Navy's AEM/S System Mast Leads the Fleet Into the 21st Century

The U.S. Navy's first-ever advanced hybrid composite structure, known as the Advanced Enclosed Mast/Sensor (AEM/S) System, has been installed aboard the Spruance Class multimission destroyer USS ARTHUR W. RADFORD (DD 968), at Norfolk Naval Shipyard, Portsmouth, Virginia. The ship will be the platform for extensive testing of the new mast by the Navy.

The new, advanced composite mast, which the Navy describes as "revolutionary and spectacular," was built and designed by an Integrated Product Team (IPT) -- known as "The AE MIS System Masters" -- made up of technical experts drawn from diverse Navy and industry activities nationwide.

The AEM/S System is a 93' high, hexagonal structure, 35' in diameter, enclosing existing radars and providing important signature and other operational benefits. By enclosing major antennas and other sensitive equipment, the AEM/S System protects them from the weather. This reduces maintenance, as well as providing significantly reduced radar signature.

A traditional "Mast Stepping" Ceremony was held on 17 May at Norfolk Naval Shipyard to commemorate mast installation and to honor the AEM/S System Masters who dedicated more than three years to the project.

"We in the Navy are committed to developing -- and introducing into the Fleet highly sophisticated technology with advanced war-fighting capabilities," said the Naval Surface Warfare Center program manager Jeffrey L. Benson. "We revere tradition, but we do not live in the past. So we will 'step the mast' to honor our traditions and to celebrate our technological advances. As we replace the RADFORD's conventional mast with the AEM/S System mast, I cannot think of a more fitting way to commemorate this historic event."

Keynote speaker at the ceremony, Admiral Paul G. Gaffney II, Chief of Naval Research, called the design revolutionary and spectacular. "The new mast will give us much improved sensor performance," he said. "The work by the Navy-industry team on this mast is absolutely spectacular."

The AEM/S System mast was installed aboard the RADFORD to replace her conventional main (aft) mast. The RADFORD, currently undergoing regular overhaul, will return to normal fleet service in Fiscal Year ‘98 with a fully operational AEM/S System. The AEM/S System will remain aboard the RADFORD for at least a year of tests and at-sea trials.

The AEM/S System ATD has developed a revolutionary mast that is affordable, solves problems associated with current masts, enables new technology required for the Navy's next generation of stealthy ships, reduces life-cycle costs, enhances sustainability, and most importantly, enhances war-fighting capabilities. Successful completion of this ATD is a key element in the incorporation of advanced technology into the topside design for the next generation of surface combatants.

Participating in the development, design, and construction of the AEM/S System were representatives of the Office of Naval Research, Naval Sea Systems Command, Naval Research Laboratory, Carderock and Dahlgren Divisions of the Naval Surface Warfare Center, Naval Command and Control and Ocean Surveillance Center, and Norfolk Naval Shipyard. Industry participants were Ingalls Shipbuilding, Seemann Composites, Mission Research Corporation, Material Sciences Corporation, Ohio State University, and Analysis & Technology.

As the AEM/S System was stepped aboard the RADFORD, Mr. Benson introduced each individual Master, who placed a coin under the mast. Twenty-one steel pennies (minted in 1943) were placed. Steel pennies were selected because copper is traditionally considered to bring bad luck. The steel pennies (21 Cents) symbolize the "Twenty-first Century" technology embodied in this Advanced Technology Demonstration. In keeping with tradition, the RADFORD's newest and oldest "Old Salts," GSEFN J.D. Mohead and EWCM(SW) R.B. Esteppe, placed the last CENT.

In his concluding remarks accepting the mast, the RADFORD's Commanding Officer Kurt Tidd said, "I think it's the most beautiful thing I've ever seen." Commander Tidd promised that his crew would vigorously test the new mast in full cooperation with the AEM/S System Masters - his new RADFORD shipmates.

Ingalls Shipbuilding division of Litton Industries, the ATD's prime industrial support activity, was responsible for fabrication of the AEM/S System Mast and a myriad of associated test articles. To support this effort, Ingalls established a composites complex and developed a temporary, liftable building in which to fabricate the mast and the test articles. In addition to fabrication, Ingalls developed detailed plans for installation aboard the RADFORD.

The AEM/S System is a high-risk, high-payoff Advanced Technology Demonstration. Benefits and payoffs include:

Enhanced Performance: The AEM/S System is fabricated with an advanced composite hybrid frequency selective surface (FSS), designed to allow passage of own-ship sensor frequencies while reflecting other frequencies. Improved sensor performance results from reduction of blockage, false targets and sensor downtime, thereby dramatically enhancing the ship's war-fighting capability.

Affordable Low-Cost Manufacturing: The AEM/S System utilizes unique materials, creative structures and innovative manufacturing techniques, yet the mast can be produced in a shipyard environment.

Affordable Reduced Life-Cycle Costs: The AEM/S System's enclosed structure protects radars and communication antennas from weather exposure and provides all-weather access for repair, thus greatly reducing the need for repair, maintenance costs, replacement costs and risk of failure.

Enhanced sustainability: The AEM/S System concept will enable rapid and seamless transition to the next generation of technology. Features such as embedded sensors, planar arrays, integrated antennas, low observable signatures, reduced topside weight -- all contribute to the Navy's objectives for future warships. Accelerated transition of AEM/S System technology to the LPD 17 is already underway, along with evaluation of its applicability to the SC 21 and CV(X).

The upper half of the AEM/S System is designed to allow passage of own-ship sensor frequencies with very low loss while reflecting other frequencies. It is divided into two radome-like compartments; the upper compartment houses the MK 23 TAS antenna, and the lower encloses the SPSAO air search radar antenna.

The whole system is a free-standing, fully integrated composite structure. Structural design requirements for strength and stiffness meet Fleet requirements for vibration, shock and fatigue. Signature and electromagnetic design requirements are based on criteria associated with sensor and antenna performance, electromagnetic interference, lighting protection electromagnetic shielding, electrical bonding and grounding. The objective of this team effort was to develop an affordable mast by fully integrating sensor technology, electromagnetics, signature reduction, advanced materials structures and manufacturing technologies," said Benson. "The AEM/S System will result in significant new design options for both future surface ships and major upgrades. This program is a necessary step in the development and deployment of next generation radar and communication systems."