Engineering 101: Steam Engines

Note: the model in the above video is actually of the CSS Virginia, formerly the Union ship Merrimac.

The earliest ships were powered by human muscle or wind, but early in the nineteenth century the Industrial Revolution brought steam power to the world's waterways. Steam has been superseded only within the last century by other types of power. There are still ships at work today that are powered by steam, from small replica paddlewheel riverboats to large cargo ships.

Paddlewheeler steam engine. Image from Twaintimes.

Steam engine systems, or "plants," have many advantages over other types of propulsion. They have relatively low vibration and noise, low weight, can be fit into small engine room spaces, and, despite their sometimes complicated looking appearance, are simple to operate and repair. On the other hand, steam engines tend to burn fuel at a higher rate than other engines. It was this drawback that forced the British Navy to set up coaling stations all over the world in the late nineteenth and early twentieth centuries. The need to maintain and protect these coaling stations was one of the reasons the Britain needed its empire in the first place, for better or worse.

In a basic steam engine, water is heated by burning coal or something else to create steam in a boiler. Sometimes the "something else" is nuclear energy. In modern steam engines the steam is heated up even more, or superheated, to give it even more energy.

A "Parsons"-type steam turbine.
Image from The Leander Project.

The steam is then directed through nozzles to concentrate it, and is then applied to a turbine, a disc or wheel with blades or paddles mounted on its edge. There are usually two turbines, one for both forward propulsion and astern.

The exact arrangement of pistons, arms, and gears varies after that, but eventually the steam's energy is used to turn the propeller shafts and thus the propellers themselves. Because modern steam turbines work best at speeds between 4000 and 7000 revolutions per minute, reduction gear must be used to reduced the speed of the shaft and propeller to more practical speeds

The steam is then cooled. Inevitably, some steam escapes the system during all this, so it is replaced with fresh liquid.

Steam engines require more planning and attention than diesel engines. The high temperatures involved (approaching 400 degrees Fahrenheit) and constant presence of water can dangerously stress materials of not handled correctly. It can take four hours or more between the time the order is given to get underway and the time the boiler is up to the needed temperature. The engine itself must be warmed up as well. Similar attention to detail must be observed when cooling down an engine.

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Mariner's In Review: The Skeptic's Guide To The Universe

One of my favorite podcasts is The Skeptic's Guide to the Universe (SGU). The podcast is produced by members of the New England Skeptical Society and hosted by Society president Steven Novella, a neurologist. Each week the show's panel of "rogues" addresses controversial claims, pseudoscience, and the paranormal, often focusing on the latest scientific discoveries or advances, fraud or just plain nonsense from the world of medicine. The SGU was one of the inspirations for this blog.


This year the SGU took on a couple of nautical issues, with varying success. An excellent report on the 100th anniversary of the sinking of the Titanic talked about some myths surrounding the lost liner:

• Although the Titanic struck an iceberg on April 14th, 1912, she did not actually sink until the 15th.
• The ship only had enough life boats for the current passengers; it had only a third of the number required for her total capacity
• Most of the deaths were from hypothermia, not drowning
• Much of the video we see of Titanic may actually be of her sister ship Olympic, which was launched the previous year
• The ship's owner, White Star Lines, didn't promote the idea that the vessel was "unsinkable," this was something that came up more after the sinking.

This last item turns out to be a myth about a myth. The SGU, to its credit, published an email from a listener the following week pointing out that, despite the claim that the "unsinkable" claim was untrue (as reported at, among other places, the myth-busting website Snopes.com), White Star had claimed in some promotional material that  "as far as it is possible to do, these two wonderful vessels [Titanic and Olympic] are designed to be unsinkable."


On the other hand, another podcast on the anniversary of the Exxon Valdez sinking led with one "rogue" commenting that "one drunk sea captain drives the boat into the shoals..." Another panelist interrupted, pointing out that this was a myth, but then saying "the captain was drunk but not at the helm." Captain Joseph Hazelwood was found not guilty of being under the influence at trial. Also, investigative journalist Greg Pallast, quoted in the very Wikipedia article the SGU uses as its source for its report, says "Forget the drunken skipper fable."


To be fair, such slip-ups are rare on the SGU. It's a worthwhile, entertaining podcast for anyone interested in honing their critical thinking skills.


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Andrea Doria

On July 25, 1956 the ocean liners Andrea Doria and Stockholm collided near Nantucket. Fifty-two passengers and crew members on the two vessels died and hundreds were injured. Eleven hours after the collision, the Andrea Doria sank to the bottom, where she remains today.

More than forty years after the Titanic sinking, the lessons learned in that earlier disaster were incorporated both into the design of the Andrea Doria, and in the response of her crew when the collision occurred. The collision made half the lifeboats on the Andrea Dorea unusable or inaccessible, but more than 1600 passengers and crew members were rescued and survived. Watertight compartments were properly secured, unlike in the Titanic incident, giving rescuers time to get most people to safety. Of the 52 dead, most had died in the initial collision.

There was no formal finding of fault. The two shipping companies that owned the Andrea Doria and Stockholm reached out of court settlements with each other and survivors, so no legal determination was ever made. An initial inquiry placed most of the blame on the officers of the Andrea Doria for improperly maneuvering their vessel in the minutes before the collision. Later investigations point to the Third Officer of the Stockholm and his misuse of a new technology called radar.

Fixation

In the study of human error, fixation is the tendency to focus on one or two inputs when things get stressful. Fixation has been a factor in industrial accidents like the one at Three-Mile Island nuclear plant, in aircraft crashes, and in maritime accidents. In the Andrea Doria incident, many believe the Stockholm’s Third Officer was so focused on his radar that he not only ignored other sources of information, he didn’t even notice the radar was set at a different scale then he believed it to be: the Andrea Doria was only five miles away; he thought she was twelve.

Following the collision, radar set designed was improved to make such mistakes less likely, and radar training requirements for bridge officers put into place.

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Capt. Cook & The Transit of Venus

Photo of the 1882 transit, which revealed a precise distance for Venus's orbit.

Last month’s transit of Venus across the face of the sun was largely an astronomical curiosity, but a similar transit in 1769 held great potential for expanding our knowledge of the universe. By comparing observations made from several points throughout the world, scientists hoped to measure the true size of the orbit of Venus, and thus the orbits of the other planets, and thus the size of the Solar System. Playing a key role was a captain named James Cook.

Statue of Cook
in Greenwich

In 1716, Edmond Halley (he of comet fame) published a paper explaining how a transit of Venus could be used to make the necessary calculations. Halley was more than the scientific father of the 1769 expedition, though. He also commanded an expedition in 1689 to measure compass variations. Halley was so bad a commander that the Royal Navy refused to allow a scientist to command one of its ships ever again. Thus Cook, a gifted mathematician and cartographer as well as a naval officer, was selected to lead the expedition.

A civilian collier, the Earl of Pembroke, was selected as the vessel for the expedition. Its shallow bottom and sturdy construction made it ideal for the voyage in ways a traditional warship would not be. The ship was overhauled, armed, and commissioned Endeavour. In August 1768 the expedition set out for Tahiti, where Cook and two scientists on board would make independent observations. It arrived the following April, and Cook made good use of the weeks leading up to the June 3 transit to build an observatory.

The results were disappointing,. The three sets of measurements taken at Tahiti did not match up within the margin of error, due to an optical phenomenon called the “black drop effect.”  Combined with measurements from more than a dozen other sites around the world, scientists were able to refine the estimates for the size of Venus’s orbit, but not with the degree of precision they had hoped for.

Cook’s voyage of exploration was not over yet. After the transit, he opened sealed orders instructing him to find and claim Terra Australis Incognita, a large southern continent of supposed great riches. He never found it and, indeed, did not believe it existed in the first place. The Endeavour did visit New Zealand and Australia and Cook was able to determine that the latter was a separate continent (it was previously believed to be part of New Guinea).

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Misunderstood Mariners: Joseph Hazelwood (Re-post)

When the twentieth anniversary of the Exxon Valdez oil spill came around [in 2009], a lot of the mythology surrounding the incident came around again, too. Everybody knows, for instance, that Capt. Joseph Hazelwood, captain of the tanker, was drunk at the time of the incident. Except, this was never proved. In his trial following the incident in Prince William Sound, Hazelwood was acquitted of being under the influence of alcohol at the time of the oil spill. In fact, he was acquitted of all felony charges, though he was convicted of a misdemeanor charge (negligent discharge of oil) and his master’s license was suspended under Coast Guard administrative rules.

Also untrue is the story that Hazelwood left the bridge under the supervision of an unlicensed mate. Third Mate Gregory Cousins was a licensed mate, what he lacked was the endorsement required by oil tanker watch officers to operate in Prince William Sound. Cousins was cleared of any charges related to the incident.

The Exxon Valdez may be the most famous oil spill, but it’s not even close to being the largest. Ten years before the incident in Alaska, the Atlantic Empress collided with the Aegean Captain off Trinidad and Tobago in the eastern Caribbean. The resulting spill dumped 287,000 metric tons (about 84 million gallons) into the sea, compared with the Exxon Valdez’s 37,000 metric tons (about 10.8 million gallons). The Exxon Valdez doesn’t even make the top ten in terms of size of spill.

On the other hand, none of the oil from the Atlantic Empress/Aegean Captain incident came ashore. The crude from the Exxon Valdez’s tanks is still being dug out of the beaches in Prince William Sound. The resulting damage to shore life, fisheries, tourism, and recreation has been an economic disaster for the Prince William Sound region, even leading to the bankruptcy of the Chugach native corporation.

The legal wrangling following the case is still in the courts. Less than a year ago the US Supreme Court threw out a $2.5 billion punitive damage award against Exxon. It had been whittled down from an initial $5 billion figure, in addition to nearly $300 million in actual damages, awarded in 1994.

As for Hazelwood, he paid a fine, did community service, and spent two decades as the butt of drunken captain jokes. Last month [March 2009] he apologized to the people of Alaska for the incident.

Misunderstood Mariners: William Bligh (Re-post)

William Bligh. 1814 portrait by Alexander Huey.

April 28 [2009] marked the 220th anniversary of the famous mutiny on the HMS Bounty. William Bligh, commander of that ill-fated expedition, has become synonymous with the image of a cruel captain, an image reinforced by popular fiction, especially movies.

Bligh was an officer under Capt. James Cook on that explorer’s third and final voyage, and served aboard vessels engaged in some of the most important naval battles of the Napoleonic Wars. Before taking command of the Bounty, he left the navy for a brief period to work in the merchant service. The Bounty’s log showed him to be, if anything, more sparing of cruel punishment than a lot of his fellow captain’s of the day. He also took from Cook a concern for the health of his crew, including making sure the food onboard exceeded the standards of the day and that the crew got daily exercise.

Bligh was also an early reformer of watch standing systems to combat crew fatigue, splitting his crew into three instead of two watches. It was this third watch that required an extra officer to be in charge of it, which led to Bligh recruiting Fletcher Christian for the 1789 voyage during which the mutiny occurred.

Bligh gets little credit for his forward thinking, although even popular accounts of the mutiny acknowledge Bligh’s skill in bringing a small boatload of loyalists 3600 nautical miles to safety with only one casualty. It’s probably inevitable that today Bligh is considered the bad guy in the mutiny, what with Christian being portrayed on film by heroic leading men Erroll Flynn, Clark Gable, and Marlon Brando. The fact is, the 1984 film The Bounty, with Mel Gibson as Christian and Anthony Hopkins as Bligh, is probably the most accurate, with many scenes lifted right from the Bounty’s log.

Merchant Mariners at D-Day

The Liberty ship Jeremiah O'Brien is the only surviving merchant ship from the D-Day armada.Photo by Mike Hofmann

Every man in this Allied command is quick to express his admiration for the loyalty, courage and fortitude of the officers and men of the Merchant Marine. When final victory is ours, there is no organization that will share its credit more deservedly than the Merchant Marine.-- Gen. Dwight D. Eisenhower

From the hot deserts of Africa to the icy waters north of Russia, American merchant mariners saw some of the most hazardous duty of World War II. When the long-awaited Allied invasion called D-Day finally came on June 6, 1944, merchant mariners were there, too.

Ships Without Ports. Some merchant ships began their preparations weeks before the actual invasion. Pulled off their regular runs, these ships cruised the waters around Britain waiting for a pre-arranged rendezvous to pick up cargo and men before heading to the French coast. These “ships without ports” were intentionally kept away from land to avoid enemy planes and ships spotting any concentration of vessels. Many of these vessels continued to shuttle between Britain and the European mainland up until the end of the war. In the first week alone, merchant hulls carried a large portion of the 326,000 troops and hundreds of thousands of tons of equipment and supplies necessary for the invasion.

Operation Mulberry. The night before the Normandy invasion, a force of civilian-crewed US Army tugs lead a fleet of concrete-hulled ships from the Isle of Wight and out into the English Channel. On the night of June 5, 1944, about the time that Allied paratroopers were landing behind German lines in Normandy and several hours after the largest invasion force in history had set out across the English Channel, a fleet of civilian-operated U.S. Army tugs pulled away from the Isle of Wight off the south coast of England. As they approached the French coast, the ships were intentionally sunk; creating breakwaters for huge artificial harbors that would serve as disembarkation points until a natural harbor could be liberated from the Germans. More than 1,800 merchant mariners manned the tugs and “blockships”.

High Merchant Marine Casualties. One in 26 American merchant mariners in World War II was killed in the line of duty, a ratio higher than any other branch of the military. Fourteen of those mariners died near Normandy, and are buried there alongside their comrades from the other services. But because they were not in the armed services, and despite Eisenhower’s praise, none were recognized as “veterans” for more than 40 years. In 1988, President Ronald Reagan signed the WWII Merchant Marine Service Act, providing merchant marine veterans with veterans’ benefits.

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