Hardened, reliable, quick opening/closing closures for the tunnels in a deep base are essential to the survival and operation of the deep base. It is proposed to (1) generate a number of concepts for such closures, (2) screen those concepts on the basis of their operability, simplicity, constructibility, obvious cost impacts, and their adaptability to being hardened, (3) to refine selected concept(s) to establish their hardness and functional adequacy, (4) to prepare a preliminary design of a mechanical operating system and establish its adequacy, hardenability, cost, and speed of operation, and (5) to establish the feasibility of the entire design.
