The "Gravity Balloon" (a nickname derived from its buoyancy-based altitude control) was not a balloon in the party sense, but a operating in the stratosphere—a realm colder, drier, and more violent than most aircraft ever encounter. 2. The Physics of Floating Against Gravity To understand Loon, one must first understand the stratosphere (10 km to 50 km altitude). Below 10 km, weather dominates: wind shear, turbulence, precipitation. Above 20 km, the atmosphere is stable, with predictable zonal (east-west) wind bands. However, at 20 km, air density is only 7% of sea level.
The optimization problem: maximize the number of user-hours connected given constraints on battery (solar recharge rate), wind prediction error, and balloon longevity. This became a partially observable Markov decision process (POMDP) with >10^6 state variables. google gravity balloon
Loon required —a fully sealed, rigid envelope that maintains internal pressure higher than the external atmosphere at all times. The challenge: as the sun heats the balloon, internal pressure rises, stressing the polyethylene film. The "Gravity Balloon" (a nickname derived from its