Abstract
This paper is dedicated to the characterisation of charging behaviour of space used polymers in space electron environment. Spacecrafts are indeed submitted in Medium Earth Orbit (MEO) to severe fluxes of electrons with energies ranging from a few keV to several MeV. For qualification of materials used on satellites and the prediction of their electrostatic behaviour in space environment, it is therefore important to tests these materials in representative environment. These experiments have been carried out at ONERA, The French Aerospace Lab (Toulouse, France) in the SIRENE facility. Different polymers (PEEK, ETFE, Kapton®, polyurethane and silicone varnish, polyurethane based paint) have been characterised to extract the main electric parameter that steer their charging behaviour in space environment: the radiation induced conductivity (RIC). These materials have then been tested in representative environment so as to study the evolution of their conductivity and charging behaviour as a function of the received radiation dose (for low and high dose levels). From these experiments, it was possible to extract the physical parameters that steer RIC and assess numerically their charging levels in specific MEO environment.
Highlights
Materials used on spacecraft have to cope with strong level of electron and protons fluxes
We can notice on this figure that all materials gets charged under 20 keV electron beam except for the Polyurethane PU paint that do not present any charging level at all, meaning that its bulk intrinsic conductivity is higher than 10−12 Ω−1 m−1
These results show the importance to take into account effect of radiation dose and electric field on charge transport and ionisation processes for a correct prediction of charging kinetics in space environment
Summary
Materials used on spacecraft have to cope with strong level of electron and protons fluxes. The high energy particles can come through the first external surfaces to get implanted within the inner dielectric parts of the spacecraft (see Fig. 1) This irradiation process induces internal electric charging on the insulating and dielectric parts of the spacecraft, with potentially high charging kinetics (if strong electron fluxes are met, like in MEO [Medium Earth Orbit] environment for instance for GPS [Global Positioning System], GLONASS [Global Navigation Satellite System] or Galileo spacecrafts) [1,2]. Successive irradiations can present different profiles depending on DRIC relaxation kinetics: for Teflon® FEP, for instance, DRIC fades away quite quickly This quick decline does not induce total recovery: electron trapped during previous irradiations act as recombination centers for the following irradiations, leading to a decrease of the effective generation rate and to a decline of RIC [12]. The physical model used for charging prediction will be presented followed by a validation and the use of this model for charging prediction of PEEK in averaged MEO conditions
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