Sunday, May 25, 2008

The Fuze that Saved A Battle

In my last post, I mentioned the VT fuze. Before I get to the VT fuze and its importance, a short discussion of fuses is in order.

The earliest cannon projectiles were round shot. They were solid balls, first of stone, then of iron. Somewhere along the way, some enterprising person wondered if there was a way to combine the heavy throwing capability of a cannon with the blast effects of a hand grenade. Hand grenades, back then, were little more than containers packed with gunpowder. The grenadier would light a fuze on the grenade and throw it towards the enemy.

Obviously, stuffing a projectile with a lit fuze into a cannon barrel that has gunpowder at the other end is not a good idea. The early fuzes were little more than just that, the fuze would be lit by the combustion of the propellant charge, with the time to detonation determined by the length of the fuze. This had its drawbacks, so the impact fuze was developed. Depending on whether the shell was fuzed at the nose or at the base and how impact-resistant the fuze was, a projectile could be fuzed so that it detonated on impact or afterwards, to allow for penetration. Clockwork fuzes (also known as "mechanical timed fuzes") were also used to set projectiles to go off prior to impact, in order to spray shrapnel over a wide area. (In a throwback term to earlier days, setting a MT fuze is called "cutting the fuse").

This was about the state of fuze technology during the First World War. Still, fuzing was unreliable, I have seen estimates that a third of the shells fired on the Western Front did not detonate. As a result, the "Iron Harvest" continues to this day. Old shells, even from as far back as the Civil War, can still kill, as their fuzes have deteriorated and can be very unstable.

Timed fuzes were used against aircraft; the gunners would set the timers to go off at a set altitude. If the setting was wrong, the fuze would detonate the shell too high or too low. The Germans addressed this problem by having an airplane fly parallel to the Allied bomber formations and radio back the altitudes.

Timed fuzes were fine against level bombing attacks carried out at medium and high altitude, but they were useless against dive bombers. For a mechanical timed fuze to work. the gunner would have to estimate at what altitude the dive bomber would be when the shell reached the dive bomber, a near impossible task.

The answer was what was known as a "variable time fuze" or "VT fuze," which was a code name that did not reveal the true nature of the fuze, as every nation with antiaircraft artillery had timed fuzes. The VT fuze was a proximity fuze.

The VT fuze was a miniaturized radar set. That may sound like not so much of a big deal, but this was in the days before transistors had been invented. It was a huge advance to that point to have a radar set that was small enough to be installed in an airplane the size of a bomber. What the Navy's scientists and engineers had to do was develop a vacuum-tube range-only radar set that could not only fit in the fuze of a 5" shell, it would survive the massive G-force of being shot out of a cannon. And then, having solved all of those problems, they had to mass-produce them.

The only project that was deemed to be more critical than the development and production of the VT fuze was the development of the atomic bomb (a version of the VT fuze was used in the atomic bomb).

VT fuzes were used to shoot down Kamikazes and V-1 missiles. Without the VT fuze, the American death toll from Kamikazes would have been far higher. As it was, during the Battle of Okinawa, 34 ships were sunk, most by Kamikazes. The Navy had 5,000 sailors killed (the Army and Marines lost 8,000).

Whether the Kamikazes would have been able to cripple the Okinawa and Iwo Jima landing forces if the Navy did not have the VT fuze is a debate best left to the alternate history folks. But there is no doubt that VT fuzes saved thousands of American lives.

Saturday, May 17, 2008

Caliber and Other Musings

Naval rifles (what landlubbers refer to as "cannons") are traditionally designated by the diameter of their bores and by caliber. But in this instance, the "caliber" designation is nothing like civilian firearms.

Caliber, for a civilian (or Army) firearm, has some passing resemblance to the bore diameter. It varies, usually for marketing reasons. A .357 magnum can trace its bore diameter back through the .38 Special, the .38 Long, the .38 Short and all the way back to the .36 of the Colt Paterson revolver. A .30 rifle has a bore diameter of .308", a .303 has a bore diameter of .311". A 7.62mm rifle can have a bore diameter of .308" (NATO) 0r .311" (Russian). A .44 is really a .43 (.429"). And so on.

Caliber, for naval rifles, is the length of the bore from the breech to the muzzle divided by the diameter of the bore. The main guns of an Iowa-class battleship had a caliber of fifty, which meant that the length of the gun barrel itself was 800 inches (16"x 50); the designation of a 16" gun was a "16'/50". A common small-caliber gun in use up until the 1970s was a 3"50, which meant that the gun barrel was 150" long.

The 3" round was the largest one-piece round (known as "fixed ammunition"), in that the projectile was mated to the cartridge case. The 5" has a separate projectile, the cartridge case contains only the powder ("semi-fixed ammunition"). The old 8" and 16" guns used bagged powder, a method of powder handling that dated back to at least the 18th Century. The last versions of the 8" guns used powder in cartridges. So did the light-weight 8" gun project of the the 1970s, which was canceled thirty years ago.

The predominant medium caliber gun through World War II was the 5"/38. (When the projectiles were fitted with one of the technological wonders of the war, the VT fuse, the 5" guns wiped out most of the Kamikaze attacks. ) The ships built from the 1950s on were fitted with guns that had longer barrels: 5"/54s. The 5"/54 Mk.42 had provisions for local aiming with positions for one or two gunners. The Spruance-class destroyers were the first to be equipped with the Mk.45 5"/54, which eliminated the gunner's position. A new version of the Mk.45 that sports a 5"/62 gun is supposedly in use, which has higher chamber pressures and would have been able to throw a new rocket-assisted projectile (RAP) out to 60 miles.

When I first heard about this project, I was dubious. The Navy experimented with 5" RAP back in the late `60s and early `70s. RAP was renown for having two problems. One was at the extended range, you couldn't hit a damn thing with it. Second was when you added in the rocket parts, you were left with a something which was not a hell of a lot more powerful than a hand grenade, which made the RAP the world's most expensive grenade launcher.

So, to get around those problems, the idea became to basically throw a GPS-guided rocket out of a 5" gun. The projectile was going to be a lot longer and heavier than a standard 5" rounds, which of course meant that it would take up more space in the magazine and it would be much slower to load. Because the projectile being thrown out was a lot heavier than a standard round, the cartridge cases contained more powder. As any rifle wildcatter knows, more powder means higher chamber pressures and shorter bore life.

Apparently, it didn't work very well and the project has been recently shitcanned.

Thursday, May 15, 2008

Power Generation

There were several types of generators. Generators were classified by both type of service and by the type of prime mover which motivated the generators.

Ship's service generators were designed to provide electrical power to the ship during normal operations. The sizes that I saw ran from 500 Kilowatts to 1,500 Kw, with a voltage output of 440 volts. The motive power was either a steam turbine (a turbogenerator), a diesel or a gas turbine. Therefore you had SSTGs, SSDGs, and SSGTGs.

Emergency generators were fitted to some ships. These generators provided less power than a ship's service generator. They were either diesels or gas-turbines, as Solar gas turbines were fitted into the bows of some cruisers. Steam, for reasons that either are or will soon be obvious, was not used to power emergency generators. Therefore you had EDGs and EGTGs.

Some ships did not have emergency generators. The Knox class frigates had diesel generators that were of the same rated output as the SSTGs, they had one SSDG per ship.

Motor generators were driven by electrical motors. I wrote about LAPS here, the MG set which provided transmitter power to the SQS-26 sonar system. There were other MG sets, including one or more which provided 400Hz AC power for use in parts of the sonar and fire control systems. 400Hz power provided for much finer control than did standard 60Hz power; there were probably other reasons, which were explained to me in some boring electrical class and which I forgot as soon as I took the test.

Let's now consider the steaming of a Knox class FF and its electrical plant, which was about as simple a plant as there was. A Knox class ship had two boilers in one fireroom; one boiler was steamed for normal operations. Just forward of the Fireroom was Aux 1, which contained three SSTGs, each of which was rated for 750Kw. During normal steaming, two of the SSTGs would provide power to the switchboard in Electrical Central; the third SSTG would either be in standby or would be offline for routine maintenance.

Aux 2, which was well aft of the main plant, contained a SSDG and a separate switchboard. This was a very large unit, consisting of two V-16 GM diesels that drove the generator, and it was loud enough that double-hearing protection was required during operation. During normal steaming, the SSDG was offline and aligned for automatic start in the event that power was lost. Some ships would start the SSDG and bring it on-line for activities such as entering or leaving port or underway refueling; this ensured that if the plant failed for any reason, electrical power would not be lost at a time when having rudder control was vital. The SSDG was also aligned so that in port, if power was lost, the SSDG would start up (unless it was down for maintenance). If power was lost underway and the SSDG didn't start, you were shit out of luck.

If power was lost, whether underway or in port, the enginemen and the electricians would man up the SSDG and the After Switchboard. (In port, the electrician would immediately trip the breaker for the shore power lines, to prevent "feeding back" to the pier. ) Loss of electrical power underway meant that the boiler(s) had fires pulled, as there were numerous pumps in the main plant which were driven by electrical motors, including the condensate pumps, the main feed booster pumps and the fuel oil service pumps. Electrical devices throughout the ship were either on LVR or LVP switches. LVRs tripped off when there was low voltage and automatically came back on when there was enough voltage. Lighting and security systems were on LVR relays. LVPs were on items that were either not vital or that the power drain was such that it was not desirable for all that stuff to come on at the same time.

Underway or in port loss of electrical power triggered an automatic security alert, where teams of sailors with guns would arm up and fan out about the ship to secure vital areas.

Underway, the boiler techs would work as fast as possible to get the boiler back on line. This was usually little more than use a periscope to look inside the firebox for spilled fuel and if none, start the light-off blower, get fuel recirculating through the lines and light fires. Once fires were lit, the boiler stops were opened, the SSTGs would start rolling over and as soon as the boiler was up to pressure, the SSTGs would be brought back on line and the main engine would start turning.

As the old saying went, for the screws to turn, the fires must burn, so Engineering was matter of "turning and burning."

Sunday, May 4, 2008

Navy Showers

You might have heard of a "navy shower." What you do is turn on the water, wet yourself down and then shut off the water. You soap yourself up, turn on the water, rinse yourself down, and you're done.

Navy ships do not have water to waste (and I will write about how fresh water is produced some other time). The standard for the use of potable water was 25 gallons a day for each person on the ship. So if you have a ship with 250 officers and sailors, that works out to 6,250 gallons of fresh water per day. That is not just for showering, that is for all uses: Cooking, washing pots and pans, laundry, showering, swabbing the decks, drinking, everything.

Fresh water use is a critical item, for if a ship runs low on fresh water, then "water hours" are imposed. During water hours, the showers are secured except at designated times and, often, for designated people. The cooks get to shower, the sailors who got really filthy at work get to shower, but the "radar girls" up in CIC, the radiomen, and the sonar techs, among others, have to suck it up and do without.

So some genius at the Naval Sea Systems Command came up with the idea of a special low-flow hand-held shower head. The user would have to bring the nozzle up close to his or her body and then hold down a button on the shower head to spritz down their body. Needless to say, they were not popular. Some folks on the ships thought they were hazardous, as a sailor would have to rub down the rinsing area to make it work better, so that was one hand holding the nozzle, one hand rinsing off. That left no hands to grab onto the grab iron in each shower in the event of a severe roll of the ship.

Add to that the fact that some ships were pretty disciplined on water use and, unless there was an engineering casualty, had refilled their freshwater tanks by the beginning of the work day.

So we go now to one of those ships. The supply system had delivered enough of the new shower heads to refit every shower on the ship, with some left over for spares. The Chief Engineer ("Cheng"), who was intimately familiar with the ship's use of water, regarded those shower heads with the skepticism due any idea from the shore pukes. Cheng ordered the division officer whose sailors would install the nozzles to put them aside and to work on more important things, important being defined as "everything else."

The Supply Officer, who knew that the new shower nozzles had arrived, asked Cheng when they would be installed. Cheng politely advised the SuppO to "mind yer own fuckin' business."

The XO soon found out that the new shower heads were on board. He asked Cheng if they had been installed. Cheng said no, that the sailors who would do the work were "busy." The XO caustically observed that if he waited until they weren't to have them installed, they'd never be installed. The XO ordered Cheng to "start installing those goddamned shower heads."

And so Cheng did. The shower heads were installed first in all of the showers in Officer Country, including the showers in the private heads of the Captain and the XO, and they were also installed in the head in the Goat Locker (the slang term for the "Chief Petty Officers' Quarters"). Cheng then sat back and waited.

The Captain advised the XO that the new shower heads "sucked." The XO, of course, knew that from personal observation. The junior officers grumbled audibly. But the biggest reaction came from the Goat Locker. The chiefs in B and M divisions knew what the fresh water usage of the ship was, they knew that the new shower heads were not needed. They made that point vocally to the other chiefs. The Command Master Chief relayed the complaints to the Captain and the XO.

And the chiefs had a plan. The R division chief ordered his sailors to reinstall the old shower heads and to "forget you ever saw the new shower heads." The sailors, who didn't want to have to use them themselves, were happy to comply. The chief storekeeper made sure that the supply records of the ship did not show that the new shower heads or any of the spare parts had ever been received.

For the next time that the ship went to sea, the R division chief threw the new shower heads over the side.

Problem solved.