Simulation tests indicate that manual control of the capsule attitude during retrograde firing will be a difficult task requiring much practice on the part of the pilot. By changing the command function from acceleration to rate, the task complexity will be greatly reduced and the developmental effort on display and controller characteristics can be reduced accordingly

There is a natural reluctance to relinquish the mechanical linkage to the solenoid valves but the redundant fly-by-wire systems offer mechanical simplification with regard to plumbing and valving hydrogen peroxide