Buoyancy & Atmospheric Considerations

Buoyancy provides the lift that makes a helium filled balloon float.  In order for you to be a capable BalloonCraft Pilot, it will be important for you to understand how buoyancy works and is affected by atmospheric conditions.

Buoyant lift is produced from the difference between the weight of the helium gas contained in the balloon, and the heavier air the balloon displaces.  Neutral Buoyancy occurs when the lift balances the weight of the balloon and the BalloonCraft.  A neutrally buoyant balloon, in still air, will not ascend (rise) or descend (fall).  The BalloonCraft 2000 is designed to operate at a slightly less than neutral buoyant point so that it will descend slowly without any motor action. Ballast weights are added in small increments to achieve this buoyancy point.  The challenge is to maintain this buoyancy point as atmospheric conditions change.  Temperature and atmospheric pressure affect the weight or density of the air the helium balloon displaces, hence it affects the buoyancy.

The following will help you to understand how your BalloonCraft 2000 will be affected by subtle changes in temperature and atmospheric pressure.

Buoyant lift decreases with a rise in temperature.  If you set the Buoyant point on a cold day, just before the heat comes on, you may notice a reduction in lift, and the lift thruster will have to work harder.  The same may occur if you move from a cold room to a slightly warmer room.  The converse is also true.  If you set the buoyant point in a warm room, and then move to a cool room, you may find that the BalloonCraft rises to the ceiling!

Buoyant lift also decreases with a drop in atmospheric pressure.  A drop in barometric pressure usually means bad weather, so don't be surprised if you notice some reduction in lift if the weather takes a turn for the worse.

In general, you will maintain the best flight performance if you become accustomed to checking the buoyancy point by adding or removing ballast.