text: Spacecraft waste heat is ultimately rejected to space by radiator surfaces. Radiators can be of different forms, such as spacecraft structural panels, flat-plate radiators mounted to the side of the spacecraft, panels deployed after the spacecraft is on orbit, and droplets. 
  All radiators reject heat by infrared (IR) radiation from their surfaces. The radiating power depends on the surface's emittance and temperature. 
  The radiator must reject both the spacecraft waste heat plus any radiant-heat loads from the environment or other spacecraft surfaces.
  Most radiators are therefore given surface finishes with high IR emittance ( > 0.8) to maximize heat rejection and low solar absorption ( < 0.2) to limit heat loads from the sun. 
  High-temperature radiators are preferred for better efficiency and size reduction considerations, however, fluid property and droplet cloud property are additional factors.
  Droplet size formation and droplet density govern emission and reabsorption. 
  A smaller droplet is essential for obtaining effective radiation in the liquid droplet radiator. A droplet with a diameter of 1 μm has been calculated to cool from 500 K to 252 K in two seconds. A dense cloud of the droplet sheet will retard the cooling rate of the droplets because of the reabsorption of the emitted light.
  A single droplet radiates heat as it travels through space and at any time this heat loss is given by:
  where  is the Stefan–Boltzmann constant, 
   is the droplet heat loss rate to space (joules/second), 
   is the droplet radius (meters), 
   is the average gray body view factor for droplet at stream center (less than one), and 
   is the absolute droplet temperature at any time (kelvin).
  This equation models the droplet as a gray body with
  constant average emissivity. The instantaneous radiation
  rate is equal to the rate of energy loss resulting in this
  equation:
  where  is the specific heat capacity, 
   is the density of droplet (kg/m), 
   is the droplet transit time (seconds).