Lighter than Air Vehicle Gas Leak Rate Measurement, 15-R8212
Principal Investigator
James Noll
Inclusive Dates: 03/11/11 – 07/11/11
Background — Stratospheric airship development efforts under SwRI's HiSentinel program have yielded a recent flight of a quarter-million cubic foot displacement vehicle to an altitude of more than 60,000 feet. The airship hull structural integrity was maintained throughout ascent and during float. Prior to flight, the hull underwent leakage rate testing over multiple days. It was instrumented and inflated to a differential pressure of several inches of water while stationed at ground level. The rate measured during this testing predicted the inflation gas leakage observed during flight. Improvement in the flight duration of subsequent similar lighter-than-air platforms will be realized by reducing the overall leakage rate of the airship hull and requires corresponding improvement of the leak qualification testing itself.
Approach — State-of-the-art sensor technology and leak-assessment methodology have been researched to understand the best approach to quickly and inexpensively quantify the leaks in an airship hull. The completed research investigated a modified pressure decay leak testing methodology for determining overall leakage rate in a large inflatable structure. This methodology was tested via a prototype instrumentation system. The system was calibrated against a fixed volume test article with known leak rates and was used to test an inflatable structure.
Accomplishments — The research has produced specifics on the sensor precision, sensor configuration and test duration required to quantify small leakage rates with a high degree of confidence. The methodology developed during this effort will make future testing more accurate and cost-efficient.
