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When the low-flow engine cooling system was developed, besides the addition of a two-pass radiator, another important design change was the replacement of the conventional single valve thermostat with a dual-valve thermostat. This new thermostat was believed to offer better control of coolant temperatures and provide better engine cooling system responses. The present study is to understand the thermal characters of the dual-valve thermostat and its effect on the performance of a low-flow engine cooling system. By developing a computational thermostat model for use with the VECSS Simulation Code, several computational experiments were conducted to compare the dynamic performance of a low-flow cooling system fitted with different thermostats.

When permanent bases are established on the moon, various methods may be employed to reject the heat generated by the base. One proposed concept is the use of a vertical thermal radiator operating with a parabolic shade. The shade reduces background environmental heating by several means, thereby, increasing the performance of the radiator. Specifically, the shade focuses the incoming solar radiation in a line above the radiator and through the use of thermal control coatings substantially reduces infrared radiation originating from the lunar surface. To further enhance the performance of the radiator, it is aligned with the moon's equator. Several different parabolic shade geometries were evaluated using the Thermal Synthesizer System (TSS) which allows the full spectrum of specular surfaces to be included in the modeling process.

Several factors are important in the development of active thermal control systems for planetary habitats. Low system mass and power usage as well as high reliability are key requirements. Ease of packaging and deployment on the planet surface are also important. In the case of a lunar base near the equator, these requirements become even more challenging because of the severe thermal environment. One technology that could be part of the thermal control system to help meet these requirements is a radiator shade. Radiator shades enhance direct radiative heat rejection to space by blocking solar or infrared radiation which lessens the performance of the radiator. Initial development work, both numerical and experimental, has been done at the Johnson Space Center (JSC) in order to prove the concept. Studies have shown that heat rejection system mass may be reduced by 50% compared to an unshaded low-absorptivity radiator.

When permanent bases are established on the moon, various methods may be employed to reject the heat generated by the base. One proposed concept is the use of a heat pump operating with a vertical, flow-through thermal radiator which is mounted on a Space Station type habitation module. Since the temperature of the lunar surface varies over the lunar day, the sink temperature for heat pump heat rejection will vary. As a result, the heat pump power demand will also vary over the lunar day. This variable power requirement could be provided by a fixed horizontal solar photovoltaic (PV) array placed on the lunar surface, since its power production will vary sinusoidally with the time of day. Using a dedicated PV array to power the heat pump may represent a favorable mass trade-off compared to enlarging the size of the base's central power grid due to power system simplification and improvements in efficiency.

Many studies have been conducted to develop a thermal control system that can operate under the extreme thermal environments found on the lunar surface. While these proposed heat rejection systems use different methods to reject heat, each system contains a similar component, a thermal radiator system. These studies have always considered pristine thermal control system components and have overlooked the possible deleterious effects of lunar dust contamination. Since lunar dust has a high emissivity and absorptivity (greater than 0.9) and is opaque, dust accumulation on a surface should radically alter its optical properties and therefore alter its thermal response compared ideal conditions. In addition, the non-specular nature of the dust particles will may alter the performance of systems that employ specular surfaces to enhance heat rejection. To date, few studies have examined the effect of dust deposit on thermal control system components.