What causes false lift which sometimes occurs during launch procedures?

What causes false lift which sometimes occurs during launch procedures?

• A. Venturi effect of the wind on the envelope
• B. Increased interior temperature
• C. Higher outside humidity
• D. Propane pressure fluctuations

Answer: (A)

Venturi effect from the wind around the envelope creates a temporary pressure difference that can lift the envelope even before heating is enough to provide real buoyancy. As air speeds up along the base and sides of the balloon, pressure underneath and around the skirt drops, producing an upward force. This dynamic lift looks like true lift during launch but isn’t from heated air. Other factors like interior temperature, humidity, or propane pressure affect actual lift, not this wind-induced pressure change, so they don’t cause the same false lift seen in gusty conditions.

Venturi effect from the wind around the envelope creates a temporary pressure difference that can lift the envelope even before heating is enough to provide real buoyancy. As air speeds up along the base and sides of the balloon, pressure underneath and around the skirt drops, producing an upward force. This dynamic lift looks like true lift during launch but isn’t from heated air. Other factors like interior temperature, humidity, or propane pressure affect actual lift, not this wind-induced pressure change, so they don’t cause the same false lift seen in gusty conditions.