Saturday, August 11, 2012
|Paddlewheeler steam engine. Image from Twaintimes.|
|A "Parsons"-type steam turbine. |
Image from The Leander Project.
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
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.
Saturday, August 4, 2012
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.
Misunderstood Mariners: Joseph Hazelwood
The Skeptic's Guide To The Universe, Show #352 Show Notes
The Skeptic's Guide To The Universe, Show #349 Show Notes
Anchorage Daily News, Hazelwood Cleared On Three Counts
Wednesday, July 25, 2012
Saturday, July 21, 2012
|Photo of the 1882 transit, which revealed a precise distance for Venus's orbit.|
|Statue of Cook|
Saturday, June 16, 2012
Saturday, June 9, 2012
|William Bligh. 1814 portrait by Alexander Huey.|
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.