Carbide/peroxide rockets?

[blackshire]

Hello All,

Just as the R/C model jet airplane enthusiasts had long wanted true turbojet engines to power their models (and finally got them), I have long desired a liquid or gaseous bipropellant rocket engine for hobbyist use, especially in scale models of liquid propellant rockets and missiles.

Calcium carbide (see: http://en.wikipedia.org/wiki/Calcium_carbide ) might make such an engine possible. When moistened with water, calcium carbide generates acetylene gas, and this acetylene gas source has been used in carbide lamps and toy cannons for many years.

In a model rocket, calcium carbide could be used to generate the acetylene fuel, while the oxidizer could be ordinary dilute "drug store" hydrogen peroxide, whose solution is mostly water. It could be decomposed into gaseous oxygen and steam by passing it through a catalyst screen inside the rocket engine. This propellant combination would be relatively "anemic" in terms of specific impulse, which--like the relatively low-ISP black powder used in solid propellant model rocket motors--would make such a liquid/gaseous propellant rocket engine safer to handle and operate.

The engine's power cycle could be arranged in either of two ways:

[1] The water to react with the calcium carbide (to generate acetylene gas) could be stored in a tank aboard the rocket. Before launch, an electrically-operated or mechanically-operated check valve would be opened, allowing water to flow into the calcium carbide compartment via gravity feed. The generated acetylene gas would pressurize the fuel side of the plumbing, opening a pressure-calibrated check valve that would allow it to flow into the engine's injector.

On the oxidizer side, a similar electrically-operated or mechanically-operated initial check valve would allow the hydrogen peroxide/water solution to flow down to the catalyst screen, where it would decompose into oxygen gas and steam. The pressurized, oxygen-charged steam would open a second pressure-calibrated check valve that would allow it to flow into the engine's injector. A pyrotechnic igniter or a spark igniter would ignite the acetylene/oxygen mixture.

[2] Instead of carrying water in a separate tank inside the rocket (to generate the acetylene), some of the steam from the catalyst-induced decomposition of the hydrogen peroxide would be tapped off to flow into the calcium carbide compartment. Because this steam would contain oxygen gas, the rocket engine would be laid out in such a way that ignition and combustion of the acetylene/oxygen mixture would take place in or very close to the calcium carbide compartment.

In either case, the rocket engine's exhaust would consist of mostly steam, along with the products of the acetylene/oxygen combustion (more steam, carbon dioxide, and some unburned acetylene that would burn with the oxygen in the air after it exited the rocket engine's nozzle). The fuel-rich reducing environment inside the hot parts of the engine would reduce the problems with corrosion that would be present in an oxidizer-rich oxidizing environment inside the engine.

The rocket engine itself could be radiatively cooled due to its short operating duration on each flight, although larger versions of the "Type 1 Engine" could use part of the water to circulate through a nozzle & combustion chamber cooling jacket before being boiled into steam and ejected with the exhaust. (This cooling system "waste" steam could also be used for TVC [Thrust Vector Control] via either secondary injection into the engine's nozzle or by being vented overboard through smaller movable nozzles.)

I hope this information will stimulate further discussion.

[blackshire]

Also, this liquid/gaseous propellant model rocket engine could be used to simulate the exhaust flame appearances of various full-scale missiles and rockets by varying the fuel/oxidizer (acetylene/oxygen) mixture ratio.

For powering scale models of missiles such as the Lance and Titan II that had "invisible" exhaust plumes, a "leaner" (less fuel) mixture ratio would be used. For scale models of rockets that had yellowish exhaust plumes (Aerobee sustainers, Black Knight, etc.), a "richer" (more fuel) mixture ratio would be used.

[Joe Wooten]

Gasoline Model Rocket engine (http://home.total.net/~launch/)

[ghrocketman]

Good luck obtaining 50% H2O2 (Hydrogen Peroxide) in any sort of "easily obtainable" manner since 9/11 in the US.
At the very least you will have to sign for it and it most likely will put you on some sort of watch list no matter your appearance.

[luke strawwalker]

One problem instantly jumps out at me... you'll need "high test" peroxide to get this to work-- "drugstore" peroxide will decompose, but it does it so slowly as to not generate a lot of exothermic heat or oxygen... obviously it decomposes when you pour it on a wound and it 'fizzes' (releasing oxygen which kills pathogens) but the reaction is VERY low intensity, obviously...

Not sure how fast carbide will decompose into acetylene. Those acetylene lamps were before my time-- I've seen them but never operated one. Additionally, getting calcium carbide isn't especially easy to do, and I'm pretty sure you'd probably have hoops to jump through to get, keep, or store the stuff... I've seen HD blowtorch setups from the 50's and 60's that used carbide/water pots to generate acetylene for torches used in shipbuilding and railroad use, where the torch ran pretty much all day every day, but I haven't seen anything like that in DECADES... AFAIK, ALL the acetylene torches in use today by welders are using balsa/acetone/dissolved acetylene high pressure cylinders-- I know that's all we've ever used on the farm and at all the different plants and stuff I've worked at... and all I've ever seen at the welding supply shops I sometimes haunt... I've NEVER seen parts for carbide/water acetylene generators, or powdered calcium carbide to fuel them....

Seems to me the valving, ignition, and control of the engine would be pretty problematical. Such a beast would be VERY expensive to make, buy, build, maintain, and operate. Just as hybrid engines are very expensive, mostly because of the GSE, a true liquid propellant engine would be even MORE difficult and expensive! Basically a hybrid is, at it's heart, a cross between an old Vashon "cold power" rocket and an APCP motor, boiling off and feeding the oxidizer nitrous oxide through an injector into the solid fuel grain and combusting with it once ignited. I'm thinking for a typical "LPR/HPR" engine burn time operating over a period of a few seconds at most, you'd have to liberate a LOT of acetylene at pretty high pressure (around a hundred PSI at least?-- Don't Estes motors operate at 70 PSI casing pressure at least??) to inject it into the combustion chamber, and mix it with the correct ratio of oxidizer (obviously through a calibrated nozzle, but the volume delivered through a nozzle is directly related to the square of the pressure forcing the fluid through the nozzle-- IE, to double the rate of flow through a given injector nozzle size, you have to increase the pressure FOUR TIMES-- so this means that your mixture will vary with the injection pressure behind it-- that's why fuel injectors in cars are supplied with fuel at a constant pressure from the fuel pump and pressure regulator-- inaccurate rail pressure means that the fuel delivery will be off from that calculated by the computer controlling the injector pulse width). The "gravity flow" thing is a non-starter for this reason, because as soon as the pressure starts to rise in the gas generator, it will stop the flow of water into the carbide chamber. Unless of course you tap off the pressure from the carbide chamber through an equalization line to pressurize the head end of the water supply tank-- but then at any rate, the volumes of the tanks come into play since they'll act as a system pressure accumulator and slow the pressure buildup in the system, effectively taking a LOT longer to build up pressure inside the combustion chamber...

Hybrid engines are MUCH simpler because, like cold propellant, the liquid nitrous is self-pressurizing and contained in a "relatively high pressure" container to start with, or a tank that self-pressurizes at ambient temperatures. Water doesn't do this. Carbide generating gas WILL create pressure inside a sealed container, (they did a little 'rocket experiment' at NASA in Huntsville, AL, using a small 'rocket' made out of a tube with a stopper into which baking soda and vinegar were added and rapidly capped tightly, and inverted in a 'launching tube' which pressurized with CO2 and then popped it's cork sending the 'rocket' flying... BUT the rate of production of the acetylene and it's pressure will be critical to the design of such a system and would have to be VERY carefully calibrated and constructed, if it's even possible at all...

I think that, if one were just completely in love with the idea of a liquid propellant hobby motor, that the best bet would be a simple pressure-fed design, using some form of liquid fuel combined with a simple, readily available oxidizer, which means nitrous oxide, IMHO... I could see a relatively simple engine being possible, using a small nitrous tank and a small fuel tank, using the nitrous to self-pressurize for injection into the combustion chamber, and the fuel housed in a seperate tank, pressurized by a small CO2 cartridge like those used in air rifles or paintball guns... the "ignition" would coincide with a device which would simultaneously pierce the C02 cartridge to pressurize the fuel tank, and pierce either a small nitrous oxide canister or a seal disk in the oxidizer line coming from the larger nitrous tank or otherwise open the nitrous supply to the combustion chamber, heck, use the same methods the larger hybrid motors use to start the flow of nitrous to the motor! The CO2 would pressurize the fuel tank, which would then begin injecting the fuel into the combustion chamber, simultaneously with the nitrous oxidizer being injected into the combustion chamber, in the presence of a constant ignition source, which would then ignite the mixture, the rocket would then take off, and fly until the fuel and oxidizer tanks were empty, venting the residual CO2 and nitrous ullage pressures overboard through the injection nozzles in the combustion chamber rendering the motor inert at the end of it's burn.

Obviously ejection would have to be handled by dual deploy setups or an altimeter or electronic timer operating some sort of secondary propellant or ejection mechanism (spring loaded, BP??)

Prepping for the next flight would require either installing a new nitrous oxide cartridge or inserting a new burst disk, or resetting the nitrous valve, installing a new CO2 cartridge for fuel pressurant, refilling the fuel and oxidizer tanks (if it's a larger motor using a larger nitrous tank than the small nitrous cartridges) and resetting the "valve disk piercing mechanism" and ignitor on the GSE, much as with a hybrid launch.

That's how I'd go about it, anyway... :)

later! OL JR :)

[blackshire]

I very much appreciate all of your replies! The calcium carbide fuel "precursor" material is readily available from Big-Bang Cannons (see: http://www.bigbangcannons.com/ ), who sell it in toothpaste-type tubes under the name "Bangsite." I used to have one of their cannons, which had a Bangsite measuring spoon cast as part of the removable breech cover. Just a ~4 mm wide hemispherical "spoon scoop" of Bangsite generated enough acetylene gas to produce a blast like that from two or three firecrackers going off at once, with a ~6" tongue of flame shooting from the cannon's barrel.

Used in a rocket, all of the Bangsite could be reacted with water before launch to fill the fuel tank with pressurized acetylene gas. The water addition could be triggered remotely (either electrically or mechanically) for safety. On the oxidizer side, "drug store" strength hydrogen peroxide (*not* 50%) could all be decomposed before launch into steam and gaseous oxygen. The H2O2 decomposition could be triggered (again remotely) by allowing it to come into contact with a suitable catalyst, such as manganese dioxide (http://en.wikipedia.org/wiki/Manganese_dioxide ).

After both of these reactions, the rocket's propellant tanks would contain acetylene gas (fuel) and a steam/oxygen mixture (oxidizer), both under pressure. (Depending on the pressure developed inside the oxidizer tank, it might contain a mixture of liquid water and oxygen gas rather than steam and oxygen gas.) This would eliminate the need for a separate pressurizing agent (either a tank of high-pressure inert gas or a pyrotechnic gas generator cartridge.) To launch the rocket, the tank valves to the engine would be opened remotely and the igniter would be fired.

[luke strawwalker]

I very much appreciate all of your replies! The calcium carbide fuel "precursor" material is readily available from Big-Bang Cannons (see: http://www.bigbangcannons.com/ ), who sell it in toothpaste-type tubes under the name "Bangsite." I used to have one of their cannons, which had a Bangsite measuring spoon cast as part of the removable breech cover. Just a ~4 mm wide hemispherical "spoon scoop" of Bangsite generated enough acetylene gas to produce a blast like that from two or three firecrackers going off at once, with a ~6" tongue of flame shooting from the cannon's barrel.

Used in a rocket, all of the Bangsite could be reacted with water before launch to fill the fuel tank with pressurized acetylene gas. The water addition could be triggered remotely (either electrically or mechanically) for safety. On the oxidizer side, "drug store" strength hydrogen peroxide (*not* 50%) could all be decomposed before launch into steam and gaseous oxygen. The H2O2 decomposition could be triggered (again remotely) by allowing it to come into contact with a suitable catalyst, such as manganese dioxide (http://en.wikipedia.org/wiki/Manganese_dioxide ).

After both of these reactions, the rocket's propellant tanks would contain acetylene gas (fuel) and a steam/oxygen mixture (oxidizer), both under pressure. (Depending on the pressure developed inside the oxidizer tank, it might contain a mixture of liquid water and oxygen gas rather than steam and oxygen gas.) This would eliminate the need for a separate pressurizing agent (either a tank of high-pressure inert gas or a pyrotechnic gas generator cartridge.) To launch the rocket, the tank valves to the engine would be opened remotely and the igniter would be fired.


One problem-- acetylene gets VERY TOUCHY as a gas when stored at pressures above 15 PSI... that's why high pressure acetylene cylinders are filled with balsa wood and acetone-- the balsa wood absorbs the acetone to keep the liquid from coming out of the tank, and the acetone absorbs the acetylene which dissolves in it, and bubbles out of solution as the ullage pressure is drawn off the tank by the regulator feeding the torch.

I'd like to see an experiment that shows common brown-bottle medicine cabinet H202 decomposing fast enough with ANY catalyst to produce STEAM...
I thought only high-concentration H202 could do that...

Later! OL JR :)

[blackshire]

One problem-- acetylene gets VERY TOUCHY as a gas when stored at pressures above 15 PSI... that's why high pressure acetylene cylinders are filled with balsa wood and acetone-- the balsa wood absorbs the acetone to keep the liquid from coming out of the tank, and the acetone absorbs the acetylene which dissolves in it, and bubbles out of solution as the ullage pressure is drawn off the tank by the regulator feeding the torch.Thank you, Luke. This is why I posted this idea as a discussion-starter--to identify problem areas. The criteria for this hypothetical liquid (or gaseous) propellant hobbyist rocket are that its fuel and oxidizer must be readily-available, non-corrosive, non-toxic, non-hypergolic, and not subject to self-detonation.

Since the acetylene molecule has (if I remember my hydrocarbon chemistry) a triple carbon bond, pressurizing the gas beyond 15 PSI must tend to break that bond (without the presence of acetone for the acetylene gas to dissolve in) and cause the acetylene molecules to decompose, with the release of the bonding energy as heat. (Yep, that's what the Wikipedia article on acetylene says--it's subject to explosive decomposition if pressurized.)

Acetone itself might make a good low-ISP liquid rocket fuel. Isopropyl alcohol (rubbing alcohol) and denatured alcohol ("methylated spirits"--ethyl alcohol containing 10% methyl alcohol to make it undrinkable and not subject to liquor taxes) would also make good readily-available liquid rocket fuels, although their ISPs would be on the high side for hobbyist use. Propane or butane in cartridges could also be used as fuels, and since the cartridges are pressurized, the fuel would force itself into the engine. The oxidizer could be pressurized gaseous oxygen (which I *think* I saw in small CO2-type cartridges for hand-held oxy-butane torches) or nitrous oxide. Or possibly...

I'd like to see an experiment that shows common brown-bottle medicine cabinet H202 decomposing fast enough with ANY catalyst to produce STEAM...
I thought only high-concentration H202 could do that....If "drug store" hydrogen peroxide is this "exothermically tame" when it decomposes, this could make it useful for the rocket. It could all be decomposed in the rocket's oxidizer tank by exposure to a catalyst, and the released, self-pressurized gaseous oxygen "head" above the leftover water in the tank would be injected into the engine to burn the fuel. The water could serve as engine coolant, which would boil and be ejected with the exhaust. Also, some of this steam could be tapped off and used to pressurize both the oxidizer and fuel tanks (if pressurized butane or propane cartridges weren't used as fuel tanks).

[rstaff3]

From everything I've read, consumer grade peroxide has to be pre-processed to get higher concentrations before it has any use as a rocket oxidizer. Last person I heard about doing this (except for maybe the RRS guys who have better facilities than the average bear) blew up their garage. I forget whether they were in it at the time.

PS - I love my Big Bang cannon.

[blackshire]

From everything I've read, consumer grade peroxide has to be pre-processed to get higher concentrations before it has any use as a rocket oxidizer. Last person I heard about doing this (except for maybe the RRS guys who have better facilities than the average bear) blew up their garage. I forget whether they were in it at the time.For this engine, that was never my plan (using the hydrogen peroxide as an oxidizer); rather, the peroxide would be the source from which gaseous oxygen would be liberated (in keeping with the criteria that for hobbyist use of this engine, the oxidizer and fuel must be readily-available, non-corrosive, non-toxic, non-hypergolic, and not subject to self-detonation).PS - I love my Big Bang cannon.I may buy another one--they have more designs than I thought!

[rstaff3]

For this engine, that was never my plan (using the hydrogen peroxide as an oxidizer); rather, the peroxide would be the source from which gaseous oxygen would be liberated (in keeping with the criteria that for hobbyist use of this engine, the oxidizer and fuel must be readily-available, non-corrosive, non-toxic, non-hypergolic, and not subject to self-detonation).I may buy another one--they have more designs than I thought!

I'm not convinced that you can effectively decompose the peroxide when it's that diluted, but then I don't even play a chemist on TV.

Conestoga had a bunch of cannon models back in the day and have added some. Mine is a very basic model. Man, they are too expensive for me now. Adding a cannon would eliminate some amount of rockets and motors. Plus the Peeples Republik of Maryland doesn't like things that go boom, even if legal. So, I only shoot mine a couple of times a year in the dark. (In the dark only because of that flame that was previously mentioned :D )

http://rocketdungeon.blogspot.com/2006/01/how-i-rang-in-new-year.html

[blackshire]

I'm not convinced that you can effectively decompose the peroxide when it's that diluted, but then I don't even play a chemist on TV.In my experience, "drug store strength" H2O2 fizzes (decomposing and releasing its "extra" oxygen atoms) very nicely on cuts, and even when I've accidentally spilled it on surfaces I've touched that have skin oil on them. Using a good metal-based catalyst such as manganese dioxide should work even better.Conestoga had a bunch of cannon models back in the day and have added some. Mine is a very basic model. Man, they are too expensive for me now. Adding a cannon would eliminate some amount of rockets and motors. Plus the Peeples Republik of Maryland doesn't like things that go boom, even if legal. So, I only shoot mine a couple of times a year in the dark. (In the dark only because of that flame that was previously mentioned :D )

http://rocketdungeon.blogspot.com/2006/01/how-i-rang-in-new-year.htmlMaryland is one of those states (California is another) that I wouldn't live in on a bet, precisely due to restrictions like that (which go far beyond the mere "outlawing of fun"). In contrast, one of my physical therapists just returned to Fairbanks a couple of weeks ago after a trip to visit family in Duluth, Minnesota. He took (and brought back) his .44 caliber *gunpowder* cannon on the plane in checked baggage (with no black powder or green cannon fuse, of course), and none of the TSA or airline personnel at either airport freaked out when he informed them about the cannon--the most common reaction was: "Neat!" He also fired it several times while he was there, and no one called the police on him.

[rstaff3]

The only way you'll convince me is to build one :D I dare ya'. I bet MDRA will let you fire it. :chuckle:

[blackshire]

The only way you'll convince me is to build one :D I dare ya'. I bet MDRA will let you fire it. :chuckle:I'm afraid producing the hardware will be up to others (I've no room [or money] for a metal-working shop in my apartment)--I just figured I'd put the idea out there. Who knows, maybe John Carmack will come up with something similar to help fund his suborbital spacecraft development project?

[luke strawwalker]

Thank you, Luke. This is why I posted this idea as a discussion-starter--to identify problem areas. The criteria for this hypothetical liquid (or gaseous) propellant hobbyist rocket are that its fuel and oxidizer must be readily-available, non-corrosive, non-toxic, non-hypergolic, and not subject to self-detonation.

Since the acetylene molecule has (if I remember my hydrocarbon chemistry) a triple carbon bond, pressurizing the gas beyond 15 PSI must tend to break that bond (without the presence of acetone for the acetylene gas to dissolve in) and cause the acetylene molecules to decompose, with the release of the bonding energy as heat. (Yep, that's what the Wikipedia article on acetylene says--it's subject to explosive decomposition if pressurized.)

Acetone itself might make a good low-ISP liquid rocket fuel. Isopropyl alcohol (rubbing alcohol) and denatured alcohol ("methylated spirits"--ethyl alcohol containing 10% methyl alcohol to make it undrinkable and not subject to liquor taxes) would also make good readily-available liquid rocket fuels, although their ISPs would be on the high side for hobbyist use. Propane or butane in cartridges could also be used as fuels, and since the cartridges are pressurized, the fuel would force itself into the engine. The oxidizer could be pressurized gaseous oxygen (which I *think* I saw in small CO2-type cartridges for hand-held oxy-butane torches) or nitrous oxide. Or possibly...

If "drug store" hydrogen peroxide is this "exothermically tame" when it decomposes, this could make it useful for the rocket. It could all be decomposed in the rocket's oxidizer tank by exposure to a catalyst, and the released, self-pressurized gaseous oxygen "head" above the leftover water in the tank would be injected into the engine to burn the fuel. The water could serve as engine coolant, which would boil and be ejected with the exhaust. Also, some of this steam could be tapped off and used to pressurize both the oxidizer and fuel tanks (if pressurized butane or propane cartridges weren't used as fuel tanks).

How about propane lighter fuel cartridge and a nitrous oxide cartridge?? How do they burn together?? Both are self-pressurizing low cryogens and remain liquid under modest pressure at normal temperatures, so they would provide their own ullage pressure to inject the propellants into the engine (so long as the combustion chamber pressure does not exceed the vapor head pressure in the propellant tanks, that is).

Interesting idea about the alcohol... I read somewhere that the V-2's were propelled on alcohol brewed from POTATOES-- fuel was in SUCH short supply in Germany late in the war that ANYTHING that used alternative fuels was highly desirable... BUT the ground crews tended to get falling-down drunk from dipping into the rocket fuel for a ready supply of alcohol, so they had to add a barf agent to the alcohol rocket fuel to keep the guys from drinking it, or make them puke their guts out if they DID...

Heck the Germans even experimented with DIESEL airplane engines in bombers, but abandoned the idea because the performance was SO low in the thin air at altitude and they were SO heavy...

Later! OL JR :)

[luke strawwalker]

For this engine, that was never my plan (using the hydrogen peroxide as an oxidizer); rather, the peroxide would be the source from which gaseous oxygen would be liberated (in keeping with the criteria that for hobbyist use of this engine, the oxidizer and fuel must be readily-available, non-corrosive, non-toxic, non-hypergolic, and not subject to self-detonation).I may buy another one--they have more designs than I thought!

I think the idea of gaseous fuels will be a non-starter-- at least generating gaseous fuels from other substances (like calcium carbide or peroxide) onboard... the reactions are SO slow and the volume of gases you'd need to support combustion are too high for it to work...

Course yall can prove me wrong, but that's my gut instinct...

There's a reason rockets use LIQUID fuels and not compressed gases for fuels, even though the compressed gases would be INFINITELY easier to handle (compared to cryogens like LO2, anyway)...

Still think self-pressurizing liquids like propane and nitrous oxide are the simplest way to go... sorta like a "cold propellant" rocket that actually combusts it's fuels...

Later! OL JR :)

[blackshire]

How about propane lighter fuel cartridge and a nitrous oxide cartridge?? How do they burn together?? Both are self-pressurizing low cryogens and remain liquid under modest pressure at normal temperatures, so they would provide their own ullage pressure to inject the propellants into the engine (so long as the combustion chamber pressure does not exceed the vapor head pressure in the propellant tanks, that is).Is nitrous oxide available in cartridges? (I'm not asking in an accusatory way--I just don't know.) If it is, then nitrous oxide/propane (or nitrous oxide/butane) would be the way to go--readily available in pre-pressurized reservoirs!Interesting idea about the alcohol... I read somewhere that the V-2's were propelled on alcohol brewed from POTATOES-- fuel was in SUCH short supply in Germany late in the war that ANYTHING that used alternative fuels was highly desirable... BUT the ground crews tended to get falling-down drunk from dipping into the rocket fuel for a ready supply of alcohol, so they had to add a barf agent to the alcohol rocket fuel to keep the guys from drinking it, or make them puke their guts out if they DID...That "dual-use" booze once flowed freely at Cape Canaveral, too! My late friend Gary Moore worked for Bell Telephone from 1957 to 1967, and he worked for them at the Cape for a time (he worked in their radio shop and had special expertise with their old "wet paper" datafax machines). He and the blockhouse technicians soon discovered that the Redstone missiles' ethyl alcohol fuel made *great* mixed drinks (especially with orange juice and cranberry juice). After a while, the powers-that-be started adding a purple food coloring dye to the rocket fuel to make it look unappealing, but Gary and his fellow "samplers" found that its taste was unaffected and kept right on enjoying it.Heck the Germans even experimented with DIESEL airplane engines in bombers, but abandoned the idea because the performance was SO low in the thin air at altitude and they were SO heavy...NASA developed a turbocharged diesel aircraft engine for light planes, but I don't know how well (if at all) it would perform at 30,000 - 40,000 feet.

[billspad]

How about propane lighter fuel cartridge and a nitrous oxide cartridge?? How do they burn together?? Both are self-pressurizing low cryogens and remain liquid under modest pressure at normal temperatures, so they would provide their own ullage pressure to inject the propellants into the engine (so long as the combustion chamber pressure does not exceed the vapor head pressure in the propellant tanks, that is).

Propane in a tank at room temperature is around 50 psi and nitrous is around 600 psi. You're going to need a combustion chamber pressure of at least a couple hundred psi. It won't work without a pump.

I think you mean butane if you're talking about lighter fuel cartridges. It's no better.

[blackshire]

Propane in a tank at room temperature is around 50 psi and nitrous is around 600 psi. You're going to need a combustion chamber pressure of at least a couple hundred psi. It won't work without a pump.

I think you mean butane if you're talking about lighter fuel cartridges. It's no better.The system could be made autogenous (self-pressurizing--in this case, self-pressure-increasing, since the fuel and oxidizer cartridges are already pressurized). A water jacket surrounding the engine's combustion chamber would absorb heat from the initial, relatively low-pressure combustion. As the water inside the jacket boiled, the steam could be piped into the fuel and oxidizer cartridges via a double-flow, concentric "needle-type" valve that would fit into each cartridge.

The outer, annular part of each valve would allow the fuel and oxidizer to flow down to the engine under their own "pre-packaged pressure." The inner, "needle" portion of each valve would extend up through the interior of each cartridge, with its "needle" opening located above the level of liquified gas inside each cartridge. The steam from the engine's water jacket would force its way into the fuel and oxidizer cartridges through the "needles" and create a larger "head" pressure inside the cartridges (above the liquid in each one), which would force the propellants into the engine at a higher pressure. If the commercially-available, pre-packaged nitrous oxide and propane (or butane) cartridges proved unsuitable to handle this extra pressure, the engine could be supplied with purpose-manufactured fuel and oxidizer tanks capable of withstanding the pressure, which could be filled from these cartridges.

[billspad]

The system could be made autogenous (self-pressurizing--in this case, self-pressure-increasing, since the fuel and oxidizer cartridges are already pressurized). A water jacket surrounding the engine's combustion chamber would absorb heat from the initial, relatively low-pressure combustion. As the water inside the jacket boiled, the steam could be piped into the fuel and oxidizer cartridges via a double-flow, concentric "needle-type" valve that would fit into each cartridge.

The outer, annular part of each valve would allow the fuel and oxidizer to flow down to the engine under their own "pre-packaged pressure." The inner, "needle" portion of each valve would extend up through the interior of each cartridge, with its "needle" opening located above the level of liquified gas inside each cartridge. The steam from the engine's water jacket would force its way into the fuel and oxidizer cartridges through the "needles" and create a larger "head" pressure inside the cartridges (above the liquid in each one), which would force the propellants into the engine at a higher pressure. If the commercially-available, pre-packaged nitrous oxide and propane (or butane) cartridges proved unsuitable to handle this extra pressure, the engine could be supplied with purpose-manufactured fuel and oxidizer tanks capable of withstanding the pressure, which could be filled from these cartridges.


I guess anything is possible but there a couple of major problems with this. You can't make steam instantly. Having a rocket sitting on the pad simmering for a few minutes is not desirable. But the biggest issue is that you can do the same job easily with stuff that already exists. If you want to build one to demonstrate your engineering expertise, that's cool and you should do it. Otherwise it's just not practical.

[rstaff3]

Yes, nitrous is available in cartridges, which are the basis of the micro-hybrids.

If you haven't followed Paul Breed's http://unreasonablerocket.blogspot.com/ saga, you should check out his blog. Then ask him how easy this type stuff is. Paul's done some amazing stuff since its mostly him and his son in a garage (propellant work done at the RRS facility).

[luke strawwalker]

The system could be made autogenous (self-pressurizing--in this case, self-pressure-increasing, since the fuel and oxidizer cartridges are already pressurized). A water jacket surrounding the engine's combustion chamber would absorb heat from the initial, relatively low-pressure combustion. As the water inside the jacket boiled, the steam could be piped into the fuel and oxidizer cartridges via a double-flow, concentric "needle-type" valve that would fit into each cartridge.

The outer, annular part of each valve would allow the fuel and oxidizer to flow down to the engine under their own "pre-packaged pressure." The inner, "needle" portion of each valve would extend up through the interior of each cartridge, with its "needle" opening located above the level of liquified gas inside each cartridge. The steam from the engine's water jacket would force its way into the fuel and oxidizer cartridges through the "needles" and create a larger "head" pressure inside the cartridges (above the liquid in each one), which would force the propellants into the engine at a higher pressure. If the commercially-available, pre-packaged nitrous oxide and propane (or butane) cartridges proved unsuitable to handle this extra pressure, the engine could be supplied with purpose-manufactured fuel and oxidizer tanks capable of withstanding the pressure, which could be filled from these cartridges.

Here ya go... Yahoo is your friend... :) http://en.wikipedia.org/wiki/Whipped-cream_charger

I think there are larger ones as well... about the size of the large paintball CO2 cartridges.

It takes a LOT of heat to bring ambient temp water to the boiling point in the typical 2-3 seconds a rocket motor would burn... I don't see that happening... heck a steel motor combustion chamber of any thickness would probably only be approaching 200 degrees + in that length of time itself, to say NOTHING of the 'coolant'... SO I think that idea is a total non-starter. Look at a table of the specific heats required to get steam up to the pressures you're talking about to augment the injection pressures and you'll quickly see what I'm talking about...

I don't think a pressure of several hundred PSI would be required... Estes engines only operate at about 70 PSI IIRC... ISP is directly tied to combustion chamber pressure, but for a small hobby motor, extremely high pressures isn't desirable anyway. BUT, if the head pressure in a butane cartridge is insufficient for injection, then going back to a pressure-fed system utilizing a fuel tank of alcohol or other liquid fuel pressurized by a high-pressure paintball/BB gun C02 cartridge to create the injection pressure would be a preferable alternative.

I'd give up on the idea of counting on 'boiling steam' for anything... (other than making spearmint tea... yummy! :) )

Later! OL JR :)

[blackshire]

Yes, nitrous is available in cartridges, which are the basis of the micro-hybrids.

If you haven't followed Paul Breed's http://unreasonablerocket.blogspot.com/ saga, you should check out his blog. Then ask him how easy this type stuff is. Paul's done some amazing stuff since its mostly him and his son in a garage (propellant work done at the RRS facility).Thank you, Dick. I see that he is also working on gasoline/peroxide liquid propellant engines!

[blackshire]

Here ya go... Yahoo is your friend... :) http://en.wikipedia.org/wiki/Whipped-cream_charger

I think there are larger ones as well... about the size of the large paintball CO2 cartridges.Thank you! I never knew those N2O cartridges existed, let alone were/are used to make whipped cream! I'd only seen the larger (definitely *not* "flight weight") N2O "bottles" and the even bigger cart-mounted N2O tanks that are used to fill the oxidizer tanks of HyperTek and Aerotech hybrid motors.It takes a LOT of heat to bring ambient temp water to the boiling point in the typical 2-3 seconds a rocket motor would burn... I don't see that happening... heck a steel motor combustion chamber of any thickness would probably only be approaching 200 degrees + in that length of time itself, to say NOTHING of the 'coolant'... SO I think that idea is a total non-starter. Look at a table of the specific heats required to get steam up to the pressures you're talking about to augment the injection pressures and you'll quickly see what I'm talking about...Point well taken, but considering the amount of combustion heat versus the required quantity of water (perhaps just a few milliliters, since water expands to something like 1,700 times its liquid volume when converted to steam), it might work. But it would be better if the system could function without the water at all.I don't think a pressure of several hundred PSI would be required... Estes engines only operate at about 70 PSI IIRC... ISP is directly tied to combustion chamber pressure, but for a small hobby motor, extremely high pressures isn't desirable anyway. BUT, if the head pressure in a butane cartridge is insufficient for injection, then going back to a pressure-fed system utilizing a fuel tank of alcohol or other liquid fuel pressurized by a high-pressure paintball/BB gun C02 cartridge to create the injection pressure would be a preferable alternative.That's what I've been thinking about as well--ordinary alcohol fuel pressurized by CO2, and an (already-pressurized) N2O cartridge for the oxidizer. As you pointed out, the chamber pressure and ISP needn't be great (because this would be a consumer hobbyist product). My purpose in this "design discussion exercise" isn't to develop the ultimate high-performance liquid propellant amateur rocket engine, but to toss back and forth ideas that could lead to a safe, simple, and inexpensive liquid propellant rocket system (or a series of them) for model rocketry and HPR applications. It would even have a logistical advantage over solid propellant rocket motors because it could be mailed anywhere without the propellants, and the propellants could be easily obtained by the "end users" almost anywhere.I'd give up on the idea of counting on 'boiling steam' for anything...It might possibly be of help to larger, HPR-size versions of these engines that would need more pressurizing gas for their bigger propellant tanks, but I'd just as soon use larger CO2 cartridges instead....(other than making spearmint tea... yummy! :) )Sounds good--as long as it's served iced! (Having grown up in Miami, the childhood memories of drinking hot tea on hot, humid nights in a non-air-conditioned kitchen still make me feel the beads of perspiration on my forehead!)

[billspad]

--ordinary alcohol fuel pressurized by CO2, and an (already-pressurized) N2O cartridge for the oxidizer. As you pointed out, the chamber pressure and ISP needn't be great (because this would be a consumer hobbyist product). My purpose in this "design discussion exercise" isn't to develop the ultimate high-performance liquid propellant amateur rocket engine, but to toss back and forth ideas that could lead to a safe, simple, and inexpensive liquid propellant rocket system (or a series of them) for model rocketry and HPR applications.



You're reinventing the wheel. Look at this (http://www.rocketryplanet.com/content/view/3290/29/) . I'm sure it could be scaled down to model rocket size but the weight of the system and the small market make that unlikely.

[blackshire]

You're reinventing the wheel. Look at this (http://www.rocketryplanet.com/content/view/3290/29/) . I'm sure it could be scaled down to model rocket size but the weight of the system and the small market make that unlikely.Hardly--that motor is a tribrid, using three propellant components (liquid oxidizer/solid fuel/liquid fuel). A pressure-fed liquid bipropellant rocket engine system would be considerably simpler than that.

Often the means to develop new devices are in existence for many years before the devices are brought into being, simply because no one thought to bring them all together to create the device. Jet propulsion and gas turbines had been around for a long time before Frank Whittle thought to combine the two to create the turbojet engine.

Speaking of turbojets, for many years tiny gas turbine engines for R/C model aircraft were thought to be either impossible or, if possible, too expensive to be viable, but steady improvements in materials science and production technologies made them practical and affordable. A model aircraft turbojet engine is much more complicated mechanically, pneumatically, and electronically than a model rocket liquid propellant rocket engine system. I have no doubts that such rocket engines will one day be practical and affordable--if the means to make them so don't exist already, just waiting for an entrepreneur to pick up the idea and run with it.

[rstaff3]

Here's a review of a MicroHybrid: http://www.rocketreviews.com/reviews/all/cm_microhybrid.shtml

Here's the microhybrid Yahoo group: http://groups.yahoo.com/group/microhybrids/
Some members are looking at larger versions.

[blackshire]

Here's a review of a MicroHybrid: http://www.rocketreviews.com/reviews/all/cm_microhybrid.shtml

Here's the microhybrid Yahoo group: http://groups.yahoo.com/group/microhybrids/
Some members are looking at larger versions.Thank you for posting these links, Dick. The Dutch-made Caveman Rocketry micro hybrid fits in BT-50 size rockets! It's not hard to envision a small liquid propellant engine system of similar size that would use the N2O cartridge and (instead of the paper fuel grain) a propane or butane cartridge, feeding into an ablatively-cooled or radiatively-cooled engine.

[luke strawwalker]

It's not the MASS of water you have to bring up to the boiling point, or the temperature of the heat source (engine combustion temperature, which is to some degree determined by operating pressure) but ALSO the insulating or heat conducting properties of the engine materials themselves...

It's like running your finger through a candle flame-- if you do it quickly enough, you don't even feel the heat. Go slower and you feel the warmth as your finger pierces the flame. Go slower yet and you get the sting of "HOT" gases as your finger goes through the flame. Hold your finger in the flame for a couple seconds and you'll have a nice burn to treat...

You're not talking about 5,500 degree combustion of hydrogen and oxygen in an SSME for 8 minutes here... We're talking about combustion temperatures of MAYBE 1,000 degrees or a bit more for only a few seconds... Even an oxy-acetylene torch takes several seconds to heat a single spot in 1/8 thick steel plate red hot, and an oxy-acetylene torch is SIGNIFICANTLY hotter than any of the proposed rocket fuels being proposed here... it takes TIME for the heat to transfer through the piece and into the fluid, and then convection of the fluid tends to make the hotter fluid rise and cooler fluid be drawn in to take it's place, and setting up that convection current means the fluid itself takes MORE time to heat up to the boiling point...

You can boil ANYTHING given ENOUGH HEAT and ENOUGH TIME... You can boil steel into vapor-- half a day or so in a carbon-arc furnace will do... or a few thousandths of a second in close proximity to the million-degree heat of a nuclear explosion... Less heat=more time More heat=less time. Course it's also about the RATE of heat transfer through the material as well... Ever look at the footprints and other shadows of stuff burned into the concrete and painted surfaces in Hiroshima?? The fireball of the Hiroshima bomb was 5,500 degrees F. It cooled quickly from that point. The heat pulse arrived about 1.5 seconds after detonation. The heat pulse was sufficient, at 5,500 degrees, to vaporize human beings, and it spalled the concrete they were standing on-- the surface heated almost instantly SO hot that the outer layer of concrete flaked off from the rapid expansion... yet in the time it took to vaporize people in those conditions, by the time they were gone, the fireball had cooled sufficiently that the remaining radiated heat was insufficient to spall the concrete under where their feet had been-- it simply heated up enough to burn the ashes away, but it didn't spall... thus preserving the 'shadows' of where the people were standing. Same thing with 'shadows' burned into painted walls...

A macabre example, but it makes the point... it takes a certain amount of TIME for the heat to penetrate something and make it hot enough to "feel hot" let alone boil water... that's why PAPER engine casings can work with model rocket motors-- SO LONG AS THE BURN TIME IS SUFFICIENTLY SHORT, and the PAPER IS THICK ENOUGH-- it takes TIME for the heat to work it's way through the paper casing and weaken and char it...

Later! OL JR :)