Writing in 1926 Albert Einstein made a discovery of another’s scientist’s work which he thought was equal to his own accomplishments. “The history of scientific and technical discovery teaches us that the human race is poor in independent thinking and creative imagination. Even when the external and scientific requirements for the birth of an idea have long been there, it generally needs an external stimulus to make it happen” man has to stumble right up against the thing before the idea comes.”

The object of Einstein’s admiration was the Flettner rotor ship the Baden-Baden, a ship solely propelled by two spinning cylinders looming above the deck. The ship, Einstein wrote, “is just now filling the entire world with amazement.” The February, 1925 issue of Popular Science Monthly agreed, noting “the world gasped in amazement” at the launch of the ship. 

In the August issue the following year marking the entrance of the ship into the New York harbor with its 31-year-old inventor Anton Flettner on board the magazine imagined a future with “Billions of horsepower absolutely free!” powered by the wind or “blue coal” as Flettner called it. The following month’s issue ran detailed plans to build a model rotor ship.

The rotor ship was hailed as the greatest leap in maritime technology since the invention of the steam engine. The twin rotors of the Baden-Baden stood 50 feet high and were nine feet in diameter. The pair were spun at 140 rpm by a 50 horsepower electric motor, either clockwise or counterclockwise depending upon the wind. As Einstein explained in an essay the rotors worked due to the Magnus effect, a property common to all spinning bodies like cannonballs or curve balls moving over home plate. The act of spinning produces a variation in velocity on opposite sides as it moves through a fluid like water or air. The variable velocity produces varying pressures driving the spinning object which drives the object in a different direction than a nonspinning object would move under the same conditions. Firmly attached to the ship, the rotors transmitted that force to the ship moving it along the water. 

The simple elegance and the promise of reduced operating costs in fuel and crew caught the public’s and Einstein’s imagination. But even as the Baden-Baden, named after a famous German spa, cruised the waters of New York for the newsreel cameras the future of the Flettner rotor ship was slowly sinking. Skeptical of its usefulness in naval warfare, the German navy pulled its support and funding. Fuel prices for commercial ships were so low that switching to a rotor system was not economical. The crash of 1929 and worldwide Depression was the final blow to the dream. The Baden-Baden was converted back to an ordinary schooner, as was its sister ship the Barbara, a three rotor ship tested by the German navy. The Baden-Baden sank during a storm in 1931. Despite their enthusiasm Einstein’s and the public’s expectations were fruitless. In fact, Einstein had been wrong.

But there was more to the life and work of Anton Flettner. Born in 1885, Flettner achieved early success as the inventor of trim tabs, devices still in use today to control and adjust airplane wings. During World War I he worked for the Graf Zeppelin Company where he developed a system for guiding air to surface missiles. Between the wars in addition to the rotor ships and a rotor assisted airplane that failed worse than the ship, Flettner invented a ventilator still in use today. With the funds from that business he started a helicopter company, making steady advances in the technology. Flettner’s work was so important to the German war effort that he was able to force Heinrich Himmler to have his wife Lydia Fruedenberg Flettner, who was Jewish, taken to the safety of neutral Sweden. Flettner’s partner in the helicopter business was Kurt Hohenemser, who was half Jewish and would have fallen victim to the Holocaust. The Nazis, however, left Hohenemser alone after Flettner convinced them that he was vital to the helicopter production. The company devoted most of its work to spotter helicopters used to observe the position of the enemy forces.

Flettner surrendered to the Allies and after a brief time in a detention camp he was one of the first German scientists relocated to America in Operation Paperclip, the program that also brought Werner von Braun to the United States despite his war crime of exploiting slave labor in producing missiles. After settling in New York, Flettner continued his innovations in helicopter technology for the military. He died in 1961 at the age of 76. His obituary in the New York Times mentioned the rotor ship but his achievements in aerodynamics far overshadowed the ship. 

The rotor ship might have died there, a curiosity of the eccentric 1920s. However, in recent years the rotor ship has been making a tentative comeback. In 2008 a German company launched a four rotor ship. Smaller ships have experimented with rotors. With the advent of strong, lightweight materials, precision and efficient motors, and computer controls to make second to second adjustments in the rotation coupled with the need to reduce the carbon footprint of transportation perhaps Flettner’s rotor ships have a future. Perhaps Einstein was right after all.