Composite paraffin rocket?

Anybody done any experiments with paraffin fuel and a solid oxidizer?

I have an inexpensive source for potassium nitrate (wish I could find an inexpensive source for other oxidizers, ammonium perchlorate, ...), and was thinking about making some composite paraffin motors. Seems like it should work fine.

If you've built/tested some paraffin motors, please post results/pictures/...

Thanks!

Reply to
rpseguin
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I'm curious, what's the melting point of your paraffin?

Reply to
Dave Grayvis

It would crack and your rocket would explode.

Reply to
jj

I believe it would not. Most paraffin waxes have a bit of oil present as a plasticizer. Unless the motor were quite cold, or the solids loading quite high, the charge should show some elasticity. Asphaltum motors are quite reliable, if low on impulse.

I'd be much more concerned with the transparency of paraffin allowing IR from the flame to penetrate and subsequently to melt the charge ahead of the flame front. It might be necessary to add an opacifier like carbon black to prevent that.

LLoyd

Reply to
Lloyd E. Sponenburgh

That would be My concern also.

Reply to
Dave Grayvis

I'm not sure of the melting point of the parrafin, but I will try to investigate. Need to pick up some thermometers. The paraffin I have readily available is just store bought paraffin wax from Safeway or Orchard Supply. Comes in 1 pound boxes.

Good point about the opacity. Carbon black is easy enough to add to the mix. Looking at this image presumably of the Stanford/NASA Ames paraffin fuel grain, it doesn't look particularly dark/opaque (it is opaque, but looks like mostly due to the thickness of it):

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Any idea on the ratio of oxidizer to fuel to use as a starting point?

65/35 -ish?

Could also do paraffin/sucrose/carbon/KNO3 mix or other compositions.

Thanks!

PS- Anybody here have a CNC lathe that is willing to turn a few nozzles?

Reply to
rpseguin

For what its worth: I made 6 pound whistle rockets about 8 or 10 years ago and used fully refined paraffin (before I found out about vaseline). They all blew up. I then changed catalysts from red IO to rutile (for sound and IR opacity) and had fewer blow up. Then I tried adding 3% graphite powder and had none blow up. They smoked REALLY bad, which was kind of a nice effect. When I switched to vaseline, everything was faster, easier, and far cheaper. The vaseline rockets carried twice the payload. I never dialed in the wax rockets, but feel that there is much research needed to fully realize their potential.

Regina

Reply to
missmonkeyshine

Vaseline/petroleum jelly mixture/formulations please...

Reply to
rpseguin

I never tried paraffin but tried the GALCIT 61-C asphalt fuel with KCLO4 with a very rudimentary nozzle many years ago. I tried it simply because it sounded so simple to make and cast. This was used in the early 1940s on JATO (jet assisted take off) units for the navy carrier planes as I recall. If you Google up "GALCIT" (Guggenheim Aeronautical Laboratory California Institute of Technology, you'll find a lot of info on the early solid composite fuels and why they settled on polysulfide rubber (Thiokol) with ammonium rather than potassium perchlorate. The formula for the Caltetec #61-C is KCLO3 76%, Fuel

24%.. The "fuel" is a mix of 70% n 18 degree asphalt mixed and melted with 30% SAE 10 weight oil. I used a waer bath to melt the fuel and mix in the perchlorate. Yep! The rocket motor blew up on static firing the first and last I tried. A note to the unwise kiddos: if you make this stuff, and it catches fire, you have the equivalent of a sticky NAPALM to try to get off your skin. And yes, the boys at Caltec tried NAPALM with perchlorate as well.

John

Reply to
John Reilly

Whoops, that was KCLO4 not KCLO3!

John

Reply to
John Reilly

Reply to
Rick

"DANGER , WILL ROBINSON!" (Remember that classic line?)

It strikes me that some of the formulations mentioned so far in this thread have a frightening similarity to compositions that Tenney Davis speaks of on pages 360-366 of his classic text. Cheddite 60B in particular, has a detonation velocity estimated at 2774-2843 meters/second when encased in paper, or about 1/2 that of solid TNT.

Some rocketry enthusiast are aware of this fact, while others are not. Anyone experimenting with composite oxidizer/hrdrocarbon mixtures should be aware of the high explosive risk associated with such propellents, since the possibility of unexpected detonation is a very real hazard.

For obvious reasons I have not posted the components of the more common Cheddite compositions, but some closely approximate compositions already discussed in this thread. For anyone experimenting with such mixtures, a close reading of Davis is both a required and reasonable exercise in safety, since a high order detonation "would be bad" (see "Ghostbusters" for an explanation of precisely what "would be bad" signifies).

Stay safe, and kindest regards. Harry C.

Reply to
hhc314

John -

Have you (or anyone else here) a copy of the 1937 paper by J. W. Parsons (inventor of the JATO) surveying various solid-fuel combinations? It was classified for many years but is supposed to be in the open literature now. I don't think it was ever published.

The two biographies of Parsons in print are next to worthless with regard to his accomplishments in military pyrotechnics and aerospace - they're more concerned with the sensational stuff surrounding Parsons's many amours, his involvement with the occult, and how L. Ron Hubbard snookered him out of his money and ran off with his mistress (all this before founding Scientology!).

Reply to
Mike Swisher

No, I wasn't aware of it nor do I know anything about him (Parsons). I will dig around though, now that you've mentioned it. Sounds very interesting and that time (late 30s early 40s) are interesting as there was such a race of rocket and weapons technology going on with the war in Europe. The fact that old L. Ron "snookered" him is amusing but not surprising for THAT snake! The Church of Scientology! Why couldn't I have thought of a great racket like that?

P.T Barnum (S.J.)

Reply to
John Reilly

The carbon black is in there though, as you can see in this quote from the article.

"The wax that the Stanford scientists chose isn't exactly dinner-table candle wax, but it's pretty close. It includes a small amount of carbon black, a fine soot, to block radiation from heating and softening the inside of the material."

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Reply to
Lex

I don't believe that a mixture of paraffin and KNO3 actually burns, in any ratio. Exotic (or not so exoitic) additives and catalysts may help, but it would probably take a lot of work to find out.

BillW

Reply to
Bill Westfield

Hi .I have a PDF for parrafin .If you have ,i send .Sorry for my bad english :) Write on my e-mail : snipped-for-privacy@gmail.com . And oxigen/fuel ratio for hybrids is in border : 4:1 (ideal) 5:1 6:1 .

Reply to
rapana

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