HEINKEL’S HE 176, THE FIRST REAL ROCKET PLANE

Whilst conducting the He 112 rocket plane tests at Neuhardenberg, Heinkel and the RLM decide to continue the development of a rocket plane interceptor. A secret

department at the Heinkel factory at Rostock-Marienehe is established to pursue this work. Whereas the rocket propelled He 112s were modifications of an existing type of airplane, the new machine is developed from the start as a true rocket plane. It is called the Heinkel He 176. Until recently it was unclear what the original prototype, the He 176 Yl, looked like, and many books and websites include drawings of the proposed operational successor rather than the actual flying prototype (the fact that this improved version was also designated He 176 obviously caused the confusion). A recently discovered picture of the He 176 VI indicates a configuration optimized for high speed flights: a tiny plane with a bullet-shaped fuselage and extremely thin, razor sharp wings in order to minimize aerodynamic drag. The cockpit is completely enclosed within the fuselage, with a flush upper glazing that can be removed for the pilot to gain entry to the plane. The picture shows two retractable main wheels and a fixed nose wheel that was fitted only for the initial taxi tests; for flights the plane was to land using the two main wheels and its tail.

The He 176 Yl has a Walter HWK RI-203 engine that uses the decomposition of hydrogen peroxide, as with the Walter engine for the He 112, but it is more powerful because the propellant is pumped into the engine rather than being pushed in (with a lesser force) by compressed air. Its maximum thrust is about 6,000 Newton, double that of the engine of the He 112. A second version of the design, the He 176 V2, will use an even more powerful von Braun engine to achieve the objective of a speed of

1,0 km per hour (620 miles per hour). To break speed records, the high thrust of the engine will be combined with a very lightweight fuselage and wing structure. In order to minimize the size of the cockpit, it is tailored closely around Erich Warsitz, the designated test pilot. It is so cramped that he can’t even bend his elbows, and the controls that are to be operated by a particular hand have to be put on the opposite sides of the cockpit! To increase the stability of the plane, the wings have a positive dihedral. The design is quite a step in technology. The propellant tanks for the 82% hydrogen peroxide, for instance, are integrated into the thin elliptical wings and thus require to be welded by using a new process. In order to be able to handle the high accelerations, and also to minimize the frontal area of the cockpit and thus air drag, the pilot adopts an unconventional reclined position. There is no canopy bubble, so the entire nose section is made of Plexiglas for the requisite visibility. At the high speeds the He 176 is to fly, even the smallest movement of the aerodynamic control surfaces will have a big effect (because the generated lift forces are a function of the square of the velocity of the air flow) so these surfaces are kept small. However, at take-off and landing the pilot will have to make large movements with the stick and rudder pedals to produce some steering effect from the small rudder, elevators and ailerons. The sensitivity of these controls had therefore to be adjusted by the pilot to achieve sufficient control at all speeds. With a wingspan of 5 meters (16 feet) and a fuselage length of 5.5 meters (18 feet), the He 176 is very small: it would fit inside a modest living room. Looking at the picture of the tiny plane, you have to admire the bravery of Warsitz for volunteering to fly something so experimental which had such a dangerous engine in such a small package.

If anything were to go wrong in flight, even baihng out was going to be a novel experience. Jumping out of the cockpit in the traditional manner was expected to be extremely difficult at high speeds, if not impossible because the force of the air drag would be strong enough to rip the pilot’s head off. Therefore the whole cockpit and nose formed a separate section that could be ejected from the rest of the plane by compressed air. A braking parachute would then slow it down sufficiently to enable the pilot to get out and land using his own parachute. Wooden mockups of the nose section with a dummy pilot inside (with weight distribution and body measurements reflecting those of Warsitz) were dropped from an He 111 bomber, and established that Warsitz would probably survive a parachute landing inside the cockpit if he did not manage to get out, and even without serious injury if he were lucky enough to set down on soft soil.

The first tests are performed by placing the actual prototype inside the huge wind tunnel of the Gottingen Test Institute. Once complete, the prototype is moved to the Luftwaffe area of Peenemiinde which offers more secrecy than the Heinkel factory. Taxi trials in which the He 176 prototype is towed at speeds up to 155 km per hour (96 miles per hour) behind a 7.6 liter Mercedes car prove to be pretty useless, as the velocity is too low for the small rudder to become effective. Taxi runs are therefore continued on the plane’s own rocket thrust, but all too often the wings hit the ground on the uneven grass airfield. Metal bumpers are therefore installed on the wingtips to prevent them from being damaged; something that can also be seen on the picture of the nose-wheeled He 176 VI. The tests show that the rudder only starts to be useful near the He 176’s take-off speed, making it necessary to steer using the wheel brakes for most of the take-off run. As this costs a lot of energy and makes it difficult for the plane to get up to the desired speed, a rudder is installed in the engine’s nozzle (this solution had also been implemented in the He 112 fitted with the Walter engine, for the same reason).

The first short rocket propelled hops into the air are made in March 1939 with very limited amounts of propellant in the aircraft for safety reasons. Over a hundred of these test runs are performed, with the plane getting no higher than 20 meters (70 feet) over a distance of about 100 meters (330 feet). Modifications are made to the

plane. New concrete runways are built. In May 1939 a demo-hop is made for RLM officials including Ernst Udet, head of technical development for the Luftwaffe, and Erhard Milch, head of the RLM. The demonstration does not have the effect the He 176 team expects. Quite the opposite: Udet deems the plane to be too unstable, too small and too dangerous, and he grounds it! Nevertheless Warsitz talks the visitors into allowing the team to conduct the test flights. On 20 June the team prepares the He 176 for its real maiden flight. To prevent anyone from blocking the attempt, and to limit the repercussions of a failure, no officials are invited or notified – not even Heinkel; Warsitz assumes full responsibility for the historic flight. After take-off he quickly achieves a speed of 750 km per hour (470 miles per hour), then he makes a steep ascent and continues to fly a circuit at 800 km per hour (500 miles per hour): faster than any previous plane. After the 1 minute’s worth of propellant is consumed, he glides back and makes a safe landing. Apart from the expected sensitivity to the controls, the He 176 proves to be a fine flying machine. News about the successful flight quickly gets out and the next day Warsitz performs a demonstration flight for Heinkel, Udet and miscellaneous other officials. On 3 July even Adolf Hitler and Hermann Goring, chief of the Luftwaffe, watch in amazement as it flies at a special air show of new Luftwaffe planes at Roggentin airfield. Coming in to land, Warsitz shuts off the engine too soon and almost flies into a brick wall; a last-second restart of the engine makes the plane suddenly rise some 50 meters and hop over the wall prior to landing safely. Most of the spectators think this spectacular maneuver is a part of the demonstration. At the same show, an impressive demonstration is made of the Walter take-off assist rocket pod with a pair of He 111 bombers, one with two 4,900 Newton thrust Walter RI-200 rockets and the other without. After starting at the same moment, by the time the standard He 111 leaves the ground the assisted one is already boosted to 200 meters (660 feet) altitude by the powerful Walter engines! The Walter rocket pods, which are dropped after burn out, deploy parachutes and are recovered for reuse, soon become standard equipment in the Luftwaffe’s bomber squadrons in the form of the RI-202.

The more powerful He 176 V2 fitted with a von Braun engine is never built; on 12 September 1939 Hitler issues an order to halt all development work on weapons that cannot be made operational within one year, which is the time he expected Germany would to need to successfully conclude the recently started war. The He 176 V2 was to have had a rocket thrust exceeding the weight of the plane so that it could lift off vertically. It might even have been able to attain the magic number of 1,000 km per hour (620 miles per hour). Hitler’s order also ended the test flights of the He 178, the world’s first jet plane that was also flown by Warsitz. The He 176 VI was put into a sealed container and sent to the Aviation Museum in BerUn to be displayed after the war but it was destroyed by an air raid in 1943. Sadly, no pictures or movies of the historic He 176 flights are available; according to Warsitz the Soviets obtained all the documentation when they captured Peenemunde at the end of the war and they kept everything secret.