Composites Road to the Fleet A Collaborative Success Story

Transcription

1 SPECIAL REPORT 306: NAVAL ENGINEERING IN THE 21ST CENTURY THE SCIENCE AND TECHNOLOGY FOUNDATION FOR FUTURE NAVAL FLEETS Composites Road to the Fleet A Collaborative Success Story John P. Hackett Northrop Grumman Shipbuilding - Gulf Coast Paper prepared for the Committee on Naval Engineering in the 21st Century Transportation Research Board 2011

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4 Composites Road to the Fleet A Collaborative Success Story JOHN P. HACKETT Northrop Grumman Shipbuilding - Gulf Coast T his paper traces the history of Northrop Grumman Shipbuilding Gulf Coast s (NGSB-GC) quest to bring composite materials to naval shipbuilding and the fleet. It will show the initial NGSB-GC independent research and development activity in composites, eventually leading to teaming with the U.S. Navy on major composite projects. Numerous small projects became stepping-stones that enabled larger projects to go forward. Examples of composite applications that made it to the fleet, as well as some that did not, will be addressed. One example of a successful project the development of the Advanced Enclosed Mast/Sensor System mast concept [its design, manufacture, test articles, and installation on the USS Arthur W. Radford (DD 968) as a demonstration] and eventually its implementation on the LPD 17 class of ships will be discussed. Another case study, the DDG 51 Flight IIA composite hangar (which although a technical success did not make it to the fleet), will be addressed. The composite high-speed vessel demonstrated the use of composites for the forward one-third of its 290-foot long hull with its complex shape. These large composite structure successes made the next step, of a composite superstructure with embedded antennas and low observability, an achievable goal. The DDG 1000 class, with a composite superstructure, will become the first class of large U.S. Navy ships so outfitted. INTRODUCTION This paper addresses the history of composites at Northrop Grumman Shipbuilding Gulf Coast (NGSB-GC) and its predecessor companies, Northrop Grumman Ship Systems (NGSS), Litton Ship Systems, Ingalls Shipbuilding, and Avondale Industries. Northrop Grumman Shipbuilding (NGSB) is a defense contractor building state of the art navy warships that must be highly mission capable and survivable. The ships built by NGSB include amphibious assault ships, cruisers, destroyers, corvettes, and cutters at NGSB-GC, and nuclear powered aircraft carriers and submarines at NGSB Newport News. A research and development (R&D) group was established at Ingalls Shipbuilding in 1975 to perform research that would influence future acquisitions for the shipyard. Among the projects undertaken by this group were numerous studies on weight-saving structures and corrosion resistant materials. Ingalls had been the lead shipyard for the FDL (fast deployment logistics) class, the 31-ship DD 963 Spruance class destroyers, and the 5-ship LHA 1 Tarawa class amphibious assault ships in the 1970s. From the DD 963 ships, Ingalls built four derivative DDGs, the Kidd (DDG 993) class anti-air warfare (AAW) destroyers. These successes led to Ingalls being selected as the lead yard for the next class of surface combatants, the Ticonderoga (CG 47) class cruisers, which were based on the DD 963 hull and propulsion plant. Ingalls built 19 of the 27 ships in the class. The follow-on surface combatant program was the Arleigh Burke (DDG 51) class destroyers, led by Bath Iron Works, with Ingalls building half of the ships. 1

5 2 Composites Road to the Fleet A Collaborative Success Story The next U.S. Navy surface combatant acquisition program was the DD 21 program, which was envisioned to be enhanced with numerous advanced technologies and be very stealthy. The low signature requirements dictated a very smooth, flat-sided, low Radar Cross Section (RCS) topside design. The Ingalls topside design was devoid of any type of traditional mast and antennas. Instead, all sensors and antennas were completely flush with the ship s superstructure to reduce the RCS. Reducing the RCS of the topside is important since the topside is the first part of the ship that comes over the horizon and can be seen by a distant enemy radar. Ingalls had experience with low RCS design and construction since it was in the middle of the DDG 51 and Israeli SA AR 5 corvette shipbuilding programs, both of which had low RCS signature requirements. Flush mounting or enclosing, or both, all of the sensors inside a mast or superstructure requires more supporting structure than a traditional stick mast and is therefore heavier. Added weight high in any ship is not desirable, as it negatively impacts the transverse stability of the ship. This weight can be reduced by using aluminum (such as for the DD 963, CG 47, LHA, LHD, and other classes). DDG 51 class ships have a steel superstructure but compensate for the negative stability implication with a wider hull. Lightweight topside structures had been a focus at Ingalls for some time. Thin metal plate and structures are prone to weld induced distortion, which conflicts with the RCS requirements that dictate a very smooth, flat structure. Flame straightening can correct the distortion, but it is disruptive and labor intensive. The traditional naval shipbuilding material, for the last hundred years, has been steel. Aluminum has been used in specialty areas such as masts and deckhouses to save weight high in the ship. Composites have been around in the commercial sector and in the aerospace industry for many years. Recreational watercraft have been manufactured almost exclusively of composites for the last 50 years or so. Recreational watercraft composites are typically a combination of a fiberglass woven roving reinforcing material impregnated with a polyester liquid resin. When cured, this material is very strong. This material is colloquially referred to as fiber-reinforced plastic (FRP) composite. The type of marine composites discussed in this paper consists of more advanced materials for both the reinforcing material and the resin, which changes the chemistry and mechanical characteristics of the composite, making it more appropriate for a naval combatant. There are numerous benefits that marine composites offer the shipbuilder and the navy. Some of those advantages are corrosion resistance, strength, light weight, nonmagnetic, flatness, smoothness, ability to take on complex geometries, fatigue life, thermal insulation, sound dampening, and the controversial one, repairability. Both the weight and the flatness issues associated with metal structures can be remedied with the use of FRP composites. A composite deckhouse offers a lighter deckhouse than steel and a possibility of being lighter than aluminum. For this reason, the Ingalls R&D group in the late 1980s began to investigate lightweight marine composites, with the goal of providing the warfighter a ship with superior signature reduction and weight savings for the upcoming DD 21 program. It is important to understand the customer s organization, and how NGSB-GC R&D activities are organized to undertake general R&D activities, and specifically composites, which will be covered in the next two sections.

6 Hackett 3 RELEVANT NAVY ORGANIZATIONS Throughout this paper, various organizations within the U.S. Navy are mentioned. It is worth describing each organization and its principal responsibility. Naval Sea Systems Command (NAVSEA) is charged with the responsibility to design, build, buy, and maintain the various ships, submarines, and combat systems of the navy. The NAVSEA technical community designs ships to meet the Office of the Chief of Naval Operations (OPNAV) requirements. Within NAVSEA, the program executive offices (PEOs) are responsible for all research, development, acquisition, systems integration, construction, and lifetime support of their assigned programs. Although part of NAVSEA, PEOs report to the Assistant Secretary of the Navy for Research Development and Acquisition (ASN RD&A). This organizational structure was established in response to the Goldwater Nichols act of PEO Ships is responsible for all non-nuclear surface ships. The PEOs are flag officers who are typically assigned for a three year tour. Inside PEO Ships, there are individual Program Manager Ships (PMS) codes for each of the ship classes, such as PMS 400 (DDG 51 Class) and PMS 500 (DDG 1000 class). The PMSs are typically led by captains, assigned for four-year tours. The two warfare centers, Naval Surface Warfare Center (NSWC) and Naval Undersea Warfare Center (NUWC), also fall under the NAVSEA organization. Navy laboratories, such as the Naval Surface Warfare Center Carderock Division (NSWC-CD) (formerly known as the David Taylor Research Center), are also part of NAVSEA (2). The Office of Naval Research (ONR) provides technical advice to the Chief of Naval Operations and the Secretary of the Navy. ONR is headed by a flag officer, typically for a two-year tour. ONR primarily funds basic and applied research for naval applications and enabling technologies for future acquisitions (3). The Office of the Chief of Naval Operations (OPNAV) is a collection of officers and staffs that advise the President and the Secretary of the Navy on all naval matters (4). OPNAV has the responsibility for fighting on the sea, over the sea, and under the sea. As such, OPNAV owns the ships, aircraft, weapons, and systems necessary to carry out that mission. They set the requirements for the fleet of tomorrow. In order to do this, OPNAV has warfare/platform specialty organizations to support functional parts of the fleet, such as N85 Expeditionary Warfare, and N86 Surface Warfare. These organizations specify warfighting requirements and point the design and R&D communities in the direction in which OPNAV desires to move to create the fleet of the future. NAVSEA is tasked with meeting OPNAV s near term needs, while ONR is responsible for developing and maturing the technologies required for tomorrow s ships. All of these organizations make up the stakeholders for technology insertion and transition into the U.S. Navy. There is an inherent tension between the goals of these organizations: ONR to see new technology developed and matured for entry into the fleet; NAVSEA Tech Codes to see well designed, maintainable, working technology in the ship; PEO to deliver a ship to the fleet on time and within budget; and OPNAV to have the most capable warship possible to defeat America s adversaries. NAVSEA and the PEOs are responsible for taking the technology available and the new technology developed by ONR and delivering a modern, affordable, requirements-based ship to the fleet. A typical time frame for NAVSEA to develop a ship design from concept design through preliminary design and then contract design is about three years. Next, the design package is put out for bidding by the shipyards to develop a detail ship design and then to build the ship. The bidding process can take a year to complete. Detail design and construction can take four to five years for a typical surface combatant. This represents a design construction cycle time of eight to nine years, but it could be substantially longer.

7 4 Composites Road to the Fleet A Collaborative Success Story NGSB -GC PROJECT MANAGEMENT NGSB-GC s approach to running an R&D project varies depending on the scope, budget, and schedule of the particular project. Independent research and development (IRAD) projects are managed a little differently than contracted research and development (CRAD) projects. IRAD projects have team members with the following roles and responsibilities: IRAD project team members The technical point of contact (TPOC) is the lead for executing the day-to-day tasks and producing the deliverables. This person provides the deliverables and other products to the manager of R&D. The manager of R&D is part of the TPOC s management chain, ensuring quality and timeliness of the deliverables. The director of R&D is part of the TPOC s management chain. This person determines which new technologies to pursue and seeks their transition to the fleet. Business development personnel provide the point of view of both the customer and the corporation, as well as providing external oversight. Administrative support personnel provide the administrative functions such as reporting budgets and schedules. Project results are reported in an R&D technical note. Due to the customer s participation and other external involvement, CRAD projects tend to have more members. These increased roles are as follows: CRAD project team members The TPOC is the lead for executing the day-to-day tasks and producing the deliverables. This person provides the deliverables and other products to the program manager. The manager of R&D is part of the TPOC s management chain, ensuring quality and timeliness of the deliverables. The director of R&D is part of the TPOC s management chain. The contract administrator administers the contract with the customer and undertakes any legal or compliance functions. The program manager represents the company to the customer s project officer or program manager and is involved in the technical scope, schedule, and budget. Administrative support provides the administrative functions such as reporting budgets and schedules. Project result reporting is dictated by each individual contract. Typically it includes monthly technical, progress, and funding summaries; a preliminary report, and a final report. In-process reviews are periodically held with the sponsor and culminate in a final review.

8 Hackett 5 HISTORICAL CHRONOLOGY OF NGSB-GC COMPOSITE PROJECTS This section will provide discussion on how the company started with small, often IRAD-funded composite projects. Early on, many of the projects were done with the assistance of the navy lab and other composite designers and fabricators, until the company was able to design and manufacture large composite structures. The company name used in each section is that appropriate for the time the project was active. Figure 1 is a timeline of composite projects worked at NGSB-GC for the period 1989 to First Composites Experience Ingalls early experience with composites was installing Kevlar ballistic armor panels on the Kidd (DDG 993) class warships in the late 1970s and early 1980s. This was also Ingalls first time working with a navy R&D organization on composites. During that timeframe the David Taylor Research Center (DTRC), currently known as Naval Surface Warfare Center Carderock Division (NSWC-CD), was conducting large scale fatigue tests on a 1/3-scale all-aluminum destroyer model (5), the Aluminum Ship Evaluation Model (ASEM). Concerns had arisen about the long-term durability of attachment methods of the Kevlar panels on the DDG 993 class. Ingalls worked with DTRC to design and install scaled sections of the Kevlar panels on the ASEM using various attachment methods. Subsequent cyclic tests compared the efficacy of the different attachment methods. Coastal Minehunter Avondale Industries was awarded a contract in October 1989 to build four composite minehunters of the Osprey (MHC 51) class (length 188 ft, displacement 900 tons). The Osprey class is the U.S. Navy s first all-composite class of ships and is based on the Italian composite Lerici class. The lead shipbuilder, Intermarine USA in Savannah, Georgia, built the first two ships plus six additional ships of the class. Avondale s facility in Gulfport, Mississippi, built the third ship, USS Pelican (MHC 53) plus three others between 1991 and Composites were used on these ships because the material is non-magnetic, a highly desirable characteristic for a minehunter, whose mission is to enter a suspected minefield and identify the location and type of mine and then destroy it. Even the diesel engines were amagnetic. The hull is a solid laminate of glass and resin, with thicknesses between inches with no frames (6). This produces a monocoque structure designed to resist the shock of underwater explosions from mines (7). The Gulfport facility was specially outfitted to suit composite manufacturing by adding climate control to the erection hall, resin stowage tanks, catalyst stowage building, and mixing tanks, as well as overhead resin impregnators to the production areas (Reference 8). See Figure 2 for a picture of an MHC. Early Small Test Articles The Ingalls R&D organization did most of its early research under the IRAD program. U.S. government rules indicated that a portion of the company s funds expended could be reimbursed as an allowable overhead expense. As part of the IRAD regulations in place at the time, the navy would assign a person to oversee the individual company s IRAD programs. For Ingalls

9 Project Name Funding Source U.S.S. Pelican (MHC-53) PMS 490 Miscellaneous Early Small Test Articles IRAD/CRADA/NSWC-CD 1/2 Scale DDG 51 Mast IRAD/CRADA/NSWC-CD [ONR(6.2)+DNA] Hangar Module IRAD/CRADA/NSWC-CD [ONR(6.2)+DNA] 1/4 Scale AEM/S System Mast ONR ATD Composite Platform NSWC-CD [ONR(6.2)] Composite Hull Section NSWC-CD [ONR(6.2)] Full Scale AEM/S System Mast ONR ATD Composite Door IRAD Composite RCS Test Fixtures IRAD/CRADA Sealift Deckhouse MSC Maritech Deckhouse MARAD LPD 17 Composite Mast PMS 317 Integrated Topside Demonstration System (ITDS) IRAD DDG 51 Composite Helo Hangar ONR DDG 51 Remote Minehunting System (RMS) Enclosure PMS 400 Low Observable Multi-function Stack ONR Joint Modular Lighterage System (JMLS) NSWC-CD CHSV ONR CVN 77 Mast PMS 378 AESD Deckhouse ONR ATD DDG 1000 Test Articles (RCS, Joints, Fire and Shock) PMS 500 DDG 1000 Deckhouse Engineering Development Model (EDM) PMS 500 DDG 1000 Integrated Deckhouse Start Fabrication PMS 500 Litton Buys Avondale FIGURE 1 Composites research timeline at NGSB-GC. Northrop Grumman Buys Litton

10 Hackett 7 FIGURE 2 MHC-54, one of the four MHC Coastal Minehunters built by Avondale Industries. composite projects, this person was from the structures branch of DTRC. The navy was also interested in getting composites technology aboard their ships. They agreed to study several areas, such as weapons blast and composite joints (1, 9). Part of this effort would entail a series of tests that would study composites under weapons blast loads, which was part of a larger navy program called Integrated Technology Deckhouse. Testing would be conducted at a Department of Defense (DOD) facility. Both Ingalls and DTRC came to a Cooperative Research and Development Agreement (CRADA), where Ingalls would spend its own money to manufacture test articles and ship them to the Navy for testing. The Navy would bear the cost of testing the articles and share the test data with Ingalls (1). This occurred roughly between 1989 and The test articles consisted of different types of stiffened panels and modules that represented shipboard deckhouse or hangar modules. They ranged in size from several inches to two deck high structures that resembled small buildings. This was the beginning of the relationship between Ingalls and DTRC using the CRADA funding method. These tasks also showed Ingalls the advantage of aligning the IRAD program with navy priorities, especially those of the navy s applied science labs such as DTRC (now called NSWC-CD). Half-Scale DDG 51 Mast NSWC-CD designed and Ingalls built a composite half-scale mast based on the DDG 51 aluminum mast in The purpose was to demonstrate the feasibility of designing and manufacturing an affordable, lightweight structure for use on navy surface combatants. The project was performed under the CRADA funding method. Ingalls paid for fabrication and shipping to the navy test site, and the navy provided the testing. The composite mast was externally similar to the aluminum mast but structurally changed to account for the material change and built to prove the feasibility of a mast based on the DDG 51 stick mast design. It was known colloquially as the green stick mast since the finished composite structure had a green color due to the vinylester resin used. The mast was 25 ft tall and 32 ft wide at the lower yardarm. This mast was manufactured using the Seemann Composites Resin Infusion Molding

11 8 Composites Road to the Fleet A Collaborative Success Story Process (SCRIMP), which is a proprietary vacuum-assisted resin transfer molding (VARTM) method. The mast was built by Seemann Composites in Gulfport, Mississippi, with Ingalls personnel in attendance. The mast was air blast tested at the Army White Sands Missile Range facility in New Mexico. The DDG 51 composite mast withstood the air blast tests with no visible damage and was analytically shown to meet or exceed navy requirements for air blast, buckling, and seaway-induced fatigue, while providing an estimated 17% weight savings over the baseline aluminum mast (10). Figure 3 shows the mast installed at the White Sands Missile Range. Hangar Module In 1991 a program was initiated under the Ingalls/NSWC-CD CRADA funding methodology to explore the idea that a metal skeleton with composite panels attached was an economical way to manufacture integrated shipboard composites such as a hangar module. The composite panels were a standard size and were adhesively attached to a welded steel frame. The expectation was that this might offer weight savings when attempting to build a large integrated composite structure compared to other materials and fabrication methods. The panels were built by Alcoa Technical Center, Pittsburgh, Pennsylvania, because of their pultrusion expertise. To evaluate how non-magnetic composite panels would integrate into a shipyard facility, the panels were shipped to Ingalls for storage and associated handling. A two-deck-high structure, roughly 20 ft high by 20 ft long by 10 ft wide, fashioned after a section of helicopter hangar, was fabricated and the interior was outfitted with typical ship systems such as pipe hangers and pipe, light fixtures, electrical panels, etc. The outfitted hangar module was then shipped to White Sands for blast resistance testing to determine survivability of the construction and outfitting techniques (14). The expected weight savings did not materialize. Ship structure is monocoque, where the skin carries the load, and the frames are there to keep the plate from buckling. This allows the frames to be small. In this hangar concept, the beams (frames) were sized to carry all of the load, while the composite plate just kept the weather out. Therefore, the frames were much larger (heavier) than if they and the plate were a single composite structure. This was a valuable lesson from this early design. All subsequent projects used monocoque composite structure. The module passed the test (10, 13). Figure 4 shows the hangar module on the test range at White Sands. From a historical standpoint, it is interesting to note that the introduction of iron into shipbuilding in the late 19th century followed a similar path. Many ships built at the time, such as the famous clipper ship Cutty Sark, were constructed with wood planks over iron frames until the new iron material was better understood and accepted as a material system. Composite Platform Deck In 1995 NSWC-CD contracted Ingalls to study the feasibility of using composite decks in an otherwise steel ship design. Composite decks would offer high strength, low weight, corrosion resistance, and increased shock and sound attenuation performance. A half-scale test article that would test a variety of panel and joint designs and configurations was manufactured and assembled by Ingalls. Ingalls built the steel portion, and the composite panel fabrication was subcontracted to Seemann. The decks were fabricated using two different deck designs: one was a solid laminate with hat stiffeners, and the other was a sandwich panel. Analytically, both panel types performed well. The test article was shipped to NSWC-CD and was planned to be tested

12 Hackett 9 FIGURE 3 ½ scale DDG-51 mast. FIGURE 4 Hangar module.

13 10 Composites Road to the Fleet A Collaborative Success Story for shock, vibration, fatigue, and fire, but funding limitations prevented the completion of the tests. However, the experience gained from the design and fabrication led to follow-on projects. Composite Hull Section In 1995 NSWC-CD funded the fabrication of a composite quarter-scale, full beam parallel midbody hull section, akin to a PC or corvette, as part of a larger program that demonstrated that a composite ship module could be built. The section was 28 ft long by 20 ft wide by 10 ft deep. NSWC-CD contracted with four different vendors using four different composite manufacturing methods to build these test articles. Time to build and cost to build were recorded and compared across all four vendors. Ingalls and CASDE provided the engineering and design to Seemann, who built the hull section using the SCRIMP VARTM manufacturing process. It was tested at various locations, including a flexure test at Lehigh University, and tested to destruction at a facility in Germany. This test article was deemed to be the highest quality of the four that were procured. It passed all tests. See Figure 5 for a picture of the hull section (12). AEM/S System Mast Traditional ship stick masts suffer from sensor blockage from the structure of the mast itself, experience sensor maintenance and preservation issues associated with the corrosive atmosphere in which they operate, and have a high radar cross section due to the large number of components and the multitude of shapes present. A new generation of mast was required to overcome these deficiencies. The composite Advanced Enclosed Mast/Sensor (AEM/S) System mast addresses all of the shortcomings of the legacy mast by enclosing the sensors inside the mast structure and having a flat faceted reflective shell to reduce the RCS of the mast. This protects the sensors inside the mast from the weather, the sun, and the high temperature and corrosive gases of the exhaust plume, as well as provides a safer environment in which to perform any maintenance on the sensors. The make-up of the composite structure that encloses the radars is tuned to the frequency of the radar behind it. This allows only the desired frequency FIGURE 5 Composite hull section.

14 Hackett 11 to enter and exit the composite mast shell, and to reflect all other frequencies (15). ONR supported the basic research and applied research associated with developing the science to allow an AEM/S System to go forward. Extensive testing was performed to validate the theory. An early part of the technology demonstration effort was the construction and testing of a quarter-scale test article. Quarter-Scale AEM/S System Mast Ingalls was contracted to build a quarter-scale composite mast that met all the standard navy design requirements. It was built in the east bank composite shop, with the help of Seemann during Seemann designed and built a unique rotating fixture for the mast s fabrication, which allowed for all the fabrication to be completed in the downhand position to increase production efficiency. The quarter-scale mast was successfully tested at the Large Blast/Thermal Simulator at White Sands. (15). AEM/S System Advance Technology Demonstration The advanced technology demonstration (ATD) was an ONR-funded risk mitigation effort for the AEM/S System mast. It was initiated in As with any ATD, the key to obtaining authorization to proceed was dependent on convincing the OPNAV staff of the warfighting value of the technology. With that endorsement, AEM/S System development became a warfighter pull as well as a technology push. There were many new and untested technologies associated with the AEM/S System, and the ATD was structured as a risk-reduction program. New engineering methods for the design and manufacture of large composite structures that would meet combatant requirements were developed. Extensive testing was performed to validate the design. Full-Scale AEM/S System Mast The AEM/S System ATD mast, at 87 ft tall and 35 ft in diameter, was the largest composite component built by Ingalls up to that time. It was built in 1996 and was installed aboard the USS Arthur W. Radford (DD 968) in May It was intended to remain aboard the ship for only six months for test and evaluation, but in May 1998, the captain of the ship requested that it remain installed for the life of the ship (16). The radars worked better, since there was minimal structural blockage to the viewing angles of the radar. It was safer, since any sailors that had to go up the mast to perform maintenance were safely inside the mast and not climbing a stick mast out in the weather. The ruggedness of the mast was proven during a pair of unplanned events. Unfortunately, in February 1999, the Radford was involved in a collision with the cargo ship Saudi Riyadh during night operations just off the coast of Norfolk. There was no loss of life, but the ship was severely damaged. There was no resulting damage to the AEM/S System mast structure. Also during its time aboard the Radford, the mast survived a nor easter at sea, again with no damage to the mast structure or antennas. The project was deemed a complete success, having exceeded all of its goals (15, 17). The success of the AEM/S System mast also prompted numerous press releases, articles, technical papers, and even an ONR Naval Technology Achievement award for one of the principals (19, 20). See Figure 6 for a picture of the AEM/S System mast installed aboard the USS Radford.

15 12 Composites Road to the Fleet A Collaborative Success Story FIGURE 6 USS Radford at sea with AEM/S. LPD 17 AEM/S System Masts As the AEM/S System mast program for the USS Radford was underway, key navy personnel in the Pentagon (OPNAV) became convinced that this was the right technology for the upcoming LPD 17 (San Antonio class) program. LPD 17 is an amphibious assault ship that had a requirement to have lower RCS signature than previous amphibious ships. At the end of contract design and at the time of award of the LPD 17 design and construction contract to Avondale Industries in December 1996, the design requirements had two conventional metal stick masts, both similar to the DDG 51 mast. During engineering development of the LPD 17, it was determined that an AEM/S System mast would provide a real warfighting benefit in helping to reduce RCS. The Program Manager s (PMS 317) initial plan was to transition from the stick masts to the AEM/S System masts starting with LPD 22 (23). The delay would provide time to address any unresolved issues. The program manager had an active risk mitigation effort underway. The AEM/S System ATD demonstration on the USS Radford was one of those efforts; others were the navy developing manufacturing methods and design tools for use by the shipyards. There was strong support from some parts of OPNAV and resistance from other parts. Likewise, the technical community was split: NSWC-CD was a strong advocate while some of the NAVSEA tech codes were reluctant. The LPD 17 program manager and PEO worked closely with the various warrant holders to resolve any open issues and weighed the benefits to the operator of having all of the ships in the class outfitted with the AEM/S System mast beginning

16 Hackett 13 with the first ship of the class. Funding was put together from within the navy to accomplish this change. While the composite technologists were important in the transition of the AEM/S System to the lead ship design, there appears to be limited active advocacy on the part of ONR and the shipbuilder directed towards the LPD 17 program office to incorporate the AEM/S System mast. In 1998 the program manager made the decision to change from the two metal masts to the composite AEM/S System masts. Avondale was advised only when the project was ready to begin construction implementation negotiations. Avondale was directed to proceed in August 1998 (22). The FY 1999 Department of Defense Appropriation Act approved the navy s plan and directed the navy to outfit LPD 17 and LPD 18, as well as the remainder of the class, with AEM/S System masts (26). In March of 2000, construction started on the AEM/S System masts for LPD 17 at the Gulfport facility. This was the first composite project to be built there since the Coastal Minehunters more than 10 years earlier (8). Start of fabrication of the LPD 17 hull at Avondale was June of See Figure 7 for a picture of the LPD 17 AEM/S System mast during assembly at the Avondale shipyard. This project is notable as it is the first time a large composite structure was installed on the first of a class ship and because the change was made after the construction contract was awarded to the shipbuilder. The main mast is approximately 42 ft in diameter at the base and 80 ft tall. See Figure 8 for a picture of the LPD 17 on sea trials in Composite Door Standard navy closures have had many problems associated with durability, operability, and survivability for years. In 1996, Ingalls addressed the need for an improved door design; the company was replacing or reworking damaged watertight doors at an alarming rate. The shipyard build strategy was to fabricate structural assemblies of decks and bulkheads of about 70 tons. A FIGURE 7 AEM/S mast being installed on LPD-17.

17 14 Composites Road to the Fleet A Collaborative Success Story FIGURE 8 LPD-17 on sea trials. significant amount of preoutfitting of systems (pipe, wireways, lights), and components, including installation of doors and hatches, then occured. The assemblies were then moved from the preoutfitting station to the ship assembly location for landing on the ship. Assemblies were joined together to produce the ship. The damage was due to shore-based translation, which caused excessive bulkhead racking and increased loads to structural elements such as doors. It was thought that if the door design could be improved, then door replacement could be minimized. The navy had long been expressing concerns about the maintenance cost and the operation of the navy standard doors. These concerns were important factors in the design, including but not limited to, fatigue failure of hinge parts, operating torques, maintenance requirements, and structural integrity during ship motions. To respond to these concerns, Ingalls, with IRAD funding, designed a composite door that was lightweight and corrosion resistant, and had a low RCS. All of the concerns were addressed and effective solutions were provided. The door passed both the shock and hydrostatic tests as described by military specifications. The door is a fully functioning and qualified U.S. Navy door that has reduced RCS and is lightweight (27). The composite low observable door design will be used as the exterior weather doors on the DDG 1000 superstructure. Figure 9 shows a picture of the door undergoing RCS testing.

18 Hackett 15 FIGURE 9 NGSB composite door. Sealift and MARITECH Deckhouses Military Sealift Command (MSC) and the U.S. Department of Transportation s Maritime Administration (MARAD) each had manufacturing technology demonstration programs in MARAD had a technology development program called MARITECH, whose aim was to improve ship design and construction processes in U.S. shipyards. The objective of the MARITECH deckhouse was to learn to mass-produce relatively simple fire-resistant composite panels (29). These panels were joined with a unique joining method. The corner joints were made with composite pultruded angles and a structural adhesive. The deckhouse-like structure was roughly 20 ft by 30 ft. The MSC deckhouse was similar in size and goals but used bolted joints to attach the composite panels to steel shapes (12). Figures 10 and 11 are pictures of the two deckhouses. Integrated Topside Demonstration System (ITDS) By 1999 the R&D group at Ingalls had garnered extensive composite design and manufacturing experience. The AEM/S System mast had provided large-scale, low RCS structural experience and an appreciation for the requirements of radars and electronics. The new DD 21 class of ships had signature requirements that were more restrictive than those of any other U.S. Navy surface ship. Thus, DD 21 was envisioned with a tumblehome flat-sided superstructure. Using flush planar antennas made the mast structure so large, it extended most of the length and width of the superstructure, making it look like an extension of the ship s superstructure. This is called an integrated deckhouse. The DD 21 design and construction competition was approaching, which Ingalls was striving to win. The R&D group at Ingalls envisioned a test article that demonstrated

19 16 Composites Road to the Fleet A Collaborative Success Story FIGURE 10 Sealift deckhouse. FIGURE 11 MARITECH deckhouse. the technology needed for the DD 21, named the Integrated Topside Demonstration System (ITDS). By funding the project internally (IRAD), Ingalls controlled the technical scope and schedule. It achieved a low RCS signature by incorporating conformal planar arrays as well as low RCS mechanical and electrical items such as lights, doors, and countermeasure washdown nozzles. The entire structure was RCS tested at the Ingalls newly constructed east bank radar range, called Point Buck (1). The Ingalls R&D group had heard that the aerospace community was actually embedding active antennas into the structural composite laminate for aircraft; this would allow the antenna to provide increased strength and stiffness to the laminate. The R&D group located a collaborating antenna vendor, Ball Aerospace, that had this enabling technology. Other larger

20 Hackett 17 antenna vendors were contacted but either did not have an antenna or did not want to invest in developing an antenna for shipboard operations. Ball developed its technology in cooperation with Ingalls, so the antenna would work when embedded in the composite structure. Ball provided its own funding to develop the antenna (1). The Ball antenna was for communications. Once the project was underway, other antenna vendors such as Litton Electronic Data Systems, Harris, and Raytheon chose to get involved. The project was moving very fast now, and Ingalls was trying to complete ITDS in time to influence the DD 21 competition. The other antenna manufacturers, now on the team, provided non-functioning RCS surrogate conformal antennas which were inserted in the composite structure. To accomplish this, a hole the size of the antenna was cut out of the composite panel after it was laminated, the perimeter was reinforced, and the antenna was bolted in at the edges. This method came to be known as a picture-frame mounting. However, it degrades the structural performance of the surrounding laminate (1). The Ball antenna system was operational, and when ITDS was finished, one could enter the two-deck composite structure and activate the functioning Ball antennas, which were on two of the four structural faces. In addition, they were able to demonstrate not only the hardware as installed but also the software developed by Ball to seamlessly transfer from one face to the other without losing signal strength. Largely due to their efforts on ITDS, Ball won the competition for the DD 21 (now called DDG 1000) Multifunction Mast (MFM) (12). The R&D group later learned that the aerospace community was not embedding antennas; they were mounted via the picture frame method. Ingalls was never able to confirm, but it is believed that the Ball antenna was the first embedded antenna (1). Unfortunately, the approved mounting method for the DD 21 antennas came to be the picture-frame method, which required much more structure than if the antennas had been embedded. ITDS was manufactured at Ingalls east bank composite facility, tested at the Point Buck radar range, and proven a complete success. All the mechanical and electrical demonstration items worked perfectly. It was completed in time to be demonstrated to the U.S. Navy representatives overseeing the DD 21 competition. ITDS proved that Ingalls, now called Litton Ship Systems, could build and integrate all the technology needed to bring the DD 21 topside out of the world of PowerPoint presentations and into reality. This was a key aperture and composite integration demonstration that served to make the overall integration risk more manageable. The ITDS technology, combined with the composite material system, provided Litton Ship Systems with a significant discriminator for the DD 21 competition. See Figure 12 for a picture of ITDS. Composite Hangar DDG 51 A logical stepping stone between the AEM/S System mast and a composite mast and superstructure for the DD 21 [by this time known as DD(X)] was a large deckhouse structure. It would address many of the integration challenges associated with a composite deckhouse attaching to a steel structure, and have typical navy outfitting. The DDG 51 Flight IIA ships being built at that time were outfitted with a steel helicopter hangar. The idea of a composite hangar was discussed between the NGSS R&D and NSWC-CD. If the upper portion of the steel hangar could be made of composites, it would save weight for the ship and allow a significant amount of outfitting techniques to be explored and demonstrated. NSWC-CD and NGSS R&D discussed the idea with PMS 400 (the DDG 51 program management office). In 1999 ONR funded the composite hangar project. A project plan was developed for potential installation on

21 18 Composites Road to the Fleet A Collaborative Success Story FIGURE 12 ITDS with embedded antennas infused composite panels. DDG 97, 100, or 103. Included in the plan were many risk mitigation items, one of which was the design and manufacture of a test article that would be outfitted with typical services that would be found in a helicopter hangar: wireways, light stands and lights, electrical panels and foundations, piping systems, etc. This test article measured 18 ft tall by 10 ft wide by 30 ft long. The test article was built and barge shock tested, after which a fire test was performed. It successfully passed both tests. A detail design for the hangar was initiated. PMS 400 directed NGSS to warranty the composite structure for the life of the ship, something that had never been done before. A typical warranty period for an entire ship is 12 months. A compromise warranty was priced into the contract for the ship, but the navy deemed the cost of that warranty unaffordable and terminated the program (1). See Figure 13 for a picture of the area of the hangar that was to be composite. FIGURE 13 Area of composites (in green) on DDG-51 Flight IIA hangar.

22 Hackett 19 In 1999 Litton Industries acquired Avondale Industries and merged them with Ingalls to create Litton Ship Systems. This made the Avondale composites facility in Gulfport, where the MHC minehunters were built, available for future Litton Ship Systems composite projects. Gulfport is an ideal composite manufacturing facility. Over the next few years, the company phased out all non-composite fabrication at the Gulfport facility. Remote Minehunting System Composite Enclosure DDG 51 Late model DDG 51 Flight IIA class ships, starting with DDG 91 USS Pinckney, were to be outfitted with a Remote Minehunting System (RMS). RMS is built by Lockheed Martin and is also known as AN/WLD 1(V). It is an off board sensor that is roughly 23 ft long and weighs approximately 14,000 lbs. This unmanned vehicle and its launch-and-retrieval davit would be located on the starboard side at deck edge, just forward of the hangar. The RMS vehicle, handling davit, and associated gear were to be stored in a weathertight enclosure. The DDG 51 superstructure is steel. The RMS, handling davit, and steel enclosure created a significant starboard list (rotation about the fore and aft direction of the ship caused by off center weights) on the ships. One possible improvement was to change the material of the RMS enclosure from steel to composites. PMS 400 authorized a Shipbuilder Special Study in 2000 to investigate a composite enclosure. Litton Ship Systems built a test article. Unfortunately, the list incurred from the RMS, associated handling equipment, and its lightweight composite enclosure was still outside of the allowable list for the DDG 51 class. After five DDGs were outfitted with the steel enclosure, the U.S. Navy decided to terminate the RMS program for future DDG 51s. See Figure 14 for a picture of the RMS composite enclosure test article under construction (30). FIGURE 14 RMS Enclosure under construction.

23 20 Composites Road to the Fleet A Collaborative Success Story Low Observable Multifunction Stack The Low Observable Multifunction Stack was an ONR-funded effort led by NSWC-CD in 2001 to demonstrate some of the technology needed to meet the DD 21 requirements and goals for signature reduction. NSWC-CD and Temeku Technologies developed a technology that would reduce the infrared (IR) signature associated with the hot gas turbine exhaust leaving the ship through the stack. Building on the success of the Ingalls ITDS, the Low Observable Multifunction Stack would have planar antennas mounted using the picture frame method. The detail design and fabrication of the composite stack were performed by Litton Ship Systems. When construction was completed, it was RCS-tested at Point Buck by a Litton Ship System/NSWC-CD team. Next the stack and IR suppression system was installed on the NSWC- CD CODOG (Combined Diesel or Gas Turbine) research vessel Lauren (1, 31). This project continued the longstanding relationship between Litton Ship Systems and the R&D community at NSWC-CD. Navy feedback indicated that the program met its objectives and passed all tests. See Figure 15 for a picture of the Low Observable Multifunction Stack on the Lauren. In April 2001 Litton Industries was purchased by Northrop Grumman Corp. (NGC) (32). Litton Ship Systems was renamed Northrop Grumman Ship Systems (NGSS). This gave the R&D group access to the other composite engineering and manufacturing centers throughout NGC. It allowed the various groups to collaborate and learn each other s facilities, capabilities, skills, and strengths. The Gulfport composite manufacturing facilities underwent a multimillion dollar capital investment (28). This investment provided Gulfport the largest five-axis machining center in the United States. The facilities include over 400,000 square feet of climate-controlled manufacturing areas. It has over 25,000 square feet of flat tooling (including two of the largest flat tools anywhere). The tooling is outfitted with laser image projectors to aid manufacturing layout. FIGURE 15 Low Observable Multifunction Stack installed aboard LAUREN.

24 Hackett 21 Joint Modular Lighterage System The U.S. Navy has a system for moving supplies and equipment off cargo ships and to the beach in the event that a deepwater port is not readily available. This is called Navy Lighterage. The legacy system is a barge-like vessel made of steel buoyancy tanks. The Lighterage system is designed to be carried on a cargo ship and handled with the ship s crane. Since the legacy system is heavy and prone to severe corrosion, it was a perfect candidate for composites. NSWC-CD funded this project in 2001 to manufacture a composite prototype section to an NSWC-CD design. The contract was awarded to NGSS in August 2001 to fabricate the composite module. NGSS was selected in a competitive procurement within the Composites Consortium, under agreement between the ONR and the South Carolina Research Authority for Composite Manufacturing Technology. A single full-scale prototype module (40 ft x 24 ft x 8 ft) was fabricated to validate the materials and fabrication process selected for module manufacturing. Fabrication of the module was completed on schedule and below budget (8). The prototype passed all tests for load-carrying capacity, stability with cargo on the deck, and linking tests with the locking mechanism. See Figure 16 for a picture of the Joint Modular Lighterage System. CHSV In 2003 NGSS began work on an ONR project that studied the feasibility of an all- Composite High Speed Vessel (CHSV). This was an engineering study for a roughly 100-meter, 2000-metric ton, 40+-knot ship using lifting bodies. Lifting bodes are large streamlined underwater appendages that partially lift the ship out of the water and improve the vessel s seakeeping and top speed. The three principal participants in the program were NGSS, Navatek, and NSWC-CD (33). The majority of the project funds were dedicated to a composite material testing and manufacturing program, with smaller amounts for hydrodynamic design, computational fluid dynamics (CFD), hydrodynamic scale model testing, and ship design. A full scale, forward third of the hull length was manufactured in Gulfport. This allowed NGSS to demonstrate that the manufacturing technology had matured sufficiently to produce a composite ship of that size, with its complicated shape, in a shipyard environment. The demonstration article was approximately 85 ft long, 80 ft wide, and 35 ft tall. It contained approximately 60 long tons of composite structure (8). NSWC-CD composite subject matter experts were deeply involved in the project. Numerous material variations, resins, and processes were investigated, and sample coupons and test articles were manufactured and tested at NSWC-CD facilities. See Figure 17 for a picture of the CHSV forebody. FIGURE 16 JMLS prototype.

25 22 Composites Road to the Fleet A Collaborative Success Story CVN 77 Mast FIGURE 17 Picture of CHSV test article. The idea of a composite mast for aircraft carriers was discussed in navy circles as early as 2001, but it was not until roughly 2003 that serious discussions were held with NGSS R&D. There are two masts on the CVN 77 USS George H. W. Bush, and the forward mast was selected, the larger of the two. The navy was interested in using composites for the upper portion of this mast to save topside weight, and the composite mast was almost a form, fit, and function replacement for the baseline steel mast. This project was funded by the CVN Program Office, PMS 378. An optimized steel mast and a composite mast were designed and built in parallel. The composite mast, measuring roughly 33 ft tall, 61 ft wide at the upper platform, and 33 ft long, was installed on CVN 77 in It contains about 27 long tons of composites. This was the first time Newport News Shipbuilding, also owned by NGC, collaborated with NGSS on a composite project. Both sites are currently in discussions to develop a composite mast and island for future aircraft carriers (35). See Figure 18 for a picture of the mast segment. FIGURE 18 CVN 77 mast.

26 Hackett 23 CVN 70 Mast Platform This effort began in 2003 as a follow on to the CVN 77 mast project. A composite platform, 7 ft by 9 ft, was fabricated as a replacement component for the 241-ft level platform for CVN 70 USS Carl Vinson. The intent of the project was weight and maintenance reduction. The platform was installed during the CVN 70 refueling and refurbishment period in The platform was identical to one provided for the CVN 77 composite mast. This was a collaborative effort between Newport News and NGSS (8). AESD Deckhouse The Advanced Electric Ship Demonstrator (AESD) is a 133-ft-long DDG 1000 look-alike technology demonstrator craft, built to support the DDG 1000 technologies maturation and ship design development. The AESD is operated by the NSWC-CD at its Acoustic Research Detachment (ARD) base in Bayview, Idaho. NGSS R&D was approached by ONR in 2004 to build a composite deckhouse for the AESD steel hull, which was built by another contractor. The composite deckhouse offered a lightweight design but also provided the customer future design and testing flexibility. The composite deckhouse design requirements called for removable panels that could be changed out in order to study different topside technologies, including planar arrays, embedded antennas, low-signature superstructure mounted outfitting designs, etc. In 2005 the deckhouse was installed on the vessel at ARD (36, 37). This project is further evidence of the relationship with ONR and NSWC-CD on key applied science testing. See Figure 19 for a close-up picture of the AESD deckhouse and a picture of the completed vessel. Summary of NGSB-GC History Before the late 1980s NGSB-GC was a typical navy shipbuilder with expertise in metal design and fabrication, including ordinary steel, high-strength steels, stainless steel, aluminum, coppernickel, titanium, and other metallic materials. When the goal was established to gain an understanding and experience with marine composites, the company first turned to the subject matter experts at the navy lab. They then made contact with commercial composite fabricators and design consultants and eventually with universities specializing in composites. Over the last twenty-plus years, NGSB-GC has established an in-house design and fabrication capability in marine composites, including a dedicated fabrication facility. In early 2008, Northrop Grumman integrated its two shipyards (NGSS and Northrop Grumman Newport News) into one sector called Northrop Grumman Shipbuilding (NGSB). This integration has provided a synergistic approach to the design/manufacture of composites and their transition into the fleet. WINNING THE DD 21 CONTRACT The DD 21 is a large multipurpose destroyer class with a focus on land attack. Operating in the littorals, the ship is required to be a low-signature ship, including low RCS. As discussed previously, ITDS was instrumental in demonstrating that Litton Ship Systems had the experience and capability needed to provide all of the various technologies for a stealthy integrated topside

27 24 Composites Road to the Fleet A Collaborative Success Story FIGURE 19 AESD deckhouse. that can be built in the shipyard environment. ITDS was continuously briefed to the navy and particularly the DD 21 program office, PMS 500. PMS 500 was very impressed that a shipyard could fund, manage, and execute an R&D program like this, with all the vendors, technology, and testing that was involved. The timing of the completion was crucial. The project moved much faster than typical research projects, as it had to be completed in time to brief the DD 21 program office on the results of all the testing. It was a complete success, achieving all its goals (1). Later that same year, on November 24, 1999, Phase 2 of the DD 21 contract was awarded to the Gold Team, led by Litton Ship Systems (38). One of the key differences between the Gold Team s design and the Blue Team s design (led by Bath) was the composite deckhouse on the Gold Team s design. With this award the navy selected the Gold Team and their design to go forward for the preliminary design of DD 21 (now called DDG 1000). See Figure 20 for a picture of the DDG 1000 engineering development model (EDM) deckhouse unit being fabricated at the Gulfport Composites Center of Excellence. Figure 21 is an artist s concept of DDG The dark rectangles shown on the integrated deckhouse represent the flush planar arrays.

28 Hackett 25 FIGURE 20 DDG-1000 Deckhouse Engineering Development Model (EDM). FIGURE 21 DDG-1000 integrated deckhouse.