[Illustration: Fig. 46. Publicity photograph from _On the Threshold of Space_ with (_from left_) Cameron Mitchell, Guy Madison and Dean Jagger. Scenes from the movie clearly depict the actual anthropomorphic dummies described nearly 40 years later as extraterrestrial “aliens.”] [Illustration: Fig. 47. Col. J. P. Stapp’s historic 1954 rocket sled test was re-created for _On the Threshold of Space_ (_see figure 33, page 31_).] High Altitude Polyethylene Research Balloons In 1946, as a result of research conducted for project MOGUL, Charles B. Moore, a New York University graduate student working under contract for the U.S. Army Air Forces, made a significant technological discovery: the use of polyethylene for high altitude balloon construction.[71] Polyethylene is a lightweight plastic that can withstand stresses of a high altitude environment that differed drastically from, and greatly exceeded, the capabilities of standard rubber weather balloons used previously. Moore’s discovery was a breakthrough in technology. For the first time, scientists were able to make detailed, sustained studies of the upper atmosphere. Polyethylene balloons, first produced in 1947 for Project MOGUL, are still widely used today for a host of scientific applications. High altitude polyethylene balloons and standard rubber weather balloons differ greatly in size, construction, and utility. The difference between these two types of balloons historically has been the subject of misunderstandings in that the term “weather balloon” is often used to describe both types of balloons. High altitude polyethylene balloons are used to transport scientific payloads of several pounds to several tons to altitudes of nearly 200,000 feet. Polyethylene balloons do not increase in size and burst with increases in volume as they rise, as do standard rubber weather balloons. They are launched with excess capacity to accommodate the increase in volume. This characteristic of polyethylene balloons makes them substantially more stable than rubber weather balloons and capable of sustained constant level flight, a requirement for most scientific applications. [Illustration: Fig. 48. Relative sizes of a modern high altitude polyethylene research balloon, an airliner, and a hot-air balloon. Inaccurate characterizations of the giant high altitude research balloons as “weather balloons” (which are typically 15 feet in diameter) has historically been the source of confusion. (_courtesy of Mike Smith, Raven Industries_) Raven Industries 40 million cubic foot balloon. 450 ft in diameter at 130,000 feet Hot-air balloon. 50 ft in diameter DC-9 airliner 104 ft long]