Small Inline Reaction Wheel
The S.A.S. Module is a toggleable module that acts as a sort of Autopilot to stabilize and help keep a rocket on course.
Contents
Description
| “ | SAS: Stability Augmentation System, Spin Auto-Stabilizer, Sickness Avoidance Solution. Whatever you choose to call it, it makes the ship stop spinning around. — O.M.B. Demolition Enterprises |
” |
Usage
S.A.S. modules do not have to be placed anywhere in particular to function, however it will cease to function if jettisoned. They appear to function on a stability:mass ratio and the effect can be enhanced by adding additional S.A.S. modules. Often a single S.A.S. module isn't enough. It is worth considering that they do add to the mass of your ship; if you require a lot of S.A.S. modules to get a large ship off the ground, you should think about distributing them such that they are dropped along with your earlier stages.
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.
- 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.
- 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.
The S.A.S module found within the command module itself uses 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.
Changes
- → See also: Version History
v0.11.0
- (undocumented) SAS now use angular momentum instead or angular velocity - takes into account inertia momentum of the ship [1]
v0.9
- (undocumented) Tweaked Kd, Ki and Kp parameters
v0.8.5
- Exposed Kd, Ki and Kp parameters for tuning the SAS module
v0.8
- SAS toggle with 'T' key
v0.7.3
- Initial Release
