This is the fifth commentary in a multipart series exploring ways to strengthen the U.S. Navy’s fleet. The first part is here, the second here, the third here and the fourth here.

There is no more valued attribute, as famed naval tactician Wayne Hughes declared, than “the number of ships ... a fleet can have.” But ships must be sustained — something the naval officer Alfred Thayer Mahan recognized nearly a century earlier when he wrote: “Fuel stands first in importance of the resources necessary to a fleet.”

The U.S. Navy spent nearly $3.9 billion on operational fuel in fiscal 2022 alone, roughly the cost of two Arleigh Burke-class destroyers. In terms of scale, the Department of Defense is the world’s largest institutional user of energy, consuming more than corporations like Amazon or developed nations like Sweden and Portugal.

Energy — specifically fuel — thus becomes a central planning consideration for any globally present maritime strategy. In the words of Secretary of the Navy Carlos Del Toro, refueling options are essential “to keep our ships out of ports and in the fight.” And as Mahan noted: “The distribution and storage of fuel is, therefore, eminently a strategic question.”

A return to nuclear power could address many of these surface combatant endurance challenges. But such an approach is costly and unlikely.

Instead, four programmatic and policy choices can build energy resilience and maximize efficiencies in the fleet, which can yield innumerable benefits as the Navy designs, employs and sustains its force deep into this century.

1. Expand in-theater, at-sea refueling options to increase capacity and accelerate mobilization timelines. Beyond the Navy secretary, senior uniformed leaders at U.S. Transportation Command and in the Pacific have highlighted the need to expand capacity. Military Sealift Command currently operates 32 refueling ships — only a third of the requirement and a number that will remain stubbornly low, even as new oilers replace their aging predecessors. The Maritime Administration’s Tanker Security Program and Voluntary Tanker Agreement provide additional surge capacity in the event of a conflict or national emergency, but these reinforcements can seem like a drop in the proverbial ocean.

Partnering with industry can augment logistics force shortfalls. Military Sealift Command charters some niche support vessels, but identifying and contracting commercial, replenishment-capable ships that are underway could shorten supply lines. A government-developed containerized kit, which allows commercial tankers to pump fuel to Navy oilers in a process known as consolidated cargo replenishment at sea, is a disruptive capability that can rapidly expand at-sea refueling capacity and deserves investment.

Such approaches would require new — but solvable — procedures to vet crews and ships, communicate securely, and integrate these commercial units into existing military logistics constructs.

Additionally, public law mandates all military cargo to be carried aboard U.S.-flagged vessels. Congress should revisit this statutory requirement and authorize the use of tankers registered to treaty allies so we can leverage our trusted partners’ capacity and overcome domestic constraints.

2. Establish a single-fuel standard for ships and aircraft to increase operational flexibility. Combatants carry two different fuels on board in separate fuel systems because while shipboard gas turbine engines are capable of burning multiple types of fuel, their embarked helicopters only use a single high-grade variant called JP5 in the maritime environment.

Complicating matters, the managers who oversee surface and aviation fuel standards, purchasing, and distribution reside in different Navy systems commands and do not always reach consensus when evaluating engineering, supply chain and operational risk.

Economically, the U.S. Navy is one of the few consumers of JP5, which sends a weak demand signal to industry. A single naval fuel — whether JP5 or a different alternative entirely — would increase demand for specialized mixtures and lower artificially high prices through economies of scale. It would also align with the recently released National Defense Industrial Strategy’s priority of resilient supply chains by simplifying purchasing, transportation and distribution logistics.

Technologically, a single-fuel standard for ships would also result in a finer-grade fuel, which could enhance system performance, allow engineers to revisit underway maintenance periodicity assumptions and identify manpower efficiencies.

Thankfully, engineering problems beget solutions — and few fuels are unburnable. Additives can alter fuel properties to make it suitable for shipboard use without damaging tanks or systems. And improved purification methods, gasket materials and engine modifications can safeguard equipment during storage and operation. New mixtures are also becoming more ubiquitous — many with favorable properties — and they should be tested for shipboard use.

In short, we can transform vulnerabilities into strengths while preparing for a transition to biofuels and alternatives, which the International Maritime Organization and experts agree are the energy future — albeit one that will require time and platform design changes.

3. Retrofit energy-efficient systems aboard combatants to maximize operational endurance. To date, many programmatic efforts to field energy-efficient, shipboard systems have been focused on new production and forward fitting. But with a current force of 73 guided-missile destroyers, applying selected hull, mechanical and electrical improvements to today’s force can yield tens of millions of dollars in annual savings that can be redirected toward other priorities.

Apart from upgrades to shipboard generators and electrical distribution systems, additional gains can be realized by replacing large current-drawing appliances like heating, ventilation and air conditioning units — or even the dish-washing scullery. For example, the cruise industry found that a 30% enhancement in air conditioning efficiency leads to 5% annual fuel savings — a staggering $193 million if applied to the Navy. Similarly, the Air Force calculated that a 1% energy efficiency improvement fuels 8,000 additional sorties.

And seemingly insignificant actions can make a sizable and compounding impact: When United Airlines moved to a lighter-weight paper for its inflight magazine, a 1 ounce difference amounted to 170,000 gallons and $290,000 dollars in annual savings.

4. Improve data capture and analysis to guide operations more efficiently. The surface force still relies on manual processes to collect and submit fuel data, interpret predictive graphical curves, and estimate fuel percentages. But reporting methods, proficiency and even units of measurement can vary.

A better option would be to digitize these analog-intensive processes, apply machine-learning algorithms and mirror the Air Force’s Operational Energy Data Collection Strategy that has saved the service $31 million per year. Meanwhile, the Defense Logistics Agency should continue investigating options to securely automate fuel sensing and collection to standardize application across the Department of Defense.

Additionally, while stakeholders across the enterprise incorporate energy data into policies and plans, coordination can be streamlined. For instance, operations researchers at the Naval Postgraduate School have occasionally delved into these issues, and the Navy sends a few supply officers each year to the University of Kansas business school’s petroleum management program. However, no formal link exists between academia and organizations like the Office of Naval Research. Much like the Naval War College’s advanced research programs, such connections could help guide research questions, create unity of effort and align intellectual capital with operational requirements.

In times of strained capacity, and given American supply chains that span the Earth’s surface, new sustainment approaches can extend the surface force’s operational staying power.

As Mahan noted: “Without ammunition, a ship may run away, hoping to fight another day, but without fuel she can neither run, nor reach her station, nor remain on it, if remote, nor fight.”

Cmdr. Douglas Robb commanded the U.S. Navy’s guided-missile destroyer Spruance and is currently a U.S. Navy fellow at the University of Oxford, where Ensign James Potticary earned a Master of Science degree in energy systems and wrote a dissertation exploring the feasibility of alternative fuel sources for U.S. Navy ships. The opinions expressed in this commentary are those of the authors and do not reflect the views of the U.S. Defense Department, the Department of the Navy nor the U.S. government.

This is the fifth commentary in a multipart series exploring ways to strengthen the U.S. Navy’s fleet. The first part is here, the second here, the third here and the fourth here.

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