A new ISS development strategy demanded technological breakthroughs. Traditional metal structures are being replaced with sophisticated inflatable modules with a flexible membrane. They are delivered to the orbit in a folded state, connected to the station by a robotic arm and then inflated to the required size. Tests have shown that these new modules can perfectly withstand the blows of micrometeorites and prevent cosmic rays passing into the station. The problem of fragility and possible air leaks has been resolved relatively quickly – its shell bears little resemblance to the balloon, rather it resembles a thick tire, wrapped in a coating resembling kevlar.
Expandable modules are more flexible and much easier to manufacture than hard metal structures, which greatly reduces their delivery cost to the ISS. They are more suited to cope with a variety of tasks. Inflatable modules can be connected to each other and create even larger specialised objects with a greater payload.