|Fields||physics, inventor, explorer|
|Institutions||Free University of Brussels (now Université Libre de Bruxelles and Vrije Universiteit Brussel)|
He was Auguste Piccard's assistant at the Université Libre de Bruxelles and on 18 August 1932 participated in the record-breaking ascent into the stratosphere to 16,200 m (53,152 ft), launched from Dübendorf, Switzerland. For this he was awarded the Cross of Knight of the Order of Leopold by the Belgian King in 1932.
On 18 August 1934 Cosyns together with his student Nérée van der Elst piloted a balloon to an altitude of 52,952 feet. Following a take off from Hour-Havenne in Belgium, they flew over Germany and Austria before landing near the village of Ženavlje (now in Slovenia). They were unsuccessful in maintaining satisfactory radio communication with ground, but were able to make observations of the currents in the stratosphere as well as investigate the nature of the cosmic rays. They failed to beat the height record, but stated on landing that they were fully satisfied with their discoveries. A large bronze monument in the shape of a balloon was erected in 1997 on the spot of their landing in Ženavlje to commemorate the event.
In 1952 he was in charge of the speleological expedition to the Gouffre de la Pierre-Saint-Martin cave system in the Pyrenees. The French speleologist Marcel Loubens, died in an accident with an electric hoist during the ascent after spending four days in the cave when the steel cable snapped. Cosyns as head of the expedition and due to his involvement in the design of the winch was considered responsible for the accident.
- Flight, 16 September 1932
- Chronology of Human Space Exploration Part 1: 1900 - 1950
- Time magazine Aeronautics: Up, Drift, Down Monday, Aug. 27, 1934
- The Explorers of the Sky, Investigating the Cosmic Rays
- Slovenian Ministry of Culture register of national heritage reference number 17195
- Le Progrès, 18 August 1952
- Life Magazine 1 September 1952
- Occhialini and the Università Libre de Bruxelles. An interview by L. Gariboldi in The Scientific Legacy of Beppo Occhialini, Springer Berlin Heidelberg, 2006, ISBN 978-3-540-37353-7