Messerschmitt Me 163 Komet
The Messerschmitt Me 163 Komet is a rocket-powered interceptor aircraft primarily designed and produced by the German aircraft manufacturer Messerschmitt. It is the only operational rocket-powered fighter aircraft in history as well as the first piloted aircraft of any type to exceed in level flight.
Development of what would become the Me 163 can be traced back to 1937 and the work of the German aeronautical engineer Alexander Lippisch and the Deutsche Forschungsanstalt für Segelflug. Initially an experimental programme that drew upon traditional glider designs while integrating various new innovations such as the rocket engine, the development ran into organisational issues until Lippisch and his team were transferred to Messerschmitt in January 1939. Plans for a propeller-powered intermediary aircraft were quickly dropped in favour of proceeding directly to rocket propulsion. On 1 September 1941, the prototype performed its maiden flight, quickly demonstrating its unprecedented performance and the qualities of its design. Having been suitably impressed, German officials quickly enacted plans that aimed for the widespread introduction of Me 163 point-defence interceptors across Germany. During December 1941, work began on the upgraded Me 163B, which was optimized for large-scale production.
During early July 1944, German test pilot Heini Dittmar reached, an unofficial flight airspeed record that remained unmatched by turbojet-powered aircraft until 1953. That same year, the Me 163 began flying operational missions, being typically used to defend against incoming enemy bombing raids. As part of their alliance with the Empire of Japan, Germany provided design schematics and a single Me 163 to the country; this led to the development of the Mitsubishi J8M. By the end of the conflict, roughly 370 Komets had been completed, most of which were being used operationally. Some of the aircraft's shortcomings were never addressed, and it was less effective in combat than predicted. Capable of a maximum of 7.5 minutes of powered flight, its range fell short of projections and greatly limited its potential. Efforts to improve the aircraft were made, but many of these did not see actual combat due to the sustained advance of the Allied powers into Germany in 1945.
After being introduced into service the Me 163 was credited with the destruction of between 9 and 18 Allied aircraft against 10 losses. Aside from combat losses, numerous Me 163 pilots were killed upon takeoff or during testing and training flights. This high loss rate was, at least partially, a result of the later models' use of rocket propellant which was not only highly volatile but also corrosive and hazardous to humans. One noteworthy fatality was that of Josef Pöhs, a German fighter ace and Oberleutnant in the Luftwaffe, who was killed in 1943 through exposure to T-Stoff in combination with injuries sustained during a failed takeoff that ruptured a fuel line. Besides Nazi Germany, no nation ever made operational use of the Me 163; the only other operational rocket-powered aircraft was the Japanese Yokosuka MXY-7 Ohka which was a manned flying bomb.
Development
Early work by Alexander Lippisch
The world's first piloted rocket flights were carried out by the German vehicle manufacturer Opel RAK. The first flight of such an aircraft, a rocket-modified glider designed by Alexander Lippisch, took place at Wasserkuppe Mountain on 11 June 1928. Two black powder rockets, designed by Friedrich Wilhelm Sander, were fitted to the aircraft’s rear. Due to the use of a forward canard arrangement, Lippisch named the glider "Ente", German for duck. After a failed first attempt, one rocket finally ignited as intended and the Ente lifted off, test pilot Fritz Stamer flying it for before making a controlled landing. Another flight using both rockets did not go as planned, as one of the two rockets exploded; the damaged aircraft took off due to the active intact rocket, but the control surfaces did not work, and with much of it aflame Stamer barely survived while fire destroyed the Ente.After the Ente's loss, Fritz von Opel commissioned a dedicated rocket plane, the Opel RAK.1. It was designed by Julius Hatry, another early Wasserkuppe pioneer, and also equipped with Friedrich Sander's Opel RAK rockets. The first public flight of a rocket plane took place in Frankfurt on 30 September 1929. Lippisch also continued his independent design work over the following decades, and in particular using rocketry, leading eventually to the Me 163.
Background
During 1937, work on what would become the Me 163 commenced, the initial work was conducted under the aegis of the Deutsche Forschungsanstalt für Segelflug —the German Institute for the study of 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 that Lippisch felt would cause problems at high speed. Lippisch changed the system of vertical stabilization for the DFS 194's airframe from the earlier DFS 39's wingtip rudders, to a conventional vertical stabilizer at the rear of the aircraft. The design included a number of features from its origins as a glider, notably a skid used for landings, which could be retracted into the aircraft's keel in flight. For takeoff, a pair of wheels, each mounted onto the ends of a specially designed cross-axle, were needed due to the weight of the fuel, but the wheels, forming a takeoff dolly under the landing skid, were released shortly after takeoff.The designers planned to use the forthcoming Walter R-1-203 cold engine of thrust, which like the self-contained Walter HWK 109-500 Starthilfe RATO booster rocket unit, used a monopropellant consisting of stabilized HTP known by the name T-Stoff. Heinkel had also been working with Hellmuth Walter on his rocket engines, mounting them in the He 112R's tail for testing – this was done in competition with Wernher von Braun's bi-propellant, alcohol/LOX-fed rocket motors, also with the He 112 as a test airframe – and with the Walter catalyzed HTP propulsion format for the first purpose-designed, liquid-fueled 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 monopropellant fuel's high reactivity with organic matter would be too dangerous in a wooden fuselage structure. Work continued under the code name Projekt X.
The division of work between DFS and Heinkel led to problems, notably that DFS seemed incapable of building even a prototype fuselage. Lippisch eventually asked to leave DFS and join Messerschmitt instead. On 2 January 1939, Lippisch moved with his team and the partly completed DFS 194 to the Messerschmitt works at Augsburg. The delays caused by this move allowed the engine development to catch up. Once at Messerschmitt, the team decided to abandon the propeller-powered version and move directly to rocket-power. The airframe was completed in Augsburg and in early 1940 was shipped to receive its engine at Peenemünde-West, one of the quartet of Erprobungsstelle-designated military aviation test facilities of the Reich. Although the engine proved to be extremely unreliable, the aircraft had excellent performance, reaching a speed of in one test.
It is important to note that the wing sweep incorporated in the design stemmed from its tailless nature and the need to balance centre of gravity and centre of lift positions for stability purposes. The sweep in both the Me 163 and Me 262 stemmed from these CG and CL issues, not from high speed aerodynamic requirements.
In the Me 163B and -C subtypes, a ram-air turbine was installed on the extreme nose of the fuselage that, along with a backup lead–acid battery inside the fuselage that it charged, provided electrical power for various pieces of onboard equipment. Such apparatus included the radio, reflector gunsight, direction finder, compass, firing circuits for the twin cannons, as well as some of the lighting for the cockpit instrumentation. Limited battery capacity made the electrical generator necessary.
The airspeed indicator averaged readings from two sources: the pitot tube on the leading edge of the port wing, and a small pitot inlet in the nose, just above the top edge of the underskid channel. There was a further tapping-off of pressure-ducted air from the pitot tube which also provided the rate of climb indicator with its source.
The resistance group around the Austrian priest Heinrich Maier had contacts with the Heinkelwerke in Jenbach in Tyrol, where important components for the Me 163 were also produced. The group supplied location sketches of the production facilities to the Allies, thus greatly aiding Allied bombers in carrying out targeted air strikes against them.
Me 163A
In early 1941, production of a prototype series, known as the Me 163, began. Secrecy was such that the RLM's "GL/C" airframe number, 8-163, was actually that of the earlier Messerschmitt Bf 163. Three Bf 163-prototypes had been built, and it was thought that foreign intelligence services would conclude any reference to the number "163" was for that earlier design. During May 1941, the first prototype Me 163A, V4, was shipped to Peenemünde to receive the HWK RII-203 engine. By 2 October 1941, Me 163A V4, bearing the radio call sign letters, or Stammkennzeichen, "KE+SW", set a new world speed record of, piloted by Heini Dittmar, with no apparent damage to the aircraft during the attempt. Some postwar aviation history publications stated that the Me 163A V3 was thought to have set the record. The record figure would not be officially surpassed until after the war, specifically by the American Douglas D-558-1 on 20 August 1947. Ten Me 163As were built for pilot training and further tests; these were unarmed.During testing of the prototype aircraft, the jettisonable undercarriage presented a serious problem. The original dollies possessed well-sprung independent suspension for each wheel, and as the aircraft took off, the large springs rebounded and threw the dolly upward, striking the aircraft. In comparison, the production aircraft used much simpler, crossbeam-axled dollies, and relied on the landing skid's oleo-pneumatic strut to absorb ground-running impacts during the takeoff run, as well as to absorb the shock of landing. If the hydraulic cylinder was malfunctioning, or the skid mistakenly left during a landing procedure in the "locked and lowered" position, the impact of a hard touchdown on the skid could cause back injuries to the pilot.
Once on the ground, the aircraft had to be retrieved by a Scheuch-Schlepper, a converted small agricultural vehicle, originally based on the concept of the two-wheel tractor, carrying a detachable third swiveling wheel at the extreme rear of its design for stability in normal use—this swiveling third wheel was replaced with a pivoting, special retrieval trailer that rolled on a pair of short, triple-wheeled continuous track setups for military service wherever the Komet was based. This retrieval trailer usually possessed twin trailing lifting arms, that lifted the stationary aircraft off the ground from under each wing whenever it was not already on its twin-wheel dolly main gear, as when the aircraft had landed on its ventral skid and tailwheel after a mission. Another form of trailer, known also to have been trialled with the later B-series examples, was tried during the Komets test phase, which used a pair of sausage-shaped air bags in place of the lifting arms and could also be towed by the Scheuch-Schlepper tractor, inflating the air bags to lift the aircraft. The three-wheeled Scheuch-Schlepper tractor used for the task was originally meant for farm use, but such a vehicle with a specialized trailer—which could also lift the Me 163's airframe completely clear of the ground to effect the recovery as a normal part of the Me 163's intended use—was required as the Komet was unpowered after exhausting its rocket propellants, and lacked main wheels after landing, from the jettisoning of its "dolly" main gear at takeoff.
During flight testing, the superior gliding capability of the Komet proved detrimental to safe landing. As the now un-powered aircraft completed its final descent, it could rise back into the air with the slightest updraft. Since the approach was unpowered, there was no opportunity to make another landing pass. For production models, a set of landing flaps allowed somewhat more controlled landings. This issue remained a problem throughout the program. Nevertheless, the overall performance was tremendous, and plans were made to put Me 163 squadrons all over Germany in around any potential target. However, while the development of an operational version was encouraged, the Me 163 programme was not assigned the highest priority due to competition from other projects; this lack of focus protracted its development.