Sunday, December 28, 2008

ASW Weapons, the Conclusion

(Parts One, Two and Three)

The SQS-23 and other Korean-War era sonars, as I mentioned in Part 3, had the capability to detect and track submarines far outside the range of Hedgehog. The US Navy, among others, experimented with larger spigot mortars and rocket-thrown depth charges. Weapon Alpha was one that was largely unsuccessful.

All such weapons had the same problems; there was an unsatisfactory dwell time between the time the rocket was fired and the time the depth charge had sunk to the correct depth and detonated. All of those were predicated on the somewhat ludicrous idea that a submarine commander, knowing that he was being tracked by a destroyer, would hold a steady course and speed.

The answer was ASROC, for "antisubmarine rocket."

As you can see here, ASROC was a rocket which was fired from an eight-cell box launcher. The launcher itself used recycled deck mounts from 3"/50 guns. The rocket itself was a dumb, ballistic, solid-fueled rocket motor. Aiming was done by training the launcher and elevating the two-cell box with the ASROC to be fired. It worked out to be far more accurate than you might think.

On ships with Terrier (later, SM-1/2 ER) launchers (the DDG-37s, CG-16s and CG-26 class ships), ASROC was fired from the missile launcher. Each ASROC loaded was one less Terrier that could be carried. As the main mission of those ships was anti-air warfare, ASROC and ASW were the bastard stepchildren.

The business end of ASROC started out as a Mk.44 torpedo:

The Mk.44s proved to be unsatisfactory (among other things, it was slow) and were fairly rapidly replaced by the Mk.46. The torpedoes were active homers; they had a very high frequency sonar set. For guided weapons, they were the first true "fire and forget" weapons of the surface navy.

For close-in work, the torpedoes were also fired from deck-mounted launchers. Triple-mounts were added to a lot of ships:

The Knox class had twin mounts on either side of the after deckhouse, which were built into the deckhouse just forward of the LAMPS hangar.

ASROC also had a nuclear depth charge variant. This was the only live test, fired in 1962, before the Atmospheric Test Ban Treaty came into effect:

The nuclear ASROC worked like an old rocket-thrown depth charge, but with a hell of a bigger bang. The dumb-rocket version of ASROC left the fleet in the early 1990s when the ships with SM-1/2 ER or box launchers were all retired. A vertical-launch ASROC was eventually developed for use in current warships, though it reportedly was a pretty troubled development program.

ASROC could reach out several miles. But once again, the sensors outranged the weapons. The SQS-26 sonar, through either "bottom bounce" or "convergence zone" modes, could detect and track submarines way the hell out. The first solution was the Drone Anti-Submarine Helicopter, or DASH.

The concept of operation of DASH was simple: Fly the thing out until the markers from the sonar operator tracking the submarine and from the radar operator tracking the DASH converged, then drop the torpedo. Repeat if necessary (later models of DASH carried two torpedoes), then fly back to the ship for more fuel and torpedoes.

In practice, DASH didn't work so well. The drones were legendary for crashing and the DASH program was axed.

But that still left the problem that ships could track submarines further out than they could attack them. The answer was to provide ships with manned helicopters, the Kaman Seasprite, SH-2F LAMPS Mk 1:

LAMPS stood for "Light Airborne Multi-Purpose System," though a lot of sailors referred to it as "Lousy Air Mail and Passenger Service," for the best thing that the helo could for morale was to go get the mail from the carrier. The two drop-tanks you can see on this helo could be replaced by Mk. 44 or Mk. 46 torpedoes, though taking off a drop-tank reduced the in-flight endurance by 30 minutes. The red/white hashmarks outline the location of the sonobuoy launcher.

Late in the 1980s, LAMPS Mk.1 was replaced on the Spruance and Perry class warships by LAMPS Mk.3, which flew the SH-60F. The SH-60 program was supposedly the first aircraft procurement program where the prime contractor was not the airframe manufacturer (Sikorsky), but the electronics package manufacturer (IBM). Those ships were supposed to be able to hold two SH-60s. I never saw more than one LAMPS on a ship at a time and I think I maybe saw one SH-60s.

LAMPS would go out to the location of the submarine as determined by the active sonar track and stream a towed bird that contained a magnetic anomaly detector, the "MAD Bird." There were several different patterns the helo could fly to develop a track on a submarine; once the helo tracked it, it could drop a torpedo.

LAMPS also required a lot of people. The air detachment for LAMPS had three or four pilots and about 20+ sailors, with the senior officer being the head of the Air Department. More than one ensign or JG division officer in the other departments had more sailors and equipment to maintain than those fours officers in LAMPS, which lead to the standard complaint of: "I know what they do to earn their flight pay, but what do they do to earn their base pay?" The corrosion control program for the helos required that they be frequently washed with fresh water (the fresh water usage of the LAMPS detachment routinely led to the Chief Engineer threatening violence upon the Air Boss).

LAMPS pilots were certifiable. Take a look at the photo of this Knox-class FF and note the size of the flight deck:

Now imagine trying to land a helicopter on that deck, at night, with the wind burbling around the superstructure and the ship rolling a bit. The LAMPS pilots did that, and the flight deck on a Garcia class FF was even smaller. They had to be nuttier than a jar of Planter's.

LAMPS became even more important when surface ships began to be fitted with towed array passive sonars. If conditions were right, a towed array could be towed below the thermocline layer, down where submarines could hide from the hull-mounted sonars of ships. LAMPS were fitted with a launcher that fired off sonobuoys; little floats that dropped hydrophones deep into the water. The buoys had radio transmitters that send the signals to the LAMPS helo, which relayed them to the ship's sonar shack, where the signals were printed out on a frequency analyzer that was surplused from the P-3C upgrade program.

Sonobuoys came in several flavors. The ships had to pay for them and, as the ones with dumb omnidirectional hydrophones were the cheapest, those were the one used the most. There were sonobuoys with active pingers, but they were both costly and, as they alerted a sub that it was being hunted, not preferred.

Sonobuoys were used to localize a contact gained from the towed array. Once the contact was localized, the LAMPS helo would be vectored in for a MAD search. Once the helo had a MAD contact, then it was up to the three crewmen in the helo (two pilots and a sensor operator) to gain an attack solution and kill the submarine.

Friday, December 19, 2008

The Big Ensigns

This is an official photo of a Navy Rear Admiral (lower half):

His paygrade is O-7 (1 star), the equivalent rank in the Army is Brigadier General.

This is an official photo of a Navy Rear Admiral (upper half):

His paygrade is O-8 (2 stars), the equivalent Army rank is Major General.

In practice, the terms "upper half" and "lower half" are dropped.

Now you might be thinking of asking this question: "Comrade Misfit, why do two different naval ranks use the same title?"

Good question, and of course, there is a story behind that.

Historically, 1-star officers in the Navy had the rank of "Commodore." ("Commodore" is also the title of an officer who commands a squadron of ships, but that's not important right now.) For a long time, the Navy did not have 1-star officers; the rank was activated only when there were large wartime fleets. Officers who were promoted from paygrade O-6 to O-7 would don the uniform and insignia of a O-8. "Upper half" and "lower half" were used only for seniority and pay purposes.

What this meant was that on the day when a Captain was promoted to Rear Admiral, he would go into work wearing the uniform of an O-6 and go home wearing the uniform of an O-8.

As you might imagine, that griped the living shit out of the generals in the Army, Marine Corps and, most of all, the Junior Birdmen. The one-star generals in joint commands really hated the fact that they would go from being called "sir" by a naval Captain to having to salute the same guy after his promotion. They resented the hell out of that and complained to the Navy for decades. The Navy, of course, didn't give a flying fuck what the other services thought and regarded the offended brigadier generals as a bunch of crybabies.

In 1980, a bill came up to Congress to require the same treatment of officers by all of the services. The bill, the Defense Officers Personnel Management Act, or "DOPMA," forced the Navy to resurrect the one-star rank, beginning in 1982. Which the Navy did. The Captains who were promoted that year were duly promoted to the resurrected rank of Commodore; they wore one broad stripe on their dress blues.

And in short order, the whining came from the Commodores. The abbreviation for Commodore was "COMO." The Commodores complained that their mail ws being misrouted to the Officers Club (formally known as the "Commissioned Officers Mess, Open, or "COM,O") or to the base communications officer ("COMMO"). The biggest insult came when a four-star Army general, in discussing the replacement naval officer to be assigned to his staff, told the Navy to "send me a real admiral, not one of those weenie commodes."

The whining of the Commodores was written up in the Navy Times newspaper and, in the letters to follow, the junior officers and the enlisted men had a lot of fun at the expense of the Commodores. Most of the letter-writers more or less advised the Commodores to suck it up. One suggested that the ranks of Rear Admiral and Commodore be renamed to "Front Admiral" and "Rear Admiral," respectively, and that the proper halves of a horse costume be issued to those officers. Another published letter noted that Ensigns (pay grade O-1, also sometimes referred to as "enswines" or "butter bars" and equivalent in rank to an Army 2nd lieutenant) also wear a single stripe on their dress uniforms:

and suggested that Commodores be referred to as "Big Ensigns."

The Commodores were, of course, even less amused by the fact that now the rest of the Navy was poking fun at them. More than a couple Commodores had the experience of having junior officers both salute and laugh at them at the same time.

And so, after a decent interval of time, the rank of Commodore became the rank of Rear Admiral.

Wednesday, December 17, 2008

The Georgi Washingtonski Submarines

This is the first American ballistic missile nuclear submarine, the USS George Washington. She was commissioned in 1959 and test-fired a series of Polaris IRBMs in 1960. She then loaded out a full compliment of 16 missiles and began her patrols.

This is a Soviet Yankee-class SSBN. They carried sixteen missiles and went into service in 1968.

You might have noticed that the two submarines look almost identical.

This is no shit:

There is a reason why the two submarines look very much alike. In 1963, Revell Models produced a model of the USS George Washington class submarine. This is a reissue of those models.
As you can see, the models were cutaway and detailed on the interior. The original models had either a swing-away solid side or a clear plastic side.

Five years is about right to design, build and commission a submarine.

As the story goes, when the Revell model was first sent to the stores, the Soviet embassy in Washington sent their people out to buy every one they could find. The models were sent by diplomatic courier back to Moscow.

The Navy was not at all amused. An investigation was started to determine who had sold the plans for the George Washington class to Revell. That person was very quietly arrested, quietly tried, and sent to prison for a very long time.

I never heard the name of the man who supposedly sold the plans to Revell. Rumor had it that it was a fairly senior officer close to retirement, but that might have been an exagerration. When I heard the story, more than 20 years later, I was firmly assured that the man who sold the plans was still in prison and that the only way he was ever going to leave prison was in a wooden box.

Now maybe this is all just a sea-story. The individual who told it to me was rather intoxicated at the time. I wasn't exactly sober when I heard it. It could all be just an alcohol-inspired story dreamed up by two drunken naval officers in a bar at a BOQ or an O-Club. You won't find any mention of this in Wickipedia, Wickileaks or the Google (until now). It's a completely unsubstantiated story with no facts to back it up.

It could be true. It could just be a story. I make no claim either way.

Saturday, December 6, 2008

Propulsion Expediency

Steam powered warships are driven by two large turbines per shaft. Steam is admitted to the turbines by the throttle valve. Steam is coming from the main steam loop at 1,175 psi and 950 degrees. First, steam goes into the high-pressure turbine. This image shows two such turbines at a factory:

Steam is admitted into the center of the turbine and flows towards either end. Since as the steam flow drops in pressure as it expands through each stage of the turbine, the blades get bigger as you look towards either end of the turbine. The really large blades at the end are the astern elements used for backing down.

Then steam goes to the low-pressure turbine. The blades are of different design, designed to extract work from steam at (you guessed it) lower pressures. Steam that came out of the main steam loop at very high temperatures and pressures is exhausted into the main engine condenser at a near-perfect vacuum of 29" Hg and 110degF.

The turbines are connected to a set of double reduction gears:

The gears are a lot larger than this drawing implies. You can crawl into the oil sump of the gears. The big gear is the "bull gear," which is connected to the screw (propeller) shaft. They are double-helix gears to prevent gear lash and absorb the massive amount of horsepower being transmitted.

Reduction gears are very heavy, are very carefully machined and are very expensive. The access ports to the reduction gears are locked with the same type of locks used to secure weapons magazines. Lead anti-tamper seals are then affixed to each port. Both the sealing crimp and the lock keys are in the personal custody of the Chief Engineer, who must personally inspect the reduction gears prior to closing the access ports and then personally lock and seal the access ports.

During the Second World War, the companies that made steam turbines and reduction gears could not keep up with the number of warships being produced. The Navy decided that the use of steam turbines and reduction gears would be limited to fast destroyers, cruisers, battleships and carriers. The Casablanca class escort carriers used reciprocating steam engines, which why those carriers had a top speed of 20 knots. Many of the destroyer escorts were powered by large electric motors powered by diesel generators, in the same matter as a diesel locomotive.

The Navy went back to steam propulsion for destroyer escorts after World War II, with the exception of the four ships of the Claud Jones class, which were diesel-electric as a cost-saving measure, and which were gotten rid of by the Navy as soon as the Navy could justify doing so. Destroyer escorts were reclassified to frigates in 1975.

Steam ruled the destroyer escorts/frigates until 1974, when the last steam escort, USS Moinester (FF-1097), joined the Fleet. The Perry class, the only class of frigates built in the last thirty years, is powered by gas-turbines.

Wednesday, December 3, 2008

ASW Weapons; Part III

As I discussed in Part I and Part II, depth charges had several drawbacks. Chief among the drawbacks was the requirement that an escort prosecuting a submarine contact had to lose contact prior to launching her depth charges.

The Royal Navy had the lead on this problem, once again. They developed a "spigot mortar" that would launch a pattern of mortar bombs, each of which had a warhead of approximately 35lbs of high explosive. This became known as the Hedgehog. The mortar bombs were loaded onto rods; the bombs each had a cylindrical well along its center axis so that the bombs slid down and rested on the rods.

The early Hedgehog mounts were roll-compensated, but they could not be trained more than a few degrees to either side (moved from left to right) by tilting the mount, so the ship herself had to be aimed at the submarine. Later mounts were fully trainable. The mortar bombs themselves were launched in pairs at very short intervals, back to front, so that the bombs that fired at higher arcs were launched first (they had a longer flight time) and thus all of the mortar bombs would hit the water nearly simultaneously. The launchers' rods were set so that the bombs hit in a pattern, usually oval or circular, at a distance of 200 yards. The bombs would sink fairly rapidly.

Unlike depth charges, Hedgehog mortar bombs were contact weapons. Unless the submarine could hear the sound of the bombs being launched, she would not know that an attack run was underway, as escorts would also make non-firing runs to refine their targeting solutions. The time it took to reload the Hedgehog mount was usually less than it took to reposition for another firing run.

Hedgehog did have some of the same drawbacks as depth charges, in that the ships had quantities of high explosives on the weather decks. The launcher crews had to work topside, sometimes in far less than ideal conditions. At least one warship was lost when the stored Hedgehog bombs blew up because of faulty fuzing. They were also dumb weapons with a fairly long time between firing and impact, often close to half a minute or more, depending on the depth of the submarine.

Hedgehog nonetheless was a very lethal weapon when employed by a skilled crew. The USS England (DE-635) sank six Japanese submarines in 1944 in a period of 12 days.

Hedgehog was effective, but it still required that the escort close to the submarine's position in order to attack it. World War II sonars operated on sound frequencies around 14-30 KHz; many were "searchlight" sonars, such as the QGB sonar that transmitted a beam on one bearing; the sonar head was steered by the operator. The high frequency meant that the sonar head was small, it could be mounted on smallish ships, but because it was a searchlight system, searching for submarines was a matter of luck. The high frequency also limited the range.

Sonars developed into true search sonars that could transmit an omnidirectional beam. The QHB sonar transmitted an omnidirectional beam, but because it operated between 20 and 26 KHz, its range was limited. The early 1950s-vintage AN/SQS-23 sonar operated at 5 KHz, which greatly increased the detection range, but which also required a much larger sonar dome. The increased detection range of sonar sets like the SQS-23 meant that the escorts could track submarines far outside of the range of Hedgehog.

Clearly a longer range weapon was needed.