The Controversial Use of Aluminum in Naval Shipbuilding
The debate surrounding the use of aluminum in naval vessels is a fascinating saga of innovation, tragedy, and the perpetual quest for a fine balance between tradition and technological advancement. The evolution of naval warfare has always been in lockstep with technological progress. From the age of sail to the age of steel, the materials that make up warships are as critical as the sailors who man them. The United States Navy’s dalliance with aluminum superstructures is a chapter that warrants a deep dive, not only for its engineering implications but also for what it teaches us about risk, resilience, and the harsh calculus of naval strategy.
Initially, the shift toward aluminum was propelled by the burgeoning weight of electronic equipment onboard. The advent of radar and sonar, seismic leaps in maritime warfare technology, required ships to be floating platforms of sophisticated, heavy electronic systems. Aluminum, being lighter than steel, seemed the optimal solution for keeping these increasingly top-heavy ships stable and agile. Furthermore, its non-magnetic properties diminished the risk of triggering magnetic mines, a not insignificant detail in an era where naval mine warfare was evolving rapidly. Aluminum also offered substantial advantages in reducing structural weight and hull maintenance, as well as increasing the speed, payload, and range of the ships. However, aluminum also came with its own challenges, such as lower fire resistance, higher initial costs, and compatibility issues with steel.
Yet, for all its advantages, aluminum came with its own Pandora’s box. The infernos on the USS Belknap and HMS Amazon laid bare a glaring Achilles’ heel: aluminum’s lower melting point and fire resistance. In the unforgiving theater of war where fire is a constant, the vulnerability of aluminum contradicted the very essence of a warship’s need for survival under duress. Moreover, the difficulties in marrying aluminum superstructures with steel hulls introduced a host of structural integrity issues. Cracking and galvanic corrosion became the ghost in the machine, undermining the longevity and safety of the vessels. These issues were also evident in other incidents, such as the collision of the USS John S. McCain and the fire on the HMS Sheffield, both of which involved ships with aluminum components.
The US Navy’s oscillation in policy, from the all-steel Arleigh Burke destroyers of 1987 to the reembracing of aluminum in the Littoral Combat Ships of the 2000s, reflects a complex evaluation of priorities. The transition back to aluminum underscored an evolving philosophy in naval design — that the survivability of a ship in modern warfare might rely more heavily on evasion and counter-detection, facilitated by a lighter vessel, than on the ability to absorb and survive direct hits. However, this perspective has been challenged by the high operating costs and maintenance issues of the LCS, which are nearly as expensive as the much more capable DDGs. Moreover, the LCS has been criticized for its lack of firepower, especially in anti-surface and anti-air warfare, and its dependence on modular mission packages that are not yet fully developed or tested. The Navy has since decided to reduce the number of LCS and upgrade some of them to a new frigate design, which will have improved sensors, weapons, and survivability features. The Navy is also exploring the use of composite materials, such as carbon fiber, for its future warships, which could offer better performance and durability than aluminum or steel.
This perspective was a nod to the reality of contemporary missile technology; with the destructive power of modern arsenals, the best defense might be not to be hit at all. And yet, shock trials tell their own sobering story of aluminum’s vulnerabilities, whispering of critical deficiencies even as they praise aluminum’s resilience to impact. Shock trials are tests that subject naval vessels to simulated underwater explosions to evaluate their structural integrity and combat readiness. Aluminum ships have shown mixed results in these trials, with some performing well and others suffering significant damage. For example, the USS Independence, an aluminum-hulled littoral combat ship, passed its shock trials in 2016 with minimal repairs needed. However, the USS Coronado, another aluminum-hulled littoral combat ship, failed its shock trials in 2017 and required extensive repairs. These examples illustrate the challenges and trade-offs of using aluminum in naval shipbuilding.
Looking east, the Russian Navy’s flirtation with carbon fiber composite materials in its Admiral Gorshkov class frigate heralds a new potential revolution in naval material science. Composites promise the allure of surpassing steel in key physical properties, such as strength, stiffness, and weight reduction, even as they wrestle with their own demons of cost and fire resistance. According to a recent article, the Russian Navy claims that the use of composites in the frigate’s superstructure reduces its radar signature by 50% and increases its speed by 10%. The article also reports that the composites are made of carbon fibers and epoxy resin, and are produced by a domestic company called Prepreg-SCM. However, the article also raises some doubts about the reliability and durability of the composites, especially in harsh marine environments. The article cites a former Russian Navy officer who says that the composites are prone to cracking and delamination, and that they have not been tested for long-term exposure to saltwater, humidity, and temperature changes. The article also mentions that the fire resistance of the composites is questionable, as they can burn and emit toxic fumes when exposed to high temperatures. Therefore, the use of composites in naval shipbuilding is still a controversial and challenging issue, requiring further research and development.
In considering these material quandaries, we must grapple with the fundamental truths of naval warfare: Ships are both weapons and targets, symbols of national power, and platforms for the projection of force. The materials from which they are wrought must be chosen not just for how they enable a ship to fight but also for how they contribute to the ship’s survivability. After all, a warship’s prime asset is its presence, and a presence cut short by structural failure serves neither deterrent nor combat purposes. Therefore, naval ship designers must balance the trade-offs between performance, cost, and survivability, and evaluate the risks and benefits of different material options. According to TNO, a Dutch research organization, survivability can be increased by designing structural elements to minimize load transmission, installing equipment on shock mounts, and protecting key areas with blast- and fragment-resistant doors and bulkheads. Moreover, survivability assessment tools, such as Alion’s MOTISS, can help simulate the susceptibility, vulnerability, and recoverability of naval ships under realistic threat scenarios. These tools can also support the development and testing of novel materials, such as carbon fiber composites, that promise to surpass steel in some physical properties.
