High Voltage Power Supply Circuit Failure due to Hollow Core Resistor

On two simultaneous sounding rocket missions, science instrument high voltage power supplies experienced in-flight failure. A subsequent investigation discovered that the OHMITE Maxi-Mox series resistors in the power supply circuitry have a hollow core, which, during the rapid ascent of the sounding rocket, did not have sufficient time to properly vent. This resulted in coronal arcing in the resistor and subsequent failure of the power supply’s feedback op-amp. It is recommended that hollow core resistors only be used in situations where they are given sufficient time to reach vacuum prior to high voltage being applied.

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