I was browsing the catalog at one of my favorite chemical suppliers (Darren originally told me about them — Mach 1 Chemicals), looking to submit a few quotes for new bonding agents, as my supply of HX-878 is rapidly aging and I’m looking for a new, possibly more useful, compound. In the middle of my browsing, I happened upon the following entry:

SNPE Butacene® 800 is a liquid resin based on HTPB (hydroxy terminated polybutadiene) and grafted with a ferrocene derivative in the chain. It is used as a binder in high burning rate ammonium perchlorate based composite propellants. It leads to a higher burning rate with low pressure exponent without migration during aging.

It is manufactured by SNPE Energetic Materials (http://www.materiaux-energetiques.com/ — they also manufacture Ammonium Perchlorate and other chemicals for aerospace and defense) and imported by Mach I. The datasheet claims that the chemical structure of Butacene prevents migration of the catalyst, and still allows it to be fully miscible with standard HTPB.

I’m seriously thinking about adding a quote for a pail of Butacene to my list, as well. With 8% Ferrocene by weight, it would tremendously ease the path to a 1 in/sec (or higher) burn rate propellant for endburners, without the use of < 30mic AP, HMX, or other explosives, and without the processing qualms presented by GAP. Though the use of metallocenes has been derided by many manufacturers and consumers (most of the time seemingly without merit), they allow the simple chemical acceleration of a propellant, thus opening doors to new designs.

One of the most inspirational texts I’ve seen as of late was a copy of “Small Sounding Rockets” that I picked up from Paul Yarnold (thanks again, Paulie!). In the chapter discussing Atlantic Research sounding rockets was a page about a vehicle that was 3″ diameter and 5 feet long which reached 100,000 feet with the aid of a breech launcher and an 18-second burn duration endburning motor. With a high burn rate propellant, suddenly this vehicle becomes feasible to reconstruct.

Back in the day, high burn rate motors were made using Polysulfide binders, sub-mic AP and Al, addition of metal wires, and secret blends of catalysts. (Did I miss any?) Mark Clark successfully leveraged these techniques to successfully fire a 3-grain 76mm L5300. But Mark works for Universal Propulsion, so he’s got a bit of a head start.

CTI has also produced fast propellants without any metallocene products. Yes, metallocenes do migrate, so there is a concern there. But this sounds like a way to get around the migration and sensitivity issue (seriously though, if it’s so brutally dangerous to use metallocene compounds, someone show me a video of AT’s Warp 9 being set off with a hammer?) while simultaneously easing processing (no small amounts of catalyst to add) and avoiding the other — potentially more hazardous — methods of speeding up burn rate.

So, I’m thinking of storing this one away in the “high performance” toolbox with the other tricks I’ve gathered, and maybe one day taking a shot at the Black Rock waiver with something no bigger than a L1 cert rocket. Who knows. It just might work.

My other question is — how do you integrate the ferrocene molecule into the HTPB chain itself? Is there some sort of bonding agent that can be used to perform this bit of chemical wizardry, without relying on foreign sources? It may not be a panacea, but it sounds like a vast improvement in the mitigation of a potential hazard caused by “cene” catalysts. (I’m resisting the urge to make so many bad puns off of that…)

Either way, I think there’s some SNPE love coming my way on an invoice sheet in the near future.

Posted June 24, 2008 in Motors. Add Comment / Trackback