Speaker
Description
Exploration missions have to cope with stringent reliability requirements, large thermal rejection needs and complex attitude with respect to sun orientation. The common solution for large dissipation systems is a single mono-phasic Mechanical Pumped Loop (MPL) running from the cabin/equipment to external piping lined radiators. These systems face redundancy and reliability issues due to their sensitivity to Micrometeoroids and Orbital Debris (MMOD), where a single impact hole will lead to the risk of losing the entire loop. These issues are then exacerbated when extended to long-term duration exploration missions and outposts. This study aims to develop hardware technology capable of interfacing with standard fluid loop thermal control systems, improving the reliability of the architecture and improving the performance with a two-stage heat transport system. By keeping a crew-safe fluid in the MPL primary loop, avoiding direct exposure to space, this addition of a novel high-performance heat exchanger with integrated Heat-Pipe evaporators, ensures a safe method of spreading heat along MMOD exposed radiator surfaces.
Mechanical Pumped Loop and Loop Heat Pipes are widely used in space application to collect the heat inside a spacecraft and transfer it to external radiators. As presented in the first Figure, the radiators used for MPLs are based on panels with the condenser lines embedded (or surface mounted) and snaking throughout the radiator surface to enable complete coverage. This approach leads to a significant surface of the loop exposed to the external environment, increasing the risk of micrometeoroid and debris induced damage, and lowering the overall reliability of the radiators, especially for very long missions. This risk is be reduced using the proposed configuration of the radiators, with a Compact Heat Exchanger used to transfer the heat from the cooling line to a network of heat pipes used to spread the heat uniformly over the radiator surface. In this case, a possible impact with a micrometeoroid would lead to the failure of only a single heat pipe reducing performance of the system but a small amount but ensuring the function of the overall radiator system.
The design of this 3D printed hybrid heat exchanger has been narrowed down from a variety of different design concepts. The final design is the result of compromises between performance, manufacturability, design compactness, ease of integration and equality in nominal/ redundant line pressure drops. This design also incorporates lessons learned from manufacturing and test results on coupons which enabled the derisking of certain processes (orbital welding between ALM part and extruded aluminum HP) and establish backup solutions.
The test realised on this Breadboard have done successfully (pressure cycling, thermal performance). Generally, the power evacuated increases with the thermal gradient ΔT = Tinlet – Tsink (2,9 kW has been achieved with ΔT = 55°C) which is a 45% higher than the specified evacuated power from MPL system.
