Subject: Space-tech Digest #139 Contents: P2-E, Not-so-Big Dumb Booster (22 msgs) ------------------------------------------------------------ Date: Sun, 29 Nov 92 19:57:18 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Pressure-fed engines using LOX... I was thinking about Bruce's P2 over Thanksgiving. A real stumbling block here is the cost of peroxide. It comprises most of the propellant. We'd really rather use oxygen; LOX is at least an order of magnitude cheaper than peroxide (and less is required). LOX is cryogenic, but operating at lower pressure counters, to some extent, the amount of pressurizing gas required. The big problem was embrittlement of the tank. Conventional steels are apparently out. Hudson's Liberty, Bruce told us, used aluminum tanks at 250 psi. Bruce discarded aluminum because it would be too thick for a large launcher, and at his pressure. I don't see this as an insuperable problem; one could use more, smaller tanks, which would have thinner walls. Basically, a collection of pipes. One advantage of this approach would be that the individual tanks would be easier to transport, and so could be made at a factory. More complex plumbing would be required, however. Perhaps there is a way to store LOX in a steel tank. The idea here would be to put the LOX in a thin aluminum tank contained inside a steel tank. Both the aluminum and steel tanks are pressurized, by helium from the same source; a check valve could prevent the pressure in the internal tank from being less than that in the intertank area. The pressure difference between the tanks is kept small, perhaps a few bar, so the aluminum is thin; most of the absolute pressure of the fuel is confined by the steel tank. The external surface of the aluminum tank is covered with some sort of fine, open celled, porous material. If the thermal conductivity of this insulation is low compared to that of the steel tank (+ external boundary layer), the steel comes into equilibrium at close to ambient temperature, not at the temperature of the liquid oxygen. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Sun, 29 Nov 92 23:52 PST To: space-tech@cs.cmu.edu Subject: RE: Pressure-fed engines using LOX... From: Nick_Janow@mindlink.bc.ca (Nick Janow) > The external surface of the aluminum tank is covered with some sort of > fine, open celled, porous material. Is there an insulation available that could insulate the steel directly, without the use of the aluminum? Perhaps some sort of sprayed on ceramic foam? If a continuous inner layer of material is necessary, due to cracking of the insulation, then perhaps aluminum would be a suitable material, though there might be other more suitable materials. It would be nice to be able to weld the steel tank, spray in the ceramic (perhaps a room temperature water-based material, like foamed cement?), then spray a sealant that remains tough at LOX temperature. That would be a lot cheaper to produce than welding (and testing) a steel pressure tank over a coated aluminum pressure tank. -- Nick_Janow@mindlink.bc.ca ------------------------------ Date: Mon, 30 Nov 92 09:56:46 +0000 From: Dominic Herity Subject: Re: Pressure-fed engines using LOX... To: dietz@cs.rochester.edu Cc: space-tech@cs.cmu.edu X-Envelope-to: space-tech@cs.cmu.edu X-Mts: smtp > A real stumbling block here is the cost of peroxide. It comprises > most of the propellant. We'd really rather use oxygen; LOX is at > least an order of magnitude cheaper than peroxide (and less is > required). LOX is cryogenic, but operating at lower pressure > counters, to some extent, the amount of pressurizing gas required. > The big problem was embrittlement of the tank. Conventional steels > are apparently out. In present day rockets, its the hardware that costs, not the fuel. I remember working out that the cost of energy (approximately equal to the cost of fuel for a shuttle launch was under 1% of the total. An expendable has about the same order of magnitude in costs. So it seems misguided to me to trade hardware complexity for fuel cost. Any idea how much a P2-E will cost, or what the peroxide will cost? Even if it looks attractive on paper, I'd suggest sticking with the simpler hardware for a first attempt. Best Regards Dominic Herity ------------------------------ Date: Mon, 30 Nov 92 07:59:23 -0500 From: dietz@cs.rochester.edu To: dherity@cs.tcd.ie Subject: Re: Pressure-fed engines using LOX... Cc: space-tech@cs.cmu.edu Right, in present day rockets, hardware costs dominate. But this would not necessarily be the case with a real big dumb booster. Mass produced consumer goods, like cars or refrigerators, cost $3/pound or so. There is no reason why a rocket need be significantly more expensive than a car, per pound. Peroxide would run around $1/pound. At a mass ratio of 10, this means $9 of peroxide per pound of hardware. Another reason to use LOX is that there is much experience with this propellant, and many engines using it are available off the shelf. It would be nice to avoid having to design a new combustion chamber, with all its potential for instabilities. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ To: space-tech@cs.cmu.edu Subject: Re: Pressure-fed engines using LOX... Reply-To: jerbil@ames.arc.nasa.gov Date: Mon, 30 Nov 92 09:14:51 -0800 From: Joseph Beckenbach > Perhaps some sort of sprayed on ceramic foam? Just to throw out a few ideas for people to play with: 1) Aerogels might provide insulation and support at the same time. 2) Someone just patented a _paint-on_ ceramic. 3) We've still just scratched the surface on materials technology. Not sure any of these would be feasible for an on-the-cheap Big Dumb Booster, but who knows? Sandwich an insulating layer of aerogel (cast in place) between outer steel and inner aluminum walls, for example, or paint on an insulating zero-contraction ceramin directly onto the steel? Yours for better brainstorms (and stealth puns :-), Joseph Beckenbach jerbil@ultra.com 408-922-0600 x246 Speaking from, but not for, Ultra Network Technologies. ------------------------------ Date: Mon, 30 Nov 92 10:59 PST From: trost@cse.ogi.edu (Bill Trost) To: jerbil@ames.arc.nasa.gov Subject: Re: Pressure-fed engines using LOX... cc: space-tech@cs.cmu.edu jerbil@ames.arc.nasa.gov writes: Sandwich an insulating layer of aerogel (cast in place) between outer steel and inner aluminum walls...? Aerogels are rather difficult to make, requiring a delicate drying process to come out right. Your standard kitchen oven can't make them at all (it's hard to make xerogels in an oven), so that would be one *big*, complicated dryer to make an aerogel in a single steel tank. That, and you might end up melting the steel (I don't have the reference (my wife's undergrad thesis) handy). I've written about aerogels before, so you might check the digests (wherever that is...aargh) to see what I said before. Alternatively, there's the stuff made out of kelp that's lighter than aerogels and opaque that might be worth looking at -- it seems like the news blurbs said it's substantially easier to make than an aerogel (i.e., stir and set). I think it's called "sea foam." On a different note in this vein -- didn't the BDH switch to H2O2 as its oxidizer when the description of the P2 was first released to space-tech? It seems like made that switch because of the simpler handling. -- Bill Trost Space is nature's way of keeping everything from happening all in one spot. ------------------------------ To: space-tech@cs.cmu.edu Cc: gwh@lurnix.COM Subject: Re: Pressure-fed engines using LOX... Date: Mon, 30 Nov 92 10:01:49 -0800 From: gwh@lurnix.COM Actually, I'm getting better numbers on the Hydrogen Peroxide; it looks like we can keep the cost slightly under $0.90 per pound (small improvement 8-). The purification and storage are looking to be a lot more simple and painless than I was presuming. The discussions about internal insulation for LOX tanks asked if there was an internal insulation material that was spray-on. I haven't found one; you can buy sheets of LOX insulation material and can custom-manufacture it in formed shapes, but it's not inherently flexible, and I have doubts about its performance under high accelleration/vibration/slosh conditions. With a tank that will become brittle and likely fracture if the LOX comes into direct contact with the tank wall, an insulator has to be nigh-on perfect, leading to complex manufacturing and QA procedures, etc. ... sort of things that are verboten in the quest for absolutely minimal cost 8-) Problem of the week: moderately high performance (High Isp) orbital transfer vehicle (LEO->GEO; ~5 km/sec @ 5 ton payload) on the inexpensive side. Ideas? -george william herbert gwh@lurnix.com gwh@retro.com rsn. ------------------------------ Date: Mon, 30 Nov 92 22:31 PST To: space-tech@cs.cmu.edu Subject: RE: Pressure-fed engines using LOX... From: Nick_Janow@mindlink.bc.ca (Nick Janow) dietz@cs.rochester.edu (Paul Dietz) writes: > Note that the aluminum is not required to support a very large pressure (in > principle, it need only support the hydrostatic pressure of the LOX). If the insulation is strong enough (like foamed cement), it might only need a LOX-impermeable membrane to prevent the LOX from entering the insulation. A spray-on coating would be a lot cheaper than an aluminum pressure tank, even if it is just a thin-walled tank. The membrane could even allow oxygen to pass through, equalizing the pressure in the insulation, yet retaining enough insulation value to keep the steel warm. Nick_Janow@mindlink.bc.ca ------------------------------ Date: Mon, 30 Nov 92 22:31 PST To: space-tech@cs.cmu.edu Subject: RE: Pressure-fed engines using LOX... From: Nick_Janow@mindlink.bc.ca (Nick Janow) While peroxide does sound simpler to handle, LOX could provide simplifications in other ways. The peroxide tank can't be pressurized with hot gas due to its instability. Could the LOX tank be pressurized by spraying in propane, perhaps with a catalytic mesh or a spark igniter to reduce the possibility of explosive mixtures? Perhaps the propane tank could be pressurized in a similar fashion (spray LOX in, with a "guaranteed ignition" system). The cost of the oxidizer may not be a valid argument for LOX, since if the peroxide booster became popular, a facility for manufacturing peroxide cheaply might be built (or expanded). Nick_Janow@mindlink.bc.ca ------------------------------ To: Nick Janow Cc: space-tech@CS.CMU.EDU, gwh@soda.berkeley.edu Subject: Re: Pressure-fed engines using LOX... Date: Mon, 30 Nov 92 23:06:54 -0800 From: George William Herbert The problem with foamed cement is that it's very seriously fracture prone and it's stress/strain behaviour is not compatable with High Strength Steel. I.e. when you pressurize things and depressurize them again, you get some cracks. I'm leery of such behaviour. I don't know offhand of other pressure-resistant insulators, though a scheme for inertly pressurizing a insulation layer could bear fruit. -george william herbert gwh@lurnix.com gwh@soda.berkeley.edu gwh@retro.com (use netcom!retro!gwh for now) up and running by Wed. nite or bust ------------------------------ To: space-tech@CS.CMU.EDU Cc: gwh@soda.berkeley.edu Subject: Big Dumb Booster evolves some more... Date: Tue, 01 Dec 92 22:34:39 -0800 From: George William Herbert New Directions The following three sections describe some recent work on the Big Dumb Hybrid Booster and a precursor vehicle. As always, I would like to thank the members of this mailing list for input in previous versions and again on this one. Oxidizer Choices The first oxidizer considered for the BDH project was LOX, due to its superior performance. When it led to materials problems, and at the prompting of Bruce Dunn (whose P2 concept was announced at about that time), I changed over to Hydrogen Peroxide. At that time I did preliminary analysis of other storable oxidizers, which indicated that H2O2 was the highest performance alternative. More recently Paul Dietz told me to look at Nitric Acid, which I'd done (and rejected) earlier. After his message, I did it again, and it appears I blew my earlier analysis. Instead of a 6-9% lower Isp for Nitric Acid compared to Peroxide, it is closer to 1-2%. Which, after a second look, is nicely offset by its higher density (1.50 vs. 1.41). I did an extensive set of calculations earlier today and think that a 600 PSI chamber pressure RFNA (Red Fuming Nitric Acid) and metalized plastic fuel rocket will have performance of Isp 265 at sea level to 285 in vaccum, after allowances for ineffeciency (0.92) in real performance. This is very positive and given the price differential between Peroxide and RFNA points towards the latter as being a superior Big Dumb propellant. RFNA is about 5 times cheaper than Peroxide (I'm going to withhold a precise estimate until I have a chance to pry prices out of some chemical companies for large bulk buys; not doubting your numbers, Paul 8-) ). The Bipropellant Solid Engine concept The one thing that had always worried me about the Big Dumb Hybrid was the need to pressurize the oxidizer and thence feed it into the chamber with the fuel. Solid engines get around this problem by simply putting the oxidizer and fuel in one mixture. It would be slightly safer to put them in two very close by mixtures, but the mechanical properties of solid oxidizers make that impractical; you have to use small particles in a matrix of something else anyway. Why not just mix them? Well, applying this concept to the BDH and looking at the oxidizers being considered, I noted that Hydrogen Peroxide freezes at less than 1 degree below zero. This would allow a frozen oxidizer to be in the same pressure container as the fuel, probably with the fuel mixed in with the oxidizer before freezing or with a "layer-cake" stack of layers of oxidizer and fuel (my current preference). Other arrangements are possible, but it's hard to beat a layer cake approach with order of inches thick (vs. 0.5 to several meters diameter) layers for overall homogenity of mixture and burn rate. The dangers of cracking and delamination present in normal solids don't exist in a bipropellant solid; since each component is physically seperated from (though close to) the other one, it will behave like the solid fuel in a hybrid, regressing normal to the flow of gas over its surface, not along all surfaces such as a solid will. This maintains the safety aspect of a hybrid in combustion, though it can't be turned off like a liquid/solid hybrid can be. I feel the loss of that feature is of very little significance in the whole scheme of things. When I decided to switch to RFNA, some changes were in order: it freezes at -42C, much colder than peroxide does. However, fortunately for me, the steel I much prefer working with (T-1) remains ductile down to about -110C, so we can even significantly supercool the RFNA ice without risking the steel's properties. The one disadvantage of this is that the motor will perform equivalently to a solid engine, and can't be throttled by venting something from (for instance) the oxidizer tank as the earlier BDH design did for directional control. I started out using paddles in the nozzle for this, I can accept going back to that method. The Not-So-Big-Dumb-Booster The most significant problem with actually going forth with the BDH project has always been getting the money together to develop it right. I had in mind doing a smaller demonstrator or a sounding rocket to prove the technology. Earlier today, I ground through a full design on one. Meet the SDB (Small Dumb Booster). The SDB is designed to launch a payload of 20 kilograms to low earth orbit. The vehicle's gross weight is about 5 metric tons; it's a three stage vehicle, and it stands seven meters high. The first stage is a cluster of six 0.5 meter diameter and 4 meter long engine units. The second is one more of these units (the seven forming a hexagonal array). Stacked on top of the second stage unit is a much smaller third stage and a 0.5 meter diameter, 1.5 meter long fairing for the payload. The motors are of the stacked-layer bipropellant solid type discussed above, RFNA and magnesium in a plastic base for fuel. It operates at a chamber pressure of 600 PSI, which further analysis shows still is by far the optimal pressure for a engine of this nature. The tanks (and all other primary structures) are welded from T-1 steel (100 ksi yield). The specified limit load condition is 0.75 of yield load, giving a factor of safety of 1.33 and an ultimate factor of safety of 1.6 . Again, analysis indicates that primary loads are from tank pressurization, which are easy to calculate and engineer for. Other loadings are minimal compared to these primary loads and for the most part do not occur in the same directions as the pressurization load maximums. The design currently has mass margins of 8%. An increase in those margins to 14% (increasing mass at all stages by 10% and following through on lower stage increases that result from heavier upper stages) leaves the vehicle at a mass of under 8 tons, so if I've royally blown some design calculations it still comes out with a reasonable size. Pricing the vehicle indicates fuel costs will be below $2750, the steel and primary fabrication about $1200, other hardware (guidance and directional control) about $5000, and setup and miscelaneous labor brings the total cost to about $11,980. Since nobody would bother believing that's how little it will cost, I'll double it before adding in a reasonable profit of 50% for a final vehicle cost to the commercial customer of $36,000. This is a price of about $800 per pound, about 1/3 to 1/4 of standard commercial launcher costs and 1/10 to 1/20 of the cost per pound of a Pegasus or Scout light launcher. And that's without scale-up effects. Anyone want to help ante up for engine tests and the first demo launch? We're looking at a $25-50,000 campaign if some labor is donated, including development tests and the first flight vehicle. My donated labor is a lot of it (I'm talking my father into adding welding gear to his shop now, which takes care of most of the problem), but I can't foot it all 8-) at least not soon. -george william herbert gwh@lurnix.com gwh@soda.berkeley.edu gwh@retro.com [hardware at T-2 days and software real soon thereafter 8-)] This email message and its contents are copyright (c) 1992 by George William Herbert and Retro Aerospace. Commercial use prohibited without prior approval. Have a nice day 8-) ------------------------------ Date: Wed, 2 Dec 92 07:35:51 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: price of nitric acid... A bit of a correction... I was quoting a (1980) price of 95% nitric acid as being about 5 times cheaper per pound than hydrogen peroxide. RFNA could be a bit more expensive (although it can be made on-site from conc. nitric acid, the NO2 being made chemically by reacting some of the acid with a metal, for example). I don't know what's happened to the price of nitric acid since then. Nitric acid is made from ammonia, which is made from natural gas, and gas prices are lower now than in 1980 (adjusted for inflation). On the other hand, air pollution controls may have driven the price up. Be aware that nitric acid requires special tank materials. The hybrid bipropellant idea sounds pretty risky, but if you must, consider nitrogen tetroxide as the oxidizer. It freezes at -12 C. Paul ------------------------------ Date: Wed, 02 Dec 92 16:28:24 +0000 From: Dominic Herity Subject: Re: Big Dumb Booster evolves some more... To: George William Herbert Cc: space-tech@CS.CMU.edu, dherity@cs.tcd.ie X-Envelope-to: space-tech@CS.CMU.edu X-Mts: smtp > Anyone want to help ante up for engine tests and the > first demo launch? We're looking at a $25-50,000 campaign What about sponsorship? You could get a lot more than that from sponsors to paint their logo on the side. ================================================================================ | Dominic Herity, dherity@.cs.tcd.ie, | Something clever | | Computer Science Dept, Trinity College, Dublin 2, Ireland.| coming soon to a | | Tel : +353-1-6772941 ext 1720 Fax : +353-1-6772204 |signature near you| ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 2 Dec 92 14:35:30 EST To: space-tech@cs.cmu.edu Subject: RE: Pressure-fed engines using LOX... >... Could the LOX tank be pressurized by >spraying in propane, perhaps with a catalytic mesh or a spark igniter to >reduce the possibility of explosive mixtures? Perhaps the propane tank could >be pressurized in a similar fashion (spray LOX in, with a "guaranteed >ignition" system). Such things have been done for hypergolics, I think, but the thought of doing it for non-hypergolics makes me cringe... Maybe with some sort of catalytic burner at the gas entry point, to ensure complete and immediate combustion... Hmm. You could presumably pressurize a tank by injecting a small flow of something that *is* hypergolic with the propellant, even if your main mix is not hypergolic. I wonder how this would look as far as weight goes. It probably would mean handling some fairly nasty substances. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ To: dietz@cs.rochester.edu Cc: space-tech@cs.cmu.edu, gwh@soda.berkeley.edu Subject: Re: price of nitric acid... Date: Wed, 02 Dec 92 11:34:26 -0800 From: George William Herbert I've looked into the cost of manufacturing RFNA from Nitric Acid; it's pretty minor. I refuse to consider using nitrogen tetroxide. I will probably have to build and test the engines myself, and nitrogen tetroxide is _bad_. People still get hurt regularly working with it (about 1 a year at last report) after having imposed the best and strictest safety guidelines possible... Admittedly, you can't entirely avoid it (any spacecraft with thrusters carries it), but I can do without it for the boosters. Besides, the difference between -12 C and -46 C isn't all that much; it's within "real cold" instead of "cryogenic" handling precautions, the other materials involved aren't adversely affected either way, it's got about half the density of nitric acid (which leads to a much bigger tank etc) and is a whole lot more expensive. And I'd have to get EPA and OSHA people's approval right and left. RFNA requires tanks that are acid-safe; nearly any plastic will do. I can spray it on to the inside of the steel walls. The fuel, which is magnesium in a plastic binder, can easily be coated in another layer of plastic to keep the magnesium from contacting the acid (someone else mailed me about that), which I had in mind but didn't specifically note in the article. And finally... someone suggested getting a corporate sponsor to raise money for the launch. Not a bad idea... 8-) side matter: Let me clarify what Retro Aerospace is just so everyone knows (someone asked about it). Retro Aerospace is a startup, currently with three part time employees working on an equity basis (ie for free but have a chunk of the business): myself, my wife, and a friend who's out at CU Boulder working on a Masters right now and out of the loop on this project, though he's been working on it a little before. Until I get some engine tests done (small scale, to verify combustion stability, safety, regression rates, etc. on the fuel/ox. mixture of choice) I'm not really looking for investors, though anyone willng to donate to help buy some equipment for the tests is gladly welcomed... Once I'm sure the engines will work acceptably, I'll want to fly a test rocket or two, at which point I will start looking for serious money. The orbital launch of the mini rocket would come a bit later. Timescale on this? I don't know. I'm employed full time doing something else, and doing this and a couple of other projects on the side, so it's going slowly at this point. I would hope to get the engine testing done before summer 1993, but a firmer schedule is hard to predict. Thanks again for the input and comments recieved 8-) -george william herbert ------------------------------ Date: Wed, 2 Dec 92 23:28:39 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: various things... Some comments on George's ideas... N2O4 is nasty, but RFNA is also nasty. The red fumes are NO2, which is lethal if you breathe it at 200 ppm (delayed pulmonary edema). N2O4 and NO2 are in equilibrium with each other, with a significant amount of the tetroxide being dissociated into the monomers at STP. Perhaps he should stick with ordinary concentrated nitric acid, w. no fumes. The density of N2O4 is not 1/2 that of nitric acid. N2O4 has a density of 1.44 g/cc at room temperature. George suggested a mix of coated magnesium disks and frozen nitric acid. May I suggest aluminum disks? High purity aluminum (99.8%) is used in some nitric acid plants, although the usual alloy is high-chromium steel. Unlike magnesium, the aluminum would resist corrosion by formation of an oxide layer. Paul ------------------------------ Date: Wed, 2 Dec 92 23:51:36 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: where is this program I discovered that CECTRP, the successor to the Gordon/McBride program I was looking for, is available from COSMIC. For $700. Plus $64 for documentation. Ouch. Paul ------------------------------ Date: Wed, 2 Dec 92 23:44:06 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Big Dumb Nozzles Bruce's booster uses the SRM nozzle. This is steerable, but is complex. It would be better to have a cheaper, dumber nozzle. I suggest a fixed nozzle with steering via fluid injection. The fixed nozzle can just be welded or bolted to the combustion chamber. Interestingly, hydrogen peroxide is a good injectant, with a side specific impulse (according to Sutton) of 434 sec. Nitrogen tetroxide is better: 478 sec. Out of curiosity: how is P2-E going to achieve roll control when operating with only a single nozzle? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Thu, 3 Dec 92 08:09:49 EST From: clarke@next1.acme.ucf.edu (Thomas Clarke) To: space-tech@cs.cmu.edu Subject: Readable Book About Rocket Fuels I recommend the book: _Ignition! An informal history of liquid rocket propellants._ by John Clark (1972, Rutgers Univ Press) It discusses the history of same beginning with Tsiolokovsky (sp?) and Dewar right up to the 60's. Much about the foibles of nitric acid - it was tamed when adding .6% HF to it was discovered to passivate steel and aluminum tanks. Also exotics like FClO3 which apparently is fairly safe to handle. Curiosities: under right conditions Teflon will burn with water CFF2n + H2O -> CO and 2HF exothermically - weired hybrid? Style is informal - one chapter title is "Peroxide, Always a Bridesmaid" A good read. Thomas Clarke Institute for Simulation and Training, University of Central FL 12424 Research Parkway, Suite 300, Orlando, FL 32826 (407)658-5030, FAX: (407)658-5059, clarke@acme.ucf.edu ------------------------------ Date: Thu, 3 Dec 92 07:03 PST To: space-tech@cs.cmu.edu Subject: Nitric acid From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) George William Herbert writes: > I've looked into the cost of manufacturing RFNA from Nitric Acid; > it's pretty minor. I refuse to consider using nitrogen tetroxide. > I will probably have to build and test the engines myself, and > nitrogen tetroxide is _bad_. People still get hurt regularly > working with it (about 1 a year at last report) after having > imposed the best and strictest safety guidelines possible... I am caught without any reference works handy, but I thought that the "Red Fuming" in Red Fuming Nitric Acid was NO2 (of which N2O4 is merely a dimer). Granted, it is dissolved in something else, but since it is "fuming" you have not eliminate the toxicity, which comes from the NO2 gas and not the N2O4 itself (corrections of course accepted if I am mis-remembering). Even "ordinary" nitric acid, which I use in the lab, is very nasty stuff. > RFNA requires tanks that are acid-safe; nearly any plastic will do. Not necessary. The "I" in IRFNA, the standard rocket oxidizer, stands for "inhibited" and refers to the addition of a trace of hydrofluoric acid. This reacts with steel to form a fluoride coating which protects the material from corroding. It was the development of IRFNA from RFNA which made RFNA a practical oxidizer by allowing it to be stored in steel or aluminum tanks. -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ Date: Thu, 3 Dec 92 07:21 PST To: space-tech@cs.cmu.edu Subject: Big Dumb Nozzles From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) Paul Dietz writes: > > Bruce's booster uses the SRM nozzle. This is steerable, but > is complex. It would be better to have a cheaper, dumber nozzle. > > I suggest a fixed nozzle with steering via fluid injection. The fixed > nozzle can just be welded or bolted to the combustion chamber. > Interestingly, hydrogen peroxide is a good injectant, with a side > specific impulse (according to Sutton) of 434 sec. Nitrogen tetroxide > is better: 478 sec. > > Out of curiosity: how is P2-E going to achieve roll control when > operating with only a single nozzle. A very good idea, which nearly made it into my writeup. This method is used on the Titan SRB. A separate tank contains N2O4, which is injected into the nozzle through an array of 24 valves. A similar system would work very nicely for the P2-E as high pressure peroxide is already available for the price of a bit of plumbing. If designing a vehicle from scratch, I think that fluid injection is what I would propose. The SRB nozzle on the other hand has the advantage that it already exists. It would have to be lengthened, but this is probably a much less critical problem than the design and construction of the throat on a new nozzle. The lower half of the SRB nozzle is any any case a replaceable item. There is a linear charge which blow off the bottom of the nozzle before landing, in order to reduce the side force which is applied to the expensive part when the nozzle hits the water. The thrust vector control system of the SRB is not all that complicated. It has two hydraulic actuators, a bit of plumbing, and two small APUs. To my knowledge, it has never caused any trouble on the SRB. Buried in my writeup somewhere is a line which indicates that when only one P2-E nozzle is working (core stage), roll control will be by mono-propellant peroxide thrusters. This makes use of the high pressure peroxide available - the Centaur attitude control was originally by peroxide thruster, although it has now been changed to hydrazine. -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ Date: Thu, 3 Dec 92 09:42:57 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: Big Dumb Nozzles Roll control: oh, I see Bruce mentioned this. Never mind. Paul ------------------------------ End of Space-tech Digest #139 *******************