Using magnesium hydride as the future dual-mode propellant for spacecraft: A simulation investigation

• MgH 2 was first applied as the H 2 and Mg sources for the dual-mode propulsion system of the spacecraft. • A novel MgH 2 hydrogen storage tank was proposed to adapt to zero gravity used for spacecraft. • The complete hydrogen desorption process of the MgH 2 tank at high backpressure was proved. • The parameters were optimized to achieve a high hydrogen desorption rate per unit thermal power. A dual-mode propulsion system stands as the important viable pathway for future multi-purpose deep space missions by the spacecraft, encompassing both nuclear thermal propulsion and nuclear electric propulsion. H 2 and Mg emerge as potential mediums for nuclear thermal propulsion and nuclear electric propulsion, respectively, with the possibility of utilizing a single material, magnesium hydride (MgH 2 ), to serve both purposes. However, how to release hydrogen completely and effectively in high hydrogen desorption pressure while retaining magnesium is the key problem. In this work, we proposed a novel MgH 2 storage tank for zero gravity environments and investigated its hydrogen desorption process at high pressures of 4 ∼ 8 MPa using simulation, which is crucial for the hydrogen supply of nuclear thermal propulsion. We examined the effects of hydrogen desorption pressure, inlet temperature, and flow velocity of argon (Ar) on the desorption process. The simulation results indicated complete decomposition of MgH 2 can be realized under 4 ∼ 8 MPa at 873 K. Moreover, the desorption pressure, inlet temperatures, and high flow velocities of Ar are suggested as 4 MPa, 773 ∼ 785 K, and 45 ∼ 100 m s −1 to achieve an average hydrogen desorption rate per unit thermal power of ≥ 20 mgH 2 s −1 . This work marks the first confirmation that MgH 2 can decompose into H 2 and Mg under high hydrogen desorption pressure at suitable thermal power, paving the way for its application as the hydrogen and Mg storage media in the dual-mode propulsion system of spacecraft.