ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 213 14.4. Final conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2661. Introduction be introduced, e.g. Reeves deﬁnes the GE as a phenomenon of aerodynamic, aeroelastic and aero- This survey is dedicated to the memory of a acoustic impacts on platforms ﬂying in close proxi-distinguished Russian engineer Rostislav E. Alex- mity to an underlying surface . The term ‘‘extremeeyev who was the ﬁrst in the world to develop the ground effect (EGE)’’ implies a range of relativelargest ground-effect (GE) machine—Ekranoplan. ground clearances of 10% of the chord of the mainHis ﬁrst creation, the top secret project KM became wing or less .known to the western world as the Caspian Sea A wing-in-ground (WIG) effect vehicle can beMonster because of hovering movements of this deﬁned as a heavier than air vehicle with an engine,mammoth craft over the Caspian Sea. The KM which is designed to operate in proximity to anbecame the prototype for many other advanced underlying surface for efﬁcient utilization of the GE.marine vehicles utilizing favorable inﬂuence of theunderlying surface upon aerodynamics and eco- 1.2. Different names of WIG effect craftnomics, Fig. 1. The story of the Caspian Sea Monster has At present many terms exist to designate such aacquired a publicity, which far surpassed that of craft. The names ekranoplan (from the French wordthe Loch Ness Monster. These two tales may appear ´ ekran ¼ screen), nizkolet (low ﬂying vehicle), ekrano-similar to an uninformed reader. In fact, loch means let (vehicle able to ﬂy in and out of GE) originateda lake in Gaelic, and the Caspian Sea is often viewed from Russia (R. Alexeev) . WIG is a popularas an enormous lake. Both monsters were huge and abbreviation of WIG effect vehicle. WISES (intro-tended to avoid the human eye. Actually, only a few duced by S. Kubo, Japan) spells as Wing-In-Surfacelucky ones saw them ‘‘in ﬂesh’’, and both had to be Effect Ship. GEM (Bertelson, USA) stands for GEidentiﬁed from photos. Machine. The terms Flaircraft, Tandem-Aerofoil Boat With the end of the Cold War, the mystery of the were introduced by Gunther Jorg (Germany). The ¨ ¨Caspian Sea Monster exists no more. But the Lippisch craft derivatives developed by Hannobreathtaking technology behind the development Fischer (Germany) are called Airﬁsh. The technologyof large ﬂying ships taking advantage of the surface of air-cushion-assisted takeoff, applied by Fischer,effect at aviation speeds may revolutionize the got an imprint in the term Hoverwing. The vehicles offuture fast sea transportation. Techno Trans (Germany) are known as Hydrow- ing(s). S. Hooker (Aerocon, USA) coined the term1.1. Deﬁnitions of the ground effect and wing-in- Wingship designating WIG vehicles of mammoth sizeground effect vehicles  As per Hooker, this term ‘‘designates very speciﬁcally a ship-sized winged craft that ordinarily In what follows ‘‘the ground effect (GE)’’ is takes off from and lands in water and which ﬂies atunderstood as an increase of the lift-to-drag ratio of high speed’’. The term RAM Wing applies to thea lifting system at small relative distances from an WIG vehicles for which the main contribution to theunderlying surface . More general deﬁnitions may lift is due to stagnated ﬂow under the main wing. A WIG vehicle permanently using power augmentation to enhance the dynamic lift is sometimes called PARWIG. 1.3. Distinctions from existing airborne and waterborne vehicles The WIG effect vehicle differs from a conventional Fig. 1. The KM dubbed ‘‘The Caspian Sea Monster’’. airplane by the relatively small aspect ratio of the
ARTICLE IN PRESS214 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 a ‘‘pancake’’ landing. The transatlantic service of the seaplane Dornier DO-X demonstrated augmentation of the payload and range (1930–1931). Improved ride and handling qualities of conventional military aircraft (F105D, B-58, Avro Vulkan) even at distances exceeding ﬁve span lengths above the ground were regularly experienced, see . The ﬁrst purposefully designed GE vehicle was due to Kaario (Finland, 1935) . His ‘‘Aerosledge Fig. 2. WIG versus airplane (KM versus AN-225 ‘‘Mria’’). No. 8’’ featured a small-aspect ratio wing, leaning upon the skis (skegs) and a swiveling wing, directing the air propeller jet under the main wing. Tomain wing, endplates (ﬂoats), special takeoff and provide additional static stability margin Kaarioalighting gear (takeoff or liftoff aids). The distinc- added two longitudinal rear beams with smalltion from a conventional airplane can be seen from stabilizing surfaces , Fig. 3.Fig. 2, comparing the KM ekranoplan with the A precursor of the power augmentation systemAN-225 (‘‘Mria’’) aircraft of similar size and weight. can be found in the Warner ‘‘compressor’’ airplane The Soviet Military encyclopedia adds to this list (USA, 1928) , Fig. 4. The design was based on aof distinctions of the ekranoplan the ‘‘raised canard conﬁguration and included two powerfullocation of the horizontal tail unit, beyond the fans forcing the air under a dome-like bottom of thelimits of the inﬂuence of the ground and the wing vehicle. The Warner was the ﬁrst to use separatewake, to ensure longitudinal stability’’ . Note that takeoff and cruise engines.the latter feature may degenerate or completely The ram-wing concept was implemented byvanish from some conﬁgurations such as ‘‘tandem’’, Troeng (Sweden, 30s) , Fig. 5. Particular features‘‘ﬂying wing’’ or ‘‘composite wing’’. Contrary to the of Troeng’s rectangular-wing vehicles were: (1)aircraft the WIG vehicles do not have to be enhanced static stability during takeoff with thehermetic. Conventional seaplanes versus WIGs help of special ﬂoats, (2) use of a screw propeller, (3)have: much larger aspect ratio and higher position- use of a small hydrofoil at the trailing edge of theing of the main wing with respect to the hull, i.e. are ram wing to ensure longitudinal stability in theless subject to the action of GE. Seaplanes (except design cruising mode.Bartini’s VVA-14) are of airplane aerodynamicconﬁguration. As compared to the hovercraft whichis borne by a static air cushion, the WIG issupported by a dynamic air cushion that formsunder the lifting wings at large speeds (RAM orchord-dominated GE) or/and by the wing-generatedlift enhanced due to reduction of the down washnear the ground (span-dominated GE). Whilesharing some features with high-powered planingboats, the WIG is supported by dynamic pressure ofthe air whereas the planing boat is supported by the Fig. 3. Kaario’s Aerosledge No. 8.dynamic pressure of the water.2. A brief history of WIG effect vehicles2.1. First inventions and applications based on theGE technology The earliest practical albeit unintentional utiliza-tion of GE belongs to the Wright brothers. Theaviators encountered GE phenomena under thedisguise of what was called a ‘‘cushioning effect’’ or Fig. 4. Warner’s ‘‘Compressor’’ airplane.
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 215 was provided for takeoff and landing with engines cantilevered from the sides of the forward fuselage. The twin vertical and all-movable horizontal empennage is supported from the wing trailing edge by twin tail booms. A single, V-shaped hydrofoil was incorporated into the Lockheed wingship design for landing purposes only. The foil had a Fig. 5. Troeng’s ram wing. span of only 15.2 ft (4.64 m) and a chord of 7.6 ft (2.3 m). The hydrofoil is extended at 150 ft/s (89 knots, i.e. about 165 km/h). Darpa report also describes Northrop Wingship 1.6 M and Douglas Aircraft Wingship-S. The former vehicle has the following main characteristics: TOW ¼ 1.6 mln lb (725 tons), length of 282 ft (86 m), wing span of 141.4 ft (43 m), aspect ratio 2.6, wing loading 206 lb/sq. ft (about 1000 kg/sq m). Structural and empty weight fractions of the vehicle were 32% and 47% correspondingly. The 2 million lb (910 tons) Douglas Aircraft Fig. 6. Ground-effect machine designed by Bertelson. Wingship-S (1977) was supposed to use the power augmented ram (PAR) wing concept. The underw- ing cavity pressure was provided from the exhaust2.2. Projects and vehicles worldwide of the four canard-mounted engines. In the DAW-S the PAR was used at all speeds and the forward Further extension of Kaario’s idea to combine engines were ﬁxed at a certain angle. The underwingfeatures of WIG effect and air-cushion vehicles was pressure is sustained by plain ﬂaps at the rear of theimplemented in Bertelson’s (USA, late 50s–early 60s) wing and a pressurized inﬂatable skirt extendingGEMs , Fig. 6. Similar to Kaario’s design, the vertically along the wing tips. As per the DARPAGEMs had a single engine for takeoff and cruise. report, the DAW-S takes off and lands verticallyThey took off and cruised by means of an air cushion at zero forward speed, thus experiencing nogenerated by deﬂecting the propeller air stream under hydrodynamic forces due to forward motion. Theoff the main wing. Stabilization of the vehicle was wing is mounted ﬂush with the bottom of theprovided by a number of control surfaces: small fuselage to prevent wave impact. The fuselage,forward ﬂaps, mounted right after the propeller, and therefore, is similar to the conventional land planehigh-mounted albeit small tail plane. design and has no seaplane keel, chines or deadrise Lockheed had been involved in WIG craft contours and is designed for ﬂoating loads only. Adevelopment since 1960. In 1963 a small two-seat substantial ski structure is included under the aftboat with a wing ﬁtted with endplates was launched fuselage to assist in the vehicle longitudinal trim(Koryagin). It had two bow hydroskis for better during takeoff and landing. A conventional T-taillongitudinal stability . A similar cutter ‘‘Clipper’’ empennage also maintains trim and stability atwas built in 1965. Beside cutters, Lockheed is forward speeds. Quite a unique craft was developedknown to have studied a large WIG effect ﬂying in the 60s by the Swiss engineer Weiland within hiscatamaran. The vehicle was to be stabilized and contract with the US company ‘‘West Coast’’ .controlled by ﬂap ailerons and a tail unit, compris- Weiland vehicles comprise a twin-hull structure withing of vertical and horizontal rudders. The cargo two large wings of aspect ratio 5 conﬁgured in awas to be transported in the hulls and the wing. tandem. The ‘‘Small Weilandcraft’’ of 4.3 tons was Later, Lockheed-Georgia (see DARPA Report to be followed by a 1000—ton ‘‘Large Weiland-) studied a 1362 million lb (620 tons) wingship, craft’’ with length in excess of 200 m and width ofwhich was designed as a logistics transport capable more than 150 m, Fig. 7. Sufﬁcient attention wasof transporting about 200 tons over 4000 nautical attached to providing efﬁcient takeoff.miles (7410 km) over an open ocean in a sea state 3 As an alternative to hydroskis, Weiland proposedenvironment at a cruise speed of 0.40 Mach. PAR power augmentation. He also introduced special
ARTICLE IN PRESS216 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 Fig. 7. Weiland’s ‘‘Large Weilandcraft’’ Project. Fig. 9. Lippisch X-114. Fig. 10. Kawasaki KAG-3 craft (S. Ando). Fig. 8. TAF VIII-1 tandem vehicle (Gunther Jorg). ¨ ¨ when landing on the water surface, hydrofoils were mounted on the vehicle, two in the front and one atinﬂatable shells on the bottoms of the hulls to the stern. Beside these small craft Lippisch alsoreduce the impact of waves during takeoff. The studied the design of much larger machines.‘‘Small Weilandcraft’’ crashed during the tests One such design was that of a 300-ton GEsupposedly due to lack of static stability. Beginning machine with a 6-engine power plant of 50,000 hp,from 1963 Gunther Jorg in Germany designed and ¨ ¨ able to carry 300 passengers at a cruising speed ofbuilt a series of ground-effect vehicles (TAF ¼ 300 km/h .Tandem-Airfoil-Flairboat) based on the idea of Three types of WIG effect vehicles were developedarranging two stubby wings in tandem , Fig. 8. by the Japanese company Kawasaki (KAG-1, KAG-2He was able to ensure static stability and controll- and KAG-3) [4,10]. The vehicles were designed byability of the vehicle in longitudinal motion by a Ando. The KAG-3 vehicle (takeoff weight of 0.7 ton,proper ‘‘tuning’’ of parameters of the forward and length 5.9 m, width with stabilizers about 6.15 m,rear wings and their design pitch angles. Thereby screw propeller) was built and tested in 1963, Fig. 10.the longitudinal steering control is reduced tothrottle control only. 2.3. Russian ekranoplans Lippisch—a German aerodynamicist, whoworked for the US company Collins Radio— The Russian developments started in the earlyintroduced new WIG effect vehicles based on the sixties almost simultaneously in the Taganrogreverse delta wing planform. In 1963 he built his Aviation Construction Complex headed by Berievﬁrst X-112 ‘‘Aerofoil Boat’’. This and the following and in the Central Hydrofoil Design BureauLippisch craft had a moderate aspect ratio in excess (CHDB) in Nizhniy Novgorod [11–13].of 3 and inverse dihedral of the main wing enabling The vehicles developed in Taganrog under thethem to elevate the hull with respect to the water guidance of Bartini were seaplanes rather thansurface. The reported lift-to-drag ratios were of the ekranoplans in the direct sense of the word. Theorder of 25. Besides, a forward-swept delta wing in idea behind Bartini’s designs was to providecombination with a relatively large high-mounted contact-free takeoff and landing of a seaplane usingtail plane appear to provide sufﬁcient longitudinal the GE.stability in a range of ﬂight heights including Two anti-submarine airplanes named Vertical-cruising close to the ground and dynamic jump takeoff-Amphibia were built possessing improvedmodes. seaworthiness and being able to takeoff and land at In the 70s the series was extended to the X-114 practically any sea state. The development started(takeoff weight of 1.35 tons) which was commis- with the small single-seat seaplane Be-1 built insioned by the German Ministry of Defense, Fig. 9. 1961. It had a low-aspect-ratio main wing betweenIn order to reduce signiﬁcant loads encountered two ﬂoats (hulls) and small side wings. The vehicle
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 217 dihedral which appeared later on SM-8 and the KM itself. Eight marinized turbofan engines of 10-ton maximum thrust each were mounted on the front pylon forward of the main wing to provide PAR Fig. 11. Vertical-takeoff Amphibia (Bartini, Beriev Bureau). takeoff. Another two identical engines were in- stalled at about mid-height of the vertical stabilizerwas propelled by a turbojet engine mounted on the and were used for cruising. After extensive tests inupper side of the main wing. To facilitate liftoff 1967–69, KM showed: efﬁcient takeoff in waves upsurface-piercing hydrofoils were ﬁtted on the ﬂoats. to 3 m, smooth ﬂight, amphibious capability (abilityNext was VVA-14 which had a length of 26 m, of going onto a shallow water area and a beach),width of 6 m, takeoff weight of 52 tons and cruising and good longitudinal stability in the whole range ofspeed of 760 km/h at altitude of 10 km, Fig. 11. design heights. This was essentially a ﬂying catamaran. Its basic The next vehicle of the KM family was ‘‘Orlyo-part was a small-aspect-ratio center-wing of rectan- nok’’ (1973, with 120-ton takeoff weight, length ofgular planform bounded by two hulls. The fuselage 60 m, aspect ratio 3 main wing), Fig. 12.was mounted toward the front part of the wing Differently from KM, ‘‘Orlyonok’’ had two PARalong its axis and two side wings were ﬁtted behind engines of 10-ton static thrust ‘‘hidden’’ in the bowthe center of gravity (CG). The liftoff was to be part of the fuselage. Cruise propulsion was providedprovided by 12 engines on the center wing. In fact by a 16-ton static thrust turboprop engine, mountedthese were power augmentation engines. Two D- at the intersection of the vertical stabilizer and the30 M turbofan cruise engines were located rear- tail plane, and two counter-rotating variable pitchwards above the central wing so that they were propellers with diameter in excess of 6 m. Theprotected against water ingestion. Also there were turboprop engine not only ensured higher efﬁciency14-m long inﬂatable pontoons ﬁtted on the bottom than the jet, but also the variable pitch propellersof the side hulls. provided remarkable low-speed maneuverability in However, the main developments of what is now the PAR mode.called ekranoplan were made in CHDB by Alex- In 1987, the next representative of the KM familyeev’s team which viewed the vehicle’s ﬂight close to was launched—a missile carrier ‘‘Loon’’ (400-tonthe underlying surface as the main regime of takeoff weight, 450 km/h cruising speed, length ofoperation. The ﬁrst piloted ekranoplan SM-1 of 3- 74 m, main wing aspect ratio exceeding 3). Itston takeoff weight was based on a tandem scheme peculiarity was that (due to the missile launching(1960). This concept was later discarded because of mission) all eight engines (static thrust of 13 tonsthe high speed of detachment from the water, each) were mounted on the bow pylon to serve both‘‘stiffness’’ of ﬂight and narrow range of pitch as PAR and cruise prime movers, Fig. 13.angles and ground clearance for which this conﬁg- Another type of Russian WIG effect vehicles isuration was longitudinally stable. known as Dynamic Air Cushion Ships or DACS The 5-ton SM-2 prototype had a new conﬁguration, [12,14]. The DACS concept was set forth by Alexeevcomprising a low-ﬂying main wing and highmounted in the late 70 s with designs accommodating from 8tail plane. Another revolutionizing novelty of this to 250 passengers. The basic element of DACS is avehicle was its capability to pressurize the air under wing of small aspect ratio bounded by skegs (ﬂoats)the main wing by the exhaust of the engines located and rear ﬂaps to form a chamber. The dynamic airupstream in the front part of the vehicle. Thusemerged a wing-tail conﬁguration with PAR consti-tuting the basis for the following series of ekranoplansof the ﬁrst generation. As a result of a huge engineering effort involvingdevelopment and tests of many self-propelled modelsthere evolved a prototype KM with takeoff weight of550 tons, length in excess of 90 m, cruise speedsabove 500 km/h, main wing of aspect ratio 2, Fig. 1. The ﬁrst small-scale KM prototype was the modelSM-5 although its tail plane did not feature a Fig. 12. Ekranoplan ‘‘Orlyonok’’ (Alexeev-Sokolov).
ARTICLE IN PRESS218 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 Research Center (CSSRC) in 1967 [15,16]. Since then, during more than 30 years a total of nine small manned test vehicles have been designed and tested on lakes and in coastal waters (see table). The XTW series was based on a wing-tail conﬁguration with the main wing having forward sweep as in Lippisch Fig. 13. Ekranoplan ‘‘Loon’’ (Kirillovykh). designs, Fig. 15. In 1996 the CSSRC reported developing the XTWII, XTW-III and XTW-IV WIG effect craft, Fig. 15. A typical craft of this series is XTW-4 which was slightly modiﬁed from XTW-2 to comply with speciﬁc requirements from sea trials. This 20- passenger WIG effect ship was ﬁrst tested on the Changjiang River in the autumn of 1999. The vehicle comprises: a major hull (ﬂoat), the main Fig. 14. Dynamic air cushion boat ‘‘Volga-2’’. wing supported by two minor ﬂoats, two vertical stabilizers carrying a high-mounted tail plane. To a certain extent the vehicle can be ascribed to wing-cushion in the chamber under the wing is formed by tail conﬁgurations. The main wing features themeans of blowing of the air with special fans forward sweep, reminiscent of the Lippisch deltaw-(propellers) mounted in front of the vehicle. The ing concept. Two P&WC PT6A-15AG turbopropoverpressure under the wing equals or exceeds the engines with MT’s 5-bladed adjustable pitch pro-weight of the vehicle even at zero or small speed. As pellers are mounted at the leading edge of the mainthe speed increases, the augmentation of lift is wing. Thus, the slipstream is efﬁciently used to assistadditionally enhanced due to the dynamic head of takeoff. Also, the WIG effect sixseat vehicle SDJ 1the oncoming air. For DACS the blowing (power using a catamaran conﬁguration was developed .augmentation) is a permanent feature present both In early eighties another Chinese organization,in the cruising and takeoff–touchdown modes. MARIC, started developing what they calledNumerous tests carried out at the CHDB showed AWIG (Amphibious WIG) . About 80 modelsthat efﬁciency of DACS is similar to that of were tested to study optimal wing proﬁles, conﬁg-hydrofoil ships. At the same time, the speed of uration of the air channel, position of the bowDACS far exceeds that of both the hydrofoil ships thrusters, arrangement of the tail wing, etc. A self-and the ACVs. The ﬁrst practical vehicle of DACS propelled radio-controlled model of 30 kg wastype was the Volga-2 cutter, Fig. 14. tested on Din-San lake in a suburb of Shanghai. This 2.7-ton craft has a length of 11.6 m, width of As the model showed acceptable performance,7.65 m and height of 3.6 m. The range of cruise MARIC proceeded to the development of the largerspeeds of Volga-2 is from 100 to 140 km/h. The craft AWIG-750 with a maximum TOW of 745 kg,vehicle is propelled by the ducted air propellers length 8.47 m, span 4.8 m, height 2.43 m, Fig. 16.mounted ahead of the wing. Inclination of their axes The power plant included internal combustionand use of special hinged vanes serves to provide engines: two for lift and two for propulsion of theboth power augmentation and horizontal thrust. craft. Each engine drove a ducted thruster type DT-The main lifting wing of the craft is almost square 30 of 30 hp rated power at 6000 rpm. The vehicleand has S-shaped sections to enhance the long- was able to takeoff in waves of 0.5 m and had aitudinal stability. As a result, the latter turns out tobe sufﬁcient in spite of the relatively small tail area.3. Recent projects3.1. Projects and prototypes produced in China Development and design of WIG effect craft inChina was started in the China Ship Scientiﬁc Fig. 15. XTW-1 vehicle (CSSRC, Wuxi, China).
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 219 In 1990 Fischer Flugmechanik tested a 4-seat vehicle Airﬁsh-3, which was 2.5 times heavier than Airﬁsh FF2, ﬂew at a speed of 120 km/h and was able to cover a range of 370 km , Fig. 17. With a length of 9.45 m and a width of 7.93 m, the vehicle had an operational clearance ranging from 0.1 to Fig. 16. AWIG-751 (MARIC, China). 1 m. Although the craft was tailored for use in GE, it could perform temporary dynamic jumps climbing to a height of 4.5 m.maximum speed of 130 km/h. It demonstrated the A design based on the Airﬁsh series formerlyexpected (amphibious) capability of passing from developed by Fischer Flugmechanik has re-emergedthe water to the shore and back. in Flightship 8 (FS-8 initially designated as Airﬁsh 8) In 1995, the China State Shipbuilding Corpora- , Fig. 18. The FS-8 was developed in Germanytion commissioned the R&D for a 20-seat AWIG- by Airfoil Development GmbH and made its751 under the name ‘‘Swan-I’’ to MARIC and the maiden ﬂight in the Netherlands in February 2000.Qiu-Sin Shipyard , Fig. 16. With its TOW of 2325 kg, length of 17.22 m, width of The vehicle which was completed by June 1997 15.50 m and height of 4 m the Flightship-8 carries 8had a TOW of 8.1 tons length–width–height people, including two crew. The wave height atdimensions of 19 Â 13.4 Â 5.2 m3 and a maximum takeoff is restricted to 0.5 m, but when cruising thecruising speed of 130 km/h in calm water. It had vehicle can negotiate 2-m waves. FS-8 is made ofthree aviation-type piston engines: two HS6E FRP. With an installed power of 330 kW it has aengines of 257 kW each for PAR lift and one cruising speed of about 160 km/h and a range ofHS6A engine of 210 kW for propulsion. The PAR 365 km. The customer is the Australian Companyengines drove two bow ducted 4-bladed air propel- Flightship Ground Effect Ltd. whose branch Flight-lers and the cruise engines drove a two-blade ship Australia conducted trials of the vehicle invariable pitch propeller. As compared to the Australia. The R&D and production work isprevious AWIG-750 it had several new features, monitored by Germanischer Lloyd with regard toincluding: increased span of the main wing, classiﬁcation of the craft.composite wing, combined use of guide vanes and A larger Flightship-40 (FS-40) dubbed Dragon-ﬂaps to enhance longitudinal stability, CHIBA Clipper is being designed for up to 40 passengers incomposites to reduce structural weight. the commuter version for an equivalent payload of 5 The tests conﬁrmed overall compliance with tons in alternative conﬁgurations. This larger craftthe design requirements, but showed some dis- has a length of 30 m, and the wingspan of 25 m canadvantages, namely, too long shaft drives of the be reduced to 20 m for onshore handling by foldingbow propellers, lower payload and lower ground winglets. The main construction material is alumi-clearance than expected. The follow-on vehicle num, and the Pratt and Whitney turboprop-dieselAWIG-751G (Swan-II) had increased dimensions,a modiﬁed PAR engines layout and an improvedcomposite wing.3.2. Projects and vehicles developed in Germany Hanno Fischer, the former technical director of Fig. 17. Airﬁsh 3 (Hanno Fischer).Rein-Flugzeugbau, set up his own companyFischerﬂugmechanik and extended the Lippischdesign concept to develop and build a 2-seatsports vehicle designated as Airﬁsh FF1/FF2 ,Fig. 17. Unlike X112 and the following X114, the Airﬁshwas designed to ﬂy only in GE. It was manufacturedof GRP and reached a speed of 100 km/h at just halfthe engine’s power during tests in 1988. Fig. 18. Airﬁsh 8—Flightship 8 (Hanno Fischer).
ARTICLE IN PRESS220 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283engines developing 1000 kW will increase the cruis-ing speed to about 225 km/h. Maximum takeoffwave height is 1.2 m and increased wing span allowsover-water operation in 4 m seas. The originatorsof the FS-8 design Fischer Flugmechanik andAFD Aerofoil Development GmbH have recently Fig. 20. ‘‘Hydrowing’’ vehicle of Technotrans.announced a proposal to produce a new craftHW20  combining WIG effect and staticair-cushion technology (see paragraph 9.2). Thedesign of HW20 (Hoverwing) employs a simplesystem of retractable ﬂexible skirts to retain an aircushion between the catamaran sponsons of themain hull conﬁguration. This static air cushion isused only during takeoff, thus enabling the vehicle Fig. 21. Marine passenger Ekranoplan MPE-400 (D. Synitsin,to accelerate with minimal power before making a T&T—ATT—ATTK).seamless transition to true GE mode, Fig. 19. Techno Trans e.V. was established in 1993. Thecompany started its activities by performing quite parts: the one (central) taking advantage of theextensive tests of Joerg tandem craft prior to power augmentation mode, and the one (side wings)launching their own WIG effect craft, project adding efﬁciency and longitudinal stability in cruise.Hydrowing  with the goal to build an 80- Provision of stability in this case has three majorpassenger ferry. In the mid-nineties they built a 2- ingredients: special proﬁling of the central part ofseater prototype (Hydrowing VT 01) propelled by the main wing, horizontal tail (albeit relativelytwo unducted propellers. The vehicle had a TOW of small), appropriate geometry and position of the812 kg, length of 9.87 m and width of 7.77 m. With side wings. The designs, exploiting these features,installed power of 90 kW it could sustain a cruising are those of the MPE (Marine Passenger Ekrano-speed of 120 0 km/h and could operate in waves of plan) series (Designer General D. Synitsin), ranging0.4 m. The main wing of the vehicle had S-shaped in TOW from 100 through 400 tons , Fig. 21.cross-sections for better stability, and a high- The MPE-400 project (1993) has a TOW of 400mounted horizontal stabilizer supported by two tons, length of 73 m, width of 53 m and height ofvertical ﬁns at the stern . 20 m. It is intended to carry 450 passengers. It The present project of Techno Trans is designated features an overall aspect ratio of 4.5. For betterHydrowing 06, Fig. 20. It has a TOW of 2.3 tons, stability the central wing sections were S-shapedinstalled power of 210 kW, a length of about 14 m, a resulting in considerable reduction of the area of thewidth of 11 m and a cruising speed of 125 km/h. It tail plane. The latter constitutes 27% of the area ofalso adopts the forward sweep feature of the the main wing. For KM this factor was 50%.Lippisch designs, has both air and water rudders, Because of the aforementioned speciﬁc features theand is equipped with a small hydrofoil for takeoff ekranoplans of MPE type can be assigned to theassistance. second generation.3.3. New vehicles and projects in Russia 3.3.2. Amphistar-Aquaglide series Ekranoplan Amphistar was developed and built3.3.1. Marine Passenger Ekranoplans by the company ‘‘Technology and Transport’’ A composite wing conﬁguration implies func- (Director and principal designer D. Synitsin) intional subdivision of the craft’s lifting area into two 1995 . In 1997 this vehicle was awarded the certiﬁcate of the Register of Shipping of the Russian Federation as a cutter on dynamic air cushion. The maximum TOW is 2720 kg, its L Â B Â H dimen- sions are 10.44 Â 5.9 Â 3.35 m3. At cruising speed of 150 km/h it has a range of up to 450 km. Seaworthi- ness is about 0.5 m. The turn radius at cruisingFig. 19. Hoverwing-20 with a static air-cushion liftoff system. speed is about 65 hull lengths. In water the turn
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 221Fig. 22. Aquaglide-5 wing-in-ground effect vehicle (Synitsin,ATT-ATTK). Fig. 24. (a) Transport Amphibious Platform (project, CHDB). (b) Transport Amphibious Platform Aquaglide-60 (project, ATT- ATTK). Fig. 23. Aquaglide-50 (project, Synitsin, ATT-ATTK). and a bow cockpit. The propulsion engines are mounted on the tail plane. The claimed advantages of the TAPs are high-speed (up to 250 km/h),radius is about a hull’s length. A modiﬁed version of amphibious capacity, ability to carry superheavythe vehicle has recently appeared under the name and oversized cargoes, high weight efﬁciency (up toAquaglide, Fig. 22. Synitsin developed a scaled 40–50%) due to a structural scheme simpliﬁedup series of Amphistar-Aquaglide-type vehicles, versus hovercraft and WIG craft, low speciﬁc loadFig. 23. Another example of larger dynamic on the supporting surface of the skegs (close to thatair-cushion vehicles scaled up from the Volga-2 of a skier on a snow surface), making the vehiclecutter is a 90-passenger high-speed river craft ecologically friendly.Raketa-2 designed to cruise at a speed of 180 km/h The TAPs  are claimed to have advantagesfor ranges up to 800 km, and powered by a gas compared to hovercraft: 2 times larger speed; highturbine. CHDB has also developed a conceptual seagoing qualities providing stable motion in roughdesign of a 250–300 passenger dynamic air-cushion seas without ﬂexible skirts; high cargo-carryingship Vikhr-2. capacity and weight efﬁciency; relatively simple structure featuring no complicated multi-element3.3.3. Transport Amphibious Platforms (TAP) power plant with reduction gears, transmissions This new concept of fast water amphibious and hover fans. The TAP aerodynamic efﬁciencytransport developed by the CHDB and ATT-ATTK (lift-todrag ratio) is 10–12 at a speed of the order ofhas speeds in the range of those of a hovercraft and 135 knots.WIG effect craft, Figs. 24a and b. Like the DynamicAir Cushion Craft the TAP are supported both by 3.4. Projects and vehicles in the USAthe dynamic head of the oncoming ﬂow and by thatof the jet exhaust of the bow PAR engines. At the In the early 90s, a US company named AERO-same time, the TAP moves in constant contact with CON developed a project Aerocon Dash 1.6 ,the water surface (note that the ATT-ATTK Fig. 25. This mammoth Wingship had the followingconcept of TAPs admits gaps between the vehicle physical characteristics: TOW ¼ 5000 tons, payloadand water surface). High efﬁciency is achieved fraction of 0.3588, wing loading of 258 lb/sq. ftthrough a proper combined use of the aerodynamic (1260 kg/sq m), cruise speed of 400 knots (740 km/h),GE and high hydrodynamic quality of the elongated cruise altitude of 12 ft (3.66 m). As underlined inplaning hulls (ﬂoats). The main structural compo- the DARPA report, a unique characteristic of thenent of the TAP is a cargo platform with long- Dash 1.6 is its land overﬂight capability. A ﬂightitudinal side skegs, the bow pylon with PAR engines altitude of 6000 ft (1830 m) and a speed of 400 knots
ARTICLE IN PRESS222 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 Fig. 26. Lockheed Martin SEA (surface-effect-aircraft) concept. Fig. 25. Aerocon Dash 1.6 ‘‘Wingship’’ (Stephan Hooker). 400 knots and a global range with 400 tons ofwere assumed for the transit over land barriers. payload.Whereas in free ﬂight lift-to-drag ratio was esti- As reported by Boeing Frontiers (online, Septem-mated as 15, in design GE mode the expected value ber 2002, vol. 01, issue 05), a high-capacity cargoof aerodynamic efﬁciency was more than 32. plane concept dubbed Pelican is being developed In recent years Lockheed Martin Aeronautical currently by Boeing Phantom Works , Fig. 27.Systems investigated the development of what they It has a large-aspect-ratio main wing, a wingspancall Sea-Based Aircraft . LMAS calls for a move of 500 ft (153 m), a wing area of more than an acreto hybrid aircraft compliant with a modern doctrine (0.4 ha), twice the dimensions of the world’s currentof rapidly moving smaller and lighter forces largest aircraft An-225, and it can transport up toanywhere in the world, or standoff power projection 1400 tons of cargo.on demand anywhere in the world. The LMAS It has a long trans-oceanic range and can ﬂy assearch for appropriate hybrid solutions resulted in a low as 20 ft above the sea (span-based relativefamily of designs. These include: seaplanes, ﬂoat- ground clearance of the order of 20/500 ¼ 0.04), butplanes and WIG-like combined surface effects it is also able to ﬂy at heights of 20,000 ft or higher.aircraft—SEA, Fig. 26. Intended for commercial and military operators LMAS concludes SEA is an emerging more who desire speed, worldwide range and higheffective alternative to WIG craft. throughput. As indicated by John Skoupa, senior Whereas the latter manager for strategic development for Boeing advanced lift and tankers ‘‘The Pelican stands as the only identiﬁed means by which the US army can is a ship that ﬂies (speciﬁcally, the Russian achieve its deployment transformation goals in Ekranoplans), deploying one division in 5 days or ﬁve divisions has little altitude or maneuvering capability, in 30 days anywhere in the world’’. It can carry 17 is sea-restricted, M-1 main battle tanks on a single sortie. has long takeoff roll, Other applications are: as mother ship for should be very large for the mission objectives, unmanned vehicles, or as potential ﬁrst-stage plat- has no signature reduction capacity form for piggybacking reusable space vehicles to the former appropriate launch altitude. is an aircraft which operates on water, The (extreme) GE provides larger range and has aircraft altitude capability, efﬁciency. The ‘‘Pelican’’ is foreseen to ﬂy 10,000 has shorter takeoff roll than pure WIG aircraft, nautical miles over water with a payload of 1.5 may be shaped for signature reduction, million pounds. As ﬂying in GE requires the latest has reduced risk due to rogue waves and surface ﬂight control technology, the vehicle will be obstacles. equipped with reliable systems providing precise, automatic altitude control and collision avoidance. SEA combines multiple surface effect technologies It is worth mentioning that Pelican is a deja vuin a Sea-Based Mobility Hybrid Aircraft design— concept. In the late sixties, Boeing was conductingWIG, seaplane and hydroplane hull shaping. surface- intensive developments of an anti-submarine GEeffect ship hull shaping, ram and power-augmented vehicle named ‘‘Lowboy’’ conﬁgured as an airplanelift, powered circulation lift and ski ship. According with low-mounted high-aspect-ratio wing. Theto LMAS, such a concept is viable with the current Pelican has been offered by Boeing as part of aaircraft technology, and would provide speeds up to system solution that would include the C-17 Globe
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 223Fig. 27. Cargo plane-in-ground effect concept ‘‘Pelican’’ (Boeing). Fig. 29. Hydrofret 2 (concept, G. Gazuit and Y. Goupil).master III transport, the CH-47 Chinook helicopterand the advanced theater transport. for extending the airﬁelds to water surfaces. In fact, the authors of the concept, Gazuit and3.5. Other projects and developments Goupil  advocate a speciﬁc formula for a sea- plane, which features catamaran hull tandem wings3.5.1. Sea-Bus project (European Community, large wing-like fuselage use of static (air cushion) andsurface-piercing hydrofoil-controlled WIG effect dynamic GE.conﬁgurations) The concept is proposed in two versions. The ﬁrst The Sea Bus (project, 1997–2000) is basically a is a ram-wing catamaran complemented by a large-large wing operating in GE just above the water aspect-ratio lifting forward wing (side wings) and asurface which also features hydrofoils and a water- highly mounted large-aspect-ratio tail plane. In thejet propulsion system , Fig. 28. The hydrofoils alternative version the tail wing is replaced by aare positioned in a trimaran arrangement, and are large-aspect-ratio rear wing (side wings) forming aconnected to the air wing by vertical surface tandem with the forward wing, Fig. 29.piercing struts. Separate V-shaped takeoff hydro- Deja vu: a seaplane design, combining a ram-foils assist in generating lift force, thereby decreas- wing catamaran hull with a wing of large aspecting the takeoff speed at which the ﬂoating hulls of ratio (side wings), was proposed by R. Bartini inthe vehicle rise from the water. The main purpose of early 60s and is known as a Vertical-takeoff-the hulls is to provide buoyancy in ﬂoating Amphibia (VVA-14). The goal was to provideoperations at low speed in harbors and in takeoff contact-free takeoff and landing of the seaplane.and re-entry operations. Due to the large water The Hydrofret differs due to the second large-density, the control of the vehicle by hydrofoils aspect-ratio wing element, highly mounted orbecomes more efﬁcient in terms of shorter response located at the plane of the ram wing. A commontime. gain in both versions with respect to a ram-wing GE It was hoped that the longitudinal stability would machine is that the overall aspect ratio of the systembe ensured by hydrofoils which implies redundancy is enlarged due to high-aspect-ratio wing elements.of aerodynamic tail planes. It was required that the It appears that by properly adjusting relativeSea-Bus should carry 800 passengers and 100 cars at position, pitch angle and areas of the large-aspect-a cruise speed of 100 knots over a distance of ratio elements, one may provide static stability of850 km. One of the key problems is the cavitation the vehicle when ﬂying close to the water surface.occurring on the hydrofoils at speeds exceeding 40 Additional reserve in this respect lies in specialknots. proﬁling of the ram wing in the longitudinal direction (S-shaping and similar measures). However, there may occur stability problems in the transitional height range. Besides, while the highly mounted tail in the ﬁrst version of the Hydrofret could have been seen as an unpleasant necessity for GE machines proper, it appears to be somewhat clumsy in free air ﬂight which constitutes Fig. 28. European Sea Bus project. the main operational mode for the airplane.3.5.2. Hydrofret concept 3.5.3. Multihulls with aerodynamic unloading Proposed as a solution for the airport congestion A certain amount of work has been done on usingproblem, the Hydrofret (Hydrofreight) concept calls the unloading effect of the presence of sea surface
ARTICLE IN PRESS224 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283on high-speed catamarans. Doctors call such developed by Professor Syozo Kubo from Tottoricatamarans ‘‘ekranocats’’ . University and built with support of Mitsubishi Somewhat earlier a similar concept of a Ram [30,31]. The m-Sky 1 (Marine Slider) ﬁrst ﬂew inAugmented Catamaran (RAC) was also proposed 1988. This 1-seater craft had a square platformby Gallington  who found that (obviously) the and endplates, TOW of 295 kg and L Â W Â Hmost efﬁcient power augmented craft should be dimensions of 4.4 m Â 3.5 m Â 2 m. Powered by atouching water very little and cruise at high speeds. 64 hp engine driving a 4-bladed ﬁxed-pitch airIn fact the RAC concept is a tradeoff between propeller, the craft could develop a cruising speedincreased drag of the side plates penetrating the of 82 km/h.waves and the loss of lift and propulsion associated After the m-Sky 1 vehicle a more sizable 2-seat m-with the lateral leakage of air. Sky 2 vehicle was developed and built by Mitsubishi As reported, Incat Tasmania has been conducting under the supervision of Kubo , Fig. 32. Whiletests of a manned model high-speed craft, ‘‘the almost similar to the previous craft, it had certainWing’’, that employs the WIG effect concept to distinctions: both air and water rudders, a wingprovide additional aerodynamic lift. Results of the structure made of aluminum pipes covered withmodel tests have shown speeds in excess of 60 knots. cloth.The test vessel is conﬁgured with three hulls (central The project of a 8-seater ‘‘ﬂying wing’’ type crafthull forward, outer hulls aft) supporting a delta started in 1998 by S. Kubo and H. Akimoto (ofwing superstructure, Fig. 30. Tottori University) with ﬁnancial support from A concept of a very fast ‘‘semi-WIG’’ wave-piercing Fukushima Shipbuilding Ltd and additional fund-trimaran (WPT) making use of aerodynamic unload- ing (of the tests from April 2000 through Apriling of the hulls was developed by Dubrovsky, Fig. 31. 2001) from Shimane Prefecture , Fig. 5.2.19. The concept of what they call Air-Assisted Vessel Takeoff weight 2.5 ton, dimensions L Â B Â H ¼Solutions has been explored in a joint effort by 12 Â 8:5 Â 3:7 m, cruising speed of 150 km/h, theEffect Ships International (ESI) and SES Europe expected range—over 350 km. Two water-cooledAS (SE). ESI claims to have patented Air Supported reciprocal engines rated 250 PS each, installed in theVessel technology for both monohull and multihull middle of the central body, drive two three-bladedvessels in 2002. They see it as an innovative propellers of 2 m diameter. The section of the mainapproach to reduce hull resistance and improve wing is Munk M6R2 for the upper side and CJ-5 forperformance—suitable for various naval and com- the lower side. The resulting camberline of the wingmercial applications. is S-shaped and the thickness is 9%. The center body of the ship (hull, cabin and root parts of the starboard and port halves of the main wing) is made of FRP strengthened by aluminum pipes. It has a step on the bottom and the rudder near the trailing edge. Outer wings and tail unit are constructed from aluminum pipes and covered by cloth. The outer Fig. 30. A model of ekranocat tested in Australia. wings have endplates at the tips. The main wing does not have a ﬂap. The horizontal tail represents aFig. 31. Artist’s view of a 100-knot ‘‘semi-WIG’’ WPT ferrydesigned to carry 600 passengers and 100 cars.3.5.4. New Japanese WISE craft developments A tendency of Japanese designs to have a simpleﬂying wing conﬁguration started by Kawasaki Fig. 32. m-Sky 2 wing-in-surface effect (WISE) vehicle (S. Kubo,KAGs was conﬁrmed in the m-Sky vehicle series Mitsubishi).
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 225stabilizer with elevator to adjust the angle of attack. length 29.5 m, width 19.6 m, propulsion 3046 kW Â 2The vehicle has two vertical ﬁns with air rudders. turboprop, maximum speed of 160 knots, with the Japanese Canard WISES project: Kawasaki Jetfoil. The former has a transportation The developers (from Tottori University, Japan) capacity 1.5 times that of the Jetfoil.claim that a wing-tail conﬁguration shows somedefect in takeoff, whereas the proposed canard 3.5.5. RotorWIG layout facilitates takeoff from rough seas . They Rotor WIGs are characterized by a large over-attempted to illustrate their idea by means of self- head rotor. The rotor allows for the third mode ofpropelled model tests with 1.8 and 3.6 length models locomotion, positioned between the hull and the(Kaien (storm petrel)-1 and 2). They state that wing. The rotor features tip weights that make upWISES should have seaworthiness over 3.0 m wave about half of the total weight of the rotor system.height for practical service in the seas around Japan. Before takeoff the rotor is over-rotated. ShortlyIn the authors’ opinion, the canard scheme allows to after initiating the takeoff run, the pitch of the rotortakeoff with high angle of incidence. In comparison, blades is increased and, within seconds, the craftthe wing-tail scheme does not allow large rotation leaves out of the water. Suddenly freed from anyangle without touching the water. They also think water drag, the air propellers accelerate the craftthat PAR ceases to be an effective liftoff aid in swiftly to cruising speed and it is the wing that takesrough seas because the impinged air leaks easily over the lift from the rotor. During cruise, the rotorfrom under-the-wing. The canard-type WISES used is off-loaded and its rpm allowed to drop to lowerby the authors has a forward mounted horizontal the drag quite drastically. For landing, the rotorstabilizer (canard) and two propellers on it. The disc is held back to catch enough wind to act as anelevator on the canard controls the pitching air break and increase its rpm. The energy in themoment of the ship and the deﬂection angle of the over-rotated rotor is then spent to lower the craftpropeller wake. Vertical ﬁns with air propellers are softly on the waves during ﬂare with little if anyin the wake ﬂow of the propellers. In the developers forward speed.opinion, the merits of the concept are: The HeliFerry : RotorWIGs can be conﬁgured in many different high angle of attack position results in a high lift ways to ﬁt different mission objectives. HeliFerry force, (HF) is a WIG version of HeliPlane, a twin pusher high-speed wake from the props prevents both propeller rotorcraft of the size of a C-130 Lockheed the canard and the main wing from stalling, even transport plane and speciﬁcally designed around the in a high lift condition, Carter rotor system, Fig. 33. The HF is a double the elevator and rudders are efﬁcient even for decked rotorWIG based on a very slender hull small forward speed because they are in the trimaran conﬁguration. The low wing is of classic propeller wake, Lippisch, reverse delta design. The other speciﬁca- propulsion systems always work in a spray-free tions are: length—118 ft, rotor radius—150 ft, region. beam—70 ft, displacement—110,000 lbs, cruise speed—120 knots at sea state 3. The rotor system It is emphasized that the concept is better suited itself weighs 3 600 lbs, including the hub, pitchfor large WISES. The main wing of Kaien-2 has a linkages and the tip weights, its rpm ranges from aproﬁle of NACA3409s (NACA3409 with modiﬁedcamber line in rear part), whereas Kaien-1 had aproﬁle of ClarkY. The lift-to-drag ratio in cruisewas 6, i.e. somewhat lower than expected. Takeoffspeed was 6 m/s and cruising speed was 9.5 m/s. Thepitch angle in cruising was 4–51 and at takeoff—2.5–3.51. In circular ﬂight the mean roll angle was 51.The maximum lift coefﬁcient at takeoff (pitch up 151)was 1.9, i.e. about 4 times larger than that incruising. They compared their preliminary design of aWISES for 140 passengers, displacement 56 tons, Fig. 33. HeliFerry—example of RotorWIG.
ARTICLE IN PRESS226 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283maximum in over-rotation of 125 to 85–100 no need for airports or runways,required for full lift, to settle to 25 in cruise. no need for sealed cabins as required on strato- spheric airplanes.3.5.6. Korea WIG project  Recently, it has been announced that the Korean 4.1. Civil applicationsgovernment plans to invest by 2010 in the develop-ment of a large 300-ton WIG effect vehicle capable According to a preliminary analysis, as reportedof carrying 100-ton payload at a height of 1–5 m by Belavin , Volkov et al.  and Hooker ,above sea level. This WIG craft would have a length there exist encouraging prospects for developingof 77 m, width of 65 m and would cruise at an commercial ekranoplans to carry passengers and/oraverage speed of 250 km/h. The plan is to use it as a cargo, to be used for tourism and leisure as well asnext generation cargo ship to reach the neighboring for special purposes, such as search-and-rescuecountries or islands in South Korea. It could reach operations.Qingdao, China from Inchon, South Korea in 3 h.In particular, it would be useful for fast delivery of 4.1.1. Search-and-rescue operationsfresh vegetables and fruits. Korea Ocean Research Memories are still fresh about the tragedies thatand Development Institute has already ﬁnished a happened with the nuclear submarine ‘‘Komsomo-successful test of a small four-seat WIG craft whose lets’’ on April 7, 1989 in the Norwegian Sea, and thedevelopment started in 1995. A sketch of the nuclear submarine ‘‘Kursk’’ on August 12, 2000 inKorean large WIG ship is presented in Fig. 34. the Barents sea. An analysis of existing means of rescue on water shows that surface ships are unable to come to the place of disaster quickly enough, while airplanes cannot perform effective rescue operations because the airplanes cannot land close to a sinking ship. Even most modern seaplanes have both lower payload and seaworthiness as compared to the ekranoplans. The GE search-and-rescue vehicle ‘‘Spasatel’’ is under construction at ‘‘Volga’’ plant in Nizhniy Novgorod. Fig. 34. Artist’s impression of Korean large WIG ship. ‘‘Spasatel’’, Fig. 35 which is based on the ‘‘Loon’’-type ekranoplan, combines features of all4. Areas of application of WIG effect craft known means of rescue on sea (search-and-rescue airplanes, helicopters, ships). Its cruising speed is Widely discussed, see Belavin , Volkov et al. expected to be in the range of 400–550 km/h in GE, and Hooker , are such beneﬁcial properties of and up to 750 km/h out of GE. Altitude when ﬂyingekranoplans as: far from the underlying surface would be up to 7500 m, and about 500 m in searching mode. The cost effectiveness when properly designed and vehicle can land and conduct rescue operations in sized, waves up to 3.5 m. It is capable of loitering in rough high ride quality (low level of accelerations) in seas with wave heights reaching 4 m. ‘‘Spasatel’’ has cruise mode, impressive seaworthiness in takeoff and landing and practically unlimited seaworthiness at cruise, safety of operation due to the effect of ‘‘binding’’ to the underlying surface and also because ‘‘...the airport is right beneath you...’’ amphibious capacity, i.e. ability to operate in GE over water, land, snow or ice surface, capacity of climbing an unprepared beach to embark/disembark passengers or carry out the maintenance of the vehicle, Fig. 35. Search-and-rescue ekranoplan ‘‘Spasatel’’.
ARTICLE IN PRESS K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 227a range of 3000 km, can operate autonomously for 5 The system implies that a search-and-rescue variantdays and is able to accommodate up to 500 people, of ‘‘Orlyonok’’ with improved seaworthiness andsee Denissov . Before a decision todevelop special medical equipment is mounted on the back of‘‘Spasatel’’ had been taken several experiments on the mammoth airplane AN-225 ‘‘Mria’’ to bethe available missile carrier ‘‘Loon’’ have been transported to the place of disaster at a speed ofperformed to appraise the ekranoplan’s capacity 700 km/h. Upon arrival at the place of emergency theto serve as a rescue vehicle. These experiments ekranoplan takes-off from AN-225, descends andshowed that ekranoplans have some useful features lands on the water surface to turn into a seagoingjustifying their use for rescue operations on the rescue vessel. Note that due to the considerablewater. In particular, when drifting on water the strength of its structure the ekranoplan can land invehicle is naturally brought to a position with its rough seas, which is dangerous for seaplanes.nose against the wind. As the vehicle’s main wing ispartially (with its aft part) immersed in the water, 4.1.2. Global Sea Rescue System there forms a region of relatively calm water behind There is a worldwide concern to develop effectiveit. The upper side of the main wing can be used as a rescue measures on the high seas. Experience showsplatform for embarkation of lifeboats and people that it is very difﬁcult if not impossible to providefrom the water surface, Fig. 36. timely aid at wreckages and ecological disasters at The CHDB in Nizhniy Novgorod and the Ukrai- sea. Use of seaplanes is often limited because ofnian aviation enterprise ‘‘Antonov’’ jointly studied unfavorable meteorological conditions, whereas usethe possibility of developing a unique large search- of helicopters is restricted to coastal areas. Untiland-rescue system which combines the long-range now, the main means of rescue (salvage) on waterand high-speed capability of a large airplane with the has been ships ﬁnding themselves accidentally nearlife-saving features of ekranoplans in the sea, Fig. 37. the disaster area and hardly suitable for this purpose. A global sea rescue system is proposed, compris- ing 50 heavy weight ekranoplans, basing in 12 selected focal base-ports throughout the world. Each ekranoplan of the system is designed to have high takeoff/touchdown seaworthiness, correspond- ing to sea state 5 and enabling its operation on the open sea during 95% of the time year around. The cruise speed of each ekranoplan of the system is 400–500 km/h and the radius of operation constitu- tes 3000–4000 km. The vehicle can loiter for a longFig. 36. Artist’s impression of rescue operations with ekrano- time upon the sea surface when seaborne at a speedplan. of 15 knots. The rescue vehicle is supposed to bring to the place of disaster a wide array of rescue means including rafts and self-propelled cutters and, possibly, helicopters and bathysphere. 4.1.3. Horizontal launch of the aerospace plane According to the project developed jointly by Musashi and Tokyo Institutes of Technology [39,40], an unmanned self-propelled ekranoplan is supposed to carry, accelerate to almost half sound speed and launch a 600-ton rocket plane to a low earth orbit (horizontal launch), see Fig. 38. Launching useful payloads into low earth orbit and expanding the functional capacity of the aerospace transport systems is one of the majorFig. 37. A search-and-rescue complex combining the ‘‘Mria’’ and tasks of the developers of new space projects for the‘‘Orlyonok’’ (Project). 21st century.
ARTICLE IN PRESS228 K.V. Rozhdestvensky / Progress in Aerospace Sciences 42 (2006) 211–283 deploying hydrophones or towed arrays. They can also be used in a wide variety of reconnaissance and transport roles. WIG effect vehicles could adapt themselves to an operational concept of anchorages all over the world to maintain a forward posture. 4.2.1. Anti-surface warfare Fig. 38. Ekranoplan-rocket plane horizontal launch. Sustained sea-level operations of ekranoplans would reduce the horizon-limited detection ranges of defending airborne early warning systems,4.1.4. Other civil applications signiﬁcantly reducing warning time. If the defender Other potential special areas are the replacement has no airborne early warning assets, mast heightof crews of ﬁshing vessels, geophysical surveys, ship radars would not see the ekranoplan until itexpress delivery of mail and parcels over the ocean; almost reached its target.coast guard and customs control operations. Ekra- Back in 1966 the company ‘‘Grumman’’ devel-noplans of moderate sizes can be used to service oped a project of a 300-ton WIG effect missilecoastal waters and to support transportation carrier conﬁgured as a ﬂying wing with in-ﬂightsystems of archipelagos, carrying passengers and variable geometry, the latter being achieved due to atropical fruits, fresh ﬁsh, etc. Similar considerations peculiar design of endplate ﬂoats . This project iscan be found in Kubo . shown schematically in Fig. 39. As per Hooker, the ultra-large vehicles of ‘‘Wing- Another example of a missile carrying strikeship’’ type offer many commercial possibilities, such as ekranoplan is ‘‘Loon’’ with 6 dorsally mounted ‘‘Mosquito’’-type missiles. transportation of non-standard commercial pay- From operational and tactical viewpoints, the loads of large sizes and weights, ekranoplan has incontestable advantages versus any search-and-rescue operations of large scale other missile-carrying platform, in particular transportation of perishable goods in quantity throughout the world, ekranoplan speeds exceed by an order of high-speed luxury transportation, magnitude those of conventional surface ships. rapid response to international market ﬂuctua- Unlike aircraft, the ekranoplan is not tied to tions. airports or aircraft carriers and can be disper- sively based in any coastal area, unlike aircraft, the ekranoplan is less visible, ﬂies4.2. Naval applications in immediate proximity to the water surface, and has large combat payloads (60 tons for the Analysis of known projects and future naval ‘‘Loon’’). Due to its additional capability toapplications have conﬁrmed that the above listed conduct ﬂight operations far from the underlyingproperties of ekranoplans together with their high surface, the ekranoplan can perform self-target-surprise factor due to speed, low radar visibility, sea ing for larger ranges.keeping capability, payload fraction comparable tosimilar size ships, dash speed feature and capacity toloiter aﬂoat in the open ocean make them perfectmulti-mission weapons platforms which can bedeployed forward and operate from tenders, seeBelavin , Sommer . Naval ekranoplans can be used as strike warfareweapons against land and seaborne targets, launchplatforms for tactical and strategic cruise missiles,aircraft carriers and amphibious assault transportvehicles. Easy alighting at moderate sea statesmakes it possible to utilize ekranoplans as anti- Fig. 39. Missile WIG vehicle developed by ‘‘Grumman’’ (Pro-submarine warfare planes capable of effectively ject).