US3301209A

US3301209A - Submersible vessels

Info

Publication number: US3301209A
Application number: US416960A
Authority: US
Inventors: Jr Patton H Caldwell
Original assignee: BAJAMAR OF HOUSTON
Current assignee: BAJAMAR OF HOUSTON
Priority date: 1964-12-01
Filing date: 1964-12-01
Publication date: 1967-01-31
Anticipated expiration: 1984-01-31

Description

Jan 31, 1967 P. H. CALDWELL, JR 3,301,209

SUBMERSIBLE VESSELS Original Filed April 8, 1964 2 Sheets-Sheet l ATTORNEY Jan. 31, 1967 P. H. CALDWELL, JR

SUBMERS IBLE VESSELS 2 Sheets-Sheet 2 originalFiled April e, 1964 INVPIOR. mf Q. 92M@ R. J Ll L E W D L A c H. N o .n A D.

m #SGE ATTORNEY United States Patent 3,301,209 SUBMERSIBLE VESSELS Patton H. Caldwell, Jr., Houston, Tex., assignor to Baja- ?ar of Houston, Houston, Tex., a corporation of exas Continuation of application Ser. No. 358,323, Apr. 8,

1964. This application Dec. 1, 1964, Ser. No. 416,960

7 Claims. (Cl. 114-16) This application is a continuation of a previous application filed on April 8, 1964, Serial No. 358,323, now abandoned.

This invention relates in general to submersible vessels and particularly to vessels having improved apparatus for varying the buoyancy and thus the ascent and descent of such vessels.

To better understand the invention, first consider the buoyancy control methods of the following prior art submersible vessels which are divided into three broad groups. They are: (l) Those having air actuated, sea water ballast tanks, like those of present day military submarines. (2) The initially lighter than water vessels, the buoyancy of which is decreased by adding heavy weights such as steel shot, plates or mercury. The buoyancy is increased by merely droppin-g the weights. This method is typified by .the well known and successful vessel, Trieste. (3) Vessels have, for example, the disadvantage air or gas operated expansible bags.

Each of the above methods has a number of significant disadvantages. The air acutated, sea water ballast vessels have, for example, the disadvantage of operational instabili-ty. Upon descent of the vessel, sea water enters the ballast tanks, varying therate of descent. That is, air left in the tan-ks is compressed by the increasing pressure of the sea water Vas the depth of the vessel increases. This permits more sea water to enter the bal-last tanks, increasing the rate of descent. To ascend, compressed air is discharged into the air tanks to expel the sea water. As the vessel ascends, the decreasing pressure of the sea water permits the air to expand, causing more sea Water to discharge from the tanks; thereby increasing the rate of ascent, or allowing air to escape. Since scientific or industrial underwater vessels should be able to ascend and descend at a controlled rate many times during each operation, this first system is not practicable.

The initially lighter than water vessels of the Trieste type have the disadvantage of operational inllexibility. More specifically, since a light fluid (usually gasoline) is used, heavy weights are used and/or some of the fluid is discharged to cause the vessel to descend. To ascend the weights are dropped, causing the vessel to rise since enough light lluid is retained for this purpose. While this method of buoyancy variation is suitable for scientific vessels making only occasional descents, it is extremely impracticable for vessels that must continuously ascend and descend.

Vessles using the expansible air or gas bladder method of buoyancy variation have basically the same disadvantage as those vessels using air actuated, sea Water ballast tanks. That is, they are operationally unstable due to the extreme variations in the volume of air or gas at different depths and pressures. If a vessel of this type were to rise from 1000 feet in the sea to 500 feet, for example, the volume of the gas would increase by 100 percent. Obviously, descents to great depths are impossible in such vessels unless some means is provided to conof 'operational buoyancy vessels.

sponsive to chan-ges in rlluid pressure and volume.

3,301,209 Patented Jan. 31, 1967 trol the bladder contraction during descent and its expansion during ascent. v

One of the objects of the present invention is to overcome many ofthe disadvantages of the prior art variable More specifically, it is an object of the invention to provide a variable buoyancy vessel which does not require the addition or loss of material during operation, such as sea water or metal weighting material. Another object is to decrease the maintenance problems by excluding corrosive sea water from the inside of the vessel. A further object is to provide an improved buoyancy control system for submersible vessels, said vessel having great stability and thus little need for trim adjustments. Another object is to eliminate air or gas in the buoyancy variation system to remove vthe problems which arise in handling compressible lluids during extreme pressure variations.

In accordance with the foregoing objects, the present invention may be broadly described as a submersible vessel having -a -liquid in a rigid chamber that isolates the liquid from the pressure of the sea Water. The rigid chamber is connected to a second chamber, which has at least a portion thereof that is distensi'ble or llexible and exposed to the surrounding sea water, and thus re- There are suitable means for transferring the liquid from the rigid chamber to the second chamber and then back to the rigid chamber to increase and ydecrease the buoyancy of the vessel. In addition, the geometry and disposition of the Iabove chambers and the vesselis such that the transfer of yfluid between the chambers does not appreciably affect the trim of the vessel.

Since the buoyancy of a vessel immersed in a fluid is a function of its vol-ume, or more correctly, the weight of the lluid it displaces (Archimedes Principle), an increase in the volume of the second chamber of the present invention while keeping mass constant increases the buoyancy of the vessel, causing it to ascend. Conversely, la decrease in the volume of the second chamber, holding mass constant, decreases the buoyancy of the vessel, causing it `to descend. This is readily apparent from an examination lof the mathematical formula,

where w is the specific gravity of the fluid displaced and V is the volume of `the fluid displaced. Therefore, the product wV equals the total Weight of the fluid displaced or the -buoyant force FB, in accordance with Archimedes Principle.

In the present invention the distensible or flexible material of the second chamber acts as a pressure com-pensator which equalizes the pressure of the liquid in the chamber and that of the surrounding sea Water. Since there is no pressure differential lacross the walls of the chamber exposed to the sea water, they are not subjected to large stresses. This permits the yuse of a great variety of materials and constructional forms, giving great flexibility to the design.

The use of a liquid in the second chamber instead of a compressible fluid is important, 'for the liquid, even though it is subjected to the pres-sure of the surrounding sea water by reason of the pressure compensating effect of the distensible material, has a nearly constant volume irrespective of depth unless intentionally transferred to 'the rigid chamber. Consequently, the buoyant force FB will remain almost constant even during great changes in depth.

The foregoing lbroad description of the invention and Y its advantages will become more apparent in the following detailed description and in the drawing in which:

FIGURE 1 is a sectional side view illustrating an embodiment of the invention particularly suitable for either underwater scientific exploration or for underwater industrial operations.

FIGURE 2 is an exploded, fragmentary sectional view which illustrates in better detail the preferred way of attaching the distensible member tothe rest of the vessel shown in FIGURE 1.

FIGURE 3 is a schematic top view showing a hydraulic circuit and related equipment used to provide propulsion, guidance and buoyancy control for the FIGURE 1 embodiment.

FIGURE 4 is a sectional side view of an alternate ernbodiment which is particularly suitable'for the underwater transportation of petroleum products, chemicals or the like. FIGURE 5 is a sectional view taken through the midsection of the embodiment of FIGURE 4. This view illustrates one of the many variations which may be played on the inventive theme and thence demonstrates clearly that the invention in its broadest sense -is not limited to any particular geometrical form.

Although specific terminology is used in the following detailed description forthe sake of clarity, it should be understood that the invention is not limited to such terminology or to the specic structures shown. Rather, the invention encompasses all equivalent devices which operate in a similar manner to accomplish a similar result.

Referring now to FIGURE 1 of the drawing, the numera-l designates a pressure Ihull which in this embodiment is spherical in shape. The spherical shape of hull 10 is selected in the interest of simplicity and availability, but the invention encompasses :many other pressure hull geometries. In communication with. pressurehull 10 is an extension 11, which serves as an entrance to the hull 10 for passengers, cargo or the like. A conventional hatch 121 is attached to pressure vessel 11 and is adapted to sealingly engage it before submersion. To facilitate this operation and the subsequent opening of the hatch 12, there is provided a spring hatch lifter 13 and a conventional handwheel 14.

Below the hatch 12 and upon the extension 11 is secured va hard rubber guard or step 15. Immediately below the guard 1-5 is .secured an outer distensible or flexible member 16, which extends circumferentially around the pressure hull 10. An annular rib 17 is rigidly secured to the pressure hull 10. The distensi'ble member 16 sealingly contacts rib 17 and is retained in that position by tension band 18.. This enables the rapid assembly and disassembly of the distensible member 16 from the pressurehull 10, a feature which simplifies maintenance and handling. It should be noted, however, that in its broadest aspects l 'to a large outer ring 19 which i-s circular and hollow in cross section. Once again the attaching means is an annular rib 20 against which is secured the distensible member 16 'by a tension band 21. As may be seen clearly in FIGURE 2 the annular rib 20 is actually a tubular ring which is secured to the outer ring 19 by an arcuate and annular plate 22. To prevent slippage, the distensible member 16 has an enlarged cross section on its extremity as is designated by numeral 23. A guard rail 24 is pro'- vided to prevent the pinching of distensible member 16 against annu-lar rib 2.0 in the event of accidental collision of the submersible vessel with another object.

A lower distensible member 25 is attached to pressure hull V101 in the same manner as the upper Idistensible member 16, though any means rnay be used. Nevertheless, an

annular rib 26 and a tension band 27 secure the distensible member 25 to the pressure hull 1U. Moreover, an annular rib 28 and a tension band 29 secure the opposite extremity of distensible member 25 to outer ring 19.

The space 30 between the distensib-

le members

16 and 25 is lilled with ia liquid, preferably one lighter than the sea water or the like in which the vessel is suzbmersed to add to its buoyancy. The same liquid iills space 31 which is defined by the di'stensible mem-ber 25 and the plate 32 that extends from outer ring 19 to pressure hull 10. The purpose of the lower distensible member is to provide a measure of safety in the unlikely event that the upper distensible member 16 were accidentally ruptured or torn.

To 'add rigidity to the vessel a plurality of structural ribs 33 extend from the outer ring 19 to a structural tubular ring 34 which surrounds the pressure hull 10. As is clearly illustrated in FIGURE 1, the structural ribs 33 and plate 32 are contoured to the same shape in Vertical cross-section. A secoond set of structural ribs 35 extend .from outer ring 19 to a structural tubular ring- 36 which surroundsthe pressure hull 10. The tubular rings 34 and 36 are joined by a series of transverse ribs 317 that are spaced radially around the pressure hull 10 for emergency. p-ress-urization ttor escape purposes.

additional rigidity of the structure.

Ome or more Plexiglas viewing ports 38 are placed in the pressure hull 10 below the plate 32. Near the lower extremity of the pressure hull 10 is a tubular ring 319' to support the vessel when it reaches the ocean iloor or when transported on the deck of a surface vessel.

The interior of" pressure -hull 10 is dia'ded into two

compartments

40 and 41. The upper compartment 40 is used for passengers, cargo andV supporting equipment such as absorption units (not shown) to iilter water vapor, carbon dioxide and the like from the air. Notice that tubular rings 34 and 36, which contain compressed air, each has valves designated respectively and 44 to control the air inlet from the rings 4into compartment 40 for The use of the rings for the storage of air eliminates the necessity of carrying v'bulky compressed air bottles inside compartment 40. The lower compartment or reservoir 41 contain ling a liquid 50, which has a lower specific gravity than sea Y water, is defined by the floor -42 which sealingly separates orated partions 46 to prevent uncontrolled wave motion in the liquid 50.

The complete propulsion system is shown schematically in FIGURE 3, while FIGURE 1 illustrates only one half of the system for clarity. With reference to FIGURE 1,

Vnotice that a pump 51 (driven by electric motor 52) draws liquid 50 from reservoir 41 through conduit 49, into a valve system 53 and finally back to reservoir 41 through conduit 54. This hydraulic circuit is designated gby the letter a in FIGURE 3. A similar circuit, desigvnated by the letter b, has a pump 51' (driven by motor 52') that feeds the liquid 50 by means of conduit 49 to valve system 53 and then back to reservoir 41 through conduit 54. A third circuit c has a conduit 56 which v connects the valve system 53 to 4the hydraulic motor 48.

` active circuit energizes circuit c to drive` hydraulic motor i 48 and thus propeller 47 in the clockwise or counter-clock* wise direction, depending on the valve -adjustments made in valve system 53.

To increase the buoyancy of the Vessel the valves in system 53 are oriented so that fluid 50 is pumped from reservoir 41 through -conduit 49, to valve system 53, through conduit 57 and hence into space 30 of the lirst buoyancy chamber. Since the pressure output of the pump 51 is greater than lthe hydrostatic pressure of the sea water, the distensible member is forced outwardly, increasing the volume and hence the buoyancy of t-he vessel. As soon as the flow of uid 50 into space 30 is ceased, the distensible member 16 assumes a static position, for it will distend only until the pressure of the liquid 50 in space 30 and the pressure of the sea water are equalized. It should be noted that the arrangement of Kthe valves (not shown) inside valve arrangement 53 enable-s the use of either pump 51 or 51' so that the loss of either one of them will not eliminate buoyancy control.

To decrease the buoyancy of the vessel, the v-alve system 53 is oriented so that

conduits

57 and 54 form a passageway -to permit the iluid 50 to return from space 30 to reservoir 41. Since the pressure of the fluid 50 inside space 30 is subject to the hydrostatic pressure of the 4surrounding sea water, it is at a much higher value than that of the non-pressurized pressure fluid 50 inside reservoir 41. Hence, the ow from space 30 to reservoir 41 is a natural result of merely opening a passageway therebetween.

The use of the lower distensible member 25 is a safety feature allowing the transfer of fluid 50 to space 31 to increase the buoyancy in the event distensible member 16 is ruptured or torn. This is accomplished by orienting the valves of system 53 so that the uid 50 is forced from reservoir 41 to space 31 through conduit 58. To descend the valve system 53 is oriented to allow the uid 50 to return to reservoir 41 lby way of

conduits

58 and 54, as may be seen in FIGURE 3.

It should be noted that in the embodiment shown in FIGURE 1, the transfer of fluid between reservoir 41 and the

buoyancy chambers

30 or 31 does not affect the trim of the ve-ssel. For, as shown, the Acenter of buoyancy and the center of gravity -of the vessel are both located on a vertical axis that -passes through the vcenter of the vessel. In addition, the

chambers

41, 30 and 31 are all symmetrical about the same centrally llocated vertical axis. Thus, there is no change in weight distribution as the uid is transferred between chambers and no trim variation occurs.

Referring primarily to FIGURE 3 to describe the hydraulic system used to guide the vessel, two nozzles 75 and 75 :are located on each side of the outer ring 19, projecting through bumper 55. Each of the

nozzles

75 and 75 has two oppositely directed, substantially tangential outlets, designated respectively 76, 77 and 76', 77'. None of the nozzles are visible in FIGURE 1 since it partially illustrates only one-half the guidance system shown in FIGURE 3. Sea water is drawn by suction 78 through an open valve 79 in conduit 80 by means of a pump 81, driven Iby electric motor 52,'which then feeds the sea water to valve system 82. The valve-s in system 82 are oriented so that sea water is fed to nozzle outlet 77 through conduit 83, or to nozzle outlet 76 through conduit 84. Thus, it may be seen that the components above form an open-ended hydraulic circuit designated by the letter d, having

alternate output paths

83 and 84 to activate `at

will nozzle

76 or 77.

A similar circuit e is defined by suction 78', conduit 80', valve 79', pump 81', valve system 82, conduit 83' and nozzle 77', or conduit 84 and nozzle 76'. Thus, sea water is drawn through lsuction 78 -or 78 by pum-

p

81 or 81 and fed to valve system 82. The valves inside system 82 divert sea water to any two of the nozzles outlets designated 76, 77, 76' and 77'. If sea water is fed to nozzle outlets 77 and 76' the vessel will be rotated in a clockwise direction. On the other hand, if sea water is fed to nozzle outlets 76 and 77', the vessel will be rotated counter-clockwise.

The guidance system is designed with safety in mind, just ias is the propulsion system, for should one of the components in circuit d or e fail for some reason, the remaining active circuit can be used to guide the vessel.

Notice that a plurality of hydraulic lines 102 connect valve system 53 and la housing 103 which contains a series of pistons `104 to alter the angle of hydraulic motor 48 and propeller 47 'with respect to the rest of the vessel. This universal mounting is well known, however, and is provided as an additional guidance means.

The advantages of the present invention are perhaps apparent in view of the description above, but especially noteworthy is the stability of the vessel during ascent and descent. Unlike those submersible vessels which use air actuated, sea Water ballast tanks or those using air or gas operated eXpansible bags, the present invention can be raised or lowered at a uniform rate without need for constantly compensating for volume changes in the buoyant fluid. Moreover, since the addition or subtraction of sea water to the vessel is not required to vary 4the buoyancy, the problem of corrosion and the related maintenance problems are reduced. In addition it is not essential to carry heavy metal weights that must lbe dropped to increase the buoyancy. Also, the vessel and it buoyancy and rigid chambers -have geometries and are positioned such that they are symmetrical about a vertical -aXis (referring here to the FIGURE 1 embodiment) in which the vessels center of buoyancy and center of gravity fare normally located (i.e during the normal operating position of the vessel). Consequently, the transfer of liquid between the buoyancy and rigid chambers does not affect the trim of the vessel since neither the center of buoyancy nor the center of gravity are shifted laterally by the transfer. This is a significant advantage since trim adjustments are unnecessary during ascent and descent, a feature which makes the 'vessel easier to control and more stable. It should also be noted that the vessels shown and described has a very large buoyancy or distensible chamber or chambers at an upper portion of the vessel so that the center of buoyancy is above the center of gravity, a feature making the vessel extremely stable. Moreover, the buoyancy chambers as shown arevery large so that the volume of the liquid therein (if the liquidis lighter th-an sea water) is suliicient to support 4the entire weight of the vessel. This enables rapid rates of ascent and descent since large quantities of buoyancy liquid may be transferred bet-ween the buoyancy :and rigid chambers.

FIGURES 4 and 5 illustrate -a` vessel constructed in accordance with the principles of my invention and having utility for the underwater transportation of petroleum products, chemicals or the like. The numeral 130, designates a plurality of rigid pressure hulls which contain liquid 131. A plate of steel 132 or the like serves as the lower hull of the vessel, though this could be fabricated of a flexible or resilient material. The upper hull 133 is a distensible member land the space .134 is filled with liquid 131 which is pumped from the pressure hulls to distend member 133 and th-us vary the buoyancy of the vessel. A

guidance land equipment compartment 135 is provided atv the bow of the vessel and an engine compartment 136 is provided at the stern. Living quarters 137 are located inside the vessel at approximately its mid-section and a control tower 138 is connected thereto by means of passageway 139. The guidance and equipment compartkment 135, the living quarters 137 and the eng-ine comand the center of gravity of the vessel are both located on a vertical axis that passes through the center of the vessel. The lowermost hull 130 zand the chamber having the distensible member 133 are symmetrical :about a vertical plane that passes fore and aft through the center of the vessel. Also, the centers of the ich-amber and hull lie on the vertical axis that passes through the center of the vessel. Consequently, the weight distribution of the fluid remains constant irrespective of transfer of iiuid between chambers and no trim :adjustment is required. In addition, the laterally placed hulls 130 are symmetrically spaced from the fore and aft vertical plane, and the weight of this iiu'id therein kept equal so that their use does not affect the vessels trim. Thus, this embodiment, like that shown in FIGURE l, has the advantage of eliminating trim variations after transferring the buoyancy control tiuid.

It should be noted that a wide variety of materials may :be used in fabricating the

distensible members

16 and 25. The materia-ls used should be impermeable (to retain the liquid 50) and iiexible, but not necessarily elastic. Notice in FIGURE 1 the position 25' that lower distensible member 25 lassumes when :a portion of the liquid 50 returns to reservoir 41 from space 31. Distensible member 116 will assume a similar position under such circumstances and furthermore, will do so if the liquid 5G flows from space 30 to reservoir 41. The materials used need only be flexible to accomplish this result, like a water-proof cloth. More-over, since there is little pressure differential across the distensible members they need not be very strong. It is advisable, however, that some additional strength be provided -to prevent puncture-s or tears.

A wide variety of liquids may be used to activate the distensible members, for the specific gravity of the liuid need not necessarily be lighter than sea Water. It can be heavier -or only slightly lighter than sea water, like pure water. If it is heavier than sea water, the vessels buoyancy can be increased by the proper sizing of the air-filled chamber 40 of FIGURE l, for example. It is expedient, of course, to use a petroleum based -oil as the liquid since it is readily available and has beneficial lubrication properties. Liq-uids are selected for use in the invention because they are `substantially incompressible, thus avoiding the problems common to vessels using compressible viiuids to lalter their buoyancy. Since incompressibility is the only basic requirement of the liquid, a vast Variety of liquids are practicable, a feature which adds to the versatility of the invention.

I claim:

1. In a submersible vessel, the improvement which comprises:

(a) at least one rigid chamber secured to the vessel and containing a liquid; i

(b) at least one partially distensible chamber communicating with said rigid chamber land being exposed to the sea water that normally surrounds the vessel;

(c) means for transferring at least a portion of the liquid |between said chambers to vary the volume of said distensible chamber and thus the buoyancy of the vessel;

(d) the center of buoyancy and the center of gravity of the vessel both being located on a vertical plane that passes fore and aft through the center of the vessel, with said chambers being symmetrical about said vertical plane and having their centers of buoyancy on a common vertical axis in said plane.

2. The invention as defined by claim 1 wherein said distensible chamber is filled with a liquid lighter than sea Water, said chamber being located at an upper portion of the vessel so that the center of buoyancy remains above the center of -gravity of the fvessel, and said liquid having a volume suicient to support the weight of substantially the entire vessel. v

3. In a submersible vessel, the improvement which comp-rises:

(a) Iat least one rigid chamber secured to the vessel and containing a liquid;

(b) .at least one partially distensible chamber communicating with said rigid chamber and being exposed to the sea Water that normally surrounds the vessel;

(c) means for transferring at least a portion of the liquid `between said chambers to vary the volume of said distensible chamber `and thus the buoyancy of the vessel; and

(d) the center of .buoyancy and the center of gravity of the vessel both being located on a vertical plane that passes fore and aft through the center of the vessel, with said chambers being symmetrical about said yplane and having their centers of buoyancy on a common vertical plane perpendicular to said fore and aft plane.

4. The invention as delined by claim 3 wherein said distensible chamber is filled with a liquidl lighter than sea Water, said chamber being located at an upper portion of the vessel so that the center of buoyancy remains above the center of gravity of the vessel, and said liquid having a volume suiiicient to support the Weight of substantially the entire vessel.

5. In a submersible vessel, the combination of:

(a) a first buoyancy chamber symmetrically disposed.

about a Vertical axis passing through the approximate geometric center of the vessel land sealingly secured thereto, with -at least a peripheral region being |fabricated from a distensible material and secured to the vessel to expose a portion of the exterior of the buoyancy chamber to the sea Water that normally surrounds the vessel;

(b) a rigid chamber secured to said vessel and being symmetric about said axis;

(c) a second at least partially diste-ns-ble buoyancy chamber symmetrically secured about said laxis inte-rior of said first buoyancy chamber to seal a quantity of liquid between the resulting symmetrical space between the irst and second buoyancy cha-mbers; and

( d) means for transferring liquid between the rigid, first and second buoyancy chambers to vary the buoyancy of the vessel.

6. In a submersible vessel, the combination of:

(a) a spherical rigid chamber, a portion of which is partitioned to iform a passenger area and a liquid reservoir which are both symmetrical about the cen.- tral vertical axis of said sphere;

(b) a buoyancy chamber secured to said sphere to be symmetric about said vertical axis to define the hull .of said vessel, at least a portion of which is distensible to enable increase of the volume thereof when liquid tills a-nd expands said chamber and with said volume being sufficient to provide buoyancy to support the entire vessel when filled with a suitable liquid; and

(c) pump means communicating between said chambers to selectively transfer liquid therebetween, whereby the buoyancy of said vessel may be changed without affecting the trim thereof.

7. In a submersible vessel, the combination of:

(a) ya sym-metric rigid chamber, a portion of which is partitioned to form a liquid reservoir and a passenger .area Which are both symmetrical about a vertical plane passing through said chamber;

(-b) a buoyancy chamber secured to said rigid chamber to be symmetrical about said vertical plane, with the centers of gravity of said reservoir and said chambers lying on .a vertical axis passing through substantially the center orf said vessel, With `at least a portion of said buoyancy chamber being distensible to enable increase of the volume thereof when liquid lls and expands said buoyancy chamber, and with said volume beinlg suicient to provide buoyancy to support the entire Vessel when lled with a suitable liquid; and

References Cited by the Examiner UNITED STATES PATENTS MlLTON BIUCHLER, Primary Examiner.

T. M. BLIX, Examiner.

Claims

1. IN A SUBMERSIBLE VESSEL, THE IMPROVEMENT WHICH COMPRISES: (A) AT LEAST ONE RIGID CHAMBER SECURED TO THE VESSEL AND CONTAINING A LIQUID; (B) AT LEAST ONE PARTIALLY DISTENSIBLE CHAMBER COMMUNICATING WITH SAID RIGID CHAMBER AND BEING EXPOSED TO THE SEA WATER THAT NORMALLY SURROUNDS THE VESSEL; (C) MEANS FOR TRANSFERRING AT LEAST A PORTION OF THE LIQUID BETWEEN SAID CHAMBERS TO VARY THE VOLUME OF SAID DISTENSIBLE CHAMBER AND THUS THE BUOYANCY OF THE VESSEL;