And here’s the tail end f the UA-1205 motor, showing details of the thrust vector control system. On this motor, TVC was by fluid injection: a bit downstream of the throat there were a multitude of small injection ports in the nozzle. Valves would, on command open some and close most of the others, allowing pressurized N2O4 to be injected. The temperature increase would cause the fluid to flash to a gas, forming something like a “bubble” over the injection port; this would cause a disruption in the exhaust flow, causing the thrust vector to be shoved around. And thus, no moving parts needed in order to achieve the effect of a nozzle that can be slewed around. Of course, this was at the expense of a big tank of TVC fluid hanging off the side.
