Author: CislunarSpace
Site: https://cislunarspace.cn
Buoyancy-weight imbalance refers to the phenomenon where a stratospheric airship's buoyancy no longer equals its gravity. When buoyancy exceeds gravity, the airship ascends; conversely, it descends. Buoyancy-weight imbalance is a unique core challenge for stratospheric airships, directly affecting altitude maintenance and station-keeping capability.
F n e t = B − m g = ( ρ a i r − ρ H e ) V H e g − m t o t a l g F_{net} = B - mg = (\rho_{air} - \rho_{He}) V_{He} g - m_{total} g F n e t = B − m g = ( ρ ai r − ρ H e ) V H e g − m t o t a l g
η = B m g = ( ρ a i r − ρ H e ) V H e m t o t a l \eta = \frac{B}{mg} = \frac{(\rho_{air} - \rho_{He}) V_{He}}{m_{total}} η = m g B = m t o t a l ( ρ ai r − ρ H e ) V H e
η \eta η State η > 1 \eta > 1 η > 1 Ascent η = 1 \eta = 1 η = 1 Trim balance η < 1 \eta < 1 η < 1 Descent
Cause Effect Variation Helium leakage Buoyancy decrease -0.5%/month Diurnal temperature variation Buoyancy fluctuation ±10%/day Pressure altitude change Buoyancy change Decreases with altitude
Method Principle Overpressure design Internal pressure reduces temperature sensitivity Ballonet Absorbs volume changes to maintain constant pressure
Method Principle Energy Helium inflation/deflation Active helium volume regulation Medium Ballast adjustment Payload/ballast jettisoning Low Altitude maneuvering Use altitude to regulate buoyancy Higher Thermal regulation Adjust skin/helium temperature High
Chen W, Wang H. Buoyancy Management for Long-endurance Stratospheric Airships[J]. AIAA Journal of Aerospace Systems, 2025. Jones M, et al. Helium Loss and Thermal Effects on Airship Performance[R]. DARPA Technical Report, 2024. 