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The Heinkel He 176 was a German experimental rocket-powered aircraft. It was the world's first aircraft to be propelled solely by a liquid-fueled rocket, making its first powered flight on 20 June 1939 with Erich Warsitz at the controls.
The He 176 was developed as a private venture by the Heinkel company in accordance with director Ernst Heinkel's emphasis on developing technology for high-speed flight. Work on the project began in 1936 after testing with a modified He 72 and a pair of He 112s had shown rocket propulsion to have some viability. The He 176 was purpose-built to harness this propulsion, rather than a modification of existing piston engined-types. The resulting aircraft, largely composed of wood, was of relatively simple build in some aspects, and relatively compact. It incorporated some novel concepts, such as an unconventional reclined seating position for the pilot and a unique jettisonable nose escape system for emergencies. In December 1937 the aircraft was officially designated He 176.
On 12 September 1939, the He 176 project was ordered to be cancelled, apparently due to the aircraft's unimpressive size and performance. However, the aircraft did provide "proof of concept" for rocket propulsion and high speed flight in general; lessons and designs cues were incorporated into subsequent aircraft such as the Heinkel He 280 prototype jet fighter and the Messerschmitt Me 163 rocket interceptor. The prototype itself along with most documentation related to the He 176 had been destroyed by the end of the war. Warsitz considered that some material may have entered the Soviet/Russian archives. The often-quoted performance data of the aircraft, such as its speed reaching 750 km/h, or 800 km/h, is drawn from Warsitz's account, and are usually not based on sound documents. Only two true pictures of the He 176 have survived, probably taken in Peenemünde during testing.
Design and development
Background
left|thumb|250px|Opel RAK.1, world's first public flight of a rocket-powered aircraft on September 30, 1929, piloted by [[Fritz von Opel]]
During the 1920s, German daredevils and inventors had experimented with the use of solid-fuel rockets to propel various vehicles, such as cars, motorcycles, railway carriages, snow sleds, and, by 1929, aircraft such as Alexander Lippisch's Ente and Fritz von Opel's RAK.1. Solid-fuel rockets, however, have major disadvantages when used for aircraft propulsion, as their thrust cannot be throttled, and the engines cannot be shut down while fuel remains.
In the mid 1930s, the aerospace engineer Wernher von Braun and his rocketry team working at Peenemünde investigated the use of liquid-fuelled rockets for powering aircraft. The German aircraft designer Ernst Heinkel became an enthusiastic supporter of their efforts, initially supplying a He 72 and later a pair of He 112s to support these experiments. During early 1937, one of these aircraft was flown with its piston engine shut down during flight, propelled by rocket power alone. At the same time, Hellmuth Walter's experiments into hydrogen peroxide monopropellant-based rockets were leading towards light and simple rockets that appeared well-suited for aircraft installation, although at the price of considerable danger and limited endurance.
The experimental flights of the He 112 had been subject to the close attention of the Reichsluftfahrtministerium (RLM) (the German Reich Aviation Ministry), which had become interested in the potential for a rocket-propelled interceptor aircraft. Heinkel decided to establish a secret department at its Rostock facility to pursue such endeavours; work commenced as early as 1936. Unlike the preceding He 112, the design team wanted to produce an aircraft purpose-built to harness this new form of propulsion, thus achieving superior performance from it; from this effort the He 176 emerged.
Design
The basic design of the He 176 was sketched out during the Neuhardenberg rocket motor and booster tests. In 1936, the RLM awarded Heinkel the contract to build the world's first rocket aircraft. It was decided to tailor-build the aircraft to specifically fit the test pilot Erich Warsitz, minimising the size of the cockpit, along with the rest of the aircraft, thus making the aircraft as lightweight as humanly possible. The resulting cockpit was so cramped that the pilot could not even flex his elbows, and some controls were placed in inconvenient positions. Due to the high speed range that the He 176 was designed to encounter, the sensitivity of these controls had to be adjusted multiple times throughout the flight for the pilot to maintain sufficient control. A crude plexiglas glazed section was removable so that the pilot could enter the aircraft. The undercarriage was a combination of conventional and tricycle gear designs, for which the main gear's struts were intended to retract rearwards into the fuselage while the aerodynamically faired nose wheel and strut were fixed. Unmanned scale mockups of the nose section were flight tested from a Heinkel He 111 bomber with positive results. The fuel used was 82% hydrogen peroxide.
Flight testing and cancellation
On 20 June 1939, the He 176 performed its maiden flight piloted by Warsitz, the occasion being the first manned rocket flight in the world. Warsitz later described the flight: "On quite another heading from that originally intended she leapt into the air and flew with a yaw and a wobble. I kept her close to the ground while gaining speed, then pulled back gently on the control stick for rapid ascent. I was at 750 kms/hr and without any loss in speed the machine shot skywards at an angle somewhere between vertical and 45°. She was enormously sensitive to the controls...Everything turned out wonderfully, however, and it was a relief to fly round the northern tip of Usedom Island without a sound at 800 kms/hr. I banked sharp left again to straighten up for the airstrip, losing such speed and altitude as I could, and during this steep turn the rocket died as the tanks dried up. The abrupt loss of speed hurled me forward in my restraint straps. I pressed the stick forward, hissed rapidly over the Penne and came in at 500 kms/hr. I crossed the airfield boundary and after several prescribed little bounces the machine came to a stop."
Following the initial test flight, the aircraft received alterations; apparently the fixed nose wheel was removed at this point as the design team intended to use only the two main wheels and the tail for regular landings.
The RLM's unfavourable attitude towards the aircraft was a major contributor to Heinkel's decision to reduce his involvement in rocket propulsion efforts. On 12 September 1939, the discontinuation of the He 176 test programme was officially ordered, apparently due to dissatisfaction with its performance and size. Only the one aircraft was ever completed; after its retirement, it was put on static display at the Berlin Air Museum. It was destroyed by an Allied bombing raid during 1943. It was powered by a similar rocket engine that was actually a further development of the unit that had powered the He 176.
Specifications (He 176 V1)
thumb|300px|Heinkel He 176 V1 with main gear retracted