U.S. patent application number 13/867167 was filed with the patent office on 2013-09-19 for tethered tow body, communications apparatus and system.
This patent application is currently assigned to Adaptive Methods, Inc.. The applicant listed for this patent is Walter Allensworth, Kevin Kieffer, Peter Owen, James Wiggins, Conrad Zeglin. Invention is credited to Walter Allensworth, Kevin Kieffer, Peter Owen, James Wiggins, Conrad Zeglin.
Application Number | 20130239863 13/867167 |
Document ID | / |
Family ID | 43464381 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130239863 |
Kind Code |
A1 |
Wiggins; James ; et
al. |
September 19, 2013 |
TETHERED TOW BODY, COMMUNICATIONS APPARATUS AND SYSTEM
Abstract
The problem of providing a submerged vehicle with
above-the-surface communications to a nearby vessel, shore
platform, or satellite while traveling at operating speed is solved
by an efficiently deployable tethered tow body having a
hydrodynamic and buoyant hull body and incorporating a
lift-generating wing that provides hydrodynamic lift to efficiently
lift the tow body containing antennas and other communications
devices to the surface. The tow body allows for stable operation
during underwater tow, surface tow, and transitions between
underwater tow and surface tow. Disclosed embodiments include
communications apparatuses encompassing the principles of the
tethered tow body, as well as various underwater systems that
incorporate a tethered tow body or communications apparatus for
establishing communications with a nearby vessel, shore platform,
or satellite.
Inventors: |
Wiggins; James; (Thurmont,
MD) ; Allensworth; Walter; (Germantown, MD) ;
Kieffer; Kevin; (Washington, DC) ; Owen; Peter;
(Monrovia, MD) ; Zeglin; Conrad; (Rockville,
MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wiggins; James
Allensworth; Walter
Kieffer; Kevin
Owen; Peter
Zeglin; Conrad |
Thurmont
Germantown
Washington
Monrovia
Rockville |
MD
MD
DC
MD
MD |
US
US
US
US
US |
|
|
Assignee: |
Adaptive Methods, Inc.
Rockville
MD
|
Family ID: |
43464381 |
Appl. No.: |
13/867167 |
Filed: |
April 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13339455 |
Dec 29, 2011 |
8443750 |
|
|
13867167 |
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|
12505194 |
Jul 17, 2009 |
8104420 |
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13339455 |
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Current U.S.
Class: |
114/244 |
Current CPC
Class: |
B63B 21/66 20130101;
H01Q 1/34 20130101; B63G 8/42 20130101; H01Q 1/04 20130101; B63B
1/16 20130101 |
Class at
Publication: |
114/244 |
International
Class: |
B63B 21/66 20060101
B63B021/66 |
Claims
1-49. (canceled)
50. An underwater vehicle comprising: an outer hull having a tow
body stowage area; a communication apparatus capable of being
stored in the tow body stowage area and providing above the surface
communications, the apparatus comprising: a tow body tethered to
the underwater vehicle with a tether, the tow body comprising a
hydrodynamic hull body including a top surface, wherein the top
surface conforms to a portion of the outer hull of the underwater
vehicle when the communications apparatus is stored in the tow body
stowage area.
51. The underwater vehicle of claim 50, further comprising an
electronics assembly located inside the hydrodynamic hull body.
52. The underwater vehicle of claim 51, wherein the electronics
assembly includes a processor.
53. The underwater vehicle of claim 51, wherein the electronics
assembly includes a wireless receiver.
54. The underwater vehicle of claim 51, wherein the electronics
assembly includes a wireless transmitter.
55. The underwater vehicle of claim 51, wherein the electronics
assembly includes a geo-location receiver.
56. The underwater vehicle of claim 52, wherein the electronics
assembly is ventilated with cooling water entering through a
plurality of vent holes.
57. The underwater vehicle of claim 52, wherein the tether
transports power between the underwater vehicle and the electronics
assembly.
58. The underwater vehicle of claim 52, wherein the tether
transports signals between the underwater vehicle and the
processor.
59. The underwater vehicle of claim 50, wherein the communication
apparatus further comprises an antenna mounted to the tow body.
60. The underwater vehicle of claim 59, wherein the antenna is
spring-loaded for keeping the antenna substantially upright during
surface tow and retracted during stowage.
61. The underwater vehicle of claim 50, wherein the tow body
comprises a lifting wing for providing hydrodynamic lift to lift
the tow body from below the water surface to at least partially
above the water surface.
62. The underwater vehicle of claim 61, wherein the lifting wing
has a curved upper surface.
63. The underwater vehicle of claim 61, wherein the lifting wing
extends at least an entire length and width of the hydrodynamic
hull body of the tow body.
64. The underwater vehicle of claim 50, wherein the tow body is
towed at an attack angle between 10 to 20 degrees relative to the
surface.
65. The underwater vehicle of claim 50, wherein the tow body
comprises a vertical stabilizer projecting from a keel slot located
on the hull body.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to communications
apparatuses, and in particular to a tethered communications
apparatus that provides submerged vehicles with communications to
the outside world.
BACKGROUND
[0002] Submerged vehicles, such as unmanned underwater vehicles
(UUVs), are used in a variety of military applications, for
example, surveillance, reconnaissance, navigation, and defense.
When these vehicles are submerged, however, navigation and
communication are difficult. Inertial navigation systems, such as
gyroscopes or other computer and motion sensors that track
position, orientation and velocity can be used, but these systems
are subject to drift the longer they remain below the water
surface. Highly accurate global positioning system (GPS) navigation
systems and high-bandwidth radio frequency (RF) communications
links are not directly available to submerged vehicles due to the
rapid attenuation of radio frequency energy by water. Thus,
submerged vehicles are limited to communicating with low bandwidth
acoustics or wiring back to another vessel or shore platform.
[0003] Prior art communications devices for submerged vehicles,
such as the device disclosed in U.S. Pat. No. 5,379,034, rely
primarily on buoyancy to float an antenna to the water surface. The
tow angle .beta. of a tethered cable, calculated as the angle
between the cable and the direction the submerged vehicle is
traveling, is affected by the speed of the submerged vehicle. The
faster the vehicle travels, the smaller the tow angle .beta.,
resulting in the tethered cable being pulled straight back and the
communications device never reaching the water surface. The slower
the submerged vehicle travels, the larger the tow angle .beta.,
resulting in the tethered cable drifting straight up and the
communications device drifting to the surface. Prior art devices
that rely primarily on buoyancy require the submerged vehicle to be
stationary or to be traveling at significantly reduced speed in,
order for the antenna to drift to the surface. Thus, submerged
vehicles using these prior art devices cannot simultaneously
communicate and travel at operational speed. Other prior art
systems, such as those disclosed in U.S. Pat. Nos. 3,972,046 and
7,448,339, rely on an intermediary float tethered to an underwater
vehicle and a surface float having an antenna. These prior art
systems operate at very limited speed ranges because the surface
floats would be pulled underwater at all but the slowest speeds.
Additionally, the intermediary floats of these prior art systems
are towed underwater, thereby increasing the probability of
entanglement and drag when deployed. Still other prior art
arrangements, including the antenna arrangement disclosed in U.S.
Pat. No. 6,058,874, do not provide for conformal stowage in which a
tethered communications device can be stowed within and be quickly
deployed from an underwater vehicle, thereby, minimizing drag and
the likelihood of vehicle entanglement during operation.
[0004] Accordingly, there is a need and desire for an efficiently
deployable tethered communications apparatus and system for
providing submerged vehicles with bi-directional, high data rate
communications to a nearby vessel or shore platform as well as GPS
coordinate data for precise navigation while traveling at
operational speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a diagram of a UUV system in accordance with an
embodiment described herein.
[0006] FIG. 2 is a diagram of a communications apparatus in
accordance with an embodiment described herein.
[0007] FIG. 3 is a partial internal view of a communications
apparatus in accordance with an embodiment described herein.
[0008] FIGS. 4A and 4B are respectively a front view diagram and a
bottom view diagram of a tow body in accordance with an embodiment
described herein.
[0009] FIGS. 5A and 5B are respectively a front view diagram and a
bottom view diagram of a tow body in accordance with another
embodiment described herein.
[0010] FIG. 6 is a schematic diagram of an electronics assembly of
a communications apparatus in accordance with an embodiment
described herein.
[0011] FIG. 7A is a diagram of a reeling assembly in accordance
with an embodiment described herein.
[0012] FIG. 7B is a diagram of a reeling assembly mounted inside a
UUV system in accordance with an embodiment described herein.
DETAILED DESCRIPTION OF THE INVENTION
[0013] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof and illustrate
specific embodiments that may be practiced. In the drawings, like
reference numerals describe substantially similar components
throughout the several views. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
them, and it is to be understood that structural and logical
changes may be made. Sequences of steps are not limited to those
set forth herein and may be changed or reordered, with the
exception of steps necessarily occurring in a certain order.
[0014] The problem of providing a submerged vehicle with
above-the-surface communications to a nearby vessel, shore
platform, or satellite while traveling at operating speed is solved
by an efficiently deployable tethered tow body having a
hydrodynamic and buoyant hull body and incorporating a
lift-generating wing that provides hydrodynamic lift to efficiently
lift the tow body containing antennas and other communications
devices to the surface. The tow body allows for stable operation
during underwater tow, surface tow, and transitions between
underwater tow and surface tow.
[0015] Disclosed embodiments include communications apparatuses
encompassing the principles of the tethered tow body, as well as
various underwater systems that incorporate a tethered tow body or
communications apparatus for establishing communications with a
nearby vessel, shore platform, or satellite.
[0016] The invention may be used to particular advantage in the
context of submerged vehicles. Therefore, the following example
embodiments are disclosed in the context of UUV systems. However,
it will be appreciated that those skilled in the art will be able
to incorporate the invention into numerous other alternative
systems that, while not shown or described herein, embody the
principles of the invention.
[0017] FIG. 1 shows an underwater vehicle system 100 in accordance
with an embodiment described herein. UUV 170 may be, for example, a
modified ANT Glider Eyak 01 developed by Alaska Native
Technologies, LLC or a modified Remus 600 developed by Hydroid,
Inc. UUV 170 is modified to integrate with a communications
apparatus 110 having a tether 130 connected on one end to a reeling
assembly 150 within UUV 170 and on the other end to tow body 120.
UUV 170 has propulsor 180 at the aft end and a tow body stowage
area 160 cut out on the top surface of UUV 170. The tow body
stowage area 160 has a length and width equal to the length and
width of tow body 120, and a depth sufficient for tow body 120 to
fit entirely within UUV 170.
[0018] In accordance with an advantageous feature of this disclosed
embodiment, tow body 120 is deployed from the tow body stowage area
160 of UUV 170, thus, enabling UUV 170 to repeatedly establish
communications with the outside world in a quick and efficient
manner. Communications apparatus 110, comprising hydrodynamic tow
body 120 and tether 130 connecting tow body 120 to reeling assembly
150, can be completely stowed inside the tow body stowage area 160
to achieve seamless integration within UUV 170. Communications
apparatus 110 is positively buoyant enabling it to float to the
surface using hydrostatic force when UUV 170 is stationary. If
desired, vehicle guidance docking plates can be installed in the
tow body stowage area 160 to help align tow body 120 inside UUV
170. Seamless integration of communications apparatus 110 has the
effect of minimizing drag and minimizing the possibility of
entanglement as UUV 170 moves underwater. The communications
apparatus 110 and reeling assembly 150 are made so that they are
collectively neutrally buoyant and, therefore, will not impact the
depth control of UUV 170 when stowed or deployed.
[0019] The present inventors have discovered that tow bodies that
combine a lift-generating wing and a stable body structure achieve
good hydrodynamic performance. Therefore, in accordance with the
embodiments described herein, tow body 120 has a lifting wing
mounted on top of a tow body structure and, optionally, at least
one side float arranged on either side of the body structure for
providing buoyancy at the outer edges of lifting wing and to
stabilize tow body 120 during underwater tow.
[0020] In accordance with an advantageous feature of the disclosed
embodiment, tow body 120 is hydrodynamically clean in that it is
designed to minimize drag during underwater tow, to achieve good
hydrodynamic performance during surface tow, and to transition
stably between underwater tow and surface tow. Tow body 120 is able
to smoothly transition from underwater tow to being towed at least
partially above the surface during communication. Additionally, tow
body 120 is able to smoothly transition from surface tow to being
towed below the surface during retrieval.
[0021] FIG. 2 is a diagram of a communications apparatus 110 in
accordance with an embodiment described herein. Communications
apparatus 110 has a hydrodynamic tow body 120 with a mounted
antenna 250 and a tether 130 attaching tow body 120 to reeling
assembly 150. Tether 130 is comprised of tow cable 230 and bridles
270.
[0022] In the example embodiment of FIG. 2, tow body structure 210
is multi-sectional with an elongated center hull body 235, an aft
section 240 and a fore section 245. Bulkheads are optionally placed
at both ends of center hull body 235 to separate center hull body
235 from aft section 240 and fore section 245.
[0023] Lifting wing 200 is mounted on top of center hull body 235
to provide hydrodynamic lift for lifting an underwater tow body 120
to at least partially above the water surface. Lifting wing 200 is
at least as long as the length of tow body structure 210 and is
wider than the width of tow body structure 210, preferably, not
greater than its length. The width of lifting wing 200, however, is
constrained by the width of UUV 170. According to the example
embodiment of FIG. 2, lifting wing 200 curves outward, forming a
convex surface. Preferably, lifting wing 200 also has a convex fore
end, which reduces drag as tow body 120 is pulled through
water.
[0024] According to the example embodiment of FIG. 2, center hull
body 235 has a cylindrical shape while the aft section 240 and fore
section 245 are cone shaped. Aft section 240 and fore section 245
of tow body structure 210 have convex surfaces and are seamlessly
integrated with center hull body 235. Preferably, aft section 240
is slightly longer than fore section 245. Vent holes 260 are used
for cooling an electronics assembly located inside the center hull
body 235.
[0025] Tow body structure 210 of the disclosed embodiment is made
of polycarbonate, however, tow body structure 210 can be made of
any other non-metallic material having positive buoyancy, such as,
for example, carbonfiber, plastic, and fiberglass. The outer hull
of tow body structure 210 is preferably coated with a fiberglass
resin or polyester coating to provide a low drag surface.
[0026] Vertical stabilizer 255 extends from the bottom of tow body
structure 210, preferably the bottom of aft cone 240, to keep tow
body 120 substantially parallel with the water surface. If desired,
vertical stabilizer 255 is mounted to tow body structure 210
through a keel slot 265 built on the underside of aft cone 240. In
an advantageous feature of this embodiment, vertical stabilizer 255
is retractable during stowage to minimize the size of tow body
stowage area 160 within UUV 170. Vertical stabilizer 255 can be
made retractable using a spring or tether 130 can be used to extend
vertical stabilizer 255 during deployment of tow body 120. Upon
retrieval, vertical stabilizer 255 will be forced inside aft cone
240 by the rear edge of tow body stowage area 160.
[0027] According to the example embodiment of FIG. 2,
communications apparatus 110 can provide UUV 170 with
high-bandwidth RF communications link and GPS coordinate data.
Antenna 250 is a 802.11 antenna providing bi-directional, high
speed data rate of at least 1 Mbps at a distance of at least 1 km.
Antenna 250 is preferably small for taking up the least amount of
space in UUV 170 and for being less likely to be noticed when
deployed above the surface. Antenna 250 should also be
omnidirectional to allow it to change position relative to a remote
receiver.
[0028] Antenna 250 should be as vertical as possible during surface
tow so as to provide optimum communications to a nearby vessel or
shore platform. In the disclosed embodiment, antenna 250 is spring
mounted to lifting wing 200 to keep antenna 250 substantially
upright during surface tow. Antenna 250 is preferably positioned to
pivot slightly to the rear of tow body 120 to reduce the
possibility of breakage if tow body 120 encounters an obstacle
during tow. According to another advantageous feature of this
embodiment, antenna 250 folds down during retrieval and stowage to
reduce drag. It will be appreciated by those skilled in the art
that an electro-mechanical device can be used to raise and fold the
spring mounted antenna 250. Alternatively, a gimbaled antenna mount
can be used to maintain correct antenna position. Those skilled in
the art will appreciate that numerous other ways can be devised to
keep antenna 250 substantially vertical during surface tow.
[0029] FIG. 3 is a partial internal view of communications
apparatus 110 in accordance with an embodiment described herein.
Center hull body 235 is at least partially hollow. Aft bulkhead 310
separates aft section 240 from center hull body 235 and creates a
watertight enclosure inside hull body 235 for storage of
electronics assembly 320. If desired, tow body structure 210 can
optionally include a fore bulkhead that separates fore section 245
from center hull body 235. Particular embodiments may optionally
fill the inside of hollow hull body 235, aft section 240, and fore
section 245 with foam 550 to achieve positive buoyancy. Fore
section 245 has a convex surface with a V-shaped upper edge 540 for
deflecting water as tow body 120 is towed on a water surface.
[0030] In accordance with an advantageous feature of the disclosed
embodiment, the watertight chamber of center hull body 235
preferably encloses all electronics required for communications
apparatus 110 except for antenna 250. Communications apparatus 110
may be rapidly integrated with many different types of UUV systems
since UUV systems need only be able to send and receive data over
standard Ethernet connection using standard internet protocol (IP)
network protocols.
[0031] Heat sink plate 300 is preferably composed of aluminum and
welded perpendicularly to aft bulkhead 310. Electronics assembly
320 is mounted on both sides of heat sink plate 300. Electronics
assembly 320 is connected to 802.11 antenna 250 and a watertight
connector 330 for tow cable 230. Alternatively, electronics
assembly 320 may be potted inside hull body 235.
[0032] The present inventors have discovered that high signal
attenuation, increased power Consumption, and difficulty in
detecting when an antenna has reached the surface result from
locating only the 802.11 and GPS antennas on tow body 120 such that
the two antennas are connected to radio receivers onboard UUV 170
via a RF coaxial cable. Therefore, UUV 170, preferably,
incorporates a power over Ethernet module that co-locates radio
electronics and antennas for both 802.11 and GPS frequency bands.
Co-location of the radio electronics and antennas allows for a thin
tow cable to be used for communications apparatus 110 and minimizes
signal attenuation from the use of tow cable 230.
[0033] Tow cable 230 transfers both power and data between tow body
electronics assembly 320 and UUV 170. The present inventors have
found that using a coaxial cable to send RF signals to a surface
antenna would significantly increase the overall weight of
communications apparatus 110. At low operational speeds, tow body
120 would be unable to lift a heavy cable, thereby increasing the
likelihood of entanglement and significantly reducing the
operational range of UUV 170. Thus, tow cable 230 is preferably a
fiber optic cable. Using a polypropylene jacket, fiber optic cable
230 can be made slightly buoyant, thereby, reducing the possibility
of cable entanglement. If UUV 170 is stationary, a buoyant fiber
optic cable 230 can reach the surface if the deployed cable scope
is greater than the depth.
[0034] FIGS. 4A and 4B are respectively a front view diagram and a
bottom view diagram of an alternative embodiment of tow body 120
having a hydrodynamic boat hull shaped body structure 410. An
optional stabilizing side float 420 and at least one bridle
attachment bar 220 each having at least one bridle attachment point
are mounted onto a lifting wing 200 on either side of hull body
410. Lifting wing 200 is centered on and mounted on top of hull
body 410. Those skilled in the art will appreciate that electronic
assembly 320 can also be mounted inside boat hull shaped body
structure 410.
[0035] Another alternative embodiment of tow body 120 is
illustrated in FIGS. 5A and 5B, which respectively depicts front
and bottom views of tow body 120 having a hydrodynamic submarine
shaped body structure 510. It will be appreciated by those skilled
in the art that tow body 120 can have other alternative
hydrodynamic and buoyant tow body structures.
[0036] While the embodiment of FIG. 3 is described with regard to
multi-sectional tow body 120 of FIG. 2, it will be appreciated by
those skilled in the art that the tow bodies disclosed in FIGS. 4A,
5A, and other hydrodynamic tow bodies may be appropriately modified
to embody the principles of the invention described herein.
[0037] FIG. 6 is a schematic diagram of electronics assembly 320 in
accordance with an embodiment described herein. Electronics
assembly 320 contains an embedded processor 650 that relays data to
and from UUV 170 via fiber optic cable 230. Embedded processor 650
contains an onboard 802.11 radio receiver chip 660, RS232-level
serial interface 670 for GPS connectivity, 10/100 Ethernet LAN port
680 for tow cable 230, digital input/output 690, and sufficient CPU
and memory for routing data at up to 54 Mbps between the Ethernet
LAN port and the Wi-Fi interface of antenna 250. Antenna 250 is
connected to 802.11 transceiver 660 onboard embedded processor 650.
In addition to the 802.11 and GPS antennas, embedded processor 650
can be configured to capture other types of data, such as, for
example, images with an onboard camera. Electronics assembly 320
also includes a float switch 610 connected to the digital
input/output 690 of embedded processor 650, a DC power converter
630, and an Ethernet to fiber optic converter 640.
[0038] The example embodiment of FIG. 6 employs a Compulab CM-X270
computer-on-module board with a PXA270ARM processor to meet all of
the above requirements, but other embedded processors that consume
little power and space can be used. The Compulab CM-X270 board
measures only 66.times.44.times.7 mm and consumes 2W at maximum
processor load.
[0039] An integrated GPS antenna and receiver module 620 is
connected to a RS232-level serial interface 670. The integrated GPS
antenna and receiver module 620 can be, for example, Mighty GPS's
all-in-one BG-320RGT GPS module. The RS232-level serial interface
670 output is connected directly to the CM-X270 serial port of
embedded processor 650. Tow body structure 210 is made of a
non-metallic material and, thus, will not interfere with satellite
reception.
[0040] Embedded processor 650 preferably supports the open source
embedded Linux operating system, but any other operating system
supported by embedded processor 650 may be used. The operating
system on embedded processor 650 runs at least three software
modules that together provide the required functionality for
communications apparatus 110.
[0041] First, the disclosed embodiment includes network layer
packet routing software to forward IP packets between UUV 170 and,
for example, a remote surface receiver. The routing software should
not buffer packets due to intermittent or slow wireless
connections, for example, because buffering should be handled by a
TCP control flow set up by UUV 170 or the remote surface
receiver.
[0042] Second, embedded processor 650 includes a software module
for, supporting GPS navigation or other similar type platforms as
known in the art. This software module receives, parses and decodes
serial GPS NMEA 0813 messages from integrated GPS antenna and
receiver module 620. The decoded GPS information would be collected
and sent periodically to UUV 170 as, for example, a TCP, UDP, XML,
or CORBA message through Ethernet LAN port 680.
[0043] Third, embedded processor 650 includes a software module for
supporting communications between UUV 170 and communications
apparatus 110. This software module sends status information to and
receives command and control messages from UUV 170. Status
information from embedded processor 650 includes, for example,
wireless signal strength, available wireless networks, status of
float switch 610 and GPS receiver 620, and other system
information. Command messages from UUV 170 includes, for example,
control over the transmit power, configured wireless network,
encryption parameters, and other network and system
configurations.
[0044] If desired, an optional bi-directional RF amplifier 600 can
be added between antenna 250 and the onboard 802.11 radio receiver
620 to improve link reliability and boost transmit power. The
disclosed embodiment uses a 2.4 GHz bi-directional RF amplifier,
such as, for example, the 2400CAE 2.4 GHz bi-directional amplifier
manufactured by RF Linx, which provides 1 W of transmit power and
20 dB of receive gain. Amplifier 600 is preferably mounted directly
on heat sink plate 300 for improved heat dissipation.
[0045] In accordance with another illustrative feature of the
disclosed embodiment, communications apparatus 110 has seawater
cooling electronics capability. Referring to FIG. 2, vent holes 260
in aft cone 240 provide a constant supply of cooling water to heat
sink plate 300. Electronics assembly 320 is ventilated with cooling
water entering through the vent holes 260 located on aft section
240 and exiting through keel slot 265 on the underside of aft
section 240. Alternatively, if electronics assembly 320 is potted
inside hull body 235, amplifier 600 should be mounted at the lowest
point of tow body structure 210 so that seawater can be used for
heat dissipation.
[0046] FIG. 7A is a diagram of a reeling assembly 150 and FIG. 7B
is a diagram of the reeling assembly 150 mounted inside UUV 170 in
accordance with an embodiment described herein. Reeling assembly
150 includes a waterproof motor housing 700 enclosing a direct
current (DC) motor with an attached spur gearbox (not shown),
preferably having a 15:1 gear ratio, that is powered by a
waterproof cable connected to a power supply and control switch in
UUV 170. Control switch directs the power to the motor to control
reeling tow body 120 in and out of tow body stowage area 160.
Attached to the DC motor is a cable drum 710 large enough to
accommodate the length of tether 130. Cable drum 710 sits inside a
reel frame. If desired, a level wind can be mounted on cable drum
710 to prevent tether 130 from jamming during reeling of tow body
120.
[0047] Reeling assembly 150 provides tension for holding stowed tow
body 120 inside UUV 170. If desired, an inner cover 740 which
conforms to the bottom of tow body 120 can be mounted over reeling
assembly 150 to streamline the tow body stowage area 160 and,
thereby reduce drag. A hole in the cover 740 serves as a fairlead
in directing tether 130 onto the drum 710. Once tow body 120 has
reached the surface, float switch 610 of electronics assembly 320
is triggered to signal the DC motor to stop. High-speed
communication to another vessel or shore platform and acquisition
of GPS satellite data can then commence.
[0048] UUV 170 can provide all the power required to run
electronics assembly 320 except for a small battery that runs a
clock inside electronics assembly 320. Fiber optic cable 230
preferably contains two 24 American Wire Gauge (AWG) conductors for
transporting power to tow body 120 from UUV 170 and a fiber for
transporting data. A single 24 gauge wire provides almost 7 W of
power at 12 V. The present inventors found that electronics
assembly 320 would require approximately 2 W to 12 W depending on
the RF amplifier used. If needed, additional power can be obtained
by using a DC-DC converter 630 to step down the transmitted voltage
at tow body 120.
[0049] Referring to FIG. 1, tow body 120 can be lifted to the
surface within a UUV operational speed ranging from stationary to
approximately 5 knots. After deploying to the water surface, tow
body 120 should sit high on the water so that antenna 250 remains
vertical and out of the water for better reception. Furthermore,
tow body 120 must be stable at both planing and displacement speeds
of up to approximately 5 knots for a prolonged period of time. The
present inventors have discovered that the optimal attack angle
.alpha. for tow body 120, measured relative to the water surface,
is approximately 10 to 20 degrees. Tow body 120 can be towed
smoothly on the surface within this range for attack angle
.alpha..
[0050] Careful consideration must be given to selecting optimum
location(s) to attach bridle(s) 270 to tow body 120 so that a
sufficient lifting force is created to lift tow body 120 to the
surface and the attack angle .alpha. is approximately 10 to 20
degrees when tow body 120 is pulled across the surface. The bridle
attachment point(s) can be located on bridle attachment bars 220,
vertical stabilizer 255, or at other locations including, for
example, the tow body's 120 center of pressure and center of
buoyancy. The present inventors have discovered that a two-point
bridle attachment provided a stable configuration and low drag
during underwater tow, surface tow, and transitions to and from the
surface. The two bridle attachment points are located at the fore
and aft ends of bridle attachment bar 220 extending from the bottom
of tow body structure 210. Alternatively, the aft end attachment
point can be located on vertical stabilizer 255 below the center of
buoyancy, as shown in FIG. 2. By locating an attachment point on
vertical stabilizer 255, bridle 270 can be used to extend vertical
stabilizer 255 during deployment of tow body 120. It will be
appreciated by those skilled in the art that other bridle
attachment configurations may be employed, such as, for example, a
single point attachment near the middle of bridle attachment bar
220 extending from the bottom of tow body structure 210, or a three
point bridle attachment in which two attachment points are located
on either fore corner of lifting wing 200 and a third attachment
point is located on vertical stabilizer 255 below the center of
buoyancy.
[0051] The foregoing merely illustrate the principles of the
invention. Although the invention may be used to particular
advantage in the context of submerged vehicles, those skilled in
the art will be able to incorporate the invention into other
non-vehicle systems, such as submerged platforms. It will thus be
appreciated that those skilled in the art will be able to devise
numerous alternative arrangements that, while not shown or
described herein, embody the principles of the invention and thus
are within its spirit and scope.
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