System for tactical balloon launch and payload return

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.

TECHNICAL FIELD OF THE INVENTION

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

Balloon systems have been used for decades to carry atmospheric sensors, surveillance equipment, and communications gear to various altitudes. Substantial prior art is documented inThe Moby Dick Project: Reconnaissance Balloons Over Russiaby 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.

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.

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.

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.

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.

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'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.

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'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.

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'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.

An example PRV is a faceted lifting-body design derived from Barnaby Wainfan'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.

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.

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.

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.

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.

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.

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.

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.

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.

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's ascent and loiter, and the PRV'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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The high-level diagram ofFIG. 1shows components of an embodiment of the present invention and their relationships to one another in an example operational context. Tactical Balloon and Payload Return System100comprises primarily a lighter-than-air vehicle for low-energy lift to altitude, Tactical Balloon200; 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 Apparatus600; and a set of equipment that facilitates monitoring and controlling the flight items, Ground-Based Control Station700. Each of these components is detailed in subsequent paragraphs.

Three instances of Tactical Balloon200are shown, representing three distinct states of deployment. Tactical Balloon200-1is in the pre-launch configuration, coupled closely with the components of Launch Apparatus600. Gas Supply130, 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 Hose135to Launch Apparatus600, which is in turn inflating the tow cell of Tactical Balloon200-1; the main cell of Tactical Balloon200-1remains packed in this configuration. Tactical Balloon200-2is in the launch configuration, with the tow cell inflated and the main cell still packed. Finally, Tactical Balloon200-3is in the float configuration, with both tow and main cells inflated.

Similarly, five instances of PRV300are shown, corresponding with various stages of flight and depicting multiple styles of airframe that may be used. PRV300-1is attached to Balloon200-1and resting in the launch cradle portion of Launch Apparatus600prior to launch. PRV300-2is attached to Balloon200-2in the early stages of ascent. PRV300-3is attached to Balloon200-3and its payload is serving the mission over Area of Interest140. PRV300-4has been released from its Tactical Balloon200(not shown), and is in return flight toward Landing Area150, which may be near the point of launch or at some other designated location. Finally, PRV300-5has returned to Landing Area150and is shown about to touch down. In addition, two different styles of airframe are shown inFIG. 1, with PRVs300-1,300-3, and300-5depicted as lifting bodies, and PRVs300-2and300-4depicted as a high aspect ratio glider. Depiction of these particular styles in the figure does not constrain System100to 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.

Ground Station700communicates with PRVs300through both line-of-sight (LOS) and beyond-line-of-sight (BLOS) technologies. LOS Communication Links125provide connections with PRVs300that are in range of Ground Station700via LOS technology. Depending on the location of Ground Station700or the existence of multiple Ground Stations700, LOS Communication Links125may be used during pre-launch checkout of PRV300-1, and during landing of PRV300-5. BLOS communication, for the purpose of the present invention, is accomplished via Satellite Communication Network110. Network110is any satellite communication system that offers data communication between distant users. Ground Station700and PRVs300use BLOS Communication Links115to Network110for communicating with one another when outside the reach of Ground Station700via LOS Communication Links125. In an embodiment, Network110is the Iridium system; alternate embodiments may use other existing and emerging systems such as GlobalStar, MilStar, MUOS, and others.

Tactical Balloon200-2, the launch configuration, is shown inFIG. 2A. In this configuration, Tow Cell210has been inflated via Fill Tube215and capped. Tow Cell210may 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 Cell220is packed, and attached to Tow Cell210via Intercell Tube230. Payload Package Adapter240provides a fitted bridge between the shape of Packed Main Cell220and that of, in an embodiment, a PRV300. In alternate embodiments, Payload Package Adapter240may be shaped differently from that shown here so as to provide a fitted bridge to other types of PRV300airframe, or even other kinds of non-returning payload that may be carried by Tactical Balloon200. Additional detail on the foregoing elements is provided below.

Tactical Balloon200-3, the float configuration, is shown inFIG. 2B. In this configuration, Tow Cell210has reached its maximum volume due to reduced atmospheric pressure at very high altitude, and Main Cell220has not only been deployed but also inflated to near its maximum volume by the expanded lifting gas overflowing from Tow Cell210through Intercell Tube230. End Fitting225is now visible due to the deployment of Main Cell220. End Fitting225seals the bottom of the Main Cell220envelope, and provides a hard object against which to secure Payload Package Adapter240. As described in the summary, End Fitting225is the novel mechanism whereby the size of Main Cell220may be adjusted by an operator prior to launch: a mission altitude is chosen, the Main Cell220envelope is trimmed to a length corresponding to the volume of lifting gas required to achieve that altitude with the total weight of Tactical Balloon200, PRV300, and payload; then a small vent opening is cut near the bottom of the balloon and the remaining bottom material of Main Cell220is wrapped around End Fitting225and knotted to secure the envelope.

FIG. 2Cprovides extensive detail of the various tubes and fittings that form interfaces between the cells of Tactical Balloon200, and between those cells and other elements of System100. 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.

Starting at the top of Tactical Balloon200, Fill Tube215is attached to one end of Tow Cell210, and provides an opening through which lifting gas is introduced. The primary structure of Fill Tube215is provided by the hollow, cylindrical Tow Cell Top Fitting211. This element features wide grooves on its outer surface, to which the film of Tow Cell210can 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 Cell210; not shown is a version with only two grooves, which provides sufficient fastening space for a zero-pressure Tow Cell210. The outside end of Tow Cell Top Fitting211is capped with Mounting Plate217, which is in turn held in place by Band Clamp218. Mounting Plate217seals the opening and provides a surface for Diffuser Coupling216, which is attached through a hole in the center of Mounting Plate217. Diffuser Coupling216provides the hole though which the inflation mechanism is inserted to supply lifting gas to Tow Cell210. Not shown, but obviously required, is the cap that fits over and seals Diffuser Coupling216after inflation is complete.

Intercell Tube230actually comprises two fittings that are mounted separately in the two cells of Tactical Balloon200, and then joined prior to launch when the particular Tow Cell210and Main Cell220have been chosen for a particular mission. The first, Tow Cell Bottom Fitting212, mirrors Tow Cell Top Fitting211by providing two or three grooves for attaching a zero-pressure or super-pressure envelope. This end of Tow Cell210is capped by Membrane231, so that when Tow Cell210is being filled with lifting gas the envelope is sealed. The second, Main Cell Top Fitting221, similarly provides three grooves for attaching the large main envelope. A Valve Mounting Ring233is also attached to Main Cell Top Fitting221, providing an airtight, threaded receptacle into which Intercell Valve235may be installed if required for a particular mission.

When two envelopes are selected for a particular mission, after inflation and prior to launch Membrane231is 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 Fitting212with Main Cell Top Fitting221and attaching them firmly to one another with Band Clamp232. If the mission calls for multiple float altitudes, an Intercell Valve235is installed in Valve Mounting Ring233of the selected Main Cell220before puncturing Membrane231and connecting the two fittings.

Intercell Valve235is constructed to fit inside the cylinder of Intercell Tube230. The valve itself comprises a Seal Ring238, against which is seated a Valve Door237. Seal Ring238is threaded to mate with Valve Mounting Ring233, and features a compressible surface with which the hard edge of Valve Door237forms an airtight seal. Operation of Intercell Valve235is effected by Motor535, an inexpensive linear stepper motor that opens or closes Valve Door237in increments as directed by Controller534. Controller534is a circuit board containing a power relay such that power from Battery531is either blocked or provided to Motor535according to the commanded direction of movement. Controller534also contains a wireless Transceiver532attached to Antenna533, whereby commands are received from a platform controller in PRV300; more information on said platform controller is provided later in this specification. In addition to receiving commands, Controller534may also transmit sensor readings to the platform controller via Transceiver532. In an embodiment, these sensor readings include voltage measurements from a transducer that indicates the pressure in Tow Cell210, voltage measurements from a linear potentiometer that indicates the shaft position of Motor535, and binary signals from a contact switch that indicates closure of Valve Door237against Seal Ring238. 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 Mount236, is anchored in Seal Ring238forming a sturdy semi-conical structure to which Motor535, Controller534, and Battery531are attached.

At the other end of Tactical Balloon200, and completing the tour ofFIG. 2C, Main Cell End Fitting225is shown to be a spool-shaped item designed to be wrapped by the film from which the Main Cell220envelope is constructed. After sizing Main Cell220, the operator seals it by wrapping the end around the smooth center portion of Main Cell End Fitting225and knotting the remainder of the film. The flanges of End Fitting225provide support to the knot so that it does not unravel, and offer a hard anchor point to which the payload package is attached.

FIG. 2Dprovides detail of the packing and deployment mechanism used to launch Main Cell220. Prior to launch, the Main Cell220envelope is packed in Deployment Bag221. Main Cell Top Fitting221protrudes through an opening in the top of Deployment Bag221(not visible inFIG. 2Ddue to the bottom-up orientation shown) so that it may be attached to Tow Cell Bottom Fitting211as described above. Deployment Bag221is fastened to Main Cell Top Fitting221with four Straps224, of which only two are visible inFIG. 2D, so that Main Cell220doesn't deploy through that opening. Straps224are wrapped around to the bottom of Deployment Bag221and into Payload Package Adapter240. At the juncture of Straps224inside Payload Package Adapter240, Deployment Mechanism223connects Straps224to one another so as to fasten Payload Package Adapter240snugly against the opening and completely enclose the Main Cell220envelope inside Deployment Bag221. When commanded to release, Deployment Mechanism223lets go of Straps224, thereby allowing Main Cell220to unfurl from Deployment Bag221. To avoid the stress on Main Cell220of an uncontrolled descent and sudden stop by Payload Package Package Adapter240and its attached payload (a PRV300in an embodiment), a folded strap is tacked together by a rip stitch to form Deployment Brake222. This device slows the descent rate of PRV300and corresponding deployment rate of Main Cell220, thereby reducing the aforementioned stress and preventing failure of the Tactical Balloon200.

FIG. 3provides exterior detail of a Payload Return Vehicle300in multiple views. As previously described, PRV300is derived from the FacetMobile airframe, with custom features to support the goals of System100.

FIG. 3Ashows a perspective view of PRV300from the top. The vehicle features three main sections, Fuselage310, Starboard Wing320, and Port Wing330. Fuselage310further features a Vertical Stabilizer311and a Nosecone315, which figure prominently in later paragraphs. Wings320and330each feature Ailerons322and332, and Winglets325and335, all of which provide functionality that is well known to those skilled in the art. In addition to these fundamental structural attributes, a Pitot340is provided to support flight control in a fashion that is well known to those skilled in the art; Pitot340is attached in an embodiment to Starboard Wing320; that choice is essentially arbitrary, and an alternate embodiment could place Pitot340in any other feasible location. Also noted inFIG. 3Ais an exemplary payload peripheral, a Payload Antenna350that is partially embedded in Stabilizer311for support and aerodynamic cover. This is an example of payload accommodation flexibility as discussed above.

FIG. 3Bshows a front orthogonal view of PRV300. While no features are explicitly labeled here, the features labeled inFIG. 3Aare visible and recognizable to those skilled in the art.

FIG. 3Cshows a side orthogonal view of PRV300in a partially disassembled state. Primary features fromFIG. 3Aare 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 PRV300airframe, distinguishing Fuselage310from Wing320requires 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, PRV300also features a detachable Nosecone315to 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 ofFIG. 4. Nosecone315is shown here completely separated from the rest of Fuselage310. Payload Access Panel314, which is on the bottom of PRV300, is also visible inFIG. 3Cdetached from its installed location. Attached to Panel314is Speed Brake312, the third control surface of PRV300(the other two being Ailerons322and332as previously shown). Speed Brake312can be held flat against Panel314when maximum flight velocity is desired, or deployed downward at any angle needed by the flight control function to slow the airframe in flight. Landing Skid313, 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 PRV300implementation to use skids for landing rather than wheels or other devices; those may be used in an alternate embodiment as required.

FIG. 4provides interior detail of one preferred Payload Return Vehicle300in multiple views.

In the first view,FIG. 4A, Payload Access Panel314is removed from the underside of PRV300to show the aforementioned interior bay of Fuselage310. Landing Skids313, described previously, are clearly visible in this view. The dominant feature in this view is Payload Pod420, a case designed to transport electronic equipment while protecting it from rough handling. In an embodiment this Payload Pod420is 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.

Four structural protrusions integral to the interior of PRV300, labeled Payload Pod Mounts410, provide sturdy attachment points for Payload Pod420. The two Pod Mounts410on the right side of the figure have vertical Payload Pod Fasteners411, embedded bolts over which matching holes in Pod420are 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 Mounts410on 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 Pod420. Alternate embodiments using other case structures for Pod420may use other forms of attachment to Mounts410.

On either side of Pod420are Ballasters430. These devices carry ballast material that can be jettisoned as needed for Tactical Balloon200altitude adjustments and flights lasting more than twenty-four hours, as is well known to those skilled in the art. In an embodiment, each Ballaster430holds approximately five pounds of material; alternate embodiments may provide larger or smaller capacities, or more than two Ballasters430, depending on payload and mission requirements. Ballasters430are aligned inside Fuselage310by structural protrusions, labeled Ballaster Supports435in the figure. The Ballasters430may be located in other suitable locations, such as the Wings320&330.

In general, Pod420may carry electronic equipment that can be enabled and disabled by a controller in Nosecone315(not shown in this figure, but described in a later paragraph). Ballasters430are also controlled from Nosecone315. The interconnects required to support this control, and potentially others depending on the payload and mission, pass through the holes labeled Nosecone Wiring Access450. Equipment in Pod420may also interact with peripheral equipment positioned inside Starboard Wing320, Port Wing330, or the rear of Fuselage310. For example, as previously noted an embodiment features a payload antenna embedded in Stabilizer311. The interconnects between a payload and its peripherals may pass through the hole labeled Wing Wiring Access440, or through a similar hole on the opposite side that cannot be seen due to the angle of the drawing.

FIG. 4Bdepicts the structure of Nosecone315in its disassembled state, the components of which are an Avionics Tray460and an exterior Cowling316into which it fits. Avionics Tray460is a modular platform on which are mounted the flight control systems, also known to those skilled in the art as avionics, supporting both Tactical Balloon200and Payload Return Vehicle300. Major components mounted on Avionics Tray460include a Satellite Communications (SATCOM) Transceiver523, a Tactical Balloon C3Unit540, and an Autopilot550. A detailed description of these components and their peripherals is given below in the context ofFIG. 5. Interconnects between components mounted on Avionics Tray460and those mounted elsewhere in PRV300pass through the holes labeled Fuselage Wiring Access461, which align with the aforementioned Nosecone Wiring Access ports450. So that components may be tested and replaced as necessary, Avionics Tray460is designed to be easily removable from Cowling316, and in turn Nosecone315is designed to be easily removable from Fuselage310, using fasteners such as nylon screws or clips well known to those skilled in the art.

FIG. 4Cprovides detail of Ballaster430, which is shown with its release opening facing up but which would be inverted from the pictured orientation in flight. Ballast Container431is 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 Magnet432is a permanent magnet mounted adjacent to the opening at the top of the figure. It keeps the steel shot inside Ballast Container431by 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 Electromagnet433is also mounted adjacent the opening, but with an opposite polarity to the permanent Holding Magnet432. When energized by its controller, Release Electromagnet433cancels the magnetic field of Holding Magnet432, allowing steel shot to flow out of Ballast Container431under the influence of gravity. A controlled amount of ballast can thereby be released through carefully timed activation of Release Electromagnet433. Finally, Ballaster430is fastened to the interior of PRV300via screws through Mounting Bracket434.

A functional architecture of the control system that can be used in Tactical Balloon200and PRV300is found inFIG. 5. Flight Control System500is a complex conglomerate of modules designed to communicate with Ground Station700, manage the various states of Tactical Balloon200, and manage speed, heading, altitude, and stability of PRV300during 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.

One component of Flight Control System500is Return Vehicle Avionics520which, as shown physically inFIG. 4Bcomprises three primary modules. Aircraft Autopilot550provides the functions required to manage stable flight of PRV300. In an embodiment it is implemented by a Piccolo autopilot from Cloud Cap Technology, and encapsulates all the functions required to control PRV300flight 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.

Autopilot550features at its core a Control Computer551responsible 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 Computer551drives control surface Servomotors501, which are outside Avionics520but 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, Autopilot550also provides a piloted mode in which automatic flight can be overridden by an operator at Ground Station700if conditions demand. In addition to these core functions, Computer551interfaces with several essential functions which in an embodiment are shown as also being components of Autopilot550, but which in an alternate embodiment might be implemented external to Autopilot550.

First of these is Line-of-Sight Communications Transceiver552, which supports commanding, telemetry, and payload data flow between Autopilot550and Ground Station700via 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. Transceiver552accesses the air via a suitable Antenna521tuned 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 PRV300.

Next is an Attitude Sensor553, which detects changes in orientation that are processed by Control Computer551into 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 Transducer554connected to Pitot340and Static Tube503. 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 Computer551using well known techniques.

Autopilot550also incorporates in an embodiment, or interacts with in an alternate embodiment, a Global Positioning System (GPS) Receiver555that 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 Sensor553and Pressure Transducer554. This dual approach to position and velocity determination increases the probability of successful navigation. With respect to altitude determination it is essential in System100, because many implementations of Pressure Transducer554, 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 Balloon200, 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.

The second component of Avionics520is a Satellite Communications Transceiver523. For most of the flight duration of Tactical Balloon200and PRV300, Line-of-Sight Transceiver552is beyond the range of the corresponding transceiver in Ground System700. So that system operators may receive telemetry from the flight unit and send commands to it while so out of range, Satellite Communications Transceiver523provides 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 Antenna524. Antenna524is 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.

The third component of Avionics520is Balloon Platform C3540. This device is responsible for lighter-than-air flight management, payload supervision, and power management. At its core is Control Computer541, 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 Computer541is attached.

For valve control, C3540incorporates a Local Wireless Transceiver542and corresponding Antenna543. This is a low-power radio for transmitting simple commands and receiving simple indications. In an embodiment, Transceiver542is constructed of components commonly used for garage-door remote control devices operating at 315 MHz. Control Computer541is able to send valve operation commands via Transceiver542, and may receive indications of valve position and gas pressure through it.

For release management, C3540incorporates a set of Deployment Relays544, whereby high-current electrical power may be switched under control of Computer541. Individual connections are provided to Ballast Release Mechanism504, which corresponds to the Release Electromagnet433in each Ballaster430inFIG. 4; Main Balloon Deployment Mechanism505, which corresponds to Deployment Mechanism223inFIG. 2; and with Return Vehicle Release Mechanism506, which is attached inside PRV300to Payload Pod420, but not shown inFIG. 4due to its location on the side of Pod420that is obscured inFIG. 4A. Each of Release Mechanisms504,505, and506incorporates 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.

Payload supervision is designed into C3540so 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 Supervisor547cooperates with Payload Supervision Interface465adjacent to the payload in Pod420to accomplish these tasks. Payload Battery461and Payload Equipment462are connected to Supervisor Interface465, through a relay incorporated therein, instead of directly to one another. This allows Supervisor547to enable and disable power to Payload Equipment462using a signal on Power Control Connection561. Control and status lines on Payload Equipment462may likewise be connected through Supervisor Interface465and Signal Connection562to Supervisor547, and driven, interpreted, or simply communicated to an operator by Control Computer541as appropriate for the specific application.

Power management in C3540includes the payload power enablement function of Payload Supervisor547, as well as dedicated power conditioning circuits for specific devices within Avionics520that require them. In an embodiment, Autopilot550manages control surface Servos501by modulating power to them, and requires a specific voltage level that is different from its main supply. Servo Power Supply545produces 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 Transceiver523requires yet a different voltage level and supply condition, which is provided by SATCOM Power Supply546. In alternate embodiments with other implementations of any Avionics520component, alternate power supply modules may be included in C3540.

In an embodiment, LOS Transceiver552, SATCOM Transceiver523, and GPS Receiver555are connected, as shown in the figure, to Control Computer551of Autopilot550. Control Computer551decommutates incoming messages received on either Transceiver552or523but bound for Control Computer541of C3540, and duplicates position readings from GPS Receiver555, and sends them to C3540via the Connection525that joins them. C3540likewise sends outgoing messages to Autopilot520over Connection525for transmission. In an alternate embodiment, any of Transceivers552and523or GPS Receiver555may be connected directly to C3540instead, requiring it to provide access to them for Autopilot550via Connection525. In yet another alternate embodiment, any of Transceivers552and523or GPS Receiver555may also be duplicated and directly connected to both Control Computers551and541, removing the need for access via Connection525in either direction.

In an embodiment, electrical power for Avionics520can be provided by two sets of batteries sized to the duration of a particular mission. Autopilot Battery512powers Autopilot550and its modules, while C3Battery514powers C3540, 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.

Separate from Avionics520and connected to it only via a local wireless interface is Intercell Valve530, the functional architecture of which is shown here, and which corresponds to the Intercell Valve235depicted structurally inFIG. 2C. Since Avionics520is located inside PRV300, and Valve530is located at the other end of Main Cell220, Valve530includes its own Battery531to provide electrical power. Local Wireless Transceiver532and its antenna533are the mirror of Transceiver542and its Antenna543, receiving commands and sending status. Motor Controller534is the destination of any commands, operating Valve Motor535as directed to open and close Valve Door237. Status information may be provided by Position Sensor536if installed, indicating in an embodiment the degree to which the shaft of Motor535is extended, or in an alternate embodiment simply whether Valve Door237is open or closed. Status information may also be provided by Pressure Sensor537if installed, indicating the pressure, and by inference the remaining altitude potential, of lifting gas inside Tow Cell210.

FIG. 6provides multiple detailed views of Tactical Launch Apparatus600, with an overview of the major components and their primary features inFIG. 6A. Launch Bag610, also shown inFIG. 6B, is a tent-like structure of lightweight fabric in which Tow Cell210can be inflated as described in the Summary section above. Fastened to the ground via Ground Anchor611and Anchor Skirt612, and open along its length near the top, Launch Bag610can be spread out and Tow Cell210arranged 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 Bag610at 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 Fasteners618are strips of the same pile material affixed to Launch Bag610perpendicular to the upper edge of the top opening and spaced at regular intervals along the entire length of the top. Release Seam619, 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.

Window Hoop614, a flexible and adjustable ring of plastic pipe, is socketed around the end of Launch Bag610where Anchor Skirt612joins the main body of the bag. When raised to a vertical position, Window Hoop614holds its end of Launch Bag610open to catch any wind and thereby inflate, forming a wind-neutral enclosure. The diameter of Window Hoop614is adjustable to accommodate the variable diameter of Launch Bag610. The end of Launch Bag610is covered with a mesh material through which air can flow to effect this inflation, forming Window Screen615. A hole in Window Screen615at roughly the center of the circular opening is Fill Tube Access616, through which Fill Tube211of Tow Cell210protrudes for access to its Diffuser Coupling216. As Tow Cell210fills with lifting gas, it displaces the air filling Launch Bag610out Window Screen615; when no air is left to displace, Tow Cell210is full.

During and after inflation, in order to prevent Launch Bag610from being lifted, it is weighted but not fastened to the ground except at Ground Anchor611, allowing it to be reoriented as the wind changes direction. The extra weight can be provided by Weight Tubes613, which are large plastic pipe sections in fabric sockets attached to both sides of Launch Bag610. 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 tubes613as needed. The weight provided by weight tubes613need 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 bag610, Such pockets, or areas of additional weight, could be positioned in any suitable location, such as, for example, above the Weight Tubes613. In addition, the weight tubes613need 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.

Shown physically inFIG. 6Aand schematically inFIG. 6Cis the second component of Tactical Launch Apparatus600. Inflation Station630controls the flow of lifting gas during the filling of Tow Cell210. Inflation Station630consists of valves, gauges, and electronics packaged in a sturdy transit case. Lifting gas is introduced to the station via Supply Inlet631, and flows to Pressure Regulator632, a standard component well known to those skilled in the art that ensures excessive gas pressure from the Supply130to which it is attached does not damage components of Inflation Station630or Tow Cell210. Inside Regulator632, the supply line is teed over to Supply Pressure Gauge633for observation as appropriate by a system operator. The output of Regulator632, carrying lifting gas at a pressure suitable for the rest of Inflation Station630, is teed to two different valves. Shutoff Valve634, normally open during operation, allows the lifting gas flow to be blocked entirely to shut off the station. When Shutoff Valve634is closed, the path from Supply130to Shutoff Valve634may still be pressurized. To depressurize safely Bleed Valve635, normally closed during operation, can be opened to release the gas through Exhaust Muffler636, a baffled outlet that deflects and disperses the gas being released so as to reduce its force and noise.

In normal operation with Bleed Valve636closed and Shutoff Valve635open, gas flows next into Solenoid Valve637, which is normally open but is driven shut electrically when fill feedback pressure is detected as described below. The output of Solenoid Valve637is teed to an Output Pressure Gauge642for observation by an operator as appropriate, and directed into Inflation Hose640by Diplexer641. Fill Hose640consists of two flexible tubes arranged coaxially. The outer hose carries lifting gas out of Inflation Station630into Tow Cell210at high pressure, while the inner hose carries a feedback flow at lower pressure from Tow Cell210to Inflation Station630. Diplexer641is 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 Hose640, while the other branch is sealed but penetrated by a small coupling to which the feedback tube of Hose640is attached.

Fill flow is carried to Tow Cell210through Fill Hose640, to which is attached Diffuser650. Diffuser650is inserted into Fill Fitting211such that Diffuser Coupling216and Fill Fitting651mate and seal. Lifting gas flows through the holes in Output652of Diffuser650, filling Tow Cell210. As the cell expands and its pressure increases, a feedback flow enters the holes of Feedback Input653at the tip of Diffuser653, and is carried through the feedback tube of Hose640back to Inflation Station630. Diplexer641separates the feedback flow as previously described. The feedback flow is teed into a sensitive digital gauge, Balloon Pressure Gauge643, for monitoring by operators as appropriate, then fed into Pressure Switch639. When the pressure of feedback flow gas reaches a preset point corresponding with the cell having expanded to fill the set volume of Launch Bag610, Pressure Switch639trips and switches current from Battery638into Solenoid Valve637to close it and shut off the fill flow.

A third component of Tactical Launch Apparatus600is Launch Cradle620. This sturdy rolling stand is tasked with supporting Payload Package665, which corresponds with PRV300in an embodiment, Packed Main Cell220, and Payload Package Adapter240. As shown inFIG. 6A, Cradle620is positioned to allow formation of Intercell Tube230by the joining of Tow Cell Bottom Fitting212protruding from an access hole (not visible in the figure) and Main Cell Top Fitting221protruding from Packed Main Cell220in Deployment Bag221. During launch, Packed Main Cell220is lifted directly off its stand, and Launch Cradle620pivots to provide the optimum release angle for Payload Package665.

The structure of Launch Cradle620is shown from two different angles inFIGS. 6D and 6E. A strong Base621forms the platform on which the rest is built. In an embodiment, Handle622and Wheels623allow Launch Cradle620to be rolled into position like a wheelbarrow; an alternate embodiment may support motorized movement with additional wheels, or replace Wheels623with skids for use in snow or sand. Rising from Base621are Stanchions624, which support Payload Table660, and Packed Main Balloon Stand625, which supports Packed Main Cell220during setup and launch. The height of Stanchions624and Stand625can be adjusted using set pins in a fashion well known to those skilled in the art, in order to accommodate different diameters of Launch Bag610. Stand625can also be moved longitudinally along its Base621rail, in order to accommodate different heights of Packed Main Cell220. Payload Table660rests atop Stanchions624, attached by Payload Table Pivots661which allow rotation from vertical to horizontal. In an embodiment, Payload Table660is shaped to hold PRV300and release it cleanly without damaging edges or interfering with control surfaces; to allow removal and installation of Payload Access Panel314; to allow unrestricted access to Payload Pod420and the interior of Fuselage310; and to allow removal and installation of Nosecone315. In an alternate embodiment with a different Payload Package665, Payload Table660would be shaped differently according to the attributes of that payload.

FIGS. 6D and 6Ealso depict two primary modes of Launch Cradle620. The vertical position shown inFIG. 6Daccommodates the launch position shown inFIG. 6A, with Payload Table660rotated about its Pivots661such that its Vertical Stops662abut the Stanchions624that support it. Vertical Latches663can lock their respective Vertical Stops662in place and prevent rotation away from vertical; this safety feature is useful when moving loaded Launch Cradle620into position, and when storing it. The horizontal position shown inFIG. 6Eaccommodates pre-launch installation of Payload Package665onto Payload Table660.

As previously described, Launch Cradle620pivots to support the optimum release angle during launch. Payload Table Pivots661permit free movement of Payload Package665on Payload Table660under the influence of wind and lift, within the constraints set by stops attached to Pivots661. Vertical Stops662keep Table660from turning completely over and dumping Payload Package665on the ground. Adjustable Off-Vertical Stops664can 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 Stops664, Vertical Latches663are released prior to launch.

The functional architecture of Ground Station700is found inFIG. 7. Ground Station700provides common and application-specific telemetry, tracking, and control (TT&C) capabilities to one or more system operations personnel. Ground Station700is implemented by computing and communications hardware accompanied by operational software.

One or more Workstations710run the operational software and support interaction of personnel with the TT&C functions. This software comprises three major components and two communication modules, which mirror the components of Flight Control System500. First, Aircraft Control module720manages Autopilot520, and is therefore tightly coupled with its design. Primary functions of Aircraft Control module720include Position Monitor721, which displays and records the position of PRV300as reported by Autopilot520(primarily useful during return flight); Telemetry Monitor722, which displays and records other telemetry that may be reported by Autopilot520, such as airspeed, temperature, flight control decisions, and others; and Commands723, which allow manual control of flight parameters. In an embodiment, use of the Cloud Cap Technology Piccolo as Autopilot520drives the use of its corresponding ground software package as Aircraft Control module720. An alternate embodiment with a different implementation of Autopilot520may include a corresponding different implementation of Aircraft Control module720. Next, Balloon Platform Control module740manages Balloon Platform C3540, and is therefore tightly coupled with its design. The primary functions of Balloon Platform Control module740are similar to those of Aircraft Control module720, including Position Monitor741, which displays and records the position and altitude of Tactical Balloon200as reported by C3540(primarily useful during ascent and float); Telemetry Monitor742, which displays and records other telemetry that may be reported by C3540, such as payload state, valve state, power control state, and others; and Commands743, 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 module740is implemented as a process control application built on National Instruments' Labview package, essentially instrumenting each sensor and relay in C3540individually. An alternate embodiment may implement module740using a different underlying package, including possibly integrating it with module720.

Satellite Communication Driver711can be provided by the supplier of the hardware used for BLOS communication with PRV300, allowing Control modules720and740to access said hardware using standard APIs as well known to those skilled in the art. Line-of-Sight Communication Driver712can be provided by the supplier of the hardware used for LOS communication with PRV300, allowing Control modules720and740to access said hardware using standard APIs as well known to those skilled in the art. In an embodiment, both Drivers711and712are integrated with the Cloud Cap Technology Piccolo-based implementation of Control module720since it and Autopilot520control both communication paths.

A third component of operational software in Workstation710is a Mission Planning module730. Parameters module731provides tools for selecting the diameter of Launch Bag610and the size of Main Cell220for a particular mission. Position Forecast module732combines current weather data and forecasts, aerodynamic models of Tactical Balloon200and PRV300, and knowledge of current position to predict future positions during ascent, float, and return flight. Module732can be used prior to launch for selection of launch location with respect to Area of Interest140, and both prior to launch and during all phases of flight to select the location of Landing Area150. Finally, Position Monitor733displays and records the current position of Tactical Balloon200and PRV300, as reported by C3540, with respect to the original and updated forecasts from Position Forecast module732. In an embodiment, Mission Planning module730is 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 module730on a geographic information system (GIS) platform, and couple it more tightly with module740.

BLOS and LOS communication links are served in Ground Station700by one or more copies of BLOS Terminal751and LOS Terminal752, respectively. In an embodiment, these devices are implemented by off-the-shelf Iridium modems and Cloud Cap Technology's 902 MHz ground station, respectively. To support continuous communication with multiple simultaneous flights of PRV300and Tactical Balloon200, one Iridium modem can be provided for each airborne PRV300. 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 Terminals751and752connect to a host computer via standard and well-known RS-232 Serial Interfaces755and756respectively. In order to allow multiple Workstations710to connect with any of Terminals751and752, they are attached through a Terminal Server750instead. Terminal Server750translates Serial Interfaces755and756into packet streams carried via Internet Protocol (IP) according to techniques well-known to those skilled in the art. Network Link765connects Terminal Server750to Network Router760using standard and well-known Ethernet technology. Router760is in turn connected to Workstations710via Network Links715, also using Ethernet technology. The network thus formed allows any Workstation710to interact with any BLOS Terminal751or LOS Terminal752as necessary for redundancy or multiple access.

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.