ILC Dover has designed and tested a 16 foot diameter, 32 foot long expandable structure to 25 psi with a minimum safety factor of four at design pressure. This large, highly stressed inflatable uses a resilient multi-layer design approach. The layers consist of macro-woven webbing and rope assemblies, a secondary structural layer, and an underlying inflation retention layer. Multiple assemblies have been constructed and tested for structural integrity, dimensional accuracy and reliable deployment. The structural load bearing members are fabricated from Vectran™ fibers which provide excellent strength and flex fold characteristics so small packing volumes can be achieved. The technology was developed to create a tunnel plug for isolating tunnel sections in an event of flooding or chemical attack. The flexible nature of the approach and scalability of the technology allows the design to be applied towards numerous aerospace and industrial applications such as space habitats, transportable hyperbaric chambers, and out-of-autoclave curing mandrels for the manufacture of large composite parts. Nomenclature= webbing tension R t = rope tension n = number of sides in polygon α = polygon angle p = pressure r = radius σ = membrane stress b = local radius R = global radius