Me 163 Komet (“Comet”) was not the only one rocket interceptor ever built (the Soviet Union tested but never deployed a BI-1 aircraft that had essentially the same concept), but it was (thankfully) the only one to be mass-produced (~320 have been built) and operationally deployed.
It was also the only such aircraft that saw actual combat – with disastrous results for Luftwaffe – and the first piloted aircraft of any type to exceed 1000 km/h in level flight. German test pilot Heini Dittmar in early July 1944 reached 1,130 km/h (700 mph), an unofficial flight airspeed record unmatched by turbojet-powered aircraft for almost a decade.
Although it was produced by Messerschmitt, it was actually designed by Alexander Lippisch – a pioneer of aerodynamics who made important contributions to the understanding of tailless aircraft, delta wings (now all but standard on fighter- and fighter/bomber aircraft) and the ground effect.
The basic idea behind development and deployment of Me 163 was understandable. Luftwaffe needed an extremely fast interceptor (thus immune to both defensive bomber guns and escort fighters) that (unlike Me-262 turbojet fighter) could be mass-produced using widely available non-strategic materials (e.g. wood), use fuel other than petrol that was in dire shortage and (hopefully) could be flown by relatively inexperienced pilots.
Me-163 was fast indeed; however, it had a number of crucial deficiencies that made it a highly inefficient interceptor (an abject failure, actually). First, it was too fast for an easy and successful intercept – its tremendous speed and climb rate meant a target was reached and passed in a matter of seconds.
And its very short flight time (7.5 minutes of powered flight) meant that (1) the pilot had only one chance of hitting its target and (2) after the Komet ran out of fuel it was transformed into a glider highly vulnerable to both defensive guns and Allied escort fighters.
Although the Me 163 was a stable gun platform, it required excellent marksmanship to bring down an enemy bomber as at least four 30mm hits were typically needed to take down a B-17. The Komet was equipped with two 30 mm MK 108 autocannons which had a relatively low muzzle velocity of 540 meters per second, and were accurate only at short range (<600m), making it almost impossible to hit a slow moving bomber.
Its fuel – hydrogen peroxide – was highly flammable and thus presented a high risk of a spontaneous explosion (which killed several pilots). And its takeoff/landing gear – takeoff dolly jettisoned after the fighter got airborne and retractable landing skid – was prone to malfunction during both takeoff and landing and thus presented more danger to is pilots than enemy guns.
Consequently, it is no surprise that Mei163 was a dismal failure – it accounted for no more than eighteen destroyed Allied bombers with ten combat losses of the Komet. Many more aircraft were destroyed (and pilots killed) during takeoff or landing or in training accidents.
As part of their alliance, Germany provided the Japanese Empire with plans and an example of the Me 163. One of the two submarines carrying Me 163 parts did not arrive in Japan, so at the time, the Japanese lacked all of the major parts and construction blueprints, including the turbopump which they could not make themselves, forcing them to reverse-engineer their own design from information obtained in the Me 163 Erection & Maintenance manual obtained from Germany. The Japanese J8M crashed on its first powered flight and was completely destroyed.