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After the launch to the International Space Station with The Space Shuttle flight STS 118 13A.1 on August 9th 2007 and the accommodation in the US lab Destiny, the air quality monitor ANITA (Analyzing Interferometer for Ambient Air) has been successfully put into operation. ANITA is a technology demonstrator flight experiment being able to continuously monitor with high time resolution the air conditions within the crewed cabins of the ISS (International Space Station). The system has its origin in a long term ESA (European Space Agency) technology development program. The ANITA mission itself is an ESA-NASA cooperative project. ESA is responsible for the provision of the HW (Hardware), the data acquisition and data evaluation. NASA's responsibilities are launch, accommodation in the US Lab Destiny, operation and data download.

After the launch to the ISS (International Space Station) with The Space Shuttle flight STS 118 13A.1 on August 9th 2007 and the accommodation in the US lab Destiny, the air quality monitor ANITA (Analysing Interferometer for Ambient Air) has been successfully put into operation. ANITA is a technology demonstrator flight experiment being able to continuously monitor with high time resolution the air conditions within the crewed cabins of the ISS. The system has its origin in a long term ESA technology development programme. The ANITA mission itself is an ESA-NASA cooperative project. ESA is responsible for the provision of the HW, the data acquisition and data evaluation. NASA's responsibilities are launch, accommodation in the US Lab Destiny, operation and data download. The ANITA air analyser is currently calibrated to detect and quantify online and with high time resolution 33 gases simultaneously with down to sub-ppm detection limits.

After 11 months of successful operation onboard the ISS US laboratory Destiny, the air quality monitors ANITA (Analyzing Interferometer for Ambient Air) was brought back to Earth on STS126 (ULF2). ANITA is a technology demonstrator flight experiment for continuous air quality monitoring inside the crewed cabin of the ISS with low detection limits and high time resolution. For the first time, the dynamics of the detected trace gas concentrations could be directly resolved by ANITA and correlated to gas events in the cabin. The system is the result of a long term ESA technology development programme initiated more than seventeen years ago. The ANITA mission was a cooperative project between ESA and NASA. ESA's responsibilities were the provision of the H/W, the data acquisition and the data evaluation. NASA was responsible for the launch, accommodation and operation onboard ISS, data download and the transportation of ANITA back to the Earth.

After a general introduction on two-phase thermal control system issues, the paper reviews the status of and lists commonalities and differences between the only two currently developed aerospace-related mechanically pumped two-phase thermal control systems. These are the Russian Segment Active Thermal Control System (RSATCS) hybrid two-phase ammonia thermal control system for the Russian segment of the International Space Station ISS, and the Tracker Thermal Control System (TTCS) hybrid two-phase carbon dioxide thermal control loop for the AMS-2 attached ISS payload.

As it is not possible to directly use commercial liquid flow meters in spacecraft fluid loops, a study was carried out for the European Space Agency to adapt commercial flow meter assemblies for space applications. The various activities (described in detail) eventually led to the selection of two commercial units, which were redesigned/adapted to be used in spacecraft single-phase (water) and two-phase (ammonia) thermal control loops. These flow meter assemblies were tested according to an agreed test programme, that included performance and calibration tests in a test bench (developed during the study), vibration testing and EMC/EMI testing. The results are discussed in order to assess to what extent the study objectives were met. Recommendations for future work are given also.

The Alpha Magnetic Spectrometer AMS-2 is planned for a five years mission as attached payload on ISS, the International Space Station. It is an international experiment searching for anti-matter, dark matter, and missing matter. AMS-2, an improved version of AMS-1 flown on STS 91, consists of various particle detector systems, one of these being the (Silicon) Tracker. The trade-off based choice and the experimental feasibility demonstration of a mechanically pumped two-phase CO2 cooling loop for the Tracker is discussed in detail. The current status and ongoing and planned development activities are discussed.

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.

Heat pipes are simple, reliable, light-weight and highly efficient components for thermal control and protection, which will find growing interest in the context of manned space flights and future space stations. Despite extensive testing requirements for satellite heat pipes, the crucial data on their zero-g behaviour can only be obtained on actual space flights. For this reason a heat pipe test platform was flown twice on a retrievable satellite (SPAS-01) on board Space Shuttle. Among various other heat pipes, two standard IKE constant-conductance heat pipes and a heat pipe diode based on the liquid trap principle were tested on this platform. The paper compares ground test data and flight data from the first and second flight. The power profile in the second flight was slightly changed in order to gain additional information about heat pipe behaviour under zero-g.

Mechanically pumped two-phase heat transport systems are currently developed to meet the high power and long transport distance requirements of thermal management systems for future large spacecraft. Capillary pumped systems are being developed for applications with special requirements concerning microgravity disturbance level, temperature stability and controllability. As two-phase flow and heat transfer in a low-gravity environment is expected to differ from terrestrial behaviour, two-phase heat transport system technology has to be demonstrated in orbit. Therefore the Dutch-Belgian Two-Phase eXperiment TPX has been developed within the ESA In-Orbit Technology Demonstration Programme. TPX is a two-phase ammonia system, flown in the 5ft3 gaseous nitrogen filled Get Away Special canister G557, aboard STS-60.

Mechanically and capillary pumped two-phase heat transport systems are currently developed to meet the high power and long transport distance requirements of thermal management systems for future spacecraft. Compared to existing single-phase systems, two-phase loops offer important advantages: reduced overall mass and pumping power consumption, virtually isothermal behaviour, adjustable working temperature, insensitivity to variations in heat load and sink temperature, and high flexibility with respect to the location of heat sources within the loop. As two-phase flow and heat transfer in low-gravity environment is expected to (considerably) differ from terrestrial behaviour, the technology of two-phase heat transport systems and their components is to be demonstrated in orbit. Therefore a Dutch-Belgian Two-Phase experiment has been developed within the ESA In-Orbit Technology Demonstration Programme.

The paper deals with heat and mass transfer research issues related to the development of spacecraft active thermal control systems, more specifically development of two-phase heat transport system technology. It focuses on design and development supporting theoretical work: the thermal/gravitational scaling of two-phase heat transport systems, including the aspects of gravity level dependent two-phase flow pattern mapping and condensation.

Two-phase heat transport systems are currently considered for the thermal management of future large power spacecraft. The monitoring of the quality, being the relative vapour mass content, of the two-phase mixture at various locations in the system, is valuable - possibly indispensable - for the proper operation of such a system. This paper reviews concepts for quality monitoring. Only a few concepts turn out to be suitable for spacecraft applications. Promising concepts are based on the capacitance, sonic velocity and index of refraction. These concepts are described and quantitatively analyzed. Applicability, advantages, restrictions and some hardware aspects are discussed.

Mechanically and capillary pumped two-phase heat transport systems are currently developed to meet the high power and long transport distance requirements of thermal management systems for future spacecraft. As two-phase flow and heat transfer in a low-gravity environment is expected to (considerably) differ from terrestrial behaviour, the technology of two-phase heat transport systems and their components has to be demonstrated in orbit. Therefore a Dutch-Belgian two-phase experiment (TPX) is being developed within the ESA In-Orbit Technology Demonstration Programme TDP1. TPX concerns a two-phase ammonia system in the (5ft3, gaseous nitrogen filled) Get Away Special canister G-557. The system is a downscaled capillary pumped two-phase loop. It includes downscaled versions of mechanically pumped two-phase loop components: multichannel condensers and vapour quality sensors (plus a controllable 3-way valve for control exercises). The Critical Design Review status of TPX is discussed.

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.

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.

Aspects of the gravitational scaling of spacecraft two-phase heat transport systems are discussed. Supporting similitude considerations, based on dimension analysis, and useful equations and correlations are given.

Based on the thermal requirements of future large European platforms such as the Columbus Space Station, several developments in the field of two-phase flow systems were initiated over the last few years in Europe. This paper will give a general overview of the objectives, development status and test results of an ESA-funded ‘Two-phase heat transport system’ study and of two studies sponsored by the German Ministry of Research and Technology on two-phase heat transport. The ESA two-phase loop system resulting from the concept trade-off is driven by an electrically powered liquid pump and is provided with a capillary cold plate and an evaporative heat exchanger mounted in parallel. Under certain conditions, a simplified version of this type of system is able to work in a capillary-pumped mode. The system is designed for a heat load of 10-20 KW, a length of 20 m, a working temperature around 20°C and R114 as working fluid.