Design
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Astro | Propulsion
| Power | Thermal
| Structures | AD&C
| CDHS |
Test
These
definitions describe transfer of energy
from
a heat source to a fluid or solid and material radiation
properties. Engineers use them to characterize and
design thermal control systems.
Heat Transfer
Convection
is the transmission of heat
into a liquid or gas as it flows over a heat source.
Conduction
is the transmission of heat
into a solid as the object contacts a heat source.
Radiation
is the transmission of energy through space. Satellites
are exposed to radiation from the Sun and Earth.
The Earth reflects sunlight and emits absorbed radiation
as infrared energy.
Reflectivity
(r)
is a material's ability to throw back, or reflect,
radiation that strikes its surface.
Absorptivity
(a)
is a material's ability to
take in, or absorb, radiation that strikes its surface.
Transmissivity
(t)
is a material's ability to pass through, or transmit,
radiation that strikes its surface. These properties
are interrelated through the conservation of energy,
r + a + t = 1.
Emissivity
is an object's ability to give off, or emit, absorbed
radiation from its surface. A black body radiator
emissivity equals one.
Albedo
is the energy from sunlight
reflected off the Earth. Approximately 30% of the
direct solar energy on a satellite comes from this
source.
