7.1. Scope#

This chapter deals with the miscellaneous items which are represented by all parts/item (or sets of parts) which are not fully electrical parts, nor fully mechanical parts nor fully structural parts. The current reliability models (EEE parts, mechanical parts) are not adapted and are not the preferred way to support reliability predictions for these items. Therefore, other ways to provide reliability estimates are proposed in this chapter and are detailed in the next sections.

The Fig. 7.1.1 represents examples of some miscellaneous parts/items:

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Fig. 7.1.1 Examples of some miscellaneous items#

The list provided below may contain some items that are in fact EEE or mechanical type items, but which are classified as “miscellaneous” because the modelling approach for EEE/mechanical is not considered as completely suitable.

One of the major characteristics of miscellaneous parts/items is that they are various (functions, technologies, nature) and very specific in the sense they are designed to support dedicated and usual functions (e.g. battery) in a satellite:

  • They cover a wide range of Technologies (e.g. Chemical, fluidic…) apart “simple” electrical or mechanical technologies,

  • They are not fully covered by elementary “EEE or Mechanical” models (e.g. a battery cathode is not a pure EEE Part),

  • The failures may originate from particular failure mechanisms (e.g. catalytic bed degradation for N2H4 thrusters),

  • They may be supported by “Innovative” technology (e.g. Plasmic propulsion) with reduced in-orbit return,

  • They can be submitted to Wear-out process (e.g. battery calendar aging) depending on their nature.

Note

Software is, by nature, a miscellaneous item. Due to its specificity, a dedicated Section 9.4.10 in the system chapter addresses software reliability modelling and therefore software reliability is not considered in the present chapter.