A propulsion device contains a working mass within an enclosed plenum, where the working mass is recirculated through the plenum to produce a net force vector. The first lamp carriage assembly is fixedly coupled between the first and second plates for directing light output by the first lamp in a first direction. The programmable electronic ignition system can employ a cylinder location sensor to identify a predetermined cylinder for controlling individual cylinder ignition timing retards. In various embodiments, a unitary roof body may engage the unitary cabin body in a stowed mode for transport, for example, and be raised above the unitary body in a deployed mode for occupancy. The invention also deals with a process for producing such derivatives and materials having controllable molecular weight with narrow molecular weight distribution. The image-taking lens system includes a reflective optical element that bends the optical path.