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Adam Hart-Davis
Flies fly; birds fly; jumbo jets fly; even this thing flies, after a fashion anyway.  The question is; what’s the biggest thing that could possibly fly?  The choice seemed to be heavier than air, a plane, or lighter than air.  Well, the biggest things to have flown so far are airships and balloons, so I’ve asked Glenn and the team to try and make a man carrying hot air balloon entirely from paper.  So, Glenn, this is actually it is it?

Glenn
It is.

Adam Hart-Davis
This is my beautiful balloon.

Glenn
Your beautiful balloon, absolutely.

Adam Hart-Davis
Not quite that lovely colour unfortunately.  I’d love a pink one!

Glenn
Would you?

Adam Hart-Davis
Our balloon is going to be huge.  We know that a conventional hot air balloon has to hold about 600 cubic metres of air to lift 200 kilograms, a bit more than me, which means a balloon 32 metres in circumference.  Why do you want it this shape and not just a sphere?

Glenn
It’s optimised for making, putting as little stress on this fabric as we possibly can so it’s optimised...

Adam Hart-Davis
Having got a shape that looks like a balloon Glenn uses another piece of software to unwrap it, rather like opening a birthday present.  We have to make a giant version of this shape and then wrap it up again to make the full size balloon.

The basic problem about making a hot air balloon out of paper is that paper is flat and the balloon is spherical, i.e. three-dimensional.  Now, the way they’re doing it is to make a whole lot of shapes like this, long, thin, lozenge shapes.  Now nine of these have already been stuck together and here they are, this is the bottom all glued together and there’s the top and you’ll see that the final thing, there’s the inside with all those markings, the final thing will actually be roughly that shape because we haven’t made a third of it yet even and then it’ll be very much balloon shaped.  Isn’t that a lovely thing?  And the gluing, the taping down the edges is absolutely critical because not only do they have to fit together but there must not be any holes for the hot air to escape.

Right, so at last we’re inflating it.  Just filling it with cold air to get the shape up so we can then start pushing in the warm air, and basically it’s just a simple extractor fan pushing air into it and gradually you can see it taking shape.

I must admit the balloon looks stunning.  Now fully inflated with cold air it looks exactly like the computer picture we started from two days ago.  Glenn and the team have done an outstanding job.  It clearly is a balloon and I can’t wait to get on board.  We want to get the envelope as upright as possible before putting the flame in so that there’s no paper immediately above the burner.

Glenn
I think that’s fine for the time being, thanks.

Adam Hart-Davis
But we seem to be losing control of the envelope.  Either it’s slowly deflating because the fan is now switched off or the tapes are pulling it round. 

It’s difficult to be sure but it looks as if the crown piece came away from the paper setting up a tear that ran down the side of one of the seams.  Perhaps if we got the heat into the balloon sooner and got it upright it would have been less stressed.  Maybe we could have used slightly heavier paper but we don’t know.  Not everything is predictable.

It was so close.  I didn’t really believe this would work.  This is the most ambitious project the Science Shack team has taken on and I didn’t really believe it would work.  I thought they’d bitten off more than they could chew, and then I began to believe it about an hour ago.  It looked so fantastic inflating here on the ground and I was getting quite excited and it’s really sad.  I guess, I guess there was just too much tension.  The paper is very flimsy and it’s gone along a seam, probably the sticky paper has a slightly different elasticity or folding or something and there was just too much tension there and then once it had gone the whole thing ripped very fast. 

And I don’t expect we’ll have the chance to do it again.

4’41”