Category Archives: Naval History

Torpedo Engine Technology for a Venus Space Probe?

I just finished reading an interesting article on a NASA proposal for a Venus space probe that uses power generation technology developed for a US Navy torpedo program back in the 1980s. Like many spacecraft, torpedoes need power generation systems that are small, generate massive power for a short period, and must be storable for years with the ability to turn on almost instantly with high reliability. Continue reading

 
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WW2 Submarine Endurance on Batteries

I have been reading the book The Bravest Man, a biography of the WW2 exploits of US Navy submarine commander Dick O'Kane. I have not formed an opinion on the book since I just started reading it, but the book does highlight the submerged maneuvering limitations imposed on a ww2 submarine because of its lead-acid battery-based power plant. The book's discussion made me curious about the operational characteristics of a Gato-class submarine when operating submerged on batteries. In this post, I will be examining the Gato-class submarine's run time versus speed plot (Figure 1). Continue reading

 
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The Bounty Mutiny and the Pitcairn Island Position Error

I liked reading the book Longitude by Dava Sobel and I also enjoyed the television movie version. I was recently doing some reading about the Bounty mutiny when I realized that the problem of measuring longitude played a role in that tale as well. The story of longitude is one of technology and obsession. While mariners had been able to measure their latitude accurately for centuries, measuring one's longitude required the development of accurate timepieces. Longitude is the story of the development of the marine chronometer. In essence, our modern GPS systems are extremely accurate clocks that provide the ultimate realization of the longitude goal. Continue reading

 
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Index/Instrument Error Correction in Sextant Measurements

Sextants make measurements that are subject to systematic errors – all instruments are subject to systematic errors. Alas, much of my career has been spent on calibrating out systematic instrument errors. Even with all my efforts, residual systematic errors remain. Continue reading

 
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Refraction Error Correction in Sextant Measurements

Refraction is probably the most difficult to understand of all the altitude observation corrections. It is also the most difficult to estimate accurately because it depends so strongly on atmospheric conditions, particularly the rate of temperature variation with altitude (see lapse rate). I will derive in this post a commonly used expression for the refraction correction required for a celestial object with an altitude greater than or equal to 15°. The accuracy of this expression degrades significantly for objects below 15°. Continue reading

 
Posted in Astronomy, Naval History, Navigation | 3 Comments

Correcting for Sextant Parallax Error

Navigators use the altitudes of solar system objects to assist them with determining their positions. The most commonly used solar system objects are the Sun, Moon, Venus, and Mars. There is a small error caused by the fact that navigators are making their sextant measurements from the surface of the ocean and not from the center of the Earth, which is the reference point used by nautical almanacs. Parallax has no practical significance when measuring the positions of stars because they are so far away relative to the radius of the Earth. Continue reading

 
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Correcting Sextant Measurements For Dip

I love to read stories of the sea and about the voyages made during the age of sail. I personally have never thought that I would have an opportunity for ocean sailing, but I recently began working with an engineer who is an avid sailor and teacher of sailing. He has sailed all over the world and recently trained another engineer in my group to sail. This newly trained sailor just returned from a trip to Bora Bora, which he found to be enjoyable and the sailing uneventful. Continue reading

 
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Ship's Course Correction for Cross-Current Rule of Thumb

I have lived most of my life in Minnesota, which is about as far away from the oceans as you can be in the United States. The idea of a planet mainly covered with water has always fascinated me. I will never forget the first time I saw an ocean (Pacific, Santa Monica, CA 1982). Fortunately, my work has provided me a bit of experience on ships and that experience was career changing − my early ocean experience involved laying fiber optic cable and that set the course of the rest of my career. Continue reading

 
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Sub Missile Launch Physical Model

I like it when instructors use physical models to illustrate how things work. I was watching this video on submarine design when I saw a physical model used to illustrate how a submarine launches a missile. The demonstration is excellent. … Continue reading

 
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Submarine Fuel Math

Introduction I just read an interesting article about an arctic environmental problem being presented by a Soviet-era nuclear submarine that had been scuttled back in 1982 (Figure 1). Apparently, scientists are now concerned that the submarine's reactor could leak dangerous … Continue reading

 
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