Calling all Engineers

[Bruce R. Schaefer]

While it is always a mistake (or not) to transfer theories and applications from one mode to another, what if the water tank was pre-heated, for pressure, but also to spray the “pre-steam” into a “steam chamber,” just as liquid fuel rockets spray the oxidizer and fuel into a combustion chamber? You have a water tank electrically heated, then shoot the future steam into a “red hot” steam chamber–however heated, where the water flashes to steam and exits the con/div nozzle at Mach 1? This would have to be done with formulae(as) or empirically. Just a thought, both of you can make fun of me now. 🙄 I think this is a great project, but at times, seems like re-inventing the steam engine… or not.

[bryans]

Anyone know a way that we could heat the tank? To temperatures of about 700 degrees? Heater blankets, even a burner.

Since you are not launching this motor, seems like propane torch or single camp stove burner would be straightforward. Get the hell away from it though, if you over-pressurize your vessel (‘s weakest point, including valve) you could have projectile pieces or the whole thing going in random directions and burning people. To easy to think that it won’t hurt cause “we just put water in there”, at least for small brained folk like me.

Heavy nichrome wire might work nicely, but you need a fair amount of power behind it. For instance, i use 16 gauge nichrome, about 26 inches of it, to cut foam, which is supplied by around 2V at maybe 40A. So i am dissipating 80W over 2 feet of wire that has a pretty small surface area. I figure the wire gets to 400F or more, should do 1000F easily, i just don’t know when the wire will melt or break down violently and pop since i do not know the composition of this particular wire. Hair dryers and toasters use exactly this arrangement.

Same principle was applied with a longer piece of the same wire, maybe 10 feet, curled around under carpet in a dog house we built… longer wire = more resistance, lower current at the same voltage. So we make the wire maybe 80F, which heats up the carpet and the dog house enough to keep the inside above 20F when the outside temp is below zero.

The neat part is that the heating element could be pretty light versus the rest of the vehicle, and detach is easy with just two terminals (or even one if the current return happened through conductive lugs to the rail and launch pad). Since you are not launching, you don’t really care about that.

The application problem of this heater in a rocket motor is all about insulating the wire from shorting against your steam vessel… kevlar cloth maybe? Insulate around that too so it doesn’t take forever to heat up. Fortunately you do not have to go too nuts since you are doing ground tests, but if you were building in a vehicle you would have to figure out how to do your heating phase without burning down or melting the rest of the rocket. That would be a Bad Deal.

Love steam power regardless.

[dan winter]

I have a copy of “Steam Rockets-2” by B.J. Humphreys and F.B. Wagner, Areo-Visions, Inc Manuals of Steam Rockets 1972. Also their “Hot Water Rockets, Development and Applications by Robert Truax a bit later vintage 1980.

The bird described uses a 110 cu ft (appox.) Air Force surplus oxygen tank/nozzle as the propellent tank. The height of the steam rocket is 6’8″ It holds 30lbs. of water heated to 470’F @ 500lb.psi with an impulse of 45 seconds. Complete with relief valve,chute/release mechanics, and an instrument section. And complementary descriptions of the launch cradle/release mechanism. Included are the plans for the launch bunker. Handily constructed of several layers of railroad track wooden ties heaped with dirt! The important part…the 1/2″ wide peep slit for viewing all the excitement.

I made several steam motors from spent CO2 cartridges…most impressive! All were externally heated with a small propane torch. I never had the guts to see just how long it took to blow one up…they will take 4-5 minutes of heating without blowing. The more they are heated, the greater the super heating of steam, and the faster they left the ground. (Most unscientific and no place for the Cub Scouts)

If I were to build a large one, A flue section in the lower section of the tank would help expedite the heating process. Additionally insulation around the tank. The use of a weed burner for heating. One could go through a bit of propane heating a large rocket….

All the foofaraw about AP I was very prepared to use steam rockets….
I surmise this type rocket would still fall under ATFE jurisdiction as is a generally defined, “Dangerous Devise?”

I used to operate steam locomotives…the blow down from a 2″ valve/pipe @ 180lbs psi. is a most impressive sight and sound!

Anyone for a few drops of hydrogen peroxide/N pressurized on decomposing screen layers?

Dan

[Kyle Parsons]

So we finally finished the project and it was due today. We rushed to even get a good test off and did the first and only successful test yesterday. We ended up using a oxygen cylinder and a ball valve. I machined the nozzle myself going off of dimensions from graphite nozzles. For the heating source we tried to use a heating cord that was rated up to 900 degrees F and wrap it around the tank. Sadly it didn’t even get the tank close to hot enough or create any pressure. So we put a oxygen acetylene torch to it and finally got some pressure. With about 10 fluid ounces of water and the tank at 212 psi, I read 22.5 pounds of force initial and for about 3 seconds it gradually decreased.

http://www.youtube.com/watch?v=sfhUCGHJ9JU

[Author]

Posts