Abstract:
A system is disclosed whereby a sensor, communication device, or other payload may be lofted to an operational altitude and maintained over an area of interest for some time by a relatively inexpensive and disposable buoyant aircraft, then returned intact to its point of origin or another desired location by a reusable but also relatively inexpensive non-buoyant aircraft. Automatic unpiloted control is used for all stages of flight, including ascent, loiter, return, and landing Specialized equipment can be provided to simplify launch procedures, reducing the number of personnel required to operate the system.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    This invention pertains in general to aeronautical platforms for carrying command, control, communications, computing, intelligence, surveillance, and reconnaissance (C4ISR) capabilities to near-space (altitudes between 65,000 feet and 120,000 feet), and returning same to the point of launch or another desired location. The invention pertains in particular to a novel hybrid near-space platform that combines a lighter-than-air vehicle for lift and loiter with a winged aerodynamic vehicle for payload return. The invention further pertains in particular to ground support and launch equipment associated with such platforms. 
       BACKGROUND OF THE INVENTION 
       [0002]    Balloon systems have been used for decades to carry atmospheric sensors, surveillance equipment, and communications gear to various altitudes. Substantial prior art is documented in  The Moby Dick Project: Reconnaissance Balloons Over Russia  by Curtis Peebles (1991, Smithsonian Books), as well as in a lengthy Air Force bibliography located at http://www.wrs.afrl.af.mil/library/balloon.htm. In general, earlier, systems either used a disposable payload, or a parachute system to return the payload safely to the ground. Older parachute systems were uncontrolled, but sometimes provided tracking signals; payload recovery involved either elaborate airborne snatches or extensive hunting over the landing zone. More recent systems, disclosed in various NASA research reports add guidance and control capabilities to the parachute, providing some flexibility to choose a landing site within a small target range. Inflation and launch has historically required calm weather and numerous personnel. 
         [0003]    Certain applications require low-cost, rapid deployment of payload capability over an area of interest, with minimal operations personnel and maximal probability of retrieving the payload. Such a capability demands a system that can be launched on very short notice by as few as one to two people, ascend to the target altitude and location automatically with as little energy expenditure as possible, and return the payload to the point of launch or another designated spot as safely as possible. 
         [0004]    In view of the above, the present invention provides a solution to the need cited above. As those skilled in the art recognize, there can be many different implementations of the present invention. For example, an embodiment of the present invention can include may aspects of the invention, including some of the following. 
         [0005]    A cylindrical plastic-film balloon envelope design is used to provide an inexpensive buoyant platform. This design is well-known to those skilled in the art as being easy to manufacture in quantity, because it does not require the design specific curved scams of a so-called “natural shape” envelope. A range of envelope sizes can be provided so that a deployable system can fly individual platforms at any altitude as required by the application and weather conditions; for example, five “family” sizes can cover the range from 60,000 feet to 100,000 feet altitude for one specific payload mass range. A novel adjustable end-fitting can be provided so the specific balloon volume for the desired altitude required can be set at launch time. The system operator simply selects the smallest family size that can reach the required altitude, adjusts the end fitting to the precise balloon length needed, and cuts off excess material. While cylindrical envelopes are used in an embodiment to provide inexpensive lift, other shapes can be used in an alternate embodiment to optimize the flight differently. For example, a natural shape envelope could be used to increase envelope performance or efficiency. Additionally, an aerodynamically shaped envelope could be used to provide a tactically launched high altitude airship. In this case the PRV would be powered to provide the airships propulsion system. 
         [0006]    A pair of techniques from prior art are used to simplify launch procedures and reduce personnel requirements. Because these balloons are very large, when filled they present significant surface area to any wind present at launch. This can be a substantial safety hazard to launch personnel, and creates a great risk of equipment loss. To reduce the surface area at launch, thereby reducing the risks and allowing the platform to be launched in higher winds, a two-cell design is used. A smaller tow cell is attached to the larger main cell, so that the main cell remains unfilled until the pair has accelerated to a speed close to that of the prevailing winds, thereby minimizing the effective wind load on the large main envelope. In addition, the main balloon cell is packed in a deployment bag which includes an automatic release mechanism. When an appropriate altitude or time after launch is achieved, a control system activates the release mechanism, thereby deploying the main cell. Rather than a large sail area at launch, the packed main cell is a compact bundle that does not catch any wind. This elimination of surface area reduces the potential for damage to the gossamer structure due to high wind loading; it also reduces the number of personnel required by making the “launch train” dramatically shorter, in turn eliminating related hazards to personnel and equipment at launch. The tow cell and the main cell are connected via an intercell tube fitting, so that as the combination rises the buoyant gas expands to fill both envelopes. 
         [0007]    For certain flight requirements, management of lifting-gas flow between the tow cell and the main cell may be accomplished via a valve in the intercell tube fitting. This valve is controlled by the platform management computer (see below) via a wireless local communication link that is separate from the main platform communication links described below. Using a wireless link for this local communication avoids the complication of adding flexible wires to the packed main cell, and is a novel approach. During ascent, closing this valve prevents further expansion of the lifting gas into the main cell envelope, which stops the ascent at a particular altitude. Reopening the valve permits the lifting gas to continue expanding into the main cell, thereby resuming the ascent. In an alternate embodiment, the valve may be installed in the tow cell&#39;s top fitting, allowing the ascent to be slowed or stopped by venting lifting gas rather than forcing it into the main cell. Depending on altitude, duration, and the amount of free lift required for a particular flight profile, to store the extra lifting gas that may be used in either of these altitude control schemes the tow cell may be enhanced to “super-pressure” capability so that it can accommodate the gas pressure that builds behind the closed valve as the platform rises. While super-pressure balloons themselves are known to those skilled in the art, their simultaneous application as a tow cell and as a gas reservoir in a multicell platform is novel. 
         [0008]    A novel apparatus is also used to further simplify launch procedures, reduce personnel requirements, and expand the range of wind conditions in which launch can be accomplished. An adjustable, durable fabric tent is used to enclose the tow cell while it is being filled prior to launch. Weighted along its length and anchored at the filling end, this tent, or launch bag, provides a calm environment in which to fill the tow cell with buoyant gas. The launch bag is designed with an opening at one end that permits attachment of a filling hose to the enclosed tow cell, and an opening at the other end through which the intercell tube fitting mentioned above protrudes so that the main cell and payload may be attached to the tow cell after it has been filled. The launch bag is designed so that its size can be adjusted to match the volume of lifting gas required for a particular launch. Filling of the enclosed tow cell can be easily terminated upon achieving the preset volume, either manually by observation of the achieved size, or automatically by use of a back-pressure shutoff mechanism in the fill nozzle. After the tow cell is filled, the fill nozzle is removed, and the main cell and payload are attached. Since the attachment point for these items is at the center of the tow cell&#39;s circular cross-section, they rest on a cradle which is designed both to hold them up and to roll around. Because of the anchor and weight arrangement described above, as well as the rolling cradle on which the payload rests, the entire assembly can adjust with changing winds, providing an optimal positioning for launch without personnel or vehicles having to move around carrying the flight train. Launch is performed by pulling open a single hook-and-pile (Velcro) seam along the top of the launch bag, thus releasing the tow cell into the air. Layout, adjustment, filling, payload attachment, and launch can be performed by as few as two persons in its current embodiment or by a single individual with the addition of package handling straps. While the use of such an apparatus is inspired by the prior art “covered wagon” system (see Peebles 1991 cited above), the present launch bag offers significant improvements on that device. First, the launch bag is constructed entirely of fabric, and sized for the tow cell in the present multicell platform rather than a much larger single-cell platform, so it can be handled easily and stored/transported compactly; the covered wagon was a hard-sided truck trailer sized for a large single envelope. Second, the tent-like structure of the launch bag fills with wind, stabilizing the launch bag, and aiding in optimally orienting the launch system parallel to changing winds with a minimum of human interaction; in contrast, the covered wagon uses a hard sided trailer to completely shelter the balloon from the wind and would require motorized trailer movement for optimal orientation to changing winds. Finally, the launch bag and filling process are integrated such that the size-adjusted bag controls the volume of lifting gas filling the tow cell automatically. Operating personnel simply set the bag for the desired payload/altitude combination and a backpressure shutoff valve in the fill nozzle stops the flow of buoyant gas into the tow cell without further operator intervention. These improvements combine to create a novel launch system that can be used for tactical deployments in high winds. 
         [0009]    The payload may be encapsulated in a payload return vehicle (PRV), which is an aircraft designed to be released from the balloon after it can no longer remain in the area of interest, then fly to a predetermined location and land safely. The landing location may either be the same as the launch point, or some other location determined by application requirements. In general, the payload return vehicle is a lightweight airframe capable of autonomously recovering to stable flight after being dropped from the balloon in very thin atmosphere (also known as “pulling out”), navigating to the landing location, and landing automatically. Return flight and landing may optionally be taken over by a pilot via a remote-control mechanism. The PRV may be of any size and configuration appropriate to the payload for a particular application, with the balloon platform size(s) being adjusted accordingly. In an embodiment, the PRV is of a size and weight such that it can be handled by one or two people in order to align with the launch-complexity goals of the novel launch subsystem described above. Depending on the application requirements such as loiter time, return distance, stealth, and others, several degrees of freedom can be exercised in PRV choice. For example, low aspect ratio, high aspect ratio, or hybrid formats may be used. Either gliding or powered variants are possible, and power plants can incorporate any kind of engine including propeller, jet, or rocket. Propulsion may be optimized for low-altitude performance to extend the return range, for high-altitude performance to assist in station-keeping, or both. The PRV may be constructed from any of several different types of material depending on application requirements such as speed, strength, or serviceability. For example, the PRV may be primarily constructed from polymer foam sheets, with wood and fiberglass reinforcements at high-stress points. Depending on application requirements, other materials may be appropriate as well, including composites, metals, films, or fabrics. Payload accommodations may include shock-resistant cases, dedicated attachment points, integrated/active surfaces (such as radar or communication antenna panels, openings, or embedded optical lense&#39;s), extension/retraction mechanisms, and/or reserved volumes as appropriate to the application. Payloads may provide communication support, data collection, observation, radar, or any other function that may benefit from operation in near-space. 
         [0010]    An example PRV is a faceted lifting-body design derived from Barnaby Wainfan&#39;s FacetMobile (http://members.aol.com/slicklynne/facet.htm). This design provides a low-cost, easily repairable platform that performs well in atmospheric densities from sea-level to at least 100,000 feet. Its low-aspect-ratio form factor offers ample allowance for payload integration; relative to the overall size of the aircraft, large internal volumes are available for installing equipment, and very large surfaces are available for integrating flat active devices such as radar or communication antenna panels. The low aspect ratio also supports safer launch and landing behaviors due to the relatively short wingspan. 
         [0011]    In an embodiment, the FacetMobile PRV can be primarily constructed from polymer foam sheets, with wood and fiberglass reinforcements at high-stress points. These materials are inexpensive, leading to a low-cost aircraft. They also are relatively simple to work with, supporting a high-tolerance, low-skill manufacturing process and rapid, low-skill field repairs. 
         [0012]    In an embodiment, a hard-shell carrying case payload pod can be provided to contain and protect payload electronics. The case is easily removable, and in the event of a hard landing will protect the payload from damage. It can also be carried away from a crash site intact even if the PRV itself is irreparable. Carrying cases of suitable size and strength are readily available on the open market, and are well known to those skilled in the art. Certain modifications are required, however, in order to provide holes for mounting the case to the PRV and for attaching to the balloon-system release mechanism. 
         [0013]    In an embodiment, a payload pod access panel can be provided on the PRV bottom facet. This opening provides easy access to the PRV interior for installing and removing the payload pod described above. The PRV speed brake is embedded in the access panel, and so its control connections are modified to be easily detached. 
         [0014]    In an embodiment, payload pod mounting brackets can be provided inside the PRV to accommodate the shape and attachment points of the hard-shell carrying case described above, thereby providing a secure installation and simple removal. 
         [0015]    In an embodiment, a detachable PRV nosecone can be provided to house all platform avionics separately from the payload pod to maximize payload capacity while providing optimal interchangeability among PRV airframes and control subsystems. In an alternate embodiment, the platform avionics are collocated with the payload inside the aforementioned hard-shell carrying case. 
         [0016]    In an embodiment, a removable PRV vertical stabilizer can be provided, into which a payload antenna may or may not be embedded as required by a particular payload. The optional vertical stabilizer can support and provide aerodynamic cover to an antenna if required. A mounting system can be provided on the appropriate facet that makes the combination stab/antenna interchangeable with a non-antenna stab or a filler for no stab at all. 
         [0017]    The PRV is integrated with the buoyant platform in two novel respects. First, the control avionics and release actuators for the balloon are carried in the PRV so that disposable elements are reduced and the sophisticated control elements can be recovered along with the payload. Second, ballasting mechanisms and materials are carried in the PRV so that ballast can be discharged from the bottom of the flight train rather than risking damage to the PRV and its payload due to ballast falling from the balloon above; this design has the additional benefit of allowing the PRV to utilize any ballast that remains from balloon operation to increase wing loading, enhancing its ability to overcome higher adverse winds during the return flight. 
         [0018]    The combined lift/return platform includes appropriate control componentry, including an autopilot, communication links, and a platform management computer with sensor and driver interfaces for both platform-specific functions and payload control. The autopilot handles automatic navigation, flight stability, and landing of the PRV during return flight. Two bidirectional communications links are provided. A high-speed line-of-sight (LOS) channel supports manual piloting by an operator on the ground if that is appropriate in a particular application. A low-speed beyond-line-of-sight (BLOS) channel permits a ground operator to monitor platform status and change flight plan parameters as necessary. In an embodiment the LOS channel is a license-free radio operating in an ISM band, while the BLOS channel is an Iridium satellite modem. Alternate embodiments may use other channels as appropriate for a specific application. The platform management computer controls main balloon deployment, ballast release, super-pressure balloon gas valving, and PRV release. It can also enable and disable payload power, and depending on the specific application it may sense and report on payload health and status or be used for payload telemetry and control. In an embodiment the autopilot and platform management computer are implemented as separate units with appropriate interconnects; in an alternate embodiment these functional elements may be integrated into a single unit. 
         [0019]    The autopilot and platform management computer use the communication links to interact with system operators via a compact ground station. This ground station provides an operator with appropriate status information and command capabilities in accordance with principles well-known to those skilled in the art. A novel mission planning capability is also provided, wherein the buoyant platform&#39;s ascent and loiter, and the PRV&#39;s return flight, are modeled in the context of prevailing and forecast atmospheric conditions (primarily wind speed and direction) and aerodynamic characteristics of the specific PRV design. System operators use this information to plan launch location and timing, PRV release location and timing, and flight plan changes if necessary. The ground station is capable of managing multiple simultaneous ascent, loiter, and return flights in support of continuously delivering fresh platforms to an area of interest and retrieving spent payloads. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The invention will be better understood from a reading of the following detailed description in conjunction with the drawing figures, in which like reference designators are used to identify like elements and in which: 
           [0021]      FIG. 1  illustrates an overall system including flight and ground components; 
           [0022]      FIG. 2  illustrates a balloon platform physical details in multiple views including individual components; 
           [0023]      FIG. 3  illustrates a payload return vehicle exterior physical details in multiple views; 
           [0024]      FIG. 4  illustrates a payload return vehicle interior physical details in multiple views, including in particular a payload pod interfaces and individual components; 
           [0025]      FIG. 5  illustrates a functional architecture of the in-flight control subsystems; 
           [0026]      FIG. 6  illustrates a launch apparatus physical details in multiple views including individual components; and 
           [0027]      FIG. 7  illustrates a functional architecture of the ground-based control station. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    The high-level diagram of  FIG. 1  shows components of an embodiment of the present invention and their relationships to one another in an example operational context. Tactical Balloon and Payload Return System  100  comprises primarily a lighter-than-air vehicle for low-energy lift to altitude, Tactical Balloon  200 ; an aerodynamic winged vehicle for payload containment and return, Payload Return Vehicle (PRV)  300 ; a set of equipment that facilitates launching the flight items, Tactical Launch Apparatus  600 ; and a set of equipment that facilitates monitoring and controlling the flight items, Ground-Based Control Station  700 . Each of these components is detailed in subsequent paragraphs. 
         [0029]    Three instances of Tactical Balloon  200  are shown, representing three distinct states of deployment. Tactical Balloon  200 - 1  is in the pre-launch configuration, coupled closely with the components of Launch Apparatus  600 . Gas Supply  130 , depicted as a truck hauling large tanks but potentially a fixed source or a set of small tanks as well, is providing lifting gas through Supply Hose  135  to Launch Apparatus  600 , which is in turn inflating the tow cell of Tactical Balloon  200 - 1 ; the main cell of Tactical Balloon  200 - 1  remains packed in this configuration. Tactical Balloon  200 - 2  is in the launch configuration, with the tow cell inflated and the main cell still packed. Finally, Tactical Balloon  200 - 3  is in the float configuration, with both tow and main cells inflated. 
         [0030]    Similarly, five instances of PRV  300  are shown, corresponding with various stages of flight and depicting multiple styles of airframe that may be used. PRV  300 - 1  is attached to Balloon  200 - 1  and resting in the launch cradle portion of Launch Apparatus  600  prior to launch. PRV  300 - 2  is attached to Balloon  200 - 2  in the early stages of ascent. PRV  300 - 3  is attached to Balloon  200 - 3  and its payload is serving the mission over Area of Interest  140 . PRV  300 - 4  has been released from its Tactical Balloon  200  (not shown), and is in return flight toward Landing Area  150 , which may be near the point of launch or at some other designated location. Finally, PRV  300 - 5  has returned to Landing Area  150  and is shown about to touch down. In addition, two different styles of airframe are shown in  FIG. 1 , with PRVs  300 - 1 ,  300 - 3 , and  300 - 5  depicted as lifting bodies, and PRVs  300 - 2  and  300 - 4  depicted as a high aspect ratio glider. Depiction of these particular styles in the figure does not constrain System  100  to using only those types; as described in the summary, multiple airframe types may be applied. The remainder of this disclosure will, however, describe a particular lifting-body design as an embodiment based on its use in the initial implementation. 
         [0031]    Ground Station  700  communicates with PRVs  300  through both line-of-sight (LOS) and beyond-line-of-sight (BLOS) technologies. LOS Communication Links  125  provide connections with PRVs  300  that are in range of Ground Station  700  via LOS technology. Depending on the location of Ground Station  700  or the existence of multiple Ground Stations  700 , LOS Communication Links  125  may be used during pre-launch checkout of PRV  300 - 1 , and during landing of PRV  300 - 5 . BLOS communication, for the purpose of the present invention, is accomplished via Satellite Communication Network  110 . Network  110  is any satellite communication system that offers data communication between distant users. Ground Station  700  and PRVs  300  use BLOS Communication Links  115  to Network  110  for communicating with one another when outside the reach of Ground Station  700  via LOS Communication Links  125 . In an embodiment, Network  110  is the Iridium system; alternate embodiments may use other existing and emerging systems such as GlobalStar, MilStar, MUOS, and others. 
         [0032]      FIG. 2  provides detail of Tactical Balloon  200  in multiple views. 
         [0033]    Tactical Balloon  200 - 2 , the launch configuration, is shown in  FIG. 2A . In this configuration, Tow Cell  210  has been inflated via Fill Tube  215  and capped. Tow Cell  210  may be constructed, according to methods known to those skilled in the art, of lightweight film and gores to act as a zero-pressure cell, or of heavier film and stronger gores to act as a superpressure cell. Main Cell  220  is packed, and attached to Tow Cell  210  via Intercell Tube  230 . Payload Package Adapter  240  provides a fitted bridge between the shape of Packed Main Cell  220  and that of, in an embodiment, a PRV  300 . In alternate embodiments, Payload Package Adapter  240  may be shaped differently from that shown here so as to provide a fitted bridge to other types of PRV  300  airframe, or even other kinds of non-returning payload that may be carried by Tactical Balloon  200 . Additional detail on the foregoing elements is provided below. 
         [0034]    Tactical Balloon  200 - 3 , the float configuration, is shown in  FIG. 2B . In this configuration, Tow Cell  210  has reached its maximum volume due to reduced atmospheric pressure at very high altitude, and Main Cell  220  has not only been deployed but also inflated to near its maximum volume by the expanded lifting gas overflowing from Tow Cell  210  through Intercell Tube  230 . End Fitting  225  is now visible due to the deployment of Main Cell  220 . End Fitting  225  seals the bottom of the Main Cell  220  envelope, and provides a hard object against which to secure Payload Package Adapter  240 . As described in the summary, End Fitting  225  is the novel mechanism whereby the size of Main Cell  220  may be adjusted by an operator prior to launch: a mission altitude is chosen, the Main Cell  220  envelope is trimmed to a length corresponding to the volume of lifting gas required to achieve that altitude with the total weight of Tactical Balloon  200 , PRV  300 , and payload; then a small vent opening is cut near the bottom of the balloon and the remaining bottom material of Main Cell  220  is wrapped around End Fitting  225  and knotted to secure the envelope. 
         [0035]      FIG. 2C  provides extensive detail of the various tubes and fittings that form interfaces between the cells of Tactical Balloon  200 , and between those cells and other elements of System  100 . These components can be comprise primarily inexpensive plastic such as polyvinyl chloride (PVC),lightweight metal such as aluminum, thin steel bands, or any other material suitable for a given application, including combinations of such materials. 
         [0036]    Starting at the top of Tactical Balloon  200 , Fill Tube  215  is attached to one end of Tow Cell  210 , and provides an opening through which lifting gas is introduced. The primary structure of Fill Tube  215  is provided by the hollow, cylindrical Tow Cell Top Fitting  211 . This element features wide grooves on its outer surface, to which the film of Tow Cell  210  can be attached with tight bands. The figure depicts a fitting with three such grooves, which in an embodiment is used for a super-pressure Tow Cell  210 ; not shown is a version with only two grooves, which provides sufficient fastening space for a zero-pressure Tow Cell  210 . The outside end of Tow Cell Top Fitting  211  is capped with Mounting Plate  217 , which is in turn held in place by Band Clamp  218 . Mounting Plate  217  seals the opening and provides a surface for Diffuser Coupling  216 , which is attached through a hole in the center of Mounting Plate  217 . Diffuser Coupling  216  provides the hole though which the inflation mechanism is inserted to supply lifting gas to Tow Cell  210 . Not shown, but obviously required, is the cap that fits over and seals Diffuser Coupling  216  after inflation is complete. 
         [0037]    Intercell Tube  230  actually comprises two fittings that are mounted separately in the two cells of Tactical Balloon  200 , and then joined prior to launch when the particular Tow Cell  210  and Main Cell  220  have been chosen for a particular mission. The first, Tow Cell Bottom Fitting  212 , mirrors Tow Cell Top Fitting  211  by providing two or three grooves for attaching a zero-pressure or super-pressure envelope. This end of Tow Cell  210  is capped by Membrane  231 , so that when Tow Cell  210  is being filled with lifting gas the envelope is sealed. The second, Main Cell Top Fitting  221 , similarly provides three grooves for attaching the large main envelope. A Valve Mounting Ring  233  is also attached to Main Cell Top Fitting  221 , providing an airtight, threaded receptacle into which Intercell Valve  235  may be installed if required for a particular mission. 
         [0038]    When two envelopes are selected for a particular mission, after inflation and prior to launch Membrane  231  is punctured by an operator so that lifting gas will flow between the two cells at the appropriate time, then they are immediately joined by aligning Tow Cell Bottom Fitting  212  with Main Cell Top Fitting  221  and attaching them firmly to one another with Band Clamp  232 . If the mission calls for multiple float altitudes, an Intercell Valve  235  is installed in Valve Mounting Ring  233  of the selected Main Cell  220  before puncturing Membrane  231  and connecting the two fittings. 
         [0039]    Intercell Valve  235  is constructed to fit inside the cylinder of Intercell Tube  230 . The valve itself comprises a Seal Ring  238 , against which is seated a Valve Door  237 . Seal Ring  238  is threaded to mate with Valve Mounting Ring  233 , and features a compressible surface with which the hard edge of Valve Door  237  forms an airtight seal. Operation of Intercell Valve  235  is effected by Motor  535 , an inexpensive linear stepper motor that opens or closes Valve Door  237  in increments as directed by Controller  534 . Controller  534  is a circuit board containing a power relay such that power from Battery  531  is either blocked or provided to Motor  535  according to the commanded direction of movement. Controller  534  also contains a wireless Transceiver  532  attached to Antenna  533 , whereby commands are received from a platform controller in PRV  300 ; more information on said platform controller is provided later in this specification. In addition to receiving commands, Controller  534  may also transmit sensor readings to the platform controller via Transceiver  532 . In an embodiment, these sensor readings include voltage measurements from a transducer that indicates the pressure in Tow Cell  210 , voltage measurements from a linear potentiometer that indicates the shaft position of Motor  535 , and binary signals from a contact switch that indicates closure of Valve Door  237  against Seal Ring  238 . Alternate embodiments may include sensors that operate by measuring quantities other than voltage, and sensors that provide indications other than those cited above. Finally, a metal spider bracket, Motor Mount  236 , is anchored in Seal Ring  238  forming a sturdy semi-conical structure to which Motor  535 , Controller  534 , and Battery  531  are attached. 
         [0040]    At the other end of Tactical Balloon  200 , and completing the tour of  FIG. 2C , Main Cell End Fitting  225  is shown to be a spool-shaped item designed to be wrapped by the film from which the Main Cell  220  envelope is constructed. After sizing Main Cell  220 , the operator seals it by wrapping the end around the smooth center portion of Main Cell End Fitting  225  and knotting the remainder of the film. The flanges of End Fitting  225  provide support to the knot so that it does not unravel, and offer a hard anchor point to which the payload package is attached. 
         [0041]      FIG. 2D  provides detail of the packing and deployment mechanism used to launch Main Cell  220 . Prior to launch, the Main Cell  220  envelope is packed in Deployment Bag  221 . Main Cell Top Fitting  221  protrudes through an opening in the top of Deployment Bag  221  (not visible in  FIG. 2D  due to the bottom-up orientation shown) so that it may be attached to Tow Cell Bottom Fitting  211  as described above. Deployment Bag  221  is fastened to Main Cell Top Fitting  221  with four Straps  224 , of which only two are visible in  FIG. 2D , so that Main Cell  220  doesn&#39;t deploy through that opening. Straps  224  are wrapped around to the bottom of Deployment Bag  221  and into Payload Package Adapter  240 . At the juncture of Straps  224  inside Payload Package Adapter  240 , Deployment Mechanism  223  connects Straps  224  to one another so as to fasten Payload Package Adapter  240  snugly against the opening and completely enclose the Main Cell  220  envelope inside Deployment Bag  221 . When commanded to release, Deployment Mechanism  223  lets go of Straps  224 , thereby allowing Main Cell  220  to unfurl from Deployment Bag  221 . To avoid the stress on Main Cell  220  of an uncontrolled descent and sudden stop by Payload Package Package Adapter  240  and its attached payload (a PRV  300  in an embodiment), a folded strap is tacked together by a rip stitch to form Deployment Brake  222 . This device slows the descent rate of PRV  300  and corresponding deployment rate of Main Cell  220 , thereby reducing the aforementioned stress and preventing failure of the Tactical Balloon  200 . 
         [0042]      FIG. 3  provides exterior detail of a Payload Return Vehicle  300  in multiple views. As previously described, PRV  300  is derived from the FacetMobile airframe, with custom features to support the goals of System  100 . 
         [0043]      FIG. 3A  shows a perspective view of PRV  300  from the top. The vehicle features three main sections, Fuselage  310 , Starboard Wing  320 , and Port Wing  330 . Fuselage  310  further features a Vertical Stabilizer  311  and a Nosecone  315 , which figure prominently in later paragraphs. Wings  320  and  330  each feature Ailerons  322  and  332 , and Winglets  325  and  335 , all of which provide functionality that is well known to those skilled in the art. In addition to these fundamental structural attributes, a Pitot  340  is provided to support flight control in a fashion that is well known to those skilled in the art; Pitot  340  is attached in an embodiment to Starboard Wing  320 ; that choice is essentially arbitrary, and an alternate embodiment could place Pitot  340  in any other feasible location. Also noted in  FIG. 3A  is an exemplary payload peripheral, a Payload Antenna  350  that is partially embedded in Stabilizer  311  for support and aerodynamic cover. This is an example of payload accommodation flexibility as discussed above. 
         [0044]      FIG. 3B  shows a front orthogonal view of PRV  300 . While no features are explicitly labeled here, the features labeled in  FIG. 3A  are visible and recognizable to those skilled in the art. 
         [0045]      FIG. 3C  shows a side orthogonal view of PRV  300  in a partially disassembled state. Primary features from  FIG. 3A  are again shown here. Labels are provided for some, as the view from this angle is somewhat different. In particular, due to the faceted lifting body shape of the PRV  300  airframe, distinguishing Fuselage  310  from Wing  320  requires the viewer to assume a perspective in this view that may not be obvious except to those exceptionally skilled in the art. As noted above, PRV  300  also features a detachable Nosecone  315  to house flight control avionics, as well as an interior bay to accommodate payload equipment and certain other flight control equipment to be described later in the context of  FIG. 4 . Nosecone  315  is shown here completely separated from the rest of Fuselage  310 . Payload Access Panel  314 , which is on the bottom of PRV  300 , is also visible in  FIG. 3C  detached from its installed location. Attached to Panel  314  is Speed Brake  312 , the third control surface of PRV  300  (the other two being Ailerons  322  and  332  as previously shown). Speed Brake  312  can be held flat against Panel  314  when maximum flight velocity is desired, or deployed downward at any angle needed by the flight control function to slow the airframe in flight. Landing Skid  313 , a hardened protrusion designed to reduce damage to the airframe during landing, is visible in this view as well. In an embodiment, cost and complexity lead the PRV  300  implementation to use skids for landing rather than wheels or other devices; those may be used in an alternate embodiment as required. 
         [0046]      FIG. 4  provides interior detail of one preferred Payload Return Vehicle  300  in multiple views. 
         [0047]    In the first view,  FIG. 4A , Payload Access Panel  314  is removed from the underside of PRV  300  to show the aforementioned interior bay of Fuselage  310 . Landing Skids  313 , described previously, are clearly visible in this view. The dominant feature in this view is Payload Pod  420 , a case designed to transport electronic equipment while protecting it from rough handling. In an embodiment this Payload Pod  420  is a hard plastic carrying case made by Pelican Products and generally known as a Pelican 1500 Case. Alternate embodiments may use different styles, sizes, materials, and manufacturers as appropriate to the requirements of the payload. 
         [0048]    Four structural protrusions integral to the interior of PRV  300 , labeled Payload Pod Mounts  410 , provide sturdy attachment points for Payload Pod  420 . The two Pod Mounts  410  on the right side of the figure have vertical Payload Pod Fasteners  411 , embedded bolts over which matching holes in Pod  420  are fitted and secured with nuts. In an embodiment using a Pelican Case, these holes are built in by the manufacturer to accommodate locks. Featured in an embodiment, but obscured by the view angle, each of the Pod Mounts  410  on the left of the figure has a lateral hole drilled through it to align with a matching lateral hole drilled in the flange supporting the corresponding Pelican Case hinge; a pin through each of these matched hole sets secures that side of Pod  420 . Alternate embodiments using other case structures for Pod  420  may use other forms of attachment to Mounts  410 . 
         [0049]    On either side of Pod  420  are Ballasters  430 . These devices carry ballast material that can be jettisoned as needed for Tactical Balloon  200  altitude adjustments and flights lasting more than twenty-four hours, as is well known to those skilled in the art. In an embodiment, each Ballaster  430  holds approximately five pounds of material; alternate embodiments may provide larger or smaller capacities, or more than two Ballasters  430 , depending on payload and mission requirements. Ballasters  430  are aligned inside Fuselage  310  by structural protrusions, labeled Ballaster Supports  435  in the figure. The Ballasters  430  may be located in other suitable locations, such as the Wings  320  &amp;  330 . 
         [0050]    In general, Pod  420  may carry electronic equipment that can be enabled and disabled by a controller in Nosecone  315  (not shown in this figure, but described in a later paragraph). Ballasters  430  are also controlled from Nosecone  315 . The interconnects required to support this control, and potentially others depending on the payload and mission, pass through the holes labeled Nosecone Wiring Access  450 . Equipment in Pod  420  may also interact with peripheral equipment positioned inside Starboard Wing  320 , Port Wing  330 , or the rear of Fuselage  310 . For example, as previously noted an embodiment features a payload antenna embedded in Stabilizer  311 . The interconnects between a payload and its peripherals may pass through the hole labeled Wing Wiring Access  440 , or through a similar hole on the opposite side that cannot be seen due to the angle of the drawing. 
         [0051]      FIG. 4B  depicts the structure of Nosecone  315  in its disassembled state, the components of which are an Avionics Tray  460  and an exterior Cowling  316  into which it fits. Avionics Tray  460  is a modular platform on which are mounted the flight control systems, also known to those skilled in the art as avionics, supporting both Tactical Balloon  200  and Payload Return Vehicle  300 . Major components mounted on Avionics Tray  460  include a Satellite Communications (SATCOM) Transceiver  523 , a Tactical Balloon C 3  Unit  540 , and an Autopilot  550 . A detailed description of these components and their peripherals is given below in the context of  FIG. 5 . Interconnects between components mounted on Avionics Tray  460  and those mounted elsewhere in PRV  300  pass through the holes labeled Fuselage Wiring Access  461 , which align with the aforementioned Nosecone Wiring Access ports  450 . So that components may be tested and replaced as necessary, Avionics Tray  460  is designed to be easily removable from Cowling  316 , and in turn Nosecone  315  is designed to be easily removable from Fuselage  310 , using fasteners such as nylon screws or clips well known to those skilled in the art. 
         [0052]      FIG. 4C  provides detail of Ballaster  430 , which is shown with its release opening facing up but which would be inverted from the pictured orientation in flight. Ballast Container  431  is a jar made of durable, lightweight material such as acrylic, sized to hold the desired amount of ballast material, (roughly five pounds in an embodiment). The ballast material used in the present invention is fine steel shot, which is held in place magnetically and flows smoothly when released using a technique well known to those skilled in the art but implemented with a novel form in the present invention. Holding Magnet  432  is a permanent magnet mounted adjacent to the opening at the top of the figure. It keeps the steel shot inside Ballast Container  431  by bridging the opening magnetically with enough force to hold the shot in the opening against itself, allowing friction and stacking to oppose gravity and prevent flow. Release Electromagnet  433  is also mounted adjacent the opening, but with an opposite polarity to the permanent Holding Magnet  432 . When energized by its controller, Release Electromagnet  433  cancels the magnetic field of Holding Magnet  432 , allowing steel shot to flow out of Ballast Container  431  under the influence of gravity. A controlled amount of ballast can thereby be released through carefully timed activation of Release Electromagnet  433 . Finally, Ballaster  430  is fastened to the interior of PRV  300  via screws through Mounting Bracket  434 . 
         [0053]    A functional architecture of the control system that can be used in Tactical Balloon  200  and PRV  300  is found in  FIG. 5 . Flight Control System  500  is a complex conglomerate of modules designed to communicate with Ground Station  700 , manage the various states of Tactical Balloon  200 , and manage speed, heading, altitude, and stability of PRV  300  during all stages of its flight. Three types of interconnect are shown in the figure. Power feeds are represented by the thick single lines, while signaling connections are represented by the slightly thinner single line. Airflow tubing is represented by thin, double lines. 
         [0054]    One component of Flight Control System  500  is Return Vehicle Avionics  520  which, as shown physically in  FIG. 4B  comprises three primary modules. Aircraft Autopilot  550  provides the functions required to manage stable flight of PRV  300 . In an embodiment it is implemented by a Piccolo autopilot from Cloud Cap Technology, and encapsulates all the functions required to control PRV  300  flight except sensors which must be external to access the environment properly. Other implementations could be chosen in alternate embodiments; although in that case the specific functional encapsulation may be different than that described here, the same functions would be provided. 
         [0055]    Autopilot  550  features at its core a Control Computer  551  responsible for real-time estimation of position, velocity, and attitude coupled with real-time computation of control surface angles required to achieve the flight goal. Control Computer  551  drives control surface Servomotors  501 , which are outside Avionics  520  but connected to it electrically while being mechanically connected to their respective control surfaces as previously described, to positions that accomplish those desired angles. In an embodiment, Autopilot  550  also provides a piloted mode in which automatic flight can be overridden by an operator at Ground Station  700  if conditions demand. In addition to these core functions, Computer  551  interfaces with several essential functions which in an embodiment are shown as also being components of Autopilot  550 , but which in an alternate embodiment might be implemented external to Autopilot  550 . 
         [0056]    First of these is Line-of-Sight Communications Transceiver  552 , which supports commanding, telemetry, and payload data flow between Autopilot  550  and Ground Station  700  via a wireless communication link that depends on line-of-sight transmission (sometimes referred to among those skilled in the art as “LOS”). In an embodiment this transmission is based on a radio frequency subsystem operating in the license-free ISM band at 902-928 MHz; an alternate embodiment may use a military band or another technology altogether depending on mission requirements. Transceiver  552  accesses the air via a suitable Antenna  521  tuned to the frequency used; in an embodiment this is a 900 MHz-sized Moxon-style device, which offers a reasonable pattern both directly underneath and laterally all around PRV  300 . 
         [0057]    Next is an Attitude Sensor  553 , which detects changes in orientation that are processed by Control Computer  551  into yaw, pitch, and roll states. In an embodiment this is a microcircuit embedded within the Cloud Cap Technology Piccolo autopilot subsystem, using inertial technologies well known to those skilled in the art. Completing the sensor set is a Pressure Transducer  554  connected to Pitot  340  and Static Tube  503 . These devices, well-known to those skilled in the art, provide measurements of air pressure that are processed into altitude and airspeed states by Control Computer  551  using well known techniques. 
         [0058]    Autopilot  550  also incorporates in an embodiment, or interacts with in an alternate embodiment, a Global Positioning System (GPS) Receiver  555  that provides a periodic measurement of location and altitude based on radiodetermination techniques relative to the well known GPS satellite constellation, independently verifying the results of local computations driven by measurements from Attitude Sensor  553  and Pressure Transducer  554 . This dual approach to position and velocity determination increases the probability of successful navigation. With respect to altitude determination it is essential in System  100 , because many implementations of Pressure Transducer  554 , including the Cloud Cap Technology Piccolo-based preferred embodiment, are not sensitive enough to produce an accurate altitude estimate at the 65,000 to 100,000 foot operational altitudes of Tactical Balloon  200 , though as is known to those well versed in the art, a pitot-static tube measurement is sufficient for dynamic pressure measurement and flight control. 
         [0059]    The second component of Avionics  520  is a Satellite Communications Transceiver  523 . For most of the flight duration of Tactical Balloon  200  and PRV  300 , Line-of-Sight Transceiver  552  is beyond the range of the corresponding transceiver in Ground System  700 . So that system operators may receive telemetry from the flight unit and send commands to it while so out of range, Satellite Communications Transceiver  523  provides beyond-line-of-sight (sometimes referred to among those skilled in the art as “BLOS”) capability. In an embodiment, this is a unit designed to communicate via the Iridium satellite communications network, chosen for its small form-factor electronics, and in particular for its small Antenna  524 . Antenna  524  is a hemispheric patch-style antenna, packaged in a form commonly referred to among those skilled in the art as a “puck.” Alternate embodiments may select other BLOS technologies than Iridium, but it is unlikely that a non-satellite solution will serve. 
         [0060]    The third component of Avionics  520  is Balloon Platform C 3   540 . This device is responsible for lighter-than-air flight management, payload supervision, and power management. At its core is Control Computer  541 , which manages main-balloon release, PRV release, ballast release, valve utilization, and payload utilization according to mission parameters and direct commands. These core functions are accomplished via several peripherals to which Control Computer  541  is attached. 
         [0061]    For valve control, C 3   540  incorporates a Local Wireless Transceiver  542  and corresponding Antenna  543 . This is a low-power radio for transmitting simple commands and receiving simple indications. In an embodiment, Transceiver  542  is constructed of components commonly used for garage-door remote control devices operating at 315 MHz. Control Computer  541  is able to send valve operation commands via Transceiver  542 , and may receive indications of valve position and gas pressure through it. 
         [0062]    For release management, C 3   540  incorporates a set of Deployment Relays  544 , whereby high-current electrical power may be switched under control of Computer  541 . Individual connections are provided to Ballast Release Mechanism  504 , which corresponds to the Release Electromagnet  433  in each Ballaster  430  in  FIG. 4 ; Main Balloon Deployment Mechanism  505 , which corresponds to Deployment Mechanism  223  in  FIG. 2 ; and with Return Vehicle Release Mechanism  506 , which is attached inside PRV  300  to Payload Pod  420 , but not shown in  FIG. 4  due to its location on the side of Pod  420  that is obscured in  FIG. 4A . Each of Release Mechanisms  504 ,  505 , and  506  incorporates either an electromagnet or a resistive heater to convert electrical power into a mechanical action that affects its function, according to principles known to those skilled in the art. 
         [0063]    Payload supervision is designed into C 3   540  so that the platform can detect and control what state the payload is in, as appropriate. For example, a mission may require that the payload be powered off during ascent, turned on at float, and placed in a different mode during return flight. Payload Supervisor  547  cooperates with Payload Supervision Interface  465  adjacent to the payload in Pod  420  to accomplish these tasks. Payload Battery  461  and Payload Equipment  462  are connected to Supervisor Interface  465 , through a relay incorporated therein, instead of directly to one another. This allows Supervisor  547  to enable and disable power to Payload Equipment  462  using a signal on Power Control Connection  561 . Control and status lines on Payload Equipment  462  may likewise be connected through Supervisor Interface  465  and Signal Connection  562  to Supervisor  547 , and driven, interpreted, or simply communicated to an operator by Control Computer  541  as appropriate for the specific application. 
         [0064]    Power management in C 3   540  includes the payload power enablement function of Payload Supervisor  547 , as well as dedicated power conditioning circuits for specific devices within Avionics  520  that require them. In an embodiment, Autopilot  550  manages control surface Servos  501  by modulating power to them, and requires a specific voltage level that is different from its main supply. Servo Power Supply  545  produces this voltage and conditions it so that the required level is maintained regardless of battery level in the main supply. Similarly, in an embodiment SATCOM Transceiver  523  requires yet a different voltage level and supply condition, which is provided by SATCOM Power Supply  546 . In alternate embodiments with other implementations of any Avionics  520  component, alternate power supply modules may be included in C 3   540 . 
         [0065]    In an embodiment, LOS Transceiver  552 , SATCOM Transceiver  523 , and GPS Receiver  555  are connected, as shown in the figure, to Control Computer  551  of Autopilot  550 . Control Computer  551  decommutates incoming messages received on either Transceiver  552  or  523  but bound for Control Computer  541  of C 3   540 , and duplicates position readings from GPS Receiver  555 , and sends them to C 3   540  via the Connection  525  that joins them. C 3   540  likewise sends outgoing messages to Autopilot  520  over Connection  525  for transmission. In an alternate embodiment, any of Transceivers  552  and  523  or GPS Receiver  555  may be connected directly to C 3   540  instead, requiring it to provide access to them for Autopilot  550  via Connection  525 . In yet another alternate embodiment, any of Transceivers  552  and  523  or GPS Receiver  555  may also be duplicated and directly connected to both Control Computers  551  and  541 , removing the need for access via Connection  525  in either direction. 
         [0066]    In an embodiment, electrical power for Avionics  520  can be provided by two sets of batteries sized to the duration of a particular mission. Autopilot Battery  512  powers Autopilot  550  and its modules, while C 3  Battery  514  powers C 3   540 , its modules, and indirectly the modules for which it provides conditioned power. This separation provides an opportunity to balance battery drain between these major functions according to the needs of a particular mission. 
         [0067]    Separate from Avionics  520  and connected to it only via a local wireless interface is Intercell Valve  530 , the functional architecture of which is shown here, and which corresponds to the Intercell Valve  235  depicted structurally in  FIG. 2C . Since Avionics  520  is located inside PRV  300 , and Valve  530  is located at the other end of Main Cell  220 , Valve  530  includes its own Battery  531  to provide electrical power. Local Wireless Transceiver  532  and its antenna  533  are the mirror of Transceiver  542  and its Antenna  543 , receiving commands and sending status. Motor Controller  534  is the destination of any commands, operating Valve Motor  535  as directed to open and close Valve Door  237 . Status information may be provided by Position Sensor  536  if installed, indicating in an embodiment the degree to which the shaft of Motor  535  is extended, or in an alternate embodiment simply whether Valve Door  237  is open or closed. Status information may also be provided by Pressure Sensor  537  if installed, indicating the pressure, and by inference the remaining altitude potential, of lifting gas inside Tow Cell  210 . 
         [0068]      FIG. 6  provides multiple detailed views of Tactical Launch Apparatus  600 , with an overview of the major components and their primary features in  FIG. 6A . Launch Bag  610 , also shown in  FIG. 6B , is a tent-like structure of lightweight fabric in which Tow Cell  210  can be inflated as described in the Summary section above. Fastened to the ground via Ground Anchor  611  and Anchor Skirt  612 , and open along its length near the top, Launch Bag  610  can be spread out and Tow Cell  210  arranged inside. The lower edge of the top opening can then be aligned with the upper edge of the top opening, either directly abutting that edge or overlapping it some distance to close Launch Bag  610  at the diameter appropriate to the volume of lifting gas required for a particular mission. Both edges of the opening are lined with the pile side of hook-and-pile fastening material (commonly called Velcro). Size-Adjustment Fasteners  618  are strips of the same pile material affixed to Launch Bag  610  perpendicular to the upper edge of the top opening and spaced at regular intervals along the entire length of the top. Release Seam  619 , a strip of fabric made with the matching hook side of hook-and-pile fastening material, can then be laid along the joint to close it. 
         [0069]    Window Hoop  614 , a flexible and adjustable ring of plastic pipe, is socketed around the end of Launch Bag  610  where Anchor Skirt  612  joins the main body of the bag. When raised to a vertical position, Window Hoop  614  holds its end of Launch Bag  610  open to catch any wind and thereby inflate, forming a wind-neutral enclosure. The diameter of Window Hoop  614  is adjustable to accommodate the variable diameter of Launch Bag  610 . The end of Launch Bag  610  is covered with a mesh material through which air can flow to effect this inflation, forming Window Screen  615 . A hole in Window Screen  615  at roughly the center of the circular opening is Fill Tube Access  616 , through which Fill Tube  211  of Tow Cell  210  protrudes for access to its Diffuser Coupling  216 . As Tow Cell  210  fills with lifting gas, it displaces the air filling Launch Bag  610  out Window Screen  615 ; when no air is left to displace, Tow Cell  210  is full. 
         [0070]    During and after inflation, in order to prevent Launch Bag  610  from being lifted, it is weighted but not fastened to the ground except at Ground Anchor  611 , allowing it to be reoriented as the wind changes direction. The extra weight can be provided by Weight Tubes  613 , which are large plastic pipe sections in fabric sockets attached to both sides of Launch Bag  610 . Though not shown in the figure, if additional weight is necessary to survive a particular combination of wind speed and/or lifting gas volume, sandbags may be attached to weight tubes  613  as needed. The weight provided by weight tubes  613  need not be in the form of tubes. And need not be arranged as discussed above. For example, desired weight could be provided by using ballast pockets incorporated into the launch bag  610 , Such pockets, or areas of additional weight, could be positioned in any suitable location, such as, for example, above the Weight Tubes  613 . In addition, the weight tubes  613  need not be tubes, and need not be comprised of a relatively rigid material such as PVC, or wood or metal, or other material. They could be, for example, constructed of inflatable tubes, such as high pressure inflatable members, to allow the launch bag system to be stowed into a smaller volume, and assembled more quickly. 
         [0071]    Shown physically in  FIG. 6A  and schematically in  FIG. 6C  is the second component of Tactical Launch Apparatus  600 . Inflation Station  630  controls the flow of lifting gas during the filling of Tow Cell  210 . Inflation Station  630  consists of valves, gauges, and electronics packaged in a sturdy transit case. Lifting gas is introduced to the station via Supply Inlet  631 , and flows to Pressure Regulator  632 , a standard component well known to those skilled in the art that ensures excessive gas pressure from the Supply  130  to which it is attached does not damage components of Inflation Station  630  or Tow Cell  210 . Inside Regulator  632 , the supply line is teed over to Supply Pressure Gauge  633  for observation as appropriate by a system operator. The output of Regulator  632 , carrying lifting gas at a pressure suitable for the rest of Inflation Station  630 , is teed to two different valves. Shutoff Valve  634 , normally open during operation, allows the lifting gas flow to be blocked entirely to shut off the station. When Shutoff Valve  634  is closed, the path from Supply  130  to Shutoff Valve  634  may still be pressurized. To depressurize safely Bleed Valve  635 , normally closed during operation, can be opened to release the gas through Exhaust Muffler  636 , a baffled outlet that deflects and disperses the gas being released so as to reduce its force and noise. 
         [0072]    In normal operation with Bleed Valve  636  closed and Shutoff Valve  635  open, gas flows next into Solenoid Valve  637 , which is normally open but is driven shut electrically when fill feedback pressure is detected as described below. The output of Solenoid Valve  637  is teed to an Output Pressure Gauge  642  for observation by an operator as appropriate, and directed into Inflation Hose  640  by Diplexer  641 . Fill Hose  640  consists of two flexible tubes arranged coaxially. The outer hose carries lifting gas out of Inflation Station  630  into Tow Cell  210  at high pressure, while the inner hose carries a feedback flow at lower pressure from Tow Cell  210  to Inflation Station  630 . Diplexer  641  is a tee coupling, cut away in the figure to show detail, with the fill flow entering at the center and exiting at one branch into the outer tube of Hose  640 , while the other branch is sealed but penetrated by a small coupling to which the feedback tube of Hose  640  is attached. 
         [0073]    Fill flow is carried to Tow Cell  210  through Fill Hose  640 , to which is attached Diffuser  650 . Diffuser  650  is inserted into Fill Fitting  211  such that Diffuser Coupling  216  and Fill Fitting  651  mate and seal. Lifting gas flows through the holes in Output  652  of Diffuser  650 , filling Tow Cell  210 . As the cell expands and its pressure increases, a feedback flow enters the holes of Feedback Input  653  at the tip of Diffuser  653 , and is carried through the feedback tube of Hose  640  back to Inflation Station  630 . Diplexer  641  separates the feedback flow as previously described. The feedback flow is teed into a sensitive digital gauge, Balloon Pressure Gauge  643 , for monitoring by operators as appropriate, then fed into Pressure Switch  639 . When the pressure of feedback flow gas reaches a preset point corresponding with the cell having expanded to fill the set volume of Launch Bag  610 , Pressure Switch  639  trips and switches current from Battery  638  into Solenoid Valve  637  to close it and shut off the fill flow. 
         [0074]    A third component of Tactical Launch Apparatus  600  is Launch Cradle  620 . This sturdy rolling stand is tasked with supporting Payload Package  665 , which corresponds with PRV  300  in an embodiment, Packed Main Cell  220 , and Payload Package Adapter  240 . As shown in  FIG. 6A , Cradle  620  is positioned to allow formation of Intercell Tube  230  by the joining of Tow Cell Bottom Fitting  212  protruding from an access hole (not visible in the figure) and Main Cell Top Fitting  221  protruding from Packed Main Cell  220  in Deployment Bag  221 . During launch, Packed Main Cell  220  is lifted directly off its stand, and Launch Cradle  620  pivots to provide the optimum release angle for Payload Package  665 . 
         [0075]    The structure of Launch Cradle  620  is shown from two different angles in  FIGS. 6D and 6E . A strong Base  621  forms the platform on which the rest is built. In an embodiment, Handle  622  and Wheels  623  allow Launch Cradle  620  to be rolled into position like a wheelbarrow; an alternate embodiment may support motorized movement with additional wheels, or replace Wheels  623  with skids for use in snow or sand. Rising from Base  621  are Stanchions  624 , which support Payload Table  660 , and Packed Main Balloon Stand  625 , which supports Packed Main Cell  220  during setup and launch. The height of Stanchions  624  and Stand  625  can be adjusted using set pins in a fashion well known to those skilled in the art, in order to accommodate different diameters of Launch Bag  610 . Stand  625  can also be moved longitudinally along its Base  621  rail, in order to accommodate different heights of Packed Main Cell  220 . Payload Table  660  rests atop Stanchions  624 , attached by Payload Table Pivots  661  which allow rotation from vertical to horizontal. In an embodiment, Payload Table  660  is shaped to hold PRV  300  and release it cleanly without damaging edges or interfering with control surfaces; to allow removal and installation of Payload Access Panel  314 ; to allow unrestricted access to Payload Pod  420  and the interior of Fuselage  310 ; and to allow removal and installation of Nosecone  315 . In an alternate embodiment with a different Payload Package  665 , Payload Table  660  would be shaped differently according to the attributes of that payload. 
         [0076]      FIGS. 6D and 6E  also depict two primary modes of Launch Cradle  620 . The vertical position shown in  FIG. 6D  accommodates the launch position shown in  FIG. 6A , with Payload Table  660  rotated about its Pivots  661  such that its Vertical Stops  662  abut the Stanchions  624  that support it. Vertical Latches  663  can lock their respective Vertical Stops  662  in place and prevent rotation away from vertical; this safety feature is useful when moving loaded Launch Cradle  620  into position, and when storing it. The horizontal position shown in  FIG. 6E  accommodates pre-launch installation of Payload Package  665  onto Payload Table  660 . 
         [0077]    As previously described, Launch Cradle  620  pivots to support the optimum release angle during launch. Payload Table Pivots  661  permit free movement of Payload Package  665  on Payload Table  660  under the influence of wind and lift, within the constraints set by stops attached to Pivots  661 . Vertical Stops  662  keep Table  660  from turning completely over and dumping Payload Package  665  on the ground. Adjustable Off-Vertical Stops  664  can be set to limit rotation to any angle between vertical and horizontal according to the geometry of the payload and other factors such as wind speed. To allow rotation from vertical to the off-vertical limit set by Stops  664 , Vertical Latches  663  are released prior to launch. 
         [0078]    The functional architecture of Ground Station  700  is found in  FIG. 7 . Ground Station  700  provides common and application-specific telemetry, tracking, and control (TT&amp;C) capabilities to one or more system operations personnel. Ground Station  700  is implemented by computing and communications hardware accompanied by operational software. 
         [0079]    One or more Workstations  710  run the operational software and support interaction of personnel with the TT&amp;C functions. This software comprises three major components and two communication modules, which mirror the components of Flight Control System  500 . First, Aircraft Control module  720  manages Autopilot  520 , and is therefore tightly coupled with its design. Primary functions of Aircraft Control module  720  include Position Monitor  721 , which displays and records the position of PRV  300  as reported by Autopilot  520  (primarily useful during return flight); Telemetry Monitor  722 , which displays and records other telemetry that may be reported by Autopilot  520 , such as airspeed, temperature, flight control decisions, and others; and Commands  723 , which allow manual control of flight parameters. In an embodiment, use of the Cloud Cap Technology Piccolo as Autopilot  520  drives the use of its corresponding ground software package as Aircraft Control module  720 . An alternate embodiment with a different implementation of Autopilot  520  may include a corresponding different implementation of Aircraft Control module  720 . Next, Balloon Platform Control module  740  manages Balloon Platform C 3   540 , and is therefore tightly coupled with its design. The primary functions of Balloon Platform Control module  740  are similar to those of Aircraft Control module  720 , including Position Monitor  741 , which displays and records the position and altitude of Tactical Balloon  200  as reported by C 3   540  (primarily useful during ascent and float); Telemetry Monitor  742 , which displays and records other telemetry that may be reported by C 3   540 , such as payload state, valve state, power control state, and others; and Commands  743 , which allow manual control of such balloon features as main cell deployment, valve operation, ballast release, and PRV release. In an embodiment, Balloon Platform Control module  740  is implemented as a process control application built on National Instruments&#39; Labview package, essentially instrumenting each sensor and relay in C 3   540  individually. An alternate embodiment may implement module  740  using a different underlying package, including possibly integrating it with module  720 . 
         [0080]    Satellite Communication Driver  711  can be provided by the supplier of the hardware used for BLOS communication with PRV  300 , allowing Control modules  720  and  740  to access said hardware using standard APIs as well known to those skilled in the art. Line-of-Sight Communication Driver  712  can be provided by the supplier of the hardware used for LOS communication with PRV  300 , allowing Control modules  720  and  740  to access said hardware using standard APIs as well known to those skilled in the art. In an embodiment, both Drivers  711  and  712  are integrated with the Cloud Cap Technology Piccolo-based implementation of Control module  720  since it and Autopilot  520  control both communication paths. 
         [0081]    A third component of operational software in Workstation  710  is a Mission Planning module  730 . Parameters module  731  provides tools for selecting the diameter of Launch Bag  610  and the size of Main Cell  220  for a particular mission. Position Forecast module  732  combines current weather data and forecasts, aerodynamic models of Tactical Balloon  200  and PRV  300 , and knowledge of current position to predict future positions during ascent, float, and return flight. Module  732  can be used prior to launch for selection of launch location with respect to Area of Interest  140 , and both prior to launch and during all phases of flight to select the location of Landing Area  150 . Finally, Position Monitor  733  displays and records the current position of Tactical Balloon  200  and PRV  300 , as reported by C 3   540 , with respect to the original and updated forecasts from Position Forecast module  732 . In an embodiment, Mission Planning module  730  is implemented as a group of user interface and computation functions which display their data as an overlay on mission area maps in the well-known FalconView flight planner tool. An alternate embodiment may implement module  730  on a geographic information system (GIS) platform, and couple it more tightly with module  740 . 
         [0082]    BLOS and LOS communication links are served in Ground Station  700  by one or more copies of BLOS Terminal  751  and LOS Terminal  752 , respectively. In an embodiment, these devices are implemented by off-the-shelf Iridium modems and Cloud Cap Technology&#39;s 902 MHz ground station, respectively. To support continuous communication with multiple simultaneous flights of PRV  300  and Tactical Balloon  200 , one Iridium modem can be provided for each airborne PRV  300 . An alternate embodiment may use technology that supports multiple simultaneous connections or a different BLOS technology instead. In an embodiment, and generally in most alternate embodiments, devices of the type used as Terminals  751  and  752  connect to a host computer via standard and well-known RS-232 Serial Interfaces  755  and  756  respectively. In order to allow multiple Workstations  710  to connect with any of Terminals  751  and  752 , they are attached through a Terminal Server  750  instead. Terminal Server  750  translates Serial Interfaces  755  and  756  into packet streams carried via Internet Protocol (IP) according to techniques well-known to those skilled in the art. Network Link  765  connects Terminal Server  750  to Network Router  760  using standard and well-known Ethernet technology. Router  760  is in turn connected to Workstations  710  via Network Links  715 , also using Ethernet technology. The network thus formed allows any Workstation  710  to interact with any BLOS Terminal  751  or LOS Terminal  752  as necessary for redundancy or multiple access. 
         [0083]    The invention has been described above with reference to preferred embodiments and specific applications. It is not intended that the invention be limited to the specific embodiments and applications shown and described, but that the invention be limited in scope only by the claims appended hereto. It will be evident to those skilled in the art that various substitutions, modifications, and extensions may be made to the embodiments as well as to various technologies which are utilized in the embodiments. It will also be appreciated by those skilled in the art that such substitutions, modifications, and extensions fall within the spirit and scope of the invention, and it is intended that the invention as set forth in the claims appended hereto includes all such substitutions, modifications, and extensions.