Wetenschap - 26 mei 2016

High level science

tekst:
Roelof Kleis

Does a hot air balloon travel as fast as the wind? Meteorologist and mountain climber Bert Heusinkveld tested it. Don’t try this at home!

Photo: Cisco de Bruijn

The photo alone may arouse butterflies in some peoples stomachs. Not feeling it? Watch the movie on this page. Heusinkveld undertakes a horrifying spacewalk to be able to point the anemometer in the right direction. A few hundred meters  under him the world around the measuring station Cabauw by Utrecht moves past.

This comparison with space travel is from Heusinkveld himself. ‘I kind of felt like an astronaut. It was unreal to be hanging under such a balloon. When the burner is turned on such a balloon makes a whole lot of noise, but under the basket it was quiet. A really strange experience. As climber I am used to quite a lot. But usually when I abseil I see a cliff below me. Now I saw ships, meadows and trees. And above me a thin rope and a basket.’

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And that all in the name of science, because this daring act served a purpose. The measurements are part of the PhD research of Cisco de Bruijn from the KNMI. Dr Bruijn’s professor is Bert Holtslag from the chair group Meteorology and Air Quality Group. De Bruijn wants to know if a hot air balloon can be used as anemometer. Hot air balloons float with the wind. But does it travel as fast as the wind?

To find out they needed accurate measuring equipment. And Heusinkveld just happened to have bought such a device. ‘An anemometer which measures 50 times a second. I bought it for research for the PhD candidate Martin Sikma. He used it for research on rice fields in Japan.’ The fact that Heusinkveld is an experienced mountain climber came in handy. The anemometer was mounted in the air.

I kind of felt like an astronaut. It was unreal to be hanging under such a balloon.
Bert Heusinkveld

The measurements need to show if and how a hot air balloon can be used as an anemometer. Heusinkveld: ‘The KNMI has developed an app specially for hot air balloons. The app accurately shows where the hot air balloon is. So we know the position, height and speed of each balloon’.  By comparing this data to the wind measurements, it can be derived how the balloon reacts to the wind. A kind of crowd-sourcing for balloonists.

It was the first time in a balloon for Heusinkveld. The film was made by his camera, mounted on a selfie-stick. ‘Actually it is a golf ball retriever. One of those things which golfers use to retrieve balls from the water. These are longer than a selfie-stick, and thus I have a wider angle. I flattened the end of the stick and fastened my camera on it.’ If you look carefully you can see the stick.

To be really honest this movie is fake. With which I mean: Heusinkveld acts as if he has to adjust something on the equipment. ‘We were so busy that the first time I climbed overboard, we didn’t film it. The second time something went wrong with the camera. This movie is of the third time I climbed overboard.’ The wow-effect is no less. The water in the back is the Rijn. The flight was from Bergambacht to just beyond Nieuwegein.

Reacties 1

  • Dorothé Lucassen

    Bert verandert niets ��
    Groetjes Dorothé


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