3D-printed pipe segment with integrated heater and sensor

Telecommunications satellites are usually placed in geostationary Earth orbit, a circular orbit 35,786 kilometers above the equator, following the direction of Earth's rotation. In this harsh environment, robustness, reliability and longevity of operational systems are essential. To prevent onboard devices from overheating in the sun or freezing in the shadow, the satellite may be equipped with a Mechanically Pumped Loop (MPL) for thermal management. CSEM, Lisi Aerospace Additive Manufacturing, and Thales Alenia Space France have co-developed an ingenious technology brick as part of the AHEAD project (Advanced Heat Exchange Devices). The result is a 3D printed pipe segment that can heat the fluid in the MPL and measure its temperature. With its built-in electrical connector and precise fluidic interfaces, the pipe makes the integration much easier compared to conventionally bonded film heaters and temperature sensors.

Optimizing thermal regulation performance by heating and monitoring 

Designed for temperatures ranging from -65 °C to +85 °C, the stainless-steel element can withstand high payloads. In the Thales Alenia Space use case, the MPL contains pressurized ammonia of 48 bars, absorbing heat at hot spots and transfers it to cold spots. To ensure continuous operation, ammonia must not get too cold. It is therefore heated locally while its temperature is constantly monitored. 

Value creation for your products

Additive manufacturing challenges, extensive testing 

Due to the small gaps between the structure and wires, laser powder bed fusion had to be highly precise. The challenge was to make these gaps not too narrow, because this could lead to material fusion, and not too large, since that would affect the heat transfer from the wires to the pipe’s inner side. “In addition to that, the wires were challenging to print as well because they are long and have a very thin diameter of 0.4 millimeters,” notes Hervé Saudan. Another demanding issue concerned the powder removal after printing, to ensure that no left-over powder material remains in the narrow caves. 

After extensive tests in a real satellite thermal management system at Thales Alenia Space, the heating function of the prototypes fulfilled all requirements. It showed no defects after vibration, pressure, and burst tests (withstanding 1225 bars) as well as thermo-elastic lifetime tests simulating 15 years in space. 

Unfortunately, the metrological performance of the Aerosol Jet Printed temperature sensor did not meet expectations. Nevertheless, the printed sensor can be replaced by an already-qualified commercial sensor in a future version of the prototype. The fact that the sensor connection wires, and output connector are already integrated into the pipe means that the benefits are retained, whatever sensor technology is used. 

Targeting refrigeration systems on Earth and 3D-printed electronics 

With the advantage of built-in wires and connectors, this use case paves the way to other heating and in-situ sensing applications. “We have several running projects but at this time I’m afraid they remain confidential,” Hervé Saudan confides. 

In a second use case, the pipe segment was equipped with a standard temperature sensor and integrated in a particle detector refrigeration system at CERN, Geneva. For such CO2-based refrigeration systems of the newest generation, CSEM’s innovation allows harvesting measurement data at strategic locations, which contributes to improving their performance. 

Whether for warming or cooling, the CSEM consortium now wants to bring its innovation to life in the machine, medical, life sciences, food and chemical industries.