The Berlin scientific balloon flights (Berliner wissenschaftliche Luftfahrten) were a series of 65 manned and 29 unmanned balloon flights carried out between 1888 and 1899 by the German Society for the Promotion of Aeronautics to investigate the atmosphere above the planetary boundary layer. The flights were organized by Richard Aßmann, Professor at the Meteorological Institute of Berlin, who also developed the most important of the measurement instruments employed by them. The execution lay primarily in the hands of the military airship pilot Hans Groß and the meteorologist Arthur Berson. In 1894, Berson flew with the balloon Phönix to a height of 9155 meters, the highest that any human had flown until then.
Background
Meteorology in the 1880s In the course of the 19th century, meteorology was no longer solely an observational and descriptive science. On the basis of classical physics, especially particle and continuum mechanics and mechanical thermodynamics, it was developed into a science of measurement and calculation, to a physics of the atmosphere. The basics of atmospheric thermodynamics were already worked out in the 1880s, but the description of the dynamics was through simple approaches such as Buys Ballot's Law.K.-H. Bernhardt, pg. 58.
Scientific weather forecasting was still in its infancy in the late 19th century. This was on one hand due to incomplete knowledge of atmospheric processes, and on the other due to a lack of reliable observations. Observations were almost all made from land, while there were only vague ideas about the vertical structure of the atmosphere.K.-H. Bernhardt, pg. 60.
Early scientific ballooning The potential of balloons for research on the upper atmosphere was recognized early on. On the first flight of a gas balloon on 1 December 1783, its inventor Jacques Charles brought along a thermometer and a barometer along with him.R. Aßmann: Allgemeine Uebersicht über die Entwickelung der wissenschaftlichen Luftschiffahrt bis zum Jahre 1887. In the following year, the chemist Antoine Laurent de Lavoisier established on behalf of the Académie française a program for scientific aviation, that was eventually not realized. In Germany, it was Georg Christoph Lichtenberg, who first addressed the issue of research into the atmosphere in his writings on the use of balloons.G. C. Lichtenberg: Vermischte Nachrichten über die aërostatischen Maschinen.
The first balloon flight with the aim of making meteorological observations was undertaken on 30 November 1784 by the American medical doctor John Jeffries together with the professional balloonist Jean-Pierre Blanchard.R. Aßmann: Allgemeine Uebersicht über die Entwickelung der wissenschaftlichen Luftschiffahrt bis zum Jahre 1887. Some of the first systematic investigations into the upper atmosphere was performed between 1862 and 1866 by the English meteorologist and important pioneer aerologist James Glaisher. On 28 balloon flights, he measured the temperature, air pressure, humidity and the wind speed up to an altitude of almost 9000 meters.R. Aßmann: Allgemeine Uebersicht über die Entwickelung der wissenschaftlichen Luftschiffahrt bis zum Jahre 1887.R. Aßmann: Die Beobachtungen, das Instrumentarium und dessen Verwendung bei den wissenschaftlichen Luftfahrten bis zum Jahre 1887 und Kritik der bei denselben gewonnenen Ergebnisse. As his instruments were not sufficiently protected from solar radiation, and as he placed them inside the basket, his temperature measurements were particularly high and affected by errors. In the following years, most scientific balloon flights were made by French scientists such as Camille Flammarion, Gaston Tissandier and Wilfrid de Fonvielle. However, the investigation of the upper atmosphere remained isolated endeavors of individual researchers until the 1890s.S. Höhler, pg. 211.
Developments in Berlin
In 1885, Wilhelm von Bezold was appointed to the newly established Chair for Meteorology at the Friedrich-Wilhelms-Universität, and as the director of the Prussian Meteorological Institute, both in Berlin.H. Steinhagen: Der Wettermann. He profoundly restructured the institute, and hired three scientific commissioners on 1 April 1886, among whom was the physician and meteorologist Richard Aßmann from Magdeburg. Aßmann had been working since 1883 on a measurement device that could measure the air temperature accurately in spite of the disruptive effect of solar radiation. In 1887, Aßmann joined the Society for Promotion of Aeronautics (founded in 1881) together with other early Berlin meteorologists, where he got to know the engineer Hans Bartsch von Sigsfeld. Sigsfeld had worked on the same problem for the aviation department (established in 1884) of the Railway Troops of the Prussian Army. Together, they developed the Aßmann aspiration psychrometer, which excluded the influence of sunlight through shielding and permanent ventilation.R. Aßmann: Die Arbeitsmethoden der Aerologischen Observatorien.
The temperature profiles made by Glaisher had long stood as secure knowledge, although there had been isolated doubts about their validity, as they conflicted with theoretical predictions. Aßmann and Sigsfeld saw now the possibility to critically test Glaisher's results with their new instrument.
On 2 June 1888, Wilhelm von Bezold made a speech at the 100th meeting of the German Society for the Promotion of Aviation on "The Meaning of Aviation to Meteorology".W. v. In this speech, he sketched a program of cooperation between meteorology and aviation in the investigation of the upper atmosphere, that was well received by members of the Society. Its implementation dominated the activities of the Society for more than a decade. Already on 23 June 1888, Sigsfeld's balloon Herder made its first trip.
Financing Significant capital was required to undertake this endeavor. Through donations from Society members (Rudolph Hertzog, Werner von Siemens, Otto Lilienthal), the tethered balloon Meteor was purchased. The Royal Prussian Academy of Sciences made a one-time grant of 2000 Marks. Several private citizens (Hans Bartsch von Sigsfeld, Kurt Killisch-Horn (1856–1915), Patrick Young Alexander) put their private balloons at the disposal of the project. Nonetheless, the Society was not in a position to raise the funds to build and maintain a suitable balloon. Subsequently, a "Committee for the Organization of Scientific Flights" was set up in mid-1892, composed of Richard Aßmann, Wilhelm von Bezold, Hermann von Helmholtz, Werner von Siemens, Wilhelm Foerster, August Kundt and Paul Güßfeldt. The committee made an appeal to Kaiser Wilhelm II, which was supported by the Academy of Sciences.R. Aßmann: Die Entwickelung der neueren wissenschaftlichen Luftfahrten. The Kaiser granted the request of 50 thousand Marks for the building and operation of the balloon Humboldt from his "Allerhöchsten Dispositionsfonds". After the crash-landing of the Humboldt, he granted a further 32 thousand Marks for the building of the Phönix. To finance additional flights, and for the publication of the scientific results, a renewed application was made in 1895, for which 20,400 Marks were paid. In 1897, the publisher Georg Büxenstein donated a thousand Marks for the building of the recording balloon Cirrus II.
Strong support for the project also came from the Prussian military, which had a pronounced interest in the military use of the skies. Officers of the Luftschifferabteilung undertook in most cases the piloting of the balloons. The meteorologists were often allowed to take part in military training flights. Premierleutnant (senior lieutenant) Groß was intermittently released from his official duties and responsible for the construction of the balloons used for the main flights.H. Groß: Das Ballonmaterial.
Participants
The organizer of the Berlin scientific flights was Richard Aßmann. In addition to his position at the Meteorological Institute, he was also the chairman of the Society for Promotion of Aviation from the beginning of 1889.H. Stade: 40 Jahre Berliner Verein für Luftschiffahrt, Berlin 1921, pg. 12. Aßmann took care to obtain excellent instruments and equipment. As leader of the project, he only participated personally in three of the manned flights.
His closest colleague in the Meteorological Institute since 1889 was Arthur Berson, who took part in 50 of the 65 manned flights. On 31 flights, Berson served as the primary observer, and on 9 as balloon pilot, and for 10 solo flights he played both roles. Berson also played a great part in the scientific analysis of the measurement data.
The Premierleutnant (senior lieutenant) of the Berliner Luftschifferabteilung, Hans Groß, was the builder of the gas balloons used, and in 32 flights as pilot, he played an important role in the preparation and execution of the flights. His steady improvements to the available balloon technology, such as the adoption of a rip-device to quickly release the filling gas that is still used almost unchanged by contemporary gas balloons, made the potentially risky endeavor much safer.
Alongside Berson was also Reinhard Süring, who was later the director of the Meteorological and Magnetic Observatory at Potsdam. He served as scientific observer (10 flights), pilot (1 flight), and went on three solo flights. As observer, he flew with Otto Baschin (five flights) Richard Börnstein (three), Victor Kremser (two), Hans Bartsch von Sigsfeld (with whom he also flew once as pilot), and Edmund Köbke, as well as once each with Hermann Stade (1867–1932), Börnstein's assistant Becker, the physician Braehmer and Abbott Lawrence Rotch, the director of the Blue Hill Meteorological Observatory in Boston.
Other participants were the professional pilots Richard Opitz (1855–1892) and Stanley Spencer, the British aviation pioneer Patrick Young Alexander, and a series of military balloonists such as Major Stephan von Nieber (1855–1920), the commander of the Luftschifferabteilung, and Richard von Kehler.
Technical equipment
Balloons
Sixteen different balloons were used for the 65 manned balloon flights. These ranged from the balloon Falke, which had a gas volume of 290 cubic meters and was used as the "bad weather balloon" when strong winds or bad weather made it impossible to use the larger balloons, to the 3000 cubic meter Majestic of the Briton, Patrick Alexander. About three-quarters of the flights were made on the large balloons M. W., Humboldt, Phönix, Sportpark Friedenau I and Sportpark Friedenau II. The gas used for lifting was hydrogen or the cheaper coal gas, or frequently a mixture of the two.
The balloon Phönix was of special significance, as it was especially constructed by Groß for scientific flights. It had enough lifting power to make high-altitude flights possible.Nach Süring (Wissenschaftliche Ballonfahrten, In: Bröckelmann (ed. Its hull was built from two layers of rubberized and vulcanized cotton fabric. It contained two valves of different sizes: the smaller was to allow the release of filling-gas during manoeuvres in flight, while the larger was to empty the balloon after landing. In response to the crash-landing of the Humboldt after its sixth flight, Groß fitted the Phönix with a newly developed "Reißbahn" (rip-track), that was stuck to the rest of the hull before the start of the flight. By pulling on the Reißbahn, the balloon pilot could open up the balloon hull wide, to allow a rapid deflation without causing it to be destroyed in the process. Additionally, the balloon's fabric was regularly impregnated with a 10% solution of calcium chloride, to make it electrically conductive and thus prevent electrical sparking due to electrostatic charging, following a suggestion from Bartsch von Sigsfeld.H. Groß: Das Ballonmaterial.