The engines can be throttled over a thrust range of 65 to 109 percent, which provides for a high thrust level during lift-off and the initial ascent phase but allows thrust to be reduced to limit acceleration to 3 g's during the final ascent phase. The engines are <a href="Glossary">gimballed</a> to provide <a href="text">pitch</a>, <a href="text">yaw</a> and <a href="text">roll</a> control during the ascent. This is the most powerful thrust for its weight of any engine ever developed.