Reaction wheel
A reaction wheel provides torque to a craft and allows it to rotate in space with using only electric charge and is thus available as long as there is an electric power generator on board. Those were namely added in version 0.21 but a similar unnamed system was added previously.
The command modules listed in the table below have a reaction wheel and can provide torque. Adding additional parts utilising torque allows faster change in rotation. The placement does matter for reaction wheels. Generally speaking they can cause some problems if placed far from the center of mass. They function like grabbing the point where the reaction wheel is located and rotating around that point. The rotation will get anywhere other then near the center of mass.[1] All command pods and probe bodies provide reaction wheels, except the Probodobodyne OKTO2, Probodobodyne QBE, and Probodobodyne RoveMate.
To operate reaction wheels electric power needs to be available. The electric consumption is proportionate to its torque. While command modules that have reaction wheels need 0.1 E/s per kilonewton meter torque, all dedicated parts need at maximum 0.3 E/s but supplying 20 torque requiring only 0.015 E/s per kilonewton meter torque. For example the Command Pod Mk1 can generate torque up to 2.4 kNm per axis which requires up to 0.24 E/s or 0.1 E/(s·kN·m). The power usage is per axis so when the reaction wheel is applying maximum torque at two axes simultaneously it requires twice as much energy.
This is one of the key systems used by SAS.
Reaction wheels
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) |
Command Pods
| Image | Part | Radial size | Cost ( ) |
Mass (t) |
Max. Temp. (K) |
Tolerance (m/s) |
Tolerance (g) |
Torque (kN · m) |
S.A.S. level |
Required Crew/ Power |
Capacity (⚡) |
|---|---|---|---|---|---|---|---|---|---|---|---|
 |
Mk1 Cockpit | Small | 1 250 (1 241) |
1.28 (1.25) |
2 000 (1 100) |
40 | 50 | 10 |  [Note 1]
|
|
50 ⚡ 7.5  MP
|
 |
Mk1 Inline Cockpit | Small | 1 600 (1 591) |
1.03 (1.00) |
2 000 (1 100) |
40 | 50 | 10 | [Note 1]
|
|
50 ⚡ 7.5 MP
|
 |
Mk2 Cockpit | Mk2 | 3 500 (3 482) |
2.06 (2.00) |
2 500 (1 400) |
45 | 50 | 15 | [Note 1]
|
+
|
150 ⚡ 15 MP
|
 |
Mk2 Inline Cockpit | Mk2 | 3 500 (3 470) |
2.10 (2.00) |
2 500 (1 400) |
45 | 50 | 15 | [Note 1]
|
+
|
150 ⚡ 25 MP
|
 |
Mk3 Cockpit | Mk3, Small | 10 000 (9 880) |
3.90 (3.50) |
2 700 (1 500) |
50 | 50 | 40/40/20[Note 2] | [Note 1]
|
+
|
500 ⚡ 100 MP
|
 |
Mk1 Command Pod | Small, Tiny | 600 (588) |
0.84 (0.80) |
2 200 (1 200) |
14 | 50 | 5 | [Note 1]
|
|
50 ⚡ 10 MP
|
 |
Mk1-3 Command Pod | Large, Small | 3 800 (3 764) |
2.72 (2.60) |
2 400 (1 400) |
45 | 50 | 15 | [Note 1]
|
+
|
150 ⚡ 30 MP
|
 |
Mk1 Lander Can | Small | 1 500 (1 482) |
0.66 (0.60) |
2 000 (1 000) |
8 | 50 | 3 | [Note 1]
|
|
50 ⚡ 15 MP
|
 |
Mk2 Lander Can | Large | 3 250 (3 202) |
1.515 (1.355) |
2 000 (1 200) |
8 | 50 | 15 | [Note 1]
|
+
|
100 ⚡ 40 MP
|
 |
PPD-12 Cupola Module | Large, Small | 3 200 (3 188) |
1.80 (1.76) |
2 000 (1 000) |
8 | 50 | 9 | [Note 1]
|
|
200 ⚡ 10 MP
|
 |
Probodobodyne HECS | Tiny | 650 | 0.1 | 1 200 | 12 | 50 | 0.5 | 1 | 1.5 ⚡/min (90 ⚡/h) |
10 ⚡ |
 |
Probodobodyne OKTO | Tiny | 450 | 0.1 | 1 200 | 12 | 50 | 0.3 | 0 | 1.2 ⚡/min (72 ⚡/h) |
10 ⚡ |
 |
Probodobodyne HECS2 | Small | 7 500 | 0.2 | 2 000 | 8 | 50 | 10 | 3 | 3.0 ⚡/min (180 ⚡/h) |
1 000 ⚡ |
 |
RC-001S Remote Guidance Unit | Small | 2 250 | 0.1 | 2 000 | 9 | 50 | 0.5 | 3 | 3.0 ⚡/min (180 ⚡/h) |
15 ⚡ |
 |
RC-L01 Remote Guidance Unit | Large | 3 400 | 0.5 | 2 000 | 9 | 50 | 1.5 | 3 | 4.8 ⚡/min (288 ⚡/h) |
30 ⚡ |
 |
MK2 Drone Core | Mk2 | 2 700 | 0.2 | 2 500 | 20 | 50 | 15/3/3[Note 2] | 3 | 3.0 ⚡/min (180 ⚡/h) |
250 ⚡ |
 |
MPO Probe | Small | 9 900 (9 854) |
0.895 (0.395) |
2 200 | 9 | 50 | 6 | 3 | 3.0 ⚡/min (180 ⚡/h) |
1 000 ⚡ 45 LF55 O
|
 |
MTM Stage | Small | 21 500 (6 300) |
0.795 (0.415) |
2 200 | 12 | 50 | 12 | 2 | 1.8 ⚡/min (108 ⚡/h) |
4 000 ⚡ 3 800  XE
|
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 In the "Career" mode in manned command modules, the performance and functionality of the SAS is determined by the presence of at least one kerbonaut with the specialization "Pilot" and the level of his specialization. In the "Science" and "Sandbox" modes, a kerbonaut with any specialization can use all the functionality of the SAS on board the manned command module without restrictions.
- ↑ 2.0 2.1 Torque differs between axes. These numbers are for pitch/yaw/roll respectively.
Notes
- ↑ Answer from C7 in his blog entry “Updated Information on SAS in 0.21.1”
