Patent Publication Number: US-10780961-B2

Title: Method of establishing communication for sub-ice submarine missions between a sub-ice vessel and a terrestrial facility using a laser-powered ice-penetrating communications delivery vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation application claiming priority to and the benefit of U.S. application Ser. No. 16/265,504, filed Feb. 1, 2019, which claims priority to and the benefit of U.S. provisional application Ser. No. 62/625,159, filed Feb. 1, 2018, and entitled “Laser-Powered Ice-Penetrating Communications Antenna for Sub-Ice Submarine Missions,” both of which are hereby incorporated by reference herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to communication devices, and more specifically to laser-powered ice-penetrating communications delivery vehicles for sub-ice submarine missions. 
     2. Description of the Related Art 
     Currently, submarines deploy tethered buoyant communications antennas, which come to rest on the underside of the ice shelf. These antennas can receive radio communications from above the ice at very low bandwidth, but have no transmitting capability. The lack of transmitting capabilities is due to poor radio frequency (RF) propagation in the highly conductive sea water environment. Having only unilateral, low bandwidth communication with the surface represents a significant impairment of operational capability. 
     Accordingly, there is a need for a compact and rapidly deployable device that can deliver a communication payload (or other payload) through a thick ice sheet to the clear surface exposed to atmosphere, thus allowing high bandwidth, bi-directional communication between a sub-surface vehicle and command and control. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention overcomes the problem of how to establish high bandwidth, bi-directional communication through a thick ice sheet between a sub-ice vessel and a receiving and/or transmitting body located on the other side of the ice sheet. 
     The present invention is a laser powered, ice penetrating system with a vehicle that can deliver a communication payload (or other payload) through a thick ice sheet, through an overlying firn layer (snow left over from prior seasons and recrystallized into a substance denser than névé, which is partially melted, refrozen and compacted snow preceding ice formation), and to the clear surface exposed to atmosphere, thus allowing high bandwidth, bi-directional communication between satellite networks, ground level communication systems, and large under-ice vehicles. 
     The actuating force for such a delivery vehicle while below the level of the water surface is supplied by its buoyancy. Boring through the thick ice sheet is achieved through a direct-melt laser drilling apparatus, wherein optical energy is supplied to the delivery vehicle over a fiber optic tether from a sub-ice vessel, e.g., submarine. High energy light impinges directly on the ice, melting the ice, while the penetrator&#39;s buoyancy keeps the nose (or front end) in contact with the upper end of the borehole. Buoyancy is maintained through the use of buoyancy materials, such as syntactic foam, aerogel and other similar low density materials, which are concentrated near the forward end of the penetrator to keep the penetrator oriented vertically as the penetrator progresses. In this application, the terms “delivery vehicle” and “penetrator” are used synonymously. 
     Optical power from the sub-ice vessel is transferred to the penetrator, or delivery vehicle. A fiber laser unit supplies the required optical power for penetrating the ice. The laser operates in the 1-5 kW range and may be carried on board the sub-ice vessel, e.g., submarine. The laser supplies the power necessary to achieve rapid (e.g., 1 ft/min) ice penetration for a small diameter penetrator. Yet, even at this high level of power, the laser unit is compact enough to be installed practically aboard submarines with constrained hatch sizes and limited onboard space. 
     A fiber optic tether delivers the optical power to the buoyant penetrator. In one embodiment, the fiber optic tether is a multimode fiber optic tether. A commercially available laser unit of this power, with a typical armored process fiber, is the Ytterbium Laser System, Model YLS-1000 from IPG Photonics Corporation, though other comparable laser sources may also be used and remain within the contemplation of the present invention. The penetrator of the present invention utilizes a much smaller diameter buffered fiber, on the order of 0.040″ diameter. 
     The fiber tether is stored in a launch tube attached to the external surface of the sub-ice vessel. When the buoyant penetrator is released from the sub-ice vessel, the fiber tether is passively deployed from the penetrator as the penetrator rises (via buoyancy action) through the water and/or ice. 
     The present invention melts the ice by applying laser power directly to the ice in front of the penetrator. The process fiber, originating from the sub-ice vessel, is terminated into an optics package inside the penetrator. The function of this optics package is to optimize the laser beam for ice penetration, first by passing the beam through a collimating optic, and then to a divergent optic to expand the beam on the ice directly impeding upward penetrator progress. The rate of penetration, for a given beam energy, follows an inverse square dependence on penetrator diameter. Consequently, holding the beam diameter at the minimum requisite dimension through precise collimation, and minimizing penetrator diameter, produces exponential gains in penetration rates. 
     A feature of the present invention is that melting of the ice is achieved by direct application of laser energy to the ice, rather than first converting this energy to heat (as in heated nose cone, hot water jetting, or hybrid designs). The use of 1070 nm wavelength laser light is important. At this wavelength optical energy is preferentially absorbed by solid ice as opposed to liquid water. This prevents, e.g., flashing of the water at higher power levels. Instead, through proper design of the optics chain, close to 100% of the optical power is deposited into a narrow cone just ahead of the penetrator and melting a hole having a diameter only slightly larger than the penetrator hull diameter. The result is significantly higher penetration rates compared to any other technology. 
     The use of focused 1070 nm radiation to create the melt hole produces several types of efficiency gains. First and foremost, using focused radiation eliminates a large amount of bulky hardware, translating to reduction in both penetrator length and diameter, the latter being paramount. Second, waste heat is greatly reduced, where waste heat is defined as unnecessary internal and shell heating in regions other than the penetrator nose. Particularly in environments where the ice is near phase change temperature, shell heating is largely wasteful, as heat does not need to be applied continuously to the borehole wall to allow passage of the aft end of the penetrator. Third, adopting a passive optics system to apply energy to the ice eliminates the need for pumps or other active hardware, reducing the penetrator&#39;s electrical onboard power budget and improving reliability. This, in turn, also reduces penetrator size and increases buoyancy, by reducing battery volume and weight. 
     Finally, adopting a direct laser melting system minimizes the need for intimate contact between the penetrator nose and the ice surface, since an optical mode of melting does not rely on direct contact to impart energy to the ice. This becomes especially significant when ascending through the ice and fern layer above sea level, as an ascending system may not keep the penetrator nose in continuous contact with the top of the borehole. This direct laser penetrator capability has been demonstrated in the laboratory using a 5 kW commercially available laser. 
     This ice melting system is relatively silent and does not utilize any energetic or pyrotechnic materials that would be hazardous to store or handle on the submarine, thus reducing the time to field this system. Further details of the direct application of laser energy to ice is found in U.S. Pat. No. 9,963,939 (Stone, et. al), entitled, “Direct Laser Ice Penetration System,” and incorporated by reference herein. 
     The present invention may deliver a communication payload from a sub-ice environment to the ice surface in various manners. In one embodiment of the present invention, upon reaching the ice-water interface (i.e., the bottom surface of the ice sheet), the penetrator begins melting the ice directly in front of the penetrator using a laser. This direct impingement of the laser to the ice-water interface melts the ice, forming a borehole through which the penetrator may pass. The penetrator continues melting the ice while simultaneously conducting a buoyant ascent advancing upward toward sea level within the just-formed borehole within the ice sheet. 
     Once the buoyancy is no longer sufficient to continue the advancement of the penetrator upwards (i.e., beyond sea level toward the surface), the penetrator then anchors itself to the interior surface of the borehole. The laser melting system of the present invention continues to function, melting a conical hole through the ice and snow. At this point, communications is established via a telescopic antenna. 
     Should it prove necessary to move (advance) the penetrator from sea level upward towards the surface (including through the potential presence of a firn layer), an electrically driven mechanical ascending system is employed. Such an ascending system functions by lodging the penetrator in place in the borehole while a void is created in the ice in advance of the nose by the laser, and then relocating the penetrator upwards via an extending and retracting mechanism in the penetrator hull. Alternatively, the ascending system may include a traction mechanism. 
     In the former scenario, the penetrator is held in place by, for example, a series of 3 to 8 spring loaded cams on the outside perimeter of the penetrator that allows only upward motion. A small motor is employed to extend the forward section of the penetrator upward once the penetrator has melted some ice and developed sufficient headroom. The aft section is then retracted into the forward section (akin the locomotion of an inch worm), and the process repeats. 
     In the latter scenario, the penetrator employs a motor or motors to turn, for example, toothed wheels held pressed against the borehole walls by a biasing pressure, developing traction against the ice. The wheels are rotated continuously to hold the penetrator nose against the ice. Alternatively, the wheels are turned on intermittently with a ratcheting mechanism capturing progress. 
     Communication to and from the delivery vehicle is achieved by a much smaller, separate fiber optic line integrated into a single tether along with the power fiber. This hybrid tether could be used to send and receive commands to and from the delivery vehicle as well as transmit and receive operational communications to and from the antenna. The hybrid tether is deployed by the penetrator and does not require any action from the sub-ice vessel following deployment. The size of the payload delivered to the surface of the ice is dictated by parameters determined by specific concept of operations (CONOPS) and existing communications systems. 
     Onboard electrical power requirements for the delivery system are minimal. In an embodiment that does not incorporate an active ascent mechanism, electrical power is only required to drive onboard control electronics. 
     However, in another embodiment where an active ascent mechanism is utilized (i.e., an actuated ascending system), additional electrical power is required to lift the penetrator hull out of the water and upward through the borehole as the penetrator hull extends. However, since progress is captured by camming or ratcheting features on the outer diameter of the penetrator, power will only need to be applied intermittently. In an embodiment where the active ascent is performed via a traction mechanism, electrical power is required to turn the toothed wheels or tracks. The requisite power for modest ascents may be carried aboard in a compact battery bank, e.g., a lithium-ion battery stack, a fuel cell stack, etc. 
     It is an object of the present invention to provide for an expendable communications device for sub-ice vessels to communicate with external facilities. 
     It is another object of the present invention to provide for an expendable communications device configured to melt a borehole through an ice mass and traverse through the ice mass until the device reaches sea level. 
     It is another object of the present invention to provide for methods of locomotion that allow an expendable communications device to advance beyond sea level and upward toward the surface as the device melts a borehole through an ice mass. 
     The communications payload delivery system of the present invention is compact and deploys rapidly. The present invention represents a significant advance in tactical capability and fills a large operational void that has existed since submarines have been conducting under ice operations. Additionally, the ice melting system of the present invention is relatively silent and does not utilize any energetic or pyrotechnic materials that would be hazardous to store or handle on a sub-ice vessel, i.e., the submarine, thus reducing the time to field this system. The present invention advantageously does not utilize chemical heating (e.g., thermite or sodium or the like) resulting in safe handling and operations. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  shows an environmental view of an underwater vehicle under an ice mass and employing an embodiment of the present invention to establish communication with a satellite. 
         FIG. 2  depicts a cut out view of an embodiment of the present invention traversing an ice mass. 
         FIG. 3  shows a cut out view of an embodiment of the present invention having broken through the surface of an ice mass. 
         FIG. 4  depicts a cut out view of an embodiment of the present invention traversing an ice mass and using a pyro charge to establish communication with a satellite. 
         FIG. 5  shows a cut out view of an alternative embodiment of the present invention using cams and an extendable retracting member and having broken through the surface of an ice mass. 
         FIG. 6  depicts a cut out view of an alternative embodiment of the present invention using retractable pins and an extendable retracting member and having broken through the surface of an ice mass. 
         FIG. 7  is a cut out view of an alternative embodiment of the present invention using a wheel and ratcheting mechanism and having broken through the surface of an ice mass. 
         FIG. 8  is a cut out view of an alternative embodiment of the present invention using a continuous tank track or caterpillar track mechanism and having broken through the surface of an ice mass. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , sub-ice vessel  10  traverses ocean water  12  under ice shelf  14  (or ice mass  14 , or ice sheet  14 ) and above ocean floor  16  in sub-freezing waters. Satellite  18  orbits above the earth in open atmosphere  22 . Ice shelf  14  may extend several meters (e.g., 100 meters up to 1000 meters) above sea level  20 , having substantial ice mass thickness between bottom surface  32  and ice surface  36  of ice shelf  14 . Consequently, communication between sub-ice vessel  10  and satellite  18  is little to none, as it is difficult to transmit or receive a signal through ice shelf  14  in this harsh environment. 
     Communication delivery vehicle  24  is releasably engaged to sub-ice vessel  10 . More particularly, communication delivery vehicle  24  is stored within launch tube  30  externally attached to sub-ice vessel  10 . Communication delivery vehicle  24  is tethered to sub-ice vessel  10  via process fiber  28  (power fiber) and communication optic line  26 . Desirous of establishing communication between sub-ice vessel  10  in the sub-ice environment and satellite  18  (or other communications apparatus or network) in open atmosphere  22 , communication delivery vehicle  24  is released from launch tube  30  of sub-ice vessel  10 . 
     Communication delivery vehicle  24  is comprised of a low density material, such as syntactic foam or aerogel (not shown), which provides substantial buoyancy to communication delivery vehicle  24 . This buoyancy allows communication delivery vehicle  24 , once released, to traverse ocean water  12  in an upward direction relative to sub-ice vessel  10 , ascending until front end  34  of communication delivery vehicle  24  comes in contact with bottom surface  32  of ice shelf  14 . 
     The buoyant material is concentrated at front end  34  of communication delivery vehicle  24  and maintains communication delivery vehicle  24  in an upright orientation as communication delivery vehicle  24  “floats” (ascends) toward bottom surface  32  of ice shelf  14 . This same substantial buoyancy positively biases communication delivery vehicle  24  upward such that front end  34  of communication delivery vehicle  24  may maintain contact and press against bottom surface  30  of ice mass  14 , as shown in  FIG. 1 . 
     Referring now to  FIG. 2 , the communications payload delivery vehicle  24  (i.e., the ice penetrator) is comprised of housing  38  having front end  34  and back end  29 . Several bays are safely secured and maintained within housing  38 . These include electronics bay  40 , payload bay  42 , and optics bay  44 . Payload bay  42  includes the communication payload, including the telescopic antenna. Optics bay  44  contains several components, including collimating optics and divergent optics. 
     A tether comprised of process fiber  28  and communication optic line  26  extends from back end  29  of communication delivery vehicle  24 . In one embodiment, a fiber spooler (not shown) containing the tether comprised of process fiber  28  and communication optic line  26  may be located within sub-ice vessel  10 . Alternatively, the fiber spooler may be located within communication delivery vehicle  24 . In the case of the former, the tether unravels from the fiber spooler as the tether is pulled away from sub-ice vessel  10  as communication delivery vehicle  24  “floats” away. In the case of the latter, the tether unravels from the fiber spooler as the tether is released from communication delivery vehicle  24  as communication delivery vehicle  24  “floats” away from sub-ice vessel  10 . 
     Process fiber  28  delivers optical power from a power source on sub-ice vessel  10  to communication delivery vehicle  24  to provide power to power consuming components of communication delivery vehicle  24 , e.g., electronics and optics. Divergent optics  46  is positioned at front end  34 . 
     Still referring to  FIG. 2 , communication delivery vehicle  24  is shown having reached bottom surface  32  of ice mass  14 . With the path of communication delivery vehicle  24  toward ice surface  36  blocked by ice mass  14 , communication delivery vehicle  24  begins to melt the ice at bottom surface  32 . 
     Laser beam  48  transmitting from front end  34  of communication delivery vehicle  24  is used for ice penetration. First, laser beam  48  passes through a collimating optic and then to divergent optic  46  to expand laser beam  48  on the ice directly impeding upward penetrator progress. Communication delivery vehicle  24  melts through ice mass  14 , forming borehole  50 , a conical hole through the ice and snow, as shown in  FIG. 2 . 
     As communication delivery vehicle  24  continues to melt the ice, communication delivery vehicle  24  continues its buoyant ascent to sea level  20  within borehole  50 . Upon reaching sea level  20 , the buoyancy force is not sufficient to advance communication delivery vehicle  24  any further. Communication delivery vehicle  24  then ceases movement and anchors (or wedges) itself to borehole walls  52 . The melting ice directly in front of laser beam  48  forms melt cavity  54  which enlarges as the ice melts. 
     The laser melting system of communication delivery vehicle  24  continues to function, melting the ice within melt cavity  54  directly in front of laser beam  48  and, ultimately, through remaining portion  56  of ice mass  14 . 
     Referring now to  FIG. 3 , once remaining portion  56  has been cleared and there is unobstructed space in open atmosphere  22  between communication delivery vehicle  24  and, for example, satellite  18 , communication is established via a telescopic antenna (not shown). With communication link  58  established, bilateral communications ensue between sub-ice vessel  10  and satellite  18  via communication delivery vehicle  24  and communication optic line  26 . 
     One problem that may be encountered is that the optical nose (front end  34 ) of communication delivery vehicle  24  reaches ice surface  36  but the transmission antenna does not reach the surface. In this circumstance, a pyro charge or charges may be incorporated. For example, in another embodiment, and referring now to  FIG. 4 , once ice surface  36  is traversed physically and optically (leaving an open tube), but the transmission antenna (not shown) does not reach ice surface  36 , pyro charge(s)  62  are used to “launch” an upper body portion  44  of communication delivery vehicle  24  out of borehole  50  and onto ice surface  36 . Additionally, the pyro charge(s) may further function to break through a few meters of snow cap to get upper body portion  44  to ice surface  36 . 
     Still referring to  FIG. 4 , upper body portion  44  has a spooler thereon that keeps upper body portion  44  in contact with the communication delivery vehicle  24 , but gets the antenna (not shown) out and away from borehole  50  and onto ice surface  36 . Fiber-optic cable  60  is released from upper body portion  44  as upper body portion  44  is “shot” out of borehole  50  into open atmosphere  22  and lands nearby on ice surface  36 . Communications between upper body portion  44  and satellite  18  are established through communication uplink  58 . Communications between upper body portion  44  and communication delivery vehicle  24  are established via fiber optic cable  60 . Communications between communication delivery vehicle  24  and sub-ice vessel  10  are established via communication optic line  26 . 
     The communication delivery vehicle of the present invention may advance through ice mass  14  using longitudinal extension means or, alternatively, traction means. In the former, the present invention incorporates a telescopic member within the communication delivery vehicle which, when in an expanded position, separates slidably engaging housings, and when in an unexpanded position, allows the slidably engaging housings to come together. In the latter, the present invention incorporates traction means using a plurality of traction elements that serve to advance the ice penetrator upward regardless of whether solid ice, firn, or snow is in the upward pathway. 
     Referring now to  FIG. 5 , for example, in one embodiment using longitudinal extension means, the housing of communication delivery vehicle  200  includes external housing  202  and internal housing  204 . External housing  202  and internal housing  204  are engagably slidable along a track  206 . The outside of internal housing  204  has a fixed track (not shown) that mates with a corresponding track (not shown) on the inside surface of external housing  202 , such that external housing  202  may slide away from internal housing  204  along the track  206  without completely separating from internal housing  204 . A plurality of spring loaded cams  216  are located at equal spaced distances around and on external housing  202 , and internal housing  204 . Motor  214  drives the plurality of spring loaded cams  216 . 
     In use, telescopic member  208  within the hull of communication delivery vehicle  200  extends distally from the penetrator hull in a linear fashion. As telescoping member  208  extends, such extending motion separates upper body  210  of communication delivery vehicle  200  from lower body  212  of communication delivery vehicle  200 . When telescoping member  208  reaches the desired extension length (which may be preconfigured to variable lengths depending on the environmental conditions encountered), communication delivery vehicle  200  is held secured and anchored in place to borehole walls  52  by a plurality of spring loaded cams  216  that allow only upward motion, as shown in  FIG. 5 . 
     Laser beam via melt optic  218  located at front end  222  of communication delivery vehicle  200  continues to melt ice directly in front of communication delivery vehicle  200 . Motor  214  is then employed to extend the forward section of communication delivery vehicle  200  upward once communication delivery vehicle  200  has developed sufficient headroom. Aft section  228  of communication delivery vehicle  200  is then retracted into the forward end  222 , and the process repeats until communication delivery vehicle  200  breaches ice surface  36 , establishing communication with satellite  18 , as described above. 
     The cams operate separately such that when the telescopic member  208  extends upward, the cams on the internal housing  204  are biting into borehole wall  52  (to prevent internal housing  204  from being pushed down, descending into borehole  50 ) while the cams on external housing  202  are retracted. Once the extension is complete, the cams on external housing  202  bite onto borehole wall  52  to hold and secure communication delivery vehicle  200  at the higher elevation while the cams on internal housing  204  retract, allowing internal housing  204  to be pulled upward into external housing  202 . 
     The present invention preferably uses 3 to 8 spring loaded cams, though a different number of spring loaded cams may be used and still remain within the contemplation of the present invention. Motor  214  used in the present invention is a small, commercially available motor. 
     In another embodiment using longitudinal extension means, and referring now to  FIG. 6 , the plurality of spring loaded cams ( FIG. 5 ) is replaced by a plurality of retractable pins  220  and functions similarly to the embodiment using the telescopic member, as described above. 
     In an embodiment using traction means, and referring now to  FIG. 7 , a motor  308  (or motors  308  and  310 ) are used to turn toothed wheels  314  held against borehole walls  52  by biasing pressure, e.g., spring  316 , developing traction against the ice along surface of borehole walls  52 . Toothed wheels  314  are rotated continuously to hold front end  302  against the ice directly in front of communication delivery vehicle  300 . Alternatively, tooth wheels  314  are turned on intermittently (with ratcheting mechanism  316  capturing upward advancing progress). Communication delivery vehicle  300  then continues advancing forward and melting ice using payload/optics  306  contained within hull  312  until communication delivery vehicle  300  breaches ice surface  36 , allowing communication with satellite  18  to be established. 
     Referring now to  FIG. 8 , in another embodiment employing traction means, a plurality of caterpillar type treads  322  (vertically oriented at equal spacing about the perimeter of communication delivery vehicle  300 ) extend outward from the core of communication delivery vehicle  300 . The plurality of motor driven tracks  322  makes contact with the interior surface of borehole wall  52 . Outward pressure from within hull  312  biases motor driven tracks  322  against the interior surface of borehole walls  52  to maintain contact with the interior surface of borehole walls  52 . This outward pressure against motor driven tracks  322  allow the individual tracks to “bite” on to the ice to provide traction for further upward advancement of communication delivery vehicle  300 . 
     The plurality of motor driven tracks  322  are driven by a drive servo or drive sprocket  324  (similar to the rotating wheel). Preferably, three (3) drive sprockets are used for stability. In using a single wheel or drive sprocket in the caterpillar type tread, the single wheel can fail and will just spin if a void is encountered. The caterpillar tread of the plurality of motor driven tracks  322 , however, spreads the contact surface out providing better traction and stability. 
     Once traction is established, communication delivery vehicle  300  then continues advancing forward and melting ice using melt optic  320  and payload/optics  306  contained within hull  312  until communication delivery vehicle  300  breaches ice surface  36 , allowing communication with satellite  18  to be established. 
     The various embodiments described herein may be used singularly or in conjunction with other similar devices. The present disclosure includes preferred or illustrative embodiments in which a system and method for a laser-powered ice-penetrating communications apparatus for sub-ice submarine missions are described. Alternative embodiments of such a system and method can be used in carrying out the invention as claimed and such alternative embodiments are limited only by the claims themselves. Other aspects and advantages of the present invention may be obtained from a study of this disclosure and the drawings, along with the appended claims.