replace the 28 and 32 cm rockets, which had too short a range. Advances in propellant chemistry also reduced its smoke signature. It could be fired from all of the same platforms as the older rockets and many of the older launchers were converted to be used with the newer rocket by installing adapter rails, although it also had its own purpose-designed launcher, the 30 cm Raketenwerfer 56. Fewer than two hundred thousand rockets and 700 launchers were built during the war. 8 cm Raketen-Vielfachwerfer The Waffen-SS decided to copy the Soviet M-8 Katyusha rocket launcher as the 24-rail 8 cm Raketen-Vielfachwerfer. Its fin-stabilized rockets were cheaper and easier to manufacture than the German spin-stabilized designs and used cheaper launch rails. It was also capable of using the considerable stocks of captured Soviet rockets. Separate production lines were set up under party control as the army refused to convert any of its existing factories, but not many actually appear to have been made. Production quantities are unknown, but photographic evidence shows the launcher mounted on lightly armored versions of the Sd.Kfz. 4 "Maultier" and captured French SOMUA MCG half-track. Panzerwerfer To improve the mobility of the Nebelwerfer units, a ten-tube launcher was mounted on a lightly armored Sd.Kfz. 4 "Maultier" half-track chassis as the 15 cm Panzerwerfer 42 auf Selbstfahrlafette Sd.Kfz. 4/1 (based on the Opel "Maultier", or "Mule", half-track). Three hundred of these were produced, split evenly between launchers and ammunition carriers (which were identical except for the launcher). These were superseded in production by the 15 cm Panzerwerfer 42 auf Schwerer Wehrmachtsschlepper (Panzerwerfer auf SWS), which had improved cross-country mobility and had greater ammunition storage than the "Maultier". The exact number built of the latter weapon is unknown, but evidence suggests that fewer than 100 were completed before the end of the war. Air-to-air adaptation (Werfer-Granate 21 rocket) The Werfergranate 21 (Wfr. Gr. 21), also called the 21 cm BR (BR believed to be the abbreviation for "Bordrakete" in official Luftwaffe manuals) was an unguided air-to-air rocket version of the projectile used in the Nebelwerfer 42 and was first used in the defense of Schweinfurt on 17 August 1943. The Wfr. Gr. 21 was mounted on Messerschmitt Bf 109 and Focke-Wulf Fw 190 fighters (one launch tube under each wing) and on the Messerschmitt Bf 110 and Messerschmitt Me 410 heavy fighters (two launch tubes under each wing)