In my examination of the various exotic forms that naval architects have come up with, so far we've stuck purely to various forms of displacement hull, where the force that keeps the ship from sinking is provided entirely by water being pushed out of the way. But this leaves the entire hull in the water, which in turn means lots of resistance when trying to go fast. So for really fast ships, there needs to be some other method of providing "lift" which keeps more of the hull out of the water.

A US PT Boat planes

The oldest and most common of these methods is known as "planing". To take a simplified model, if a flat plate is towed through the water with the forward end higher than the back end, it will deflect water downward, which in turn will push the plate up, producing lift much like an airplane's wing does.¹ This is the basic mechanism behind all planing craft, and has the advantage that once the majority of lift is provided by planing, the resistance grows more or less linearly with speed, a far less onerous scaling than experienced by a displacement hull. But planing as a concept runs into another problem: the amount of lift required to plane varies with the weight of the craft divided by the area of the bottom,² a ratio that rises with vessel size. The result is that while a surfboard can plane while falling down a wave and a jet ski can often plane at 20 kts, bigger craft need a lot more speed to get on the plane, putting it out of reach of anything over 50-100 tons, which means that military use is limited to fast coastal craft like torpedo boats rather than proper warships. Read more...

Last time, we discussed multihulls, the catamarans and trimarans that are make up a small but significant portion of the world's fleet. Most multihulls are designed primarily for high speed, but for high speed to be useful, it needs to be practical if the sea is less than calm. Fortunately, naval architects have worked out ways to solve this problem, some of which can also be applied to conventional ship, and have even come up with a catamaran derivative, known as SWATH, that provides unmatched seakeeping for its size. But we'll start with an illustration of the basic principle at its simplest with the wave-piercing bow.

Axe-type wave-piercing bow and conventional bow, showing the different shapes

The basic concept behind a wave-piercing bow is simple. Imagine a normal ship is sailing along over a flat ocean, then runs into a wave. The bow is going to reach the wave first, and as the ship is horizontal, it will be pushed into the wave. This means that the waterline there will be higher than normal, and on a conventional bow there is quite a bit of flare,³ so the bow displaces more water, which means more buoyancy, which in turn pushes the bow up. The end result is that the ship will pitch up and down as it passes through the waves, which is the major cause of seasickness and also impairs decision-making. A wave-piercing bow has less buoyancy than a conventional bow, particularly above the normal waterline, and as such, pitches the ship less when it runs into a wave. The downside to this is that the bow rising keeps the water further away from the deck, so ships with wave-piercing bows tend to be pretty wet forward. This is a serious problem if the designer hasn't taken it into account,⁴ but can work if nobody is expected to be standing in the areas that keep getting wet. Read more...

It's time for our regular Open Thread. Talk about whatever you want, so long as it isn't Culture War.

This past week, I was a guest on Patrick McKenzie's Complex Systems podcast, talking about ways that the defense industry differs from others, why discourse about "drones" is often wrong, and posing him puzzles from the history of Operations Research. I was delighted to be able to talk to him, and I think it turned out well. (Oh, and for those who don't do audio, there's a detailed transcript at the link as well.)

For those who got here from Complex Systems, hello, and thank you for coming. Naval Gazing started off as a blog about battleships, and has since spread out to cover a lot of stuff. If you're new to defense issues, I would recommend looking through the Intro tag, where I've tried to collect the writing that would be of most use to someone who has no background in the field. And feel free to ask questions, which either I or one of the regulars here should be able to answer.

Overhauls are A Brief Overview of the US Fleet, Military Spaceflight Part 4 and for 2024, Early Underwater Weapons, The Problem of Defense Economics, and reviews of military museums in Boise and the Danish steam frigate Jylland.

Over the years, naval architects have come up with a variety of unusual hull types for specialized roles, and it's worth taking a look at some of them. There are benefits and drawbacks to any departure from the conventional monohull, and while for most roles, the tradeoffs aren't worth it, a few have seen reasonably wide use. We'll start with the oldest of these by far, the multihull. Typically, these can be divided into catamarans, with two fairly similar hulls and trimarans, with a single big hull in the middle and two smaller hulls out on the sides.

A replica Polynesian catamaran

The basic idea of making a ship with more than one fairly conventional hull dates back to the outrigger boats used by the Austronesians in their expansion across the Pacific. At first, these were simply two dugout canoes with a platform between them, a design probably adopted in search of the great advantage of the multihull, excellent stability. The reason for this is extremely straightforward. Stability is the resistance of a ship to rolling over, and it comes from hull on the downward side being pushed deeper and displacing more water while the hull on the upward side displaces less. On a catamaran, with the hulls split apart, this effect is significantly stronger, a useful feature if you are planning to carry a large sail on a small boat. But any case where there are two or more separate points of contact with the water can produce the same effect, and the Austronesian catamaran eventually evolved into the more typical outrigger designs used in the astonishing expansion across the Pacific Ocean.⁵ Read more...

On May 17th, 1987, USS Stark was on patrol in the Arabian Gulf. Iraq and Iran had been at war for most of a decade, and things had escalated from a simple battle for territory into both sides trying to interdict the oil that was funding the other's war machine. Iran was faced with a trickier situation. They had cut off direct Iraqi access to the Arabian Gulf early in the war, so Iraqi oil was transshipped via neutral powers, such as Kuwait and Saudi Arabia, and those same powers were funding Iraq's war effort. Kuwait had finally become concerned enough to request American involvement in protecting its tankers, and while the actual program had yet to begin, the USN was increasingly active in the region. Iraq had the easier job of things, as Iran's main oil facilities were quite close to its territory and the tankers that moved its oil out of the gulf were relatively easy to attack with French-made Exocet missiles. In the previous 10 months, they had flown 340 sorties and launched 90 Exocets, which had reportedly damaged about 40 tankers. And while this was annoying to the insurance companies (because the Exocet was too small to be a serious threat to a tanker) bystanders were generally safe.

Stark earlier in her career

On this specific day, Iraq was deploying a new plane. The Dassault Mirage F1 had been the backbone of Iraq's naval strike force for several years, but its range was pretty limited, so the Iraqis had requested that Dassault modify a Falcon 50 business jet into a "trainer". A Mirage F1 cockpit was installed on the right side, and an Exocet hardpoint was fitted under each wing. As the plane, codenamed Suzanna,⁶ headed out over the Gulf, it was picked up by a USAF E-3 Sentry operating out of Saudi Arabia, which thought it was a Mirage F1, and classified it as a friendly fighter on the Link 11 network operating in the Gulf. Read more...

This is the second half of John Schilling's two-part effortpost on SCUBA diving, originally written for Data Secrets Lox. The first part covered basic recreational diving, while this one looks at more advanced topics.

This time we’ll be focusing on technical and professional diving. Note that these aren’t strictly the same thing. “Technical diving” refers to anything beyond the limits of no-decompression open-cycle scuba diving. And there are amateurs who learn those skills for recreational purposes, e.g. visiting interesting or historically significant shipwrecks at 40-80 meters. There are also professionals who can do their jobs using nothing but recreational-grade scuba gear and techniques. But for our purposes, I’m just going to fold them both together into the broad category of stuff beyond ordinary recreational diving.

Most of this is going to be stuff that’s more difficult, more expensive, and more dangerous than ordinary recreational diving, but also more rewarding. Let’s start with the risks. I already listed all the things that could kill you in the course of a brief recreational dive to no more than forty meters, if you aren’t careful. Here’s a few more to worry about if you’re going really deep. Read more...

This is the first half of a two-part effortpost on SCUBA⁷ diving originally posted at Data Secrets Lox by John Schilling. This part is devoted to the basic principles of scuba diving and the hobby of recreational diving, while the second half will cover more advanced technical diving, and professional or military diving activities.

Diving is not actually all that difficult, at the most basic recreational level. You’re not going to suffocate or run out of air – there’s plenty of that no more than twenty meters (65’) away, and you’re buoyant enough that if you drop your weight belt you’ll float to the surface in seconds. You shouldn’t be diving deep enough or long enough that even an emergency ascent will give you “the bends”. And the sharks aren’t going to eat you.

But it absolutely does require training, about two full weekends’ worth, because there are some ways to kill yourself very quickly if you do something stupid and the not-stupid things, while easy to describe, are neither obvious nor instinctual. Your first few dives need to be with an expert watching closely to make sure you don’t do anything stupid. At that point you scan safely spend an hour or so looking at already-known Neat Stuff down to about twenty meters, in calm open water in daylight. Highly recommended if you live or vacation anywhere with good diving, because there’s a lot of neat stuff to see. There are several agencies that certify recreational divers; PADI (Professional Association of Diving Instructors) is probably the largest, but the others have their fans (and occasional holy wars). Without a certification card from one of them, nobody will rent you dive gear, nobody will fill your air tanks, and nobody will let you on board their dive boats. Read more...

It's time once again for the regular Open Thread. Talk about whatever you want, so long as it isn't Culture War.

Overhauls are my review of Batfish, the list of US museum ships, Italian Battleships in WWII, NWAS Light Attack Part 1, NWAS Cruise Missiles Part 1, Zumwalt Part 2, my review of Hornet, Military Spaceflight Part 2, and for 2024, Military Spaceflight Parts nine and ten, Air Attack on Ships Part 6 and Southern Commerce Raiding Part 9.

I'm going to designate tomorrow (8/2) at 1 PM Central Time (GMT-6) as the Schelling Point for anyone who wants to hang out in voice chat on the Discord. I will probably be there, but might have other things going on.

As a companion to my series on US military aircraft, I'm going to take a similar look at the military aircraft of our allies, and then of the rest of the world. Note that this is less comprehensive than the US version, as there are a lot of countries operating a lot of planes, and I am not going to tear my hair out trying to find all of them. But I will mention the major players, along with a few interesting oddities.

Fighters

Fighters worldwide play much the same role they do for the US, although it is worth noting that nobody outside the US, Russia and China operates bombers, so for all of our allies, fighters also handle the high-end ground attack work. Adoption of US fighters has been reasonably widespread, but major countries often build their own as a matter of national sovereignty and to support their aerospace industries. Read more...

The utility of space-based imagery was obvious almost from the moment that people thought of putting cameras in space, but for the first decade or so of spaceflight, the ability to launch things was limited to only the USSR and the US, and they used this capability primarily for military purposes, with limited exceptions for communications and meteorology.

Dick Gordon sets up a Hasselblad camera in the Apollo 12 simulator

Because of the cloak of secrecy that shrouded both side's reconnaissance satellite programs, the first good look anyone in the wider world got at the Earth from space was through cameras carried aboard manned spacecraft. At least on the US side, these were Hasselblad handheld cameras, and produced stunning photos that had nowhere near the resolution of something like Corona. But they were still of great interest to researchers in fields like agriculture, forestry, hydrology and geology, who had a new window onto the planet that they studied. Pressure began to build for a dedicated platform to produce low-resolution imagery for Earth scientists, finally culminating with the flight of Earth Resources Technology Satellite-1, later known as Landsat-1, in 1972. Read more...