Here is an English translation of European Patent laying-open publication 524,872, "Montgolfier", to Domen..... translated (roughly) by myself...



(Translator's note: Throughout this patent, the word "montgolfiere" is used to mean a hot-air balloon. I think this is a good usage which ought likewise to be encouraged in English (parallel to the use of the word "roziere" to denote, well, a roziere type balloon), and therefore I have similarly used "montgolfier" for this concept throughout.)

TRANSLATION OF EP PATENT PUBLICATION 524,872

EUROPEAN PATENT OFFICE

Publication Number: 0,524,872 A1

APPLICATION FOR EUROPEAN PATENT

Application Number: 92402099.3

Application Date: 21 July 1992

International Class: B 64 B 1/58.

Priority: 24 July 1991 FR 9109383

Application Publication Date: 27 January 1993 Bulletin 93/04

Designated Contracting States: AT DE FR GB IT

Applicant: Domen, Jean-Paul

13 Rue Ganneron

F-75018 Paris (FR)

Inventor: Domen, Jean-Paul

13 Rue Ganneron

F-75018 Paris (FR)

Montgolfier

Abstract: This montgolfier comprises two means of heating: exothermic condensation of water vapor, and greenhouse effect. It comprises a balloon (10) provided on its upper part (12) with a layer which is both transparent and absorbent, and in its interior with a screen (44) which absorbs solar radiation. The screen (44) may be arranged in the best manner to be able to capture this radiation. Moreover, the air with which the balloon (10) is inflated is sufficiently hot and humid for exothermic condensation of the water vapor which it contains to be sufficient, at least from a certain altitude, to augment the Archimedean force and to accelerate the speed of rising of the balloon.

Applications: New toy (diameter=2m)

Leisure montgolfier (diameter=20m)

Montgolfier winch (diameter=100m)

MONTGOLFIER

The present invention relates to montgolfiers, that is to say, to balloons which are open at the bottom and are inflated with hot air.

A montgolfier remains aloft due to the force of Archimedes, its total weight being less than the weight of the external air which it displaces. The lift is equal to the product of the volume of the balloon, the acceleration of gravity, and the difference of the volume-masses inside and outside the balloon due to the difference between the temperatures of the air inside and outside the balloon. At the level of the opening, the air inside the balloon is in pressure equilibrium with the external air, so long as the speed of ascent is zero. At the top of the balloon, the interior air is hotter than at the base, and it is under a pressure which is greater than that of the exterior air. In order to maintain the over-pressure which inflates the balloon and the force of Archimedes which makes it rise, it is necessary to provide heat constantly or intermittently, in order to compensate for cooling due to the adiabatic expansion of the air in the balloon during its ascent, and for the losses by thermal conduction through its skin. In order to implement this provision of heat, it is usual to burn propane gas into the balloon in a discontinuous fashion. By way of example, to keep a montgolfier of twenty meters in diameter weighing two hundred and fifty kilograms in the air for one hour, it is necessary to burn forty kilograms of propane, i.e. to provide an average of a hundred and sixty kilowatts to the balloon. [sic]

A manner of ameliorating this necessity has briefly been described in an article in the French newspaper "Le Figaro" dated 19 November 1991, concerning the European campaign of Arctic ozone study. Montgolfiers which present a transparent lower portion and an aluminized upper portion, initially inflated with helium, oscillate at high altitude between two extreme levels. This is thanks to solar radiation during the day and infrared radiation from the earth during the night; the air-helium mixture, with which these balloons are inflated after the first descent, always remains sufficiently hot to allow them to behave like ludions [TN: a "ludion" is a toy that bobs up and down in a bottle] for a relatively long time period.

A first objective of the present invention is a new process for inflating a montgolfier, in order to allow it to rise to a high altitude, without any fresh supply of external heat being necessary.

A second objective of the invention is a perfected montgolfier, partly inflated according to the above procedure, which can rise very rapidly to a first altitude without supply of external energy, and then can automatically modify its behavior and can continue to rise less rapidly than before to a second altitude, still without requiring any supply of external energy.

A third objective of the invention is a perfected montgolfier, which is able to continue to rise to a third very high altitude, when the effects of the means of inflation, put into practice by the above procedure, have been exhausted.

According to the invention, a new procedure for inflating a montgolfier is characterized by consisting of utilizing this effect of hot air sufficiently humid for condensation of the water vapor contained in this air to be able to be produced, during the rising of this montgolfier, at least from a given altitude.

A montgolfier inflated in this way rises rapidly in altitude, under the effect of the force of Archimedes which increases with the speed of rising of the balloon. This is because the rising of the balloon provokes a reduction of pressure at the level of the opening, which causes expansion of the air/vapor mixture, the exothermic condensation of a part of this vapor, and finally a growing difference of temperature between the interior and the exterior of the balloon and therefore, at least for a first time, an increase of the force of Archimedes and of the speed of ascent. It would all stop immediately if the speed of ascent of the balloon were cancelled. This cumulative phenomenon is related to the conditions of meteorological instability which provoke storms and cyclones. Considerable forces are thus put into play, which can attain 50 MW for a montgolfier of a hundred meters in diameter.

The standard atmosphere is defined between sea level and the tropopause (a thermal plateau at 216.5 K starting at an altitude of 11,000 meters), by a ground temperature Te of 288 Kelvins, a ground pressure P of 101,325 Pascals, and a vertical temperature gradient dTe/dz of -6.5 K/km. Moreover, the relative variation of pressure as a function of altitude dP/P.dz=-0.12/km (which is -12,200 Pa/km at sea level and -2,500 Pa/km at the tropopause), which causes a reduction of the temperature at the dew point dTs/dz as a function of the altitude of about -2 K/km. As far as the variation of the saturation pressure of water is concerned, it follows a law independent of the ambient pressure, and it varies from 100 to 300 Pa/K as the interior temperature Ti varying from 288 K to 310 K. Moreover, from the equations of a perfect gas and the variation of pressure with altitude, it can be shown that the adiabatic expansion of the air inside a montgolfier causes a reduction of the temperature Ti of this air of 9.77(Ti/Te) K/km.

By combining the characteristic equations of a montgolfier (the equations of equilibrium in the air and the equations of state of the interior air and the exterior air) it can be shown that the variation dTi of the interior temperature Ti which is necessary to keep a given constant load in the air at a given altitude, in the standard atmosphere described above, as a function of the variation of altitude dz (in kilometers) is an increasing function dTi/dz =27.7(Ti/Te)2-34.2(Ti/Te), as shown in FIG. 1. From the equation of equilibrium shown above, it is possible to calculate the differences of the temperatures (Ti-Te) and of the volumetric masses (e-i) at sea level and at that of the tropopause, which correspond to the maximum values of the ratios (Ti/Te) to implement at ground level and at altitude, in order to be able to take off and thereafter to keep aloft. These differences are shown by the two doubly graduated lines A and B, respectively placed below and above the curve in FIG. 1. These superimposed curves permit explanation of all the thermodynamic phenomena which take place during the ascent of a montgolfier inflated according to the procedure of this invention.

First, one sees that in the standard atmosphere a montgolfier can ascend while its internal temperature diminishes with the altitude. This is true as long at it is below the tropopause, and under the sole condition that the ratio Ti/Te between the absolute temperatures inside and outside the montgolfier remains less than 1.234 in the standard atmosphere. The maximum value of the cooling is 6.5 K/km (the gradient dTe/dz) for Ti=Te, and it corresponds to a fictitious montgolfier of which the total mass is zero.

As a consequence, if it is desired for a montgolfier to be able to be heated by exothermic condensation of the water initially contained in the form of vapor in the hot air which it encloses, and for this to continue as far as the tropopause, it is necessary that at the altitude of the latter, the minimum difference in temperature, necessary to remain in the air, should not exceed 51 K (i.e., 0.234 times 216.5 K). This corresponds, on the line B in the figure, to a maximum difference of volumetric mass of 70 gr/m3. Taking this term to the line A in the figure, it can be seen that this final maximum difference of volumetric mass corresponds to a maximum initial value of 1.07 for the ratio Ti/Te necessary for takeoff, if one requires to attain the tropopause without any external supply of heat.

Moreover, it has been seen above that the vertical gradient of the temperature of the dew point is -2 K/km. If this value is transferred to FIG. 1, it forms a boundary which separates the domain of conventional montgolfiers from that of the montgolfiers according to this invention. This threshold value corresponds to a ratio Ti/Te=1.17. Conventional montgolfiers, usually loaded to 250 gr/m3 and heated by propane, function with a temperature difference (Ti-Te) greater than 72 K at sea level. Accordingly, an increasing ratio Ti/Te (starting at 1.26) must be ensured in order to ensure continuous rising of the balloon. Allowing for the weight of the cylinders of propane which must be carried, this obligation limits the normal maximum altitude of montgolfiers of the current type rather rapidly, and moreover explains why such a montgolfier cannot in any case undergo exothermic condensation, at least while the interior air is far from being saturated with water. On the contrary, the montgolfiers according to the invention function by obtaining the latent heat of condensation of the water vapor which they contain, from when, starting at a given altitude, the cooling of the interior air is, on the one hand, definitely superior to the reduction of the temperature of the dew point (2 K/km) and also is definitely less than the cooling of the external air (6.5 K/km). These values, displayed in FIG. 1, define the conditions of operation of a montgolfier according to this invention. When the ratio Ti/Te approaches its lower limit, the useful load diminishes but the exothermic condensation phenomenon increases at the same time as do the speed of ascent and the maximum altitude which can be attained. When the ratio Ti/Te approaches its upper limit, the maximum load per unit volume increases up to a plateau of 178 gr/m3, but the intensity of the exothermic condensation phenomenon diminishes, just as do the speed of ascent and the maximum altitude. In practice, these different cases of the figures are explored during the entire ascent of this montgolfier. The cumulative phenomenon described above starts from a given height determined by the conditions of takeoff, which are the load per unit of volume, the internal and external temperatures, and the relative saturation water vapor pressure. The phenomenon terminates at the moment when the relative water saturation pressure becomes insufficient for the provision of heat due to condensation of water vapor, consequent upon a given variation of temperature, to compensate for the thermal losses of the montgolfier (adiabatic expansion and losses through the skin). Subsequently the ascent continues for a short period, on the one hand due to the effect of the acquired speed, and on the other hand due to the effects of the moderate condensation of water vapor which continues until the interior air is no longer saturated with water vapor. After having thus attained its ceiling without provision of external heat, the montgolfier starts its descent. During the entire pseudo-adiabatic expansion of the saturated mixture, the condensed water falls as rain, fog, snow, or ice, according to the temperature, pressure, and saturation conditions of the external air. In practice, the quantity of heat produced by the condensation of water vapor varies as a function of the temperature at which the phenomenon appears. For example, at 300 K, the condensation of a gram of water vapor produces 2,400 joules, which increases the temperature of a kilogram of air by 2.4 K. The condensation phenomenon is directly linked to dPs/dTi, the variation as a function of temperature of the saturation water vapor pressure in the montgolfier.

In order to produce an effective exothermic expansion of the hot air saturated with water vapor of a montgolfier inflated according to this invention, it is necessary that the difference between the variation of its final temperature and that due only to the adiabatic expansion should be definitely greater (double, for example) than the difference between the diminution of the dew point temperature and that of the final temperature. This situation appears at sea level for air at 294 K saturated with water vapor, to which there corresponds a variation dPs/dTi=140 Pa/K. At sea level, this interior temperature of 294 K corresponds itself to a value dTi/dz of 5 K/km and to a maximum load per unit volume of 70 gr/m3, for a temperature Te of the order of 276 K. These are the minimum conditions to be fulfilled in order to be able to compensate locally for the loss of temperature caused by the adiabatic expansion due to an elementary [TN: infinitesimal] ascent dz, by heat supply from the condensation of water during this ascent. Of course, if it is desired for the phenomenon to continue until the tropopause, it is necessary to be dealing with air which is distinctly hotter, always with the reservation that the interior temperature Ti, necessary for the takeoff, has the ratio Ti/Te<1.17 to the external temperature Te. If this ratio is too close to this maximum, that is to say if the load per unit of volume is important [sic], the maximum altitude which this montgolfier can attain without supply of external heat reduces rapidly. For example, the ceiling is only about 5,000 meters for a load per unit of volume of 150 gr/m3, in the standard atmosphere.

According to a second characteristic of the present invention, on the one hand, at takeoff the montgolfier is only partially inflated and the temperature of the hot air saturated with water vapor which it contains is the greater the less the balloon is inflated and the greater is the load at takeoff per unit volume, and, on the other hand, a closure is installed in a relatively gas-tight fashion upon the opening of the thus inflated balloon, with the means of attachment of this closure being adapted to allow its automatic detachment when the pressure in the interior becomes a little greater than the pressure at the exterior.

Thanks to these arrangements, a montgolfier thus partly inflated and closed for a time (for example, half inflated with air saturated with water vapor at 306 K) rises much more quickly than does an open montgolfier, completely inflated according to the procedure of this invention, producing the same initial lift. In fact, with a montgolfier thus inflated and closed, exothermic condensation of water vapor is produced with much greater efficiency during the ascent. The phenomenon no longer occurs at constant balloon volume with the mass of gas decreasing, as in the case of an open montgolfier, but with a substantially constant mass of gas, because the volume of the closed balloon, partially inflated, increases to its maximum as its altitude increases. It therefore follows that the laws regulating the phenomenon by which a closed balloon is maintained in the air are different from those concerning an open balloon, and become Ti/Te=Cte and dTi/dz=-6.5Ti/Te K/km. For example, for a ratio Ti/Te=1.10, the maximum load per unit of volume at takeoff becomes 125 gr/m3 and the ratio dTi/dz=-7.5 K/km. The vertical gradient, thus authorized for Ti, is more important than in the case of a standard open montgolfier, because all the energy of the condensation of the water vapor is released inside the closed balloon, and because the efficiency of the phenomenon is therefore much increased. The process stops when the volume of the balloon attains its maximum and the internal pressure increases so as definitely to surpass the exterior pressure. The effect of this is to provoke an immediate detachment of the elastic fixing means of the closure and to put the balloon into the conditions of ascent of a standard open montgolfier. At this instant, at one and the same time this montgolfier is inflated with air particularly hot saturated with water vapor, is already placed at a relatively high altitude, and is also endowed with a high speed of ascent. This combination of conditions is particularly favorable for permitting the montgolfier to rise further, before exhausting all the latent heat of condensation contained in the charged water vapor.

According to a third aspect of the present invention, a montgolfier of the type which comprises a skin portion which is transparent and means of heating which exploit solar radiation, is characterized in that, on the one hand, at least the upper portion of the skin of the balloon is implemented by means of a plastic film which is at the same time transparent and absorbent vis-a-vis solar radiation, with a coefficient of absorption of around 20%, and, on the other hand, a screen which absorbs solar radiation as well as possible is arranged in the interior.

Thanks to these arrangements, the solar radiation which is absorbed by the partially transparent skin of the montgolfier keeps the temperature of this skin at a sufficient value to prevent condensation of water vapor thereupon, which would considerably reduce the amount of solar radiation impinging upon the screen inside the balloon, and would increase the losses by conduction through the skin. The radiation thus absorbed by the screen is a supplementary external supply of energy which is added to the heat produced by the condensation of the water vapor, and which substitutes itself for the latter when the phenomenon which causes the latter no longer appears. In this connection, it should be noted that the maximum value of the heat produced by water vapor condensation in a montgolfier of large size is approximately fifteen times greater than that provided by the absorption of solar radiation. At a given moment in the ascent of this montgolfier, the solar radiation thus absorbed can be sufficient to compensate for the thermal losses by adiabatic expansion and by conduction through the skin of the balloon, when the effects of the exothermic condensation of the water vapor in the air in the balloon have been exhausted. In this case, the force of Archimedes can stabilize itself so far as only to compensate for the weight of the balloon, which therefore remains at a constant altitude. If the solar radiation is sufficient for the force of Archimedes to remain greater than the weight of the balloon, the latter will continue to ascend. In this case, its average internal temperature continues to drop, provided that the balloon is below the tropopause and the ratio Ti/Te is less than 1.234. In any case, in order to maintain the speed of ascent of the balloon, the difference between the internal temperature and the external temperature should always be increasing, as indicated in FIG. 1. This imperative is all the more constraining when the volume of the balloon is great, because the thermal exchanges with the sun and with the external air are proportional to the surfaces concerned, while the mass of air to be warmed is itself proportional to the volume of the balloon.

The interior screen of a montgolfier according to this invention constitutes a source of energy of which the maximum, taking into account the coefficient of absorption of the skin, is 0.8 kW per square meter of the effective surface. With such a source of heat, the air inside the balloon is heated by the greenhouse effect. In fact, the screen behaves like a more or less perfect black body which, on the one hand, absorbs the solar radiation which impinges upon it through the partially transparent skin of the balloon, and, on the other hand, dissipates the energy thus transformed by convection. With a balloon of twenty meters in diameter, an absorbent screen is available whose effective surface can attain 314 m2, which means that it can generate 250 kW, which is a much greater quantity of energy than is needed to keep such a montgolfier in the air. [sic]

With the two types of energy which are exploited by a montgolfier which is perfected and inflated according to the three aspects of the present invention, the cost of an ascent with such a montgolfier is particularly low. The maximum altitude which can be attained and the speed of ascent are principally determined by the conditions in which condensation of water vapor can be produced. As for the duration of the flight, it principally depends upon the ambient intensity and duration of solar radiation. In these conditions, with good irradiation by sunlight, an open montgolfier of 100 meters diameter, provided with a transparent skin and an interior screen according to the present invention, and filled with hot air at 300 K upon takeoff, which at a given moment later becomes saturated with water vapor at 294 K, can carry a load of 25 tons (i.e. 50 gr/m2) to an altitude of 20,000 meters. During this ascent the tropopause is reached in 25 minutes, principally due to the effect of exothermic condensation of the water vapor which is charged (22 tonnes), and the final altitude [is reached] in about three hours, due to the complementary effect of the solar radiation absorbed by the screen.

If this montgolfier had been half inflated with air saturated with water vapor at a temperature of at least 306 K and its opening had been closed by means of a detachable [TN: strictly, "unhookable"] closure according to the present invention, the load could be increased to 50 tons, the time taken to ascend to the tropopause would fall to about 15 minutes, and the final altitude would become much greater than the previous maximum altitude.

The characteristics and the advantages of the invention will appear in a more precise manner from the following description, which is given by way of non-limitative example, and from the appended drawings, in which:

- FIG. 1 shows the curves commented upon above;

- FIG. 2 shows an axial section of a perfected montgolfier according to this invention.

Referring to FIG. 2, a montgolfier according to this invention comprises a balloon 10 which has an upper portion 12, substantially spherical, and a lower portion 14, substantially conical and opening downwards, with an opening diameter measuring from ten to fifteen percent of that of the balloon. The skin 16 of the balloon 10 is simultaneously gas-tight, relatively transparent and endowed with a solar radiation absorption coefficient around 20%, and strongly resistant to tension. To this end, it may be, for example, constituted as an assembly of gores [? panels ?] of polyethylene film, brown in color and twenty microns thick, welded along high resistance cords (carbon or kevlar). In such a case, the weight of a balloon of twenty meters diameter will be about thirty-five kilograms. The law of variation of tearing resistance of such a plastic film subjected to a relatively elevated temperature determines the maximum value of the temperature of the air saturated with water vapor which may be used to inflate the montgolfier.

The borders of the opening of the balloon 10 are solidly fixed to a circular collar 18 to which are attached, on the one hand, suspensions 20 which support a load 22, and, on the other hand, a detachable [TN: strictly, "unhookable"] closure 24, made from impermeable fabric and provided with an elastic border 26. The collar 18 comprises an exterior rim 28 on which the elastic border 26 of the closure 24 is engaged. In its center the closure 24 comprises a circular opening connected to a relatively long sleeve 30 which is provided with a narrow exit orifice. This central opening of the sleeve permits continual evacuation of the condensed water without allowing that of the interior air. Moreover, premature detachment [TN: strictly, "unhooking"] of the closure 24 cannot produce itself under the weight of this water. The diameter of the sleeve 30 measures about 10% of the diameter of the closure 24. The force of detachment [TN: strictly, "unhooking"] of the elastic border of the closure, engaged upon the rim of the collar 18, corresponds, for example, to an excess of interior pressure of around 50 Pascals. The diameter of the collar 18 has been chosen sufficiently large so that, after the detachment [TN: strictly, "unhooking"] of the closure 24, the interior air can escape with a low pressure difference, for example less than 20 Pascals.

In the interior of the balloon 10, at regular intervals around a great horizontal circle 34 of the spherical portion 12 and around four other great circles separated from one another by angles of about ten degrees, there are fixed buckles such as 36-38-40-42. To these buckles there are hooked carabiniers (not shown) fixed upon the periphery of a screen 44 of substantially circular shape, made from a thin black material, for example from a foil of plastic or of anodized aluminum. In its center, the screen 44 has an opening 46, of average diameter comparable to that of the opening of the balloon. Under its own weight, the screen 44 takes the form of a truncated cone more or less deformed, directed towards the base.

When the balloon 10 is to be used with a screen 44 which is sustained by the buckles 40-42 which are arranged around a great circle more or less inclined with respect to the horizon because, at the time and place concerned, the sun is only moderately elevated, or, on the contrary, because the sun is at a very high elevation in the sky, then it is therefore necessary to orient the axis of the screen 44 to the same azimuth as the sun, in order to have the best effective surface for the screen. To this end, an orientation means 48 comprising a propeller 50 whose axis is ortho-radial [TN: perpendicular to a radius], driven by an electric motor 52, is fixed to the exterior of the balloon at the level of its equator. This motor 52 can be fed by a battery or by solar panels either in one direction or in the other. For a balloon of twenty meters in diameter, an electrical power of ten watts and a propeller of fifty centimeters in diameter are quite enough to correct the orientation of the screen in a few minutes and/or to make it constantly follow the movement of the sun.

A montgolfier according to this invention, twenty meters in diameter, filled upon takeoff with air sufficiently hot and humid to be able to have, at a given moment, a dew point at a temperature of at least 294 K, can theoretically carry a load of 250 kg (i.e. 60 gr/m3) to any altitude compatible with human resistance in the absence of an oxygen reserve, and moreover can do this during the entire time that the location in question is irradiated by sunshine. Accordingly it constitutes a perfect leisure montgolfier. After having inflated the balloon of such a montgolfier using conventional means (a fan), it should be pre-heated by means of a fixed propane burner, into whose flame a a water spray should be injected. The altitude of such a montgolfier is controllable in two ways. The first way consists of making it turn upon its axis, using the orientation propeller. In this manner, it is possible to position the screen to a state in which its surface is minimally effective, and is insufficient to maintain the temperature difference necessary to produce a lift which balances the weight of the craft. The second way consists of using conventional means, for example opening a valve positioned at the top of the balloon.

It will be noted that during the entire descent of a montgolfier the interior air is compressed in order to stay in equilibrium with the external air. Due to this fact, as during the ascent, the internal temperature will rise more than the external. This has the effect of stabilizing the speed of descent.

A montgolfier provided with a fixed screen according to this invention, two meters in diameter and having a total weight of two hundred grams, can be well warmed by sunlight, and can rise to several hundred meters. If tied to the ground by a string, it can be an interesting new toy which can be very rapidly inflated by a portable hair dryer, preferably connected to the balloon by a fabric sleeve kept wet. It will be noted that, for this particular application, the three complementary aspects of the present invention may not be mutually associated.

A montgolfier according to this invention of one hundred meters in diameter can be filled quite rapidly by means of a double-flux [sic] reactor, associated with a chamber which is adapted to humidify and cool the jet of hot gases which is produced, by means of a curtain of water jets. In favorable conditions, such a montgolfier, perfected and inflated according to this invention, can carry a load weighing up to 50 tons to an altitude of 30 kilometers (the case of a montgolfier half inflated, filled with air saturated with water vapor at a temperature of at least 310 K and closed for a time with an automatically detachable closure), in conditions which are particularly interesting from the point of view of economy. Such a load might be, for example, an aerial vehicle equipped with a statoreactor [sic] [? ramjet ?], which could be brought to its starting [priming] speed of around 500 m/s after a rebound [?] effected at the end of a dive of 15,000 meters.

CLAIMS:

1. Procedure for inflating a montgolfier, characterized in that it consists of using for this purpose hot air sufficiently humid for exothermic condensation of the water vapor which it contains to occur during the ascent of the balloon, at least from a certain altitude.

2. Procedure for inflating a montgolfier according to Claim 1, characterized in that, at the moment of takeoff, the temperature of the dew point of this air is at least equal to 294 Kelvins.

3. Procedure for inflating a montgolfier according to Claim 1, characterized in that the average temperature Ti of the interior air needed to stay in the air has a ratio Ti/Te to the external temperature Te less than 1.17.

4. Procedure for inflating a montgolfier according to Claim 1, characterized in that the load per unit volume of the montgolfier when completely inflated is less than 70 gm/m3.

5. Procedure for inflating a montgolfier according to Claim 1, characterized in that, at the moment of takeoff:

- the temperature of the dew point of the interior air is substantially greater than 294 K;

- the balloon is incompletely inflated; and

- the opening of the balloon is obstructed in a relatively gas-tight manner and is adapted to remain so until the volume of the balloon becomes constant and the interior pressure becomes somewhat greater than the external pressure.

6. Montgolfier of the type comprising a balloon (10) open at the base and a load (22), characterized in that, at the moment of takeoff:

-it is incompletely inflated;

- the interior air is saturated with water vapor at a temperature substantially greater than 294 K, said temperature being further the greater the less the balloon is inflated and the greater is the load per unit volume;

- the opening of the balloon (10) is closed by a closure (24) adapted to detach [TN: literally "unhook"] itself automatically when the difference of pressure between the interior and the exterior exceeds a certain threshold.

7. Montgolfier of the type comprising a balloon (10) open at its base, a layer portion which is made from a transparent material, means of heating adapted to exploit solar radiation, and a load hanging from the balloon;

- characterized in that:

- said transparent layer portion of the balloon is its upper portion (16);

- said material is a plastic film, at the same time transparent to and absorbent of solar radiation, with a coefficient of absorption of about twenty percent; and

- a screen (44), adapted to absorb solar radiation efficiently, is arranged in the interior of the balloon (10).

8. Montgolfier according to Claim 7, characterized in that, on the one hand, the diameter of the opening provided at the base of the balloon (10) is sufficiently great for a feeble difference of pressure to be maintained between the interior air and the exterior air, when the balloon gains altitude, and in that, on the other hand, the screen (44) comprises in its center an opening (46), of diameter close to that of the opening of the balloon.

9. Montgolfier according to Claim 7, characterized in that, with the upper portion (12) of the balloon being substantially spherical:

- fixing means (36-38) are arranged at regular intervals along a horizontal great circle and along several other great circles, spaced by about ten degrees from one another;

- attachments, adapted to cooperate with said fixing means, are arranged around the periphery of the screen (44); and

- a propeller (50), with an ortho-radial [TN: perpendicular to a radius] axis and unitary with the shaft of an electric motor (52) is fixed to the external skin of the balloon, near its equator, in order to be able to orient the screen (44) with respect to the sun.

10. Montgolfier of very large dimensions according to Claims 6 and 7, characterized in that the useful load (22) is an aerial vehicle equipped with a statoreactor [sic].

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