Abstract Inflatable space structures have become an important part of space explorations due to their lightweight, simpler design, low cost, and fewer parts. These structures include antennas, solar arrays, solar concentrators, reflectors, etc. These structures are made of flexible polymers which can be folded and easily carried with spacecraft due to their small volume and weight. Structures, when reaching their destination, are inflated through internal pressurization to achieve desired structural integrity. In space, these structures are subjected to very harsh environment such as high radiation levels, structural vibrations, and micrometeoroid bombardments. The polymeric material used to fabricate these structures is susceptible to degradation under these harsh conditions. These structures are prone to lose their structural integrity over long-term degradation of the material. The most common problem associated with inflated space antennas is leakage of inflated gas. Hence, the health monitoring of these structures becomes crucial to avoid structural failure due to leakages which may cause loss of information, accuracy, and money. Gas sensors are used to detect leakages in these structures. A mixture of helium (He) and nitrogen (N2) is used as inflating gas in space antennas. Helium is the lightest gas after hydrogen and has chemically inert, nonflammable nature which makes it an ideal inflating gas. However, the detection of He leakages is very difficult because of its nonreactive behavior with chemical species. Metal oxide based semiconducting (MOSs) materials are widely used sensing element for detection of various gases. Although it is very difficult to find out He gas leakages, vanadium pentoxide (V2O5) can detect even a small concentration of He through resistive changes. In this chapter, we will discuss the requirement of leakage monitoring system for inflatable space antennas and He gas sensing properties of V2O5 semiconducting material.