Trisilane is an ideal carbon free fuel as it’s a dense liquid at room temperature and pressure (740 kg/m3), burns efficiently and possesses high energy density (40+ MJ/kg). The only biproduct of combustion is silicon nitrade, a solid. Triilane is ideal for use in external combustion cycles such as S-CO2 Brayton cycles. Heavy duty propulsion applications such as marine and rail require an energy density liquid fuel, the issue is all current carbon free fuels suffer from storage and energy density constraints. Tisilane offers an ideal carbon free propulsion option for heavy duty propulsion. Trisilane is compatible with current liquid infrastructure and holds the title as being the only carbon free liquid fuel, excluding hydrazine, which is considered too toxic. All other carbon free fuels are gaseous or require carbon recycling. Potential power density of supercritical S-CO2 bottoming cycles are 1.4 MW/Ton.