Progress MS-08 to test experimental space radiator
One distinctive feature of the Progress MS-08 cargo ship is the presence of three pairs of white rectangular panels attached to the exterior of the refueling section on the spacecraft. They are radiators of the Phasoperekhod ("phase transfer") LEU-TT-1 experiment testing so-called heat pipes, which might help to improve prospective light-weight thermal control systems.
Progress MS-08 spacecraft with Phasoperekhod panels attached to its middle section.
Known specifications of the Phasoperekhod experiment:
The thermal-control system is intended to prevent overheating of equipment inside pressurized and unpressurized spacecraft compartments. One popular method to do that is to circulate ammonia through a network of the so-called heat pipes. Ammonia has very low thermal resistance and, as a result, can serve as an ideal medium to remove heat and radiate it into space. During the operation of the heat pipe system, the radiator fluid heats up inside the pipe and evaporates, carrying the heat to the cold section of the pipe, where the vapor condensates, and the fluid then returns to the heating zone via a special capillary system.
Although radiator systems of this type have been operating in space for decades, authors of the Phasoperekhod experiment at RKK Energia and Keldysh Center stressed the absence of detailed and systematic data about the influence of weightlessness on the parameters and specifications of such hardware and the lack of information about the maximum life span of these systems.
The authors of the Phasoperekhod experiment wanted to see how microgravity conditions in orbit would affect the ability of ammonia to remove heat via the radiator's heat pipes in long-duration flights. The careful monitoring of the process with a network of sensors could help engineers to develop a system with minimum mass, the authors of the experiment said.
The experiment aboard the Progress MS-08 included six 2-kilogram radiator panels with a heat pipe, six electric heaters and eight temperature sensors spread along the length of each pipe and capable of recording temperature from minus 50 to plus 80 degrees C. The heat pipe contains no more than 20 grams of heat-carrying ammonia. An electronics unit controlling the experiment was installed inside the pressurized cargo section of the Progress MS-08 spacecraft and wired to the radiator panels via cables.
The cosmonauts onboard the station can activate the experiment by pressing buttons on the electronics box inside the Progress. The experiment then runs according to a pre-programmed sequence and records its data to a removable flash memory card. At the end of each experimental session, the generated data can be downlinked to mission control. Each session should not exceed three hours. Each day, mission control is expected to request no more than two sessions separated by no less than a three-hour break. The goal is to log up to 50 sessions within the experiment.
The authors projected that Phasoperekhod would generate up to 35 megabytes of data in each session and the total data harvest would not exceed 1,000 megabytes during the entire study.
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Progress MS-08 spacecraft is being prepared for its integration with launch vehicle adapter on Feb. 5, 2018. Click to enlarge. Credit: RKK Energia