6.65 VI.8.5: Output by Active External Radiator: The ES group investigated two refrigerator circuits, the Brayton heat pump and the Rankine heat pump, as means to reduce the external radiator area. The overall power flow in the active power output system is schematized in Figure 6.27. Section VI.8.2 described the anticipated power inputs into the hull: Pinputsunlight Pinputoperations Pinputlifestyle 2.79xl0 7 watts 2.0xl0 6 watts 3.6xl0 6 watts and Pthermal to run the heat pump. These four power inputs had to be dissipated by the two power outputs: radiation from the hull through the shield,and radiation from the external radiator. As described in Section VI.8.3 and Appendix VI.F, the radiation from the hull through the shield was estimated at: Poutputhull + shield 8.6xlo 6 watts The external radiator would therefore have to radiate away: P = 2.49xl0 7 watts+ P outputrad thermal There were advantages and disadvantages to the active external radiator concept. Since, for a given power output, the area of a space radiator is proportional to the fourth power of its absolute temperature, the higher operating temperature of the active radiator could significantly reduce its area. However, the required power output would be greater due to the addition of Pthermal to the power inputs. The production of Pthermal would call for a larger
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