A Survey of Nanotechnology for Rocket Propulsion

The introduction of nano-sized energetic materials (nEM) first occurred in Russia about 60 years ago and raised great expectations in the rocket propulsion community, thanks to higher volumetric energy densities and faster energy release rates with respect to conventional ingredients. Despite intense worldwide research programs, still today mostly laboratory level applications are reported. Pristine nEM ingredients do not fit any propulsive system at industrial level, except for very small additive amounts. A number of practical reasons prevent large-scale applications: inert natural coating of the energetic particles, non-uniform dispersion, excessive viscosity of the slurry propellant, possible limitations in mechanical properties, more demanding safety and aging issues, and so on. A viable solution to transform promises into reality is possible by implementing surface modifications via suitable coating techniques. For example, stabilization through passivation is mandatory to avoid spontaneous ignition in air while specific coatings are recommended to mitigate clustering and viscosity, control reactivity and hazards, and extend the shelf life. After recalling the unique applications made possible by the addition of nEM ingredients in rocket propulsion, this paper intends to discuss the technical challenges, hazards, and aging issues expected during the whole life cycle of nEM in view of their commercialization and large-scale use.