WO2017095505A1

WO2017095505A1 - Aerostat tether with integrated hydrogen filling tube

Info

Publication number: WO2017095505A1
Application number: PCT/US2016/052643
Authority: WO
Inventors: Patrick J. Fitzgerald; Stephen D. NORDEL; Gary D. COLEMAN
Original assignee: Raytheon Company
Priority date: 2015-12-04
Filing date: 2016-09-20
Publication date: 2017-06-08

Abstract

An aerostat system including an aerostat and a tether. One end of the tether is attached to the aerostat and the other end of the tether is configured to be attached to ground handling equipment, such as a reel apparatus. The aerostat system also includes a secondary attachment loop on the tether. The secondary attachment loop is between the two ends of the tether. The second attachment point configured to facilitate transferring the tether from the ground handling equipment to a simple mooring point.

Description

AEROSTAT TETHER WITH INTEGRATED HYDROGEN FILLING TUBE

FIELD

[0001] The present disclosure relates generally to aerostats and, more particularly, to tethered aerostats.

BACKGROUND

[0002] Aerostats are lighter-than-air crafts (i.e. , dirigibles) that generate lift from a buoyant gas contained in one or more gasbags. Several different types of aerostats exist, including balloons and air ships. Additionally, aerostats may be either free- flying or tethered to the ground. Aerostats may be used for a variety of different purposes, including communications or surveillance operations with cameras and/or radar.

[0003] Conventional aerostats leak some of the buoyant gas over time. Accordingly, conventional aerostats have to be periodically serviced by lowering the aerostat, refilling the aerostat with buoyant gas, and then re-deploying (i.e. , raising) the aerostat. Such repeated servicing of the aerostat is both time-consuming and costly. Repeated servicing of the aerostat may also create significant downtime during which the aerostat is not being operated for its intended purpose. Repeated servicing of the aerostat also increases wear of the tether. Also, some conventional aerostats are oversized to accommodate for the leak rate of the buoyant gas and the time between refilling operations. However, oversizing the aerostat is both costly and space-inefficient, and may still require gas refilling operations for long-duration deployments. Oversizing the aerostat also fatigues the aerostat over time. Additionally, the additional gas that must be provided to compensate for the leak rate of the aerostat is inefficient because the additional gas does not increase the lifting or payload capacity of the aerostat.

[0004] Additionally, conventional tethered aerostats typically include ground handling equipment, such as a reel apparatus, slip rings, and/or rotating joints, which must remain attached to the tether during the entire deployment of the aerostat because conventional aerostats do not include a mechanism to eliminate tension on the tether, which would facilitate removal of the ground handling equipment. Keeping the ground handling equipment attached to the tether during the entire deployment of the aerostat is inefficient because the ground handling equipment is only needed during launch and recovery of the aerostat (i.e. , the ground handling equipment is not used during a vast majority of the aerostat deployment). Additionally, keeping the ground handling equipment attached to the tether during the entire deployment of the aerostat subjects the ground handling equipment to increased risk of damage, such as by inclement weather.

SUMMARY

[0005] The present disclosure is directed to various embodiments of an aerostat system. In one embodiment, the aerostat system includes an aerostat, a tether having a first end coupled to the aerostat and a second end opposite the first end configured to be coupled to ground handling equipment, and a secondary attachment loop on the tether. The secondary attachment loop is between the first and second ends of the tether and is configured to facilitate transferring the tether from the ground handling equipment to a simple mooring point. The tether may include an outer sleeve, and the secondary attachment loop may be integral with the outer sleeve. The outer sleeve and the secondary attachment loop may each include woven fibers. The secondary attachment loop may be detachable from the tether. The aerostat system may also include a bead coupled to the tether. The bead is configured to retain the secondary attachment loop on the tether. The aerostat system may further include a bullet assembly configured to be coupled to the tether and engage the bead, a lock ring configured to engage the bullet assembly, and an outer housing assembly configured to engage the lock ring. The secondary attachment loop may be coupled to the outer housing. The tether may also include a feedtube for supplying a lifting gas to the aerostat. The tether may further include a series of cables configured to supply power and control signals to the aerostat. The aerostat system may also include a service line having a first end configured to be coupled to the secondary attachment loop and a second end configured to be coupled to the simple mooring point. The ground handling equipment may include a reel configured to retract the tether.

[0006] The present disclosure is also directed to various embodiments of a tether for an aerostat system. In one embodiment, the tether include an outer sleeve having a first end configured to be coupled to an aerostat and a second end opposite the first end configured to be coupled to ground handling equipment, and a secondary attachment loop coupled to the outer sleeve between the first and second ends. The secondary attachment loop may be integral with the outer sleeve. The outer sleeve and the secondary attachment loop may each include woven fibers. The secondary attachment loop may be detachable from the outer sleeve. The tether may include a bead coupled to the outer sleeve, a bullet assembly configured to be coupled to the outer sleeve and engage the bead, a lock ring configured to engage the bullet assembly, and an outer housing assembly configured to engage the lock ring. The secondary attachment loop may be coupled to the outer housing. The tether may also include a feedtube housed in the outer sleeve and configured to supply lifting gas to the aerostat.

[0007] The present disclosure is also directed to various methods of transferring an aerostat system from ground handling equipment to a simple mooring point. In one embodiment, the method includes attaching a first end of a service line to a secondary attachment loop on a tether, tensioning the service line until tension on a second end of the tether is removed, disconnecting the second end of the tether from the ground handling equipment, and attaching the second end of the tether to the simple mooring point. The method may also include extending the service line until the tension is reapplied to the second end of the tether and disconnecting the first end of the service line from the secondary attachment loop. The method may also include coupling the second end of the tether to a gas supply for supplying a lifting gas and supplying the lifting gas through the tether to the aerostat. The lifting gas may be any suitable lifting gas, such as hydrogen.

[0008] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features and advantages of embodiments of the present disclosure will become more apparent by reference to the following detailed description when considered in conjunction with the following drawings. In the drawings, like reference numerals are used throughout the figures to reference like features and components. The figures are not necessarily drawn to scale.

[0010] FIG. 1A is perspective view of a schematic representation of an aerostat system according to one embodiment of the present disclosure;

[0011] FIG. 1 B is a cross-sectional view of a tether of the embodiment of the aerostat system illustrated in FIG. 1A;

[0012] FIGS. 1 C-1 D are detail views of a secondary attachment point on the tether of the embodiment of the aerostat system illustrated in FIG. 1 A;

[0013] FIGS. 2A-2D are a perspective view, an exploded perspective view, a top view, and a cross-sectional view, respectively, of a secondary attachment point on the tether according to another embodiment of the present disclosure; and

[0014] FIG. 3 is a flowchart illustrating steps of operating an aerostat system according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0015] The present disclosure is directed to various embodiments of aerostat systems having an aerostat and a tether connecting the aerostat to ground handling equipment, such as a reel apparatus (e.g., a spool), slips rings, and/or rotating joints. The tether includes a secondary attachment loop which facilitates detaching the tether from the ground handling equipment after deployment of the aerostat and attaching the tether to a simple mooring point. Detaching the tether from the ground handling equipment enables the ground handling equipment to be utilized for other aerostat deployments and also mitigates the risk that the ground handling equipment could become damaged (e.g., due to inclement weather) if the equipment remained attached to the tether during the entire deployment of the aerostat. Embodiments of the tether of the present disclosure may also include an integrated feedtube for continuously delivering a lifting gas to the aerostat to compensate for the leak rate of the lifting gas out of the aerostat. Continuously delivering the lifting gas to the aerostat eliminates the costs associated with periodically lowering the aerostat to refill the aerostat with lifting gas.

[0016] With reference now to FIG. 1A, an aerostat system 100 according to one embodiment of the present disclosure includes an aerostat 101 and a tether 102. In the illustrated embodiment, the aerostat 101 includes a hull 103, a stabilizing tail 104 (e.g., one or more fins) coupled to a rear end of the hull 103, and a pair of ballonets 105 coupled to opposite sides of the hull 103. In one or more embodiments, the aerostat 101 may have any other suitable number of ballonets 105. The hull 103 includes an outer skin 106 filled with a lifting gas, such as helium or hydrogen, to provide the buoyancy of the aerostat 101 in the air. An upper end 107 of the tether 102 is coupled to the aerostat 101 and a lower end 108 of the tether 102 is coupled to ground handling equipment 109. In one embodiment, the ground handling equipment 109 includes a reel apparatus (e.g., a spool), slips rings, rotating joints, and a deployment trailer. The ground handling equipment 109 may also include a power supply for powering various systems, equipment, and/or instruments on the aerostat 101 , a lifting gas supply source, and a control system for controlling the various systems, equipment, and/or instruments on the aerostat 101. The reel apparatus is configured to extend the tether 102 to deploy the aerostat 101 and to rewind the tether 102 to lower the aerostat 101 (e.g., at the end of the deployment operation of the aerostat 101 ). The aerostat system 101 may also include a plurality of auxiliary lines 110 detachably coupled to a nose of the hull 103 when the aerostat 101 is grounded (i.e., the auxiliary lines 110 are configured to secure the aerostat 101 to the ground before deployment of the aerostat 101 ). [0017] The ballonets 105 are configured to expand and contract to supply and remove, respectively, a volume of lifting gas from the hull 103 of the aerostat 101. In one or more embodiments, the ballonets 105 may be configured to displace a volume of lifting gas into or out of the hull 103 of the aerostat 101. The ballonets 105 are configured to compensate for the volumetric expansion and contraction of the lifting gas in the aerostat 101 due to the diurnal cycle of the sun. During the day, the lifting gas inside the aerostat 101 expands and increases the internal pressure on the outer skin 106 of the aerostat 101. Accordingly, a volume of the lifting gas may be transferred into the ballonets 105 to prevent rupture of the skin 106 of the aerostat 101. During the night, the lifting gas inside the aerostat 101 contracts and reduces the internal pressure acting on the skin 106 of the aerostat 101. Accordingly, the volume of the lifting gas that was transferred into the ballonets 105 may be reintroduced into the hull 103 of the aerostat 101 to maintain the aerostat 101 in a rigid, inflated state with proper displacement for buoyancy. Otherwise, the contraction of the lifting gas inside the aerostat 101 would tend to cause the skin 106 of the aerostat 101 to buckle (e.g., rippling in the skin 106 of the aerostat 101 ), which could cause the aerostat 101 to become aerodynamically unstable. The ballonets 105 are also configured to expand and contract to compensate for atmospheric pressure variance with altitude. That is, the ballonets 105 are configured to compensate for the variance in the pressure differential across the outer skin 106 of the aerostat 101 (i.e., the pressure differential between the atmospheric pressure and the internal pressure of the lifting gas inside the aerostat 101 ) as the aerostat 101 ascends or descends.

[0018] With reference now to the embodiment illustrated in FIG. 1 B, the tether 102 includes an outer sleeve 111. The outer sleeve 111 may be made out of any suitably strong and durable material, such as, for instance, woven synthetic fibers. Additionally, in one embodiment, the outer sleeve 111 may be made out of an electrically conductive material such that the tether 102 provides a current return path in the event of a lightning strike of the aerostat 101. In the illustrated embodiment, the tether 102 also includes a structural jacket 112 housed inside the outer sleeve 111. In the illustrated embodiment, the outer sleeve 111 and the structural jacket 112 are cylindrical and coaxial. In the illustrated embodiment, the tether 102 also includes a feedtube 113 housed in the outer sleeve 111 and the structural jacket 112. The feedtube 113 is configured to deliver a lifting gas to the aerostat 101 to maintain the aerostat 101 aloft in the air. In one embodiment, the lifting gas may be supplied to aerostat at such a rate to compensate for the rate at which lifting gas is leaked from the aerostat 101. Accordingly, the aerostat 101 may remain filled with the lifting gas without having to periodically lower the aerostat 101 to resupply the aerostat 101 with the lifting gas. Additionally, because the feedtube 113 is configured to continuously supply lifting gas to the aerostat 101 , the aerostat 101 does not have to be oversupplied with lifting gas at the time of deployment to compensate for the leak rate of the lifting gas and the duration of the aerostat deployment. Further, because the aerostat 101 does not need to be oversized, the entire lifting capacity of the lifting gas contributes to the useful lifting capacity of the aerostat 101. The lifting gas may be any suitable type of gas for maintaining the buoyancy of the aerostat 101 , such as, for instance hydrogen or helium.

[0019] Additionally, denser gases in the atmosphere (i.e., gases denser than the lifting gas) may tend to leak through joints or seams in the outer skin 106 of the aerostat 101 , thereby reducing the buoyancy of the aerostat 101. In one embodiment, these denser gases that leak into the aerostat 101 may be vented from a lower end of the aerostat 101. Accordingly, in one embodiment, the tether 102 may be provided without a return line for removing denser gases from the aerostat 101. Thus, in one embodiment, the lifting gas may be supplied unidirectionally to the aerostat 101 (i.e., in a direction from the lifting gas supply on the ground equipment 109 to the aerostat 101 ). In one or more alternate embodiments, the tether 102 may be provided with a return line for removing denser gases from the aerostat 101 that have leaked from the atmosphere through the outer skin 106 of the aerostat 101.

[0020] In the embodiment illustrated in FIG. 1 B, the tether 102 also includes one or more power supply lines 114 for delivering power to the aerostat 101 , ground and return lines 115, 116, respectively, and a plurality of fiber optic lines 117 for transmitting signals to and/or receiving signals from the aerostat 101 (e.g., control signals to various equipment or instruments on the aerostat 101 , such as, for instance, communications equipment and/or a radar system).

[0021] Additionally, in the embodiment illustrated in FIG. 1A, the tether 102 includes a bifurcation or confluence point 118 at which the tether 102 branches into a plurality of smaller lines 119 coupled to the outer skin 106 of the aerostat 101. The smaller lines 119 are configured to distribute the tensile load on the tether 102 across several attachment points on the outer skin 106 of the aerostat 101. In one or more embodiments, the tether 102 may not bifurcate into a plurality of smaller lines.

[0022] With reference now to the embodiment illustrated in FIGS. 1 C-1 D, the aerostat system 100 also includes a secondary attachment loop 120 on the tether 102. As described in more detail below, the secondary attachment loop 120 is configured to facilitate detaching the tether 102 from the ground handling equipment 109 and subsequently coupling the lower end 108 of the tether 102 to a simple mooring point 121 (see FIG. 1A). The secondary attachment loop 120 may be located at any suitable intermediate position between the upper and lower ends 107, 108 of the tether 102, such as, for instance, from approximately 10 feet to approximately 40 feet along the tether 102 from the lower end 108 of the tether 102 that is coupled to the ground handling equipment 109. In the embodiment illustrated in FIGS. 1 C-1 D, the secondary attachment loop 120 is a flexible loop (e.g., a deadeye) of woven synthetic fibers integrally formed with the woven synthetic fibers of the outer sleeve 111 of the tether 102. In one embodiment, the secondary attachment loop 120 may include a metal liner (e.g., a steel liner) underneath the woven synthetic fibers. Additionally, in the illustrated embodiment, ends 122, 123 of the secondary attachment loop 120 are wound around at least a portion of the tether 102 (e.g., the secondary attachment loop 120 is split and wound around at least a portion of the tether 102). Accordingly, when a tensile load is applied to the secondary attachment loop 120, the ends 122, 123 of the secondary attachment loop 120 are drawn (e.g., clamped) against the outer sleeve 111 of the tether 102. In one embodiment, the clamping force between the ends 122, 123 of the secondary attachment loop 120 and the tether 102 increases as the tensile force on the secondary attachment loop 120 increases. In another embodiment, the secondary attachment loop 120 may include a rigid ring (e.g., a D-ring) or hook (e.g., a J- shaped hook) coupled to the tether. The ring or hook may be coupled to the tether by any suitable manufacturing technique or process, such as, for instance, bonding, adhering, or mechanical fastening. For instance, in one embodiment, the ring or hook may be woven into the fibers of the outer sleeve 111. In one embodiment, the secondary attachment loop 120 may be a rope braided onto the tether 102, such as, for instance, a YaleGrip TM offered by Yale Cordage, Inc. Accordingly, the secondary attachment loop 120 on the tether 102 may be either rigid or flexible and may be either integrally formed with the tether 102 or formed separately from tether 102 and subsequently coupled to the tether 102. The secondary attachment loop 120 may have any suitable size, depending, for instance, on the type and size of the equipment used to engage the secondary attachment loop 120 and/or the loads the secondary attachment loop 120 is designed to withstand.

[0023] With reference now to the embodiment illustrated in FIGS. 2A-2D, the aerostat system 100 may include a secondary attachment assembly 200 rather than the secondary attachment loop 120 illustrated in FIGS. 1 C and 1 D. In the embodiment illustrated embodiment in FIGS. 2A-2D, the secondary attachment assembly 200 includes a bead 201 on the tether 102, a bullet assembly 202 configured to engage the bead 201 , a lock ring or collar 203 configured to engage the bullet assembly 202, an outer housing assembly 204 configured to engage the lock ring 203, and a secondary attachment loop 205 coupled to the outer housing assembly 204. As described in more detail below, the secondary attachment loop 205 is configured to facilitate detaching the tether 102 from the ground handling equipment 109 (e.g. a reel apparatus, slips rings, rotating joints, and a deployment trailer) and subsequently coupling the lower end 108 of the tether 102 to the simple mooring point 121.

[0024] In the embodiment illustrated in FIGS. 2A-2D, the bead 201 is an annular member (e.g., a toroid shape) having an outer diameter D_B larger than an outer diameter of the tether D_T. In one or more embodiments, the bead 201 may have any other suitable shape. In one embodiment, the bead 201 may be integrally formed with the outer sleeve 111 of the tether 102 (e.g., the bead 201 may be a ring woven into the synthetic fibers of the outer sleeve 111 ). The bead 201 may be made out of any suitable strong and durable material, such as, for instance, metal (e.g., aluminum or steel). In one or more alternate embodiments, the bead 201 may be formed separately from the tether 102 and coupled to the tether 102 by any suitable manufacturing process or technique, such as, for instance, bonding, adhering, or mechanical fastening. The bead 201 is fixedly attached to the tether 102 at an intermediate position between the two ends 107, 108 (see FIG. 1A) of the tether 102, such as, for instance, from approximately 10 feet to approximately 40 feet along the tether 102 from the lower end 108 of the tether 102 that is coupled to the ground handling equipment 109.

[0025] Still referring to the embodiment illustrated in FIGS. 2A-2D, the bullet assembly 202 includes a first shell half 206 and a second shell half 207 configured to be detachably coupled to the first shell half 206. In the illustrated embodiment, each shell half 206, 207 includes a tapered semi-tubular segment 208 having an upper end 209 and a lower end 210, and a larger semi-tubular segment 211 coupled to the lower end 210 of the tapered semi-tubular segment 208. In the illustrated embodiment, the upper end 209 of the tapered semi-tubular segment 208 is narrower than the lower end 210 of the tapered semi-tubular segment 208 such that an outer sidewall 212 of the tapered semi-tubular segment 208 tapers between the narrower upper end 209 and the wider lower end 210. The outer sidewall 212 of the tapered semi-tubular segment 208 may taper at any suitable angle a relative to a longitudinal axes L (see FIG. 2A) of the shell half 206, 207, such as, for instance, from approximately 1 degree to approximately 10 degrees. In the illustrated embodiment, an outer sidewall 213 of the larger semi-tubular segment 211 extends between an upper end 214 and a lower end 215. Additionally, in the illustrated embodiment, the upper end 214 of the larger semi-tubular segment 211 is rounded. A shoulder 216 is defined between the rounded upper end 214 of the outer sidewall 213 of the larger semi-tubular segment 211 and the lower end 210 of the outer sidewall 212 of the tapered semi-tubular segment 208. When the first and second shell halves 206, 207 are coupled together, the tapered semi-tubular segments 208 cooperate to form a frusto-conical portion 217 (see FIG. 2D) of the bullet assembly 202 and the larger semi-tubular segments 211 cooperate to form a cylindrical portion 218 (see FIG. 2D) of the bullet assembly 202. The outer sidewall 212 is on the frusto-conical portion 217 and the outer sidewall 213 is on the cylindrical portion 218 of the bullet assembly 202.

[0026] The shell halves 206, 207 each also include an inner sidewall 219 opposite the outer sidewalls 212, 213 of the tapered semi-tubular segment 208 and the larger semi-tubular segment 211 , respectively. When the first and second halves 206, 207 are coupled together, the inner sidewalls 219 cooperate to define a central opening 220 (see FIG. 2D) (e.g., a cylindrical through hole) extending along the longitudinal axis L of the bullet assembly 202 between the upper end 209 and the lower end 215. The central opening 220 is configured to receive a portion of the tether 102. In one embodiment, the central opening 220 has the same or substantially the same size and shape as the outer sleeve 111 of the tether 102 (e.g., the central opening 220 may have the same or substantially the same diameter as the outer diameter D_T of the tether 102). In one or more embodiments, the central opening 220 may be slightly larger than the tether 102, but smaller than the outer diameter D_B of the bead 201.

[0027] In the embodiment illustrated in FIGS. 2A-2D, the first and second shell halves 206, 207 each also define an arcuate notch or shoulder 221 extending into the inner sidewall 219 and a lower surface 222. When the first and second shell halves 206, 207 are coupled together, the arcuate shoulders 221 cooperate to define an annular recess 223 concentric with the central opening 220. The annular recess 223 is configured to engage a portion of the bead 201 on the tether 102 when the bullet assembly 202 is coupled to the tether 102. In the illustrated embodiment, the annular recess 223 has the same or substantially the same size and shape as a portion of the bead 201 on the tether 102.

[0028] Although in the illustrated embodiment the bullet assembly 202 includes two shell halves 206, 207, in one or more alternate embodiments the bullet assembly 202 may include any other suitable number or parts (e.g., the bullet assembly 202 may include three parts configured to be coupled together around the tether 102). Additionally, in one embodiment, the first and second halves 206, 207may be hingedly coupled together. The two halves 206, 207 of the bullet assembly 202 facilitate attaching and removing the bullet assembly 202 from the tether 102 while the tether 102 is attached to the aerostat 101 (i.e., the two shell halves 206, 207 facilitate attaching and removing the bullet assembly 202 from the tether 102 without having to disconnect the tether 102 from the aerostat 101 ).

[0029] In the illustrated embodiment, each shell half 206, 207 also includes first and second engagement surfaces 224, 225. The first and second engagement surfaces 224, 225 of the first shell half 206 are configured to contact or abut the first and second engagement surfaces 224, 225, respectively, of the second shell half 207 when the first and second shell halves 206, 207 are coupled together. Each shell half 206, 207 also defines at least one alignment opening 226 (e.g., a blind bore) in each of the engagement surfaces 224, 225. In the illustrated embodiment, the alignment openings 226 in the shell halves 206, 207 extend into the engagement surfaces 224, 225 in a direction transverse to the longitudinal axis L of the bullet assembly 202. The alignment openings 226 in the shell halves 206, 207 are configured to receive locating pins 227 (see FIG. 2B) configured to ensure proper alignment between the shell halves 206, 207 when the shell halves 206, 207 are coupled together.

[0030] With continued reference to the embodiment illustrated in FIGS. 2A-2D, the lock ring 203 of the secondary attachment assembly 200 is an annular member halving a first semi-annular part 228 and a second semi-annular part 229 configured to be detachably coupled to the first semi-annular part 228. In the illustrated embodiment, the first and second semi-annular parts 228, 229 each include an upper surface 230, a lower surface 231 opposite the upper surface 230, an outer surface 232, and an inner surface 233 opposite the outer surface 232. Each semi- annular part 228, 229 also includes a pair of engagement surfaces 234, 235 extending between the upper surface 230, the outer surface 232, and the inner surface 233. The engagement surfaces 234, 235 on one of the semi-annular parts

228 are configured to abut the corresponding engagement surfaces 234, 235, respectively, on the other semi-annular part 229 when the semi-annular parts 228,

229 are coupled together. In the illustrated embodiment, each of the first and second semi-annular parts 228, 229 also defines an arcuate notch or shoulder 236 extending into the lower surface 231 and the inner surface 232. When the first and second semi-annular parts 228, 229 of the lock ring 203 are coupled together, the inner surfaces 232 cooperate to define a central opening 237 (see FIG. 2D) (e.g., a hole extending between the upper and lower surfaces 230, 231 ) and the arcuate shoulders 236 cooperate to define an annular recess 238 concentric with the central opening 237. The annular recess 238 defined in the lock ring 203 is configured to receive at least a portion of the shoulders 216 defined in the shell halves 206, 207 of the bullet assembly 202. In one embodiment, the annular recess 238 defined in the lock ring 203 may have the same or substantially the same size and shape as the portions of the shoulders 216 the annular recess 238 is configured to receive (e.g., the annular recess 238 defined in the lock ring 203 may conform or substantially conform to at least a portion of the shoulders 216 on the bullet assembly 202). Although in the illustrated embodiment the annular recess 238 in the lock ring 203 and the shoulders 216 defined in the shell halves 206, 207 of the bullet assembly 202 are curved (e.g., rounded), in one or more embodiments, annular recess 238 in the lock ring 203 and the shoulders 216 defined in the shell halves 206, 207 of the bullet assembly 202 may have any other suitable shape, such as, for instance, beveled or chamfered edges. In the illustrated embodiment, the central opening 237 in the lock ring 203 has a diameter D_L that is equal or substantially equal to a maximum diameter D_c of the frusto-conical portion 217 of the bullet assembly 202 such the inner surfaces 233 of the lock ring 203 engage the outer sidewalls 212 of the tapered semi-tubular segments 208 of the bullet assembly 202 when the lock ring 203 is installed around the bullet assembly 202, as described in more detail below. In one embodiment, the central opening 237 of the lock ring 203 may be tapered to match or substantially match the taper of the frusto-conical portion 217 of the bullet assembly 202. Additionally, in the illustrated embodiment, each semi- annular part 228, 229 also defines a pair of openings 239, 240 configured to receive fasteners 241 (e.g., bolts) coupling the first and second semi-annular parts 228, 229 together. In one embodiment, the openings 240 in one of the semi-annular parts 229 may be through holes extending through the outer surface 232 and the engagement surfaces 234, 235 and the corresponding openings 239 in the other semi-annular part 228 may be internally threaded blind bores in the engagement surfaces 234, 235. In one or more embodiments, the openings 239, 240 in both semi-annular parts 228, 229 may be through holes extending through the outer surfaces 232 and the engagement surfaces 234, 235. The fasteners 241 may extend through the through holes and be secured to the semi-annular parts 228, 229 with nuts.

[0031] Still referring to the embodiment illustrated in FIGS. 2A-2D, the outer housing assembly 204 includes a first case half 242 and a second case half 243 configured to be detachably coupled to the first case half 242. Each case half 242, 243 is a semi-cylindrical member including an upper surface 244, a lower surface 245, an outer sidewall 246 extending between the upper and lower surfaces 244, 245, and an inner sidewall 247 opposite the outer sidewall 246. Each case half 242, 243 also includes an upper flange 248 (see FIG. 2D) extending circumferentially around an upper end 249 of the case half 242, 243 and a lower flange 250 extending circumferentially around a lower end 251 of the case half 242, 243. The upper and lower flanges 248, 250 project radially inward from the inner sidewall 247. In the illustrated embodiment, the upper and lower flanges 248, 250 each include a semi- cylindrical inner sidewall 252, 253, respectively. A recess 254 is defined in both of the case halves 242, 243 between the upper and lower flanges 248, 250. Accordingly, in the illustrated embodiment, each of the case halves 242, 243 has a C-shaped cross-section. Additionally, an upper shoulder 255 is defined between the inner sidewall 247 and the upper flange 248 and a lower shoulder 256 is defined between the inner sidewall 247 and the lower flange 250. When the first and second case halves 242, 243 are coupled together, the inner sidewalls 252 of the upper flanges 248 cooperate to define an upper opening 257 and the inner sidewalls 253 of the lower flanges 250 cooperate to define a lower opening 258. Additionally, when the first and second case halves 242, 243 are coupled together, the recesses 254 cooperate to define a cavity 259 (e.g., a cylindrical cavity) configured to house the lock ring 203 and at least a portion of the bullet assembly 202. The upper and lower openings 257, 258 open up into the cavity 259.

[0032] In the illustrated embodiment, each case half 242, 243 also includes first and second engagement surfaces 260, 261. The first and second engagement surfaces 260, 261 of the first case half 242 are configured to contact or abut the first and second engagement surfaces 260, 261 , respectively, of the second case half 243 when the first and second case halves 242, 243 are coupled together. Additionally, in the illustrated embodiment, each case half 242, 243 also defines four openings 262, 263 configured to receive fasteners 264 (e.g., bolts) coupling the first and second case halves 242, 243 together. In one embodiment, the openings 263 in one of the case halves 243 may be through holes extending through the outer sidewall 246 and the engagement surfaces 260, 261 and the corresponding openings 262 in the other case half 242 may be internally threaded blind bores in the engagement surfaces 260, 261. In one or more embodiments, the openings 262, 263 in both of the case halves 242, 243 may be through holes extending through the outer sidewalls 246 and the engagement surfaces 260, 261. The fasteners 264 may extend through the through holes and be secured to the case halves 242, 243 with nuts.

[0033] With continued reference to the embodiment illustrated in FIGS. 2A-2D, the outer housing assembly 204 also includes an anchor 265 extending outward from the outer sidewall 246 of each of the case halves 242, 243. In the illustrated embodiment, the anchors 265 are cylindrical members (e.g., cylindrical lugs), although in one or more embodiments, the anchors 265 may have any other suitable shape. The anchors 265 are configured to support opposite ends 266, 267 of the secondary attachment loop 205. The anchors 265 may be coupled to the case halves 242, 243 by any suitable mechanism. For instance, in one embodiment, the anchors 265 may be detachably coupled to the case halves 242, 243. In the illustrated embodiment, the anchors 265 each include an externally threaded portion 268 that is threadedly coupled to an internally threaded blind bores 269 extending inward from the outer sidewalls 246 of the case halves 242, 243. In one or more embodiments, the anchors 265 may be fixedly coupled to the case halves 242, 243 (e.g., the anchors 265 may be integrally formed with the case halves 242, 243). The opposite ends 266, 267 of the secondary attachment loop 205 may be coupled to the anchors 265 in any suitable manner. For instance, in one embodiment, the opposite ends 266, 267 of the secondary attachment loop 205 may include loops 270, 271 (e.g., eyelets) configured to be slipped over the externally threaded portions 268 of the anchors 265. The anchors 265 may be threaded into the internally threaded blind bores 269 of the case halves 242, 243 to clamp the ends 266, 267 of the secondary attachment loop 205 against the outer sidewalls 246 of the case halves 242, 243. In one or more embodiments, the opposite ends 266, 267 of the secondary attachment loop 205 may be fixedly coupled to the anchors 265. The secondary attachment loop 205 may be made out of any suitably strong and durable material capable of withstanding the anticipated loads on the secondary attachment loop 205, such as, for instance woven synthetic fibers. Additionally, the secondary attachment loop 205 may be either rigid or flexible.

[0034] To install the secondary attachment assembly 200 on the tether 102, the first and second shell halves 206, 207 of the bullet assembly 202 are brought together around the tether 102, above the bead 201. The first and second shell halves 206, 207 may be properly aligned relative to each other by inserting the locating pins 227 into the alignment openings 226 in one of the shell halves 206 and then bringing the shell halves 206, 207 together such that the locating pins 227 extend into the corresponding alignment openings 226 in the other shell half 207. The bullet assembly 202 may then be slid down along the tether 102 until the bullet assembly 202 contacts the bead 201 and the annular recess 223 defined in the bullet assembly 202 receives at least a portion of the bead 201. The engagement between the bullet assembly 202 and the bead 201 is configured to retain the bullet assembly 202 in the desired position along the tether 102 (i.e., the bead 201 is configured to function as a stop preventing the bullet assembly 202 from sliding further down along the tether 102 past the bead 201 ). The bead 201 is also configured to transfer tension loads applied on the secondary attachment loop 205 (e.g., tension loads applied to the secondary attachment loop 205 during a task of detaching the tether 102 from the ground handling equipment 109 and coupling the tether 102 to the simple mooring point 121 ) to the outer sleeve 111 of the tether 102 and thereby mitigate the risk of crushing or compressing the tether 102, which could damage the electrical lines (e.g., power supply lines 114, ground and return lines 115, 116, and fiber optic lines 117) in the tether 102 and/or inhibit the flow of lifting gas through the feedtube 113 to the aerostat 101.

[0035] The first and second semi-annular parts 228, 229 of the lock ring 203 may then be brought together around the frusto-conical portion 217 of the bullet assembly 202. The first and second semi-annular parts 228, 229 of the lock ring 203 may be coupled together by inserting the fasteners 241 through the openings 239 in one of the semi-annular parts 228 and into the corresponding internally threaded bores 240 in the other semi-annular part 229. In one or more embodiments, the fasteners 241 may be inserted through corresponding through holes in the first and second semi- annular parts 228, 229 of the lock ring 203 and coupled to the semi-annular parts 228, 229 by nuts. The lock ring 203 may then be slid down along the frusto-conical portion 217 of the bullet assembly 202. In one embodiment, the lock ring 203 may be slid down along the frusto-conical portion 217 of the bullet assembly 202 until the inner surfaces 232 of the lock ring 203 halves engage the outer sidewalls 212 of the bullet assembly 202, the annular recess 238 in the lock ring 203 receives at least a portion of the shoulders 216 on the bullet assembly 202, and the lock ring 203 rests on the shoulders 216 of the bullet assembly 202. The engagement between the inner surfaces 232 of lock ring 203 and the outer sidewalls 212 of the bullet assembly 202 biases the shell halves 206, 207 of the bullet assembly 202 together, thereby securing the bullet assembly 202 to the tether 102. The engagement between the lock ring 203 and the shoulders 216 of the bullet assembly 202 is configured to prevent the lock ring 203 from inadvertently disengaging the bullet assembly 202 (i.e., the shoulders 216 are configured to function as a stop retaining the lock ring

203 on the bullet assembly 202 as the lock ring 203 is forced down along the bullet assembly 202).

[0036] The first and second case halves 242, 243 of the outer housing assembly

204 may then be brought together around the bullet assembly 202 and the lock ring 203. The first and second case halves 242, 243 may then be coupled together by inserting the fasteners 264 through the openings 262 in one case half 242 and into the corresponding internally threaded blind bores 263 in the other case half 243. In one or more embodiments, the fasteners 264 may be inserted through corresponding through holes in the case halves 242, 243 and coupled to the case halves 242, 243 by nuts. In one or more embodiments, if the secondary attachment loop 205 is flexible, the secondary attachment loop 205 may be coupled to the anchors 265 on the outer housing assembly 204 before or after the first and second case halves 242, 243 are coupled together around the bullet assembly 202 and the lock ring 203. [0037] When the outer housing assembly 204 is installed around the bullet assembly 202 and the lock ring 203, the frusto-conical portion 217 of the bullet assembly 202 extends up at least partially through the upper opening 257 in the bullet assembly 202 and the lower flanges 250 on the outer housing assembly 204 extend below the bead 201 on the tether 102. Additionally, in the illustrated embodiment, when the outer housing assembly 204 is installed over the bullet assembly 202 and the lock ring 203, the lock ring 203 is received in the cavity 259 between the upper and lower flanges 248, 250 and the upper shoulders 255 of the upper flanges 248 abut against the upper surfaces 230 of the lock ring 203. Accordingly, when force is applied to the secondary attachment loop 205, that force is transmitted to the lock ring 203 and forces the lock ring 203 downward along the outer sidewalls 212 of the bullet assembly 202, which further secures the shell halves 206, 207 of the bullet assembly 202 together around the tether 102.

[0038] In one embodiment, the tether 102 may include a reinforcing layer at the portion of the tether 102 that is engaged by the secondary attachment assembly 200. In one embodiment, the reinforcing layer may be an additional layer of fibers woven into the outer sleeve 111 of the tether 102. The reinforcing layer is configured to distribute the tensile load supplied from the bullet assembly 202 across the outer sleeve 111 of the tether 102 and/or increase the frictional force between the bullet assembly 202 and the tether 102. In one embodiment, the reinforcing layer may be the same or similar material as the outer sleeve 111 , although in one or more embodiments, the reinforcing layer may be a different material than the outer sleeve 111

[0039] FIG. 3 illustrates a method 300 of disconnecting the lower end of the tether 102 from the ground handling equipment 109 and connecting the lower end 108 of the tether 102 to a simple mooring point 121 according to one embodiment of the present disclosure. In the illustrated embodiment, the method 300 includes a task 310 of coupling a service line to the secondary attachment loop 205 on the tether 201. The method 310 also includes a task 320 of tensioning the service line until the tensile load on the lower end 108 of the tether 102 supplied by the buoyancy of the aerostat 101 is transferred to the service line (e.g., tensioning the service line until the lower end 108 of the tether 102 is slack). The task 320 of tensioning the service line may be performed by any suitable process, such as, for instance, by pulling the service line with a vehicle and/or winding the service line around a reel. For instance, the task 320 may include pulling the service line toward the ground until the tensile load on the lower end 108 of the tether 102 is transferred to the service line. In the illustrated embodiment, the method 300 also includes a task 330 of disconnecting the lower end 108 of the tether 102 from the ground handling equipment 109 (e.g., disconnecting the lower end 108 of the tether 102 from the reel, the lifting gas supply, and the power source).

[0040] In the embodiment illustrated in FIG. 3, the method 300 also includes a task 340 of connecting the lower end 108 of the tether 102 to the simple mooring point 121 , reconnecting the feedtube 113 to the lifting gas supply, and reconnecting the electrical lines (e.g., reconnecting the power supply lines 114, the ground and return lines 115, 116, and the fiber optic lines 117). The method 300 also includes a task 350 of extending the service line (e.g., unwinding the service line from the reel) until the tension from the aerostat 101 is reapplied to the lower end 108 of the tether 102. Additionally, in the illustrated embodiment, the method 300 includes a task 360 of disconnecting the service line from the secondary attachment loop 205 on the tether 102. The aforementioned steps may be performed in reverse such that the tether 102 may reconnected to the ground handling equipment 109 at the end of the aerostat deployment in order to rewind the tether 102 around the reel and thereby lower the aerostat 101. By disconnecting the tether 102 from the ground handling equipment 109, the ground handling equipment 109 can be used for another aerostat deployment. Additionally, disconnecting the tether 102 from the ground handling equipment 109 allows the ground handling equipment 109 to be stored during the deployment of the aerostat 101 , which mitigates the risk that the ground handling equipment 109 could become damaged, such as from inclement weather during the deployment of the aerostat 101.

[0041] While this invention has been described in detail with particular references to embodiments thereof, the embodiments described herein are not intended to be exhaustive or to limit the scope of the invention to the exact forms disclosed. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of assembly and operation can be practiced without meaningfully departing from the principles, spirit, and scope of this invention. Although relative terms such as "outer," "inner," "upper," "lower," "below," "above," "vertical," "horizontal," and similar terms have been used herein to describe a spatial relationship of one element to another, it is understood that these terms are intended to encompass different orientations of the various elements and components of the invention in addition to the orientation depicted in the figures. Additionally, as used herein, the term "substantially" and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Moreover, the tasks described above may be performed in the order described or in any other suitable sequence. Additionally, the methods described above are not limited to the tasks described. Instead, for each embodiment, one or more of the tasks described above may be absent and/or additional tasks may be performed. Furthermore, as used herein, when a component is referred to as being "on" or "coupled to" another component, it can be directly on or attached to the other component or components may be present therebetween.

Claims

WHAT IS CLAIMED IS:

1 . An aerostat system, comprising:

an aerostat;

a tether having a first end coupled to the aerostat and a second end opposite the first end configured to be coupled to ground handling equipment; and a secondary attachment loop on the tether, the secondary attachment loop disposed between the first and second ends of the tether and configured to facilitate transferring the tether from the ground handling equipment to a simple mooring point.

2. The aerostat system of claim 1 , wherein:

the tether comprises an outer sleeve, and

the secondary attachment loop is integral with the outer sleeve.

3. The aerostat system of claim 2, wherein each of the outer sleeve and the secondary attachment loop comprise woven fibers.

4. The aerostat system of claim 1 , wherein the secondary attachment loop is detachable from the tether.

5. The aerostat system of claim 1 , further comprising a bead coupled to the tether, the bead configured to retain the secondary attachment loop on the tether.

6. The aerostat system of claim 5, further comprising:

a bullet assembly configured to be coupled to the tether and engage the bead; a lock ring configured to engage the bullet assembly; and

an outer housing assembly configured to engage the lock ring, wherein the secondary attachment loop is coupled to the outer housing.

7. The aerostat system of claim 1 , wherein the tether comprises a feedtube for supplying a lifting gas to the aerostat.

8. The aerostat system of claim 7, wherein the tether further comprises a plurality of cables configured to supply power and control signals to the aerostat.

9. The aerostat system of claim 1 , further comprising a service line having a first end configured to be coupled to the secondary attachment loop and a second end configured to be coupled to the simple mooring point.

10. The aerostat system of claim 1 , wherein the ground handling

equipment comprises a reel configured to retract the tether.

1 1 . A tether for an aerostat system, the tether comprising:

an outer sleeve having a first end configured to be coupled to an aerostat and a second end opposite the first end configured to be coupled to ground handling equipment; and

a secondary attachment loop coupled to the outer sleeve between the first and second ends.

12. The tether of claim 1 1 , wherein the secondary attachment loop is integral with the outer sleeve.

13. The tether of claim 1 1 , wherein each of the outer sleeve and the secondary attachment loop comprise woven fibers.

14. The aerostat system of claim 1 1 , wherein the secondary attachment loop is detachable from the outer sleeve.

15. The tether of claim 1 1 , further comprising:

a bead coupled to the outer sleeve;

a bullet assembly configured to be coupled to the outer sleeve and engage the bead;

a lock ring configured to engage the bullet assembly; and

16. The tether of claim 1 1 , further comprising a feedtube housed in the outer sleeve and configured to supply lifting gas to the aerostat.

17. A method of transferring an aerostat system comprising an aerostat, a tether having a first end coupled to the aerostat and second end attached to ground handling equipment, and a secondary attachment loop on the tether between the first and second ends, from the ground handling equipment to a simple mooring point, the method comprising:

attaching a first end of a service line to the secondary attachment loop on the tether;

tensioning the service line until tension on the second end of the tether is removed;

disconnecting the second end of the tether from the ground handling equipment; and

attaching the second end of the tether to the simple mooring point.

18. The method of claim 17, further comprising:

extending the service line until the tension is reapplied to the second end of the tether; and

disconnecting the first end of the service line from the secondary attachment loop.

19. The method of claim 17, further comprising:

coupling the second end of the tether to a gas supply for supplying a lifting gas; and

supplying the lifting gas through the tether to the aerostat.

20. The method of claim 19, wherein the lifting gas is hydrogen.