Thursday, July 16, 2009

Trinity Site history

Courtesy of White Sands Missile Range

The first atomic bomb was tested at Trinity Site on July 16, 1945. Most people are familiar with this and the fact that the National Historic Landmark is on the north end of White Sands Missile Range. However, most are not familiar with the Trinity Site explosion weeks earlier on May 7, 1945.

At 5:30 a.m. on July 16, 1945 the world was ushered into the atomic age with the test of a plutonium-based bomb at Trinity Site.

The other Trinity explosive test was initially proposed in 1944 as a way to provide testers with a full dress rehearsal for the real thing and as a way to calibrate blast and shock sensors.

It was accomplished by building a 20-foot heavy wooden platform. On top of this soldiers placed 100 tons of high explosives (HE). The amount of HE and its height above the ground were scaled to simulate a four to five kiloton nuclear blast. (The July 16 test took place on a 100-foot tower but had a higher yield of 20 kilotons).

Many of the instrumentation sites used for the real test were operational for the 100-ton test. For instance, 11 quartz blast gauges were installed at ground level and nine records were obtained. Also, six geophones were used to measure earth motion and all gave satisfactory readings. In addition, all three Fastax cameras running at 1,000 frames per second from 800 yards away provided excellent photographic coverage.

Some of these instrumentation sites were constructed to accommodate the 100-ton test. For instance, the west 800-yard bunker has a view port facing the real ground zero and another facing more to the south where the 100-ton test was conducted.

The 100-ton test took place southeast of the real ground zero at a spot just east of the current Trinity Site parking lot.

The test was scheduled for 4 a.m. on May 7 but was delayed 37 minutes.

One obscure aspect of the test was the use of a radioactive slurry in the stack of HE. To measure the distribution of radioactive debris from the explosion, a radioactive slug from Hanford was dissolved and run into plastic tubing in the HE stack.

After the explosion the same methods were used to measure radiation on the ground that were planned for the July 16 test. For instance, a lead shielded tank drove into the small crater (about five feet deep and 30 feet in diameter) to take soil samples.

One thing learned from the test was the need for better roads to get people around quicker and reduce dust. By the time of the real test, more than 20 miles of the site’s roads were blacktopped.

Unlike the real test, the May 7 action went pretty much unnoticed. The flash of light was seen at the Alamogordo Bombing Range headquarters area by an observer who was told about it. Other than that, no one seems to have noticed the explosion.

This column is provided by White Sands Missile Range’s Public Affairs Office. For more information, call the office at (505) 678-1134.

Trinity Site Booklet

Text via The Morgue, embedded image via Nevada Tumbleweed