I've previously covered the development of naval steam propulsion systems, focusing on those used aboard battleships. But from the dawn of the 20th century, other systems were developed to push ships through the water, and today, variants of these systems dominate the marine propulsion landscape.¹

Diesel engines are checked aboard USS San Antonio

The first serious challenger to steam was the diesel engine, which began to go to sea even before WWI. It had three major advantages over steam. First, it was significantly more efficient at turning the energy of the fuel into rotation, with diesels having two to three times the horsepower per unit weight of fuel per hour as contemporary steam engines. Second, they were easier to run and maintain, requiring fewer crew. These two advantages made diesels attractive to merchant ships, although adoption wasn't universal until after WWII. And third, they were far faster to throttle. A boiler could take an hour to produce steam from a cold start if another boiler on the ship was available, and far longer if the entire plant was cold. This often meant that warships had to operate inefficiently, with more boilers online than they needed at the moment in case demand for steam increased. Diesels could be turned on and reach full power almost immediately, then shut down just as rapidly. Read more...

It's time once again for our usual open thread. Talk about whatever you want that isn't culture war.

Scott Alexander, formerly of the blog Slate Star Codex, where Naval Gazing came from, is back, with a new Substack blog, Astral Codex Ten. And DSL is running the monthly effortpost contest, with 17 entries for January.

2018 updates are Russian Battleships Part 2, Why the Carriers Aren't Doomed Part 4, SYWTBABB - Strategic Background, Early US Battleships, Aegis and Amphibious Warfare Part 1. 2019 overhauls are the Mk 23 Katie, Commercial Aviation Part 6, the King George V Class, German Guided Bombs Part 1, The PHS Corps and my history of Wisconsin. And 2020 overhauls are Operation Crossroads and Battleship Torpedoes parts one, two and three.

The story of the lighter-than-air craft at sea is not one of success. Early attempts were not particularly successful, with the RN being a particular loser when their first rigid airship broke in half before its first flight. The Germans did somewhat better, with Zeppelins being used extensively on patrol missions in the North Sea and the Baltic. But bad weather and poor doctrine meant that they were generally not particularly effective, and the Naval Airship Division began to look for other missions.

The most obvious of these was using the Zeppelins as bombers, attacking far behind the lines. The Army had used its airships in a number of raids on targets in continental Europe, with little success and fairly heavy losses. But the Navy believed that bombing London could, in conjunction with unrestricted submarine warfare, destroy British morale and bring the country to its knees. Eventually, the Kaiser consented to the raids, provided they avoided threatening the Royal Family and instead focused on military targets. Nobody seems to have realized that the inaccuracy of bombing made this completely impossible. The first raid was carried out on January 19th, 1915, and attacked several towns in Norfolk, killing four. More raids followed throughout the year, and the Royal Navy, as traditional guardians of the British isles, was given responsibility for defending against them, although the Royal Flying Corps got into the game later on for overland interceptions. Read more...

By 1960, the age of the battleship was clearly over. Not a single one remained in active service anywhere in the world, although some of the treaty battleships still lingered on in reserve fleets. But while they were clearly outdated in fleet combat, the presence of such large, fast, and relatively young hulls drew interest for a variety of purposes.

Iowa as a Commando Ship (from Shipbucket)

One particular area of interest was an amphibious conversion. With the end of WWII and the advent of the atomic bomb, amphibious warfare was undergoing major changes, and the idea of turning a battleship into a helicopter carrier held some appeal. An early plan for the North Carolina class foundered when it was found to be more expensive and less efficient than a new-build ship, but plans for the Iowas, under the name "commando ship", lasted much longer. The basic idea was to disperse the amphibious force across more ships, to reduce vulnerability to nuclear attack, and to get the 16" guns back to sea to provide fire support, including the Mk 23 nuclear shell. Read more...

The past year has been reasonably productive. We've begun colonization of Gliese 892, with the first load of infrastructure delivered and a colony ship on the way. To support this, four AKXs have been built, and 6 more ordered. We've also made contact with the race that lives in Gliese 438, who call themselves the Zophris Association. At the moment, they've agreed to our requests to stop scouting Sol. Beyond that, the Martian population is over 10 million, and we've closed it to new immigrants for the time being. We've also got a gap in our factory's schedule, and need to figure out what to do with it.

Database is here.

In the late 1930s, the US was beginning to prepare for war. New submarines were being built, the first of the long-range "fleet boats" that would eventually starve Japan. One of these was Squalus, laid down at Portsmouth Naval Shipyard on the Maine-New Hampshire border in October 1937 and commissioned 17 months later. She began to work up, making 18 dives in the waters off New England. May 23rd would see her 19th, a crash-dive while making speed on the surface to check her readiness for a major inspection coming in June.

Squalus fitting out

Like all submarines of her era, Squalus was propelled on the surface by diesel engines, and they needed air to run. This entered the sub through the main induction valve, which would hydraulically slide closed just before the submarine dived. Obviously, an induction valve failure would be a very serious issue, and the crew took precautions. The so-called Christmas Tree, which showed the status of every valve on the boat, was watched closely, and as a backup, a blast of high-pressure air was released inside the boat, producing a spike on the ship's barometer. The dive was perfect, at least until they reached 50', only 62 seconds after starting the procedure. Then, crewmen began to feel their ears pop, and a report reached the control room that the engine rooms were flooding. Read more...

Whalers are not the only ships that go to harvest the bounty of the seas. Man has pursued fish for millennia, and continues to do so today using a variety of different methods. Fishing is a wide subject, covering everything from an angler with a rod on a streambank to fleets far out at sea using nets and the latest technology to catch fish for sale. It's this aspect I'll focus on, looking solely at commercial oceanic fishing.

Fishermen prepare longlines for salmon

There are two main ways to fish: you can either get them to bite on a hook, or catch them in a net. The latter is by far the most common, although longline fishing is an important part of the fishing fleet. This involves using a line with multiple baited hooks, as many as 2,500 on a 75-mile long line in some fisheries. This method produces the best fish quality, although the work of baiting the hooks means that it is reserved for either high-value fish like tuna or for species like halibut that live on rocky bottoms where nets don't work. Longlining is also generally considered to be more environmentally friendly than most nets, although bycatch, where non-targeted species are caught, is still a problem. Very occasionally, rod-type lines with one or a few hooks are used, but these have largely been replaced by other methods. Read more...

It's time, as usual, for our open thread. Talk about whatever you want, even if it's not naval/military related and isn't Culture War.

During the last virtual meetup, Trofim_Lysenko pointed me to this video, which is of a presentation by a senior Navy acquisition officer analyzing the Death Star program from an acquisition point of view. Highly recommended.

2018 overhauls are Bringing Back the Battleships, Why the Carriers Aren't Doomed Parts two and three, Stability, Pre-Dreadnoughts and Basics of Naval Strategy. Overhauled from 2019 were Interwar Naval Diplomacy, Commercial Aviation Part 5, Falklands Part 10, the Spanish-American War Part 1, The NOAA Commissioned Corps and Ship Structure and Strength. And 2020 overhauls are Aerial Decoys, Pictures-Iowa Enlisted Quarters, Escorts and Cool Facilities-Bayview.

Since the 1940s, engineers have invented many ways to guide weapons to their targets. The technical details of all these methods would undoubtedly fill a book (or many books), but a basic understanding of them is helpful to make sense of the tangle that is the history of guided missiles. We can broadly break them down into two types: target-based and location-based. Target-based guidance systems try to steer to a specific thing, be that a ship, an airplane, or a building, while location-based systems are going to a specific place. Another important axis is how much help the guidance system needs from outside. Some weapons are fire-and-forget, just needing to be pointed and told to get on with it, while others require more or less involvement by someone outside to get where they need to go.

An Atlas ICBM

We'll get location-based systems out of the way first. Traditionally, these were the preserve of strategic weapons like ICBMs and long-range cruise missiles, fired at targets over the horizon. The simplest system of this type is inertial guidance, which sums up all of the acceleration the weapon has done from a known starting point to figure out where it is and what it needs to do to reach the target. The problem is that any errors in measuring acceleration build up, and need to be corrected if you want to hit a target with a conventional warhead. At first, the corrections were radioed by an outside observer, but later systems were developed to allow autonomous operation, at first by using star sightings and later by matching against the terrain below the missile or looking at surrounding landmarks. Today, location-based guidance is ubiquitous thanks to GPS, which allows weapons like JDAM to hit precise targets with little outside support.² The only real drawback is that you need to know exactly where the target is. That's impossible if the target is moving, which covers a significant fraction of things we might want to blow up.³ Read more...

Whales have been hunted for thousands of years, and indigenous people still hunt them today from small boats, seeking meat and other products. But deep-sea whaling didn't become a major industry until the 17th century, and the main objective was not meat. It was instead whale oil, extracted from blubber, and baleen, the strainers that many whales use to filter their food out of the ocean.⁴

Whaling ship Charles W. Morgan, the oldest merchant ship afloat, at Mystic Seaport

Demand for both products ballooned in the late 18th and early 19th century. Whale oil was the best fuel for new, brighter oil lamps, and also a vital lubricant for the developing industrial revolution, while baleen was used anywhere where a combination of strength and flexibility was required, ranging from buggy whips to corset stays. Whale stocks in the North Atlantic quickly collapsed, and whalers had to venture further and further in search of their prey, often to the remote corners of the Pacific or the Southern Ocean. This trade was initially dominated by Americans from New England, with a high proportion concentrated in Nantucket, Massachusetts. Read more...