The Travel Tube is a rapid transport system connecting the different parts of Moonbase Alpha. The name, and design, is clearly inspired by the circular tunnels and carriages of the London Underground, popularly known as the Tube. The Moonbase Travel Unit moves on top and bottom rails. The rails are slotted, and the travel unit has a prong on top and bottom that fits into the slot. Presumably they are powered by a maglev system, which require minimal maintenance.
Photo by Phil Rae of the original model. It was about 28cm/12 inches in diameter. The cylinder is illuminated inside, the light bleeding through the door frame and outer ring. The side door- barely seen on screen - is undetailed. The front face is askew in this picture. Only the front face exists today, pictured below.
Copyright Martin Willey