VLS Underway Replenishment: When will the Navy get serious?

by Craig Hooper Defense Tech Naval Warfare Analyst

In a high-threat environment, the Navy’s AEGIS vessels have a problem. They cannot be re-armed. AEGIS cruisers have 122 vertical launch system (VLS) cells, while the destroyers have 96. Each magazine is “multi-use,” composed of specialized land attack and self-defense weapons, so a desired missile may not be available in sufficient numbers. Complicating matters, AEGIS vessels sometimes sail with a partially-filled magazines, and missile reliability rates aren’t often anywhere near 100%.

CSBA expert Jan Van Tol, in his recent AirSea Battle monograph (.pdf), is the latest to highlight this vulnerability, and pointedly suggests that, given the way high-end warfare is likely to be waged, “the Navy should continue its efforts to develop and field the capability to rearm surface ship VLS cells at sea.”

But…what efforts? VLS underway replenishment (UNREP) has been a long-standing—and long-ignored-- vulnerability. Take this editorial snippet from a Fall 1988 issue of the long-unheralded UNREP Journal:

"In wartime the enemy decides when and where we expend defensive ammo, so an ammo UNREP may be needed any time, even when the seas are rough or the decks are icy. While we may be able to rearm our aircraft carriers under these conditions, our ability to handle missiles in dollies or in VLS canisters on cruisers, destroyers, and frigates is extremely poor.

The magnitude of the missile handling problem has been minimized over the past 25 years because of a lack of a missile war and the infrequent missile UNREPs to cruisers, destroyers and frigates. We do transfer stores in peacetime that have to be deck handled, but our peacetime UNREP policy is "safety first", so we can wait for seas to abate and the ice to melt. As a result, a serious ammo UNREP problem has not had much visibility.

The U.S. Navy had an answer in the 1960's to transferring and striking down missiles in heavy weather or even with icy decks. It was called FAST for Fast Automatic Shuttle Transfer. FAST demonstrated a transfer/strikedown rate of 24 TARTAR missiles per hour at night in sea state six conditions (compared to four VLS missiles per hour now in daytime and calm seas). While we can still transfer missiles between ships at a high rate, deck handling, and strikedown are the limiting factors. Deck handling was solved by FAST because missiles were automatically moved from the UNREP station to the magazine strikedown without sailors having to push-pull dollies or hand trucks. However, the complexities of the automated FAST handling equipment created an unacceptable maintenance burden on both the UNREP and combatant ships because FAST required the services of shipboard technicians that were either not available or were needed to maintain the ship's missile launchers. As a result, FAST wouldn't work when needed nor perform as planned. FAST had to be simplified in the 1970's to our current STREAM system.

What should be done today about rearming missiles? The right missile handling system must be superior to what we have today, but not nearly so complicated as FAST. The right system must be highly reliable so as to withstand long periods of disuse and still work when needed. The right system must be simple in design so that no extensive specialized training is required for the crew. The right system must be able to safely handle missiles in heavy weather and on icy decks....

...There are some who say that UNREP of missiles is too hard and, therefore, the requirement should be eliminated; however, the recent missile firing experience by U.S. ships in the Persian Gulf should alert us to the future....When the going gets tough a great amount of ammo will be expended in a short time. The next urgent requirement is to quickly reload those empty magazines and be ready for whatever follows. Underway replenishment is the only answer for the fleet commander and we need to do it better."

This passage was written almost a year BEFORE the USS Arleigh Burke (DDG 51) was even launched. So, it’s safe to say that AEGIS vessels have not been designed with missile UNREP in mind—and, yet, they’ve done just fine.

But today, given the anticipated growth in demand for VLS cells, is it time to start considering the need for rapid VLS UNREP? Is there a way to design VLS cells (and VLS-dependent ships) to facilitate fast underway replenishment of depleted missile batteries?

With the restart of the DDG-51 program, this is something the Navy community must discuss. Now that America has gone a couple generations without incorporating ease of missile UNREP in warship design, has the Navy simply overlooked the possibility of designing missile ships so they can quickly be replenished?

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