Ships – Submersible device – Having attitude control
Reexamination Certificate
2000-10-06
2002-04-16
Avila, Stephen (Department: 3617)
Ships
Submersible device
Having attitude control
C114S331000, C114S312000
Reexamination Certificate
active
06371041
ABSTRACT:
BACKGROUND OF THE INVENTION
In recent years there has been considerable interest in and development of submersible craft, as submarines or under sea exploratory and rescue vehicles as all levels of commercial and military research. The underwater frontier remains a huge and much unexplored portion of the earth, with vast riches in minerals, petroleum, seabed, plant, and aquatic life. Further, covering some 70% of the globe, facile access to and use of the underwater environment remains critical to national defense as well as to increased development of the same and its instructive geological lore, habitat study, seabed and seamount mapping, and the like.
Humankind's adventures into ocean depths and the sky above commenced and made great strides in the 20
th
century. Nonetheless, advances in aviation and space have far exceeded progress under the sea. While there are substantial and fascinating similarities in atmospheric air travel and undersea travel, the latter has lagged in research and development, although submarine technology has moved forward from surface air-dependent undersea travel to deep-sea dwelling capability. With greater underwater serviceability, design concerns are shifting from the hydrodynamics of wave resistance and control at or near the surface to the need for uninterrupted hydrodynamic flow about the undersea vehicle, with reduced wetted surface.
Submarines, even in recent years with newer hull designs and nuclear and other power development, still essentially partake of an elongated cigar-like hull configuration with necessary planing surfaces for control, and a fin or sail to contain periscopes and masts.
Such hulls must be carefully designed to withstand deep-sea pressure as well as being volumetrically efficient. A generally flattened hull shape introduces or advances planing or gliding ability, and using the latent forces of gravity and buoyancy to induce a thrust forward. One such is shown, for example, in my U.S. Pat. No. 5,477,798 having a sleek, generally “manta ray” form with remarkable hull strength and carrying capacity.
Further, in exploration and utilization of ocean depths it becomes increasingly important that even the most advanced hull designs be associated with effective and reliable control systems to improve underwater maneuverability, including the ability to hover, or silently glide downwardly or upwardly, to achieve particular needs or missions.
While, as noted, there are certain similarities and relationships between air flight and sea hydrodynamics, it is evident that resistance to fluid flow about a submerged hull is greater than airflow resistance aloft, due to the higher viscosity of water than air. Further, as water is incompressible in sharp contrast to air, a moving undersea body creates more absolute displacement with concomitant greater resistance. As a consequence, the operation of submarines is dependent on ballasting and therefore is more comparable to that of a gas-filled blimp or dirigible, than to heavier-than-air aircraft.
It follows that design and control improvements as to undersea gliding, planing, maneuvering, and even hovering are needed, wherein aircraft are well advanced in these regards. While we have observed for eons the ability of fish to dive, leap, stop, and hover in the water, only recently have we been able to mechanically emulate them. Grade school science classes in past generations were rather inaccurately taught elements of submarine design. The common experiment at the time comprised a partially filled milk bottle containing an inverted test tube with sufficient air above the water level in the tube to float the test tube at the surface. The bottle was stoppered with a connection to a hydrometer bulb. Squeezing the bulb induced sufficient pressure in the bottle to compress the tube's air bubble, permitting additional water to enter through the bottom of the tube, whereby it would sink. The release of external pressure conversely increases the air volume, expelling a like amount of water, allowing the tube to resurface. This experiment in fact illustrates the fish-swimming bladder and is not current in submarine design.
In a submarine comparable air volumes are called “free surfaces”, which present a risk in that loss of buoyancy in a descent is inherently accelerated. For this reason, submarine ballast tanks are always vented before submerging, and inaccessible voids are filled solidly.
This air volume concept was observed in a tropical fish aquarium and revealed that the fish swimming bladders enhanced their performance. By a simple expansion and contraction of its bladder, a “glass fish” was observed to rise, hover, and sink, independently of other movement. Obviously, the bladder's volume was precisely controlled by the fish, allowing it to descend from and return to the surface with little effort and a minimal change in buoyancy. Such capability in a submarine would greatly enhance submarine performance. Improvements in such control ability are necessary to undersea progress at any level.
Various techniques and structures in an effort to improve underwater control of submerged vehicles are typified in the prior art by U.S Pat. No. 3,946,685 to Chadbourne et al, U.S. Pat. No. 3,665,884 to Gustafson, U.S. Pat. No. 3,752,103 to Middleton, U.S. Pat. No. 3,667,415 to Robbins, U.S. Pat. No. 5,129,348 to Rannenberg et al, or U.S. Pat. No. 5,477,674 to Somers et al, U.S. Pat. No. 4,577,583 to Green, or U.S. Pat. No. 3,157,145 to Farris, among others. Also of interest is a J.S.N.A., Japan publication, “Study on the Hydrodynamic Characteristics of Circular Submarines”, which generally suggests the capability of a vessel to glide while submerged. While these patents and publications provide diverse control teachings and systems, and lead toward improved underwater vehicles, the same do not provide a full measure of desirable underwater buoyancy, attitude, ascending and descending glide control, and the like for submarine or like undersea craft with improved laminar hydrodynamic flow. Thus, illustratively, the use in these patents of thrusters or jets for depth or attitude control has the hazard of agitating sea sediments, both disrupting the environment and sharply impeding already restricted underwater visibility. Similarly, the provision of lateral wing-like appendages overlooks the high resistance of wetted surfaces under water.
Buoyancy control is essential to safe and facile operation of all undersea craft, as submarines or submersible exploratory vehicles. Such control permits, for example, the use of the vehicle for recovery of heavy objects from the sea floor. See U.S. Pat. No. 3,292,564, to Lehmann by way of illustration. However, even the most pressure resistant hull is unavoidably compressed in extended deep sea descent, reducing both volume and buoyancy. Minimally, some compensation can be effected by pumping trim and drain systems. Using compressed gas to discharge ballast water, however, is not always desirable as the gas is further compressed by continued descent, is unable to fully expand at depth, and with decreasing effectiveness. In ascent, the compressed gas rapidly expands, which may and does cause a hazardous acceleration to the undersea vessel rising to the surface. The necessarily vented gas in such emergency surfacing would be lost and unrecoverable. See the U.S. Pat. No. 1,686,928 to Wardle and Rannenburg U.S. Pat. No. 5,129,348. There is a need for more rapid and positive buoyancy control.
In another area of underwater control, submarines establish trim with a fore and aft system of weight transfer to attain a desired longitudinal attitude. Weight transfers while underway are compensated for by diving plane angle adjustments until the fore-aft transfer of trimming water is needed to restore the planes to a neutral position. Seawater piping systems function both to admit seawater or to discharge it back to the sea. The efficiency of overboard discharge pumping is significantly reduced as depths increase. See illustratively, the system of Chadbourne U.S. Pat
Avila Stephen
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