proposed system employs three separate airship stages to reach orbit. Multiple vehicles are needed because an airship made strong enough to survive the dense and turbulent lower atmosphere would be too small and heavy to lift payloads high enough. An orbital airship must be much larger and with thinner walls to maintain its buoyancy-to-weight ratio. The three stages are; the Ascender ground launcher, the Dark Sky permanent sky station, and the Orbital Ascender spacecraft. A fourth airship design similar to the record-breaking Tandem but based on air-filled beams will be required for the assembly of Dark Sky Station. Because of the thin atmosphere at such high altitudes, to carry a useful payload very large volume and/or very strong but lightweight materials are required. The ISAS BU60-1 scientific balloon holds the world altitude record for an unmanned balloon as of 2009, at 53.0 km. The average density of BU60-1 over its gross volume was 0.00066 kg per cubic meter. To fly higher, this must be significantly improved. Ascender The Ascender airship would operate between the ground and the Dark Sky Station at 140,000 feet (ca. 42,672 m). A long, V-shaped planform with an airfoil profile would provide aerodynamic lift to supplement the airship's inherent buoyancy, with the craft driven by propellers designed to operate in a near vacuum. The Ascender would be larger than any airship yet built, but would be dwarfed by the later stages. It would be operated by a crew of three. JP aerospace has developed two large-scale test models, the Ascender 90 and the Ascender 175. The number denotes the length of the airship in feet (ca. 27.4 m and 53.3 m). More recent airships have reverted to being named in sequence. Dark Sky Station The Dark Sky Station would be a permanent floating structure, remaining at 140,000 feet (ca. 42,672 m). It provides an intermediate stage allowing transfer of cargo or personnel between the Ascender stage and the orbital stage. It would also serve as the construction facility for the orbital component, which would be too fragile to travel lower. The station could also be used as a relay station for telecommunications due to its high altitude. Orbital Ascender The Orbital Ascender airship would be the final flight stage from the station to orbit. It would initially rise as a lighter-than-air craft from the station at 140,000 feet to 180,000 feet (ca. 42,672 m to 54,864