Aerostats

The aerostat is an unmanned air ship capable of ground controlled flight or stationary localisation at any altitude and for extended periods of time (depending on hydrogen producing equipment and solar cell quality, and barring accident, the span of time could be measured in years). Aerostats usually carry communications equipment, though some are being used by weather services worldwide. Its payload does not allow for a crew, so many features that are required on manned ships can be replaced by equipment, fuel and redundant systems.

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