Built to float in the carbon dioxide atmosphere of Venus, aerostats are essentially cities built as giant balloons. The breathable atmosphere filling aerostats is lighter than the surrounding atmosphere, so aerostats feature open areas with massive volumes of air that enable them to float. Aerostats are not pressurized, as the interior air pressure is roughly equal to the exterior atmosphere, meaning that there is no need for heavy airlocks, just airtight doors and bulkheads. Aerostats are constructed from lightweight but durable materials such as aerogels, diamond, and metallic foam.
Most aerostats are shaped like a balloon or upside-down tear drop. The center of each is a massive vertical air-filled chamber, reaching from top to bottom, that provides buoyancy. Other parts of the aerostat are built with large open airy areas and high ceilings. External parts of the structure may feature tall privately owned towers and open areas for synthmorphs that do not require breathable atmosphere. Most aerostats are mobile, floating through the stable areas of the Venusian atmosphere. Occasionally an aerostat will tether itself to the surface at mining or research outposts, allowing supplies and resources to be transferred via elevator cables.
Aerostats present would-be attackers or infiltrators with a set of challenges considerably different from space habitats. Aerostats don’t have the large, active fleets of defense and harvester drones that space habs do, but they do have numerous landing bays for atmospheric craft. Life support aboard an aerostat is dispersed throughout the habitat’s hull, consisting of little more than large banks of CO2 scrubbers connected to a cooling and ventilation system. The accompanying networks of ducts crisscross the entire habitat and can be extremely useful to lithe interlopers. At the same time, an aerostat contains large, open spaces that serve dual duty as public atriums and as chambers to hold the oxygen and nitrogen that makes the habitat buoyant. These big open spaces provide ample maneuvering space for robotic fliers and other small aircraft. These areas make it easy for hab designers to spatially segregate important administrative buildings from surrounding structures, something that can’t be done in more cramped habitats. Getting aboard an aerostat is an easier job than infiltrating other stations, but striking at its heart can be much more difficult.

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