Nuts and bolts

We have discussed in this section the system-level issues associated with providing energy to a planetary probe. There are of course many subsystems required to make everything actually work; subsystems that may require significant design and development effort. Details of these, which would include power switches, current limiters, peak-power trackers for solar arrays, battery charge regulators and so on, are beyond the scope of this book, however. Requirements are often driven by non-nominal cases - for example a regulator that works perfectly well for years of a main mission may be inadequate to provide enough current for a fraction of a second to fire pyrotechnic devices at the start of the mission (pyrotechnic devices are often therefore wired directly to the unregulated battery terminals).

The mass of a spacecraft harness is often forgotten, but can be quite significant -e.g. the harness on the 200 kg Huygens probe itself weighed some 12 kg - a not insubstantial amount.

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