Picture of Physic behind sky lanterns

Hello everyone,

in this instructable I will explain the principle of flight hot air balloon (known as sky lanterns). I had hot air balloons for school project, so,I thought that it might be interested to other people see how hot air balloons works and I translate it from my language.
About tutorial for making hot air balloons, there is full of it,so, just search a little bit. :)

Sorry for possible grammar mistakes in advice, english isn't my mother language.

If you have any questions, or ideas for some new projects, just ask below or send me PM.

So, here we go! :D

If you will like it, feel free to vote!

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Step 1: Historical Introduction

What are hot air balloons?

As you may already figured it out, hot air balloon in basic is just some big bag in which you put heated air,which is produced by some fire source, so it could fly.

  • Hot air balloons were used in WW2 by Japan, they were bombing America, principle was that they were catching air streams for navigation, and then when they will get to target place, they will just shut down the flame. It is surprising that sometimes they would hit something, but they stopped because they did not know whether it working or not.
  • About sky lanterns, they were usually made from rice paper and bamboo frame, whole balloon was powered by bamboo paper dipped in wax. The principle is that fire heat up the air in the balloon which creates lift, and then lift is greater than balloon weight then it starts to rise. First great hot air balloon, was made by brothers Etienne & Joseph Montolfier. The balloon was made from paper and powered with burning thatch, volume of 800 m^3. It reached high of 2000 m and landed couple kilometers away.
  • Today, hot air balloons are used in sports, sky lanterns are used for some special occasions like birthday parties, new year celebrations, etc.
LalitaW4 months ago

THX a lot

This is really educating even I dont know much physics

ivver (author)  LalitaW4 months ago

Your welcome, I'm glad that you like it. :)

tomash6611 months ago

Great work Ivver!

I'm realy glad ( and proud ) to see you here...

ivver (author)  tomash6611 months ago

Thank you! :)

marliana11 months ago

awesome with the explanation

(removed by author or community request)
ivver (author)  DELETED_mohdazhar1 year ago
thank you! :-)
ftežak1 year ago
hehe cool
(removed by author or community request)
ivver (author)  deleted_account1 year ago
Thank you for your support, I'm very glad that you liked it. You can freely PM me if you are having trouble with something, I'll see if I can help. You have some nice instructables, I'll vote for you.
eladd1 year ago
Admittedly I only skimmed over this but I didnt see anything about delta t. It certainly seems that the data would change significantly depending on the temperature of the room (outside air). ie if the room temperature is 22.2 degrees Celsius and the air in the balloon is heated to 100C the delta t is 77.8 degrees. But what if we have an outside air temp of 32.2 degrees Celsius, do we then have to heat the inside air to 110C in order to achieve the same result? In this line of thought, would it be more relevant to have recorded the delta t instead of the internal temperature of the balloon, since the internal temp seems irrelevant...
ivver (author)  eladd1 year ago

I didn't do that measurements because I could not control room temperature in that scale, but, I can give you the answer. You can calculate it with formula for lift: F_u=gV_b (ρ_z-ρ_b ) , where "g" is grav. constant, V_b is volume of balloon, p_z is density of air which is in room and p_b is density of air in balloon. About density of gases on different temperatures, you can use this calculator if you don't like paper job: (air has 29g/mol)

We have to heat up air inside of balloon more than delta t to have same results as the one with lower room temperature.

dcsabi1 year ago
You might have problems with your grammar but your physics rocks :)
ivver (author)  dcsabi1 year ago

haha :D thanks :D

MrE1 year ago

Wow! I am so impressed with this. So rarely do you find someone who claims to explain the workings and the actual physics behind something and then actually SEE them show the actual physics. This is without a doubt in my mind the best instructable, with the most detailed info, real life tests, documentation. You have repeatable and verifiable lab tests with all the work shown. I am in awe of you work and dedication you gave to this instructable. Please keep up the good work and continue giving us more like this. I am sending you a badge. The world needs more like this and more people like you.

ivver (author)  MrE1 year ago

Thanks a lot for supporting me and reading! I'm glad that you (and I think others too) liked it. I have in plan to make 2 more instructables like this one, but, I don't know how soon it will be. And again, thanks a lot. :D