December 26, 2018

The Great White Fleet Part 2

In 1907, Teddy Roosevelt ordered the bulk of the American battlefleet sent from its bases on the Atlantic to the West Coast in a test of its readiness to deploy quickly, in the event of a war with Japan. The resulting force, known as the "Great White Fleet" due to the gleaming paint scheme used, reached San Francisco in May 1908, to a tremendous welcome.

The Great White Fleet in San Francisco Bay

Even as the fleet was completing the last legs to the West Coast, it was announced that it would return to the East Coast via Australia, the Philippines, and Suez. This promptly set off a diplomatic storm, as nations along the route vied to get a visit from the fleet. Australia had moved first, issuing an informal invitation before the battleships had even passed through the Strait of Magellan, but American efforts to forestall further invitations by announcing the route early proved futile. New Zealand and Japan were quickly added to the itinerary, although in both cases only one port would be visited. The Chinese invitation was also accepted, although only after considerable wrangling over the site of the visit and the number of ships to participate. A British invitation for a visit to the UK was turned down due to time constraints, but their offer of their numerous bases along the route, most prominently Gibraltar, was gratefully accepted. Read more...

December 23, 2018

Electronic Warfare Part 3 - ECCM

I've previously discussed the fields of Electronic Signal Measures (ESM) and Electronic Countermeasures (ECM). But now let's turn to the third major branch of electronic warfare, Electronic Counter-Countermeasures (ECCM). ECCM is concerned with defeating or at least mitigating the effectiveness of ECM, through a variety of techniques even more diverse than those used to attack systems in the first place.

Modern AESA radars like this AN/APG-81 incorporate many ECCM features

The most basic ECCM technique to counter jamming is increasing transmission power. Because radar return strength falls off with the fourth power of range1 while jamming falls off with the square of range, at some point the reflected signal will be stronger than the jammer, and the radar will pick it up. This is a particular problem when airborne platforms attempt to jam surface radars, which have much larger power budgets. Read more...

December 21, 2018

Spot 1

I've had the privilege of getting to see the inside of the forward Mk 38 Main Battery Director on both Iowa and Massachusetts. This position, known as Spot 1, is the primary position for main battery fire control, and provides an incredible view of the area around the ship. I thought I'd share some of my pictures from the visits.

The outside of Iowa's Spot 1

The basic purpose of the director is to provide range, bearing and level information to the fire-control system. This information allows the ship to know the position of the target and to compensate for the ship's own roll and pitch, so that it can place shells on the target accurately. Read more...

December 19, 2018

Electronic Warfare Part 2 - ECM

Last time, we discussed the basic division of electronic warfare into Electronic Signal Measures (ESM, detection of enemy electronic signals), Electronic Countermeasures (ECM, use of active measures to mess up enemy signals) and Electronic Counter-Countermeasures (ECCM, techniques to defeat enemy ECM), and how ESM works. This time, we'll look at the area most people think of when they talk about electronic warfare, ECM.

A radar screen showing the effects of jamming

The most basic ECM technique is simple noise jamming. This is flooding a relevant portion of the electromagnetic spectrum with white noise, with the intent of drowning out the relevant signal. For a radio, it's the equivalent of trying to talk while someone blasts loud music, and the same principle applies to radar, reducing the range at which a radar unit can get a useful return. Noise jamming is usually divided into a few categories, spot, barrage, and sweep. Spot jamming is transmission on a specific frequency, which is highly effective if the system in question is limited to only a single frequency. However, most modern radars are "frequency agile", which means they can switch away from a jammed frequency among a much wider band. One way to counter frequency agility is to jam the entire band the radar could be operating in, known as barrage jamming. The problem with barrage jamming is that it is rare to find a jammer powerful enough to be able to blanket a wide spectrum. Sweep jamming, where the jammer's power is swept across a variety of frequencies, is capable of defeating electronics with poor error-checking, although it's not particularly useful against better-designed systems. Read more...

December 17, 2018

Open Thread 15

It's time for our usual biweekly open thread. Talk about whatever you want, even topics unrelated to the subject of the blog.

This week, I'm going to highlight Nomenclature of Naval Vessels, a 1942 publication on all of the terms that get used on ships.

Updates over the past two weeks include Ironclads, The Loss of HMS Victoria, The Death of Force Z, Parts One and Two on Huascar and The South American Dreadnought Race.

December 16, 2018

Electronic Warfare Part 1 - ESM

Over the past century, warfare has increasingly been taking place on the electromagnetic spectrum. A century ago, primitive radio first gave commanders the ability to control forces at sea across great distances. Attempts to thwart enemy communication, or to turn it to one's own ends, swiftly followed. During WWI, both sides tried to jam the other's communication, and set up direction-finding networks to locate the source of transmissions. These set the pattern that has been followed with increasing sophistication ever since.

An RC-135 Rivet Joint, the premier USAF electronic intelligence aircraft

Electronic warfare is usually divided into three parts: Electronic Countermeasures (ECM), Electronic Counter-countermeasures (ECCM) and Electronic Support Measures (ESM).2 ECM is concerned with denying the enemy the use of the electromagnetic spectrum. This is conventionally done by jamming, the electronic equivalent of playing loud noise to drown out sounds you don't want someone else to hear. ECCM is a wide variety of techniques intended to mitigate the effects of ECM. If someone is playing white noise to stop you from hearing a specific note, it might be the use of a signal processor to listen to only the specific frequency you care about. ESM is primarily concerned with locating and characterizing the emitters of the other side. In our acoustic analogy, it would be learning the sounds of someone else's car so you can recognize them if they come after you, or using multiple microphones to locate someone trying to sneak up on you in the dark. Read more...

December 14, 2018

Commercial Aviation Part 3

Earlier, I talked about how airlines sell tickets, to get the most money out of their passengers. This time, I’m going to talk about the mechanical process of getting those passengers where they want to go. The basic problem is that there are an almost arbitrarily large number of combinations of A and B people want to travel between, and it’s obviously impractical to have direct service between all of them. Different travelers want different things, and the whole system is constrained by available airplanes and airports.

MD-83 of Allegiant Air

So, how do we take the planes I talked about last time, plus all of the airport infrastructure, and create a route network that will get people where they want to go? This is hard to describe from first principles, so we’ll examine a couple of airlines to see how they do things.


December 12, 2018

The First South Dakota Class

The Washington Naval Treaty of 1922 brought about major changes in the design of the battleship, most notably cancelling most of the ships being built in American and Japanese yards. In the United States, three classes were affected. I've previously discussed the Colorado and Lexington classes, but a third class, the South Dakotas, were cancelled entirely.

The South Dakota class as designed

The South Dakotas were ordered under the massive Naval Act of 1916, a result of Woodrow Wilson's swing towards naval expansion as the World War dragged on. Americans feared that a victorious power would turn its eyes across the Atlantic, seeking economic dominion over the United States. A fleet "second to none" would be vital to safeguarding US interests from a power with millions of battle-hardened veterans and a war indemnity from the loser. It was not apparent at the time the economic toll that the war would take on the participants, rendering any such dreams moot by 1918. The bill, on the floor of Congress when news arrived of Jutland, authorized ten battleships and six battlecruisers. While the first four were to be derivatives of the existing Tennessee class, the last six could be significantly larger, the ships the USN had been asking for since 1914. Read more...

December 09, 2018

The Falklands War Part 9

In early April, 1982, Argentina invaded the Falkland Islands, a few desolate rocks in the South Atlantic. The British mobilized their fleet, sending it south by way of Ascension Island. On the 25th, a force retook South Georgia, a even smaller and more desolate island that Argentina had also captured, while the main task force closed in on the Falklands. May 1st saw the British launch their attack. The Argentine Navy tried to interfere the next day, but withdrew after the cruiser General Belgrano was sunk by a submarine.

HMS Sheffield

May 3rd was quiet, but May 4th was not. The day began with the second Black Buck raid. While everything went smoothly, the string of bombs fell 600 yds wide of the runway, doing no damage to any of the airport facilities. The carriers closed in on Stanley during the night, planning another set of raids. Harriers flew off for CAP, while the three Type 42 destroyers, Glasgow, Coventry and Sheffield, moved further west, deploying down the threat axis about 20 nm from the carriers in a line 40 nm long. By this point, the fleet was beginning to treat the matter as routine, and at Air Raid Warning Yellow,3 procedure was to be at Defence Watches, with half the crew at their stations. When Air Raid Warning Red was sounded, the entire crew would go to their battle stations. The good performance of radars on May 1st had given them confidence to justify this procedure. Read more...

December 07, 2018

December 7th, 1941

2,403 dead. 1,178 wounded. Five battleships, one target ship, and three destroyers sunk, and many more ships damaged. 188 aircraft destroyed and 159 damaged. And the US drawn into the greatest war the world has ever seen.

This is the toll of the Japanese attack on Pearl Harbor. It was, as President Roosevelt said, a date which will live in infamy. More dark days were to come, in Malaya and Singapore, the East Indies, and the Philippines. But eventually, the efforts of the Allies pushed them back. Less than four years later, an American fleet was anchored in Tokyo Bay, and the Japanese came aboard the battleship Missouri to sign their surrender.