Internal Electrostatic Discharge Testing of Polyimide Film Heaters in a Jovian Radiation Environment

The internal charging behavior of Fralock FR10445 polyimide film heaters was investigated for NASA’s Europa Clipper mission. Radiation transport simulations were performed to calculate the expected charge deposition in the heater dielectrics for a heater adhered to the spacecraft structure during flyby of Europa. Simulations were performed for several shielding configurations of the heater (different numbers of layers of copper tape). Further simulations were performed to determine what electron beam energy and flux would reproduce the same charge deposition in the heaters when placed inside the JPL Dynamitron electron beam facility. The heaters were cooled to the minimum expected flight temperature of -115 °C and the leads of the heaters were terminated with 50 Ω resistors and monitored for discharge pulses. It was found that a heater with one layer of copper tape shielding produced discharges compatible with Human Body Model (HBM) Class 1B electronics. Heaters with two layers of copper tape produced discharges compatible with HBM Class 1A electronics. During the test, a hookup wire wrapped in copper tape was run over the top of the heaters in order to investigate coupling of discharge pulses from the discharge site to a nearby shielded wire. No significant coupling was observed from the source of the discharge to the wire.