Aeronautics and astronautics – Aircraft – lighter-than-air – Balloons
Patent
1998-10-23
1999-11-30
Carone, Michael J.
Aeronautics and astronautics
Aircraft, lighter-than-air
Balloons
244128, B64B 140, B64B 158
Patent
active
059927950
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a stratospheric balloon with long flight duration of the type having an envelope made of transparent material able to present a state of fullness where said envelope is entirely inflated. "Transparent material" is normally understood to mean a material which allows solar and infrared radiation to pass with very minor absorption in relation to the incident flux. This material may in particular consist of polyethylene or polyester which are the materials generally used to manufacture stratospheric balloons.
It is known that variable volume conventional stratospheric balloons may have very large volumes (greater than 10.sup.6 m.sup.3) and can transport heavy loads to altitudes of the order of 40 to 45 km. These stratospheric balloons are characterized in particular in that they operate with a gas which is lighter than air from which they draw their lifting force and in that their volume in the full state is very much greater than their volume in the bubble state. This type of balloon may for example be illustrated by patent U.S. Pat. No. 3,312,427. These stratospheric balloons are totally different from hot air balloons which are constant volume balloons, using atmospheric gas in which they are immersed and drawing their lifting force, either from a burner, or from the ambient radiation (solar or infrared). Solar or infrared hot air balloons are made so as to collect continuously the maximum solar or infrared energy, and to this end, are provided over at least a half of their surface area with a device for trapping solar or infrared radiation. Hot air balloons may for example be illustrated by the patents FR 2.418.150 or U.S. Pat. No. 4,262,864.
The essential problem which variable volume stratospheric balloons present lies in their very short life span, of the order of 24 hours, which may be extended to several days on condition that large quantities of ballast are carried. In point of fact, during the daytime, when a stratospheric balloon arrives at the full state, part of the gas is expelled until the free lifting force is cancelled, the balloon then becoming stabilized at its flight platform. At night, the gases of the balloon undergo a high degree of cooling which brings about a considerable reduction in the volume thereof and causes the balloon to descend irreversibly. Only jettisoning ballast will then enable this to be stabilized (of the order of 10% of the total weight). However, the lifting force which is thus added is retrieved on the following day and results in a new expulsion of gas at the ceiling so that the operation of jettisoning ballast is renewed each night in order to prevent an irreversible descent. Since the quantities of ballast carried are limited, the lifespan of such balloons cannot generally exceed 4 to 5 days. This limitation to the lifespan is a serious fault in this type of balloon while the necessity of carrying ballast in a large quantity is very penalizing since it necessitates an increase in the volume of the balloon and the mass of aerostatic gas for a given pay load and, consequently, leads to an increase in the cost of the flight.
In order to overcome this disadvantage, a variable volume stratospheric balloon has been designed, such as described in patent FR 2.639.607, having a thermal trapping cover fixed to the upper part of the envelope. As explained in this patent, such a trapping cover, in point of fact, enables the balloon to be stabilized between upper levels (daytime periods) and lower levels (night-time periods) over a plurality of day and night cycles. However, as with all conventional stratospheric balloons, such a balloon is confronted with problems of diffusion of the aerostatic gas, which leads to a limitation of its flight duration.
The present invention aims to overcome the above mentioned disadvantages of current stratospheric balloons and essentially aims at providing a stratospheric balloon having a long flight duration without requiring the jettisoning of ballast.
Another objective of the invention is to provide a stratospheric b
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Carone Michael J.
Centre National d'Etudes Spatiales
Ducker, Jr. Charles R.
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