Why is rearming missiles at sea crucial for US Navy? And why is it so hard?

Today, having vertical launch systems on ships is basically a standard. VLS wells are full of missiles all ready to be launched. They enable the ship to both store many missiles and, more importantly, to fire them off in quick succession. And to mix and match missile types quickly, if needed. When US ships started receiving VLS systems in mid to late 1980s, there was some concern as to how to replenish spent missiles at sea. So a strike down module was incorporated into the missile well right from the start. Basically, it was a collapsible crane that took up three missile cells. And was supposed to take out an empty missile canister and slide in a replacement canister. But it ended up very finicky and hard to use. That was even for standard two missile canisters. Later, longer canisters like those for tomahawks were outside the scope of capability for the basically no extra missile canisters were ever stored on US navy ships. Cold war ended soon and the need to replenish at sea disappeared. There was no perceived enemy for decades. Then, in the last decade or so, China came along. The US is now in a rush to come with a system that will enable at sea replenishment. That old strike down crane is not in use anymore and, besides, today's missiles are larger and heavier than what it could handle. But let's back up a little. Why is the need to replenish missiles at sea so important? Here's the problem the US navy is currently facing. It envisions it may have to fight China. Said war would likely result in US ships firing off their missiles roughly in front of Japan's main islands, alongside the Ryukyu islands, near Taiwan and on the edges of the South China Sea. Some of those missiles would be tomahawks. Those are not such an issue. Bigger issue is that most would be SAM missiles. Not so much hitting Chinese planes, but intercepting Chinese missiles. Which would be aiming at both US ships and US land bases. There may easily be dozens of such missiles incoming per attack. Perhaps you remember that one video from Ukraine where a single patriot battery launched some 20 interceptor missiles within less than a minute against incoming Russian missile barrage. Against China, which has more launcher platforms and more missiles, who knows how many interceptor missiles might be needed to defeat a single attack. By far the most common US ship is the Birk class destroyer, with 96 VLS cells. There is no one standard missile loadout. It depends on perceived needs. Short range self defense SAMs are the ESSM missiles. Those come quad packed, so there are many of those per ship. They don't have the energy to pursue targets far from the ship, though. At best, they could engage some subsonic anti-ship missiles threatening a friendly ship a dozen miles away. Or perhaps a supersonic missile threatening a ship several miles away. Or missiles threatening their own ship. But it's the anti-ballistic missiles and long range SAMs that are problematic. Those would likely get used a lot. A destroyer might be a few dozen miles away and still be able to protect a location. But the missile expenditure rate might be huge. More than one interceptor may often be used against one incoming missile, to increase chances of successful interception. So let's now imagine that China performs a medium sized attack near Okinawa or against some carrier battle group. And the US ships in vicinity expand 50 missiles to defend. But then just hours later or the next day, another attack happens. Another 50 missiles get expanded. And suddenly even a group of 2 or 3 BRG destroyers is getting low on missiles. 3 destroyers, mind you, represent 3.3% of all US ships capable of area air defense. But in practice, they represent more. Out of 90 US air defense ships, a third is going to be under maintenance. That percentage is likely to go even higher if ships are forced to do near consecutive 8 month deployment stints. Some ships will do other duties. They'll have to escort cargo ships over the pacific, which would be supplying Taiwan or US forces in general. That's because China might always sneak out a submarine or try to hit with very long range hypersonic light vehicles. Further ships might be needed around the world, even if just in token quantities. It's possible that the total tally available for ops near China would be just 50 or so ships. So ships with few missiles left would have to leave the area and sail towards a protected port. Where will that port be? That's gonna be changing in a war. Currently that's either Guam, Hawaii or ports in mainland Japan. But some of those, especially Japan and Guam, might regularly get struck by Chinese missiles. A Burke destroyer sailing from Taiwan to Tokyo or Guam has to cross 13 to 1700 miles. Realistically 20 knots might be its top speed over such long distances. That's 73 hours to Guam or 57 to Tokyo. That doesn't sound so bad, but it can add up. A return trip is needed, plus a few days to actually replenish the ship. Loading just a single missile requires a port crane, lots of people and can take up to an hour. So a ship might lose roughly a week to get back on station. As said, those figures might get worse. If China manages to keep those ports harassed, the US might send ships farther away to get resupplied. While Pearl Harbor might be a bit too pessimistic, even Australia makes the whole trip too long at nearly two weeks, for a two way trip plus reloading. The US procured some 3500 Harpoon anti-ship missiles during the cold war. Given the number of platforms it used, China's platforms and decades during which China produced its various missiles, there are likely to be at least a similar number of anti-ship missiles in China's arsenal, that's not counting land attack missiles. If out of 50 or so ships the average US ship near China needs to restock on missiles every month, that may be a week or two out of action for every month. That's a lot of downtime, effectively lowering the number of deployed ships further. Perhaps to just 30 something ships deployed. Also, those ships would be dispersed. The pacific front might be over 2000 miles wide. A ship without enough missiles is of course nearly useless. Even if it's a 3 billion dollar package, counting its missile load. If ships don't need to sail a long way but can just go back a few hundred miles to reload, more ships will be available on station. A 2019 study by Center for Strategic and Budgetary Assessments suggested that just having three replenishment ships serving a force of 48 destroyers in the pacific to rearm them at sea could effectively yield an equivalent of 5 to 18 more destroyers on station, depending on the exact distance of the rearmament location from destroyer's deployment point. But how will the US navy achieve this? First, what doesn't work? Using helicopters. There's just too much movement, both from the helicopter and the ship at sea. Each of those containers with missiles weighs 2 to 3 tons and has quite a bit of momentum. Breaking a lid of a nearby missile cell could easily happen. A member of the crew might get hit by the container. But most likely, any hit would dent the container itself and possibly damage the missile inside. Imagine trying to launch a damaged missile inside a well full of other missiles. That could risk a catastrophe. The navy is pursuing a few ideas. Using vehicles with cranes has been done before, but those aren't optimal. And not all ports have them. So the navy is experimenting with ships with their own cranes to do the loading in small ports. Basically even ports where there are no port facilities with large cranes. That would greatly increase the number of ports available to the US navy. It would complicate matters for China, as it probably could not keep all those potential ports harassed by missile attacks. Supply ships have their own cranes, so those were tested too. All those work as intended, but while it helps, it's not really a cure for the problem. Ships still need a harbor and cold water for the transfer. The US navy has, however, two more solutions. One seems to be fast-tracked right now, even though it's not perfect. But it seems to provide a good enough solution in the short term. The system is called TRAM, transferable rearming mechanism. It's been tested on land, and tests at sea are scheduled for this year. It's basically a simple crane system that is likely modular, to be assembled on a ship near the VLS well. Images of the land tests show rails on which the crane assembly moves over the VLS cells. The crane itself is articulated, and big enough to handle even the biggest missile containers. The biggest change seems to be the fact that the crane rotates, raises and lowers the missile on its own, without too much help from the loading crew. Regular loading systems have the missile container simply hang from a crane on a cable and sway around. But the TRAM system seems to firmly hold the container in its grip, on a rail. As the crane itself gets fixed above the empty launch cell, the rail moves the container precisely into place and slides it down the cell. There's not too much info on the TRAM system available, but it's plausible it uses some sensors and automation to help the whole process. Of course, a crane operator is still present. The whole idea likely means a missile can be reloaded more quickly. And the crane is, as its name says, transferable. So the question remains how to transfer the crane onto the ship, and how to transfer missile containers to the crane. That has not yet been demonstrated, but if we had to guess, it could be done using regular resupply ships. If the sea state allows it, a resupply ship will use one of its regular cranes to hand off TRAM components to a destroyer. Those components may not be as heavy nor as sensitive as missile containers, so they would be easier to hand over and assemble. Once the TRAM crane is in place, missile containers may be moved onto some sort of, and this is just assumed, prepared soft mats on the destroyer's deck. Then the TRAM crane might take over. Another option could be relying on regular cables for transfer of pallets. If the cable attachment point and the delivery point is close enough to the TRAM crane location, then the TRAM crane could take over. That, however, has yet to be demonstrated. Perhaps a better and more permanent solution would be this. The US Navy has in the past also experimented with specialized large cranes. Large supply ships could be retrofitted to feature novel heavy-duty but articulated and automated cranes. Said cranes move in six axes and account for all movement, including waves, and can quite precisely and gently lower containers. Now, 15 years ago that tech may have not been super precise, and perhaps it's still not good enough to directly lower a missile container gently into their cells. But at the very least, it seems good enough to put a container right next to the TRAM crane. Or in some hypothetical next version of the TRAM crane, to have the big crane hand over the container in air. Those systems may not be in widespread use for years, as retrofitting many supply ships would not be quick. But the TRAM system alone is still a step in the right direction, and may enable the US Navy to keep more ships on station. Whatever the pace of development is, it's not gonna be slow. The US Navy seems to be aware of the urgency, and we will likely see some sort of Etsy replenishment in actual widespread use soon, possibly within mere years. And remember, Binkov may talk about war, but only real peace can bring us all together.