Search Results

Advanced thermal management systems are one of the key technologies needed for future applications within the framework of the NASA Authorization Act 2005. This Act specifies that a programme shall be established to develop a sustained human presence on the Moon, including a robust pre-curser programme to promote exploration, science, commerce and US pre-eminence in space, and as a stepping stone to future exploration of Mars and other destinations. This paper will elucidate the development of two-phase thermal management systems for Moon and Mars applications, using data obtained from experiments with terrestrial scale-model systems, built according to the thermal-gravitational modelling and scaling laws (derived from dimension-analytical similarity considerations). It will include also important supporting issues, like the compilation of flow pattern maps at various gravity levels and writing down the constitutive heat and mass transfer equations for these maps.

Two mechanically pumped two-phase test rigs were built at NLR in order to experimentally study critical issues of spacecraft two-phase thermal management systems: a 5 kW, 31 mm ID, freon loop, focusing on the critical components of the ESA Two-Phase Heat Transport System. a 300 W, 4.93 mm ID, ammonia loop, to support the development of the ESA Capillary Pumped Loop Experiment (for the in-orbit demonstration of two-phase heat transport system technology) and to experimentally support two-phase thermal modelling and scaling activities. The rigs are described in detail. Typical test results are presented.

Discussed are some critical theoretical and experimental research issues to be investigated for candidate two-phase thermal control systems (and their components), to define what is to be done to develop reliable systems, for near and far future planetary applications envisaged. An earlier publication SAE-2007-01-3242 (“Design of planetary two-phase thermal control systems, using experimental data of terrestrial model systems, built according to thermal-gravitational modelling and scaling laws”), discussed that such advanced thermal control systems are one of the key technologies needed for future applications within the framework of the NASA Authorization Act 2005. This act specifies a programme to be established to develop sustained human presence on the Moon, including a robust pre-curser programme to promote exploration, science, commerce and US preeminence in space, also as a stepping stone to future exploration of Mars and other planetary destinations.

Condensers are crucial components of two-phase heat transport systems envisaged for future large spacecraft. To properly design such condensers, one uses experimental data, obtained from ground testing and reduced gravity aircraft and rocket flight testing, plus results of thermal modelling and scaling calculations. A frequently reported result of such activities, is that condensation lengths required in low-gravity environment exceed the corresponding lengths on earth (in horizontal ducts) up to one order of magnitude and more, while the accompanying pressure drops are almost the same.

Several publications describe research carried out at NLR on the thermal-gravitational modelling and scaling of two-phase heat transport systems for spacecraft applications. They dealt with mechanically and capillary pumped two-phase loops. The activities pertained to pure geometric, pure fluid to fluid, or hybrid scaling between a prototype system and a model at the same gravity level, and between a prototype in micro-gravity and a model on earth. Recent publications also include the scaling aspects of a prototype loop for a Moon or Mars base application and a terrestrial model. The work discussed here was carried out in the last couple of years. It concerns scaling to super-gravity levels, and was done because a promising super-gravity application for (two-phase) heat transport systems can be the cooling of high power electronics in spinning satellites and in military aircraft.