thermal design Flashcards
why is thermal design important?
without thermal control, components would overheat or overcool, making for inefficient operation
define conduction
molecular excitation
define convection
heat transport by fluid mixing
define radiation
EM wave emission
fill the missing word: in high vacuum, heat can only be transferred to or from the spacecraft via ________
EM radiation
define direct solar radiation
can be approximated to a parallel beam of light
define albedo radiation
direct solar radiation reflected by nearby planets
define earth shine
thermal radiation radiated by every planet
what must be true for a system in thermal equilibrium?
what is absorbed is equal to what is emitted
list the features of white, gold and grey paint
- white: highly absorbent in IR and highly reflective in visible part
- gold: not good absorber of visible and IR parts, good material to use for thermal insulation coatings
- grey: totally absorbing, used in passive thermal control
define view factor
fraction of radiation leaving surface 1 that is intercepted by surface 2
what needs to be considered for circular non-co-planar orbits?
planetary position and angle the orbit plane makes with earth-sun vector
what is true in non-circular non-co-planar orbits?
- view factors change around the orbit
- projected areas change around the orbit
define thermal cycle
behaviour of spacecraft temperature over time as spacecraft passes between direct solar and eclipse conditions in the orbit