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Now You Know, August 2023, Section 1 of 2

Updated: Aug 11

Project ELSIE

By Sara Gray, Technical Information Specialist, NSWCDD

As one of “the history people” for the Dahlgren base, I’ve been able to see some cool things Dahlgren does now and has done in the past. One that is in my top five has got to be the ELSIE

blocks. They are these huge concrete blocks in the woods on Tisdale Road, and I feel like Indiana Jones trekking back there to see them. Nature has slowly taken over the blocks, a couple have trees taking root in them, and some have formed small stalactites.

They’re all part of a testing facility for the ELSIE Project. After World War II, specifically around 1948, the Atomic Energy Commission (AEC) tasked the Bureau of Ordnance (BUORD), who tasked Dahlgren with this case. The idea was to develop a light case (Light Case…LC…Elsie. Get it?) for the atomic bomb. It had to be light enough to be carried by Navy carrier-launched aircraft but still ground-penetrating for tactical strikes on hardened underground targets. Overall breakdown of the responsibilities for this project looked something like this:

BUORD Overall Design and Development

Naval Gun Factory Gun Barrel

White Oak Safing, Arming, and Fuzing

Sandia National Laboratory Handling Equipment and Aircraft Saddle

AEC Uranium

Dahlgren Testing and Evaluation of Ballistics

Dahlgren was the obvious best choice for the actual testing of the case. It was the premier organization for gun and bomb testing, and the team there had proven itself with the development of a “sewer pipe” bomb. The ELSIE cases had to be tested by a simulated airdrop. Rather than send airplanes up to 50,000 feet every time they wanted to do a test, the Dahlgren team used a gun. The device had to accelerate but not exceed a certain G-load level, so several barrels were modified to fit this requirement. The general arrangement of the ELSIE test site can be found here. As the device went down the barrel, charges helped create a slow acceleration but still achieve the terminal velocity. One of the barrels modified for these tests actually still exists on base. It is currently stored on Main Range. The device was fired into the ELSIE blocks, concrete targets that are thirty or forty feet thick.

The actual lab work done on these cases was in the Butler Hut, a prefabricated, 40- by 100-

foot, windowless building specially acquired from the War Reserve. This building is none other than today’s Building 492. It was converted to the mailroom in 1956. It had a concrete vault to store the test bombs, and that is still around today as well. Only about ten to fifteen people worked in the building. The demanding project required about sixty hours a week, including weekends. Each person had to have a Q-level clearance, Q being the code word for clearance to work on the design and development of atomic weapons.

Besides clearance level, physical security for the project was high. The Butler Hut was surrounded by a tall chain-link fence with floodlights and was guarded around-the-clock by Marines. To gain access to the building, you had to see a Marine in one office to get the key to another building with the safe that held the key to the Butler Hut. You went to the building, honked your car horn, then stood in the headlights if it was dark. An armed Marine would come to you to check on your clearance. If the alarm was tripped, it would be a minute or less before guards surrounded the whole building. These Marines were frequently put to the test. An “invasion” team, usually from Indian Head, would come down the river by boat, land on shore, and attempt to hang a handkerchief on the fence and escape without notice.

About the Author

Sara Gray works for NSWC Dahlgren in the Technical Library & Research Center. She has undergraduate degrees in History and Historic Preservation and a master’s in Management.

A version of this article was previously published as an NSWCDD blog in October of 2017. Reused with permission.

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