Multiple rocket launcher
[1] The Joseon dynasty of Korea used an expanded variant of such a launcher (called a hwacha) made of 100 to 200 holes containing rocket arrows placed on a two-wheeled cart.
[4] European armies preferred relatively large single-launch rockets prior to World War II.
European navies developed naval multiple launcher mounts with steadily improving explosive rockets for light and coastal vessels.
The Germans began using a towed six-tube multiple rocket launcher during World War II, the Nebelwerfer, called the "Screaming Mimi" by the Allies.
Later in the war, 15 cm Nebelwerfer 41s were mounted on modified Opel Maultier "Mule" halftracks, becoming Panzerwerfer 42 4/1s.
Another version produced in limited numbers towards the end of the war was a conversion of the Schwerer Wehrmachtschlepper ("heavy military transport", sWS) halftrack to a configuration similar to the Panzerwerfer 42 4/1, mounting the 10-barreled 15 cm Nebelwerfer.
As the launch system was inspired by and looked similar to the BM-13, which the Germans had nicknamed "Stalin-Orgel" or "Stalin-Organ", the Vielfachwerfer soon became known as the "Himmler-Orgel", or "Himmler-Organ".
MRLs are still unable to properly engage reverse slope positions in mountain warfare because it is more difficult to determine the trajectory compared to that of a howitzer by adding or removing propellant increments.
[6] Improvised MRLs based on helicopter or aircraft-mounted rocket pods (typically of 57–80 mm caliber) especially on light trucks and pickups (so-called "technicals") are often seen in civil wars when rebels make use of captured launchers and munitions.
Trajectory-correcting munitions may then benefit from this, as a directional radio may send a coded message to the rocket to deploy air brakes at just the right time to correct most of the range error.
A more sophisticated system makes use of radar data and a one-way radio datalink to initiate a two dimensional (range and azimuth) correction of the rocket's flight path with steering by fins or nose thrusters.
Long-range MRL missiles often fly a higher quasi-ballistic trajectory than shorter-ranged rockets and thus pose a de-confliction challenge, as they might collide with friendly aircraft in the air.
