Zahlen, bitte! Shortest earth orbit in 84 minutes of the Schuler period
The Schuler period was important for the invention of the gyrocompass: Even Albert Einstein was involved in the development of the ship navigation instrument.
The 84-minute period plays a role in many geodetic calculations, for example as the shortest possible orbital period of a satellite around the earth. If there were a straight tunnel between New York and London, for example, in which a vehicle could move freely without friction and without an engine under the influence of gravity, it would be in New York in 42 minutes and back in London in 84 minutes. The figure known scientifically as the Schuler period played an important role in the development of navigation devices such as the gyrocompass. It owes its development to the daring plan to dive under the North Pole.
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125 years ago, the German art historian and self-proclaimed polar explorer Hermann Anschütz-Kaempfe explored the possibility of reaching the North Pole with a submersible during his last polar voyage for the time being. He had been infected with “polar fever” by the Austrian polar explorer Julius Payer. Payer had taken part in several expeditions and had painted and glorified the ordeals of the expeditions to the North and South Poles in large pictures. Anschütz-Kaempfe set off for Spitsbergen for the first time in 1897. In that year, the Swedish polar explorer Salomon August Andrée's attempt to reach the Pole simply by air with a hydrogen balloon had failed. Anschütz-Kaempfe imagined (PDF file, page 13) that a submersible would surface in open water in the Arctic Ocean and someone would use a 20-meter-high ladder to locate the nearest water point five or six nautical miles away and determine it with a compass.
“The gyroscope, an instrument that indicates with great accuracy any lateral deviation of the ship from the given direction, is now pointed after the compass. The ladder is retracted, the shaft is closed, and the dive can begin…” Hermann Anschütz-Kaempfe wanted to use this simple stop-and-go principle to approach and cross the North Pole. The gyroscope was to be used as a direction indicator underwater to determine the direction if the magnetic compass did not provide any results.
North Pole sailing company founded
To finance his plan, he founded the “Gesellschaft zur drahtlos-unterseeischen Nordpolfahrt” together with the Munich manufacturer Hermann Scholl. By this time, the considerable fortune that Hermann Anschütz had received as the adopted son of Mr. and Mrs. Kaempfe had already dwindled considerably. Undaunted, the talented inventor began constructing gyroscopes in 1903, which he tested on model ships in the Müllerschen Volksbad in Munich and then on pleasure boats in Lake Starnberg. The goal, however, was real diving trips in the North and Baltic Seas with the submarine “Forelle” from the Germania shipyard in Kiel, which belonged to the Krupp Group. The polar explorer concluded a contract with the shipyard for the underwater control of torpedoes.
(Image:Â Manfredgoellner, CC BY-SA 4.0)
Anschütz came closer to his goal when his gyroscope was first used on the harbor steamer “Schleswig” in the Kiel Fjord and later on the small cruiser SMS “Undine” during the calibration of the guns. Anschütz-Kaempfe experienced that his gyroscope was not affected by the gunfire, but had problems with the roll and pitch. The Reichsmarineamt, which supported Anschütz-Kaempfe in his experiments, recommended that the inventor forget his North Pole voyage and improve and patent his invention.
This was done with the patent application for a “gyroscope apparatus” as German Reich Patent (DRP) 182 855 on March 27, 1904. It was not the first patent of its kind, but the first to be registered for the use of a gyroscope on ships. The Dutchmen Marinus van den Bos and Barend Janse had already applied for a patent for a “rotary compass” in 1885, which Siemens bought up but soon had to discontinue production due to its lack of seaworthiness.
Involvement of the cousin brings the gyrocompass breakthrough
After many more attempts, Anschütz & Co KG was entered in the Kiel commercial register in September 1905. Even more importantly, Anschütz-Kaempfe was able to persuade his cousin Max Schuler to join the company. Here, the graduate engineer and physicist developed the mathematical principles for the vibration behavior of a gyroscope, the disturbances of which Anschütz-Kaempfe dealt with in practical experiments. Around 1915, Schuler calculated this period using a hypothetical pendulum with a length of 6371 km corresponding to the Earth's radius and a gravitational field of 9.81 m/s². A pendulum reaching to the center of the earth would swing at 84.4 minutes.
The inventor Anschütz-Kaempfe, who had actually studied for a doctorate in art history, was unable to report on the functioning of his “botched machine” in the language of physics. Today, the geophysical constant he discovered is known as the Schuler period of 84.4 minutes (PDF file).
(Image:Â Stahlkocher, CC BY-SA 3.0)
First suitable gyrocompass in use in the navy
In 1908, the Anschütz company launched the first suitable gyrocompass on the market, which was immediately tested on the SMS “Deutschland” on the orders of Admiral Tirpitz. Anschütz-Kaempfe continued to tinker and in 1909 combined the gyrocompass with the coupling table of the speed measuring system to create the first automatic navigation plotter. The further development of the compass was accelerated with the patent application of June 22, 1911, for the DRP 211 637 three-gyrocompass. It was installed on the battle cruiser SMS Moltke. In merchant shipping, the compass was used on the “Imperator”, the largest ship in the world until 1914.
In December 1914, the AnschĂĽtz company decided to take legal action against a compass patent held by the US American Elmer Ambrose Sperry. Sperry had visited the AnschĂĽtz works in Kiel in 1909 and then presented his gyrocompass. The Imperial Patent Office appointed Albert Einstein from the Prussian Academy of Sciences, who had just moved to Berlin, as an impartial expert. Before publishing his special theory of relativity, Einstein had worked as a third-class technical expert at the Swiss Patent Office in Bern and was therefore familiar with disputes of this kind. He examined both compasses in 1915.
(Image:Â U.S. Navy)
Anschütz won the case and thus the European market, while Sperry dominated the US market. Anschütz-Kaempfe and Einstein became friends, a sailing dinghy was always available for Einstein and a guest apartment was set up as the “Diogenes-Tonne” in Kiel for the retreat from Berlin. Einstein now represented Anschütz as an expert witness in disputes over the artificial horizon developed by Max Schuler for blind flight in air traffic and patented by the Anschütz company in 1916. In 1918, Einstein finally asked for his dismissal as an expert to work with Anschütz-Kaempfe on a new generation of compasses, as Anschütz-Kaempfe was bothered by the fact that the open three-gyro compass could be influenced from the outside.
After many discussions and correspondence with Einstein, he developed the idea of a dual gyroscope, which is mounted in a sphere and sealed airtight so that the gyroscope can rotate without air friction resistance. Anschütz-Kaempfe initially experimented with mercury, but then switched to electrolyte on Einstein's recommendation. The power supply with three-phase current was also discussed, thanks to which the two gyroscopes in the spherical compass rotated at 19800 rpm. Einstein's most important idea was the use of a magnetic ring as a “blowing coil” so that the sphere inside the system always remained centered.
(Image:Â U.S. Navy photo by Yeoman 1st Class J. Thompson/Released)
The jointly developed spherical compass was patented by the Reich Patent Office in 1922 as a “gyroscope apparatus for measuring purposes” under No. 394 667. Einstein received 1% of the sales price of each apparatus; 3% of the license fee when foreign patents were granted. Anschütz transferred Einstein the payments due to him until 1938, when he had long since emigrated to the USA and been expatriated by the National Socialists. Little has changed to this day.
The dive under the North Pole was not undertaken until 1958 by the USA with the nuclear-powered submarine Nautilus and had nothing to do with the record attempts of the early polar explorers, but served as a nuclear deterrent. It was intended to show the Soviet Union that US submarines could surface off the coast at any time.
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