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DID YOU KNOW, August 2023

Updated: Sep 18, 2023

August 7th - The Sewer Pipe Bomb/Thin Man/Little Boy

The first segment of our featured article for the month, “Project ELSIE” by Sara Gray (, mentions the development of a “sewer pipe” bomb at Dahlgren. But what exactly was it?

Brigadier General Leslie Groves’ Manhattan Project scientists focused on the “Thin Man” (later called “Little Boy”) design for an atomic bomb through 1943. Working at Dahlgren Naval Proving Ground, Captain William “Deak” Parsons and Dr. Norman Ramsey created models to test the design’s ballistic qualities. Colleagues who saw these models, which consisted of long pieces of 14-inch pipe welded between 500-pound bombs that had been cut in half, referred to them as “sewer pipe” bombs.

Before the first drop tests on August 13, 1943, Parsons and Ramsey filled the models with sand and debris. To allow them to adjust the center of gravity, they had lead billets made which were so heavy that their weight “squashed down halfway” the tires of the car that carried them to Dahlgren and kept the car from going above twenty mph. Although the first tests were not successful, adjustments to the model did result in a satisfactory design for ballistic performance.

Caption: Nuclear weapon of the “Little Boy” type. (NH 123862 courtesy of the Naval History and Heritage Command.)

August 14th - Manhattan Project's Difficult Legacy

On August 6, 1945, Captain William “Deak” Parsons, former Dahlgren experimental officer, served as weaponeer on the Enola Gay, arming “Little Boy” on the way to Hiroshima, Japan. Three days later, Commander Frederick Ashworth, former Dahlgren aviator, armed “Fat Man” on the way to Nagasaki.

As quoted on Wikipedia, “World War II was the deadliest military conflict in history. An estimated total of 70-85 million people perished, or about 3% of the 2.3 billion (est.) people on Earth in 1940.” Many saw the use of atomic weapons as a way to end the war as quickly as possible. Between the two bombs, taking into account the initial explosion and the resulting effects of the radiation, as many as 300,000 people died.

The men and women involved in the creation and use of these bombs took what they were doing very seriously. Nobody made the decision to use them lightly but, rather, debated the matter intensely.

While we appreciate the groundbreaking theoretical and technical achievements involved in the making of these atomic weapons, we mourn for those who suffered from their direct and indirect effects, whether they were in Africa where the uranium was mined, the United States where the materials were assembled and tested, or in Japan where the bombs were used.

Is there a silver lining? Books like Life Atomic: A History of Radioisotopes in Science and Medicine by Angela N. H. Creager explore how insight gained through atomic research led to breakthroughs in medicine and biology. We also have a better understanding of the interconnectedness of the elements in our environment. So the Manhattan Project’s legacy is more extensive than we might initially realize.

This is a good reminder that history is never as cut and dry as we might like to consider it. It is our job to study the past – the good and the bad, the comfortable and the uncomfortable – and to pay attention to the lessons learned – the good and the bad, the comfortable and the uncomfortable – as we move forward in our own times. War has always accelerated technology progress, creating major leaps forward without knowing unintended consequences both good and bad. The hope is humanity will use the past to create a better future.

Image: Nuclear weapon of the “Fat Man” type, the kind detonated over Nagasaki, Japan. (NH 123863 courtesy of the Naval History and Heritage Command.)

August 21st - Capt. Hedrick Announced V-J Day to Dahlgren Personnel

In the August 18, 1945, edition of the “News Sheet,” Captain David Hedrick officially announced V-J Day (the end of WWII) to Dahlgren’s military and civilian personnel:

You men and women, civilian and service personnel of the Naval Proving Ground, may

well take pride in your contribution to the defeat of the enemies in Europe and to the

surrender of Japan. The Navy is the Nation’s first line of defense, and the weapons of war

which have established the Navy’s superiority have been tested and proved by you.

Through your efforts the guns and munitions, and all that go to make up naval ordnance,

have been placed on ships and landing crafts with full assurance that they would stand the

heat and stress of battle. Your work at the batteries and in the shops of this station,

through cold-wintry weather and during the hot summer months, has made this

assurance. The importance of the part the proving ground has had in the war effort has

made it a major activity in the Naval establishment of the United States.

Image: Captain David Hedrick, 1941. (NH 49106 courtesy of the Naval History and Heritage Command.)

August 28th - USS Pennsylvania Link to Project ELSIE

In this month’s featured historical article, “Project ELSIE” by Sara Gray, she mentioned that several gun barrels were modified to do testing on the ELSIE cases.

One of those barrels had been on the USS Pennsylvania (BB-38) during the Japanese attack on Pearl Harbor on December 7, 1941. The drydock she was in at the time protected her from torpedoes, and she suffered relatively minor damage.

Related to the mention of radiation in our August 14th “Did You Know” fact, the USS Pennsylvania ended her Navy career by serving target duty during the July 1946 atomic bomb tests at Bikini Atoll. Contaminated with radioactive fallout, she was studied for the next year and a half and then scuttled in deep water.

Do you want to read the materials referenced above? Check out the appropriate links at:

To find out more about the Dahlgren Heritage Museum – and local history – stop by Wednesday through Sunday, 10 a.m. to 4 p.m.


[Left] View of the USS Pennsylvania’s forward 14/45 guns circa early 1930s. (NH 50758 courtesy of the Naval History and Heritage Command.)

[Right] USS Pennsylvania drydocked in an Advanced Base Sectional Dock (ABSD) at the Pacific, circa 1944. (U.S. Navy Photo)
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