Description
Objective:
The objective of the activity is to allow Power Processing Unit (PPU) switch on as quickly as possible after spacecraft separation.
Targeted Improvements:
To avoid long drifts during mission phases (days).
Description:
High power units like PPUs have the risk of Corona at first start-up if the pressure is too high. Traditionally, such units are therefore only switched on after several days of depressurisation and outgassing. With full electric orbit raising, there is a need to start PPUs within a few hours after separation, in order to start the electric orbit raising as early as possible. The days of depressurisation and outgassing lead to a decay of the spacecraft's orbit while waiting for the operational requirements to be met for switching on the plasmic propulsion.
After choosing a EOR missions profile and a PPU existing design, it is proposed to define the conditions (temperature, pressure, etc.) required to switch-on the PPU as early as possible after separation, without Corona.
The proposed work logic is:
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Selection of a reference PPU design & reference EOR mission profile;
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Define the pressure profile using materials outgassing rate and any other parameters driving pressure decay (manufacturing, temperature, etc.)
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Definition of max pressure allowed to ensure no risk of Corona - analytically, or by test;
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Issue of some recommended methods for a safe start-up after separation without design change - possibly by measuring temperature, pressure, time, etc.
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Validation of this method by test;
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recommend design changes if necessary.
Tender Specifics