Large-scale cargo airships remain commercially impractical primarily due to the uncontrolled buoyancy variation during loading and unloading operations — a phenomenon known as "buoyancy snap" or "whiplash". This paper presents a theoretical viability analysis of a novel buoyancy control architecture based on a closed thermal cycle using a helium-water vapor mixture, combined with a passive hydraulic tension-regulation mechanism based on Pascal's principle. The system allows precise, reversible control of lift force without expelling gases or requiring external infrastructure, operating in a fully closed fluid cycle. A quantitative model is developed using the ideal gas law, Dalton's Law, Pascal's principle, and the International Standard Atmosphere to estimate net payload capacity as a function of envelope volume and system component masses. Version 2.0 update. Major revisions relative to the original preprint: - Optimized chamber volume fraction f = 0.80 (vs f = 0.71) enabled by an external rigid gondola configuration replacing the internal 500 m³ module, increasing net lifting capacity. - Partial-cycle thermal strategy: boiler and condensation system sized per net payload discharged rather than total chamber vapor mass, reducing boiler power by a factor of 5.8x. - New condensation architecture: a calcium chloride hexahydrate (CaCl2·6H2O) phase-change material thermal battery, with two operating modes — fully autonomous (Option A) and ground water connection (Option B). - Complete bottom-up mass balance with 37 individually sourced components, replacing the top-down estimates of the original version. - Component-level mass balance recalculated explicitly at L = 127 m (~100,000 m³ scale). -Updated net payload results: ~3.7 t (Option A) / ~7.1 t (Option B) at L = 92 m; ~19.6 t (Option A) / ~37.2 t (Option B) at L = 127 m. This version supersedes v1.0. All previous limitations regarding model uncertainty (±25-40%) remain in effect; this is a theoretical viability analysis requiring experimental validation.
Franco Carricart (Sat,) studied this question.