SAS

SAS is a control system that will help control you ship by countering rotation. Advanced SAS (ASAS) adds to this by also controlling control surfaces such as wings.

Control

you can turn the system on and off with the T key, and temporarily invert it by holding the F key. The current state of the SAS system is shown by a light on your Navball. The SAS and ASAS are controlled together, you can opt to enable SAS but not ASAS, and vice versa; though as the name suggests ASAS is still SAS but with a more functionality.

All command pods offer a small amount of SAS force, and you can add to this by adding more SAS units to the craft. ASAS however is simply either there or not, you can not add multiple units to increase its effect.

Theory

The S.A.S. modules use a P.I.D. system, which stands for “Proportional, Integral, Derivative”.

• Proportional means the S.A.S. module applies a turning-force that is proportional to the displacement from the "target" orientation. In other words, the further off-line the ship, the harder the module tries to correct it.
• Integral means the S.A.S. module increases the corrective force the longer the ship is off-target. So if the ship is constantly "not-quite" on target, the S.A.S. module will ramp up the force used to correct the ship's orientation.
• Derivative means the S.A.S. module takes the rate-of-turn of the ship in to account, and tries to apply a force against the turn. So the faster the ship is pitching, yawing, or rolling, the harder the S.A.S. module tries to stop the turn. This is supposed to dampen the action of the S.A.S module, preventing overshoot, as well as dampening any fast turn or roll.

The SAS functionality found within command modules use only PD, with no I. The reason for overshoot is that the PID system is not well-tuned yet. The "I" and "P" factors are a bit too powerful, the "D" factor (which dampens movements) is a bit too weak.

Advanced S.A.S. does not produce torque itself, it uses controllable components instead.

SAS/ASAS Parts

The game currently offers four SAS/ASAS units; a small radius SAS, a small radius ASAS, a large radius ASAS and an 'avionics package'. You also get some SAS functionality from command modules.

Dedicated Units

Image	Part	Radial size	Cost ()	Mass (t)	Max. Temp. (K)	Tolerance (m/s)	Tolerance (g)	Torque (kN·m)	Electricity (⚡/s)
	Small Inline Reaction Wheel	Tiny	600	0.05	2 000	9	50	5	0.25 (15 ⚡/min)
	Advanced Inline Stabilizer	Small	1 200	0.1	2 000	9	50	15	0.45 (27 ⚡/min)
	Advanced Reaction Wheel Module, Large	Large	2 100	0.2	2 000	9	50	30	0.6 (36 ⚡/min)