Static Lift

Author: CislunarSpace
Site: https://cislunarspace.cn

Definition

Static lift is the buoyant force generated by lighter-than-air (LTA) aircraft using gases with density lower than air (helium or hot air). According to Archimedes' principle, an object submerged in fluid receives a buoyant force equal to the weight of the displaced fluid. For stratospheric airships, static lift is the core physical mechanism for maintaining altitude.

Physical Principle

Archimedes' Principle

B = \rho_{air} V_{displaced} g

Net Static Lift

B = \rho_{air} V_{He} g - \rho_{He} V_{He} g = (\rho_{air} - \rho_{He}) V_{He} g

Altitude Effects

Altitude	$\rho_{air}$	$\rho_{He}$	Static Lift
0 km	1.225 kg/m³	0.169 kg/m³	100%
10 km	0.414 kg/m³	0.057 kg/m³	34%
20 km	0.089 kg/m³	0.012 kg/m³	7.3%

Design Calculations

Required Helium Volume

For given payload mass $m_{payload}$ and flight altitude $h$ :

V_{He} = \frac{m_{total}}{\rho_{air}(h) - \rho_{He}(h)}

References

Du Y, Liu W. Aerostat Principles[M]. Aviation Industry Press, 2024.
Cook M V. Airship Technology[M]. Cambridge University Press, 2023.