SUPERPRESSURE BALLOON FOR CONSTANT LEVEL FLIGHT
AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
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The superpressure balloon is a sealed, virtually non-extensible plastic cell that will float at a constant density altitude despite diurnal fluctuations in the superheat of the lifting gas. This type of balloon does not require ballast to maintain altitude. Instead, it depends upon the ability of the plastic cell to retain all of the lifting gas without significant change in volume, at varying pressures that always remain higher than ambient. The superpressure balloon is more efficient, and is considerably smaller than the valved balloon designed for the same altitude, payload and duration. It provides a highly stable platform for long-duration experiments in the stratosphere. General equations relating superpressure, superheat and free lift are derived and the allowable temperature-fluctuation limits for maintaining altitude are considered. The stringent physical requirements imposed upon suitable materials and some of the special materials-testing procedures for superpressure application are discussed. Design equations are given for the cylindrical, tetrahedral, onion and spherical shapes.
- Lighter-than-air Aircraft