Proceedings Eighth Afcrl Scientific Balloon Symposium 30 September To 3 October 1974

This publication contains preprints of papers presented at the Eighth AFCRL Scientific Balloon Symposium, 30 September to 3 October 1974, held at Hyannis, Mass. The papers are grouped in accordance with the five symposium sessions: powered balloons, tethered balloons, free balloon technology, balloon-borne experiments, and special applications

This publication contains papers presented at the Ninth AFGL Scientific Balloon Symposium, 20 October to 22 October 1976, held at Wentworth By-The-Sea, Portsmouth, New Hampshire.

Those who use large polyethylene balloons for experimental programs are presented with background information on the processes of selecting and designing balloons to meet their respective mission requirements. The effects of payload weight, altitude, duration, and vertical control on both the total payload weight and the balloon size are discussed with respect to these processes. The need to define missions success in terms of realistic requirements is emphasized and a mission planning procedure is proposed. Assumptions and problems in contemporary balloon design are discussed, and design and analysis procedures based on the loads and geometry at the time of launch are developed. Dynamic launch shock is proposed as a criterion for shell thickness, and a model of polyethylene film modulus is developed to account for strain rate and stress and strain relaxation at a launch temperature of 23 degrees C. Computer codes have been written for the processes of balloon selection and balloon design to meet mission requirements. They are intended to be a basis for more efficient, interactive mission planning. Finally, improvements to the balloon design process are proposed and discussed.

The need for a technique of instantaneously effect controlled balloon-system descent from high altitude prompted the development efforts reported herein. The background, the approach, test flight data, and the technical problems that frustrated the successful development of the desired technique are included. A simplified model of the shape of a partially full balloon is presented (a model that should also approximate the dimensions of subpressure shapes). Some heretofore unpublished information on apex valve characteristics and subpressure effects are included together with recommendations for any future work of this problem. Significant supplementary findings and historical perspectives are noted. (Author).

The history of the development of free balloons to carry heavy payloads into the stratosphere is reviewed with the objective of developing a design based on existing technologies for a balloon to carry 9000 lb to 90,000 ft. Reinforced polyester balloons, in tandem balloon configurations, are discussed with respect to materials, design criteria, and performance. The problem of launch dynamics for single cell polyethylene balloons is also discussed and it is concluded that a capped single cell polyethylene balloon can be dynamically launched, successfully, with the 9000-lb payload. Further, it is concluded that the single cell polyethylene balloon is the best means to meet the objective. Specifications for such a balloon are provided.