Many good ideas for the development of airships have yet to be fully explored. Airship structures can be rigid, semi-rigid or non-rigid. Shapes can range from tubular to catamaran to disks or spheres. Similarly, many materials can be used to build envelopes and gas cells. Finally, many methods exist to adjust buoyancy. Ballast can be taken on/off, or gas can be vented (if hydrogen is used). The lifting gas can be heated, cooled or compressed. Aerodynamic lift can be obtained in conjunction with engine thrust. Of course, all these approaches can be used in some combination. What is clear at this point is that the dominant design for a cargo airship has yet to be proven. BASI is examining many design alternatives and materials to build less expensive and more robust airships for cold climates.