Design Rationale of the Nomad 1000 Multi-purpose Diesel Electric Submarine
By: L. Bruce Jones
The last three decades has seen the construction of three separate and distinct types of manned undersea vehicles. These three categories are 1) military submarines, 2) manned submersibles and 3) tourist submersibles. Over 50 examples of each category have been constructed since 1960.
A new company, U.S. Submarines, Inc., has developed a line of diesel electric submarines that combine characteristics of each of the three categories above to essentially form a fourth type of manned undersea vehicle suited for private luxury use and commercial and research applications. This article examines the development of the design rationale as it relates to the three basic manned undersea vehicle types taken within the context of their applicability to commercial operations.
2. Military Submarines
Autonomous diesel electric and nuclear submarines have had significant strategic military importance during this century. Today, there are 11 countries that produce military submarines. Of these, only the United States, with 121 vessels, has a submarine force that is entirely nuclear powered. The former Soviet Union recently had a fleet of 311 submarines, 175 of which were nuclear. Great Britain, China and France have a mixture of both nuclear and diesel electric submarines, while the remaining submarine producers, Germany, Sweden, Japan, Italy, Netherlands, and Yugoslavia have relatively small fleets of diesel electric boats. The total number of submarines belonging to all 11 countries is approximately 649.
There are 32 additional countries that operate approximately 185 diesel electric submarines built by one or more of the 11 submarine producing nations. Approximately 50 midget submarines are estimated to be operational as well.
Military Submarine Milestones
The World War II German Type XXI submarine represented a quantum leap forward in submarine design due to developments in hull hydrodynamics and propulsion systems. The Type XXI design formed the basis for the U.S. Guppy class boats (Greater Underwater Propulsion Performance) which achieved double the submerged endurance and range of their predecessors.
A second equally dramatic development was the 1953 launch of the diesel electric test vehicle Albacore , a streamlined, teardrop-shaped hull with a fin-like sail that achieved a submerged speed of 33 knots. The Albacore form provided the cornerstone for the development of virtually all subsequent diesel electric and nuclear submarine hulls.
In 1955 the world's first nuclear powered submarine, the Nautilus , was launched. With virtually unlimited submerged endurance and later, the capability of high speeds, nuclear powered submarines became the most significant weapons of the 20th century.
Today, the former Soviet Alpha class attack submarines are capable of submerged speeds of 45 knots and diving depths in excess of 2500 feet, while U.S. submarines are known for their stealth characteristics, advanced weaponry and sophisticated electronic systems which make them the most capable submarines in the world.
Relevance to Commercial Applications
Military submarines are designed around their weapons systems. While highly effective for their intended purposes they have no commercial variants or applications and their drawbacks can be characterized as follows:
- very high acquisition and operating costs
- high number of skilled crew required
- no viewports, with no retrofit possibilities
- cramped spaces and complex systems
- designed as a weapons platform
An artist rendering of the new Seawolf.
3. Manned Submersibles
In the period from 1950 to 1980, well over 140 non-military manned submersibles were built world wide. Used principally for scientific research or in support of off-shore oil exploration, these vehicles were very popular in the 1970s when such firms as Lockheed, General Dynamics, Rockwell, General Motors and Westinghouse were involved in the industry's development. These vehicles varied substantially in size and capability though they were characterized by a number of traits that served to separate them from military submarines.
Virtually all of the manned submersibles built during this period required a support system. In most cases the support system included a mother ship capable of launching and retrieving the submersible vehicle. At the very least a tow vessel or tender was required during dive operations. With two exceptions, all of the submersibles were battery powered, and as a consequence they had limited range, speed and endurance. Because observation was almost always an important factor, the submersibles had viewports of varying size and geometry and the vehicles tended to be designed for slow speeds and excellent maneuverability, which included the ability to "hover" over a given spot on the sea floor.
A combination of the low speed requirements in conjunction with the fact that the submersibles were removed from the water after virtually every mission, meant that much of the required equipment was attached to the outside of the pressure hull where it did not detract from the already severely limited interior space, and where it could be easily serviced between dives. In addition, external equipment minimized the vehicle displacement and thus the weight - a critical factor when the submersible had to be launched from, and recovered to, a mother ship.
Today, with a few exceptions, manned submersibles have largely been supplanted by remotely operated vehicles (ROVs) that have proven quite effective and are less costly to operate in commercial application. Scientific research, where direct observation is critical, remains the cornerstone for operating manned submersibles and three notable vehicles capable of diving to 6,000 meters (20,000 feet) have been built in recent years, Mir 1&2 and Shinkai 6500 .
In general, manned submersibles have the following disadvantages:
- small size, very cramped interior
- severely limited range and endurance
- base aboard expensive support ships required
- generally dated technology
The Remora 2000 being recovered to its support ship.
4. Tourist Submersibles
The first purpose-specific passenger submarine was the Auguste Piccard, which was built for the Swiss National Exhibition in 1964. During its 16 months of operation in Lake Geneva, the submarine, which was capable of diving to 2500 feet, carried 32,000 people during 1,012 dives to depths of up to 200 meters.
In the mid-1970s Kawasaki Heavy Industries executed a design for a 40- passenger tourist submarine, but the vehicle was never built. It was not until the advent of a company named Research Submersibles Limited (RSL) in 1983 that contemporary passenger carrying operations were established; however, the vehicles were converted commercial submersibles with a limited seat capacity of one pilot and two observers. They plied the depths of the famed Cayman Wall, often to 600 meters. RSL still exists today and routinely operates its Perry-class submarines to the 250 meter foot level.
In 1984 a British Columbia based company, using the Auguste Piccard as inspiration, designed and built a 28-passenger tourist submarine, the Atlantis I , that began operations the following year in Grand Cayman. The same company had placed two more vehicles in service by 1987, and at that time other companies began to enter the business and establish operations of their own.
Today the numbers speak for themselves. The list of tourist submersibles now has 56 entries that account for 1894 seats, and the industry while showing recent signs of some readjustment is still slated for some significant growth lasting well into the next century.
With ticket prices ranging from US$55 to $285 the economic imperative is clearly the motivating factor behind the design, construction and operational establishment of these vehicles. Indeed, some operators measure their profits in millions of dollars per year.
Tourist Submersible Design
Not surprisingly, virtually all contemporary tourist submarine designers had developed their experience in the execution of manned submersibles. As a consequence, all of the tourist submarines manufactured to date have reflected those philosophies that characterized manned submersible design, with one major exception; in most cases the substantial weight of purpose specific built tourist submarines precludes their removal from the water, except for an annual haul-out for inspection and maintenance.
Military submarines provide a juxtaposed design philosophy where the vehicles are autonomous, and hydrodynamically efficient. Additionally, all major systems and components are located inside the pressure hull where they can be easily serviced.
One could argue the point that tourist submarine designers may have been better served to adopt some of the military submarine design philosophy. For instance, virtually all tourist submarines must be towed back and forth to their dive site, as their limited speed (3 knots maximum) and battery capacity precludes autonomous transit. Fitting a diesel engine would provide surface transit capability and would allow for the charging of batteries and high pressure air tanks while underway.
In many cases the number of dives per day are limited by the battery capacity. Yet clearly, streamlining the hull would allow more efficient operation and extended endurance. Moving major components from outside the pressure hull to its interior would also increase reliability and reduce maintenance. Interestingly enough, the major argument against internal arrangement of equipment in manned submersibles was that a larger pressure hull dramatically increased displacement and made surface launch and retrieval difficult. However, in tourist submarines, the majority of which displace over 80 tons and are removed from the water only once a year, such an argument is untenable.
Moreover, the added cost of construction of a larger hull would be amortized by the reduction of maintenance costs.
The similarity in lackluster performance and capability that is shared by all contemporary tourist submarines stems from the complete adherence to the manned submersible design philosophy. The disadvantages to tourist submersible designs are:
- battery powered only
- low speed, endurance and range
- dependent upon support boat
- high maintenance from external equipment
- high drag coefficients
A 48-passenger tourist submersible.
5. U.S. Submarines' Design Philosophy
At U.S. Submarines, Inc. we set out to design a new type of contemporary diesel electric submarine that would overcome the disadvantages inherent in military submarines, manned submersibles and tourist submersibles. Our first design was the 20-meter (65-foot) Nomad 1000 , billed as the world's first personal luxury submarine the vehicle is also well suited for scientific research and as a 24-passenger tourist submarine. More recently we have been retained to design larger vehicles, the 36-meter (120 foot) Seattle class and the 65-meter (213 foot) Phoenix . The advantages of these designs are:
Speed, Range & Endurance
- excellent speed, range and endurance
- superior viewing
- good surface stability characteristics
- high levels of comfort
- contemporary technology
- exceptional maneuverability
- excellent depth capability
- contemporary styling
- hydrodynamic efficiency
- low maintenance requirements
- ease of operation
- levels of safety consistent with ABS class
Battery powered manned submersibles and tourist submersibles are very limited in speed, range and endurance. Typical mission times for manned submersibles are measured in hours, with submerged or surface ranges of approximately 10-15 miles. Larger tourist submersibles in the 48 passenger, 100 ton size range are typically designed for 8-12 one-hour dives at speeds of approximately 0.5 - 1.0 knot. At a maximum speed of 3 knots the batteries would be discharged much faster.
The Nomad 1000 is powered on the surface by twin 250 HP turbo diesels driving a single shaft through a transfer system and F-N-R reduction gearbox. Submerged power is from a 240 VDC shunt wound (85 kw) 110 HP electric motor/generator. Surface speed is essentially limited to 12 knots by waterplane area, with 1000 nautical mile surface range. As a 24-passenger tourist submarine, the Nomad is 4-times faster than its counterparts, with 50 times the range.
The Seattle class has a 3000 nautical mile range with a maximum speed of 15 knots, while the Phoenix is capable of 4000 nautical miles with a top speed of 18 knots.
In leisure, sight-seeing, research and commercial applications external viewing is critical. The Nomad has 35-inch diameter hemispherical sector side viewports and a 50-inch forward viewport. The hemispherical shape is structurally superior to equivalently sized flat viewports and allows a better downward view as well.
We have attempted to make the submarines' surface characteristics as ship-like as possible. Large main ballast tanks on the order of 25% of displacement and located well outboard provide significant freeboard and stability, while inverted bow tanks of substantial size provide critical buoyancy forward. Lightweight materials above the waterline smooth the transition between GM and GB, as does the location of the ballast weights, drop weights and trim weights, all low between the skids. In addition, all the submarines are equipped with an active roll stabilization system capable of reducing the magnitude of the roll by up to 80% when underway.
High Levels of Comfort
The luxury versions of the Nomad, Seattle and Phoenix class boats have interiors designed by the reknown Glade Johnson Design. A full galley, head and shower with luxury sleeping accommodation characterize each design. The Phoenix , with a 6.7 meter (22 foot) diameter pressure hull and two main decks as well as a surface saloon has over470 square meters (5000 square feet) of interior space. In addition, automated climate control systems maintain comfortable cabin temperature and humidity levels at all times.
The advent of automated control systems and reliable electronic, acrylic, diesel and battery technology is largely responsible for these vehicles. Twin industrial CPUs with animated graphic touch screen monitors control 500 I/O blocks through a single twisted pair cable. Engine and motor performance is tracked and maintenance alarms are set at required intervals. As a result, manning requirements are minimized and safety levels are improved.
All of our diesel electric boats are equipped with four hydraulic maneuvering thrusters, one each transverse mounted at the bow and stern and two vertical thrusters. Maneuvering control is through a digital proportional joystick, and the submarine can rotate in its own length, sidle in either lateral direction or move precisely up or down in the water column.
The Nomad, Seattle and Phoenix class submarines are all classed to 305 meters (1000 feet). The pressure hulls are built to American Society of Mechanical Engineers (ASME) Pressure Vessels for Human Occupancy (PVHO-1) standards. In the case of the Nomad , the pressure hull is 1 inch ASTM 537 steel with stiffening rings on a 20 inch frame spacing.
Noted naval architect Howard Apollonio was retained to provide the styling for the superstructure of the submarines, resulting in a unique contemporary "yacht-like" look.
Manned submersibles and tourist submersibles have a large number of unfaired external components that serve to increase parasitic drag. While the Nomad, Seattle, and Phoenix have oversized "sails" above the waterline we have endeavored to streamline the design and optimize propulsion performance and efficiency wherever possible. The end result is maximum submerged speeds that vary from six to ten knots.
The difficulty of submarine maintenance is inextricably linked to design in conjunction with equipment selection. With experience in the construction, maintenance and operation of over 50 manned submersibles and tourist submersibles we have specified proven equipment, materials and components. In addition, wherever possible we have placed equipment inside the pressure hull for ease of access.
Ease of Operation
Pilot work-load has been reduced by the computer based automated control and monitoring system in conjunction with intuitive digital proportional joystick controls. Care has been taken to consider biomechanics and other human engineering factors in the design of the vehicle.
Safety & ABS Class
All of our submarines are classed +A1 Manned Submersible by the American Bureau of Shipping (ABS). The ABS has classed the majority of the world's manned submersibles and there has never been a serious injury or fatality in any ABS classed submersible. This year alone, the tourist submersible industry will carry 2 million passengers and the industry still maintains a perfect safety record.
The Phoenix 1000 from U.S. Submarines, Inc.
6. Market Opportunities
Because of the very expensive nature of nuclear military submarines and developments in the worldwide strategic situation we are apt to see significant reductions in the world's nuclear submarine forces. Recently. CIS forces have decommisioned over 120 submarnes, and by the year 2000 America's submarine fleet will probably be reduced from 121 to 65 vehicles. With the exception of the new Seawolf attack submarine the outlook for new construction is not at all bright.
The German Type 209 diesel electric submarine is the most popular export-sales submarine in the world, and sales will continue as smaller nations modernize their aging fleets. Excellent opportunities exist for smaller, conventional military submarines in this size range. However, the design costs are quite high. U.S. Submarines has negotiated a cooperative R&D agreement with the Naval Undersea Warfare Center, Keyport which would allow us to execute designs for military submarines should the opportunity arise.
U.S. Submarines, Inc. is also developing an autonomous DSRV design based on the Nomad , as we believe there is a developing market in some 20 countries for vehicles of this type.
As mentioned earlier, commercial applications of manned submersibles have largely been supplanted by ROVs. Manned submersibles are still used by the scientific community, and we see some opportunity here for a Nomad variant.
Typically, research submersibles have limited range, speed and endurance and also are quite limited in interior space. In addition, they require the use of an expensive support ship which more than doubles the daily cost of operation. A Nomad could journey out to sea under her own power and could provide scientists with a comfortable observation platform that would allow a group to cover large areas of sea floor and to stay submerged for days at a time - all at significantly less cost than conventional submersible systems with their large support ships.
The tourist submersible industry continues to grow, and there is also an increasing trend toward smaller resort-sized vehicles. We see the Nomad as being an excellent addition to this market. Compared to conventional tourist submersibles the Nomad is capable of four times the speed, seven times diving depth and 50 times the endurance. The Nomad also obviates the need for passenger transfer at sea, increasing the number of annual operating days while removing the need for a passenger transfer boat and associated crew. Recharging the batteries and high pressure air banks while transiting back and forth from base increases the number of dives the submarine is capable of making each day, while reducing the cost of associated shore facilities.
Personal Luxury Submarines
The Nomad was originally designed as a personal luxury submarine, and the market is developing in this area. In addition, we have had requests for larger luxury submarines which have resulted in the development of the Seattle and the Phoenix class vehicles. Moreover, both the Seattle and the Phoenix class boats are being evaluated for use as overnight submarine excursions as a part of the growing high-end adventure travel industry.
At U.S. Submarines we believe that we have successfully created a new category of submarine through the innovative adaptation of demonstrated technology. With aggressive marketing, our vehicles will increase in popularity in the decades to come. While the cost of these vehicles will preclude their commonplace occurrence, certainly we will see the advent of submarine tours and overnight specialty trips that will be accessible to those with sufficient interest.
L. Bruce Jones