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→Heat Pipes
* Damper
Dampers help in dissipation of vibration energy into heat energy. A PVI system can be simplified with the system shown in the figure below:
[[File:PVI1.png|frame|center|Passive Vibration Isolation. Image reproduced from [https://commons.wikimedia.org/wiki/File:Passvib1.svg here]]]
==== Transmissibility Curve <ref name = "ref2">https://en.wikipedia.org/wiki/Vibration_isolation</ref> ====
=== Active Vibration Isolation (AVI) System <ref name = "ref2" /> ===
It can be modeled as spring along with a feedback circuit which consists of a sensor , a controller, and an actuator. The acceleration (vibration) signal is processed by a control circuit and amplifier. Then it feeds the electromagnetic actuator, which amplifies the signal. As a result of such a feedback system, a considerably stronger suppression of vibrations is achieved compared to ordinary damping.
==== Sensors for Active Isolation ====
==== Multi-layer Insulation (MLI) ====
Protects the spacecraft from excessive solar rays. Acts as a radiation barrier.
[[File:PTC1.png|frame|center|Illustration of the working of MLI]]
==== Coatings ====
q(space)= q(loses) + q(electric)
[[File:PTC2.png|frame|center|Radiator illustration]]
=== Active Thermal Control (ATC) system ===
*Flat sheet heaters use the Joule effect
[[File:PTC3.png|frame|center| Patch heater]]
==== Louvers ====
*Shield radiator surfaces to moderate heat flow to space
* '''Principle:''' Bi-metallic spring sense the radiator temperature, open/close the radiator to deep space.
[[File:LoversATC3.png|framethumb|center| 600px| Louver mechanism. Image reproduced inspired from [http://www.tak2000.com/data/satellite_tc.pdf here]]]
====Heat Pipes====
*Wicking material returns fluid to hot end
*Provide high heat transfer rates even with small temperature differences
[[File:ATC1.png|frame|center|Heat Pipe Mechanism. Image reproduced from [https://commons.wikimedia.org/wiki/File:Heat_Pipe_Mechanism.png here]]]
===Comparison of Passive and Active Thermal Control ===