Mechanically-activated nanocomposites (MANCs) of nano-aluminum (nAl)/X (X=Cu, Ni, Zn, Mg, and graphite) were used as replacements for reference nAl powder and as catalytic ingredients in polyurethane (PU) propellants. The effects of their use on combustion heat, burning rate, and thermal decomposition were investigated. It was found that MANCs have catalytic effects and the modified propellants have enhanced the released heat, burning rate, and thermal decomposition properties. MANCs-based propellants have improved the processing and the mechanical properties with acceptable safety aspects. They can be used for catalytic applications in solid propellants to improve their energetic, burning rate, and thermal decomposition characteristics.