Between Planets Shuttle 23

In BETWEEN PLANETS, Heinlein casually tosses out that the shuttle Don Harvey is about to board has a wingspan of 300 feet. The largest wingspan of any aircraft built so far happens to also be a seaplane; the Hughes H-4 Hercules, better known as the "Spruce Goose," has a wingspan of 319 ft 11 in. Since the Spruce Goose was built and flew (one time) before BETWEEN PLANETS was written, it seems a certainty that Heinlein would have known about it. However, the Martin P6M SeaMaster, though a large seaplane, was not nearly so large as the Spruce Goose. So, I assume that this Venusian shuttle is a smaller (perhaps, older) type than the one that took Don Harvey down to Venus. The scale of the kit is a non-standard 1/132. I consider the scale of the Venusian shuttle model to be 1/144, slightly larger but still nowhere near the size Heinlein described.