OUTDATED. Still here for demo users, but this is mostly useless for 0.21+. I previously wrote a different version before the great DDOS attack. Since there is no tutorial sub section, I'll post it here for now. SAS, or ASAS? That is the question. Which one do YOU need for YOUR spacecraft? In this mini-guide, I'll be teaching you the differences, as well as which one to use on specific aircraft/rockets. First of all, to use any one of these parts, press T to toggle (on/off) or F to trigger (holding F will keep SAS on). SAS SAS is your basic rotational stabilizer. Usually used on rockets, SAS stops your rocket from spinning all over the place. SAS has rotational torque only, making it useless for vertical and horizontal stability. However, SAS can be useful when launching large rockets, to prevent them from entering death spirals. http://wiki.kerbalspaceprogram.com/wiki/S.A.S._Module ASAS ASAS stands for Advanced SAS, and keeps the entire aircraft/rocket stable. It does this by using other controllable parts. ASAS, unlike SAS does not have any torque itself, so by itself, it is useless. However, ASAS utilizes gimbal engines, winglets/canards, RCS and other parts with torque (Command pods and SAS) to keep the craft stable. http://wiki.kerbalspaceprogram.com/wiki/Advanced_S.A.S._Module Avionics Package The avionics package is basically the same as ASAS; it utilizes other parts to stop your craft from moving. The AvPa is usually mounted on a nosecone. http://wiki.kerbalspaceprogram.com/wiki/Avionics_Package