You could almost say the Aegis combat system (ACS) bears a close resemblance to the Portuguese Man O’ War, which drifts on the surface of warm-water oceans where it ignites fear for its potent sting. What stands the ACS apart, however, is its ability to be equally effective in all climates and any conditions, with a sting intended to have a much wider effect.

The ACS is an integrated weapons system used by the US, Japanese, Spanish, Norwegian and Korean navies. And more countries, including Greece and India have shown interest in its capabilities while Australia has already placed orders for placement on its new destroyers. It is one of the most advanced and most capable defence systems currently in use featuring both an integrated single-ship system and a ship-to-ship network. In all, 108 ships – 88 within the US Navy – feature Aegis.

“The ACS is an integrated weapons system used by the US, Japanese, Spanish, Norwegian and Korean navies.”

First developed by the missile and surface radar division of RCA, Aegis is currently produced by Lockheed Martin, which gained the technology through acquisition and has been developing it ever since. As the first ever completely integrated combat system designed to repel any menace from the surface, air and subsurface, the weapons control system can claim to be the most sophisticated naval surface ship combat system around today.

It is also an advanced command and decision (C&D) and comes equipped with the very latest in radar and computer technology, which allows it to follow enemy targets and, where necessary, destroy them.

Aegis also has a number of equally important components at its core. The weapons system includes within its armoury the mk41 vertical launching system, the Phalanx close-in weapon system (a fast-reaction, rapid-fire 20mm gun system), anti-submarine warfare (ASuW) systems and Tomahawk land attack cruise missiles (TLAM). It also boasts integrated shipboard torpedo and naval gunnery systems. The Aegis weapons system itself, which is at Aegis’s heart, comprises the mk99 fire control system, weapon control system, the command and decision suite, the SPY-1 radar and SM-2 Standard missile systems.

Lockheed Martin spokesman Ken Ross says the main attraction of the Aegis weapon system has been the Aegis ballistic missile defence – a primary component of the sea-based element of the US ballistic missile defence. “All elements are fully integrated to provide the fastest and most reliable data sharing and operational awareness,” says Ross.

Aegis history

Aegis’s biography dates back to the late 1950s when having replaced guns with guided missiles the US Navy introduced the advanced surface missile system to coordinate defence of its ships from anti-ship missile threats. In 1969 it was renamed Aegis, after the mythical Greek god Zeus’s fabulous protective shield of the same name. After a series of developments the US Navy built the first Aegis-equipped cruisers using the hull and machinery designs of Spruance Class destroyers.

At the very centre of the ACS is the SPY-1 radar system. SPY-1A – an advanced, automatic detect-and-track, multi-function three-dimensional passive electronically scanned array radar known as ‘the shield of the fleet’. The SPY high-powered radar is able to perform search, tracking, and missile guidance functions simultaneously with a track capacity of well over 100 targets at more than 100nm (190km).

The SPY-1 radar guides the Standard missile delivery through a radio frequency uplink during its midcourse during engagements but the terminal guidance is supplied by the SPG-62 radar system. This combined radar guidance enables considerable numbers of targets to be engaged simultaneously. It first went to sea in 1983 with the USS Ticonderoga which belongs to the Spruance Class.

“The ACS is one of the most advanced and most capable defence systems currently in use.”

“Since then, upgrades in antenna and signal processing capability have been core elements of the Aegis evolution,” says Ross.

“Developments that added greater cruise missile detection and electronic countermeasures led to the SPY-1B and SPY-1D, and signal processing advances to increase effectiveness in the harsh littoral regions were introduced with SPY-1D(V). As this radar has made monumental increases in capability, the SPY-1A still provides superior performance when compared to other radar at sea around the world.”

ACS investigation

On 3 July 1988, the ACS was tested in practice when missiles launched from USS Vincennes shot down Iran Air Flight 655 over the Straits of Hormuz near the end of the Iran-Iraq war killing all 290 passengers and crew aboard. Despite the tragic loss of life the official report, ‘formal investigation into the circumstances surrounding the downing of Iran Air flight 655 on 3 July 1988’, written by Rear Admiral William M Fogarty, concluded that the ACS had no maintenance problems and was fully operational. It was determined that human error had led to distrust on the part of the crew of the data provided by the ACS and the civilian plane was wrongly identified as an Iranian F-14 Tomcat attempting an attack on the USS Vincennes.

The investigation ruled that had the commanding officer relied on the tactical data provided by Aegis, the engagement would not have happened. The tense conditions of the region had led the crew to misinterpret the data subconsciously.

Similar errors are highly unlikely in the future due to the continued development of the ACS. In 1991 the USS Arleigh Burke was commissioned with an architecture that was dominated by the Aegis system. Flight II of the Arleigh Burke class, which came on line in 1992, added further improvements to the Standard missile system and SPY radar.

Aegis modernisation programme

Today, the US Navy is in the process of modernising Aegis-equipped ships. “USS Bunker Hill, which went to sea in 1986, is undergoing modernisation in San Diego,” Ross says. “When it leaves the shipyard in February it will have the most advanced Aegis weapon system, and will be the first ship with Aegis open architecture. This cruiser modernisation programme is the first phase of modernisation for the 84+ fleet of US Navy Aegis ships.”

In 2012, the Navy will begin installing the next phase, Aegis modernisation, with the USS Arleigh Burke (the first-of class in the DDG-51 line). “This phase will include the full merge of Aegis open architecture with Aegis BMD, allowing the navy the potential to have its full fleet of Aegis ships be BMD capable,” Ross says.

“The SPY high-powered radar is able to perform search, tracking, and missile guidance functions simultaneously.”

The most spectacular use of the ACS came on 14 February 2008 when an SM-3 missile launched from USS Lake Erie destroyed the USA 193 satellite which was in a deteriorating orbit and in danger of falling into the Earth. An event which might well have had calamitous consequences as USA 193 was carrying hydrazine – an extremely hazardous substance that could have led to a major toxic cloud being released into the atmosphere.

Launched on 14 December 2006, it was decided within the month that the satellite had to be destroyed, and by the first week of January Aegis was considered to be the only option.

This defence of Earth from a felt threat from outer space, albeit one homemade and not alien in origin, was developed in less than 45 days, according to Ross. The Lockheed Martin engineers “tested it, installed it on the three ships and created the training for those three crews.”

“The design of Aegis as a closed-loop system was critical to the mission’s success – after the SM-3 was launched from USS Lake Erie, Aegis tracked the satellite and provided mid-flight guidance to the missile (until just before the intercept),” Ross says. In short, in under two months the Aegis system was adapted for use in an environment for which it had not been designed and proved to be a complete success.