The Active Mass Balance Auto-Control (AMBAC) is a fundamental technology that allows for thruster-less maneuvering in the zero-G environment of space by mobile suits by means of precise movement control of their limbs.
OverviewAMBAC works by leveraging Isaac Newton's Third Law of Motion (When there's an action there is an equal and opposite reaction) with regard to inertia to effect changes in direction. For example, if we place a person in a micro-gravity environment where friction is negligible (i.e. space), and 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 rest of his body turning the other direction in order to conserve angular momentum. Then when the motion of the arm stopped, the rotation of the body would also stop. The AMBAC system coordinates movements and micro-movements precisely, allowing a continuous balance and stability without expending reaction mass. For the most part, AMBAC is invisible to the naked eye, as the shifts are slight. The system can be used to dodge incoming projectiles or small objects as the arms and legs of a mobile suit account for a significant portion of its total mass. The AMBAC system also allows the center of mass to shift outside of the body. AMBAC is by its nature limited to re-orienting the unit about its center of mass, and is not a substitute for propulsion. It is often used in conjunction with the propulsion system to quickly turn the unit and shorten aiming speed as well as directing the main thrusters. The system is similar in principle to the momentum wheel system used in present day satellites, though obviously more complex. Mobile suits performing AMBAC motions would presumably move similarly to present-day astronauts performing extra-vehicular activity: both typically having roughly similar body structure, their use of that mass to control their rotation would presumably be similar, even if calculated by different means.
Tail Binder and Wing Binder
Binders are technological instruments that provide extra control for the AMBAC systems. The idea is simple: "If four limbs can maneuver the unit better than none, why not equip them with 5 or more?" The resulting advancement is the tail binder. First equipped on MSN-00100 Hyaku Shiki, the tail binder was originally used as part of the interface for the testing of the concept of transformable mobile units (the type installed on the Hyaku Shiki is not technologically advanced enough for it to be able to transform, however). The tail binder ultimately served as the fifth limb and demonstrated the usefulness of the concept. The unit performed well against more conventional mobile suits and showed superiority in manoeuvrability. Anaheim Electronics had since then installed tail binders on most of the mobile suits of the same series under Project Zeta, most notably the MSZ-006 Zeta Gundam.
A cousin to the tail binder is the wing binder, equipped on most transformable mobile suits with waverider mode as wings. The system made use of the wings' mobility for the transformation during mobile suit mode as AMBAC limbs and further increasing the number of limbs for the AMBAC system. The tail binder is also seen on later models of military aircraft and space fighters in U.C.0088, on the FF-08-GB/WR Wyvern.
In Mobile Suit Gundam SEED Astray, George Glenn utilize AMBAC while assisting Kisato Yamabuki piloting TMF/A-802 P-Mod.W BuCUE Waltfeld Custom Type, allow it to maneuver in space despite being land combat MS.
In the Anno Domini time-line, The Gundams (and by extension other GNMS) rely on this for their mobility in zero-g space where they lack the ability to manipulate weight using GN Particles and is vital to mobility focused mobile suits such as Gundam Exia.