Ignition and combustion of metal fuels under microgravity: a short review

Abstract

Metal fuels have a high potential for applications in space propulsion owing to their superior energy density and distinct combustion characteristics. Therefore, research into the combustion properties of metal fuels in microgravity has become necessary. The principles, applications, benefits, and limitations of experimental methods for microgravity combustion of metal fuels were compared in this review. Drop towers, aircrafts, sounding rockets or microgravity balloons, acoustic or ultrasonic levitation, electrodynamic levitation, space stations, and numerical simulations are common methods used to provide microgravity for combustion research. Among them, the devices providing microgravity environment on the ground has become a good choice for simulating microgravity environment owing to its convenience, reliability and relatively low cost. Further, the physical and chemical properties of common metal fuels, such as aluminum, boron magnesium, and so on, were introduced, and the existing research achievements on the combustion of metal fuels in microgravity are succinctly summarized in this paper. The melting process, ignition temperature, combustion temperature, flame structure, and extinction of metal fuel combustion will be affected by microgravity. Moreover, the necessity and insufficiency of the research are also illustrated. Finally, the existing and potential applications of metal fuels in space propulsion and space weapons are introduced. Metal fuels’ superior energy density and combustion performance can benefit deep-space exploration, particularly Mars exploration, and bring new insights into the design of space weapons. This paper may throw some new light on the study of metal fuel combustion in microgravity.