Messerschmitt Me 163
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Image:Me 163B-0.jpg The Me 163 Komet was the only operational rocket fighter aircraft. It required a lengthy development process and entered the Second World War in a very limited fashion only in 1944.
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Background
Prior to the start of World War II, Hellmuth Walter had started experimenting with the use of hydrogen peroxide as a fuel for various engines. The fuel was particularly useful as a rocket fuel, as it would "ignite" (although it was actually just decomposing) simply by being passed through a metal catalyst. That meant that one could build an engine with nothing more than a pump and a tube with a wire mesh in it. Hydrogen peroxide was also suited to being the oxidizer for a more conventional rocket engine, instead of just being solely a propellant.
Instabilities in the combustion chamber made it difficult to scale the engine to power outputs useful for an aircraft. Although a number of missiles and RATO systems would eventually be built using this design, any aircraft based on it would have to be very light weight. At the same time the fuel consumption was such that the plane would also require a large internal volume to be devoted to tankage.
Alexander Lippisch had been working for a number of years on tail-less glider designs, which he later suggested be used with the Walter engines. Although Lippisch had not invented the design with rocket power in mind, he argued that a tail-less aircraft could be built with much larger internal volume and still have the same drag as a smaller conventional design. Combining the Walter rocket with a larger Lippisch glider seemed to offer the potential to create a powerful short range rocket interceptor.
Development
Work on the design started under the aegis of the DFS (Deutsche Forschungsanstalt für Segelflug—the German institute for sailplane flight). Their first design was a conversion of the earlier Lippisch Delta IV known as the DFS 39 and used purely as a glider testbed of the airframe.
A larger follow-on version with a small propeller engine started as the DFS 194. This version used wingtip-mounted rudders, which Lippisch felt would cause problems at high speed, and he later redesigned them to be mounted on a conventional vertical stabilizer at the rear of the aircraft. The design included a number of features from its glider heritage, notably a skid used for landings, which could be retracted into the aircraft's keel in flight. For takeoff, wheels were needed due to the weight of the fuel, but these were released shortly after takeoff. It was planned to move to the Walter R-1-203 cold engine engine of 400 kg (882 lbf) when available.
Heinkel had also been working with Walter on his rocket engines, mounting them in the He 112 for testing, and later the first purpose-designed rocket aircraft, the He 176. Heinkel had also been selected to produce the fuselage for the DFS 194 when it entered production, as it was felt that the highly volatile fuel would be too dangerous in a wooden fuselage, with which it could react. Work continued under the code name Project X.
However the division of work between DFS and Heinkel led to problems, notably that DFS seemed incapable of building even a prototype fuselage. Lippisch eventually requested to leave DFS and join Messerschmitt instead. On January 2, 1939 he moved along with his team and the partially completed DFS 194 to the Messerschmitt works at Augsburg.
The delays caused by this move allowed the engine development to "catch up", and once at Messerschmitt the decision was made to skip over the propeller-powered version and move directly to rocket power. The airframe was completed in Augsburg and shipped to Peenemünde West in early 1940 to receive its engine. Although the engine proved to be extremely unreliable, the aircraft had excellent performance, reaching a speed of 342 mph in one test.
Me 163A
Image:Me 163A-1.jpgProduction of a prototype series started in early 1941, known as the Me 163. Secrecy was such that the number, 163, was actually that of the earlier Bf 163 project to produce a small two-passenger light plane, which competed against the Fieseler Fi 156 Storch for a production contract, as it was thought that intelligence services would conclude any reference to the number would be for that earlier design. Me 163 A V1 was shipped to Peenemünde to receive an updated engine, and a successor aircraft, the Me 163 A V3 on October 2, 1941, bearing the radio callsign letters "CD+IM", it set a new world speed record of 1,004.5 km/h (623.8 mph), which was not surpassed until the Douglas Skystreak jet research aircraft surpassed this record on August 20, 1947. Five prototype Me 163 V's were built, adding to the original DFS 194, followed by eight production examples designated Me 163A-0.
During testing the jettisonable main landing gear arrangement proved to be a serious problem and caused many planes to be damaged at take off when the wheels came bouncing up and crashing into the plane. On landing malfunctioning hydraulic dampers in the skid could lead to back injuries for the pilot, and the airplane lacked steering or braking control during the landing run, leaving the pilot unable to avoid obstacles. The landing skid also meant that the aircraft was immobile on the field, presenting an obstacle for other Luftwaffe aircraft and a target for the enemy.
Nevertheless the performance was tremendous and plans were made to put Me 163 squadrons all over Germany in 25 mile (40 km) rings. Development of an operational version was given the highest priority.
ME 163B
Image:Me 163 liftoff.jpg Meanwhile Walter had started work on a newer hot engine which added a fuel of hydrazine hydrate and methanol, designated C-Stoff, that burned with the oxygen-rich exhaust for added thrust. This resulted in the significantly modified Me 163B of late 1941. Due to the RLM requirement that it should be possible to throttle the engine, the originally simple powerplant grew complicated and lost reliability. It took another two years before the B models were ready for widespread testing.
Two prototypes were followed by thirty Me 163B-0 aircraft armed with two MG 151/20 cannons and some four hundred Me 163B-1s armed with two MK 108 cannons, but which were otherwise similar to the B-0. Occasional references to B-1a or Ba-1 subtypes are found in the literature on the aircraft, but the meanings of these designations is now unclear.
The performance of the Me 163 far exceeded that of contemporary piston-engined fighters. After take-off from a dolly, it would be traveling over 200 mph (300 km/h) at the end of the runway, at which point it would pull up into an 80-degree angle of climb all the way to the bombers' altitude. It could go even higher if need be, reaching 40,000 ft (12,000 m) in an unheard-of three minutes. Once there, it would level off and quickly accelerate to speeds around 550 mph (880 km/h) or faster, which no Allied plane could hope to match.
By this point Messerschmitt was completely overloaded with production of the Bf 109 and attempts to bring the Me 210 into service. Production in a dispersed network was handed over to Klemm, but quality control problems were such that the work was later given to Junkers, who was at that time underworked.
For training purposes it was planned to introduce the Me 163S, which removed the rocket engine and tankage and placed a second seat for the instructor behind the pilot. The 163S would be used for glider landing training, which proved to be a serious problem in practice. It appears the 163S's were converted from the earlier 163A series prototypes.
In service the slow-firing MK 108's proved to be a serious problem. The Komet travelled so fast that it was almost impossible to hit a bomber with the needed three rounds to destroy it. A number of innovative solutions were attempted, the most promising being a battery of six 50mm mortars known as Jagdfaust. The trigger was tied to a photocell in the upper surface of the aircraft, and when the Komet flew under the bomber, the resulting change in brightness caused by the underside of the aircraft could cause the rounds to be fired. It appears that this weapon was used in combat only once, resulting in the destruction of a Halifax bomber.
Later versions
Another major concern was the short flight time, which never met the projections made by Walter. With only 8 minutes of powered flight, the plane truly was a dedicated point interceptor. Work started immediately on the development of an engine with two separate combustion chambers, one tuned for "high power" for takeoff and climb, the other for efficient lower-power cruise. This HWK 109-509.C would improve endurance by as much as 50%. Two 163Bs, V6 and V18, were experimentally fitted with the new engine and tested in 1944.
Waldemar Voigt of Messerschmitt's Oberammergau offices started a redesign of the 163 to incorporate the new engine, as well as fix other problems. The resulting Me 163C design featured a larger wing through the addition of an insert at the wing root, an extended fuselage with extra tankage through the addition of a "plug" insert behind the wing, and a new pressurised cockpit topped with a bubble canopy giving dramatically improved visibility. The additional tankage and cockpit pressurization allowed the maximum altitude to increase to 52,000 feet, as well as improving powered time to about 12 minutes, doubling combat time from about 5 minutes to 9. Three prototypes were planned, but it appears only one was flown, and not with its engine.
Meanwhile another redesign was taking form as the Me 163D, which retained the original overall design of the 163B, but included the fuselage plug for increased tankage and a new tricycle undercarriage. Work on this version was "farmed out" to Focke Achgelis, who produced a single prototype in late 1944 or early 1945.
But by this time it appears that Willi Messerschmitt had tired of the entire project, and moved all work on the advanced models to Junkers. Here a new design effort under the direction of Heinrich Hertel at Dessau attempted to combine the 163C's advanced features with the landing gear from the 163D. The resulting Junkers Ju 248 used a three-section fuselage to ease construction. The V1 prototype was completed for testing in August 1944, and was glider tested behind a Junkers Ju 188. Apparently the Walter 109-509.C engine was fitted in September, but it is not clear if it was ever tested under this power. At this point the RLM re-assigned the project to Messerschmitt, where it became the Me 263. This appears to have been a formality only, with Junkers continuing the work and planned production.
However, by the time the design was ready to go into production, after many delays, the plant it was to be made at was overrun by Soviet forces. While it did not reach operational status, the work was briefly continued by the Russian Mikoyan-Gurevich (MiG) design bureau as the Mikoyan-Gurevich I-270.
Operations
Operations began in 1944. As expected, the plane was extremely fast, and for a time the Allied fighters were at a complete loss as what to do about it. The plane often climbed to the bombers faster than the opposing fighters could dive in an attempt to intercept it. A typical Me 163 tactic was to zoom through the bomber formations at 30,000 ft (9,000 m), up to an altitude of 35,000–40,000 ft (10,700–12,000 m), then dive down through the formation again. With luck, this would afford the pilot two brief chances to fire off a few rounds from his cannons before he had to glide back to his airfield. That high speed was to prove a problem in that the builders were never able to make a truly effective weapon for the plane, one that could fire fast enough to allow it to kill a bomber before passing it.
As the cockpit was unpressurized, the operational ceiling was limited by what the pilot could endure for several minutes while breathing oxygen from a mask, without having his blood boil or losing consciousness. Me 163 Pilots underwent altitude chamber training to harden them against the rigors of operating in the thin air of the stratosphere without a pressure suit.
One fighter wing, Jagdgeschwader 400 (J.G. 400), was equipped with the craft in two groups, with the mission of defending synthetic gasoline installations during May 1944. First actions occurred at the end of July, attacking two USAAF B-17s without confirmed kills and continuing in combat from May 1944 to spring 1945. During this time, there were nine confirmed kills with 14 lost.
It wasn't long before the Allied pilots noted the extremely short lifetime of the powered flight. They would wait it out, and as soon as the engine went off they would hunt them down. They also quickly identified the fields the planes operated from and started strafing them after the Me 163s landed. More of the planes were being lost than pilots could be trained on them, and it was clear that the original plan for a huge network of Me 163 bases was never going to happen.
In any operational sense the Komet was a failure. More were lost to landing accidents than they ever accounted for in bomber kills, which stand at only 16. At the same time the Komet was a successful design in pointing the way to the future. It was one more piece of strong evidence that the day of the propeller fighter was over, and it also spawned improved weapons like the Bachem Ba 349 Natter and Convair XF-92. Ultimately, the point defense role that the Me 163 played would be taken over by the surface-to-air missile (SAM).
Japanese versions
As part of their alliance, Germany provided the Japanese Empire with plans and examples of the Me-163. The Japanese versions were designed as trainers, fighters, and interceptors. Differences between the versions were fairly minor. The Mitsubishi Ki-200 Shusui was the equivalent of the 163B, armed with two 30mm Ho155-II cannons. The Navy version, the Mitsubishi J8M1 Shusui, simply replaced the Ho155 cannons with the Navy's 30mm Type 5.
Mitsubishi also planned on producing a version of the 163C for the Navy, known as the J8M2 Shusui Model 21. A version of the 163D/263 was known as the J8M3 Shusui for the Navy with the Type 5 cannons, and Ki-202 Shusui-kai with the Ho155-II for the Army.
Trainers were planned, roughly the equivalent of the Me 163 A-0/S. These were known as the Yokoi Ku-13 Akigusa or Ki-200 Syusui Rocket Interceptor practice glider.
Other trainer variants included:
- Yokoi Experimental Ki-13 Shusui Heavy Glider. This glider was created as the Ki-200 Syusui Rocket Interceptor practice glider. The project was cancelled due to high costs.
- Kugisho/Yokosuka MXY-8 Akigusa Rocket Interceptor practice glider(Experimental Shusui Light Glider). Created as the J8M1 Syusui Rocket Interceptor practice glider.
- Kugisho/Yokosuka MXY-9 Experimental Shusui Heavy Glider. This glider was created as the J8M1 Syusui Rocket Interceptor practice glider, but was cancelled due to high costs.
- Kugisho/Yokosuka MXY-9 Shuka Rocket Interceptor Operative training glider. This plane would have used the Hitachi "Hatsukaze-11" fan jet engine on the MXY-8 "Akigusa" airframe.
Specifications (Me 163B-1)
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