VOL. 23 January ISSUE YEAR 2022

Off the Beaten Track

in Vol. 23 - January Issue - Year 2022
The Duck
A replica of the 
Opel RAK.1

A replica of the Opel RAK.1

rocket engines for supplemental thrust

rocket engines for supplemental thrust

The first attempts to build rocket-propelled aircraft date back to the beginning of the 1900s. The pioneer was German industrialist Fritz von Opel, who attached two rockets under the fuselage of a glider. The rockets were propelled by black powder, fired by a switch in the cockpit and burned consecutively to ensure a longer flight time, each with a burn time of about thirty seconds. The aircraft was slightly over four meters long, with a wingspan of twelve meters. Opel named it the Ente (“Duck” in German). On June 11th 1928 a test pilot flew the glider for 1500 meters.

Opel’s next project was a powered airplane specifically designed to be propelled by rockets. His Opel RAK.1 was 5.41 meters long with a wingspan of 11 meters and powered by sixteen black powder rockets. A large crowd, numerous journalists and film crews, some from the United States, gathered outside of Frankfurt on September 30th 1929 to witness the first test flight. This time Opel personally flew his aircraft instead of relying on a test pilot. He covered a distance of 3.5 km in 75 seconds at an altitude of 30 meters and a speed of about 150 km/h. The original plan was to fly from Frankfurt to Rüsselsheim, but a downward gust of wind caused Opel to make a forced landing after only five of the rockets had burned. Despite this partial setback, the test was considered a huge success. News of Opel’s feat was greeted with enthusiasm around the world and inspired a wave of research and experimentation.
A young Italian inventor and aviation enthusiast named Ettore Cattaneo was closely following Opel’s achievements. With the help of a World War I flying ace, Cattaneo tried to develop a liquid-propelled rocket suitable for an airplane. The project proved too difficult and dangerous. He then turned his attention to improving solid fuel rockets. Together with two professors from the Milan Polytechnic University, Cattaneo designed a rocket fueled by a blend of gunpowder, chlorine and paraffin to be mounted on a glider with six rockets of his own design. On June 25th 1931, he began a series of test flights, gradually increasing the flying time and distance until, three days later, he bettered Opel’s results.
By the end of the decade, it had become obvious that the world was headed towards a new war and interest in rocket-powered aircraft grew. In a demonstration for the German Air Ministry on June 20th 1939, the Heinkel He 176 became the first airplane in the world to be powered by a liquid-propellant rocket engine. Ministry officials were not impressed and the project was abandoned. Towards the end of the war, the Messerschmitt Me 163 Komet fighter plane became the world’s first mass-produced rocket plane. Although it was the first rocket-powered fighter to see combat, difficulty in procuring rocket fuel forced the German Air Force to abandon the Komet in favor of the Messerschmitt Me 262, the world’s first jet engine fighter. Germany gave the drawings of the Komet to its ally Japan, which carried out the first test flight of its Mitsubishi J8M on July 7th 1945. This plane never saw combat, but Japan used about 850 Yokosuka MXY-7 Ohka rocket-powered suicide attack aircraft during the war. In the latter part of the war, the Soviet Union tested the Bereznyak-Isayev BI-1 and the United States mounted rockets on a modified P-51D Mustang, but neither model led to any practical application.
During the Cold War, the Soviet Union developed the Mikoyan-Gurevich I-270 as a rocket-powered interceptor aircraft. In 1947, the United States developed the Bell X-1, the first rocket-powered aircraft to break the sound barrier in level flight. This model led to the X-15, powered by an ammonia and liquid oxygen rocket that allowed it to reach speeds of Mach 6.7 and altitudes of 100 km. The United Kingdom and France joined in the race to develop rocket-powered military aircraft that could also be sold to friendly nations. The most commercially-successful rocket-powered fighter plane was the Lockheed F-104 Starfighter, first developed in 1954. It eventually flew with fifteen air forces, although it had a very poor safety record. It was retired from active military service in 2004.
In modern times rocket-powered airplanes for military use have been eliminated thanks to improved performance by turbojet engines, missiles and radar systems. They remain as race planes or for scientific suborbital flights. Rockets are also used to boost the thrust of jet-propelled or even propeller-powered aircraft.

By Giovanni Gregorat, Contributing Editor MFN