The Roswell Report: Case Closed

## 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.

The initial polyethylene balloons had diameters of only seven feet and carried payloads of five pounds or less. $ ^{72} $ As balloon technology advanced, payload capacities and sizes of balloons increased. Modern polyethylene balloons, some as long as several football fields when on

Fig. 48. Relative sizes of a modern high altitude poyethelyne 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)