RPG-7 - Propulsion System

Propulsion System

According to the United States Army Training and Doctrine Command (TRADOC) Bulletin 3u (1977) Soviet RPG-7 Antitank Grenade Launcher—Capabilities and Countermeasures, the RPG-7 munition has 2 sections: a "booster" section and a "warhead and sustainer motor" section. These must be assembled into the ready-to-use grenade. The booster consists of a "small strip powder charge" that serves to propel the grenade out of the launcher; the sustainer motor then ignites and propels the grenade for the next few seconds, giving it a top speed of 294 meters per second. The TRADOC bulletin provides anecdotal commentary that the RPG-7 has been fired from within buildings, which agrees with the two-stage design. It is stated that only a 2-meter standoff to a rear obstruction is needed for use inside rooms or fortifications. The fins not only provide drag stabilization, but are designed to impart a slow rotation to the grenade.

Due to the configuration of the RPG-7 sustainer/warhead section, it responds counter-intuitively to crosswinds. A crosswind will tend to exert pressure on the stabilizing fins, causing the projectile to turn into the wind. While the rocket motor is still burning, this will cause the flight path to curve into the wind. The TRADOC bulletin explains aiming difficulties for more distant moving targets in crosswinds at some length. The RPG-7 has no noticeable recoil, the only effect during firing being that of the sudden lightness of the launcher as the rocket leaves the tube.