America’s ballistic missile submarines can stay submerged and hidden from prying eyes for up to three full months at a time. But what happens when one of these vessels needs to be resupplied while out at sea? As a recent video released by the U.S. Navy shows, there are a number of resupply options available to these clandestine war machines, ranging from small drones to massive cargo aircraft.

“We don’t need to send them fuel, but sometimes we do need to send them [food], sometimes we do need to get them some parts to keep them at sea,” Commander of Submarine Force Pacific Rear Adm. Blake Converse said this week at the Naval Submarine League’s annual symposium.

“Our submarines are very reliable and can carry quite a bit of food, but [the resupply] further extends the range of those submarines. And that was hugely mission-enhancing for the BN force.”

The United States maintains 14 nuclear-powered Ohio-class ballistic missile submarines to serve as the sea-based leg of America’s nuclear triad. These subs serve alongside the triad’s airborne leg (bombers like the B-52 and B-2) and the land-based leg comprised of intercontinental ballistic missiles. Both Russia and China employ nuclear triads of their own, using similar methodologies.

As a part of the nuclear triad, these submarines need to stay at sea for extended periods of time, ensuring America’s sea-based nuclear deterrent remains viable. However, since they can only store around 90-days worth of food on board at a time, the submarines sometimes need to be resupplied while out on the open sea. If a large scale conflict were to break out with a near-peer and nuclear-capable adversary like China, these submarines would serve as an essential bit of posturing, ensuring China doesn’t launch a nuclear strike against the United States through the nuclear doctrine of Mutually Assured Destruction (MAD).

The premise behind MAD is simple: America’s nuclear triad ensures that no nuclear attack could completely annihilate all three methods of nuclear weapon delivery available to the United States. That certainty means a nation planning a first-strike nuclear attack can rest assured that America will respond with its own nuclear weapons. MAD is effectively a promise between opposing nations that says:If we go, you go with us.” That’s why America’s ballistic missile submarines have adopted the not-so-funny nickname of “Boomers.”

An unarmed Trident II (D5LE) missile launches from the Ohio-class ballistic missile submarine USS Maine (SSBN 741) off the coast of San Diego, California, Feb. 12, 2020. (U.S. Navy photo by Mass Communication Specialist 2nd Class Thomas Gooley/Released)

In order to keep these submarines well-stocked while at sea, the U.S. Navy tested delivering supplies from four different airborne platforms. First, a U.S. Navy Sailor controlled a small quad-rotor drone that could deliver small items or pieces of equipment to a surfaced sub. Then, a U.S. Navy MH-60 Seahawk delivered a slightly larger payload, before a U.S. Marine Corps MV-22B Osprey came in with another. Finally, a U.S. Air Force C-17 Globemaster airdropped another delivery as it flew overhead.