A proposed improved balloon system for carrying scientific instruments in the stratosphere would include a lightweight, ambient-pressure helium balloon and a vented infrared Montgolfiere (see figure). [An infrared Montgolfiere is an ambient-pressure warm-air balloon, named after the familiar fire-heated hot-air balloons invented by the Montgolfier brothers. An infrared Montgolfiere is heated primarily by the Sun during the day, and/or by infrared radiation from relatively warm surface of the Earth at night.] The system would feature controllability of altitude for taking scientific data, landing, or taking advantage of favorable winds for relocation. The system would be designed for long life, but would weigh less (and therefore cost less) than do previously developed long-life balloon systems.

Two Different Balloons would be used together to take advantage of the differences between their diurnal variations in buoyancy.
The advantages of the proposed system are best understood in the context of two prior classes of long-life, high-altitude balloons. One prior class is that of helium superpressure balloons, in which pressures above ambient are maintained in order to maintain constant densities and thus constant altitudes. The other prior class is that of infrared Montgolfieres (used by themselves, rather than in combination with ambient-pressure helium balloons according to the present proposal). Superpressure balloons must be strong, and thus heavy, to maintain their interior pressures above ambient. Montgolfieres are not as efficient as helium balloons are and hence must be very large, and correspondingly heavy. A Montgolfiere by itself floats higher during the day than during the night, and thus is not well suited for observations for which altitude control is required. Altitude control for helium balloons has been effected by partial venting of helium (for descent) or dropping of ballast (for ascent), but these releases entail a tradeoff between controllability and longevity.

In the proposed system, there would be no deliberate venting of helium or release of ballast. The ambient-pressure helium balloon would provide most of the lift during the day. The infrared Montgolfiere could be used to make up for the small decrease in buoyancy caused by nighttime cooling of the helium balloon, or to increase altitude. A vent in the top of the infrared Montgolfiere could be used to vary the buoyancy.

Masses and sizes of a conventional superpressure helium balloon and of the balloons in the proposed system have been calculated for a payload mass of 500 kg at the altitude where the ambient pressure is 0.01 bar (1 kPa). The total mass of the proposed system was found to lie between one-fifth and one-third of that of the superpressure helium balloon, the exact value depending on specific design parameters. Because the construction of an ambient-pressure balloon is much easier than is that of a superpressure balloon, the cost of the proposed system should be even lower than that indicated by the ratio of masses.

This work was done by Jack Jones of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Physical Sciences category.

NPO-20742

Topics:
Aircraft Balloons Hazardous materials Hazards and emergency operations Physical Sciences Pressure Radiation Sun and solar Vehicles
This Brief includes a Technical Support Package (TSP).
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Long-Life Stratospheric Balloon System with Altitude Control

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NASA Tech Briefs Magazine

This article first appeared in the January, 2002 issue of NASA Tech Briefs Magazine (Vol. 26 No. 1).

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Overview

The document outlines a proposal for a novel long-life stratospheric balloon system designed to carry scientific instruments at high altitudes. This system combines a lightweight, zero-pressure helium balloon with a vented infrared Montgolfiere, a type of hot air balloon that utilizes solar heating during the day and radiant heat from the Earth at night. The primary goal of this innovative design is to achieve altitude control, allowing for the collection of scientific data, safe landings, and the ability to take advantage of favorable winds for relocation.

The document contrasts this new system with two prior classes of high-altitude balloons: helium superpressure balloons and infrared Montgolfieres used independently. Helium superpressure balloons maintain internal pressure above ambient levels, which requires them to be strong and heavy, making them costly and less efficient. On the other hand, infrared Montgolfieres, while lighter, are less efficient than helium balloons and must be larger to achieve the necessary lift. They also experience altitude variations between day and night, which complicates their use for consistent scientific observations.

The proposed system addresses these limitations by using the lightweight zero-pressure helium balloon to provide most of the lift during the day. At night, the infrared Montgolfiere compensates for any loss of buoyancy due to cooling and can also be used to increase altitude if needed. This dual approach allows for better altitude control without the drawbacks associated with traditional helium balloon systems, which often rely on venting helium or dropping ballast for altitude adjustments.

The document emphasizes the significant advantages of this combined balloon system, including reduced weight and cost compared to superpressure balloons, easier construction, and enhanced operational flexibility. The system is designed for long life and aims to facilitate scientific missions that require precise altitude control, making it particularly suitable for applications such as buoyant astronomical observatories.

In summary, this innovative balloon system represents a significant advancement in stratospheric research technology, promising improved efficiency, cost-effectiveness, and operational capabilities for scientific exploration at high altitudes.