Abstract:
A computer-implemented method for releasing and controlling an airship is provided. The method includes receiving instruction signals to release the airship for an autonomous flight, wherein the airship includes a plurality of body segments and a plurality of coupling elements for coupling adjacent body segments along a length of the airship. The method further includes determining environmental conditions affecting the airship, evaluating an internal pressure level of each of the plurality of body segments and a stiffness level of each of the couplings elements, and determining whether the evaluated internal pressure levels and stiffness levels are substantially suitable to the determined environmental conditions. The method further includes, determining whether the propulsion unit is in an operational state, and then based on the determination that the propulsion unit is in an operational state, triggering a disconnection of the tether unit and an activation of the auto pilot unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/644,183, filed May 8, 2012, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    A typical airship such as a blimp has a rigid outer envelope filled with a lifting gas such as helium. An airbag or ballonet disposed inside the envelope is used to provide vertical control of the airship and to provide ballast when the airship is aloft. In particular, air is evacuated from the ballonet to outside the airship to cause the airship to ascend and air is pumped into the ballonet to cause the airship to descend. Such an airship may include more than one ballonet to provide ballast and to control the nose-to-tail orientation of the airship. 
         [0003]    Due to their rigid outer structures, typical airships may not be maneuverable in weather conditions involving high winds and/or turbulent air. Moreover, high-speed crosswinds may damage the rigid airship. As such, these airships are generally operated on calm days or when high-speed winds are not expected. 
         [0004]    Aerostats also have an outer envelope filled with a lifting gas. However, unlike blimps, aerostats are secured to an object/body on the ground by a tether. One end of the tether is attached to the aerostat and another end of the tether is attached to the object that is securely stationed on the ground. The tether holds the aerostat in place over a particular area. As known to one of ordinary skill in the art, an aerostat is not equipped with a propulsion device and a flight controller and, therefore cannot self-navigate to a destination when disconnected from the tether. 
       SUMMARY 
       [0005]    Disclosed herein are a self-powered releasable aerostat, method and system for releasing and controlling the aerostat. 
         [0006]    According to one aspect, a computer-implemented method for releasing and controlling an airship is provided. The method includes receiving instruction signals to release the airship for an autonomous flight, wherein the airship includes a plurality of body segments and a plurality of coupling elements for coupling adjacent body segments along a length of the airship, wherein the airship is detachably coupled to a ground unit through a tether unit, and wherein the airship includes a propulsion unit, an auto pilot unit, and a controlling unit for controlling the propulsion unit, the tether unit, and the auto pilot unit. The method further includes determining environmental conditions affecting the airship, evaluating an internal pressure level of each of the plurality of body segments and a stiffness level of each of the couplings elements, and determining whether the evaluated internal pressure levels and stiffness levels are substantially suitable to the determined environmental conditions. Based on a determination that the evaluated internal pressure levels and stiffness levels are substantially suitable to the determined environmental conditions, the method further includes, determining whether the propulsion unit is in an operational state, and then based on the determination that the propulsion unit is in an operational state, triggering a disconnection of the tether unit and an activation of the auto pilot unit. 
         [0007]    According to another aspect, an airship includes a plurality of body segments Tillable with lighter than air gases, a plurality of coupling elements, each of which is positioned to couple adjacent body segments along a length of the airship, a releasable tether unit for securing the airship to a ground unit while the airship is aloft, a propulsion unit for facilitating an autonomous flight of the airship, a controlling unit for triggering a release of the tether unit, for actuating the propulsion unit, and for controlling internal pressure levels of the body segments and stiffness levels of the coupling elements. 
         [0008]    According to another aspect, a non-transitory computer-readable medium comprising instructions executing the method for releasing and controlling an airship. 
         [0009]    These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it should be understood that the disclosure provided in this summary section and elsewhere in this document is intended to discuss the embodiments by way of example only and not by way of limitation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the accompanying figures, like reference numerals refer to identical or functionally similar elements throughout the separate views. 
           [0011]      FIG. 1  illustrates an elevated longitudinal side view of an exemplary embodiment of an aerostat, having multiple segments, connected to vehicle via a tether; 
           [0012]      FIG. 2  illustrates an elevated longitudinal side view of the aerostat of  FIG. 1  with a non-aligned arrangement of the multiple aerostat segments; 
           [0013]      FIG. 3  is a cross-sectional view, along a line A-A, of an exemplary embodiment of the tether of the aerostat of  FIG. 1 ; 
           [0014]      FIG. 4A  is a schematic diagram of an exemplary embodiment of a communication system of the aerostat of  FIG. 1 ; 
           [0015]      FIG. 4B  is a block diagram of an exemplary embodiment of a control system of the aerostat of  FIG. 1 ; 
           [0016]      FIG. 5A  illustrates an elevated longitudinal side view of an exemplary embodiment of an aerostat having multiple tethers; 
           [0017]      FIG. 5B  illustrates an elevated longitudinal side view of another exemplary embodiment of an aerostat having multiple tethers connected to a single tether that is connected to a vehicle or an immobile station; 
           [0018]      FIG. 6  illustrates an elevated longitudinal side view of another exemplary embodiment of a single-segment aerostat having a tail; 
           [0019]      FIG. 7  is a flow chart illustrating a method for releasing and controlling an a flight of the aerostat of  FIG. 1 ; 
           [0020]      FIG. 8  is a block diagram illustrating components of the aerostat controller; and 
           [0021]      FIG. 9  is a schematic drawing illustrating a computing network system according to an exemplary embodiment. 
       
    
    
       [0022]    Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements. Further, the apparatus, method and system components have been represented, where appropriate, by conventional symbols in the drawings. 
       DETAILED DESCRIPTION 
       [0023]    In the following detailed description, reference is made to the accompanying figures, which form a part hereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, figures, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
       Overview 
       [0024]    As known to one of ordinary skill in the art, an airship, such as an aerostat or a blimp, has an envelope of flexible sheet material that is filled with a lighter than air (LTA) gas, such as helium. The envelope has an aerodynamic configuration, such as a teardrop shape, or a round configuration. However, the overall shape of the airship is set and may not be modified expect very slightly during the filling or removal of the LTA gas. Moreover, as stated above, due to the rigid outer structure, the airship may not be maneuverable in weather conditions involving high winds and/or turbulent air. 
         [0025]    Accordingly, in one exemplary embodiment, an aerostat is configured as a segmented airship. Now referring to  FIG. 1 , an aerostat  50  includes a head segment  102 , one or more body segments  104 , and a tail segment  106 . At a coupling  113  between any two adjacent segments is a segment closer strap  114  operated by a segment closer module  116  associated therewith. In addition, each segment  102 ,  104 , and  106  includes a sensor module  118 , a segment fill-fan-and-valve assembly  120 , and a pressure sensor  122 . Sensor module  118  includes one or more instrument sensors such as a magnetic compass, an inertial navigation sensor, and a three-axis position sensor. A segment controller  124  is also disposed in each segment  102 ,  104 , and  106 , and is configured to receive measurement signals from sensor module  118  and pressure sensor  122  disposed in such segment  102 ,  104 , or  106 , and to serialize and transmit such measurement signals to an aerostat controller  126 . Further, segment controller  124  is configured to receive from aerostat controller  126  signals for adjusting a stiffness of couplings  113  between adjacent segments  102 ,  104 , and  106 , and to increase or decrease the pressure inside segments  102 ,  104 , and  106 . In response to the received signals, segment controller  124  is configured to operate corresponding segment closer strap  114  at an associated coupling  113  to increase or decrease the stiffness thereof. Similarly, segment controller  124  is configured to operate fill-fan-and-valve assembly  120  associated with segment  102 , 104 , or  106  to increase or decrease the pressure within such segment  102 ,  104 , or  106 . The stiffness of coupling  113  and the pressure inside segments  102 ,  104 , and  106  can be adjusted appropriately to allow aerostat  50  to assume a substantially/suitably rigid structure having a profile shown in  FIG. 1 . Such profile and rigid structure may enable aerostat  50  to hover over a relatively fixed area in low wind conditions. In one embodiment, aerostat  50  includes a motor driven propulsion module  130  that may be controlled by aerostat controller  126  to propel aerostat  50 . 
         [0026]    As shown in  FIG. 1 , aerostat  50  is connected to a ground unit  52 , which can be a vehicle or fixed station, through a tether  54 . One end  56  of tether  54 , which can be a quick connect fitting end, is configured to be releasably coupled to an attachment point  58  located on aerostat  50 . Another end  60  of tether  54  is releasably coupled to an attachment point  62  of ground unit  52 . Moreover, such releasable ends  56  and  60  can mate with suitable receptacles (not shown) at attachment points  58  and  62  of aerostat  50  and ground unit  52 , respectively. 
         [0027]    Now referring to  FIG. 2 , a width of each closer strap  114  and the internal pressure of each segment  102 ,  104 , or  106  may be adjusted to allow aerostat  50  to become flexible or stiff. In case closer straps  114  are configured to have a cylindrical shape, then their respective diameters may reach their widest values during the stiffening process. By constricting one of segment closer straps  114  at the corresponding coupling  113 , thereby reducing the stiffness at such coupling  113 , may allow a portion of aerostat  50  that includes such coupling  113  to become flexible. That is, segments  102 ,  104 , and  106  of aerostat  50  can be moved with respect with one another. Moreover, it should be apparent that the diameters/widths of closer straps  114  between adjacent segments  102  and  104   a,    104   a  and  104   b,  and  104   b  and  106  may not be identical and therefore stiffness at couplings  113  between such adjacent segments may vary. In high wind and/or turbulent air environments, such flexibility can allow each segment  102 ,  104 , or  106  of aerostat  50  to drift into a position that reduces a gradient of the wind with respect to such segment (that is, such segment presents a minimized cross-section to the wind). With this segment-closer strap arrangement, aerostat  50  can remain airborne even in high wind and/or turbulent air conditions without being at risk of being damaged by crosswinds. Moreover, 
         [0028]    As known to one of ordinary skills in the art, one technique for providing power to electrical devices/systems aboard aerostat  50  is to carry an electrical generator on board. This arrangement is configured to provide all the necessary power needs of aerostat  50  in a somewhat efficient manner. Unfortunately, electrical generation equipment is quite heavy and decreases a potential load equipment that may be carried by aerostat  50 . Another drawback of employing an on-board power generator is the reduced “availability” of aerostat  50 . In other words, the generator typically only has enough fuel to electric components of aerostat  50  for a few days. At the end of which, aerostat  50  must be retrieved, serviced, and then re-deployed. In order to increase the availability of aerostat  50 , a ground-based power supply system located in ground unit  52  is configured to provide power to aerostat  50  through tether  54 . As such, any problem with the ground-based power supply system can be easily dealt with on the ground instead of having to retrieve aerostat  50  anytime the onboard electrical generator has a malfunction. Moreover, ground-based power supply system is used to supply power to aerostat  50  so that power sources, such as power storage units, on board aerostat  50  may be conserved while aerostat  50  is connected to ground unit  52 . Based upon the foregoing, there is a need for a lighter tether that allows for an increase in any desirable load carried by aerostat  50 . Moreover, there is need for a tether which provides more power to aerostat  50 , provides redundancy and improved power delivery, and is configured to minimize an electromagnetic interference emanating therefrom. 
         [0029]    Now Referring to  FIG. 3 , one embodiment of tether  54  includes a power line  202  and a communications line  204 . A protective outer layer  206  surrounds power line  202  and communication line  204 . Protective outer layer  206  may be manufactured using an environmentally durable material, such as Kevlar® material that is manufactured by E.I. du Pont de Nemours and Company for example. In another embodiment, communication line  204  includes a fiber-optic line (optical fiber) as is known in the art. Power line  202  includes a conductive wire such as copper or other conductive material. Power line  202  and communication line  204  are configured to terminate in end  56  of tether  54 . Moreover, attachment point  58  can include a solenoid driven release (not shown) that when actuated by aerostat controller  126  enable a detachment of the quick connect fitting ends from their corresponding receptacles. 
         [0030]    Moreover, attachment points  58  and  60  may include attachment mechanisms that may be swiveling fixtures, such as ball joints. Alternatively, each of the attachment mechanisms may be a u-joint, gimbal, or other mechanism. Furthermore, aerostat  50  may utilize multiple attachment mechanisms for tether  54  having a plurality of coupling features. Further, each of the attachment mechanisms may include a decoupling mechanism, such as is a guillotine-type mechanism that severs tether  54  as needed. In addition to the solenoid-initiated quick release device, the decoupling mechanism may be realized as any of the following, without limitation: a pyrotechnic device, or a wide variety of other detachment mechanisms. 
         [0031]    Referring back to  FIGS. 2 and 3 , ground unit  52  supply aerostat  50  with power via power line  202  so that power sources, such as power storage units, on board aerostat  50  may be conserved while aerostat  50  is connected to ground unit  52 . Ground unit  52  may include a generator, a solar panel assembly, batteries, or other power sources from which to supply power to aerostat  50 . Alternatively, tether  54  may be configured to incorporate a waveguide for Megawatt-level transmission of millimeter wave power. 
         [0032]    As shown in  FIG. 2 , a ground unit controller  208  associated with ground unit  52  may use communication line  204  to transmit data to or receive data from aerostat controller  126 , an autopilot unit (described below) of the aerostat  50 , a controller of a payload  210  carried by aerostat  50 , and/or additional component carried by aerostat  50 . For example, ground unit controller  208  may transmit instructions to aerostat controller  126  regarding the altitude or attitude at which to maintain aerostat  50 . In one embodiment, ground unit controller  208  may transmit instructions to the autopilot regarding a destination to which the aerostat  50  should fly if or when the aerostat  50  is disconnected from the ground unit  52 . Ground unit controller  208  is configured to transmit instructions to the controller of payload  210  regarding data payload  210  may gather and/or actions payload  210  may undertake. 
         [0033]    In one embodiment, ground unit controller  208  is configured to receive via communication line  204  data regarding the attitude and/or or altitude of aerostat  50  or of the operating status of the various components or systems of aerostat  50 . Ground unit controller  208  may also receive via communication line  204  data collected by payload  210  or information regarding the operating status of the components associated with payload  210 . 
         [0034]    As shown in  FIG. 4A , in one embodiment, ground unit controller  208  may communicate with the components on the aerostat  50  (including aerostat controller  126 , payload  210 , or the autopilot) using radio or other wireless communication means apparent to those of skill in the art. Moreover, ground unit controller  208  may communicate with the components on aerostat  50 , using both wireless communication and the communication line  204 . Alternatively, as shown in  FIG. 4A , a power cable  403  that includes a power line (not shown) may not be integral to tether  54 , and the wireless communication may be performed using an Omni directional antenna  405  connected to aerostat  50 . 
         [0035]    Referring back to  FIG. 2 , a remote controller  212 , which may be located remotely from the ground unit  52 , may also communicate with components on board aerostat  50 . In one embodiment, remote controller  212  may utilize radio or other wireless communication means apparent to those of skill in the art to transmit data to ground controller unit  208 . Ground controller unit  208  thereafter transmits such data to the components on the aerostat  50  as described above. Similarly, ground controller  208  may receive data from the aerostat  50  as described above and forward such data to remote controller  212 . In another embodiment, remote controller  212  may communicate with the components of aerostat  50  directly. 
         [0036]    In one embodiment, aerostat  50  can operate in an unmanned manner under control of controller  126 . Moreover, ground unit  52  may also be unmanned after aerostat  50  has been launched. In another embodiment, the operation of aerostat  52  can be directed from remote controller  212 . 
         [0037]    In accordance with an exemplary embodiment, when aerostat  50  is secured to the ground by tether  54 , the motors of propulsion module  130  are idle. In response to instruction signals from ground unit controller  208  or remote controller  212 , aerostat controller  126  actuates such motors, confirms that propulsion module  130  is operational, disconnects tether  54 , and navigates aerostat  50  to a predetermined location. In another embodiment, ground unit controller  208  or remote controller  212  may send instruction signals to direct aerostat controller  126  to activate the motors of propulsion module  130  and release aerostat  50  at a predetermined or particular time, or after a specified period of time elapses. Such instruction signals may direct aerostat controller  126  to release aerostat  50  when the weather is sufficiently favorable for flight. Further, remote controller  212  may be configured to remotely control the operation of aerostat  50 , including propulsion maneuvers, flight maneuvers, and landing maneuvers. 
         [0038]    To release tether  54 , aerostat controller  126  directs a tether controller (described below) to actuate a release mechanism that disengages tether  54  from the first attachment point  58 . Alternatively, to release tether  54 , aerostat controller  126  directs the tether controller to actuate a release mechanism that disengages tether  54  from the second attachment point  60 , and to trigger a retrieving mechanism that brings up tether  54  towards aerostat  50  for storage during the autonomous flight. This alternate arrangement of tether  54  facilitates the attachment of aerostat  50  to another ground unit that may not be equipped with a tether. 
         [0039]    In one embodiment, before aerostat  50  is released from tether  54 , ground unit controller  208  or remote controller  212  may send an instruction signal to the autopilot of aerostat  50  that includes a destination to which aerostat  50  should fly after its release. Ground unit controller  208  or remote controller  212  may send another instruction signal to aerostat controller  126  to undertake a controlled descent of aerostat  50 . Such instruction signal may direct aerostat controller  126  to undertake the controlled descent of aerostat  50  immediately, at a particular time, or after a specified period of time elapses. Such instruction signals may direct aerostat controller  126  to controllably descend aerostat  50  when the weather is sufficiently favorable for such operation. In response to such instruction signals, aerostat controller  126  may direct segment controllers  124  of each segment  102 ,  104 , and  106  to operate segment fill-fan-and-valve assembly  120  to deflate such segments. Aerostat controller  126  may also direct controllers  124  to operate segment closer modules  116  to control the stiffness of couplings  113  associated therewith to facilitate control of the descent of aerostat  50 . 
         [0040]    As such, one would recognize that the controlled descent of aerostat  50  may occur while aerostat  50  is attached to tether  54  or after aerostat  50  is released from tether  54 . For example, ground unit controller  208  or remote controller  212  may direct aerostat controller  126  to actuate the motor of propulsion module  130 , disengage aerostat  50  from tether  54  or disconnect tether  54  from ground unit  52 , use propulsion module  130  to navigate to a predetermined location transmitted to the autopilot of aerostat  50 , and controllably descend aerostat  50  or release tether  54  upon reaching such location. 
         [0041]    In order to improve on the aerostat autonomous flying, aerostat controller  126  may be coupled to following sensors are used: a Global Positioning System (GPS) receiver (not shown), a digital compass (not shown) that provides the airship heading (yaw), pitch and roll angles, two piezoelectric vibrating gyros (not shown) that provide the pitch and yaw rates. Besides, an altimeter and a speedometer, both based on silicon piezo-resistive pressure sensors, may be used for helpful environment information. 
         [0042]    In one exemplary embodiment, aerostat controller  126  is configured to detect whether the tether  54  is severed, unexpectedly disconnected, or otherwise compromised. In another embodiment, aerostat controller  126  is configured to monitor the power supplied through power line  202  and to determine that the tether  54  has been compromised if such power is interrupted. In still another embodiment, ground controller  208  or remote controller  212  may transmit a particular signal, such as a heartbeat signal, at predetermined intervals and aerostat controller  126  may determine that tether  54  has been compromised if such heartbeat signal is not received when expected. Other characteristics of tether  54  that may be monitored by aerostat controller  126  to determine continuity of tether  54  will be apparent/obvious to one of ordinary skills in the art. 
         [0043]    Upon determining that tether  54  has been compromised, aerostat controller  126  may undertake instructions previously transmitted thereto and/or stored in a memory thereof. In one embodiment, such instructions may direct aerostat controller  126  to cause aerostat  50  to navigate to a predetermined location, and optionally, descend upon reaching such location. In another embodiment, such previously transmitted and/or stored instructions may direct aerostat controller  126  to immediately begin a controlled descent of aerostat  50  once tether  54  is compromised. 
         [0044]    Moreover, if tether  54  is compromised, the previously transmitted or stored instructions may cause aerostat controller  126  to direct segment controllers  124  to dump the lifting gas from one or more of the segments  102 ,  104 , and  106  of aerostat  50  to facilitate a rapid descent of aerostat  50 . Other actions that may be undertaken in response to a determination that tether  54  has been compromised will be apparent/obvious to one of ordinary skills in the art. 
         [0045]    The actions described above that may be undertaken when aerostat controller  126  determines that tether  54  has been compromised may also be undertaken in other emergency situations. Further, such actions may be undertaken upon a command transmitted by ground control unit  208  and/or remote controller  212 . 
         [0046]    Referring to  FIG. 4B , a control system  400  of the aerostat  50  includes aerostat controller  126  described above coupled to altitude and attitude/condition sensors  401 . Altitude and attitude sensors  401  may include a pitot tube  401   a  and a GPS module  401   b.  Aerostat controller  126  is also coupled to each segment controller  416  associated with a segment  102 ,  104 , or  106 , a coupling controller  418  associated with each coupling  13 , an autopilot unit  402 , and a propulsion module  408 . In one embodiment, aerostat controller  126  is configured to monitor the readings from the altitude and attitude sensors  401  to manage the in-flight vector parameters, air speed, and to control the altitude and attitude of aerostat  50 . Moreover, aerostat controller  126  is configured to communicate with autopilot unit  402 , ground unit controller  208 , and/or the remote controller  212  in order to keep aerostat  50  in a substantially stationary position or to correctly travel to a predetermined location at a predetermined altitude. 
         [0047]    Aerostat controller  126  is configured to control a propulsion module  408  to move the head segment  102  in a particular direction and control the attitude of head segment  102 . Aerostat controller  126  also monitors and adjusts the inflation pressure, the heading, and the attitude of each of the segments  102 ,  104 , and  106  to ensure that remaining segments  104  and  106  of aerostat  50  follow head segment  102  while minimizing the forces of the wind on the segments of aerostat  50 . As such, on board propulsion module  408  and controller  126  enable aerostat  50  to handle changes in ambient wind, and hence can relocate and fly around. 
         [0048]    Control system  400  further includes a power module  410  to provide electrical power to the components thereof. Power module  410  may provide power supplied via power line  202  in tether  54 , if available, or from a power source onboard aerostat  50 . The onboard power source may be any suitable source of electrical energy including a battery, solar cell, wind generator, or a combination thereof. Alternatively, the onboard power source may be a self-harvesting power unit that draws its electrical energy from mechanical energy generated by aerostat movements, such as on vibrations and oscillations. 
         [0049]    Control system  400  further includes a communication module  411  coupled to the airship controller  126  that includes a transceiver to facilitate wired or wireless communications between aerostat controller  126  and ground unit controller  208  and/or the remote controller  212 . 
         [0000]    In one embodiment, aerostat controller  126  is coupled to a tether controller  412 , which is configured to monitor the continuity of tether  54  and to provide signals to aerostat controller  126  that indicate whether tether  54  has been compromised. Further, tether controller  412  is configured to control the solenoid driven release to disengage aerostat  50  from tether  54 . 
         [0050]    In the above described embodiments, tether  54  is the only element attaching/securing aerostat  50  to ground unit  52 . In another embodiment, multiple tethers may be used. Now referring to  FIG. 5A , for example, a first tether  500  may secure head segment  102  to ground unit  52   a,  and a second tether  502  may secure tail segment  106  to ground unit  52   b.  Further, additional tethers may be used to secure middle body segments  104   a  and  104   b  to ground units  52   a  and  52   b.  As such, tethers  500 ,  502 , and  504   a  and  504   b  do not have to be simultaneously attached to the same ground unit. As shown in  FIG. 5A , tethers  500  and  504   a  are attached to ground unit  52   a  and tethers  502  and  504   b  are attached to ground unit  52   b.  Tethers  500 ,  502 ,  504   a,  and  504   b  may be each connected to aerostat  50  using quick connect fittings that may be released electronically by aerostat controller  126  as described above. Further, the power and/or communication lines may be incorporated in all or some such tethers  500 ,  502 ,  504   a,  and  504   b.  Some of tethers  500 ,  502 ,  504   a,  and  504   b  may not include any power and/or communication lines but may be used only for securing or stabilizing aerostat  50 . 
         [0051]    Referring to  FIG. 5B , one or more of the tethers  500 ,  502 ,  504   a,  and/or  504   b,  may be collected into a single tether  510  that is secured to ground unit  52 . Collecting tethers  500 ,  502 ,  504   a,  and  504   b  in this manner may ease their management when used to secure or stabilize aerostat  50 . 
         [0052]    Referring to  FIG. 6 , one exemplary embodiment of an aerostat  600  that includes a non-segmented rigid outer envelope  602  is shown. Aerostat  600  further includes controller  126 , and propulsion module  130 . In another embodiment, instead of being rigid, outer envelope  602  includes an inflatable shell. One or more ballonets may be disposed within outer envelope  602  to control lift and stability of aerostat  600 . Similarly to aerostat  50 , one end  56  of tether  54  is releasably coupled to attachment point  58  on aerostat  600 . Another end  60  of tether  54  is coupled to attachment point  62  of ground unit  52 . Ground unit controller  208  and/or remote controller  212  receive information from and transmit instruction signals to controller  126  of aerostat  600  as described above. 
         [0053]    As discussed above, if controller  126  receives an instruction from ground unit controller  208  or remote controller  212  to disengage tether  54  from aerostat  600  or from ground unit  52 , controller  126  is configured to trigger an activation of propulsion unit  130 , confirms that propulsion unit  130  is operational, and disengages tether  54  from the aerostat  600  or from ground unit  52 . Thereafter, controller  126  navigates aerostat  600  in accordance with instruction signals received from ground unit controller  208  and/or remote controller  212 . In one embodiment, aerostat  600  includes tail fins  604  to facilitate control and stability during flight thereof. In another embodiment, controller  126  is configured to operate fins  604 . 
         [0054]    Now referring to  FIG. 7 , a flow chart shows an exemplary method  700 , initiated at Step  702 , for releasing and controlling aerostat  50 . At Step  704 , controller  126  receives instructions signals for an autonomous flight of aerostat  50  to a predetermined location. At Step  706 , controller  126  is configured to determine environmental conditions affecting aerostat  50 . Following the determination of the environmental conditions, controller  126  evaluates an internal pressure of each of the body segments of aerostat  50  and a stiffness of each of the couplings connecting adjacent segments, at Step  708 . Subsequently, controller  126  is configured to determine whether these internal pressure and stiffness evaluations are suitable for the determined environmental conditions, at Step  710 . In case, the evaluations are found to be non-suitable, controller  126  is configured to trigger an appropriate adjustment of the internal pressures of the segments and stiffness of the couplings, at Step  712 . Otherwise, controller  126  is configured to proceed with a determination of whether the propulsion unit is in an operational state, at Step  714 . In the negative, controller  126  triggers a process that renders the propulsion unit operational, at Step  716 . Otherwise, controller  126  proceeds to activate motors associated with the propulsion unit, at Step  718 . Subsequently, controller  126  triggers a disconnection of tether  54 , at Step  720 , and proceeds to navigate aerostat  50  to a predetermined destination based on the received instructions signals, at Step  722 . 
         [0055]    Now referring to  FIG. 8 , in which a block diagram  800  illustrates components of controller  126 . As shown, controller  126  includes a processing unit  802 , a memory unit  804 , a flight data unit  806 , a communication application  808 , a flight control application  810 , an aerostat release application  812 , a segment and coupling control application  814 , and a power control application  816 . Communication application  808  is configured to receive data from communication module  411  and to provide instructions based on the received data. Flight control application  810  is configured to analyze data received from tether controller  412 , altitude and attitude sensors  400 , autopilot unit  402 , and propulsion module  408 , and generate instructions based on the received data. Aerostat release application  812  is configured to request and analyze data indicative of the status of tether  54  and of operational status of propulsion module when autonomous flight instructions are received from remote controller  212 . Power control application  416  is configured to monitor the state of charge (SOC) of power sources integral to aerostat  50  and power transmission provided through power line  202 . 
         [0056]    Processing unit  802  can be implemented on a single-chip, multiple chips or multiple electrical components. For example, various architectures can be used including dedicated or embedded processor or microprocessor (μP), single purpose processor, controller or a microcontroller (μC), digital signal processor (DSP), or any combination thereof. In most cases, processing unit  802  together with an operating system operates to execute computer code and produce and use data. Memory unit  804  may be of any type of memory now known or later developed including but not limited to volatile memory (such as RAM), non-volatile memory (such as ROM, flash memory, etc.) or any combination thereof, which may store software that can be accessed and executed by processing unit  802 , for example. 
         [0057]    In some embodiments, the disclosed method may be implemented as computer program instructions encoded on a computer-readable storage media in a machine-readable format.  FIG. 9  is a schematic illustrating a conceptual partial view of an example computer program product  900  that includes a computer program for executing a computer process on a computing device, arranged according to at least some embodiments presented herein. In one embodiment, the example computer program product  900  is provided using a signal bearing medium  901 . The signal bearing medium  901  may include one or more programming instructions  902  that, when executed by a processing unit may provide functionality or portions of the functionality described above with respect to  FIG. 7 . Thus, for example, referring to the embodiment shown in  FIG. 7 , one or more features of blocks  702 - 720 , may be undertaken by one or more instructions associated with the signal bearing medium  901 . 
         [0058]    In some examples, signal bearing medium  901  may encompass a non-transitory computer-readable medium  903 , such as, but not limited to, a hard disk drive, memory, etc. In some implementations, signal bearing medium  901  may encompass a computer recordable medium  904 , such as, but not limited to, memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations, signal bearing medium  901  may encompass a communications medium  905 , such as, but not limited to, a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, etc.). 
         [0059]    It will be appreciated that some embodiments may be comprised of one or more generic or specialized processors such as microprocessors, digital signal processors, customized processors and field programmable gate arrays (“FPGAs”) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and/or apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. 
         [0060]    In one embodiment, the method  700  may also be implemented in hardware using any of the following technologies, or a combination thereof, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc. 
         [0061]    In the foregoing specification, specific embodiments have been described. However, various modifications and changes can be made without departing from the scope of the claims herein. For example, method steps are not necessarily performed in the order described or depicted, unless such order is specifically indicated. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the claims.