Ultrasets, Shock Hammocks and Orion Ship Michael

Added a few more over the weekend; the first few from a great Lester del Rey story from 1939. This story has a very early mention of the ultrawave, a faster-than-light communication system. The shock hammock from the same story is a very early reference (maybe the first - del Rey believes so) to the fact that, when accelerating at high gravities, the pilot's body must be perpendicular to the direction of motion.

Finally, the Orion nuclear-pulse ship Michael from Niven and Pournelle's excellent Footfall was added, along with a cool illustration.