Rocket-assisted projectile

XM1113 extended-range artillery round, shown here at a range demonstration, uses a rocket-assist motor

A rocket-assisted projectile (RAP) is a cannon, howitzer, mortar, or recoilless rifle round incorporating a rocket motor for independent propulsion. This gives the projectile greater speed and range than a non-assisted ballistic shell, which is propelled only by the gun's exploding charge. Some forms of rocket-assisted projectiles can be outfitted with a laser guide for greater accuracy.

History

Colour-coded section view of a rocket-assisted projectile ammunition round

The German Sturmtiger (1944) used a 380 mm (14.9-inch) Rocket Propelled Round as its main projectile. These rounds were high explosive shells or shaped charges with a maximum range of 6 kilometres (3.7 mi). The gun 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).

Also the German Krupp K5 railway gun of World War 2 used rocket-assisted projectiles in the later stages of the war, although it also used conventional artillery projectiles.

The North Korean M-1978 / M-1989 Koksan 170 mm (6.7-inch) 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 kilometres (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.

The XM1113 RAP round replaced the M549A1 RAP round for the M777 howitzer and other 155 mm (6.1-inch) artillery after 2016. The new round had a range of 39 kilometres (24 mi) instead of the 30 kilometres (19 mi) NATO standard. As of 2016, the XM1113 was scheduled for Limited Rate Initial Production in fiscal year 2022.

See also

• Base bleed rounds, another way to extend artillery range
• Extended Range Guided Munition, a 127 mm round that was to be used in existing 5-inch guns
• Long Range Land Attack Projectile, a 155 mm round for the Advanced Gun System that uses a rocket motor to increase range

External links

• GlobalSecurity.org Rocket Assisted Projectiles page includes RAP projects from around the world.
• Army researchers add power, range to artillery Picatinny Arsenal
• US3572249A - High efficiency rocket munition