So, while I imagine a lot here have read Clarke’s general description of the gelled propellant business, I’ve recently skimmed over Sutton. Since it’s a mid-naughts book, it is more complete - and makes references to a relatively recent (early-naughts) Northrop program that tried to make a tactical rocket using MMH-IRFNA. Sutton doesn’t really cover the gelling agents, and stops at saying they used carbon; several other sources point to boron and aluminium as performance-boosting gelling agents. Their own paper being referenced is paywalled, and my own chemistry education stopped in high-school with a teacher who thought titanium aluminide is impossible.
The big question I have is how can one gelling agent be used for both reducing and oxidizing environments, especially seeing as being in dust form rapidly increases their reactivity, and some of them, like aluminium, are pretty reactive to begin with.
And the minor question is why they used carbon if the main selling point of hypergols over solids is an inherent lack of a smoke trail.