The explosion of a hydrogen bomb releases energy in three forms - blast, heat and nuclear radiation. Their relative importance depends on the distance of the bomb from the surface at the moment of explosion. Broadly speaking, the effects of blast and heat are comparatively local in all cases, whereas those of radiation may be very widespread.

2. Size of the Bomb -There is no technical limitation to the yield of this weapon. The analysis which follows is related throughout to a 1O-megaton ' bomb (10M.T). The highest yield achieved in the United States experiments to date is 30M.T. The area affected-by a bomb of this yield would be about 45 per cent. greater than in the case we are considering.

3. Blast and Heat - Blast and heat are more intense from an air burst than from a ground burst. - In dull weather damage from the heat wave is somewhat less extensive than in clear air. The blast and heat resulting from the explosion of a 1O-M.T. bomb would cause destruction on about the following scale:

  Air Burst 10 M.T at 20,000 feet (Radius in miles) Ground Burst 10M.T. (Radius in miles)
(a) Surface devastation to ordinary brick houses 7.5 5.5    
(b) Devastation to facilities and tunnels below ground Nil 0.33 mile in radius and depth    
(c)Major structural damage to brick houses 9 6.75    
(d) Surface damage by fire on ordinary day 8-12 5-9    

4. Radiation - The initial radiation occurring within a few seconds of detonation of a bomb, whether air burst or ground burst, is probably confined within a radius of three or four miles. The area thus affected is therefore in any case devastated by heat and blast.

The residual radiation occurring as an after-effect of the explosion varies very greatly in its effects, according to the point of burst. If the bomb bursts too high for the fire ball to reach ground level, the bulk of the radio-active materials are carried into suspension in the upper atmosphere. They are then so dispersed that they have no serious local effects when they eventually settle out.

But if the bomb bursts at or near the ground, quantities of much heavier radio-active particles are carried for a while by the winds that blow in differing directions at different levels. The pattern of precipitation is irregular, varying with the speed and direction of the air currents in the area, but a high proportion of the fall-out occurs from very high levels where the winds are more constant in direction and speed. This tends to elongate the area of contamination in the direction of the winds there prevailing.

5. Effects of Radiation on Life.- No medical means of curing or even curbing the effects of radiation on human beings are yet known. On human beings the effects are cumulative over a considerable period, becoming lethal when a certain dosage has been absorbed. In the Marshall Islands natives on an atoll 110 miles from the explosion received about one-third of the lethal dose: Americans who remained in huts 150 miles downwind received over a tenth of the lethal dose. Both these groups were 20 miles off the main line of fall-out.

Symptoms of radiation sickness may not show for some days, or even weeks. But about one-fifth of the lethal dose produces temporary sickness, with increasing disability as absorption increases beyond this point.

On animals the direct effects are similar. (In the Marshall Islands all animal life was extinguished on an atoll 110 miles from the explosion.)