Sub-orbital high-altitude telecommunication system

The invention relates to a method and system for wireless sub-orbital communication.

In particular, the invention relates to a long-term telecommunications system located at high altitude in the suborbital plane, which is outside of any system physically associated with earth and whose components remain high at the station for a long time.

Known wireless communication systems use either ground-based or space-based infrastructures (satellites). Ground-based systems include radio masts and antennas located on tall buildings, slopes, and the like. Balloons tied to the ground are also used here. The spatial systems are based on satellites equipped with telecommunications devices.

Terrestrial wireless communication systems have been known since the early days of radio. The configuration range of these systems ranges from simple one-way and two-way radio connections, as well as radio and television broadcasting networks, to sophisticated cellular networks and the proposal of Personal Communications Network (PCN).

Relay stations are designed to transmit and receive radio transmissions to and from various locations. Because they are located on or near the ground, their radio signals tend to propagate more horizontally than vertically. Thus, each relay station has a limited range of transmitting and receiving signals. The reach of radio signals is limited due to: horizon problems due to the curvature of the earth; from uneven terrain, from trees and from tall buildings in the path of propagation. There is also interference from other signals or reflections of the transmitted signal. There are also attenuation problems resulting from undesirable absorption of the transmitted signals.

In order to increase the range, higher power devices are used and / or the height of the relay stations is increased. Increasing the power helps to solve the problems of attenuation and the problem of interference from other signals, but does not solve problems arising from the curvature of the horizon line, line of sight, and noise from the reflected signal. Therefore, it becomes advantageous to increase the height at which the relay stations are placed. They are placed on towers, tall buildings and mountain tops. This reduces the problems associated with the horizon and line of sight, which increases the range of the relay station and slightly reduces attenuation and interference from reflected signals. Unfortunately, for geographic or political reasons, it is not always possible to locate the relay stations in optimal locations, due to difficulties in obtaining permission from the landowner or the government.

Such inconvenience may be alleviated to some extent when wireless telecommunications devices are lifted by tethered balloons. However, tethered balloons have their drawbacks. When the balloons are tied at low heights, their range will not be greater than the range of the relay station located on the tower or on the roof of a tall building. It is then difficult to justify the cost of installing the balloon. Also because the work of the balloons depends on the weather conditions and the wind that prevails on them

180 378 heights, the balloons can be easily damaged, which will be associated with their frequent replacement.

On the other hand, if the balloons are tied at altitudes allowing the transmission of telecommunication signals over a fairly large area, making them economically viable, independent of the weather conditions, and durable in use, both the balloons and slings become unsafe for airplanes. The ties themselves are exposed to stresses caused by the weather. Moreover, it is highly likely that the tether of a damaged balloon will be scattered hundreds, if not thousands or tens of thousands of feet, causing damage and posing a risk of injury to people. In addition, if the sling falls on electrical cables, there is a risk of fire and power failure.

These drawbacks make tethered balloons inconvenient to use as components of a telecommunications system whose devices have to operate for extended periods of time.

To overcome the limitations of terrestrial wireless telecommunications systems, space-based telecommunications systems are built using satellite techniques that have been developing since the early days of Sputnik (1957). Satellite systems in geosynchronous orbits (approximately 35 km) have been in use for many years and are largely reliable. Their main advantage is their high altitude, which allows one satellite to transmit and receive signals from an area on the earth covering hundreds of thousands of square kilometers. However, the production costs, launching and locating the satellite in orbit are high, as well as their replacement. For this reason and due to the extremely difficult operation of these facilities, special attention should be paid to their reliability.

Moreover, due to the high altitude of the satellite, there are radio transmission delays of approximately 1/8 second in each direction. This significantly limits the satellite's ability to carry and connect normal two-way (duplex) voice communications. Also due to their high altitude, radio communication equipment requires a higher power supply than comparable terrestrial equipment. This increases costs and affects the weight and size of equipment installed both in the satellite and on the ground.

When a satellite fails, which must inevitably happen, both in terms of electronics and loss of orbit, attempts to recover or repair it are extremely costly. Moreover, such attempts, whether successful or unsuccessful, pose the risk of damage or loss for both personnel and equipment. On the other hand, a damaged satellite may remain in orbit. It becomes just one more piece of cosmic junk until it loses its orbit so much that it travels through the atmosphere to the earth. If the satellite is not completely destroyed during this fall, it can cause injury and damage to people and property.

To solve the problems associated with the operation of existing high-altitude satellite systems, it has been proposed that the satellites orbit at altitudes of about 800 km or about 8000 km. This lowers the power demand and reduces time delays, but at the same time causes other inconveniences. The point is, at these lower altitudes, the satellites are not geosynchronous. Therefore, during one particular connection, telecommunications signals would have to be transmitted between several satellites. This is because the circumferential position of each satellite relative to the earth is constantly changing. Thus, a satellite over a ground station at the beginning of communication may orbit during the communication to such an extent that it will lose the signal from that station. In order to maintain the connection, the signal from the ground will have to be passed to another satellite that is closer to this ground station. For this to happen, satellites need to be programmed. Thus, very complex program features must be implemented. In addition, the manufacturers have not yet agreed on the optimal heights, angles of signal propagation and how to deal with Dopier shifts. Moreover, the orbits of the satellites, due to their low altitude, will be lost faster than the orbits of satellites located at higher altitudes. Thus, both satellites and devices on

180 378 installed, will have to be replaced more frequently, which again will significantly increase the operating costs of the system.

GB-A-2082995 discloses a lightweight device adapted for air transport which is capable of positioning in the upper atmosphere and functioning as a telecommunications relay station. The device comprises means for generating a lifting force drawing energy from the environment, for example by means of solar panels.

Patent FR-A-2282366 discloses a method of destroying a balloon by means of remote control of the load while returning to the ground using a parachute.

EP-A-0371529 discloses a balloon in which the gas temperature is regulated by the amount of solar energy entering the balloon.

An Odyssey balloon designed by Albuquerque, New Mexico was disclosed in the New York Times of June 7, 1994, Chapter C, p. 1. The method of controlling the height of this balloon is to equip it with a central expandable chamber, filled with a gas lighter than air, which is surrounded by a virtually non-expandable outer chamber filled with air. Compressed air is blown into the outer chamber to reduce the height, and air is released from the outer chamber to increase the height.

The presented problems can be significantly reduced by the use of telecommunications infrastructure with permanently high suspended, repairable telecommunications stations. These devices maintained at a predetermined position in the sub-orbital plane could receive telecommunications signals from a ground station and transmit them to another similar high-mount station or to another ground station.

As the propagation of radio signals to and from the relays is rather vertical, the problems of line of sight, reflection and attenuation would be minimized in this way. It would be unlikely that high buildings, trees, or obstacles would block, reflect or absorb radio signals. This means that to send a signal over a given distance, less power would have to be used than if the signal was transmitted horizontally or close to the ground. In addition, since such a system would operate at altitudes less than ten percent of the altitude proposed for the lowest satellite systems, the transmission of telecommunications signals would require less power and the problem of the magnitude of transmission delays would be neglected.

This will be solved by a relatively cheap, efficient wireless telecommunications system, without the economic and physical constraints of terrestrial network infrastructures, tethered balloon systems or space-orbiting infrastructures.

A method of suborbital wireless communication, which consists in placing at least one relay station at a height predetermined for receiving and transmitting telecommunications signals to and from earth stations and other relay stations, transmitting a telecommunications signal from one of the earth stations, receiving it at this set relay station and then transmits to the second earth station, wherein, during the transmission and reception of telecommunications signals to and from the earth stations and other relay stations, the set relay station is maintained at a predetermined height, which according to the invention is in the range from 19 to 56 km, and the movement of this relay station is controlled at this method, that, once the current height and / or position above ground of a relay station has been determined and a predetermined height and / or position of that relay station has been identified, it is moved from the current height and / or position to the predetermined height and / or position.

Preferably, the relay station is positioned above ground at a predetermined height by inflating its balloon with gas in response to a signal from the mobile earth station and brought to a predetermined position on the ground by discharging gas from the balloon in response to a signal from the mobile earth station.

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Preferably, the height of the relay station is controlled by changing the gas temperature in the balloon, and the gas temperature is controlled by controlling the amount of solar radiation energy that enters the balloon.

Preferably, the amount of solar radiation entering the balloon is controlled by changing the transparency of the balloon coating.

Preferably, the relay stations over the more densely populated areas are placed at lower heights than the relay stations over the less populated areas.

Preferably, relay stations located above the more densely populated areas are set to narrow focus angle for receiving and transmitting telecommunications signals, and relay stations located above less populated areas are given a wide focus for receiving and transmitting telecommunications signals.

Preferably, the lateral displacement of the relay station is accomplished by applying a thrust to it in the direction in which it is to move.

Preferably, energy stored in or received by a relay station is used to generate the thrust and to transmit and receive telecommunications signals.

Preferably, the energy stored or received in the relay station is solar, microwave, wind or chemical energy.

Preferably, when the relay station is composed of sections, telecommunication signals from and to the earth stations and / or other relay stations are selectively received and transmitted in at least one of these sections, to which the communication energy is transmitted from at least one of the sections. other sections of this relay station.

Preferably, telecommunications signals from and to the earth stations and / or the remaining relay stations are received and transmitted selectively in at least two sections of the relay station, and in the event of loss of the ability to transmit and / or receive telecommunications signals through one of these sections, transmission and / or or receiving the telecommunication signals in the second section, and thus the continuity of operation of the relay station is maintained.

Preferably, the energy transferred between the relay station sections is microwave energy that is converted into electricity and used for telecommunications communication.

Preferably, the suborbital telecommunications signals are assigned the same frequencies as the frequencies assigned to terrestrial communications telecommunications signals.

Preferably, the communication signal from the first earth station is transmitted to the first relay station, then it is transmitted from the first relay station to the second relay station and then from the second relay station to the second earth station.

A sub-orbital wireless communication system comprising at least two earth stations with transmitters and receivers of telecommunications signals and at least one relay station with a receiver and transmitter of telecommunications signals located at a predetermined height above the ground and equipped with devices to control the vertical movement of this relay station to a predetermined height, and staying at this altitude, according to the invention, it is characteristic that at least one relay station is brought to a predetermined height, which is in the range 19 to 56 km, the relay station also comprises devices controlling the horizontal displacement of the at least one relay station to a predetermined position and maintenance. her in this position, the devices being comprised of devices for selectively or simultaneously identifying the actual and predetermined height or position of the relay station, and devices for moving it from a current height or position to a predetermined height or position.

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Preferably, the devices controlling the displacement to a predetermined height and / or position include a drive system and a system for selectively activating said drive system.

Preferably, at least one earth station is connected to the basic earth telecommunications network.

Preferably, at least one of the earth stations is a mobile station.

Preferably, the relay station's horizontal displacement control devices include a drive system and an electrical system powering the drive system.

Preferably, the relay station includes a gas inflatable device with an associated gas discharge system.

Preferably, the gas inflatable device is a balloon.

Preferably, the balloon comprises a parachute with descent control lines and an altitude control system.

Preferably, the altitude control system is a balloon gas temperature controller.

Preferably, at least part of the envelope on the balloon is an electrochromic or photochromatic material.

Preferably, the system comprises at least three relay stations, at least one of them being composed of sections, at least one of which has a receiving / transmitting device for telecommunications signals from and to the earth stations and / or the remaining relay stations, and at least one of the remaining sections have a device supplying the receiving / transmitting devices and / or devices controlling the horizontal and vertical displacement of the relay stations.

Preferably, at least two sections have receiver / transmitting devices for telecommunications signals from and to the earth stations and / or other relay stations.

Preferably, at least two sections have devices for feeding the receiving / transmitting devices and / or devices for controlling the horizontal and vertical displacement of the relay station.

The subject matter of the invention in an exemplary embodiment is reproduced in the drawing, in which Fig. 1 shows a schematic diagram of a suborbital wireless communication system; Fig. 2 shows an elevation view of the relay station; Fig. 3 shows the drive system of the relay station of Fig. 2; Fig. 4 shows an alternative embodiment of the drive system of the relay station of Fig. 2; Fig. 5A is a top view of a relay station including three sections; fig. 5B - relay station with three sections, in side view; Figures 6A, 6B and 6C illustrate relays on airplanes; Figures 7A and 7B illustrate an alternative embodiment of a sub-orbital wireless communication system; Fig. 8 is a detail of the transfer station of Fig. 1 with a balloon deflation system; Fig. 9 shows the second embodiment of the deflation system of Fig. 8 and Fig. 10 shows the relay station being brought to the ground.

As shown in Fig. 1, sub-orbital wireless communication system 10 consists of a ground portion 12 and an overground portion 14.

Ground portion 12 may include conventional tap-off networks 16 connected to ground station 18, provided with suitable long range transceiver such as antenna 20. Ground portion 12 may also include mobile telephones such as well known cell phones that can be human-borne^:22 or mounted on vehicles 24. Antennas 20 are used to transmit and receive telecommunications signals to and from a high-suspension sub orbital relay station 28 located 19 to 56 km above the ground.

Ideally, there should be more than 28 such relay stations, each of them located in a fixed location above ground. Such relay stations 28 are intended to remain in the air for at least 20 to 30 days.

Each relay station 28 includes an apparatus for receiving telecommunications signals from the antenna 20 of the ground station 18, from the human 22 cell phone or vehicle 24, and then forwards them to the antenna 118 of another earth station 120, another human cell phone 122, or another vehicle 124. this is going to happen

180 378 directly or via another relay station 130. As the telecommunications signals return to the ground portion 12 of the suborbital wireless communications system 10, communications continue in a conventional manner.

The relay station 28 is equipped with a lifting device. Although ordinary zero-pressure balloons are used for flying at high altitudes, they are not suitable for use in equipment that has to operate for more than a week or about ten days. This is because the gas in zero pressure balloons cools down at night and increases its density. As a result, it descends until it reaches a density height that corresponds to its own density. Therefore, to stay up, the zero-pressure balloon must lose about 8 to 9% of its weight each night to compensate for the increase in its density. Otherwise it will fall to the ground.

On the other hand, a suitable lifting device may be a gas-blown device that is lighter than air, such as e.g. a high-pressure balloon 32. The pressure-relief balloon 32 has the property of being able to float at a predetermined density height. This is achieved by balancing the inflation pressure of the balloon and the weight of the equipment mounted thereon against the expected pressure and temperature of the surrounding air at the desired density altitude. It has been observed that devices of this type maintain high vertical stability throughout the day, despite the fact that they are exposed to huge temperature fluctuations.

The lifting device may also be an enhanced zero pressure balloon provided with means to control the heating of the gas contained in the balloon during the night and its cooling during the day. In this way, controlling the gas temperature reduces the amount of ballast that would have to be thrown out each night.

An alternative solution for the lifting device is a positive pressure zero-pressure balloon. It is an ordinary zero-pressure balloon equipped with closing valves. This allows the pressure to be maintained to the specified limits in flight by the controlled release of gas through the valve. This reduces the amount of ballast that has to be thrown out as the gas cools down during the night because a conventional zero pressure balloon increases in density and loses height.

Although a positive pressure zero-pressure balloon also undergoes diurnal variations in height, it requires significantly less ballast and gas bleeds than a heat-regulated zero-pressure balloon. Therefore, both the flight time of an overpressure zero-pressure balloon and the equipment load can be significantly higher than that of a zero-pressure balloon. However, the contraction and expansion of the gas contained within the balloon in a diurnal cycle, accompanied by altitude changes, puts enormous stress on the balloon. Therefore, the weight of the equipment carried by the balloon is reduced.

There is therefore a need to control the height of the balloon and the expansion and contraction of the gas contained within the balloon in order to reduce stresses. This is accomplished by using means to control the amount of gas inside the balloon that is heated during the day and cooled during the night. In this way, the degree of stress on the balloon is controlled, and the load it can bear over relatively long periods of time ranges from three to four tons.

The amount of heat inside the balloon is controlled by applying a suitable transparent, electrochromic or photochromic material to the envelope of the balloon or part of the envelope. Thus, the envelope of the balloon is substantially transparent in low light and at night. This allows radiant heat energy to enter the balloon and heat its interior in a manner similar to a greenhouse. During the daytime, sunlight or a signal from the ground causes the balloon coating to become reflective or opaque. This lowers the amount of radiant energy penetrating the balloon and thus keeping the balloon interior relatively cool.

At the ground portion 12 of the sub-orbital wireless communications system 10, there are a plurality of tracking stations 36. These are equipped with well-known identification devices.

180 378 and detecting the position and height of the individual relay stations 28, whether they are in a group or not.

The tracking system is there to bring the relay station 28 to its assigned position in case the tracking station 36 detects that the position has moved. In order to keep the relay stations 28 in a fixed position, the tracking system is automatically controlled using a fuzzy logic control system.

As shown in Figure 2, each relay station 28 includes one unit block 38. In the preferred embodiment of the invention, the unit block 38 has a deck. However, such device block 38 may be of any convenient shape and size such as to be sufficient to lift devices necessary to fulfill the tasks of the relay station 28.

The device block 38 shown in Figs. 2 and 3 includes a housing 40 that can be lifted by the balloon 32. The housing 40 includes a telecommunications signal transmitter and receiver 44 and an antenna 48 for communicating with the ground. The antenna 48 serves to receive and transmit telecommunications signals between the antennas 20 of the earth stations 18 and the relay station 28. The relay station 28 also has an array of antennas 52 adapted to receive and transmit telecommunications signals to and from other relay stations 130. Housing 40 also includes a guidance module 56 that transmits identification and position signals to tracking stations 36. It receives commands from the tracking station 36 to trigger the drive system. The homing antenna 58 is for communication between the tracking station 36 and the homing module 56.

Mounted on the housing 40 is a reactivable power supply 60 which contains a set of solar batteries 64. Solar batteries 64 capture the sun's rays in a known manner and convert them into electrical energy which is used to power the telecommunications device and to guide and drive the relay station 28.

In addition, the power supply 60 may include a set of weather vane 68. These may be oriented in different directions such that at least some of them always face the prevailing winds. Wind deflectors 68 generate electricity in a known manner, which energy can also be used to power telecommunications equipment, to guide and drive the relay station 28.

The device block 8 of the relay station 28 shown in Fig. 4 has another power source 66 which is part of the microwave power system. The system includes a ground-based microwave generator (not shown) that produces a beam of microwave energy at a frequency of approximately 35 GHz. This beam is directed to the receptors 80 on the relay station 28 and is here converted into direct current. Microwave energy can also be supplied from an orbital source or from free space.

In a manner similar to a solar power system, a microwave power system can power the telecommunication devices located at the relay station 28 as well as provide power to guide and drive it.

Additionally, the relay station 28 may be equipped with at least one microwave transmitter and corresponding devices for directing the microwave transmitter to the microwave receiving device of another relay station 130, such that the other terrestrial microwave generator is able to deliver microwave energy to the relay station 130.

As shown in Figures 3 and 4, the drive system of the relay station 28 may include a set of rocket motors 108 or thrusters 90, or propellers 94. The thrusters 90 and the propellers 94 are oriented in a horizontal plane along mutually perpendicular axes and are supported in an overhead nacelle 100. on the housing 40. By selectively triggering various jet engines 90 or propellers 94, relay station 28 is guided to a predetermined position above the ground and held there.

Additional thrusters 90 or rocket engines 108 or propellers 112 may be placed on the vertical axes as needed to assist with the introduction

180 378 of the relay station 28 to a predetermined height when firing it or guiding it in case it drifts from the predetermined height further than permitted.

Drift of the relays 28 from their predetermined positions is detected by ground tracking stations 36. The tracking stations 36 then trigger the drive members at the relay stations 28 at selected intervals to bring them back to the predetermined position.

In an alternate embodiment, illustrated in Figures 5A and 5B, each relay station 28 may include two to four sections 34. Each section 34 is provided with a device block 38 which is independently lifted by its own lifting device, i.e., balloon 32.

Some device blocks 38 support the telecommunications equipment, while other device blocks 38 contain devices for generating and transmitting power energy. In this way, energy is transmitted from the power generating modules by radiating microwave energy to the antennas of the telecommunications modules. Since there are several sections 34 making up the relay station 28, each of these sections 34 can be smaller and lighter than if only one block of devices 38 were included in the relay station 28. Moreover, the provision of a set of sections 34 creates redundancy that allows keeping the relay station 28 operational if the devices of one of the sections 34 fail.

Another solution, illustrated in Figures 6A, 6B, and 6C, is to use light unmanned aerial vehicles 114 in place of the balloons 32. The aircraft 114 may be steered from the ground using well known techniques. However, they are less useful here than the balloons 32. This is because they have to constantly change position in order to stay up, and because the load that can be mounted on them is limited by the low weight required to reach great heights. airplane 114.

The energy needed to keep the aircraft 114 up for longer periods is obtained from solar energy (Fig. 6A). In this case, the airplane 114 is in fact a flying wing composed of high efficiency solar cell plates 116. The solar cells 116 in the wing can drive electric motors and an energy storage system.

Additionally, regenerative hydrogen-oxygen fuel cells 118 (Fig. 6B) can be used to achieve longer flying times.

In addition, light airplane 114 may be powered by microwave energy radiated to antenna 126 of airplane 114 from transmitting cup reflector 128 on the ground or collected from microwave energy in space (FIG. 6C).

During operation of the sub-orbital wireless communication system 10, the receiver does not feel its existence. Thus, when a telephone call occurs, telecommunications signals will be forwarded from the calling telephone, via the conventional telephone network 16, to the earth station 18 associated with its location. The antenna 20 of this station will radiate a telecommunication signal corresponding to this telephone call to the nearest relay station 28. A switching circuit of known type will route the signal to another earth station 120 located in the vicinity of the receiver. If the receiver is away, the signal will be transmitted to a distal relay station 130 from which it will be routed to another human's portable cell phone 122 or other vehicle 124, or to yet another earth station 140 located in the vicinity of the receiver. The signal received by the other earth stations 120 or 140 will be transmitted to the recipient's telephone via¹ conventional telephone network. After such setting up of the telecommunications link between the two telephones by means of the land and relay stations, the parties can communicate.

As the relay stations are located at an altitude of approximately 19 to 56 km, they are beyond the reach of inclement weather. However, at this altitude, the power requirements of the telecommunications signals are quite low to allow the use of the same frequencies as those used for terrestrial transmission. This means that existing allocated telecommunications frequencies can be used. Due to this,

180 378 that quite a lot of technical devices have already been developed for these frequencies, the costs of introducing this new system are not high. Moreover, the maximum use of the existing frequencies can be achieved by using known digital multiple access techniques such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), code multiple access CDMA (Code Division Multiple Access). ), or a combination of these techniques.

Therefore, compared to telecommunications signals from satellites, the signals generated in the telecommunications system according to the invention are relatively weak, as they travel a shorter distance. This is particularly advantageous because the possibility of using a weaker signal makes both the transmitters and the receivers smaller, lighter, and requiring less power.

This aspect of the telecommunications system is even more evident when the relay stations 28 over densely populated areas 132 operate at lower altitudes and / or with more narrowly focused reception and propagation angles 142, compared to other relay stations 28 working in less populated areas 134. at higher altitudes and / or having more focused reception and propagation angles 144 (Figs. 7A and 7B). By doing so, the imbalance in the dynamics of the traffic served by the various relays 28 of system 10 is substantially reduced. Moreover, as previously explained, the relays 28 intended for the more densely populated areas 132 may operate at a lower power level. This can reduce operating costs. This is an additional advantage over a satellite system, because in such a system, reducing the orbit height of a satellite will increase its loss rate and shorten its lifetime.

Each relay station 28 is equipped with a restorative system 150 (Figures 2, 8, 9, and 10). This system consists of a deflation device 152 and a remotely operated return parachute 154.

In the embodiment illustrated in Figures 2 and 8, the deflation device 152 includes a housing 160 formed integrally with a corresponding lighter-than-air device, e.g., a balloon 32. The housing 160 has an outwardly projecting and radially directed flange 164 integrally connected to the balloon 32 or with glue or by welding. The collar 164 supports the downwardly facing generally cylindrical wall 168 that supports the bottom wall 172. The bottom wall 172 (FIG. 8) is delimited by a mesh with holes such that the housing 160 is connected to the inside of the balloon 32 and is at the same pressure.

Near its upper edge, the cylindrical wall 168 supports an inwardly facing flange 176. Fragile cover 184 is connected to flange 176 in an airtight manner. This is achieved by gluing the cover 184 to the flange 176 or by using a suitable gasket, or by making the cover 184 integral with the housing portion 160.

The cylindrical wall 168, the bottom wall 172, and the lid 184 define the parachute chamber 154.

A small chamber 190, formed under the fragile cover 184 by the wall 192, houses a small explosive 194 that is fired in response to a signal received by antenna 196.

Parachute 154 has control cables 198 connected to a radio controlled propulsion unit 200 which is provided in housing 160. Propulsion 200 is equipped with electric motors driven in response to ground signals to alter the lengths of the control cables 198 and thereby provide directional control. parachute 154.

To bring the relay station 28 to the ground, a code signal is sent, which is received by the antenna 196. As a result, the explosive 194 detonates and the brittle cover 184 is removed.

Since cover 184 is designed to be easily broken, the applied explosive 194 may be relatively light so as not to damage the parachute 154.

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Wall 192 helps to direct the blast force towards the top of cover 184, rather away from balloon 32.

After the cover 184 is removed, gases begin to escape from inside the balloon 32 through the bottom wall 172 and an opening in the top of the housing. The force of the air escaping from the balloon 32 as soon as the cover 184 is removed is sufficient for the deployment of the parachute 154.

As shown in Fig. 10, parachute 154 will support balloon 32 with its control lines 198. Relay station 28 is directed to a predetermined location on the ground.

In the embodiment shown in Figure 9, the collar 164 supports the lid 204 with an annular airtight seal therebetween. The lid 204 is connected to the flange 164 by a set of clamping supports 210 spaced around the circumference. The clamp brackets 210 are held releasably in mesh with the cover 204 by electric motors 212. The electric motors 212 are energized on a signal from the ground and retract the clamp brackets 210.

When the clamp brackets 21.0. are drawn off, the pressure of the gases exiting from the balloon 32 will displace the cover 204 which will allow the parachute 154 to expand.

After the relay station 28 is repaired, the restoration system 150 is replaced and the balloon 32 is re-inflated and repositioned.

If the relay stations include remotely operated airplanes 114, they can be brought for repair in a known manner and returned to the appropriate site after repair.

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HG. 3

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FIG. 4

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HG. 5A

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FIG. 5B

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FIG. 7B

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FIG. 9

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FIG. 10

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