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.
AMBAC 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 a person was placed in a micro-gravity environment where friction is negligible (i.e. space), and asked 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 activities: 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.
The AMBAC system was first demonstrated by the AMBAC Spacepod test made by Zeonic; the system allowed the space pod to have greater agility and fuel efficiency than MIP's competing design, the MIP-X1 mobile armor. The system was then expanded to four limbs, two arms two legs, with nearly all subsequent mobile suits.
Wing Binders and Tail Stabilator
Wing Binders and Tail Stabilator 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 wing binders concept was first utilized on MSN-00100 Hyaku Shiki as a part of its transformation system, they were originally supposed to help the mobile suit move effectively even while it is in mobile armor form. When the Hyaku Shiki's transformation system fails, the mobile suit was retooled into a non-transformable unit and the wing binders were kept as they can serve as additional AMBAC limbs. As a result, the unit performed well against more conventional mobile suits and showed superiority in maneuverability. Anaheim Electronics had since then installed wing binders on the back of most of the mobile suits of the same series under Project Zeta, most notably the MSZ-006 Zeta Gundam.
A cousin to the wing binders is the tail stabilator, an elongated binder that is also mounted on the mobile suit's back and can serve to increase the unit's AMBAC capabilities. Some variants of the tail stabilator are equipped with built-in vernier thrusters and can thus further improve a mobile suit's maneuverability. Besides being mounted on transformable mobile suit, it is also used by non-transforming units such as PMX-003 The O. The tail stabilator continues to be used on MS developed after U.C.0087, an example is the RGZ-91 Re-GZ.
In Mobile Suit Gundam SEED Astray, George Glenn utilizes AMBAC while assisting Kisato Yamabuki pilot the TMF/A-802 P-Mod.W BuCUE Waltfeld Custom Type, allowing it to maneuver in space despite being land combat MS.
Although the exact term is not used, the GSF-YAM02 Guardshell MA mode can maneuver in space by movement of its three legs.
In the Anno Domini time-line, AMBAC is also utilized by mobile suits for maneuverability in zero-G space. In addition to the standard AMBAC concept seen in other series, the GN Drive-type mobile suits' AMBAC system can take advantage of the GN Particles' ability to alter mass to manipulate the mass ratio of each parts of their bodies.
Although the exact term is not used, the AGE-1R Gundam AGE-1 Razor uses inertial force generated by the weight of its massive blades for maneuvering, much like AMBAC.