December 30, 2018

Information, Communication and Naval Warfare Part 2

In the aftermath of World War I, the RN and USN continued to develop the concepts they had created to handle information during the war, on both tactical and strategic levels. Aircraft added to the ocean surveillance picture, making it easier to survey wide areas, but the major development was in tactical plotting.

A sailor uses a Dead Reckoning Tracer

Plotting had first been introduced at Jutland, where it had given Jellicoe a decisive edge in positioning his fleet, despite problems with the implementation. During the interwar years, navies on both sides of the Atlantic worked out plotting techniques in exercises, added dedicated plotting spaces to their ships, and built automatic plotting tables which made an indication of the ship's location on a chart. The British maintained two separate plots, one for the strategic situation, and one for the immediate area around the ship in question. The Americans did not, and suffered in automatic plotting technology, too. The British used a device which projected a spot of light onto the map that moved based on the ship's indicated course and speed. The mechanical American Dead Reckoning Tracer tended to jump under the shock of gunfire. Plotting proved particularly vital in enabling night tactics, exemplified in the British victory at the Battle of Cape Matapan, where it gave them the confidence to avoid friendly fire and allowed them to take the Italians entirely by surprise. Read more...

December 28, 2018

Commercial Aviation Part 4

One aspect of air travel I'm particularly interested in is frequent flier/loyalty programs. These have three basic purposes from the perspective of the airlines:

1. They allow the airline to differentiate what is essentially a commodity product, a trip from A to B, and turn it into something unique.

2. They give customers an incentive to put all of their flights with a given airline.

3. They give the airlines the ability to sell lots and lots of miles to banks, who in turn use them to incentivize customers to spend on their credit cards. The banks collect their money on interchange fees.

We can divide the programs into two broad parts, status and points. Status is earned on an annual basis, and is designed to reward the airline’s best customers with upgrades, free checked bags, and other amenities. Most people don’t have status, and the easiest way to get basic status is through having a credit card. Points are earned by everyone, while status traditionally requires spending significant amounts of time/money with the airline. Read more...

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...