SCIENTIFIC OFFENSIVE 



aged by fires. Of course, the A-Day bomb might be 

 (and indeed was) detonated at an miexpected position, 

 which would mean that some gages would find them- 

 selves nearer the detonation than had been expected 

 while others would be unexpectedly far away; some 

 gages, accordingly, would give readings so large as to 

 be off-scale and others would read zero. 



Other complications were that the target vessels, de- 

 spite their special moorings, were continually shifting 

 with the tide and wind. Pressure gages intended for 

 the exposed side of a target vessel might find them- 

 selves actually on the shielded side. Then there was 

 always the chance that the bomb itself would be ab- 

 normally weak and would produce only abnormally- 

 low pressures. 



IMPULSE 



To a physicist, impulse is no evanescent whim ; it is 

 a prosaic but useful measure of cumulative push. It 

 takes account of both the intensity of a push and 

 the duration of the push, and is thus a compound con- 

 cept. The intensity and the duration were both expected 

 to be very great in the Bikini explosions. Engineers 

 were undecided as to whether pressure, impulse, ve- 

 locity, or acceleration data would be most useful in ex- 

 plaining damage ; but all agreed that impulse was one 

 of the important quantities to be studied if explosions 



71 



