Ullage motor
（重定向自Ullage engine）
![Three sets of ullage motors are shown in this schematic of the Saturn V rocket](/Images/godic/202502/18/Saturn_v_schematic2336.jpg")
Ullage motors (also known as ullage engines or ullage rockets) are relatively small, independently fueled rocket engines that may be fired to accelerate the rocket prior to main engine ignition, when the vehicle is in a zero-g situation.