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Tuesday, December 30, 2014

Alice in Chains

So two posts ago was music from the 70s and 80s.  This is one of my favorite 90s bands, very melodic for an alt/metal band.  And of course there will only ever be one Layne Staley.  Sad story, that.

So I'm posting more music vids.  Because of course you installed the Ad Blocker for Youtube that I mentioned in the previous post!  Amirite?

I love this song, but couldn't find a live version, so we are stuck with the video and the studio cut :(

Monday, December 29, 2014

Must-have web browser addons, extensions, and what-have you

Like many people, I use the Intel/Windows arrangement, and use either Firefox or Chrome for a browser.  Of the many available extensions (or addons) that are available online, I have found a few that are really helpful, and I highly recommend them.  You can thank me later...

Adblock Plus:  This does what it says.  Blocks many ads from appearing on the pages you browse.

Ghostery:  This blocks cookies.  Install this, and it will show how many cookies it blocks on every web page.  You would be shocked how many people are tracking your every page view.  It's easy to allow a cookie if a site requires it for security reasons (logins, etc)

Adblock for Youtube:  Tired of seeing a commercial every time you just want to watch a youtube vid?  Try this one out!!!  

Script Block or NoScript:  These prevent Javascript attacks (which are easy and common) on your computer.  They also keep those annoying animated pop-up ads from coming up on your webpage.  If you need a javascript to run (perhaps for an animated weather map), you can temporarily or permanently allow java if you trust the website.  If you do use Java, keep it up to date!!!  If you have installed Ghostery and/or script blockers, the above link will need permissions to check your Java version.

Saturday, December 27, 2014

Permit class submarine variants

Permit class boats were the mainstay of the attack submarine fleet throughout the 1960s.  Here is what Wikipedia has to say about them:

Preceded by: Skipjack-class submarine
Succeeded by: Sturgeon-class submarine
Built: 1958–1967
In commission: 1961–1994
Completed: 14
Lost: 1
Retired: 13
General characteristics
Type: Fast attack submarine
Displacement: 3,750 long tons (3,810 t) surfaced, 4,300 long tons (4,369 t) submerged
Length: 278 ft 5 in (84.86 m)
Beam: 31 ft 7 in (9.63 m)
Draft: 25 ft 2 in (7.67 m)
Propulsion: 1 S5W PWR
2 steam turbines, 15,000 shp (11 MW) 1 shaft
Speed: 15 knots surfaced, 28 knots submerged
Range: Unlimited, except by food supplies
Test depth: 1,300 ft (400 m)
Complement: 112
Sensors and processing systems: BQQ-2 sonar (later BQQ-5)
Mark 113 Fire-control system (later Mark 117)
Periscopes Electronic warfare
• 4 × 21 in (533 mm) torpedo tubes amidships
• 12-18 × Mark 37 torpedoes, later replaced by Mark 48s
• 4-6 × UUM-44 SUBROC anti-submarine missiles
• 4 × UGM-84 Harpoon anti-ship missiles

Below, a typical Permit Class cutaway. (I have a .pdf of this image that is really clean, but don't know how to post that here)

Those were the Permit class ships.  There were two that were built a little different, and those were the Tullibee (SSN-597) and the Jack (SSN-605)

Jack was about 20 feet longer than a normal Permit Class ship, and incorporated a direct drive propulsion system, connected to dual counter-rotating screws on a concentric shaft.  So, an inner shaft would turn a small screw one direction and an outer shaft would turn a larger screw in the opposite direction.  I have heard that the shaft sealing system on this ship was a nightmare.

The purpose for having a direct drive running a pair of smaller screws is twofold:  Eliminate reduction gears (a source of noise) and reduce or eliminate cavitation at the screw.

Reduction gears are (surprise) a set of gears.  Steam turbines are most efficient at pretty high speeds. The screw of a warship is most efficient at low speeds.  The reduction gears take the high-rpm output of a steam turbine and reduce it to low-rpm speed for driving a ships' propellor.

Cavitation is the creation of vapor bubbles on the low-pressure side (trailing edge) of a propellor blade.  As the bubbles come loose from the moving blade, they collapse and cause a crackling noise that is easily detected by sonar.  When your goal is stealth rather than speed, cavitation is not acceptable.

Below, cavitation on the tips of the screw of a small motorboat.  Water is flowing left to right in the image.  Long-term cavitation will eventually erode the metal of the screw.

Smaller screws have less cavitation for a given RPM than large ones, because the blade tips will not be travelling as fast.  In theory, you can have two smaller screws with the same surface area, and run them at a higher speed than a single large screw, with less likelihood of cavitation.

Cavitation is is typically a problem at shallow depths, where there is not much water pressure to prevent forming vapor bubbles.  It is also a problem when the throttles are suddenly opened.  I liken it to spinning the tires on a car - it happens easier from a standstill than at 50 mph.  Not that I know anything at all about operating the throttles of a nuclear submarine ;)

Although counter-rotating props had previously produced impressive gains in speed on the experimental Albacore (AGSS-569), in this case the results were disappointing, and led to the abandonment of this approach.

Below, the screw arrangement of USS Jack

A typical submarine screw looks more like this.  Note that it has an odd number of blades, which helps to reduce harmonic and beat noise.

The USS Tullibee (SSN-597) was an interesting design.  Launched in 1961, she was the first to have a spherical bow-mounted sonar, and angled mid-ships torpedo tubes.  This layout would become standard on all later US submarines.  Her propulsion system was turbo-electric, meaning that she had main propulsion generators, and wound around her shaft was a large motor.  She was also the smallest nuclear attack submarine in the US fleet.  The overall details of this interesting power plant are not available, sadly.  I would be interested to learn more about her.

Tullibee underway.  She wasn't a fast ship - about 15 knots surfaced AND submerged.  Interesting hump behind the sail.

Profile of the one-of-a-kind USS Tullibee

More music!!! 70s, 80s

Just a few videos I stumbled upon recently.  Songs I still enjoy hearing...

Steely Dan, with one of the best guitar intros ever.

Tommy Tutone

Greg Kihn

The Pretenders


Fishbone - gets pretty manic at about 1:45

A little OC punk - Bad Religion


It's a ways past Pearl Harbor Day, but I have been thinking about that quite a bit.  I am not a great and well-read student of military or Navy history, but I know a little bit about it.  Although I am not a surface ship guy, I think battleships are pretty cool, and so I have read a fair bit about them.

Battleships were at the core of the first modern arms race in the early 20th century.  This battleship arms race began shortly before the outbreak of the first World War (and many historians believe helped to cause it).  But the reign of the battleship ended decisively with the attack on Pearl Harbor.

The idea of a large ship, carrying primarily big guns, goes back to the days of sail.  These were called "ships of the line", because the tactics of the day required bringing a line of several ships broadside to the enemy, and blasting them with the cannons mounted on the sides (a "broadside").

The tactical goal in those days was to "cross the enemy's T", to maneuver so as to have the enemy sailing straight toward the side of your ship.  The front of these vessels were poorly armed, having at most only deck-mounted hand cannons.  Therefore the firepower of a broadside would likely destroy the oncoming enemy ship, with little harm coming to the ship crossing in front of the other ships.

Below, two lines of warships ("Battle ships of the line") firing broadside volleys at one another.

In theory (and in practice), the larger ships with bigger and more cannons would typically sink smaller and less well-armed vessels.  The best defense for a smaller vessel was to rely on speed to escape, or maneuverability to avoid a broadside, if possible.

Below, a sail ship with three rows of cannons

The term "Battleship", while coined during the age of sail, became more common when steam-powered ironclads came onto the scene.  Ironclads were the ship-builder's response to the introduction of incendiary and explosive shells, which of course were highly destructive to wooden vessels.  Additionally, naval cannons were becoming more and more powerful, and later models could blast through several inches of oak, sending wooden shrapnel flying inboard to kill the crew.

This Union ironclad (USS Cairo) appears to have an armored stern wheel for propulsion.  This was a ship used on the Mississippi River during the US Civil War.  Most deep-water ironclads used the newly invented (and less vulnerable) underwater screw.  Note the angled sides, intended to cause incoming shells to deflect rather than penetrate.

Ironclads, and all battleships made up until the introduction of the HMS Dreadnought are considered "Pre-Dreadnought" designs.  The difference between an ironclad and a dreadnought-era battleship is the use of wood underneath the outer iron skin.  Typically 8-12 inches of wood would underlie 4-5 inches of iron or low-quality steel cladding on an ironclad warship.  Ironclads were not particularly fast, nor were they maneuverable.  They used piston steam engines rather than turbines for propulsion.

HMS Dreadnought was such a technological marvel that even decades after she had been scrapped, battleships were called "dreadnoughts".  Pretty impressive!

Below, the ship that started an arms race.

HMS Dreadnought made all warships that had come before obsolete.  She was very fast, because she was the first warship to use steam turbines for propulsion, and thus she could run or fight on her own terms.  Secondly, she was the first battleship to use only large (12 inch diameter) guns.

In the era of HMS Dreadnought, fire control consisted of spotters checking for splashes in the water where shells landed, and then advising the gun crews how to adjust their fire to get closer to the target - and maybe even hit it!  Ships that had a variety of gun sizes would often confuse the spotters, who might see a splash and not know which size of gun battery had fired it, making targeting confusing. On a ship with all large guns, this issue of confusing splashes from large and small guns out on the horizon did not arise.

However even during the heyday of this arms race, a fearful enemy hid just under the surface, and that was the submarine.  Every battleship captain's nightmare was that his gleaming, magnificent, treasury-busting ship-of-the-line would be sunk by a lowly torpedo.  If you look at the photo above, there are a series of poles running alongside the ship.  These would be extended when the ship was not in motion, and torpedo nets would be hung from them.  Not as invulnerable as they seemed, then.

Deploying torpedo nets.

With the launching of HMS Dreadnought, every major ocean-going country in the world immediately set out to build their own series of dreadnoughts, or modern battleships.




The United States (finally moving to steam turbine propulsion in 1922):


So the naval powers of the world, just before the Great War, embarked on the business of bankrupting their treasuries to build fleets of mighty battleships, just as the emerging technologies of air power and submarines were about to render them nearly useless.  And while naval strategists envisioned battles of all big-gun ships, during actual (as opposed to theoretical) wars, most of these ships succumbed to mines, torpedoes, or air attacks.

One of the few battles fought with large-gun capital ships was the Battle of Jutland, in 1916, off the coast of Denmark.  The larger British battle fleet engaged the German battle fleet over the course of two days, with the intent of sinking them or keeping them contained in their home ports.  The British lost twice as many men and tonnage than the Germans did, while causing the Germans to retreat home. Both sides claimed victory, although one could also say that both sides lost.

After the German fleet exploded three of the British Dreadnoughts, David Beatty (commander of the British Battlecruiser fleet)  turned to his flag captain, saying "Chatfield, there seems to be something wrong with our bloody ships today."  He was correct.  British designers and the Navy had traded the weight penalty of thick armor for greater speed and more guns; the British battleships were little more than very expensive floating bombs.

Even though the battleship had proven itself not terribly useful during the Great War, maritime nations continued to build them. There was even a sort of battleship arms control, with each nation allowed to build a certain tonnage of battleships and aircraft carriers.

Below, the German Battleship Bismarck during WW II.  After her rudder was damaged by torpedo bombers, the British battle fleet caught up to her.  She was then sunk by both enemy gunfire and intentional scuttling.

What finally did the battleship in though, was the eye-opening events of December 7,1941.  On that day six aircraft carriers sunk four battleships, damaged four more, and sunk or damaged several cruisers and destroyers, in addition to wreaking havoc on the airfield at Ford Island.

Below, Pearl Harbor at the beginning of the attack.  Ford Island (center) sits at the center of Pearl Harbor.  In this photo, the battleship West Virginia has just been hit by a torpedo.

The aftermath:

USS Nevada

USS Arizona

USS West Virginia

USS California (Neosho behind) get the idea...

No number of battleships could have accomplished the destruction that these six aircraft carriers did. Even if the Pearl Harbor battleships had been at sea, they could not even have gotten near enough to the aircraft carriers to harm them without being sunk by torpedo bombers first.  Battleships were quickly cast aside, in favor of aircraft carriers and submarines.

In between wars, battleships were gaudy, impressive, and threatening. During an actual shooting war, they were quite a bit less fearsome, spending their time bombarding tropical islands and escorting the more strategically valuable aircraft carriers.

Meanwhile during World War II, just 314 US submarines sank 1560 enemy ships, an impressive 55% of the total tonnage sunk during the war.

And so, suddenly after one Sunday in Hawaii, the future of naval warfare turned to submarines and aircraft carriers (and the many, many ships required to protect aircraft carriers).

Oddly enough, in spite of these lessons of history, US battleships gained a third lease on life toward the end of the cold war.  Four decommissioned battleships that had been built during WWII were recommissioned, and refitted with guided missiles and also with close-in weapon systems for missile defense. These ships were decomissioned the second time in the mid 1990s.

Iowa fires a broadside in 1982 for a firepower exhibition.  Exhibition... that kinda says it all.

Now as unimpressed as I am by the usefulness of battleships in actual battles.  I still think they are cool.  Extremely cool.  Just sayin... Check out that armor.  17 inches of steel!

USS Missouri ("Mighty Mo") after her 1980s refit with missiles and modern electronics.  Also, 33-35 knots is pretty darn fast!

In closing, I honestly believe that if the navies of the world were to engage in unrestricted warfare, *nothing* would be afloat on the surface within a week.  Only land-based aircraft and a handful of very advanced submarines would remain.

Thursday, December 11, 2014

Ballistic Missile Submarines

In case anyone is wondering why I never discuss Ballistic Missile Submarines:  I don't find their activities very interesting.  

Saturday, December 06, 2014

First-Generation US Nuclear Submarines

I find the introduction/implementation of new technologies very fascinating.  When these new technologies are first unleashed, there is a great deal of variety and plenty of experimentation going on before everyone falls into line and starts building very similar things.  The initial deployment of a new technology leads to some really interesting decisions and designs though.

This post is about the impact of nuclear power on submarine design, and on operation. Both were impacted in major ways, and it took several years for builders and sailors to sort things out.  In the meantime, the first generation nuclear boats were somewhat experimental.  There was quite a bit of variety in design and purpose for the new ships.

Until the advent of nuclear power, the best submarine in the world had been built by Germany during World War II.  This was the remarkable Type XXI U-Boat.  These submarines were built from 1943 to 1945, but although superior to any other submarine were plagued by quality control problems, and also by wartime bombing of the production factories.

These submarines incorporated massive storage batteries for enhanced underwater endurance, allowing them to stay submerged at 5 knots for 2-3 days straight.  Additionally, the Type XXI was equipped with a "Schnorkel" (the snorkel mast), which allowed it to remain submerged while running diesel generators to recharge the batteries.  Most importantly, they were fast and quiet, compared to their peers.

Below, Type XXI submarines moored at Bergen, Norway.  May 1945.

There is only one surviving Type XXI submarine, which was scuttled and then re-floated.  It is located at the German Maritime Museum in Bremerhaven.  Photo below.

The advanced technology developed for the Type XXI was not lost on anyone.  After World War II ended, the US Navy tested and Reverse-Engineered two German U-Boats, the U-2513 and U-3008.  As a result, several engineering goals were identified and used in the design of new US submarines.  Those goals were:

  1. Streamlining the hull
  2. Improving Battery Capacity
  3. Installing Snorkels
  4. Improving fire control systems
The Navy immediately wanted to begin building a brand new class of submarine with all the new features, but the Bureau of Ships felt that the plethora of WW II submarines could be modified enough to reach most of the goals.  Thus was born the GUPPY program, a series of modifications to improve US Tench, Balao, and Gato class WWII fleet boats, to make them perform more like a German Type XXI.

Below, a Tench Class Fleet Boat, the USS Toro.  The deck guns have not yet been installed for a war patrol.  Note the clutter on the deck and conning tower.

GUPPY mods included rounding the bow, removing the deck guns, and placing a fairing around the conning tower - which was afterwards called a "sail".  Snorkel masts were installed on ships that could accommodate them, and larger capacity batteries were installed.  The last GUPPY conversion was completed in 1963, by which time the WWII ships were no longer able to confront more modern enemy subs.

Below, the USS Tench with Guppy 1 Modification.  Rounded bow, very litle deck clutter.  Antennae and periscopes enclosed in a streamlined sail.

Meanwhile the Navy had managed to fund a few brand-new submarines, starting in 1946, with all of the features from their German Type XXI wish list.  These were the six Tang class submarines.  The Tang class were very capable ships:  The range without refueling was 10,000 miles.  They could run 15 knots surfaced, 18 knots submerged, and could dive to 700 ft.  Far better than anything a WWII fleet boat could do - including a Type XXI.

Nevertheless, all diesel-electric submarines, regardless of their sophistication, need to snorkel and burn diesel fuel to recharge their batteries.  During these periods of charging the batteries (which occur frequently), the submarine is much more exposed to detection than when operating deep. Additionally there is increased danger to a submarine spending long periods at periscope depth from collision with surface vessels, who will be unaware that a submarine is nearby.  The snorkel mast is made intentionally difficult to spot or to detect on radar.  These are the operating limits of a submarine that relies on internal combustion engines to function.

The USS Wahoo, a Tang-Class submarine.

And then suddenly the world changed, and many of the things submarine designers and sailors had always contended with were thrown out the window.

Below: The ship that changed everything - USS Nautilus at her launch on 21 January 1954...  On January 17, 1955 she was "Underway on nuclear power".

The new nuclear propulsion system did several things for ship designers.  No longer did they need to give top design priority to battery capacity, massive multiple diesel generator sets (for quickly charging the batteries), and setting aside space for large quantities of diesel fuel. The new propulsion system allowed engineers to explore the capabilities of a ship that was independent of internal combustion. And explore they did...

Below, the power plant that started it all.  The S1W prototype reactor in Idaho.  The water tank surrounding the reactor compartment is to absorb gamma radiation and to slow and absorb neutrons. The reactor is well shielded internally and unshielded (except for the pressure hull) exernally.

With all that history out of the way, we finally reached to the subject of this post!

USS Nautilus made a shakedown cruise four months after her first nuclear-powered underway.  Submerged the entire time, she ran 1300 miles from New London Connecticut, to San Juan, Puerto Rico, covering it in less than 90 hours.  This was the longest submerged cruise ever made by a submarine and the highest sustained speed ever recorded.

Nautilus' incredible speed and endurance rendered most of the Anti-Submarine warfare tactics that had been developed during World War II obsolete.  Radar and anti-submarine spotting aircraft were useless against a ship that no longer had to be near the surface and extend a snorkel mast to recharge the main storage batteries.  It could also quickly change position and depth.  A new and difficult adversary, which is difficult to detect and defeat, even today.

Nautilus (SSN-571) against New York backdrop.  SSN stands for Submersible Ship, Nuclear

On October 4, 1957, the Soviet Union placed the Sputnik satellite into orbit, shocking the entire nation.  The implicit message for the US was that the Soviets could rain down nuclear weapons on any US city at any time.

In August 1958, Nautilus was the first ship to reach the North Pole.  She passed through the Bering Strait, and dove under the ice for 2 days before reaching the pole, then continued on toward Greenland.  She did not break the ice during the trip - it was done entirely submerged.

The implicit message for the Soviet Union was that nuclear-powered ballistic missile subs (which were then under construction) could hide under the polar ice and rain down nuclear weapons on any Soviet city at any time.  And so went the cold war propaganda...

In fact, the hull and superstructure vibrated so badly that Nautilus sonar became useless at over 4 knots, so the lessons learned were incorporated into later designs.

While Nautilus was a ground-breaking and breathtaking ship, in many ways she was a simple old-school Tang-Class diesel submarine with a pressurized water reactor instead of diesel generators and massive storage batteries.  Let's look at another first-generation nuclear boat.

USS Seawolf (SSN-575) underway surfaced.

Seawolf was similar in many respects to the Nautilus.  She was a Tang-Class submarine with a nuclear reactor instead of the diesel-electric components.  She was commissioned in March of 1957. This ship used a very advanced reactor propulsion system that turned out to be overly complex and maintenance intensive.

The primary coolant system used on Seawolf was the S2G liquid-sodium cooled reactor.  By using liquid sodium, the reactor could be operated at higher temperatures and lower pressures.  Also because it carried more heat, steam could be superheated, raising efficiency further.  The system operated at only 15 psig, so it was quite light.  However...

The superheaters suffered from poor tubesheet welds and leaked steam into the liquid sodium coolant, a problem that caused formation of sodium hydroxide (a caustic) and hydrogen gas (explosive when mixed with air).  Any minor breakdown that might result in the sodium coolant dropping below the melting point would cause the system to freeze up, a maintenance nightmare.

In 1960 Seawolf was converted to an S2W reactor, and with that, the experiment ended!

The Skate (SSN-578) was the third nuclear-powered submarine launched by the US, and the lead ship of only four in that class.  This made the Skate class the first production run of nuclear submarines. All ships of this class used the S3W reactor.

Below, USS Skate surfaced at the north pole, August 1959.  Note the steam rising from the warm seawater discharge.

Skate was commissioned in December of 1957, and in August 1959, became the first submarine to surface at the north pole.  In August of 1962, Skate and Seadragon rendezvoused at the north pole and surfaced together.  They operated together for another week before parting ways.

The ships of this Class were Skate, Sargo, Seadragon and Swordfish.

Importantly for the new nuclear-powered submarines, a single prototype diesel-electric submarine had been testing the advantages of streamlining for optimum underwater performance, and this was the "Auxiliary Submarine" AGSS Albacore .  She was the result of wind-tunnel testing and revolutionized design by using a teardrop shaped hull, thereby minimizing drag.

Albacore at launch, December 1953  Submerged speed on an electric motor and batteries was a remarkable 33 knots.  Nuclear propulsion would arrive two years later.  The combination of a sleek hull and nuclear power would have to wait for the Skipjack class to arrive in 1959

The experimental teardrop-shaped Albacore begat a class of three Diesel-Electric boats called the Barbel Class, which also use a teardrop hull, and so look identical to modern nuclear submarines.

USS Blueback (SS-581) moored in Portland, Oregon 2004

The Skipjack class is what I would consider a late first-generation nuclear submarine.  It incorporates many features shared by current submarines, such as the teardrop shaped hull, an attack center inside the hull instead of a conning tower inside the sail, and a powerful S5W reactor that became the mainstay of the US navy for decades.

The reason I don't consider Skipjack class ships second generation is because while they were very fast, they weren't particularly quiet. Nor were they deep-diving.  The were very nice looking.  Did I mention they were fast?  One thing the Skipjack class accomplished was to standardize the attack submarine shape and layout.  In all the decades since Skipjacks, submarine fundamental design has not changed, although of course everything has improved a great deal.

USS Skipjack (SSN-585) trying to perform a high speed surface run.  Skipjack class boats could run at 15 knots surfaced, 33 knots submerged.

But was Skipjack the last first-generation class of nuclear submarine the US built?  Heck no!

The US submarine fleet had only one ship that had two reactors, and that was the USS Triton (SSRN-589).  This ship was a "radar picket submarine", meaning she was to stay out ahead of an aircraft carrier group and use radar to spot incoming threats before they got close to the carrier - essentially extending the radar detection range of the surface ship(s).  Apparently giving away the position of the most expensive submarine ever built by surfacing and sending out radar signals was OK, because that was how they were using her!  Different era, I guess...

USS Triton did not have a teardrop shaped hull, but she did have two reactors.  She achieved her speed through raw power.  Lacking a the teardrop shaped hull, she was faster surfaced (30+knots) than submerged (27+knots).

She isn't very pretty.  Triton launch, August 1958.

Profile shot.  Still not pretty.   ...but two S4G reactors!

The notion of a radar picket submarine ended with the introduction of carrier-based early-warning aircraft, and so Triton was converted into an attack submarine.  The Triton however, having two complete reactor and steam plants, was very reliable.  In 1960, on her shakedown cruise, she followed Magellan's course around the world - submerged the entire time.
She lasted about more 10 years in a navy composed of faster, quieter and cheaper to refuel ships.

USS Halibut (SSGN-587), the first and only US nuclear powered guided missile submarine.  Below, Halibut launching a Regulus guided nuclear missile.

Halibut steaming on the surface.

I discussed Halibut and her diesel-electric cousins in this post, so I won't go into it more, other than to say she was the last unusual design before everything became standardized.

Afterward were the Thresher/Permit class (14 boats), the Sturgeon Class (37 boats), and Los Angeles Class (62 boats).  The Thresher/Permit Class had one variant, and the Sturgeon Class had two variants.  I may discuss them in the future!  Interesting variations, those...

Blog Main Photo

It's time to change the main photo.  The aspen leaves have long since fallen!

Wednesday, December 03, 2014

What the hell is an SSXBT? Should I buy one off Ebay?

An SSXBT is a Submarine-Launched Expendable Bathythermograph!  Say that three times fast...

Now you probably can't wait to learn ALL about this arcane, but exciting technology.  First let's see if we can figure out what it does by its name.

Submarine-Launched.  Pretty self-explanatory there.
Expendable.  OK: you won't be getting it back after launching it into the ocean.
Bathythermograph. It records the temperature of the ocean.

So we have a device that takes the temperature of the ocean, apparently...  couldn't we just stick a thermometer into the water to figure that out?

Actually an SSXBT does a little bit more than take water temperature in a single place, which is what makes them pretty cool devices :)

The purpose of an SSXBT is to make a graph of the ocean temperature from the surface, all the way down to the maximum operating depth of the submarine that launched it.  The reason for wanting to know the ocean's temperature vs. depth profile is to better understand how sound will carry at various ocean depths, and set your ship's operating depth accordingly.

Colder ocean water is more dense and tends to carry sound further.  Interfaces between warmer and colder layers can reflect sound, keeping surface ships from hearing a submarine.  A cold channel between two warm layers may carry a submarine's sound a great deal further horizontally to another submarine than it would ordinarily go.  Understanding these conditions and using them tactically helps a submarine to remain hidden.

This cannot be emphasized enough:  Remaining undetected is critical for a submarine.  The only advantage (although it's a huge one) that a submarine has is stealth.  Once a submarine is detected, it is no more difficult to destroy than a surface ship.  Probably easier, because as floating targets, surface ships have many, many countermeasures against attack, while submarines do not.

...Which brings us back to our SSXBT and getting a profile of the ocean's temperature vs. depth.

Below is an image of an SSXBT, which is 3 inches in diameter and about 3 ft. long.  It is shaped like a small torpedo, and in fact, these are gently launched with pumped water through tiny 3" torpedo tubes (called "Signal Ejectors") out the top of the submarine.  A signal wire connects the SSXBT to a recorder on the ship (which of course has to be moving very slowly for this to work at all)

In the photo you will notice the SSXBT is made of two pieces.  The piece to the right is buoyant. After launch, the SSXBT floats to the surface, and then the right (buoyant) part separates.  The left part contains a weighted temperature probe with fins, which records water pressure (depth) and temperature as it sinks.  The data is relayed back to the ship via a signal wire, which is wound on a spool in the slotted section of the SSXBT. The buoyant part of the SSXBT scuttles itself after reaching the surface, so there is only brief evidence at the surface that a submarine lurks below.

Below is a drawing of an SSXBT, slightly more complicated than the one above.  This one has a "Lifting Body" (#306) that is buoyant, and helps prevent the signal wire from getting tangled up with the ship.

Just so you don't think I am blathering highly classified information all over the internet:

Here is a Lockheed-Martin advertisement with a drawing explaining how their SSXBT works.

Here is a declassified document (10-20 second .PDF download) explaining all about temperature gradients and how to read and troubleshoot your own SSXBT temperature chart!  Pretty cool stuff.

The photo of the SSXBT above was from someone who was selling it on Ebay.  Unfortunately the auction has already ended.  Truly a Christmas gift for the guy who has everything... I'd be willing to bet he doesn't have one of these :)

Tuesday, December 02, 2014

A dangerous tree

I took a week's vacation recently, and it wasn't much of a restful vacation.  More like catching up on chores - one big chore in particular.  Ever since moving here, I have been worried about one very large Ponderosa pine tree that was leaning toward the house.  I did not want to attempt to take the tree down myself because it was leaning the wrong direction, and I wasn't sure I could make it fall where I wanted it to.

Notice how the branches on this big leaning tree are the same size as some of the surrounding trees...

It took the tree service several weeks to give me a bid, then another month for them to actually come out and drop that tree (and a couple of others, one of which was leaning toward our power line).

As luck would have it, I had scheduled some time off about the time they got around to felling the big tree.  Good thing too; it was a pretty big job to clean it up.  The tree service would have hauled the tree off, but it would have cost 3x as much.  So I decided to do it myself.  ugh...  Of course it had to be the biggest, fullest tree on the property!

Happily, the tree fell away from the house, but it also blocked one of the driveway access roads.

Here I'm getting ready to start cutting off the limbs.

The first of four burn piles.  The tree is still blocking the driveway, but the lower half has been limbed.  I decided to save logs from the larger limbs.  Somebody will want them for firewood.

The driveway is open again!  Note the addition of more logs from the tree branches to the left.  There are still plenty of limbs remaining on the far side of the trunk.

The final burn pile.  The trunk is mostly sectioned.  There are quite a few more branch logs on the left.  After taking this photo, I stacked out the branch logs behind the house, but probably won't move the sections of the trunk until they dry out.  They are really heavy.

We had so much rain and a little snow, that I had to buy a weed burner to ignite the last pile.  I wasted a few gallons of gasoline and diesel, with no lasting fire to show for it.  This little sucker got it going after about 3 minutes of roaring and howling flame.  It's noisy, but it works.