It is the denser fuels injected into the nozzle I am refering to. The Lox and kerosine both need to be vaporized before TAN injection if I am right. You can’t route the TAN propellants through the cooling jacket of the main chamber because the primary chamber propellants must do that job after TAN shuts off. Changing cooling systems in mid flight would probably be a very bad idea.

Vaporizing the kerosine before injection is going to be a real trick. The hydrogen uses whatever normal injection into the main chamber as an unaugmented engine, and it plays no part in the TAN injection.

Is it possible you are overthinking problems with TAN here? On the gas/gas injection question, for instance. In a TAN design, You have to route the augmenting fuel and oxidizer that you want to inject past the main combustion chamber and throat to some downstream location on the nozzle. Since you need that plumbing to pass over hot portions of the nozzle in any case, why not put the two in contact and transfer some energy to vaporise your propellants?

My understanding was that in a TAN you inject the denser propellants into the nozzle and use the higher performance reaction in the core engine. So you don’t need a heat exchanger to vaporize H2 just before injection into the nozzle, or whatever you were getting at.