Pumpkins and onions and balloon design

Abstract The reach for a capability to make long flights (months) with heavy payloads (tonnes) has long been pursued. The closest we have come is with polar flights devoid of a significant diurnal cycle. Superpressure technology, with its ability to survive diurnal cycles, is an obvious choice, but materials limitations have been an obstacle to realizing these ambitious goals. Now comes an assortment of new synthetic materials, coupled with a special variety of superpressure balloon which, in combination, is poised to yield a solution for our enhanced duration/payload quest. In this paper we are looking not at materials, but only at a balloon concept. This concept is a “natural shape” oblate spheroid balloon whose shape is chosen to exploit properties of component materials, particularly newly available ones. The current variation of this concept is called a “pumpkin” balloon. The most visible work on this shape is that done by France's CNES, Japan's ISAS, and in the USA by NASA's Wallops Flight Facility. But the basic design idea is not new; it extends back at least a half century. This paper traces the origins of the shape, its evolution through various iterations, and it speculates on some of the recent thinking regarding construction details.