Abstract
Vertical flight performance of Lighter-than-Air free hot-air balloons is derived and discussed. Novel mathematical model using lumped-parameters has been used to model balloon flight dynamics and steady-state performance in particular. Thermal model was not treated as the super-heat is under the control of aeronauts/pilots. Buoyancy or gross lift, net or effective lift, specific lift, and excess specific lift were derived for a general single envelope balloon and can be applied to hot-air, gas and hybrid balloons. Rate-of-climb, absolute ceiling, rate-of-descent, and the maximum rate-of-descent or the uncontrolled terminal descent have all been modeled and sample computations performed for AX8 or AX9 FAI-class hot-air balloons. Lifting index or the specific net/effective lift have been computed treating ambient and hot air as ideal gases at various pressure altitudes and representative envelope temperatures. Drag coefficient in upward and downward vertical flights have been chosen based on best available data. Experimental scale and full-scale flight tests are suggested for more accurate estimates of external aerodynamics in vertical balloon flights. CFD computations of coupled inner- and external-flows are also recommended in future efforts. Knowledge of free balloon’s vertical performance is essential in flight planning and operational safety of flight.
Highlights
The main motivation for this study was to present new and comprehensive approach to performance calculations of free balloons and manned hot-air balloons in particular
Even the specialized literature and references we found are somewhat frugal on the aerodynamic drag information
The main contribution of this article is in the development and utilization of a comprehensive mathematical model of LBH quasi-state vertical flight performance using some novel definitions and introducing new parameters
Summary
The main motivation for this study was to present new and comprehensive approach to performance calculations of free balloons and manned hot-air balloons in particular. Buoyancy-driven or lighter-than-air (LTA) aircraft find many applications and their utilization may increase in the future. The Federal Aviation Administration (FAA) (2008) uses designations LBH (hot-air balloon) and LBG (gas balloon), it is appropriate to call such balloons Montgolfière (LBH) and Charlière (LBG), honoring their respective inventors. While lacking importance in commercial air transportation since the time of rigid airships, LTA aircraft have several specialized and unique applications. Much of current weather data comes from the routine atmospheric sounding using stratospheric LBGs. Manned and unmanned aerostats are used as tethered airborne observational platforms, for atmospheric and astronomical research, or for carrying airborne radars, telecommunication equipment, and other instrumentation. Hot-air ballooning (LBH), a recreational activity, has small commercial component, such as sightseeing and adventure flights
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