Reaction wheel

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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.

All command modules except the EAS-1 External Command Seat 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]

To operate reaction wheels electric power needs to be available. The electric consumption is proportionate to its torque. While command modules, except Probodobodyne OKTO2, needs 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
(Funds)
Mass
(t)
Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
Torque
(kN·m)
Electricity
(⚡/s)
Inline reaction wheel.png
Small Inline Reaction Wheel Tiny 600 0.05 2 000 9 50 5 0.25
(15 ⚡/min)
Inline advanced stabilizer.png
Advanced Inline Stabilizer Small 1 200 0.1 2 000 9 50 15 0.45
(27 ⚡/min)
ASAS large.png
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
(Funds)
Mass
(t)
Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
Torque
(kN · m)
S.A.S.
level
Required Crew/
Power
Capacity
(⚡)
MK1COCKPIT.png
Mk1 Cockpit Small 1 250
(1 241)
1.28
(1.25)
2 000
(1 100)
40 50 10 Crew Crew 50 ⚡
7.5 Units of fuel MP
Mk1 Inline Cockpit.png
Mk1 Inline Cockpit Small 1 600
(1 591)
1.03
(1.00)
2 000
(1 100)
40 50 10 Crew Crew 50 ⚡
7.5 Units of fuel MP
Mk2 Cockpit.png
Mk2 Cockpit Mk2 3 500
(3 482)
2.06
(2.00)
2 500
(1 400)
45 50 15 Crew Crew + Crew 150 ⚡
15 Units of fuel MP
Mk2 InlineCockpit.png
Mk2 Inline Cockpit Mk2 3 500
(3 470)
2.10
(2.00)
2 500
(1 400)
45 50 15 Crew Crew + Crew 150 ⚡
25 Units of fuel MP
Mk3 Cockpit.png
Mk3 Cockpit Mk3, Small 10 000
(9 880)
3.90
(3.50)
2 700
(1 500)
50 50 40/40/20[Note 1] Crew Crew + CrewCrewCrew 500 ⚡
100 Units of fuel MP
Mk1CommandPod Dark.png
Mk1 Command Pod Small, Tiny 600
(588)
0.84
(0.80)
2 200
(1 200)
14 50 5 Crew Crew 50 ⚡
10 Units of fuel MP
Mk1-3CommandPod.png
Mk1-3 Command Pod Large, Small 3 800
(3 764)
2.72
(2.60)
2 400
(1 400)
45 50 15 Crew Crew + CrewCrew 150 ⚡
30 Units of fuel MP
LanderCanMK1.png
Mk1 Lander Can Small 1 500
(1 482)
0.66
(0.60)
2 000
(1 000)
8 50 3 Crew Crew 50 ⚡
15 Units of fuel MP
Mk2canN.png
Mk2 Lander Can Large 3 250
(3 202)
1.515
(1.355)
2 000
(1 200)
8 50 15 Crew Crew + Crew 100 ⚡
40 Units of fuel MP
Cupola.PNG
PPD-12 Cupola Module Large, Small 3 200
(3 188)
1.80
(1.76)
2 000
(1 000)
8 50 9 Crew Crew 200 ⚡
10 Units of fuel MP
HECS.png
Probodobodyne HECS Tiny 650 0.1 1 200 12 50 0.5 1 1.5 ⚡/min
(90 ⚡/h)
10 ⚡
OKTO.png
Probodobodyne OKTO Tiny 450 0.1 1 200 12 50 0.3 0 1.2 ⚡/min
(72 ⚡/h)
10 ⚡
HECS2.png
Probodobodyne HECS2 Small 7 500 0.2 2 000 8 50 10 3 3.0 ⚡/min
(180 ⚡/h)
1 000 ⚡
Probestack.png
RC-001S Remote Guidance Unit Small 2 250 0.1 2 000 9 50 0.5 3 3.0 ⚡/min
(180 ⚡/h)
15 ⚡
Probehuge.png
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.png
MK2 Drone Core Mk2 2 700 0.2 2 500 20 50 15/3/3[Note 1] 3 3.0 ⚡/min
(180 ⚡/h)
250 ⚡
  1. 1.0 1.1 Torque differs between axes. These numbers are for pitch/yaw/roll respectively.


Notes

  1. Answer from C7 in his blog entry “Updated Information on SAS in 0.21.1