Active Mass Balance Auto Control (AMBAC) is a fictional technology in the Gundam universe that allows for thrusterless manuvering in space by mobile suits by means of manipulating their limbs. In conjunction with the fusion reactor developed by Dr. Y.T. Minovsky, AMBAC made mass-production mobile suits for space combat feasible.

How AMBAC Works

AMBAC works by utilizing Isaac Newton's Third Law of Motion with regard to inertia to effect changes in direction. For example, if we place a person in a microgravity environment where friction is negligible (i.e. space), then ask him to place his left arm to his chest, then swing it out to the side, the resulting inertia of the arm movement would result in the person spinning counterclockwise. If this person then repeated the same motion, but with his right arm, the inertia from that motion would cancel out the original motion, halting them. If these motions are timed, one could use them to change their facing easily, spinning till the proper heading was reached, then braking with an opposite but equal motion, using no reactive mass in doing so. Similar motions could be used to move on the other axii without expending reaction mass. An AMBAC system makes these motions more precicely than any human could ever hope to, allowing minute shifts of mass do be translated into course correcting. For the most part, AMBAC is invisible to the naked eye, as the shifts are slight, but there are a few motions that are rather visible - the most common is a jackknifing motion that throws the majority of the mobile suit's weight forward, braking it.