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A hot air balloon needs to be slightly negatively bouyant. If a particular design can lift 1000lbs, an ideal flight weight might be 900 lbs so that, in the event of a burner failure, the balloon will slowly descend.
If the payload for a given flight is only 600lbs (fuel, pilot, passengers) then 300 lbs of ballast (sandbags) will be needed to keep the bouyancy in the correct range.
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Sandbags or other ballast is used mostly for helium balloons, not hot air balloons. The rate of descent of a hot air balloon is controlled by the time the burners are burning. If it is going down too fast, you burn longer. You may have two burners but if you lose one, the other one can keep the balloon aloft. they are always much larger than needed.
The design weight is based upon the volume of the balloon and a particular temperture of the air in the balloon which must be below the melting point of the fabric.
Typically you don't need ballast to adjust payload in a hot air balloon. IN a helium balloon, the only way you can go back up after starting a descent (by dumping helium) is the drop some weight. So ballast would be helpful with helium balloons.
What else can I help you with?
Why do hot air balloons have sand bags?
Modern hot air balloons do not have sand bags because the air input is easily controlled for lift. Hot air balloons used to have sandbags to weigh them down until lift off and sand was gradually dumped to gain height in the air.
What types of hot air balloons are there?
There are traditional hot air balloons, special-shaped hot air balloons (such as animals, objects, or characters), and solar-powered hot air balloons that use solar energy to heat the air inside.
Where in the atmosphere do hot air balloons float?
Hot air balloons float because hot air displaces cool air in the atmosphere
Why lighter than air balloons fly?
air balloons or hot air balloons fly because they fill with a very light type of air. The air is hot air.
What does thrust have to do with hot air balloons?
This may not help, but I didn't think it had ANYTHING to do with hot-air balloons...
Why were hot air balloons made in 1783?
People think that hot air balloons where made for battles.
when do hot air balloons come to bucyrus ohio?
when do hot air balloons cometo bucyrus ohio
How do hot air balloons stay in air?
hot air rises
How do hot air balloons produce lift?
Hot Air
Why do you think hot-air balloons can rise into the air?
Hot-air balloons can rise up into the air because hot air is lighter, allowing it to float up into the sky.
What are hot air balloons used for now a days?
Hot air balloons are now mostly used for leisure
Does a hot air balloon have helium inside it?
Hot air balloons do not use helium; they are typically filled with hot air. Helium is non-flammable and more commonly used in other types of balloons like weather balloons or party balloons. The hot air inside a hot air balloon is what allows it to rise and float.
