Finite burn effects on ascent stage performance

The use of liquid bipropellants for ascent stage propulsion introduces possible propellant penalties not present when using solid rocket motors. If the velocity increment is achieved in a finite time span, as opposed to an almost instantaneous burn, then the required impulse is higher. Although bipropellants do offer certain unique advantages, these penalties represent an offsetting factor. Four representative missions are used to estimate and minimize these losses. Computer simulations of a specific ascent stage were used to derive penalties. Results indicate that a relatively simple steering strategy leads to almost negligible propellant losses for initial accelerations down to 0.05 g.