Automated pressure control in pressurized balloon systems

Abstract

Efforts of the NASA Long Duration Balloon Vehicle (LDBV) Project to produce a mid-latitude capable, long duration balloon have centered on pressurized systems. Recent flights have shown that large systems, using Overpressurized Zero Pressure (OZP) balloons, have significant performance advantages over their zero pressure brethren. The absence of ducts on these systems requires venting of excess lifting gas through an apex valve. The valve is also used for venting during float to limit pressures in the polyethylene structure. Close pressure control is required on these systems because limit pressures are critical to balloon viability. To limit the amount of human commanding and attention required to operate the LDBV system, automated valving controls are required. A simple, two-state control algorithm was tested successfully during flights 342N and 365N from Lynn Lake, Manitoba. Subsequently, a fully automated ascent and float control was successfully employed on flight 393NT from Fort Sumner, New Mexico. This paper presents the analysis and flight performance of these control algorithms and their software implementation.