Werfer - Granate 21 The " Werfer - Granate 21 " rocket launcher , also known as the BR 21 ( the " BR " standing for " Bordrakete " ) in official Luftwaffe manuals , was a weapon used by the German Luftwaffe during World War II and was the first on - board rocket placed into service by the Luftwaffe , first introduced in mid 1943 . The weapon was developed by Rheinmetall - Borsig under the leadership of Dipl . - Ing . Rudolf Nebel , who had pioneered German use of wing - mounted offensive rocketry in World War I with the " Luftstreitkräfte " . History . The tight formations flown by USAAF heavy bombers allowed their defensive heavy machine guns to provide mutual cover to one another , and such a combat box was an extremely dangerous environment for a fighter aircraft to fly through . This weapon enabled the German pilots to attack their bomber targets from a safer distance of over a kilometer , where the risk of being hit was much reduced . Although extremely inaccurate , the rockets did not have to destroy the bombers , but only cause them to take evasive action that would disrupt their protective formation , making them vulnerable to conventional attack . While a single fighter ' s payload of two or four such rockets was extremely unlikely to score a hit , a mass launch by an entire fighter squadron ( 12 - 16 aircraft ) as it arrived to intercept the bombers would likely score two or three hits , about 15 % accuracy . The rocket ' s huge blast radius also compensated for inaccuracy , and even a non - lethal hit on a bomber by a showering of shrapnel would have psychological effects and perhaps cause it to take evasive manœuvres that would drive it from the protection of its fellows . JG 1 and JG 11 were the first front line units to utilise the weapon during the spring of 1943 . During the autumn of 1943 the Bf 110 G - 2 " Zerstörer " of ZG 26 and ZG 76 were also equipped with it . These weapons were also sometimes used against ground targets from late 1943 onwards , such as in the Italian campaign 1943 – 44 , the 1944 Normandy campaign and during the Ardennes Offensive . Design and capabilities . Modified from the 21 cm Nebelwerfer 42 infantry barrage rocket projectile and reconfigured for air - launch , the spin - stabilised rocket was propelled by diglycol solid fuel , and the warhead weighed . The Wfr . Gr . 21 ' s projectile had a velocity of per second ( 1 , 150 km / h , 716 mph ) and a maximum range of . The rocket and tube weighed some in total . A time fuse detonated the warhead at a pre - set distance of to from launch point , resulting in a lethal blast area approximately wide . Usage . Single seat fighters carried a single tubed rocket under each wing , while the " Zerstörer " heavy twin engine fighters carried two under each wing . Operationally the weapon had several disadvantages ; the launcher tubes produced significant air resistance and reduced speed and manoeuvrability and general performance . The tubes were jettisonable , and once the rocket had been fired the fighter could revert to a ' clean ' profile . Shortcomings . The relatively low velocity of the rocket created a considerable problem in attempting to counter the resultant ballistic drop of such a slow - moving projectile , which required that the launcher tubes be mounted at a roughly 15° angle upwards from the line of flight , causing considerable drag on the airframe of the carrier aircraft . The low launch velocity also meant accurate aiming was difficult , as it was for the attacking pilot to accurately judge the distance to the target . As a result most of the rockets fired exploded either in front of or behind the bomber target . However , they did often achieve the effect of opening up the bomber formations enough for fighters to attack with conventional weapons . Aircraft armed with the Wfr . Gr . 21 . " Underwing mount ( singly , one under each wing ) " " Underwing mount ( two under each wing ) " " Under - fuselage mount ( one each side , from bomb racks flanking nosegear well ) "