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I came across the following picture on a news site, in a series of 'this day in...' type items.

A black and white photograph of balloons

The accompanying text reads (in Dutch)

22 juni 1975 - In Geldrop werd de Internationale Holland Ballonwedstrijd gehouden. Deelnemers uit zeven landen streden daar om de Trophee du ballon libre.

Which translates to

22 June 1975 - The International Holland Balloon competition was held in Geldrop. Contestants from seven countries competed for the Trophee du ballon libre.

To my surprise, the balloons are round and are closed at the bottom. What type of balloons are these? They don't seem to be hot air balloons, are they?

share|improve this question
helium or hydrogen I'd guess – ratchet freak Jul 10 '14 at 9:12
@ratchetfreak That was my thought too, but I'd like something more definitive, preferably with more of an explanation, how common is / used to be this type of balloon and so on. – SQB Jul 10 '14 at 9:43
Assuming you are Dutch, I think you will appreciate this little gem – DeltaLima Jul 10 '14 at 22:39
@DeltaLima Yes I am, and thank you. – SQB Oct 10 '14 at 5:56
up vote 22 down vote accepted

These are gas balloons. Instead of heating the air to reduce its density and providing the buoyancy, these balloons use helium or hydrogen which is lighter than air. Before lifting off, the balloons are kept on the ground by extra weight hanging on the basket. Usually these bags, clearly visible on the picture, are filled with sand.

During the flights, the gas will slowly dissipate through the fabric of the balloon reducing the buoyancy of the balloon. By throwing more weight overboard, again sand, the balloon can maintain in the air.

Gas balloons have less control in height than hot air balloons. The balloons are more expensive to operate because of the price of helium and to a lesser extent hydrogen.

Although gas ballooning is less popular then hot air ballooning, there are a number of gas balloons operating in Europe and the USA. enter image description here

Once a year the Gordon Bennett race is held in which teams compete to fly the longest distance in their gas balloon.

After some more research into the Trophee du ballon libre I found this Polygoon Journaal item of 1976 (in Dutch). It mentions that the balloon is kept afloat by 630 cubic meters hydrogen gas.

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I thought as much, but I expected to see some of the gas bottles still lying around. Was it common to use helium instead of hot air in the 70's? – SQB Jul 10 '14 at 11:59
I wish I could vote your answer up more than once. You went above and beyond. (Pun intended only if you want to). – SQB Jul 11 '14 at 6:16
For the worse control and higher operating cost gas filled balloons can lift more payload or take the same payload higher for the same size, because density of hydrogen is much lower than that of even very hot air. – Jan Hudec Jul 14 '14 at 18:25
If one travels to Paris (but I'm sure there are other locations), you may board one which is a permanent attraction (and also used for air analysis, and unfortunately for advertising too), near the Eiffel tower. It uses helium and is able to lift 2.5t at 150m, according to Wikipedia. – mins May 26 at 8:33
@SQB That's very kind of you to award me a bonus! It was really not necessary for you to do that, but I appreciate it! – DeltaLima May 31 at 12:02

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