Our system uses solid conductive propellants that are safe to store terrestrially and on-orbit. One example is the refractory metal molybdenum, which melts at over 2800K and only begins appreciably oxidising at temperatures above 600K. Other systems use highly pressurised gases, or materials that are liquid at room temperature, or materials that must be heated so that they melt or evaporate, or chemically hazardous materials as propellant. In comparison, our propellants are stable enough that we have carried a fully fuelled and integrated unit as carry-on luggage on international flights without issues.