Rearming at Sea: Yesterday’s Necessity
Mounting crises across the Middle East, Russia’s ongoing war in Ukraine, and the growing challenge of credibly deterring the People’s Republic of China (PRC) in the Indo-Pacific all increasingly strain the United States’ rapidly depleting munitions stockpiles. The United States should invest in expanding its munitions stockpiles and strengthening its defense-industrial capacity. Nevertheless, these efforts are insufficient on their own to ease the United States’ extensive logistical constraints in prosecuting a large-scale conflict and will take years to bear fruit.
The United States’ best option to mitigate these logistical weaknesses is to reduce bottlenecks that hamper its deployable existing combat power. Addressing these vulnerabilities is critical for U.S. naval forces, as the sea would form a principal battleground in any high-intensity conflict with America’s most capable potential adversary, the PRC. One of the most glaring and least discussed of these logistical gaps is the U.S. Navy’s inability to reload its principal missile magazine, the vertical launch system, at sea. The length of time U.S. surface combatants must divert from their area of operations to rearm directly impacts the combat power available to commanders. To increase the availability—and therefore lethality—of its fleet as the PRC’s maritime capabilities rapidly expand, the U.S. Navy urgently needs to pick up the pace on developing at-sea missile reloading capabilities.
Emptying Magazines
For an illustrative example of the United States munitions challenge, scholars and policymakers need to look no further than the ongoing military operations in Yemen. The Red Sea strike campaign—intended to counter and retaliate against Houthi attacks on Red Sea shipping—underscores serious munitions constraints for the Navy. During large-scale American and British strikes against Houthi positions on January 12th, 2024, the Navy launched over 80 Tomahawk cruise missiles against dozens of targets across Yemen, far exceeding 2023’s entire Tomahawk acquisition of 55 missiles. Given mounting assessments that this strike campaign is unlikely to deter the Houthis, policymakers can expect naval magazine replenishment demands to persist and even worsen.
The Red Sea operations bear troubling implications for high-priority theaters such as the Indo-Pacific. In a high-intensity conflict against a near-peer competitor such as the PRC, U.S. surface combatants would expend substantial quantities of munitions designed to counter or strike land, air, surface, undersea, and ballistic missile threats. Even against the comparatively less capable Houthis, the U.S. Navy faced 28 drones during a single early morning attack on March 9th, in addition to at least 95 drones and missiles it had previously intercepted from Yemen up to that point.
Rearmament needs would exponentially compound against a high-end adversary like the PRC. Indeed, wargames conducted last year by the Center for Strategic and International Studies estimated that in a conflict over Taiwan, the United States could run out of several categories of vital munitions, such as Long-Range Anti-Ship Missiles, in less than a week. A similarly stark Center for Strategic and Budgetary Assessments (CSBA) study estimated that in a conflict with the PRC, the U.S. Navy could expend over 360 missiles a day, or 10,800 per month.
But even if the United States has the munitions stockpiles it needs to credibly threaten or sustain this kind of high-intensity combat in the near future, it could still fall prey to a less-discussed but equally dangerous bottleneck: naval rearmament time. Central to this challenge is the role of the Navy’s workhorse missile magazine: the Vertical Launch System.
The Vertical Launch System
Since naval combat became organized around guided missiles in the second half of the 20th century, the number of these munitions that U.S. ships can bring to bear against their adversaries has become a central metric of fleet combat power.
In 1986, the Mk-41 Vertical Launch System (VLS) became the U.S. Navy’s principal missile magazine for surface combatants. VLS modules comprise a series of reloadable cells able to house various missiles for missions as diverse as offensive strikes on land targets or defending against incoming anti-ship missiles in readiness for immediate firing. The Navy’s primary surface combatants, Arleigh Burke-class guided missile destroyers and Ticonderoga-class guided missile cruisers, have the VLS capacity for up to 96 and 122 missile cells, respectively.
Despite their reliability and usefulness, VLS tubes must be reloaded in port. Early efforts to install foldable cranes on U.S. surface vessels were abandoned, given the challenges of loading heavy canisters of live munitions in rough seas. Nevertheless, returning to a friendly port capable of VLS reload can take weeks, depending on how far a ship is deployed from the nearest facility with the proper infrastructure.
VLS Rearmament as a Point of Failure
These long rearmament times could be a strategically catastrophic bottleneck. In a high-intensity conflict with the PRC, U.S. surface combatants should expect to defend against large-scale anti-ship missile salvos that could force them to deplete their VLS magazines rapidly. Even if U.S. forces possess adequate stockpiles to rearm after these engagements (certainly not guaranteed in light of the aforementioned magazine depth concerns), ships diverting for weeks to reload their VLS cells could be unavailable during critical phases of the conflict. Should China or another adversary successfully target friendly ports capable of rearmament, such as those in Japan or Guam, surface combatants could be forced to divert thousands of miles out of theater to refill their magazines. In other words, even if the Navy has the supplies and assets necessary to win, it can still lose if it cannot access and employ them quickly enough.
Therefore, munitions logistics could be decisive for deployable fleet strength. Against the PRC’s increasingly superior mass at sea, faster VLS reloading presents an opportunity to blunt Beijing’s numerical advantage by maximizing U.S. naval lethality. CSBA estimated that by reducing diversionary reload times, at-sea VLS rearmament could add the effective on-station missile capacity of up to 18 additional cruisers and destroyers.
At-sea VLS reloading is a difficult engineering problem, but having the capability to rearm far closer to the mission at hand is too important an asset to give up on. The United States’ defense-industrial challenges will not be solved overnight. Hitting the proverbial gas pedal on missile reloads at sea can mitigate U.S. vulnerabilities and improve the credibility of its deterrent efforts in the meantime.
Building on the U.S. Navy’s Efforts
The Navy recognizes the risks of its reloading deficiencies and has intermittently tested at-sea VLS reloading concepts since 2016. One promising design, the Transferrable Re-arming Mechanism, could be fitted to existing Combat Logistics Force (CLF) vessels and would employ existing systems used for the Navy’s underway replenishment. Another, the At-Sea Precision Lift concept, features a crane that compensates for ships’ swaying and roll and could employ the Navy’s Expeditionary Sea Bases derived from existing commercial oil tanker designs.
Unfortunately, most tests so far have occurred pier-side rather than attempting to test their viability in the higher sea-states where the designs are theoretically capable of operating. Since last year, Secretary of the Navy Carlos Del Toro has described at-sea rearmament as a “main priority” for the service and a “game-changing” capability to achieve. In February, speaking at the annual WEST Conference in San Diego, Del Toro announced orders for an at-sea test by this summer. But the Navy needs to go further, both in testing and logistical procurement.
One or two yearly tests may signal continued interest but will not make at-sea rearmament deployable in the 2020s. If underway VLS reloading is a top priority, the Navy should conduct multiple experiments annually with various crane designs and then incorporate the most promising and adaptable type into training exercises for further refinement as soon as proof of concept is achieved in moderate seas. At-sea VLS reloading should then be incorporated into large-scale international exercises, such as the Rim of the Pacific exercise (RIMPAC), sending a message to partners and adversaries alike about the United States’ ability to retain maximum lethality in a conflict.
If such a testing tempo is not possible within its existing resources, the Navy should seek the additional experimentation funding it needs in its FY 2025 budget request. The return on investment could be substantial—CSBA’s 2019 projection estimated that at-sea VLS rearmament would provide approximately $11-37 billion of “value” in terms of the equivalent combat power that would be made available. Put in perspective, the Navy’s entire 2024 shipbuilding budget was $33 billion. This potential is waiting to be unlocked.
Given the existing demands of its overstretched sealift fleet, the Navy should also increase the number of support vessels capable of conducting VLS reloading at sea. Capable adversaries will recognize the strategic value of the ships conducting this rearmament mission and target them. Equipping a wider variety of support vessels to conduct rearmament missions in addition to their other sustainment tasks would reduce their individual value as targets and improve U.S. logistical resiliency.
In the long term, once a reliable, adaptable at-sea VLS re-load crane is developed, the Navy should procure additional support vessels that can specialize in rearmament. Existing commercial vessels are already designed for transferring cargo at sea and could be well-suited for this role. Feeder ships, for example, transport cargo between larger container ships and ports inaccessible to those vessels. Buying and converting commercial vessels such as feeder ships would be faster and more economical than designing purpose-built hulls from scratch. Commercial conversions would also be more replaceable, reducing pressure on support vessels with other tasks. Rearmament ships fitted with multiple cranes could further reduce rearmament time by simultaneously reloading surface combatants’ fore and aft magazines.
The Capability the U.S. Navy Needs
Magazine depth may receive most of the policy attention and for good reason. But given the logistical bottleneck posed by VLS reloading, even full stockpiles could be rendered useless in a high-intensity fight against massed enemy formations and daunting missile salvos. The Navy needs to significantly improve its rearmament time to maximize its munitions, both now and in the future.
The challenges of blue water missile rearmament are very real, but so are the dangers of increasingly strained deterrence. The U.S. Navy has conducted underway replenishment since at least 1799 and more systematically since first experimenting with refueling coal at sea in 1899. The Navy already knows how to bring food, fuel, and certain ammunition to the fleet directly to keep it in the fight longer. At-sea vertical launch cell reloading in the missile age should be just as integral to fleet sustainment.
Given nearly a decade of testing, at-sea VLS rearmament should have already been well on its way to maturity. However, if the best time to implement this technology were yesterday, the second-best time would be today.
Views expressed are the author’s own and do not represent the views of GSSR, Georgetown University, or any other entity. Image Credit: U.S. Department of Defense via Flickr