Process for altitude-stabilizing a balloon, and atmospheric balloons for implementing this process

A process for altitude-stabilizing an atmospheric balloon comprising ballast jettison mechanism to vary the balloon's specific weight, and using a balloon provided with an interpole link for actuating said ballast jettison mechanism so that an increase in the tension in the link causes a reduction in the specific weight of the balloon by jettison of ballast is disclosed.

This invention relates to an altitude-stabilization process for an 
atmospheric balloon comprising means for varying specific weight, such as 
jettisoning means, means for evacuating aerostatic gases, or also means 
for adjusting the heat transferred to the air contained in the balloon if 
the aerostatic balloon is of the hot-air type. The invention also covers 
atmospheric balloons designed to implement said process. 
BACKGROUND AND OBJECTS 
It is known that the balloon equilibrium at a given altitude in the 
atmosphere depends on the displaced volume of air of which the mass must 
be balanced by the sum of the solid and gaseous masses carried by the 
balloon. Stable equilibrium is achieved at a given altitude when the 
vertical balloon displacement takes place in the presence of at least one 
parameter being modified (which concerns the balloon or the ambient 
atmosphere), tending to return the balloon to its starting point. 
Thus, only a pressurized balloon within which the pressurized gas always 
remains at constant volume is inherently stable at a given altitude. A 
balloon which is open at its lower part is stable in ascent due to the 
natural evacuation of the aerostatical gas that takes place at constant 
volume; but on the other hand it is unstable in descent when its volume 
decreases. A balloon far from its filled state (i.e., when limp) is 
unstable and rises or descends depending on the thermal balance 
controlling its gas-bulb volume and the change in the gas mass (such a 
change being caused by diverse phenomena and in particular being due to 
diffusion through the envelope. 
Now it is often desired in many missions (particularly scientific missions) 
to keep a balloon for some time at a constant altitude or only slowly 
varying its altitude in ascent or descent at a given altitude or at 
several desired altitude levels. Frequently the altitude levels that are 
desired correspond to a limp balloon state. 
To assure this stabilization (where this term means both staying at a 
constant altitude and rising or descending in controlled manner), the 
generally adopted procedure is to modify the specific weight of the 
balloon by either jettisoning ballast or evacuating part of its aerostatic 
gas. These operations are initiated by electromechanical systems which in 
some instances are ground-controlled by a remote radio-electric control, 
and in other cases from the balloon by pick-ups mounted to it which 
measure certain parameters, typically the temperature and the atmospheric 
pressure, which after analysis allow effecting the controls. However the 
ambient atmosphere as a rule will not be calm due to vertical winds, 
turbulence etc., and it is a fairly complex matter to collect useful 
parameters. The corresponding equipment, which must be functional through 
the entire balloon lift and sometimes in a harsh environment, strongly 
deviates from the ideal rated operation of the electronic and supply 
circuits (temperatures less than -100.degree. C. or exceeding +100.degree. 
C.), and such equipment is complex, costly and heavy. Moreover, it 
generally uses up a lot of ballast and accordingly is poorly suited for 
the atmospheric-planet type of exploration wherein the total balloon mass 
must be as low as possible (the balloon is understood to be the balloon 
proper and all material therein). 
The object of the present invention is thus to overcome the drawbacks of 
the conventional systems and to provide an altitude-stabilizing system for 
a balloon. The invention, deals with a process for stabilizing an 
atmospheric balloon of the type comprising means to vary its specific 
weight, in particular jettisoning means designed to reduce the balloon 
mass, means for evacuating the aerostatic gas, or, in the case of a 
hot-air balloon, a burner fed by a fluid fuel. 
A particular object of the invention is to assure balloon-stabilization by 
using substantially simplified equipment of which the cost and the weight 
are significantly reduced with respect to those of conventional systems. 
Another object is to create novel balloon forms which are better suited to 
missions which include predetermined-altitude stabilizations. 
To that end the process of the invention for altitude-stabilizing an 
atmospheric balloon and comprising means to vary its specific weight 
comprises the use of a balloon provided with an inter-pole link extending 
from its upper to its lower poles and in controlling means designed to 
vary the balloon's specific weight using this inter-pole link in such a 
manner that an increase in the tension T applied to said link shall act on 
these means to reduce the specific weight. 
The term "inter-pole link" denotes any component or assembly of components 
of longitudinal shape extending between the poles of the balloon and 
physically fastened either to the poles themselves or near them, or to 
auxiliary manner, this link as a rule will be flexible and can be one 
cable, several cables, one flexible sleeve or several sleeves, etc. 
The balloon being used can be of the type described in the French patent 
application 80.00343 filed by the applicant on Jan. 4, 1980 (or U.S. Pat. 
No. 4,420,130) and evincing an envelope with symmetry of revolution about 
one axis and comprising an approximately cylindrical portion. 
The length L of the inter-pole link is adjusted as a function of the 
contemplated mission to a value depending on the natural distance D.sub.p 
between the two poles when the balloon is filled. To keep the balloon limp 
at a constant altitude or at a slowly varying altitude, this length L 
generally shall be adjusted to a value L.sub.o .gtoreq.D.sub.p. 
When the balloon in its filled state is descending, the distance D between 
the poles increases from the value D.sub.p. In the absence of the 
inter-pole link, this distance might grow to a limiting value D.sub.F very 
close to the envelope gore length. In the presence of the inter-pole link, 
which exceeds D.sub.p but is less than D.sub.F, when the inter-pole 
distance D becomes equal to the length L.sub.o of the link, a tension T 
arises in the link which increases as the descent continues and can 
decrease only if the balloon rises again. 
According to the invention this tension T is used to actuate means for 
varying the balloon's specific weight: when this tension exceeds a 
threshold, it acts on these means to reduce the specific weight, whereby 
the descent is decelerated and the balloon is stabilized. 
In the case of a balloon equipped with jettison means known per se, these 
means are controlled by the inter-pole link so as to cause jettison when 
the tension T exceeds a predetermined tension threshold t.sub.d. 
In the case of a hot-air balloon equipped with suitable combustion-fluid 
burners, the combustion rate is controlled by the inter-pole link in such 
a manner that said rate increases when the tension T exceeds a given 
threshold t.sub.d '. 
For some missions and some balloon types, the descending stabilization 
implemented by the above defined process will be enough (considering in 
particular the natural ascent stability of certain balloons, as already 
mentioned). 
In other cases however a balloon is used which comprises means for varying 
its specific weight both by lowering and increasing it. In the process of 
the invention, these means are controlled by the inter-pole link so that 
an increase in the tension T in said link acts on these means to reduce 
the specific weight and a decrease in said tension acts to increase said 
specific weight. 
With respect to an atmospheric balloon comprising both jettison means and 
aerostatic gas evacuation means, the link controls the jettison when its 
tension exceeds the threshold t.sub.d and controls the evacuation when 
this tension drops below a threshold t.sub.e &lt;t.sub.d. To stabilize the 
balloon at a desired altitude level, it suffices to adjust the length L of 
the inter-pole link and the thresholds t.sub.e and T.sub.d so that the 
tension T in the link at the altitude of the desired level be between 
t.sub.e and t.sub.d. The link is inactive as long as its tension remains 
between these values (that is, as long as the balloon remains at the 
desired altitude level). If, for some reason, the balloon should begin the 
descend, the tension T increases and beyond the threshold t.sub.d causes a 
jettison whereby the descent is stopped and a new ascent takes place. If 
on the other hand the balloon should rise, the tension T drops, and below 
the threshold t.sub.e causes evacuation of the aerostatic gas, whereby the 
rise stops and a new descent takes place. It must be borne in mind that 
the condition t.sub.e &lt;t.sub.d prevents simultaneous occurrence of 
jettison and aerostatic gas evacuation. 
In the case of a hot-air ballon, the combustion-gas flow-rate is controlled 
by the inter-pole link so as to increase from an equilibrium value when 
the tension T in the link rises above the threshold t.sub.d ' and to 
decrease from this equilibrium value when the tension T drops below a 
threshold t.sub.e '.ltoreq.t.sub.d '. 
The present invention also covers an atmospheric balloon to implement the 
process described above. This balloon comprises an envelope made of a 
flexible hermetic material, a jettison reservoir located below the 
balloon, a jettison member associated with the reservoir to cause a 
controlled jettison of ballast, and, possibly, an aerostatic gas 
evacuation aperture in the ballon envelope with a movable sealing member 
for this aperture. In the present invention, said balloon is provided with 
an inter-pole link between its upper and lower poles, said link being 
fastened to the jettison member so as to act on it beyond a predetermined 
tension-threshold t.sub.d ' and where such is present, also fastened to 
the movable sealing member so as to close it beyond a predetermined 
tension threshold t.sub.e. 
The invention furthermore covers a hot-air aerostatic balloon comprising an 
envelope made of a flexible, hermetic material and open at its lower part, 
a burner hooked-up in the vicinity of this lower pole, and means for 
supplying the burner with combustion fluid from a tank. According to the 
invention, the aerostatic balloon comprises an inter-pole link between the 
upper and lower poles of the balloon, the link being fastened to the 
burner supply means so as to adjust the combustion fluid flow rate as a 
direct function of the tension in said link.

DESCRIPTION OF THE INVENTION 
The atmospheric ballon illustratively shown in FIGS. 1 and 2 is a 
pressurized balloon consisting of an envelope 1 of which the upper and 
lower poles 2 and 3 respectively are joined by a link 4. A basket 5 
associated with jettison means 6 is located below the lower pole 3. 
The envelope 1 can be made by the method described in French patent 
application No. 80.00343 (or U.S. Pat. No. 4,420,130) mentioned above 
using a plurality of polyethylene film gores capable of withstanding the 
tangential tensions in all the directions in its plane (i.e., 
circumferential and longitudinal ones). These gores are provided with a 
rectangular segment so that their assembly at the edges enables formation 
of a cylindrical portion 1a extended at the top and at the bottom by 
segments coverging toward the poles of the balloon. 
The link 4 can be flexible but non-stretching cable. In this example, this 
link is fastened in the vicinity of the upper pole to a disk-shaped piece 
to which are fixed the upper gore ends of the envelope. At the bottom, 
near the lower pole, the link 4 is coupled to the jettison means as shown 
in FIG. 2 so as to act on these beyond a tension threshold t.sub.d applied 
to this link. 
In the example, the jettison means comprise a tank 7 for a fluid kept 
pressurized by a pressurizing gas 5 separated from the fluid by a flexible 
membrane 8. The fluid constituting the ballast can be in particular liquid 
freon which will vaporize upon release. 
The tank 7 comprises an output orifice with which cooperates a valve 9 
acting as the jettison member. The valve 9 is housed in a cylindrical body 
10 supported by the balloon and acting as the connection between this 
balloon and the basket. The body 10 is perforated with evacuation holes 
such as 11 to permit the escape of the ballast fluid to the outside when 
the valve 9 is open. 
Near the lower pole, the link 4 is designed to penetrate in an essentially 
hermetic manner the body 10 and it is fixed at its lower end to the 
jettison valve 9. Elastic means such as the spring 12 are arranged in the 
body 10 so as to force the valve toward its closed position. This spring 
12 is calibrated and permits adjusting the tension threshold t.sub.d 
beyond which the link 4 controls the valve opening. 
The forces acting on the valve are the following (FIG. 3): 
the link tension T direct upward, 
the force p.sub.s also directed upward and caused by the pressure p of the 
fluid on the valve (surface s) 
the downward return force of the spring, equal to R in the closed state. 
Accordingly the valve 9 opens at a tension threshold t.sub.d =R-ps and 
remains open as long as the tension T.gtoreq.t.sub.d. 
With K the spring coefficient, the upward displacement .DELTA.x of the 
valve is given for a tension T.gtoreq.t.sub.d in the link by 
.DELTA.x=K(T+ps-R). 
Therefore this displacement is proportional to the tension T, whereby the 
jettisoned mass is directly related to the tension T and to the duration 
in which this tension T is effective. This enables stabilization of the 
balloon at an altitude which is a function of the system parameters and 
with oscillations of which the amplitude also depends on these parameters. 
In the examples of FIGS. 2 and 3, the valve 9 operates symmetrically, that 
is, the tension threshold t.sub.d at which this valve opens is equal to 
the threshold at which it also closes again (the effective valve area 
acted on by the ballast fluid being the same whether the valve is open or 
closed). 
Under these conditions, the balloon oscillations are damped and the balloon 
tends to stabilize at an equilibrium altitude. FIGS. 4a through 4e and 5a 
through 5e schematically show the behavior of such a balloon. The balloon 
is assumed to be initially entirely filled at a maximum altitude (FIG. 
4a). The length L.sub.o of its link between the poles is adjusted to a 
value exceeding the natural distance D.sub.p separating the poles in this 
condition -- the link is loose and the jettison valve is closed (FIG. 5a). 
If it is assumed that by a diffusion phenomenon (or any other such 
phenomenon as calibrated leakage, evacuation of aerostatical gas. etc.) 
the balloon begins descending, the envelope deforms and the inter-pole 
distance increases until it equals the link L.sub.o (FIG. 4b), and a 
slight tension T appears in the link (FIG. 5b). This tension is less than 
the threshold tension t.sub.d and the balloon continues descending. 
The tension T increases until it exceeds t.sub.d (FIG. 4c); the valve 9 
then opens and causes the initiation of jettison (FIG. 5c). 
The descent rate of the balloon decreases until it is null and the balloon 
rises again to return to its link tension t.sub.d (FIG. 4d). The valve 
closes again and stops the ballast discharge. 
The rate of rise decreases until it is null, and the balloon peaks at an 
altitude lower than that of its wholly filled state (FIG. 4e). The link 
remains taut but the tension in it is less than the threshold t.sub.d. In 
this manner the balloon can be stabilized by means of a trajectory 
consisting of a sequence of damped oscillations, one of which is 
graphically illustrated in FIG. 6. 
As regards the variation shown in FIG. 7, the valve 13 operates 
asymmetrically and comprises a heel 13a with an effective area S larger 
than the area s of the part applied to its seat. When such a valve is 
closed, it will require the tension T to become the threshold t.sub.d to 
open, but thereupon it will also close again once this tension becomes 
less than a different closing threshold .theta..sub.d, where .theta..sub.d 
&lt;t.sub.d. Thus, once open, the valve remains in this state as along as the 
tension exceeds .theta..sub.d. 
Under these conditions it is possible to achieve balloon stabilization at 
larger and undamped vertical oscillations. This arrangement is especially 
significant in order to explore an atmosphere within two specified 
altitudes. 
The partial view of FIG. 8 shows another embodiment mode wherein the 
balloon consists of an envelope 14 of the same type as before but where 
the inter-pole link 15 comprises jettison means 16 located underneath the 
lower pole and similar to that described above; aerostatic gas evacuation 
means 17 located near the upper pole; and means 18 regulating the length 
of the inter-pole link 15. 
The evacuation means 17 consist of an evacuation aperture 19 in the 
envelope and of a movable member 20 to seal said aperture. The inter-pole 
link 15 is coupled at the top to this member 20 to actuate it toward 
closure beyond a predetermined tension threshold t.sub.e. 
In the example, the closure member 20 consists on one hand of a valve 
located opposite to and below a support means surrounding the evacuation 
aperture 19 and on the other hand of reversing levers 21 rigidly fixed to 
the envelope by brackets 22 fastened along the length of said levers. Each 
reversing lever 21 is connected at one end to the valve 19 and at the 
other to the inter-pole link 15 by means of auxiliary cables 23, whereby a 
tension T from the link toward the bottom tends to actuate the valve 19 
toward closure. 
This valve functions together with elastic means such as the spring 24 
whereby it is acted on in the direction of its open position. This spring 
is calibrated so as to adjust the evacuation-tension threshold t.sub.e to 
a predetermined value (a threshold below which the valve 20 is open and 
above which it is closed). If the jettison-tension threshold is t.sub.d, 
the calibration is such that t.sub.e &lt;t.sub.d. 
Thus, if the tension T is less than t.sub.e, the aerostatic gas will be 
evacuated and the balloon tends to descend or to decelerate any rise; if 
the tension T is between t.sub.e and t.sub.d, there is neither jettison 
nor evacuation of the aerostatic gas, and no action is exerted on the 
balloon by the means of the invention. Lastly, if the tension T exceeds 
t.sub.d, there will be jettison and the balloon tends to rise or to 
decelerate any descent. 
Consequently the balloon tends to return within an altitude range 
corresponding to t.sub.e .ltoreq.T.ltoreq.t.sub.d. For jettison means 16 
and evacuation means 17 of specific parameters, this altitude range can be 
adjusted by controlling the length L of the inter-pole link to an 
appropriate value larger than or equal to the natural distance D.sub.p 
between the poles for the filled balloon state. 
In the example of FIG. 8, the balloon is provided with adjustment means 18 
acting on said length and capable of providing this length in several 
values L.sub.1, L.sub.2 . . . in accordance with a predefined program. The 
balloon therefore is designed to successively explore several altitude 
ranges. 
In particular these adjustment means 18 may comprise means such as the drum 
25 for winding the link, rotational drive means such as the winch 26 for 
said winding means, and control means such as the control logic 27 acting 
on the winch in predetermined sequences. The assembly can be supported 
from the envelope by a support plate 28 preferably located near the lower 
pole (though it may also be located near the upper pole). The control 
logic 27 can be preset to assure the application of a predetermined 
program, it can also be implemented by remote control. 
Illustratively FIGS. 9 and 10 additionally show the application of the 
invention to a hot-air balloon. This balloon consists of an envelope 29 
made of a flexible material and open at its lower pole, and possibly with 
a cylindrical segment as previously described. This balloon is provided 
with a burner which in this example consists of a circular flame array 35 
connected to supply means comprising a control-casing 36 for the gas-flow 
rate and a pressurized reservoir 37. This casing and the flame array are 
mounted on a rigid support 38 connected to the basket 39. 
The hot-air balloon is provided with an inter-pole link 31 extending from 
its upper pole to its lower pole; this link is fastened to the casing 31 
supplying the burner in such a manner that the combustion-fluid flow rate 
is directly controlled by the tension in said link. At its lower part the 
link is protected by a thermal protection cone 40 with an aluminized outer 
surface. 
The link 31 can act on a pivot lever 32 controlling a sealing valve in the 
burner supply circuit and diagrammatically indicated by 33. A return 
spring 34 cooperating with a calibration system allows adjusting the 
equilibrium altitude as a function of the various system parameters. 
If the descent drops below this altitude, the tension increases and causes 
a higher combustion-gas flow-rate with respect to its equilibrium value. 
The temperature of the rise-gas increases and the descent rate drops until 
the balloon stops and rises again. 
When rising and exceeding the equilibrium altitude, the mechanism proceeds 
in the reverse sequence and the balloon then is made to descend due to a 
drop in the gas temperature. 
While this invention has been described as having a preferred design, it 
will be understood that it is capable of further modification. This 
application, is therefore, intended to cover any variations, uses, or 
adaptations of the invention following the general principles thereof and 
including such departures from the present disclosure as come within known 
or customary practice in the art to which this invention pertains, and as 
may be applied to the essential features hereinbefore set forth and fall 
within the scope of this invention or the limits of the claims.