The efficiency of various methods for deflection of dangerous space objects (e.g., asteroids) is studied. The main physical processes related to a distant nuclear explosion are analyzed, and a mechanical momentum is calculated. Mechanical momenta resulting from explosions of buried nuclear and chemical charges are quantitatively estimated. Approximate expressions for estimation of the mechanical momentum related to explosion or high-velocity impact are derived. The topicality of the protection of the earth from dangerous space objects and the corresponding particular problems are discussed.