Germany (1937)
Rocket Powered Aircraft – 1 Prototype Built

Prior to, and during the war, the German aviation industry developed a series of operational and prototype aircraft designs. Among the leading new technologies, rocket-powered aircraft were being developed. The concept was initially tested prior to the war on a smaller scale, including limited theoretical tests and prototyping. But further development would lead to the creation of the first rocket-powered aircraft known as the He 176. While it wasn’t accepted for service, it proved that such a concept was feasible and set the stage for the later Me 163 rocket-powered aircraft.

History of Rocket Engine Development in Germany

Following the end of the Great War, Germany was forbidden to have an Air Force. This also included the development of aircraft designs, though this did not stop the Germans from experimenting with new aviation technology. One such new technology was rocket propulsion. One of the first such flights using rocket propulsion occurred in June of 1928, when aviation enthusiast Fritz Stramer took to the sky his rocket-powered glider. Another pioneer in rocket-powered flight occurred at the end of September 1929. A pilot named Fritz von Opel managed to take to the sky in his rocket-powered glider, named Ente (Duck). Von Opel was assisted by another prominent aircraft designer Alexander Martin Lippisch. While technically speaking these were not real rocket-powered flights, given that these gliders did not take to the sky using purely the rocket engine but were towed to altitude. Nevertheless, these flights showed that flight using rocket engines was possible.

Over the following years, Lippisch became quite interested in rocket technology and would join the Deutsche Forschungsinstitut DFS, where he worked as an engineer. There, he developed a series of new glider designs, like the DFS 40. This work would eventually lead to the creation of the Me 163 rocket-powered aircraft. The Junkers Aircraft company also was interested in rocket development as they built and tested rocket take-off boosters. One such engine was ground tested in 1936.

Another stepping stone in rocketry research was the work of Wernher von Braun. In 1932 and 1934 von Braun managed to successfully launch two rockets using liquid-fuel rocket engines. In 1935 he managed to come into contact with Dr. Ernst Heinkel 1935. After von Braun presented his work, Dr. Ernst was highly impressed and promised to provide von Braun with any assistance in his work. For this, he appointed a young and energetic aircraft engineer named Walter Wenzelunzel to assist von Braun. In order to properly test the installation of rocket engines in aircraft designs, a special test center was established at Kummersdorf in 1936.

Dr. Ernst supplied this research team with a few He 112 airframes. The first He 112 was used for ground testing. For this reason, its fuselage was retained while its wings and the original engine were removed. The rocket engine, which ran on a combination of liquid oxygen and alcohol, would be placed in the rear of the fuselage, with the engine nozzle being placed just beneath the tail unit. Von Braun’s team installed the oxygen tanks in front of the cockpit, with the alcohol tank behind the pilot seat. The engine (the sources do not specify its precise designation) could provide a thrust of 1,000 kg (2,200 lb) with an endurance of 30 seconds. During the testing the engine exploded, destroying the aircraft in the process.

Despite this setback, the project went on. By this time, German Army Officials were becoming interested in the project. In order to maintain its secrecy, von Braun and his team were instructed to find a remote auxiliary airfield where these tests could continue to be conducted away from prying eyes. The team, wanting to be close to Berlin, chose a small field at Neuhardenberg, which was covered on most sides by dense forest. Temporary housing, cabins, and tents were quickly set up in 1937 and the work could finally go on.

In 1937 von Braun began close cooperation with another enthusiast of rocket engine development, Helmuth Walter. This cooperation was partly initiated by the German Air Ministry (Reichsluftfahrtministerium RLM) who intended to use the rocket engines for other proposals, like assistance during take-offs. Walter was a young scientist who was highly interested in rocket propulsion. He managed to obtain military funding, which greatly helped in his work. In 1936 he used a Heinkel He 72 to test this engine. In 1937, he even managed to get the attention of the RLM. The RLM formed a Special Propulsion System department (Sondertriebwerke) with the aim of experimenting with rocket engines in the aircraft industry. While this department was mainly focused on developing rocket engines for short take-off assistance, Walter wanted more than that. He intended to develop a strong rocket engine that could replace the standard piston engines of the day. Walter managed to develop such an engine, named Walter TP-1, which was fueled by the so-called ‘T-Stoff’ (hydrogen peroxide) and ‘Z-Stoff’ (water solution of either calcium or sodium permanganate).

Von Braun requested another aircraft which Henkel provided, this was the He 112 V8 (during these trials it received a slightly changed designation V8/U). The test pilot Erich Warsitz managed to take it to the sky using the aircraft’s original piston engine. Warsitz was a crucial pilot for the German early rocket and jet engine development, being heavily involved in testing and helping with the overall design of both the He 176 and He 178. At about 450 meters Warsitz activated the rocket engine, and during the 30 seconds of the engine burn phase, a speed of nearly 400 km/h (or 460 km/h (286 mph) depending on the source) was reached. Due to the dangerous leakage of the engine, the flight had to be aborted, but otherwise, the flight has deemed a success. This He 112 V8 would be returned to Heinkel, but two more aircraft (H7/U and A-03) would be donated to the rocket research program.

After this flight, all further tests were conducted using the Walter TP-1 rocket engine. In contrast to the von Braun engine which used alcohol and liquid oxygen as fuel, Walter’s own engine used hydrogen-peroxide and calcium permanganate as a catalyst. This engine was deemed safer too, which is somewhat ironic given the corrosive and volatile fuel. To avoid accidentally coming into contact with the Walter engine fuel, the pilot had to wear a highly protective suit. If exposed to the corrosive fuel, it caused disintegration without actually burning.

More tests were conducted at this location until the end of 1937, when the research was to be moved to Peenemunde. Due to some delays, the tests on the He 112 continued on from April 1938.

Heinkel’s First Rocket-Powered Aircraft

Following the series of tests on the He 112, some officials from the RLM began showing great interest in the prospect of using a rocket-powered aircraft interceptor. It was originally hoped that this aircraft would be capable of vertical, or nearly vertical take-off. When sufficient altitude was reached, the aircraft was then to make a swift dive on its target, firing a volley of its full weapon load. After this attack run, it was simply to glide away once it was out of fuel, to its base of operation.

The work on the project was conducted under a veil of secrecy and began in 1936 at the Heinkel Rostock-Marienehe work. The following year the first drawings of the He 176 V1 (derived from “Versuchsmuster 1” meaning “Experimental Model”) were completed by Hans Regner. Interestingly the designers set a huge task in front of them, by actually trying to reach a blistering speed of 1000 km/h (620 mp/h). An astonishing and difficult feat to achieve with such a novelty design. This set a number of challenges that had to be overcome. One of them was a proper wing design able to withstand the pressure of such high speed. For this reason, it had to be designed to be flat, at only 90 millimeters thick, with very sharp leading edges. This in turn caused further problems, as this design would cause the aircraft to stall at low speeds. In addition, the installation of wing fuel tanks would be difficult.

In order to make the whole design smaller and thus save weight, the pilot had to be placed in a rather unpleasant semi-recumbent position, with his legs stretched out in front and the pilot’s seat reclined. This was also done to help the pilot better cope with the extreme G-forces that he would be subjected to during the extremely high forward acceleration. The fuselage had a very small diameter of only 0.8 meters (2ft 7in) and was specially designed according to the height of the test pilot, Warsitz.

The construction of the first prototype was undertaken at the Heinkel’s aircraft works in Marienehe. Once the aircraft was completed, it was to be transported to Peenemunde. The aircraft’s testing was conducted under great secrecy and was transported there via military escort in June 1938. Just prior to the actual testing, Warsitz was informed by RLM officials that given the experimental nature of the design, and Warsitz’s valued status as an experienced test pilot, he was advised not to fly it. Warsitz, who was heavily involved in the He 176 design, protested to Air Minister (Reichsluftfahrtministerium) Ernst Udet, who gave him permission to undertake the first flight. After this was settled, there were some delays with the assembly and engine adjustment.

The initial tests were undertaken on the ground. Due to unsuitable terrain and lack of a proper towing vehicle, ground testing proved ineffective. So it was decided to use the aircraft’s own engine for these tests, which were conducted at the end of 1938. Using the He 178’s own engine on the ground presented a new problem, namely the rudder could not provide steering during take-off. As the aircraft had no propellers to generate airflow, steering the aircraft using the rudder on take-off was ineffective, thus the only way to maintain the aircraft’s heading was by using the left and right brakes on the main wheels. This was quite dangerous for the pilot and the aircraft, as an imbalanced braking force could potentially lead to an accident. The result of the initial testing showed that some changes to the overall structural design were needed. For this, the Heinkel crews spent the winter of 1939 modifying the He 178.

First Flights

During the Spring of 1939, a series of small test flights were conducted with the He 178. Somewhat unexpectedly, the Heinkel team was visited by an RLM delegation led by Udet himself. After observing the He 178 on the short flight they were quite impressed, but surprisingly for the Heinkel team, Udet forbade any more flights on it. Mostly due to fear for the pilot’s life. After some delays, Warsitz visited Udet in Berlin and filed a plea that the project should go on. Udet finally accepted this and gave a green light.

While the first official flight of the He 176 was to be conducted under the supervision of many RLM officials, feeling that something might go wrong, Erich Warsitz and Heinkel’s team (without the knowledge of Dr. Erns) decided to perform the flight in secrecy. The date for this was set on the 20th of June, 1939. After a rough take-off, the pilot managed to take the He 176 to the sky. Given the small fuel load, the flight lasted around a minute. Overall, the first test flight was deemed a success. The following day, Udet and his delegation visited the site and observed another test flight.

The Fuhrer Inspects the He 176

A couple of days later Warsitz and Heinkel’s team were informed that any further flights were forbidden. The reason was that Hitler himself became interested in the project and wanted to personally see the aircraft. The He 176 was to be transported to the Rechlin Secret Test Center and shown to many high-ranking members of the Luftwaffe. On the 3rd of July 1939, the aircraft was to be demonstrated to a large delegation including Hitler himself. First, a flight of a He 111 equipped with rocket-assisted take-off was shown to Hitler, which greatly impressed him. Another Heinkel innovative design, the He 178 jet-engine powered aircraft, was also present. While it was not yet capable of taking to the sky it was used for ground testing. Next in the line for inspection was the He 176, after a brief examination of its interior by the delegation, the stage was set for it to take to the sky. The flight initially went well, but the pilot miscalculated and shut down the engine too soon. While still at high speed, he began descending rather rapidly. After several attempts to restart the engine, he finally succeeded, just before hitting the ground. The plane took an almost vertical climb of some 50 meters before the pilot regained control and landed it safely. Hitler and his delegation were under the impression that the pilot performed this maneuver intentionally to demonstrate the aircraft’s potential. For his flight, the pilot was awarded 20,000 Reichsmarks.

The End of the Project

After this exhibit, Heinkel’s team tried to prepare the He 176 for reaching speeds up to 1,000 km/h. Structural analysis of the design, on the other hand, showed that this would not be possible. For this reason, preparation for the construction of a second prototype was underway. It was to be powered by a von Braun rocket engine, which suggested that the aircraft could be launched vertically. This was possible thanks to weight reduction efforts sufficient to enable vertical take-off.

Ultimately the whole project would be canceled. The order was given by Adolf Hilter, who insisted that designs that could not enter production in less than a year, be canceled. Despite Heinkel’s attempt to win over Udet’s support, it went nowhere and the project was officially terminated.

The He 176 V1 was disassembled and transported to the Aviation Museum in Berlin to be exhibited. Sadly it would be later on destroyed in one of many Allied bombing raids. The He 176 V2 was almost complete, but its parts were eventually scrapped. The V3 had also been under construction, but was ultimately abandoned in its early stages.

Technical Characteristics

The He 176 was designed as an all-metal, high-wing rocket-powered experimental reconnaissance aircraft. Its fuselage had a simple circular cross-section design. The wings had an asymmetrical profile and were quite thin. During take-off, there was a significant chance of the wingtips contacting the ground, due to the fuselage’s small diameter and extreme vibrations during take-off. To avoid damaging them, Heinkel engineers added a “U” shaped metal bar under each wingtip as a temporary solution. The wings were also initially to act as fuel tanks, but this feature had to be abandoned on the prototype, and fuel was instead stored behind the cockpit. The tail and rudder design was more or less conventional.

The rocket engine chosen for the He 176 was the Walter RI type. It provided thrust ranging between 45 kg to 500 kg (100 to 1,1100 lb) with an endurance of one minute. Due to the weight issues combined with a relatively weak propulsion unit, the desired speed of 1,000 km/h (620 mph) was never reached. The maximum speed reached by this aircraft differs greatly between sources. For example, D. Nešić mentioned that the maximum speed was only 345 kmh, while authors J. R. Smith and A. L. Kay quoted a figure of 700 kmh. Lastly, the test pilot himself in his own logbook mentioned that he managed to reach a speed of 800 kmh (500 mph).

The landing gear consisted of one front smaller wheel, two larger wheels 700 mm in diameter, and one more to the rear. While the front wheel was fixed the remaining three were completely retractable.

The cockpit provided the pilot with an excellent forward view and was made of plexiglass. Given the experimental nature of this aircraft, great attention was given to pilot safety. As in case of emergency, bailing out of the fast-moving and cramped aircraft was almost impossible. Heinkel engineers designed the entire cockpit section to be jettisonable. The cockpit assembly was connected to the fuselage by four locks which were equipped with small explosive charges. When the pilot was jettisoned from the fuselage his parachute would open automatically and allow him to land safely. This system was tested by using a wooden cockpit containing a dummy pilot. This trial cockpit was then taken to the sky by a He 111 and at sufficient height, it was released. The parachute opened without an issue and it landed on the ground intact. The results of the dummy pilot showed that this system was safe if the cockpit landed on soft ground.

The small size of the cockpit prevented the use of a standard instrument panel, as it would severely affect the pilot’s forward visibility. Instead, the instruments were placed to the left and the right of the pilot. Interestingly, while Heinkel did not intend to arm the aircraft, RLM officials insisted that two machine gun ports be placed beside the pilot. Due to the cramped cockpit interior, the two machine guns had to be placed where the pilots’ side controls were positioned. As this would cause delays and much-needed redesign work, the Heinkel engineers simply placed machine gun ports (without the actual machine guns equipped) and kept the original control units in place. The RLM officials, when visiting the work, were told that these were just temporary measures.

The Only Photograph

Given the secretive nature of the project, RLM officials effectively gathered all films and photos for themselves. All persons involved in the project were also forbidden from taking any pictures. At the war’s end, the Soviets either destroyed or captured these and their final fate is unknown. Sometime after the war, many artists attempted to produce sketches of how the He 176 may have looked. These greatly differed from the original design, but given the lack of information and general obscurity of the He 176, this is understandable.

Conclusion

The He 176 project arose as a collaboration of several different parties. It was heavily influenced by rocket engine testing and development done by von Braun and Walter. Heinkel Flugzeugwerke provided the necessary resources and production capabilities, while test pilot Erich Warsitz provided valuable feedback which guided necessary changes and improvements to the design.

It was a novel idea to use rockets to power aircraft, which offered numerous advantages, such as reaching high speed and altitude very quickly. Given that this project was more or less a Heinkel private venture in the development of new technologies it likewise did not find a place in German military service. It, however, did set the stage for future designs like the Me 163, which actually saw some combat during the war.

He 176 Specifications
Wingspans	4 m / 13 ft 1 in
Length	5 m / 16 ft 4 in
Height	1.4 m / 4 ft 7 in
Wing Area	8 m² / 53 ft²
Engine	Walter RI rocket engine
Empty Weight	1,570 kg / 3,455lbs
Maximum Takeoff Weight	2,000 kg / 4,400 lbs
Maximum Speed	700 km/h / 435 mph
Endurance flight Range	60 seconds
Crew	One Pilot
Armament	None

Gallery

Illustration by Godzilla

Credits

• Written by Marko P.
• Edited by Henry H. & Ed J.
• Illustration by Godzilla

Sources

• D. Nešić (2008), Naoružanje Drugog Svetskog Rata Nemačka Beograd
• M. Griehl (2012) X-Planes German Luftwaffe Prototypes 1930-1945, Frontline Book
• D. Mondey (2006). The Hamlyn Concise Guide To Axis Aircraft OF World War II, Bounty Books.
• D. Donald (1998) German Aircraft Of World War II, Blitz Publisher
• J. R Smith and A. L. Kay (1972) German Aircraft of the Second World War, Putnam
• Jean-Denis G.G. Lepage (2009), Aircraft Of The Luftwaffe 1935-1945, McFarland & Company Inc
• L. Warsitz (2008) The First Jet Pilot The Story of German Test Pilot Erich Warsitz Pen and Sword Aviation