US3106179A

US3106179A - Propulsion system for a hydrofoil vessel

Info

Publication number: US3106179A
Application number: US160394A
Authority: US
Inventors: Traksel Johan; Iii William F Hammond
Original assignee: Lockheed Aircraft Corp
Current assignee: Lockheed Corp
Priority date: 1961-12-11
Filing date: 1961-12-11
Publication date: 1963-10-08
Anticipated expiration: 1980-10-08
Also published as: GB978480A

Description

Oct. 8, 1963 J. TRAKSEL ETAL 3,106,179

PROPULSION SYSTEM FOR A HYDROF'OIL VESSEL Filed Dec. 11, 1961 e Sheets-Sheet 1 FIG. 1

INVENTORS JOHAN TRAKSEL WILLIAM E HAMMOND IE 1963 J. TRAKSEL ETAL 3,106,179

PROPULSION SYSTEM FOR A HYDROFOIL VESSEL Filed Dec. 11, 1961 6 Sheets-Sheet 2 FIG..2

INVENTORS JOHAN TRAKSEL WILLIAM F. HAMMONDHI BY a Oct. 8, 1963 .1. TRAKSEL ETAL. 3,106,179

PROPULSION SYSTEM FOR A HYDROFOIL VESSEL Filed Dec. 11, 1961 6 Sheets-Sheet 3 INVENTORS JOHAN TRAKSEL FIG- 6 WILLIAM F. HAMMONDIII gnt Oct. 8, 1963 Filed Dec. 11, 1961 4 TOTAL NET THRUST, E LBS, XIO

J. TRAKSEL ETAL PROPULSION SYSTEM FOR A HYDROFOIL VESSEL 6 Sheets-Sheet 4 3 FT4A-2 ENGINES, FOILBORNE CONDITION SEA LEVEL 80F DAY FIXED NOZZLE |eo \EZREA VARIABLE NOZZLE EXIT AREA I40 20 so as so SHIP VELOCITY, Vo- KNOTS TAKEOFF NET THRUST AVAILABLE VARIABLE EXIT AREA VS FIXED EXIT AREA INVENTORS PK; 8 JOHAN TRAKSEL WILLIAM F. HAMMOND 111 Ageaf Get. 8, 1963 6 Sheets-Sheet 5 Filed Dec. 11, 1961 INVENTORS JOHAN TRAKSEL WILLIAM F. HAMMONDIE Oct. 8, 1963 Filed Dec. 11, 1961 J. TRAKSEL ETAL 3,106,179

PROPULSION SYSTEM FOR A HYDROFOIL VESSEL 6 Sheets-Sheet 6 MAXIMUM commuous [I Em CRUISE, FOILBORNE .so

3 ENG. TAKEOFF FOILBORNE .so NI- 2% z 5 sews. t \zENG TAKEOFF HULLBORNE m 30 IENG.

LU .J N 8 z .20

2 O 30, 4O 8O 90 5O 6O VELOCITY KNOTS REQUIRED NOZZLE EXIT AREA FOR PUMP OPERATION AT CONSTANT EFFICIENCY v INVENTORS 'JOHAN TRAKSEL WILLIAM E HAMMOND JJI FIG-7 United States Patent 3,106,179 PROPULSION SYSTEM FOR A HYDROFOlL VESSEL Johan Traksel, Chatsworth, Calif, and William F. Hammend HI, Nashville, Tenn, assignors to Lockheed Aircraft Corporation, Burbank, Calif.

Filed Dec. 11, 1961, Ser. No. 160,394 21 Claims. (Cl. 11466.5)

This invention relates to a propulsion system for a hydrofoil vessel and more particularly to a new and improved hydrodynamic jet propulsion system for a vessel having a hull, a plurality of hydrofoils depending fore and aft of the hull, a hydrodynamic induction system in selective hydrofoils and a drive means for propelling the hull, when foilborne, on a body of water.

This invention provides a new and improved hydrodynamic jet propulsion system in which a plurality of engines and a corresponding plurality of pumps are disposed in the vessels hull in substantially parallel relationship to each other and in predetermined angular relationship relative to the longitudinal water line of the hull. Water from the body of water flows through a hydrodynamic induction system, which forms an integral part of the lower portion of selective ones of the hydrofoils, into a manifold which distributes the water to the pumps as required. The outflow from the pumps is ducted to individual nozzles extending rearwardly from the pump and angularly relative to the longitudinal water line of the hull and which are located adjacent to the bottom of the hull. The thrust required for lifting the hull on the hydrofoils and for propulsion of the hull while foilborne can be attained with various combinations of flow rate and flow velocities, the latter determining the required pump pressure rise. While it is desirable that the ducting have as large a flow as possible, the internal flow losses must be balanced against the external hydrodynamic drag. The over-all efiiciency is also a function of the ratio of jet velocity to ship velocity. A means of regulating the exit area of the nozzle and flow velocity is therefore provided by this invention.

An equal plurality of turbo-shaft engines are provided in the hull, each having a rearwardly extending driven shaft connected to a respective pump for driving the pump.

A unique arrangement is provided for delivering a head of air to the engines and a unique exhaust system is provided which exhausts air above the hull. An air plenum is provided substantially upstream of the compressor face of the engines into which the air intake is directed, the air intake being directed towards the bow of the vessel. Air intake ducts for the engines have openings communicating with the air plenum, the openings being downwardly directed and in a common, substantially horizontal plane so that any water or impurities suspended in the air is deposited into the plenum before entering the intake ducts communicating with the engines.

Another feature of this invention is the provision for means for preventing cavitation of the water distributed by the pump into the exit nozzles so asto provide a greater efficiency and thrust by the pumps.

It is an obvious advantage to have the pump operate close to its optium efiiciency throughout the entire vessel or ship speed regime. This requires that the water flow be kept at :a fixed relationship to the pump rpm. The total pressure at the Water jet nozzle exit, however, is found to vary with both the flow quantity and the forward speed of the ship. Therefore, a variable nozzle area is required to satisfy the flow conditions.

It is therefore an object of this invention to provide a new and improved propulsion system for a hydrofoil 3,196,179 Patented Get. 8, 1963 vessel for lifting the hull of the vessel to be foilborne and for propulsion of the craft while the hull is foilborne.

Another object of this invention is to provide a new and improved hydrodynamic propulsion system for a hydrofoil vessel which provides improved jet nozzle means exiting water from pumps of the vessel for acquiring improved lift and propulsion of the vessel.

A further object of this invention is to provide a new and improved hydrodynamic propulsion system for a hydrofoil vessel which has improved its intake and exhaust ducting for acquiring the greatest efficiency and most practical arrangement of the drive means operating the pump means.

Yet another object of this invention is to provide a new and improved hydrodynamic propulsion system for a hydrofoil vessel or ship which eliminates or substantially decreases cavitation that could occur in the pump during pumping water through the flow system. i

A further object of this invention is to provide a new and improved intake ducting system for the drive means of this invention for preventing the taking in of moisture or other foreign matter normally suspended in the air received in the air intake.

Another object of this invention is to provide a new and improved hydrodynamic propulsion system for a hydrofoil vessel in which the exit area of the nozzle means thereof is variable and the angle of thrust thereof is adjus-table.-

A general object of this invention is to provide a new and improved hydrodynamic propulsion system for a hydrofoil vessel which overcomes dis-advantages of prior means and methods heretofore intended to accomplish generally similar purposes.

These and other objects of this invention will be more apparent from the following detailed description, drawings and appended claims.

In the drawings:

FIGURE 1 is a plan view of the hydrodynamic propulsion system as incorporated in a hydrofoil vessel;

FIGURE 2 is a vertical, cross-sectional view as taken substantially along the longitudinal center-line thereof;

FIGURE 3 is a vertical, cross-sectional view as taken substantially along the line 33 of FIGURE 2;

FIGURE 4 is a vertical, cross-sectional view as taken substantially along the line 4-4 of FIGURE 2;

FIGURE 5 is an enlarged, vertical, cross-sectional view as taken substantially along the centerline of the pump means of this invention and as indicated by the line 55 of FIGURE 1;

FIGURE 6 is an end View thereof as taken substantially along the line 6-6 of FIGURE 5;

FIGURE 7 is a graph showing the required nozzle exit area for pump operation at constant efiiciency; and

FIGURE 8 is a graph showing the takeoff net thrust available of a variable exit area vs. fixed exit area.

Referring in detail to drawings, there is shown by way of illustration, but not of limitation, a new and improved propulsion system designed and constructed in accordance with this invention and generally designated by the numeral 10. The propulsion system 10 is herein illustrated as adapted for use in the hull 11 of a vessel 12 having a plurality of hydrofoils fore and aft of the hull, a fore hydrofoil being indicated by the numeral 13 and the aft hydrofoils being indicated by the numeral 14.

The vessel 12 is herein illustrated as being provided witha conventional propulsion means generally designated by the numeral 15 which is located adjacent to the stern 16 of the vessel and includes an outboard propeller 17 driven by an inboard mounted engine 18 for propulsion of the vessel 12 when it is hullborne on a body of water, the water line being indicated by the numeral 19.

A propulsion system 10 is useful for assisting the propeller 17 to propel the craft 12 when it is hullborne. However, the principal feature of the propulsion system it is its use for lifting the hull from the surface of the water so as to be foiloorne and for propulsion of the hull while it is foilborne. For this purpose, the propulsion system 10 includes a plurality of nozzles 21, three herein shown, which are angularly disposed relative to the longitudinal water line 19 of the hull 11 for exhausting water from a pump means 22 which receives water from the body of water 19 through a hydrodynamic induction system 23 incorporated in selective ones of the hydrofoils, such as the aft hydrofoils 14.

The pump means 22 includes a plurality of pumps, three herein shown, arranged in substantially parallel relationship to each other and to the longitudinal centerline of the hull, the pumps being driven by drive means 25 which includes an equal plurality of engines 27, each having a driven shaft 24 extending rearwardly and angularly for driving an impeller 26 of its respective pump. The engines 27 are enclosed in individual housings 28, each including an air inlet 29 and an air outlet 31, the engines being preferably of a turboshaft type.

Each inlet 29 is provided with a discrete intake duct 32 which extends forwardly and upwardly and includes an opening 33. The openings 33 are directed downwardly in a plane substantially parallel to the plane of the longitudinal water line 19 of the vessel. The intake openings 33 communicate with the interior of an air plenum 34- which receives a head of air from an air inlet opening 36 which is directed substantially forwardly, towards the bow 37 of the vessel 12.

The outlets 31 of the engine housings 28 are provided with rearwardly, upwardly and angularly directed ducts 37 which terminate at a region above the deck 39 of the hull 11 so as to communicate with ambient air above the hull. Each exhaust outlet 38 is preferably provided with an exhaust deflector 41 which deflects air from the ducts 37 rearwardly towards the stern 16 of the vessel 12.

The exhaust deflectors 41 preferably comprise hooded elements 42 which are hinged as at 43 so as to be pivotable into a retracted position as indicated by the broken lines 42 in FIGURE 2 when the propulsion system 10 is not being used. In such event, a closure means, in the form of a hinged door 44, is provided which may be employed to close the opening when the deflectors are in their retracted position 42'. In the extended position shown in the solid lines 42, in FIGURE 2, the exhaust door 44 is shown as being open, to allow free exhaust of air from the deflector.

The ducts 37 are most conveniently secured in suitable manner, as by clamps or the like (not shown), to the hull 11 and include inlet openings 46 slightly greater than the outlets 31 of the engines 28 so as to form an annular opening 47 around the outlets 31. The annular openings 47 serve to draw ambient air, as indicated by the arrowed line 48, into the ducts 37 so as to provide cooling means therefor.

The pump means 22, as previously mentioned, includes a plurality of pumps 50, three herein being shown, in FIGURE 1, one being shown in detail in FIGURE 5. Each pump includes a housing 51 having a hollow interior 52 in which an impeller 26 connected to its respective driven shaft 24 is rotatable. The interior 52 of each housing 51 is connected to a transverse manifold 53 having inlet passages 54 communicating with the aft hydrofoils 14 which have water inlet passages 56 forming a part of the hydrodynamic induction system of the hydrofoils.

Each interior 52 of the pumps 59' communicates with the manifold 53 to receive a flow of water therein from the hydrodynamic induction system 23. The impeller 26 expels water from the manifold 53 through a diffuser section 56 of the interior 52 and outwardly thereof into a duct 57 communicating with one of the nozzles 21. For greatest efiiciency, the opening of the nozzle 21, as best seen in FIGURE 6 which is an end view thereof, is substantially rectangular in configuration when fully open as seen by the dotted lines of FIGURE 6. The substantially rectangular opening 21 communicates with a cylindrical portion 58 of the duct 57 which is connected to the exhaust of the pump as at 59 and 61 by suitable flanges.

The hydrodynamic induction system, including the water inlet 54, under certain conditions such as low speed takeoff, tends to introduce air in dissolved form, with the water, into the manifold 53 thereby causing cavitation on the impeller blades of the pump when acted on by the'impeller 26. To overcome the cavitation condition, a plurality of passages 62 are annularly disposed relative to the longitudinal centerline 63 of the pump, each including an inlet 64 and an outlet 66 communicating between the outlet of each pump 50 and the interior 52 adjacent to the manifold 53. In this manner, a substantial proportion of the water at the outlet 63 of the pump is recirculated to the pump inlet thereby increasing the water pressure at the pump inlet due to the ejector action. In order to adjust the flow of high pressure water through the passages 62, valves, as indicated at 67, are preferably provided in the passages 62 for varying the flow therethrough.

The exit area of the nozzles 21 is preferably variable so as to vary the flow velocity and balance the internal flow losses against the external hydrodynamic drag, inasmuch as the over-all efficiency is also a function of the ratio of jet velocity to ship velocity. For this purpose, the exhaust nozzle 21 is preferably provided with a valve element 71.

The valve element 71 is illustrated herein in the form of a flap 72 pivotally secured as at 73 to the duct 57 and is pivotable to vary the exhaust nozzle area at 21. For this purpose, a means, herein illustrated as a cylinder 74, is provided having a piston rod 76 connected to a lever 77 which in turn is connected to a pivot point 73 for controlling the position of the flap 72 relative to the opening 21. The cylinder 74 may be operated by any conventional pneumatic or hydraulic system (not shown}; In response to actuation of the cylinder 74, the flap 72 may be pivoted to either a fully open position illustrated in FIGURE 5, or in a position to decrease the area as indicated by the broken lines 72' in FIGURE 6.

The variable nozzle means 71 further provides means for adjusting the angular thrust of the exhaust fluid from the nozzle 21. By varying the angular relationship of the flaps 72, the angular thrust of the water exhausted from the nozzle 21 is varied. It will be readily understood that when the flap 72 is in its uppermost position, the angle of thrust of the exhaust fl-uid out of the nozzle 22 will be directed at a relatively smaller angle relative to the longitudinal water line of the hull whereas, when it is fully open, the thrust is substantially parallel to the centerline of the duct 57 and pump 56. The angular relatiionship of the outlet nozzle to the longitudinal water line of the hull usually rangesbetween 5 and 20, the preferred angle being approximately 9 /2.

The hydrofoils 14 are preferably detachably and pivotally secured for inspection purposes and for lifting out of the Water if desired. For this purpose, each strut of the hydrofoils 14 is secured to the manifold 53 as by complementary flanges 81 secured in suitable manner as by bolts 82, or the like. A pair of braces 83 have their upper ends 84- pivotally secured to the hull 11 and their lower ends pivotally secured at 86 to a strut of the hydrofoils 14. When the flanges 31 are detached, the hydrofoils 14 are pivotable to an uppermost position, above the waterline, for inspection. The forward hydrofoil 13 may be constructed in similar manner for inspection thereof, if desired.

The nozzle area variation required to satisfy the conditions noted above for takeoff and maximum continuous power operation is shown idFIGURE 7. The small variation in area required to maintain constant efficiencyat the takeoff power condition leads to the conclusion that the control system may be simplified to the extent of using fixed nozzle area for takeoff operation. The system performance at takeoff power with a fixed exit area sized for the minimum speed condition of FIGURE 7 is compared with the performance associated with the variable exit area in FIGURE 8. The results indicate that more thrust is provided by the system having the fixed nozzle area. It has been found that as the flow rate increases from its minimum value, the pump efficiency increases. As a result, the decrease in pressure rise across the pump is proportionally less than the increase in flow rate and there is an attendant increase in net thrust. In the case of cruise operation, however, the vessel is already operating at the point of optimum efficiency by definition. The use of a fixed nozzle area would result in some small loss in performance.

Operation of the foilborne propulsion system is therefore as follows. The nozzle control levers are moved from complete shutoff to the takeoff position. The turboshaft engines are started and set at idle thrust. The power lever of the central engine is gradually advanced to the takeoff position. The rate of advance is limited by the pump inlet static pressure, which is indicated at the instrument console with an appropriate red line value. As the ship accelerates, the second and third engine power levers are advanced subject to the same minimum pump inlet static pressure limitation. When the desired cruise velocity is reached, the engine power is reduced to the required cruise level and the nozzle area increased to the appropriate cruise setting. Adjustments in this setting are made as necessary to obtain optimum range or minimum fuel flow.

While there is herein shown and described what is conceived to be the most practical and preferred embodiment of this invention, it is recognized that departures may be made therefrom within the scope of this invention which is not limited to the details disclosed herein but is to be accorded the fuil scope of the claims so as to embrace any and all equivalent devices.

What is claimed as new and desired to secure by Letters Patent is:

1. A propulsion system for a hydro-foil vessel having a hull, a plurality of hydrofoils fore and aft of the hull, a hydro-dynamic induction system in selective ones of the hydrofoils, and a drive means for propulsion of the hull when hullborne in a body of water, the combination with: turboshaft drive means in said hull and having an air intake duct means having an inlet opening directed forwardly towards the bow of the hull, an exhaust outlet directed aftwardly relative to the hull, and a driven shaft extending aftwardly and downwardly in predetermined angular relationship to the longitudinal waterline of said hull; pump means in said hull, said pump means having a hollow housing, an impeller in said housing and connected to said driven shaft for rotation of said impeller therewith, an inlet communicating with the hydrodynamic induction system of the selective 'hydrofoils for receiving water from the body of water, and means defining an outlet nozzle extending rearwardly, downwardly, and angularly relative to said waterline of said hull for exhausting water through said hull from said pump means at a predetermined angle for assisting in lifting of said hull 'when hullborne to be foilborne and for propulsion of said hull when foilborne.

2. A propulsion system as defined in claim 1, wherein the area of said outlet nozzle from said pump means is variable; and including means selectively operable for varying said outlet nozzle.

3. A propulsion system as defined in claim 2, wherein said outlet nozzle is adjustable for angularly adjusting the discharge of the flow thereof and for regulating fiow quantity through said pump means, said outlet nozzle being adjustable in response to varying of said area thereof for adjusting the angular relationship of said outlet nozzle to said longitudinal waterline.

4. A propulsion system as defined in claim 1, wherein said turboshaft drive meansincludes a plurality of turboshaft engines in spaced, parallel relationship to each other and to the longitudinal centerline of said hull, and said air intake duct means includes a plurality of discrete intake ducts communicating between said inlet opening and each of said engines.

5. A propulsion system as defined in claim 4, including means defining an enlarged air plenum intermediate of said intake opening and said discrete intake ducts and communicating therewith, each of said discrete intake ducts includes a substantially horizontal, downwardly directed duct opening; and including means defining a passageway communicating between said intake opening and said air plenum whereby moisture and other foreign particles in the air received in said intake opening is deposited in said plenum while the air itself is communicated to said duct openings of said discrete intake ducts.

6. A propulsion system as defined in claim 3, wherein the angular relationship of said outlet nozzle means of said pump means is approximately 9 /2" to the longitudinal water line of said hull. g

7. A propulsion system as defined in claim 3, wherein the angular relationship of said outlet nozzle means of said pump means is adjustable in a range of from 5 to 20 relative to the longitudinal waterline of said hull.

8. A propulsion system as defined in claim 4, wherein said pump'means includes a plurality of discrete pumps equal in number to said turboshaft engines, each having an impeller in its housing connected to a respective driven shaft of said discrete turboshaft engines for rotation therewith; and including means defining a transverse manifold in said hull and communicating with haid hydrodynamic induction system of said hydrofoils'; duct means communicating between said manifold and each of said housings of said pumps; and wherein each of said pump housings has an exhaust outlet directed aftwardly and downwardly relative to said hull and in angular relationship to said longitudinal waterline of said hull.

9. A propulsion system as defined in claim 8, wherein each of said hydrofoils having an hydrodynamic induction system is detachably connected to said manifold and including brace means pivotally secured at opposite ends to said hull and one of said hydrofoils having an hydrodydynamic induction system, respectively, for selectively pivoting said respective hydrofoils above the waterline when detached from said manifold.

10. A propulsion system as defined in claim 9, includingmeans defining a passageway communicating between said outlet and said inlet of said pump means for recirculating a predetermined volume of discharge from said pump through said pump so as to prevent cavitation in said inlet.

11. A propulsion system as defined in claim 10, wherein said passageway includes a plurality of discrete passage ways annularly arranged around the centerline of said pump means.

12. A propulsion system as defined in claim 10, including valve means in said passageway for varying the flow in said passageway.

13. In a propulsion system for a hydrofoil vessel having a hull, a plurality of hydrofoils fore and aft of the hull for supporting the hull in spaced relationship to a body of water when foilborne and a hydrodynamic induction system in at least one of said hydrofoils, the combination with: turboshaft drive means in said hull and having housing means arranged substantially parallel to the longitudinal centerline of said hull, said housing means having a driven shaft extending outwardly and rearwardly therefrom, an air inlet directed towards the bow of the hull and an air outlet directed towards the stern of the said hull; pump means in said hull operatively connected with said induction system and having impeller means connected to said driven shaft for rotation therewith; and an exhaust outlet nozzle extending rearwardly and angularly downwardly from the pump means relative to the longitudinal waterline of said hull for lifting said hull into a foilborne position and for propelling said hull for- Wardly while foilborne.

14. A propulsion system as defined in claim 13, wherein the exit area of said outlet nozzle of said pump means is variable; and including means selectively operable for varying said outlet nozzle.

15. A propulsion system as defined in claim 14, wherein said outlet nozzle is adjustable for angular adjusting the discharge of the outflow, said outlet nozzle being adjustable in response to varying of said area thereof for adjusting the angular relationship of said outlet nozzle to said longitudinal waterline.

16. A propulsion system as defined in claim 13, including exhaust deflector means for deflecting the exhaust air of said exhaust duct in an aft direction, relative to said hull, and substantially parallel to the longitudinal waterline of said hull.

17. A propulsion system as defined in claim 16, wherein said exhaust deflector means is pivotally mounted relative to said exhaust duct and retractable therein.

18. A propulsion system as defined in claim 17, including closure means on said exhaust duct for selectively closing the outlet thereof when said exhaust deflector is in a retracted position.

19. A propulsion system as defined in claim 13, wherein said drive means includes a plurality of turboshaft engines in spaced, parallel relationship to each other and to the longitudinal centerline of said hull and said air intake duct means includes a plurality of discrete intake ducts communicating between said plenum and each of said engines.

20. A propulsion system as defined in claim 13, wherein said turboshaft drive means includes a plurality of turboshaft engines and wherein said pump means includes a plurality of pumps equal in number to said turboshaft engines, each said pump having an impeller in its housing, each impeller being connected to a respective driven shaft of said turboshaft engines for rotation therewith.

21. A propulsion system as defined in claim 20', including means defining a transverse manifold in said hull and communicating with said hydrodynamic induction system; a plurality of ducts communicating between said manifold and each of said housings of said pumps and wherein each of said pump housings has an exhaust outlet directed afterwardly and downwardly relative to said hull in predetermined angular relationship to said longitudinal waterline of said hull.

References Cited in the file of this patent UNITED STATES PATENTS 2,483,663 Nowak Oct. 4, 1949 2,980,047 Korganoff et a1 Apr. 18, 1961 3,006,307 Johnson Oct. 31, 1961 3,007,305 Hamilton Nov. 7, 1961 3,020,872 Gierczic Feb. 13, 1962 3,055,331 Singelmann Sept. 25, 1962 FOREIGN PATENTS 902,229 Germany Oct. 18, 1954 829,880 Great Britain Mar. 9, 1960

Claims

1. A PROPULSION SYSTEM FOR A HYDROFOIL VESSEL HAVING A HULL, A PLURALITY OF HYDROFOILS FORE AND AFT OF THE HULL, A HYDRODYNAMIC INDUCTION SYSTEM IN SELECTIVE ONES OF THE HYDROFOILS, AND A DRIVE MEANS FOR PROPULSION OF THE HULL WHEN HULLBORNE IN A BODY OF WATER, THE COMBINATION WITH: TURBOSHAFT DRIVE MEANS IN SAID HULL AND HAVING AN AIR INTAKE DUCT MEANS HAVING AN INLET OPENING DIRECTED FORWARDLY TOWARDS THE BOW OF THE HULL, AN EXHUAST OUTLET DIRECTED AFTWARDLY RELATIVE TO THE HULL, AND A DRIVEN SHAFT EXTENDING AFTWARDLY AND DOWNWARDLY IN PREDETERMINED ANGULAR RELATIONSHIP TO THE LONGITUDINAL WATERLINE OF SAID HULL; PUMP MEANS IN SAID HULL, SAID PUMP MEANS HAVING A HOLLOW HOUSING, AN IMPELLER IN SAID HOUSING AND CONNECTED TO SAID DRIVEN SHAFT FOR ROTATION OF SAID IMPELLER THEREWITH, AN INLET COMMUNICATING WITH THE HYDRODYNAMIC INDUCTION SYSTEM OF THE SELECTIVE HYDROFOILS FOR RECEIVING WATER FORM THE BODY OF WATER, AND MEANS, DEFINING AN OUTER NOZZLE EXTENDING REARWARDLY DOWNWARDLY, AND ANGULARLY RELATIVE TO SAID WATERLINE OF SAID HULL FOR EXHAUSTING WATER THROUGH SAID HULL FROM SAID PUMP MEANS AT A PREDETERMINED ANGLE FOR ASSISTING IN LIFTING OF SAID HULL WHEN HULLBORNE TO BE FOILBORNE AND FOR PROLULSION OF SAID HULL WHEN FOILBORNE.