Gas Replacement System (GRS)

nbsp;The Gas Replacement System (GRS) is a new technology that enables long duration flight of Super Pressure Balloons (SPBs) at nearly constant altitude. In the GRS, a storable liquid such as ammonia is carried aboard the balloon mission gondola and used to replace helium that leaks from a SPB. The ammonia can be used directly as a helium replacement gas, or it can be dissociated into a very low molecular weight nitrogen/hydrogen mix. In either case, the balloon remains fully inflated, and remains floating at nearly constant altitude. The advantage of using a storable liquid in this way, rather than as ballast, is that consumable mass is greatly reduced, being cut by a factor of 1.7 in the simple (S) non-dissociation system and 3.4 in the (D) dissociation system. Moreover, in a ballast system the floating mass of the balloon changes by the sum of the ballast and the leaked helium, whereas in the GRS the only the leaked helium is lost. Thus the floating mass of the system remains almost constant, with near constant cruise altitude being maintained as a result, Indeed, using the CRS the altitude excursion for compensating for a given amount of helium leakage being reduced by a factor of 8 compared to a ballast-dropping alternative. The GRS is a simple low-mass system requiring very low power. In the proposed program, the potential performance of the GRS will be analyzed, design options compared, designs developed and built for both S and D type units, and the concept validated by means of lab tests of GRS prototypes.