Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: annie123 on 03/09/2012 14:11:58

Title: does the shape of a hot air balloon make a difference to speed?
Post by: annie123 on 03/09/2012 14:11:58

My son insists that the shape of a balloon has none or very little effect on its performance in wind currents. I would have thought that odd shapes with protuberances as in many of the balloons at the hot air festival here right now would affect their speed because of varied resistance. Any hot air balloon experts out there?

Title: Re: does the shape of a hot air balloon make a difference to speed?
Post by: CliffordK on 03/09/2012 17:13:48

The hot air balloons more or less travel with the wind.  So, an odd shape should not slow it down, and anything that would increase the wind resistance might actually be beneficial.

Weight, of course would also be an issue.  a tear-dropped bag would likely minimize the weight of the material vs the amount of contained air.  As well as maximizing the heat distribution within the balloon and minimizing surface area cooling.  This likely would not make a huge difference, but might mean additional fuel would be required on some of the odd shaped balloons.

The weight in turn might affect the performance in the air, but it is likely minimal.

Title: Re: does the shape of a hot air balloon make a difference to speed?
Post by: yor_on on 04/09/2012 04:15:37

A balloon made as a sail Clifford? Would that speed it up? And could one make a shape that allowed it to move closer to the wind?
=

No it wouldn't matter, would it :)
It would be mass relative its area meeting the wind wouldn't it?
Thought of a sailing boat there, but that's a different beast.

Title: Re: does the shape of a hot air balloon make a difference to speed?
Post by: CliffordK on 04/09/2012 05:09:12

St. Louis has an annual balloon race.

And, some sponsors have unique shaped balloons.  Hopefully I won't get banned for allowing the post of adversing logos...  Should I invert them like BBC?

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.energizer.com%2FSiteCollectionImages%2Fbunny_center%2Fhot_hare_balloon%2Fright_rail_splash.jpg&hash=9a856ffe4b1d37fd627b2492ffddea35) [ Invalid Attachment ]  [ Invalid Attachment ]

And Yes, yor_on, somebody apparently designed a sailing ship balloon.
 [ Invalid Attachment ]

While the mass would be greater for the odd shaped balloons, the surface area may be proportionally greater, so the two may compensate for each other.

Title: Re: does the shape of a hot air balloon make a difference to speed?
Post by: yor_on on 04/09/2012 23:01:56

That one was really cool Clifford :)