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A rocket assisted projectile (RAP) is a cannon, howitzer, mortar, or recoilless rifle round incorporating a rocket motor for independent propulsion. This grants the projectile both greater speed and range than an ordinary shell, which is propelled only by the ballistic force of the gun's exploding charge. Some forms of rocket assisted projectiles can be outfitted with a laser-guide for greater accuracy.
The German Sturmtiger (1944) used a 380 mm Rocket Propelled Round as its main projectile. These rounds had a maximum range of 6,000 m, and came with high explosive shells or shaped charges. A normal charge first accelerated the projectile to 45 m/s (150 ft/s), the 40 kg (88 lb) rocket charge then boosted this to about 250 m/s (820 ft/s).
The North Korean M-1978 / M1989 (KOKSAN) 170mm self-propelled gun can use rocket assisted projectiles to achieve a range of around 60 kilometres (37 mi); at one time this was the world's longest range tube field artillery piece.
When NATO standards required member armies to have corps-level artillery that could fire to a minimum range of 30,000 metres (19 mi), nearly all member nations solved the problem with RAP rounds in their 155 mm (6.1 inch) artillery. The Belgian Army was the only NATO member army that did not require RAP, reaching the required range with a conventional round.
- Base bleed rounds, a similar concept for extending artillery range.
- Long Range Land Attack Projectile, a 155mm round for the Advanced Gun System that uses a rocket motor to increase range.
- Extended Range Guided Munition, a 127mm round that was to be used in existing 5" guns.
- "M-1978 / M1989 (KOKSAN) 170mm self propelled (SP) gun". Global Security. Retrieved 19 March 2016.
- GlobalSecurity.org Rocket Assisted Projectiles page includes RAP projects from around the world.