Date: Sun, 24 Sep 1989 16:13-EDT From: space-tech-request@cs.cmu.edu To: "~/st/lists/stdigest" Subject: Space-tech Digest #36 Contents: Henry Spencer Re: Lightweight mirrors Henry Spencer Re: Homemade liquid fueled rockets [legality,safety] Korac MacArthur Re: Homemade liquid fueled rockets [legality,safety] Henry Spencer Re: Homemade liquid fueled rockets [legality,safety] John DuBois Re: Homemade liquid fueled rockets [legality,safety] Paul Dietz Re: Homemade liquid fueled rockets [legality,safety] Henry Spencer Re: Homemade liquid fueled rockets [legality,safety] Paul Dietz fuels for rockets (with peroxide) Henry Spencer Re: fuels for rockets (with peroxide) Paul Dietz Re: fuels for rockets (with peroxide) Henry Spencer Re: fuels for rockets (with peroxide) Matthew Francey home-built rockets [control] ------------------------------------------------------------ From: henry@utzoo.uucp To: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Re: Lightweight mirrors Date: Fri, 22 Sep 89 14:57:26 EDT > ...I used to wonder whether a slack rope on earth would assume the form of > a parabola. I eventually found out that it does not (I *think* the shape it > forms is a hyperbola).... No, not a hyperbola, it's a catenary, which is a more complex curve. The cables on a suspension bridge *are* a parabola; the difference is whether the weight is constant per meter along the cable or horizontally (the bridge cables weigh essentially nothing compared to the horizontal roadway that they support). > ... 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... Seems practical. There were a couple of experimental radar-reflector satellites, a while after the Echos, which were wire-mesh spheres deployed by inflation -- the mesh was imbedded in a plastic film which decomposed when exposed to sunlight. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ From: henry@utzoo.uucp To: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Re: Homemade liquid fueled rockets Date: Fri, 22 Sep 89 14:57:27 EDT > ... I was thinking the > first step would be small engines, burning maybe a few ounces of > propellant for a few seconds -- the liquid or hybrid equivalent of > model rocket engines. Would ground tests violate fire codes? Surely > not if performed at a remote location. Fire codes probably wouldn't be an issue, but odds are that tests of any kind of rocket engine legally qualify as handling of explosives. (Model rockets using factory-built engines have a special exemption, as I recall.) Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Fri, 22 Sep 89 16:04 EDT From: Subject: Liquid fuel rockets To: space-tech@cs.cmu.edu X-Original-To: space-tech@cs.cmu.edu, K_MACARTHUR Yes, plenty of legal barriers are in the way of private investigations of many subjects. In the old days you just set something off at some remote locale and hoped it worked. The worst that could have happened to you legally was the farmer 5 miles down the road complaining that your exploded rocket scared his cows, and he would threaten to call the sherriff if it continued. Nowadays you have to have a license practically to sneeze in a crowded room. The initial reasoning for legislation was to protect the masses from themselves, keep the kids from playing with dads dynamite for stumps or black powder homemades that start forest fires. Now it is supposedly so terrorists won't make rockets, as well as the kids down the block. Any respecting terrorist has ready access to mil-spec variety rockets and bombs, thanx to various arms dealers and lunatic fringe countries. The only way to do home hobby liquid fuel rockets is illegally. If you are really into it, study it well before models are made, and build a real good blockhouse in the ground to experiment in, and pay your health insurance premiums, just in case. :) I think I'll stick to the books for now. Maybe some private research group could be formed to obtain all the necessary permits, etc. to do anything real. It would have to be supervised by someone who knows a lot about the subject to get the OK to do such research. I think the military/industrial complex has it all stacked their way to prevent just such ventures. Who knows? Korac MacArthur "Go for throttle up....." ------------------------------ From: henry@utzoo.uucp To: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Re: fuels for rockets Date: Sat, 23 Sep 89 02:59:43 EDT > Correct me if I'm wrong, Henry, but I seem to recall hearing that > H2O2 and H3N were used in the early X15 rocket engines. Or maybe > it was H2O2 and methanol? That's another fairly benign choice. > Later X15 models used a more powerful engine, with liquid oxygen... Alas, not quite right. Both the interim and definitive X-15 engines burned ammonia and LOX. Hydrogen peroxide was used for powering the pumps and for high-altitude attitude control. (I just looked this up to confirm.) A word of caution to the optimists: the X-15 had several in-flight fires and at least one on-ground engine-test explosion. I should explain that I don't want to discourage anyone from trying to build actual hardware. The point of the cautions about safety is that if you want to survive the experience intact, you need to take a really professional attitude to the operation. That means, in particular, that you expect explosions, and make very sure that you're never in a position to get hurt by one. Or, lots worse, hurt an innocent bystander. It does not take very much explosive -- e.g., mixed fuel and oxidizer -- to make a very nasty explosion that can ruin your whole day. Military hand grenades usually contain under 100 grams of explosive... and LOX mixed with anything organic is a more powerful explosive than anything they fill grenades with. (Hypergolic fuels have the advantage that it's hard to make them mix enough to explode... but beware of unstable materials like hydrazine or H2O2 that can explode all by themselves when hit by a shock wave.) Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Sat, 23 Sep 89 05:14:19 EDT From: spcecdt@ucscb.UCSC.EDU (Space Cadet) To: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Re: fuels for rockets >The point of the cautions about safety is that >if you want to survive the experience intact, you need to take a really >professional attitude to the operation. That means, in particular, that >you expect explosions, and make very sure that you're never in a position >to get hurt by one. I can second this, as someone who has learned the hard way that experimenting in an unprofessional manner with rocket fuels is a good way to seriously maim yourself. I've had two of them explode in my face. The first (which used homemade black powder) broke a blood vessel in my left eye; a bit more force behind whatever it was that hit it would've blinded me. The second (polyurethane + ammonium perchlorate) put me in the hospital. I ended up with $700 in medical bills (with a $2k insurance dedictible :-( ). Magnets now stick to my hand (yes, seriously). Be *careful* - I am, now. Wish it hadn't taken that last one to convince me. I consider myself very fortuate that I still have the full use of my eyes and hands. John DuBois spcecdt@ucscb.ucsc.edu ...!ucbvax!ucscc!ucscb!spcecdt ------------------------------ Date: Sat, 23 Sep 89 08:21:40 EDT From: dietz@cs.rochester.edu To: henry@utzoo.uucp Cc: cs.cmu.edu!space-tech@cs.toronto.edu Subject: fuels for rockets > The point of the cautions about safety is that if you want to >survive the experience intact, you need to take a really professional >attitude to the operation. That means, in particular, that you expect >explosions, and make very sure that you're never in a position to get >hurt by one. Absolutely right. In particular: all tests should be done in a pit shielded by thick earthen walls. *You* should be some distance away in the blockhouse, looking at the computer/closed circuit TV. The system should be designed so dangerous conditions can be safed and fuels purged remotely. When manipulating toxic/dangerous compounds, you should wear complete protective gear, and have a water spray handy. > but beware of unstable materials >like hydrazine or H2O2 that can explode all by themselves when hit by >a shock wave.) 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. Any fuel system using it must be designed to avoid buildup of excess pressure, and organic contaminants must be excluded. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: henry@utzoo.uucp To: uunet!cs.rochester.edu!dietz@cs.toronto.edu Cc: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Re: fuels for rockets Date: Sat, 23 Sep 89 18:51:46 EDT > 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. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Fri, 22 Sep 89 15:10:53 EDT From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Cc: telesoft!roger@ucsd.edu Subject: fuels for rockets (with peroxide) Roger Arnold suggested peroxide + ammonia as a fuel for amateur rockets. I looked up some information on various fuels. The figures in parentheses are the differences in heats of formation between a stoichiometric mixture of fuels and the products of their complete combustion. Heats of formation are measured at about 25 C. Water is assumed to be in the exhaust in the form of steam. I have ignored the heat lost in evaporating pressurized liquid propane or ammonia. (1) Hydrogen peroxide monopropellant (1.596 kJ/g) Pure H2O2 has a chamber temperature of 1250 K and Isp of 146 s at a 20-1 pressure ratio. The Isp is low, but H2O2 engines are very simple. Decomposition can be catalyzed by permanganate, manganese dioxide, silver, iron oxide or platinum. Aqueous solutions of H2O2 have lower performance. 87% H2O2 + 13% water gives a chamber temperature of 930 K and Isp of 126 s (at the same pressure ratio, I think). The theoretical Isp of 90% H2O2 is 147 s. Hydrogen peroxide decomposes if heated and has a high freezing point. Oxides of many metals catalyze its decomposition. Concentrated peroxide spilled on iron, concrete, dust or clothing may result in explosion if the liquid is partially confined. It is practically inert in contact with certain aluminum alloys, polyethylene or teflon. (2) H2O2 + polyethylene hybrid rockets (6.98 kJ/g) (The specific energy is actually for the alkane eicosane, C20H42.) This combination actually has fairly respectable performance. With a 6.7:1 oxidizer/fuel ratio, the chamber temperature is 3000 K. At a chamber pressure of 1000 psi, the sea level Isp is 277 s. The performance of this combination could be enhanced by adding light metal or light metal hydrides to the polyethylene. Beryllium hydride gives the best increase, but is ruled out due to the toxicity of Be compounds. Next best is lithium hydride. I imagine the LiH would be encapsulated inside the plastic. Aluminum would have the advantage of not being unstable if exposed to air. I wonder if AMROC uses, or plans to use, light metal additives in their rubber-LOX hybrid rockets. Mixing lithium (say) into a conventional solid rocket fuel sounds like a recipe for disaster, but hybrid rocket fuel has no oxidizer. (3) H2O2 + propane (7.2 kJ/g) (4) H2O2 + ammonia (5.86 kJ/g) The peroxide-ammonia combination is less energetic than propane, but as Roger suggested the ammonia would be better suited to regenerative cooling due to lack of coking. Even if ammonia was thermally decomposed to nitrogen and hydrogen, this reaction is endothermic, which I'd imagine is beneficial (as long as the hydrogen does not damage the metal). (5) H2O2 + methanol (6.64 kJ/g) The Germans studied this as a monopropellant during WW2, but could not stabilize it sufficiently. A drop of permangenate would cause it to explode. As a bipropellant it looks inferior to other choices of fuels. ---- >From these examples, I'd conclude that a hydrogen peroxide-polyethylene hybrid rocket would be interesting for an amateur group attempting to build a small motor. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: henry@utzoo.uucp To: cs.cmu.edu!space-tech@cs.toronto.edu Cc: uunet!cs.rochester.edu!dietz@attcan.uucp, uunet!ucsd.edu!telesoft!roger@attcan.uucp Subject: Re: fuels for rockets (with peroxide) Date: Sat, 23 Sep 89 03:30:02 EDT > I wonder if AMROC uses, or plans to use, light metal additives in > their rubber-LOX hybrid rockets... There have been hints of proprietary details in their fuel. On the other hand, they make a big deal out of how their fuel is just rubber and oh-so-safe to transport (while never mentioning the LOX...!), so perhaps not. >From these examples, I'd conclude that a hydrogen peroxide-polyethylene >hybrid rocket would be interesting for an amateur group attempting >to build a small motor. It might be worth a try. On the other hand, I've never really understood Amroc's fascination with hybrids. They're not easy to build well. Sutton ("Rocket Propulsion Elements", a book I highly recommend, and it's *in* *print* unlike some other good ones...) observes that burning rate is hard to predict, it is very difficult to avoid localized high burn rates, there are problems getting the oxidizer sufficiently well-distributed and in sufficiently intimate contact with the fuel for efficient burning, and there are the devil's own list of variables involved. Sutton does mention a possibly interesting fuel combination: red fuming nitric acid plus polybutadiene/polymethylmethacrylate. RFNA is a bit ugly (it's nitric acid with some nitrogen dioxide dissolved, and the NO2 is volatile and poisonous), but straight concentrated nitric acid is a good possibility. Frankly, I would much rather handle it than concentrated H2O2; at least the acid can't explode. Nitric acid is the only big-league oxidizer that I would unhesitatingly handle without major safety paranoia. (I have handled concentrated nitric acid, in fact; you just have to be a bit careful about spills.) I strongly suspect that it's much the easiest to obtain, also. (Industrial H2O2 is only about 30% peroxide, against 70%+ for rocket use; the stuff you buy in drugstores is 3%. The less said about getting N2O4, the better. LOX is in fairly routine use for things like oxygen systems, but may still be awkward to get for unspecified sinister purposes. :-)) (Polybutadiene is synthetic rubber; polymethylmethacrylate is Plexiglas.) Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Sat, 23 Sep 89 10:34:05 EDT From: dietz@cs.rochester.edu To: henry@zoo.toronto.edu Cc: space-tech@cs.cmu.edu Subject: fuels for rockets (with peroxide) > It might be worth a try. On the other hand, I've never really understood > Amroc's fascination with hybrids. They're not easy to build well. > Sutton ("Rocket Propulsion Elements", a book I highly recommend, and it's > *in* *print* unlike some other good ones...) observes that burning rate > is hard to predict, it is very difficult to avoid localized high burn > rates, there are problems getting the oxidizer sufficiently well- > distributed and in sufficiently intimate contact with the fuel for > efficient burning, and there are the devil's own list of variables > involved. Aside from the advantages listed by Sutton, I can think of several reasons why an amateur effort might like hybrid rockets over liquid rockets. First, you only need to feed one fluid into the combustion chamber, which reduces the number of valves, sensors, regulators, pumps, etc. in half. Second, combustion chamber cooling is much less of a problem -- the walls are covered with fuel, which ablates. Granted, the nozzle still has to be cooled (Amroc uses an ablative nozzle, no?). The problem with even burning sounds like a *design* problem to me; once Amroc solves it, they reap the benefits of a simpler system. The biggest limitation would be the empty mass of the motor, I think. > but straight concentrated nitric acid is a good > possibility. Frankly, I would much rather handle it than concentrated > H2O2; at least the acid can't explode. But nitric acid is more corrosive than peroxide, I think. Solve that and I might agree with you. However, I would still be a safety paranoid with any concentrated acid. The edition of Sutton in front of me (3rd, 1963) says nothing about nitric acid for use in hybrid rockets. Which edition do you have? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: henry@utzoo.uucp To: uunet!cs.rochester.edu!dietz@cs.toronto.edu Cc: cs.cmu.edu!space-tech@cs.toronto.edu Subject: Re: fuels for rockets (with peroxide) Date: Sat, 23 Sep 89 18:51:44 EDT > ...[in hybrids] combustion chamber cooling is much less of a problem > -- the walls are covered with fuel, which ablates... Assuming that said ablation is even -- otherwise you get exposed walls in places while others are still burning. (This is one of the reasons why the standard hybrid problems with uneven burning are serious.) > nozzle still has to be cooled (Amroc uses an ablative nozzle, no?). I believe that's correct. > >... I would much rather handle [nitric acid] than concentrated > > H2O2; at least the acid can't explode. > > But nitric acid is more corrosive than peroxide, I think. Solve that > and I might agree with you. However, I would still be a safety > paranoid with any concentrated acid. Don't be too sure about the corrosion angle; almost any impurity in contact with peroxide causes decomposition, releasing oxygen... and raw oxygen is second to very few things as a corrosive. Materials are a tricky problem for either. Agreed that concentrated acid has to be handled with some care, especially if you're putting it under pressure in plumbing. However, speaking as someone who has handled acids -- I was halfway to a degree in chemistry when I got sidetracked into computers -- concentrated nitric acid is one of those things that just requires a bit of care and forethought, while concentrated peroxide would scare me. > The edition of Sutton in front of me (3rd, 1963) says nothing about > nitric acid for use in hybrid rockets. Which edition do you have? The fifth edition, 1986 I think, which is the current one. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ To: space-tech@cs.cmu.edu Subject: home-built rockets Date: Sat, 23 Sep 89 17:13:47 EDT From: mdf@ziebmef.mef.org Since making liquid fuel engines seems to be Highly Illegal, how about a true computer-controlled guidance system for a model rocket? A possible project would be to make a thing that would launch a model rocket as close to vertical as possible, countering any cross-winds present. Would one be imprisoned for a long time if it was discovered you were attempting such a feat? (1/2 :-) The "computer" part would probably be a snap, as would the actuators needed to control the model (would one control the thrust, or would standard model- airplane aileron stuff suffice?)... the real task would be to find sensors. Are there any gyros small enough? And what about the acelerometers? What other means can be used to sense attitude? -- Name: Matthew Francey Address: N43o34'13.5" W79o34'33.3" 86m mdf@ziebmef.mef.org uunet!{utgpu!moore,attcan!telly}!ziebmef!mdf ------------------------------ End of Space-tech Digest #36 *******************