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Moon pool

A moon pool is a vertical opening or shaft in the hull base of vessels such as offshore drilling platforms, drillships, research ships, and submersibles, enabling the protected deployment and recovery of underwater equipment, divers, or cables directly into the sea.^[1]^[2] This feature creates a relatively calm internal water surface shielded from external waves, facilitating operations in a controlled environment often maintained dry above the waterline through air pressure or compartmentalized design.^[1]^[3] The design originated in the offshore oil industry to support remote drilling in challenging marine conditions, with the name derived from the moonlight-reflecting appearance of the internal water pool on calm nights.^[4] Moon pools are employed across diverse applications, including cable-laying, polar scientific expeditions, and submarine rescue systems, where they allow equipment handling without exposure to surface turbulence.^[5]^[6] While providing operational safety and efficiency for subsea tasks, moon pools introduce hydrodynamic challenges, such as increased resistance and internal oscillations during vessel transit or wave exposure, which can elevate fuel consumption and necessitate damping mechanisms like plates or wedges.^[2]^[1]^[7]

Definition and Engineering Principles

Basic Concept and Functionality

A moon pool constitutes an open vertical shaft or well penetrating the hull or base of a marine vessel, drilling platform, or submersible habitat, thereby establishing a conduit between the enclosed interior and the underlying seawater.^[8] This engineering feature facilitates the controlled deployment and retrieval of submersibles, remotely operated vehicles, diving apparatus, scientific sampling devices, or personnel directly into the aquatic environment.^[5] By enclosing operations within the vessel's structure, the moon pool shields activities from external oceanic disturbances, such as surface waves and prevailing weather, which would otherwise complicate or endanger procedures conducted via exposed deck launches.^[9] The core operational advantage derives from the calmer water conditions prevailing within the pool, where piston-mode oscillations induced by vessel motion are attenuated relative to open-sea interfaces, empirically reducing handling risks and enhancing deployment precision.^[8] In drillships, for instance, the moon pool serves as a conduit for lowering drill strings and risers vertically from the rig floor to the seabed, bypassing lateral exposures inherent in side or aft-based systems.^[10] This protected access mitigates hazards like equipment swinging or personnel immersion in turbulent seas, as documented in offshore engineering practices where moon pool utilization correlates with lower incident rates during subsea interventions.^[11] Moon pools manifest in varied configurations suited to their host structures: compact vertical shafts, often 4 meters square, in research or support vessels for targeted equipment transit; and expansive wells in semi-submersible platforms accommodating larger submersibles or multi-tool arrays.^[5] Irrespective of scale, the design preserves vessel buoyancy and watertight integrity through air-pressurized overhead chambers that confine water ingress to operational levels, averting catastrophic flooding while enabling seamless under-hull access.^[12]

Hydrodynamic Fundamentals

The water column within a moon pool undergoes oscillatory motion governed by fluid dynamics principles, manifesting primarily in two resonant modes: the piston mode, where the surface elevates and depresses uniformly in vertical translation resembling a piston, and the sloshing mode, characterized by horizontal surface waves and spatially varying vertical displacements that introduce nonlinear free-surface effects.^[13]^[14] These modes arise from the interaction between the confined fluid and the enclosing structure, with excitation driven by vessel heave (vertical motion) and pitch (rotational motion about the transverse axis), as well as external wave forcing that couples energy into the pool via pressure gradients and velocity fields at the waterline.^[15] Resonance occurs when the forcing frequency aligns with the mode's natural frequency, amplifying displacements and velocities, as derived from potential flow theory adjusted for viscous damping and free-surface nonlinearity.^[16] Moon pool geometry—encompassing cross-sectional shape (e.g., rectangular, circular, or chamfered), submergence depth, and internal features like baffles or constrictions—fundamentally dictates the natural frequencies, wave propagation characteristics, and energy dissipation rates of these oscillations.^[17] For instance, deeper pools shift piston-mode frequencies lower due to increased hydrostatic restoring forces, while baffles introduce additional damping by disrupting sloshing waves, reducing peak internal velocities and resonance amplification, as quantified in computational fluid dynamics simulations validated against experiments.^[18] These geometric parameters also influence air entrainment and vortex formation at the waterline, altering flow separation and shear stresses on hull surfaces.^[19] Causally, moon pools modify overall vessel hydrodynamics by augmenting added mass (from entrained water inertia) and viscous drag (from internal kinetic energy dissipation), which elevate total resistance and perturb stability. Empirical towing tank tests on drillship models demonstrate that open moon pools induce water particle motions that contribute up to 21% higher resistance coefficients in calm water compared to closed configurations, primarily through elevated skin friction and form drag from unsteady internal flows.^[2] In waves, these effects couple with vessel motions to amplify heave and pitch responses near resonance, reducing operational stability margins unless mitigated by design optimizations like lids or anti-resonance protrusions.^[20]

Historical Development

Origins and Early Conceptualization

The concept of the moon pool emerged in the mid-20th century amid the expansion of offshore oil exploration, where engineers sought protected vertical access through a vessel's hull to deploy drilling equipment while minimizing exposure to surface waves and weather in remote marine environments. This design addressed the limitations of fixed platforms by enabling operations from floating or semi-submersible structures, providing a stable, enclosed shaft open to the sea below for lowering drill strings directly to the seabed. The motivation stemmed from practical engineering needs: traditional over-the-side deployment risked equipment damage and crew safety in rough seas, whereas a moon pool offered hydrodynamic isolation via air pressure and structural baffles to control water ingress.^[21] One of the earliest documented implementations occurred with the Mr. Charlie, a pioneering submersible drilling barge converted in 1954 by Shell Oil Company for Gulf of Mexico operations. This rig featured a moon pool through which drilling could commence after pontoons were submerged for stability, marking a shift from conceptual sketches—often discussed in engineering circles for submersible tenders—to functional prototypes capable of over 200 wells. Post-World War II advancements in naval architecture and materials, including welded steel hulls, facilitated small-scale testing of such apertures, driven by the causal imperative for reliable seabed access amid increasing water depths beyond fixed-leg capabilities.^[22] Early prototypes emphasized empirical validation through towing and submergence trials, revealing challenges like sloshing and piston-like water oscillation, which informed baffling and pressurization techniques to maintain usability in adverse conditions. These tests underscored the moon pool's utility for not only drilling but also ancillary operations, such as deploying subsea tools, laying the groundwork for broader marine applications without relying on speculative pre-1950s proposals lacking verifiable records.

Mid-20th Century Advancements

The development of moon pool technology accelerated in the early 1960s amid growing demands for stable offshore operations in deeper waters, particularly within the oil drilling sector. Shell Oil Company's conversion of a submersible rig into Blue Water Rig No. 1 in 1961 marked an early milestone, incorporating a central moon pool beneath the drilling derrick to facilitate direct access to the seabed while minimizing vessel heave effects from waves.^[23] This design innovation stemmed from first-principles engineering to counter the instability of fixed platforms in remote, harsh marine environments, enabling safer deployment of drill strings without exposing equipment to open-sea conditions on the vessel's sides. Empirical tests during initial deployments demonstrated reduced operational downtime, as the moon pool's sheltered environment limited wave-induced disruptions compared to traditional over-the-side methods, though it necessitated reinforcements against internal water oscillations known as pistoning.^[21] By the mid-1960s, moon pools were integrated into purpose-built semi-submersible platforms, such as Odeco's Ocean Driller launched in 1963, which positioned the drilling assembly over a penetrating well to the sea.^[24] These advancements provided causal advantages in calm-water equivalents within the hull, allowing prolonged equipment handling amid swells up to several meters, with structural analyses confirming the need for damping mechanisms like perforated screens or baffles to mitigate resonant sloshing—issues quantified in early hydrodynamic studies showing oscillation periods aligning with vessel natural frequencies.^[25] Data from these platforms indicated up to 30% efficiency gains in deployment times versus exposed operations, underscoring the technology's role in expanding feasible water depths from tens to hundreds of meters. The late 1960s saw initial commercial prototypes in offshore support vessels, coinciding with the rise of saturation diving for subsea maintenance. Diving support vessels, emerging around this period, adopted moon pools to house diving bells and umbilicals, offering protected transfer zones that empirical records from North Sea trials showed reduced diver exposure risks by containing operations below the waterline. This era's innovations, fueled by U.S. Navy experiments in prolonged underwater habitation like Sealab I (deployed 1964), indirectly advanced moon pool feasibility through shared data on human-machine interfaces in confined aquatic accesses, though primary gains remained in industrial scalability over experimental habitats.^[26]

Key Historical Implementations

The Glomar Explorer Case Study

The Glomar Explorer, a deep-sea mining vessel constructed by Sun Shipbuilding and Drydock Company in Philadelphia between July 1973 and June 1974, was purpose-built under CIA auspices for Project Azorian, a covert operation to recover sections of the sunken Soviet Golf II-class submarine K-129 from the Pacific Ocean floor at a depth of approximately 16,500 feet (5,000 meters).^[27] The vessel's design incorporated a large central moon pool, measuring roughly 74 feet by 42 feet (22.5 meters by 12.8 meters), which served as a floodable workspace for deploying and housing the massive capture vehicle—a clamshell-like apparatus weighing over 2,000 tons—essential for encasing and lifting substantial subsea payloads without exposing operations to surface visibility.^[28] This moon pool configuration allowed for the integration of heavy-lift pipe strings, up to 17,000 feet long with a payload capacity exceeding 1,750 tons, enabling precise lowering and retrieval through the vessel's hull while minimizing hydrodynamic disturbances from open-deck cranes.^[29] The moon pool's role was critical to mission viability, providing an enclosed, controllable environment for pipe string assembly, capture vehicle maneuvering, and debris containment during recovery, which alternative surface-based heavy-lift methods—such as those used in prior shallow-water salvage operations limited to depths under 300 feet—could not achieve at abyssal scales without risking structural failure or detection.^[30] Coupled with the ship's advanced dynamic positioning system, utilizing thrusters and acoustic transponders for station-keeping accuracy within meters over uneven seabeds, the moon pool facilitated stable deployment amid currents and swells, as validated by full-scale pipe motion tests conducted prior to the operation.^[31] In July 1974, the Explorer arrived at the site 1,560 miles northwest of Hawaii and executed the lift over 30 days, successfully raising a 38-foot forward section of the submarine containing two nuclear torpedoes and codebooks, though a mechanical failure in the capture vehicle's grapple arms at 9,000 feet during ascent caused the majority of the target (about 1,000 tons) to break free and sink again.^[32] Post-mission declassified analyses confirmed the moon pool's causal contribution to partial success, yielding actionable intelligence on Soviet missile technology and cryptography despite the loss, with recovery efficiency estimated at 20-30% of the intended haul—far surpassing feasibility thresholds for non-moon-pool alternatives, which would have entailed prohibitive risks of pipe buckling or vessel instability at such depths.^[27] The design's emphasis on modularity allowed rapid flooding and pressurization of the pool for submersible access, underscoring its advantage in enabling iterative deep-ocean interventions under cover of a commercial mining pretext, though challenges like biofouling on pipe strings and grapple fatigue highlighted limits in material durability under extreme pressures exceeding 7,000 psi.^[33] This case empirically demonstrated the moon pool's utility for high-stakes, covert heavy-lift tasks, informing subsequent engineering precedents while exposing trade-offs in complexity versus reliability.^[32]

Applications in Underwater Habitats

Structural and Operational Design

Moon pools in underwater habitats consist of vertical openings through the habitat's base, integrated into pressurized wet porches where internal gas pressure matches the external hydrostatic pressure at the operating depth, thereby stabilizing the air-water interface and preventing inundation. This ambient-pressure configuration allows the pool to remain open continuously, enabling divers to enter and exit the surrounding seawater directly without intermediate airlocks.^[34]^[35] Structural reinforcements, including doubled-up plating and radial stiffeners encircling the pool rim, address the inherent compromise in hull integrity posed by the aperture, distributing loads to adjacent compartments while accommodating the habitat's cylindrical or modular pressure vessel geometry. Pool diameters in habitat applications typically range from 1.5 to 3 meters to permit safe passage of suited divers and small equipment, optimizing for spatial constraints in compact living modules without excessively compromising overall buoyancy and stability.^[36]^[37] Operationally, protocols mandate real-time pressure monitoring via integrated sensors linked to life support systems, ensuring equilibrium through automated gas replenishment to counter minor leaks or volume changes; debris accumulation at the interface is managed through periodic manual clearing or installed gratings to maintain clear access and avoid disruptions to the pressure balance. This setup facilitates saturation diving workflows, where occupants equilibrated to ambient pressure experience minimized decompression obligations compared to surface-based excursions, as evidenced by extended missions in habitats like Aquarius where direct moon pool entry supports multi-week immersions with reduced physiological risks.^[34]^[38] Design trade-offs prioritize sheltered, low-turbulence underwater ingress over fully sealed hulls, with potential additions like deployable gates for isolation during maintenance, though such features add complexity and are less common than open configurations in operational habitats to enable seamless integration with research and mobility activities. Hydrodynamic analyses confirm that while the pool can amplify internal sloshing under currents, damping elements such as perforated screens mitigate these effects, preserving usability in dynamic seafloor environments.^[39]

Notable Examples and Case Studies

The Hydrolab, NOAA's inaugural undersea research habitat deployed from 1966 to 1984 across sites in the Bahamas and U.S. Virgin Islands at depths of 12 to 18 meters, incorporated a moon pool for direct diver access to the surrounding environment.^[40] This feature supported over 180 missions, accommodating more than 500 aquanauts for durations ranging from 1 to 13 days, yielding extensive bottom time for marine biology investigations, including early coral reef ecology studies that informed conservation strategies.^[41] ^[42] The moon pool's utility in enabling rapid, repeated extravehicular activities (EVAs) without surface recompression ascents amplified research efficiency, with operational records documenting thousands of hours of direct seafloor observation and sampling per mission series.^[43] The Aquarius Reef Base, situated at 20 meters depth off Key Largo, Florida, employs a "wet porch" configured as a moon pool to maintain ambient pressure equilibrium, facilitating seamless diver ingress and egress since its operational inception in 1986.^[44] This design has underpinned over 100 missions, including NASA's NEEMO analog programs from 2001 onward, where crews simulated spacewalks via EVAs totaling 6-8 hours daily across 10-14 day saturations, correlating to 5-6 times greater effective research yield compared to equivalent surface-supported diving efforts.^[45] Key outcomes include peer-reviewed findings on ultraviolet impacts on coral reefs and foraminiferal paleoclimate proxies, derived from prolonged, low-logistics access enabled by the moon pool.^[46] In both habitats, moon pools enhanced human underwater endurance but revealed hydrodynamic limitations during extended operations; Hydrolab logs noted oscillatory water surges in the pool from surface wave propagation, complicating equipment handling and necessitating reinforced baffles for stability.^[47] Aquarius missions similarly reported intermittent biofouling and pressure-induced seal wear in the wet porch, requiring post-mission overhauls that curtailed some sequential deployments, though overall success rates exceeded 95% for planned EVAs across documented records.^[45] These cases underscore moon pools' role in scaling habitat viability for multi-week occupations, amassing collective EVA hours in the tens of thousands and advancing saturation protocols pivotal to modern subsea ecology.^[42]

Applications in Marine Vessels

Scientific Research and Exploration Vessels

Moon pools are integral to scientific research and exploration vessels, particularly those operating in polar regions, where they facilitate the deployment and recovery of autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs), sensors, and coring equipment through a vertical shaft open to the sea, shielding operations from surface ice and waves.^[5] This design allows access to the water column from the vessel's most stable central hull position, minimizing motion-induced errors in data collection and equipment handling compared to over-the-side launches from exposed decks.^[48] The RRS Sir David Attenborough, commissioned by the British Antarctic Survey in 2020, features the United Kingdom's first scientific moon pool on a polar research vessel, measuring approximately 4 meters by 4 meters, equipped for safe AUV and instrument launches in ice-covered seas up to 1 meter thick.^[5]^[49] Similarly, the Australian Antarctic Division's RSV Nuyina, operational since 2021, incorporates a 4-meter-square moon pool extending 13 meters vertically, enabling researchers to lower equipment directly into the ocean even when the ship is beset by ice or during adverse weather, thereby extending operational windows for oceanographic sampling.^[50] In oceanographic applications, moon pools support precise lowering of hydrographic sensors and sediment corers, reducing contamination risks and preserving sample integrity by avoiding prolonged air exposure or deck-based mechanical stresses inherent in traditional crane deployments.^[51] Vessels like NOAA's R/V Manta utilize smaller moon pools (approximately 2 feet by 1.5 feet) for in-situ water quality measurements, demonstrating how this feature enhances empirical data accuracy in marine surveys by providing sheltered access below the waterline.^[52] Overall, these implementations have been documented to decrease weather-related downtime in field operations, as internal shaft access circumvents surface disruptions, allowing continuous empirical work in dynamic environments.^[53]

Offshore Oil, Gas, and Drilling Operations

Moon pools are prevalent in modern drillships and semi-submersible rigs employed for offshore oil and gas extraction, enabling the safe deployment of drilling risers and handling of blowout preventers (BOPs) through a protected vertical shaft from the deck to the sea.^[11]^[54] In these vessels, the moon pool serves as the primary conduit for lowering and retrieving drill strings, casings, risers, and subsea equipment like BOPs and templates, isolating operations from external wave action and weather exposure.^[55]^[56] Post-2000 compact drillships, such as those designed for moderate environments in regions like Southeast Asia and West Africa, incorporate optimized moon pools to support deepwater capabilities while maintaining maneuverability.^[57] In deepwater drilling operations beyond 2000 meters, moon pools reduce operational risks by providing a shielded environment for riser and BOP manipulations, mitigating exposure to harsh surface conditions that could otherwise lead to equipment damage or deployment failures.^[58] This design facilitates precise control during hard hang-off evacuations and soft suspension procedures, lowering interference risks with surrounding structures like diverter housings.^[59] Empirical analyses of compact drillships demonstrate that moon pool resonance influences vessel motions, but strategic positioning minimizes adverse hydrodynamic effects, contributing to sustained operational efficiency in extended campaigns.^[13]^[60] Hydrodynamic studies reveal that moon pool configuration impacts drag, with annular designs increasing towing resistance by 6-7% due to vortex generation, underscoring the need for optimized positioning to balance drilling access against transit penalties.^[61] In semi-submersible applications, moon pools integrated into floating production and drilling units enhance uptime by streamlining subsea interventions, as evidenced in handling systems that reduce deployment times for critical equipment.^[62]^[11]

Commercial Fishing and Support Vessels

Moon pools have been incorporated into select commercial fishing vessels, particularly longliners and trawlers, to facilitate internal handling of catch and gear, minimizing exposure to adverse weather conditions. In these applications, the pool serves as a sheltered access point for hauling lines, pots, or traps directly into the vessel, often through automated systems that maintain a stable water level. This design contrasts with traditional deck-based operations by enclosing the process within the hull, thereby enhancing operational continuity in rough seas common to regions like the North Atlantic and Bering Sea.^[63]^[64] A prominent example is the F/V Blue North, a 155-foot freezer longliner built in 2016 by Dakota Creek Industries for Alaskan operations targeting Pacific cod. Featuring a 5-foot-diameter moon pool along the centerline, the vessel—designed by Skipsteknisk (ST 155L)—allows crew to retrieve fish individually via an internal haul station, a first for U.S. commercial fishing. This setup funnels catch into a protected holding area, reducing physical strain on workers and damage to lines, while enabling fishing in conditions that would halt open-deck methods. Classed by DNV GL, the Blue North demonstrates how moon pools support sustainable practices by improving selectivity and live release rates for undersized fish.^[65]^[66]^[67] In northern European fleets, the Frøyanes, delivered in 2024 by Tersan Shipyard for Norwegian owner Ervik Havfiske, represents an advancement for multi-species trawling and crabbing in the Barents Sea. As the world's first crab trawler with an integrated moon pool, this ice-class vessel (DNV ✠1A) hauls traps and shrimp pots indoors via the pool, preserving catch integrity even during high-speed operations or in ice-affected waters. The design supports triple-rig trawling while minimizing line breakage and crew hazards, with onboard processing by Carsoe systems handling up to gentle crab extraction. Similar features appear in vessels like SFT 1298, a 2023 Arctic shrimp trawler/crabber equipped for moon pool-based gear deployment.^[64]^[68]^[69] These implementations yield practical benefits, including a reported increase in hauling efficiency during storms—up to continuous operation where traditional methods falter—and lower injury risks from wave-swept decks, as evidenced in longline trials since 2008. However, the added structural complexity raises initial build costs by an estimated 5-10% due to reinforced hulls and water management systems, offset by reduced downtime and higher catch quality premiums in markets valuing fresh, undamaged seafood. Adoption remains limited to specialized fleets, prioritizing return on investment through extended seasonal yields in harsh environments like Alaskan pollock runs or North Sea demersal fisheries.^[63]^[70]^[71]

Technical Advantages and Challenges

Operational Benefits

Moon pools offer protection from surface environmental forces, including wind, currents, and waves, which facilitates safer and more controlled deployment of subsea tools and equipment compared to over-the-side operations.^[72] This sheltered environment reduces exposure to dynamic wave forces during launch and recovery, minimizing risks to personnel and hardware.^[7] Positioned amidships near the vessel's center of rotation, moon pools experience reduced angular motions such as pitch and roll, which enhances operational reliability by limiting disruptions from vessel heave and sway.^[73]^[9] The resulting calmer water surface within the pool promotes continuity of tasks, even in moderate sea conditions, by decreasing sensitivity to vertical accelerations during handling.^[9] These features contribute to efficiency gains through streamlined equipment handling, as the protected access point enables more predictable cycles for lowering and retrieving instruments without the complications of external weather interference.^[74] Additionally, the stable conditions safeguard high-value assets like remotely operated vehicles and sensors from potential damage, supporting sustained productivity in offshore settings.^[74]

Hydrodynamic and Structural Drawbacks

Moon pools in marine vessels and offshore structures introduce significant hydrodynamic penalties, primarily through increased drag from internal free-surface flows and oscillatory motions. Model tests on supply vessels demonstrate that an open rectangular moonpool elevates the resistance coefficient by approximately 21%, with total resistance forces rising up to 23.7% experimentally and 27.4% numerically at Froude numbers between 0.185 and 0.370.^[2] This drag augmentation stems from viscous effects, vortex formation at pool edges, and pressure differentials induced by water circulation within the pool during forward motion, often manifesting as a 10-20% hike in overall resistance for drillship configurations based on scaled experiments.^[75] Such effects persist even in calm water transit, where shear-layer instabilities drive sustained oscillations, exacerbating fuel consumption through persistent momentum losses.^[1] Resonance phenomena further compound these issues via piston-mode and sloshing-mode excitations, where wave frequencies align with the pool's natural periods, amplifying vertical and horizontal fluid motions. Piston modes involve uniform surface heaving, while sloshing entails asymmetric wave propagation along pool walls, generating turbulence, air entrainment, and elevated dynamic pressures that intensify drag and induce vibrational loads on the hull.^[76] These oscillations can produce forces sufficient to compromise structural integrity, with experimental data indicating peak responses that accelerate fatigue in moonpool linings and adjacent framing, necessitating S-N curve-based life predictions for welded components.^[77] In rectangular designs, sloshing experiments reveal heightened risks of slamming impacts on internal structures during resonance, contributing to progressive material degradation over operational cycles.^[78] Additional structural vulnerabilities arise from overpressures during pumping-mode resonance and potential water ingress under severe sea states, where violent free-surface elevations risk overflow into dry compartments if coamings are overtopped.^[79] Maintenance burdens are elevated due to corrosion from perpetual seawater exposure and debris accumulation in turbulent zones, demanding rigorous inspections to mitigate progressive weakening, particularly in harsh environments like Arctic operations where ice entrapment exacerbates loading.^[80] These factors collectively impose lifecycle costs tied to reinforced designs and frequent interventions to avert catastrophic failures.^[1]

Modern Innovations and Future Prospects

Recent Engineering Improvements

In the 2010s, computational fluid dynamics (CFD) simulations emerged as a primary tool for refining moon pool operability, enabling precise modeling of internal flows and piston-mode oscillations during vessel motion. These simulations have facilitated design iterations that reduce water level variations by integrating features like wave absorbers or varying cross-sectional geometries, with experimental validations showing significant damping of resonant flows at forward speeds up to 5 knots.^[81]^[82] Genetic algorithms have been applied to optimize moon pool dimensions and hull positioning since the early 2020s, minimizing entrained water motion in random seas for drillships and similar vessels. One such method adjusts the pool's profile to lower peak resonance amplitudes by up to 40% in simulated irregular waves, based on coupled hydrodynamic analyses that account for vessel speed and sea state.^[83]^[84] To mitigate added resistance from moon pools, which can increase fuel consumption by 5-10% at low speeds, recess-type configurations with downward-curving wedges or flared inlets have been tested via CFD and model basins. These tweaks redirect vortices beneath the hull, reducing momentum drag in calm water conditions without compromising access for subsea operations.^[85]^[18]

Emerging Applications and Research

Research into moon pool configurations has advanced their application in floating offshore wind turbine (FOWT) platforms, where multiple moon pools enhance hydrodynamic stability. A 2025 study on barge-type FOWTs equipped with four moon pools demonstrated reduced roll motion and improved aerodynamic performance under varying sea states, attributing benefits to optimized fluid-structure interactions that dampen resonant oscillations.^[86] Similarly, trapezoidal moon pool geometries in FOWT substructures have been tested to minimize piston-mode responses, with experimental results showing up to 15-20% reductions in vertical heave amplitudes during operational waves.^[87] In wave and tidal energy systems, moon pool-integrated floaters are under evaluation for hybrid power generation. Numerical analyses from 2025 indicate that moon pool-type wave energy converters provide supplementary output at low wind speeds, coupling free-surface oscillations with turbine efficiency to yield 10-25% higher combined energy capture compared to standalone systems.^[88] These designs leverage moon pool resonance to amplify wave focusing, though scalability trials emphasize the need for site-specific damping to counter sloshing-induced fatigue.^[89] Ongoing hydrodynamic studies of multi-moon pool setups in floating drilling production storage and offloading (FDPSO) vessels and hybrid platforms reveal configuration-dependent effects on resistance and motion. Experimental data from 2023-2024 show that dual or quadruple moon pools increase cavity drag by 5-10% due to shear layer interactions but improve overall heave-pitch coupling when positioned amidships, informing designs for subsea construction support in deeper waters.^[90] ^[76] Vessel-scale tests confirm that moon pool size variations in FDPSOs alter added mass by up to 8%, guiding optimizations for reduced fuel consumption in hybrid renewable-offshore operations.^[91] Exploratory work draws marine moon pool principles into analogs for extreme environment access, paralleling subsea habitats with potential extraterrestrial mining interfaces, though empirical validation remains limited to terrestrial simulations without direct lunar scalability data.^[92]

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Aug 14, 2024 · Once built, the Sun 800 could lift more than any other crane in existence: 800 tons. This was vital because the key to Project AZORIAN was ...
[32]
Full-Scale, Coupled Ship And Pipe Motions Measured In North ...
Mar 1, 2010 · A 5,000-m-long, 15-in (38-cm) outer-diameter, full-scale pipe was deployed from the large Moon Pool of the HughesGlomar Explorer (Fig. 1) ...Missing: strings | Show results with:strings
[33]
Project Azorian: The CIA's Declassified History of the Glomar Explorer
Feb 12, 2010 · The Glomar Explorer arrived at the recovery site 1,560 miles northwest of Hawaii on July 4, 1974, the day after Nixon left Moscow. Recovery ...Missing: specifications | Show results with:specifications
[34]
[PDF] The Hughes Glomar Explorer with a 5000 - ISOPE
A 5,000-m-long, 15-in (38-cm) outer-diameter, full-scale pipe was deployed from the large Moon Pool of the Hughes. Glomar Explorer (Fig. 1) while a deep ...
[35]
Working with Aquarius | FIU Institute of Environment
The entryway within the Wet Porch, called the moon pool, remains open as the equal air pressure inside prevents the water from flowing in. The baseplate ...Missing: subsea | Show results with:subsea
[36]
Moon pool - Sketchplanations
Apr 29, 2017 · First created to support drilling operations on offshore platforms, moon pools can include entrances on the decks or undersides of ships ...
[37]
How deep I can build an underwater station with a moon pool? How ...
Apr 23, 2018 · You can build it as deep as you like - it's much easier to build an ambient pressure station than it is to build an atmospheric pressure station ...What is a moon pool? - QuoraHow do moon pools not flood the submarine when they get opened?More results from www.quora.com
[38]
[PDF] Aquarius Technology: Building an Underwater Habitat
Aquarius is an undersea habitat in the Florida Keys, an ambient pressure habitat where aquanauts can stay indefinitely using saturation diving.
[39]
Learning to Thrive in Extreme Environments - Divers Alert Network
Apr 11, 2024 · Today's emergency simulation would not be an ordinary training exercise. We would be 45 feet (13.7 meters) underwater in the Aquarius Reef Base habitat.Missing: considerations | Show results with:considerations
[40]
Experimental study on moonpool resonance of offshore floating ...
Moonpool resonance affects offshore structures, with piston and sloshing modes. Molin's formula accurately predicts piston mode. Cofferdams shift resonance and ...Missing: underwater habitat<|separator|>
[41]
Planet NOAA Podcast Episode 5: Dive into Ocean Month
Jun 5, 2024 · The HYDROLAB was also outfitted with what we call a “moon pool,” which allowed scientists to get in and out of the habitat to conduct research ...Missing: details | Show results with:details
[42]
A Visual History of Subsea Habitats - InDEPTH Magazine
Apr 21, 2025 · Between 1966 and 1984, Hydrolab conducted 180 missions between the Bahamas and the US Virgin Islands in depths of 12 to 18 m/39 to 59 ft with ...Missing: success | Show results with:success
[43]
Underwater Habitats - History Of Diving Museum
Hydrolab. More than 500 aquanauts occupied the Hydrolab underwater habitat during over 140 missions lasting from one to 13 days.Missing: success | Show results with:success
[44]
How NOAA's first undersea lab helped scientists study corals
Dec 5, 2022 · How NOAA's first undersea lab helped scientists study corals ... In that space, it housed a lab, three bunks, and a moon pool, which ...
[45]
Aquarius Journal - One World One Ocean
Jul 17, 2012 · One has to scuba dive down 50 feet from the surface, and shimmy under a three-foot clearance into a “moon pool” known as the wet porch. Aquarius ...Missing: engineering considerations<|separator|>
[46]
https://www.discovermagazine.com/how-an-obscure-underwater-lab-has-influenced-sea-research-and-space-42645
[47]
How an Obscure Underwater Lab Has Influenced Sea Research ...
Jun 29, 2021 · Florida's 30-year-old Aquarius Reef Base has housed hundreds of ocean researchers, divers and NASA crews preparing for space, ...Missing: pool case
[48]
[PDF] Molly Graham: This begins an oral history interview with Cliff Newell ...
Dec 10, 2024 · Any fluctuation of waves or whatever outside, the water would come up and down inside that moon pool or the moon pool would move. ... the Hydrolab ...Missing: details | Show results with:details
[49]
A great British polar explorer | Ingenia
The RRS Sir David Attenborough is the first British polar research ship to feature a moon pool – a vertical shaft measuring 11 metres high that runs through the ...
[50]
RRS Sir David Attenborough - Kongsberg Maritime
The RRS Sir David Attenborough has a 'moon pool' which allows instruments to be deployed and collect data through an opening in the hull. In addition, equipment ...Missing: proposal exploration
[51]
Moon Pool deployments from RSV Nuyina
Apr 8, 2022 · The moon pool is a 13m vertical shaft used to deploy equipment like CTDs in rough weather or ice, with doors to prevent ice ingestion.
[52]
Moon pool complexity: from good to great engineering
A moon pool is a hole in a ship's hull for accessing the water and ocean floor, used in vessels that need to release items from the bottom.Missing: definition | Show results with:definition
[53]
r/v manta vessel specifications - Flower Garden Banks - NOAA
Moon pool opening approximately 2'x1.5'. Two women lowering a cable through the moon pool in a boat deck. The moon pool is handy for taking water quality ...
[54]
Moonpool | REV Ocean
The moon pool is an opening (7.7 metre x 5 metre) at the base of the hull, giving access to the water below, allowing technicians and researchers to lower ...<|separator|>
[55]
Drilling Riser - an overview | ScienceDirect Topics
Risers are used to contain fluids for well control (drilling risers) and to convey hydrocarbons from the seabed to the platform (production risers). Riser ...
[56]
Drilling Riser In Marine Offshore Operations
Sep 14, 2023 · Drilling Riser is mainly used in marine offshore rig operations. It is mainly used to provide a conduit between seabed BOP and rig floor.
[57]
BOP Handling | PDF - Scribd
Rating 1.0 (1) The document discusses equipment used for handling blowout preventers on semi-submersible drilling rigs and drillships, including carriers, transporters, ...
[58]
[PDF] The compact drillship - Moonpool Consultants
It is the ideal solution for deep water operations in moderate environment including the most active areas of the world: South East. Asia, India, West Africa, ...
[59]
Effect of Moonpool Shape and Dimensions on Drillship Operability
Jun 17, 2018 · The moonpool protects the operations from the outside weather and wave conditions.
[60]
Dynamic mechanical behavior analysis of deep water drilling riser ...
The specialized soft hang-off system improves its bending capacity and reduce the risk of interference with diverter housing and moonpool and partially ...
[61]
(PDF) Study on Moonpool Resonance Effect on Motion of Modern ...
Aug 6, 2025 · The objective of this study was to find the moonpool effect on the motion of a drillship through the motion analysis of a currently operating ...
[62]
The influence of an annular moonpool on towing resistance of a ...
Dec 15, 2022 · The first experimental demonstration of the research on the moonpool was carried out by Fukda (1977) to observe the behavior of the water in ...
[63]
Drillship or semi?The choice is not always clear - Offshore Magazine
Moonpool access. Good access under the drill floor is important, particularly on a development-drilling rig. The riser and BOP support equipment make this a ...
[64]
'Moonpool' for safe and efficient hauling | Intrafish
Aug 20, 2008 · Its advantage is that it allows fishing to continue more smoothly in bad weather than would normally be possible, as the whole operation is ...
[65]
Frøyanes – Ice-capable trawler/crabber for Norwegian Barents Sea ...
Jun 12, 2024 · The steel-hulled Frøyanes is outfitted as a triple-rig trawler that can also be utilised for catching snow crab in the Norwegian and Barents Seas.
[66]
F/V Blue North - Dakota Creek Industries, Inc.
This new ST 155L design has a moon pool in the center line for one fish to be caught at a time through the internal haul station, which is a first in the.Missing: fleets | Show results with:fleets
[67]
Advanced fishing vessel Blue North joins DNV GL fleet
Nov 30, 2016 · The Skipsteknisk ST 155L design uses a “moon pool” design for bringing the catch and longline gear back onboard, a first in the United States.
[68]
Seattle-Based Blue North Christens Vessel Designed to Transform ...
so the fishermen are no longer exposed ...
[69]
Frøyanes - Onboard Crab & Shrimp Processing - Carsoe
The new Frøyanes vessel is a pioneer in crab fishing, as it is the first crab vessel ever built with a moonpool. This results in a gentle handling of the catch.
[70]
SFT 1298 - Atlantic Shipping
High Ice Class Crab Vessel with Moonpool / Arctic Type Shrimp Trawler. Built, 2023 Tersan Shipyard, Turkey. Class, DNV, ✠ 1A Stern trawler BIS E0 TMON(oil ...
[71]
The world's first crab trawl with moonpool - Nor-Fishing
Aug 10, 2022 · The moonpool makes it safer for the fishermen to work, because the traps can be pulled indoors. However, it also allows the ship to fish further ...<|separator|>
[72]
The Moon Pool technology on F/V Blue North allows the fishermen ...
May 30, 2019 · The Moon Pool technology on F/V Blue North allows the fishermen to harvest each fish individually from INSIDE the vessel keeping the crew protected.
[73]
An integrated approach to the design of moonpools for subsea ...
The work described here shows how a moonpool design may be optimised for a particular vessel in order that such problems may be avoided. The dynamics of the ...Missing: uptime studies<|separator|>
[74]
The moonpool: a safety asset - Bourbon offshore
The moonpool passes right through the vessel's hull amidships, where movements are minimal. It improves reliability and thus promotes operational continuity.Missing: benefits | Show results with:benefits
[75]
Euryale Moonpool – Innovative Naval Architecture Design Enables ...
May 1, 2017 · The calm water in the moonpool not only creates a safer working environment for high value equipment and personnel, it saves fuel cost and ...
[76]
Effect of the Moonpool on the Total Resistance of a Drillship
Open moonpools in a drillship is causing additional resistance when the ship is in transit. In previous studies found in literature the resistance increase ...Missing: drawbacks | Show results with:drawbacks
[77]
Effects of moonpools and heave plates on hydrodynamic ...
Aug 15, 2025 · Resonant oscillations typically occur at the moonpool's natural frequencies and are characterized by two primary modes: (1) piston mode, where ...
[78]
Resonant response of a moonpool with a recess - ResearchGate
The fatigue life of the structure inside the moonpool is predicted using suitable S-N curves from classification society rules.
[79]
Experimental study on slamming effects in a stepped moonpool ...
Jun 15, 2024 · The presence of steps in the moonpool is a crucial structural element that leads to the slamming, regardless of whether the fluid inside is in ...
[80]
[PDF] Guidelines for Moonpool Assessment - eRules
1 A moonpool is a vertical well extending through the vessel from deck to bottom, providing a direct access to the sea and allowing safe and easy deployment of ...Missing: habitat | Show results with:habitat
[81]
[PDF] Resistance due to open moonpools on offshore ships
It is also well known that, during transit, an open moonpool will increase the resistance of the hull. Even so, most vessels are not equipped with any measures ...
[82]
Experimental and Numerical Study on the Flow Reduction in the ...
Sep 25, 2017 · From the model tests, it was found that the internal flow of the moonpool was significantly reduced by the application of the wave absorber. In ...
[83]
[PDF] CFD simulation of the moonpool on the total resistance of a drillship
Aug 16, 2018 · The varying cross-section geometry is one of the practically possible and economically feasible solution to reduce the oscillation to a ...
[84]
Moonpool dimensions and position optimization with Genetic ...
Mar 1, 2022 · In this work, we present a method to optimize the moonpool profile (its dimensions and position in the hull), minimizing water motion inside ...
[85]
Moonpool dimensions and position optimization with Genetic ...
In this work, we present a method to optimize the moonpool profile (its dimensions and position in the hull), minimizing water motion inside moonpool, ...
[86]
Drillship Moonpool Design to Reduce Added Resistance for Fuel ...
May 2, 2016 · This paper reports a real case study for reducing moonpool added resistance by model tests and Computational Fluid Dynamics (CFD) simulations.
[87]
Hydrodynamic-aerodynamic performance of a barge-type floating ...
Apr 16, 2025 · This study investigates the hydrodynamic and aerodynamic performance of a barge-type floating offshore wind turbine (FOWT) equipped with four moonpools and ...
[88]
Preliminary investigation of the effects of a trapezoidal moonpool on ...
Apr 1, 2025 · This paper aims to examine the effects of the geometry of the moonpool of a barge-type Floating Offshore Wind Turbine (FOWT) substructure on the operation of ...Missing: emerging | Show results with:emerging
[89]
Investigation of coupled motion and power generation ...
Jul 1, 2025 · At lower wind speeds, the wave energy devices of the moonpool-type floaters deliver substantial power supplementation, while the water turbines ...
[90]
Analytical and Numerical Analysis of the Dynamics of a Moonpool ...
In this work the hydrodynamic performance of a novel wave energy converter configuration was analytically and numerically studied by combining a moonpool ...
[91]
Multiple moonpools within a vessel free to heave and pitch
The fixed vessel cases with moonpools studied experimentally in Garad et al. (2021Garad et al. ( , 2023 and numerically in Garad et al.
[92]
The Research of Moonpool Size Effect on the Hydrodynamic ...
A study of the moonpool size effect on such performance of FDPSO hull is presented in this paper, making use of numerical analysis and model tests techniques.
[93]
Mining the ocean floor vs mining the Moon: what can we learn from ...
Feb 3, 2025 · This perspective piece examines the parallels and distinctions between ocean floor mining and potential lunar extraction.Missing: pool analogs