Fatherly in manner, with white hair and a full white beard, Needham had been described to me by a colleague as a between Santa “cross Claus and Eeyore,” an impression that belied his stature as a high wizard in the black art of explosives. With degrees in physics and astrophysics, he is an authority on modeling all variety of blast events and the dynamics of blast reflection, and he spoke with wistful nostalgia of the big booms” of high-ordnance tests of years “rumble past. A glance at his résumé calls attention to the diversity and sheer spookiness of blast-related issues: to fireball behavior,” “modifications explosive simulation of nuclear effects,” and and “high “Shock Vibration symposia.” Needham’s objective was to provide breachers with maps that would show which areas of a given type of structure are safest from reflected pressure. How a blast is reflected is determined not only by whether a space is square or rectangular, and the ceiling high or low, but also by where the wall studs lie, the number and placement of doors and windows, whether there are gaps or holes in the enclosure, whether there is furniture in the room. A shock wave bouncing off a rigid surface, whether of thin plaster or of steel, can be more powerful than the original wave. (Notoriously, the back-blast reflected off the ground at Hiroshima was more powerful than the actual explosion.) The corners of a room, where one might instinctively seek shelter, are particularly dangerous—as is being the third man in a line of breachers carrying protective shields, which, as it turns out, also reflect shock waves. A blast even reflects from within a soldier’s helmet to his head. Every feature in a landscape, every gesture a person makes, shapes a blast event. A terse conclusion of the original 2008 breacher injury study cited evidence” that recommended safe standoff distances required “clear
Fatherly in manner, with white hair and a full white beard, Needham had been described to me by a colleague as a “cross between Santa Claus and Eeyore,” an impression that belied his stature as a high wizard in the black art of explosives. With degrees in physics and astrophysics, he is an authority on modeling all variety of blast events and the dynamics of blast reflection, and he spoke with wistful nostalgia of the big “rumble booms” of high-ordnance tests of years past. A glance at his résumé calls attention to the diversity and sheer spookiness of blast-related issues: “modifications to fireball behavior,” “high explosive simulation of nuclear effects,” and “Shock and Vibration symposia.” Needham’s objective was to provide breachers with maps that would show which areas of a given type of structure are safest from reflected pressure. How a blast is reflected is determined not only by whether a space is square or rectangular, and the ceiling high or low, but also by where the wall studs lie, the number and placement of doors and windows, whether there are gaps or holes in the enclosure, whether there is furniture in the room. A shock wave bouncing off a rigid surface, whether of thin plaster or of steel, can be more powerful than the original wave. (Notoriously, the back-blast reflected off the ground at Hiroshima was more powerful than the actual explosion.) The corners of a room, where one might instinctively seek shelter, are particularly dangerous—as is being the third man in a line of breachers carrying protective shields, which, as it turns out, also reflect shock waves. A blast even reflects from within a soldier’s helmet to his head. Every feature in a landscape, every gesture a person makes, shapes a blast event. A terse conclusion of the original 2008 breacher injury study cited “clear evidence” that recommended safe standoff distances required
Blast-Force-National-Geographic.docx