Main results achieved

The project explored a variety of solutions and produced hundreds of samples in different configurations. In the end, it converged on a so-called Configuration A which was used to build seven larger-area demonstrators 100 mm x 100 mm on Kapton® Polyimide film. Samples were characterized and tested extensively in terms of properties at BoL and resistance to ageing and manipulations.

Large area demonstrator – about 100×100 mm

Results were as follows:

  1. α = 0.24 ± 0.02 (as expected);
  2. εHOT = 0.77 ± 0.03 (as expected);
  3. Δε = 0.32 ± 0.02 (low);
  4. TMIT = 27°C (as expected);
  5. ΔTMIT = 26°C (as expected);
  6. Rs > 1E12 Ohm/square (high);
  7. Substrate: Kapton FPC 3 MIL (as expected);
  8. Size of demonstrators: 100 mm x 100 mm (as expected);
  9. T.O. durability: properties stable after TVAC and p+, effects of UV not tested (partially as expected);
  10. Mechanical durability: Adhesion good after cutting, bending, humidity and TVAC (as expected).

Results are in good alignment with the expected values, apart from three deviations. Two deviations (high Rs, no UV testing) are the effect of partial budget reallocation from integration and testing activities to development activities. The third, Δε ≈ 0.3, is the effect of a non-optimal choice of materials.

Results were shared with the thermal engineers of major system integrators and were very well received. In particular, it was observed that, without improvements, the technology could already be of interest for applications in which the radiator sees the sun only at a grazing angle. In the general case, the T.O. performance still needs some improvement, but efforts should be directed more to lower α below 0.2 than to raising Δε. In fact, Δε = 0.3 is already good enough as it generates about 40% saving in the heating power budget for the cold case, compared to a standard coating ε = 0.8.

Surface at the optical microscope

The Smart-Flex Consortium has already outlined an evolution plan to improve the technology further and identified the topics on which the R&D efforts should be focused. Furthermore, in line with major integrators’ recommendations,  the Consortium is already planning new ageing tests on existing samples, from UV tests to tests in space.