Science: Underground A-Bomb

Most atom bombs have been exploded well above the ground, either perched on a tower or dropped from an airplane.

Last week on its Nevada proving ground the AEC tried something different: it exploded an underground bomb, its first subsurface bomb since a little-publicized experiment in 1951.

The bomb, of unusually low energy yield because of the unusually high hazard, was buried in the earth at an undisclosed depth. When it exploded, it gave little light, heat or blast, but it raised into the air a many-fingered fountain of dirt or shattered rock. Most of this material was so heavy that it fell back immediately, spreading radioactivity for a considerable distance. A radioactive dust cloud hung in the air for 3½ hours, but did not move far from the crater.*

The AEC gave no more information, but some of the military problems of an underground atom bomb are fairly obvious. Nuclear explosives are getting cheaper and more plentiful, and they can perform with extra oomph many of the familiar military duties of chemical explosives. Items:

LAND MINES. An atomic minefield would be an effective obstacle to the movement of ground forces, would destroy men and vehicles near the explosion, might radioactivate and make impassable a wide strip of important territory.

DEMOLITION. The deeper an explosive, atomic or chemical, is buried under the surface, the more of its energy it imparts, to a shock wave passing through the earth; hence, atomic demolition bombs would offer an effective method of destroying deep dugouts, shelters or underground factories.

SABOTAGE. The so-called "satchel bombs" that may be planted by saboteurs, landing parties or paratroopers in a future war are likely to explode in basements, subway stations or other underground places. Knowledge of their effect on subsurface conduits and structures will be valuable to both civil and military authorities.

In maneuvers near Jolon, Calif, last week, the Army's 2nd Infantry Division set out to destroy an "enemy" missile-launching site whose concrete roof, 14 feet thick, had defied aerial bombing. In a hit-and-run raid, the G.I.s hypothetically turned the site into a radioactive crater.