Illustration of August Piccard's balloon at an altitude of 15,000 metres on 27th May 1931. The balloon is carrying the Swiss-Belgian physicist Auguste Piccard (1884-1953) and his assistant Paul Kipfer. This was the first flight of the balloon and pressurised gondola designed by Piccard. It carried Piccard and Kipfer to a record altitude of 15.781 metres, making them the first people to enter the stratosphere. In order to reach the stratosphere Piccard had designed the gondola to be airtight, with pressurised air inside, and used a very large balloon, that didn't require to be fully inflated for take-off. During the flight they were able to gather substantial data on the upper atmosphere and measure cosmic rays.