering 1 MW of power really be? Especially if it is operating at only 10% efficiency. It seems to me that it would take a pretty hefty heat exchanger/radiator to dump 9 MW of waste heat, even into the Martian atmosphere. My personal feeling is that a nuclear reactor providing both thermal power for reaction engines and mission electrical power makes great sense--for the Earth to Mars transfer ship. Thrust to mass ratios don't count for a lot there. But for a lander? Maybe, but I'd have to be convinced. > NERVA was my interpolation; I don't think the original message said > NERVA, just nuclear. Which brings me back to the subject of DUMBO. I haven't dug up those references yet, but since I've had inquiries, I'll say just a few words about what DUMBO is (or was). DUMBO was a competitive design to NERVA, in the late fifties. Its key feature was a very large surface to mass ratio in the reactor heat exchanger. I don't have the figures, but the ratio was least a couple of orders of magnitude higher than for the NERVA design. It would have translated into a sufficient thrust to mass ratio for the engine to be used in a single stage earth to orbit shuttle. There was apparently a lot of political in-fighting between the NERVA and DUMBO factions within the nuclear engine program. NERVA was the concept first advanced, by those who came to hold senior positions in the program. DUMBO was an upstart design. Ultimately, a decision was made to build NERVA, and to scrap DUMBO. The rationale was that high thrust to mass wasn't needed for the "space tug" role that the nuclear engine program was directed toward, and NERVA was a more conservative design, much likelier to succeed, within the cost and schedule constraints of the program. (Hmm, seems I've heard that one, before. Probably goes all the way back to ancient Egypt.) - Roger Arnold ucsd!telesoft!roger ------------------------------ Date: Thu, 28 Sep 89 10:37 CDT From: Subject: Liquid motors, amateur rocketry, orbital debris... To: space-tech@cs.cmu.edu X-Original-To: net%"space-tech@cs.cmu.edu", SPD7924 Hello, I have really been enjoying the discussion lately about model rocket engines and liquid rocket engines. I just had a course here at A&M (rocket propulsion) in which we used Suttons book. It is a very nice book. I will also throw my support behind the idea of being very careful when working with homemade liquid fuel rockets. They can be very dangerous if not handled properly, and tragic accidents can result. Also, if something tragic does happen, it makes the whole model rocket community look bad and gives the congresscritters another reason to try and regulate something. The publicity just isn't good for the average home rocket builder. I didn't realise that the NAR was trying to move up to G motors. I guess I need to renew my membership to find out what has been going on lately. As far as making or using more powerful than G engines goes, I once heard of something termed "Amateur Rocketry". From what I understand, this is the next higher level of home built model rocketry type things. Amateur rocketry supposedly has guidelines simliar to model rocketry and covers engines from G class up to something like R or S class (I am not sure where it stops). It allows the use of metal and is in general more sophisticated than model rocketry. I really don't know much more about it, if anyone else has heard of it maybe they can provide more info. I am also working on a project here at A&M this semester and am wondering if this group has any suggestions or information to offer. We are trying to design a mission (or set of mission) for the purpose of removal of orbital debris. Any ideas would be greatly appreciated. Also, if anyone has handy the data on current world launch capabilities (i.e. what weight and volume to what orbits on what rockets), that would be very much appreciated. References on where to find this data as concisely as possible would be great, too. Keep 'em flying! Steven Deterling Bitnet: SPD7924@TAMVENUS ------------------------------ End of Space-tech Digest #37 *******************