Merchant Marine Cadets Help Navy Knock The Rust Off Sextants

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September 10, 2016

PHILIPPINE SEA (Sept. 3, 2016) Midshipman 2nd Class Benjamin Sam, a student at the U.S. Merchant Marine Academy, fixes the ship’s position using a sextant aboard the Arleigh Burke-class guided-missile destroyer USS Benfold.  (U.S. Navy photo by Deven Leigh Ellis)

By Commander Justin Harts, USN (USS Benfold) According to the definitive book on marine navigation familiar to most naval officers – “The American Practical Navigator” – navigation began the first time humans had to find their way home using some object that caught their eye. Marine navigation was born shortly afterwards when humans observed that some objects could support their weight on water, and for the last 6,000 to 8,000 years, humans have been navigating on water by following the movement of stars in the night sky.

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So, you might be surprised that Navy Sailors are charting the moments of today’s most advanced warships using skills from the mid-1700s! There are as technology has become interwoven into our day-to-day lives, it’s important that we’re prepared to live without it if necessary. Several years ago, the Navy looked to our past to chart our future because basic techniques used to plot a ship’s position by observing the movement of the stars; planets, sun and moon are still as relevant to safe navigation at sea today as they were 200 years ago.

Celestial navigation was not formally taught to most naval officers during the last 15 years. Officer Candidate School did not teach it, Naval Reserve Officers Training Corps stopped teaching it in 2000, and the Naval Academy removed it from its curriculum in 2006. However, based on direction from former Chief of Naval Operations Adm. Jonathan Greenert, celestial navigation has been reinstated into the navigation curriculum and is a requirement in the Officer Professional Core Competencies Manual at USNA. Being proficient at celestial navigation provides added redundancy to ensure that our ships can sail safely in any contingency. The academy resumed formal classroom instruction during the summer session of 2015, and the class of 2017 will be the first in many years to graduate with a basic knowledge of celestial navigation.

USMMA Cadet taking a Sun Line Sight with a sextant
Midshipman 2nd Class McKenna Henyon, a student at the U.S. Merchant Marine Academy, takes a sunline measurement aboard the Arleigh Burke-class guided-missile destroyer USS Benfold (DDG 65). Photo by Deven Leigh Ellis, USN)

However, there is one group who never gave up their sextants – midshipmen at the U.S. Merchant Marine Academy in Kings Point, New York. These midshipmen are still required to master the art of CELNAV in preparation to become officers in the Merchant Marine and Strategic Sealift Officers in the Navy.

When I learned Benfold would be sponsoring four midshipmen from Kings Point for our next patrol, celestial navigation was one of the first things I thought about. I’m pretty rusty, and while I talked a big game, I really wasn’t up to teaching the subject. So I challenged the mids to partner with Benfold’s quartermasters to see if they could successfully navigate the ship from Yokosuka, Japan, to Guam for Exercise Valiant Shield without using GPS or the ship’s inertial navigation systems. I sort-of expected some excuses, but they set to it like it was no big deal, fixing the ship’s position to within five nautical miles of our GPS solution on the first night using Mars and several stars. The next morning, they were on the bridge well before sunrise to plot morning stars, updating their position from the previous evening.

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During the day’s work in navigation, Benfold bridge teams took morning sunlines to predict the ship’s position at noon and then calculated our latitude by observing the sun’s apogee at local apparent noon. They determined the ship’s laser ring gyro error by observing amplitudes and azimuths of the sun, moon and planets, determined our latitude by observing Polaris, and fixed our position by observing stars at sunrise and sunset.

By the end of the voyage, midshipmen and quartermasters were engaged in daily shootouts, competing for accuracy using nothing but a sextant, a stopwatch and some books originally written in the early 1800s.

It’s a big ocean and Guam is a pretty small target in relative terms. At roughly 33 miles long and 12 miles wide, Guam sits in the middle of an ocean that encompasses 60 million square miles, but they found it! All total, the voyage was 1,341 miles and the maximum cross track error they encountered was four miles – close enough to sight the island visually. Not bad considering the only modern technology they were allowed to use was a watch and pocket calculator.

Like any skill, practice makes perfect. Benfold, with the help of some midshipmen, is learning that what’s ‘old’ is new again and plotted its course successfully by following the movement of stars in the night sky. As the ship and crew prepare for Exercise Valiant Shield 2016, I am excited for the opportunity to continue practicing this nearly lost art and to mix some of the most high-tech tactics with some of the most ancient techniques to increase our combat edge as Benfold looks to the past to chart our future.

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