I had a gracious reply from Edward about formulating Jetex pellets:
"I've a stock of ammonium and potassium dichromate, high-grade kaolin, AN, GN, 2,4-DNT, asbestos
(!), vanadium pentoxide, along with sundry supportive reagents (nitrates, perchlorates, resins, binders), so it's likely I'll
likewise see what's possible with the Sebel/Jet-X formulations.
Guanidine nitrate has for decades been an item of special interest (along with ammonium nitrate), for its exceptional ability to sustain
combustion at low pressures, decompose at low temperatures, and produce only harmless exhaust gases. (Dichromate propellants are clearly toxic, and really aren't suitable for indoor use, unlike GN formulations.)
GN based Jetex-type formulations work with a highly-complex and ill-understood thermochemical process that requires both catalysts and burn-rate modifiers. V2O5 is one of those key catalysts, and even V2O5 (Vanadium pentoxide, I think) depends upon a both embedded asbestos fibers and an alloy screen to function correctly.
While I'll see how far we can go with cardboard tubes as test motors, I expect that right away it will be imperative to run with
conventional Jetex 50 motor cases and nozzles (and sealing washers,
and wire gauze screens).
At this moment, my focus is upon (basically) replicating the original ICI cardboard-tube motor and earliest formulations, per published
patents. I fully expect to re-invent the wheel in this project, but hope to avoid re-inventing the spokes, axle, bearings, suspension, and
so forth, so to speak".
In my interview with Alex Hutchinson, it was the use of asbestos to provide a surface for complete ignition of the GN he seemed most proud of. Sebel and Tiger pellets used kaolin which required toxic dichromates in the mix. Yes, it worked, but not as subtle. Bert Judge was of the opinion that the wire gauze used in Jetex motors was merely to keep the wick in place and as a filter of muck from ignition.
I've taken to nicknaming this formulation "S-Stoff 991" to completely differentiate it from all previous Jetex guanidine nitrate formulations.
In truth, I don't like to speak of S-Stoff 991 in the same breath as referring to the original propellants from Imperial Chemical Industries (ICI). I have on the laboratory table beside me the reagents for both S-Stoff 911 and ICI-type, and tomorrow I intend to mix a batch or three of the former.
It's going to be a chore I don't look forward to, quite honestly, since the key ingredient in S-Stoff is that colorful salt of potassium and chrome: potassium dichromate [aka bichromate]--clearly nasty, potent, vile, those beautiful California-poppy colored crystals in the candy jar. It's really the first cousin of Vesuvius' Fire, ammonium dichromate. It's a potent oxidizer, and then some, in toxic sorts of ways, alas.
So if I manage 3 or 4 batches tomorrow, off comes the respirator, eye protection, face shield, gloves, and Tychrem hazmat suit, and I'll turn to my personal favorite solid propellant: GN-based, 2,4-dinitro fueled, V2O5 catalyzed, asbestos-fiber enhanced, ICI formulations. Those reagents are quite gentle, even predictable, compared to the nasty brilliant orange crystals of dichromate/bichromate.
Compare with, for instance, KNO3 [saltpeter], NH4ClO4 [ammonium perchlorate, as in Rapier], and CH6N4O3 [guanidine nitrate].
I've worked with high-energy chemicals all my long life, and I proceed with these Jetex dichromate experiments slowly and carefully, strictly in the interests of publishing recent and modern accounts of what's possible in a small lab. When all's said and done, I doubt if anyone else will want to tread this path knowingly.
As an ex-research chemist ( I.C.I. Paints Div.), I always considered that the gauze was absolutely nothing to do with catalysis and wonder where people got that idea. The ICI fuel pellets burn just fine with no gauze - QED. The gauze served 2 purposes: 1) Keeping the igniter wick pressed against the pellet 2) Preventing any lumps/ash reaching the jet orifice and blocking it.
I'm certainly interested in pursuing new Jetex-type fuel and, even more important, some way of igniting it without that pesky, unavailable, disintegrating igniter wick. Does anyone know if that Dutch (?) D-cell powered igniter worked? One just sold on eBay for $137.50 !! I was interested for a while - but really!! I have an idea for a different way of igniting the fuel, but it's very dependent on inserting something into the orifice - (sorry about that).
Does anybody know anything about the Jet-X fuel? Was it any good?
Geoff is correct - in our interview with Bert Judge, he maintained the gauze was there to keep the wick up against the pellet and to filter out any particles that would clog the orifice. Not that there was much gunge from an ICI pellet.
Asbestos in the pellet provided a surface for complete combustion - Alec Hutchison, who developed the ICI pellets with James Taylor, says he was particularly proud of this discovery.
Sebel pellets were of course different, and created a lot of gunge when burning. This could clog the Wilmot Mansour gauzes. Thus the stainles steel Sebel gauzes were coarser mesh.
Jet-X, Powermax pellets, which were basically wood flour and ammonium nitrate, were very variable - some OK, mostly only good to put around the roses.
Powermax fuse, though, is excellent .
John Nesbit developed and sold a hot wire igniter some years ago - I have two - but they needed a very good high capacity low resistance size 'C' (or was it a 'D' ?) battery, and I for one couldn't get it to work.
Something similar though could be developed using today's improved battery technology.
Oh dear! I posted 45 minutes worth of typing here this morning and "submitted," but it's vanished into the ether. So frustrating. I broke my golden rule - always store it in WORD first, because this sort of thing happens too frequently.