There is an uncertainty in ecal.ine :ccaetion wich involves whether
the thermal yield is proporticnal t radi¢ bemical viet ® or proportional
Ir, this paper, the thecretical
to some lower power such as i of,
upper limit is assumed and this in itself may give values 2 ix 7
times higher than actually obtaired.
Tasr
is aleo an uncertainty
regarding the transmission of sir, because tna fireball rises raplidig
tc great heights. Near the surface cf th: water, traneniesicn is
quite low, but several hundred fee* above rhe water the trenmsmissicr.
increases merkedly.
The transmission ass..ed here is for very clear
air and considered reasonably cafe.
Although Liuge:ab is several
hundred feet, below tit horicar at Eniwetos, ne protection is afforded
from thermal radiation besause the firebal” rapidly g-iws tc @ diameter
many times this value.
A distinctive feature of the tinsrmal radiation on this explosion
will be the long time ecales involved, marly 10 tims that from «
& KT bomb.
It may be possible te see the Light minimum and ths
subseouent increase to maximum radiation, around 2 seconds. The
thermal radiation will persist for soma 30 saconds instead of the 3 seconds
fer conventional size weapons. Personnel sheuld be warned tnat it
is necessary to keep on the dark epcpzgkesa for muth lenger péricds off
time than for conventional size weapons.
3.2
TotaX Thermal Radiation vs Distance
Figure i0 shows the total thermal radiation in calories tin”
as a function of distence from ths bomb, These curves have heen
derived using the assumption that the tetal thermal radtatian wilt
represent 1/3 of the total yisid.
The dotted Lincs represent the
values of tota: thermal radiation which would be received
if ons
completely neglected absorption of thernai radiation by air.
The
full lines are based on a transmission of £5 per cent oer mile,,
and corresponds to a very clear atmoarhere
The fui lines are
considered reasonable estimates for strutiures near the ground.
The dotted lines are an exagrerated upper Limit, more e.prepriate
to high flying aircraft,
303
Temperatures of Surfates niposed to Thermal Radiatian.
Both the "affect of Atomic Weapons" and "Capabilitias of Atomic
Weapons" contain tables wiich give the critical energies in calories!
em’ for a number of common materials euch as wood, loth, rubber, and
piasties. The long duration cf thermal radiation of this weapon haa
the effect of lmreasing these critical energies by a facter of 3
above the critical energy required en a conventional size weapon.
Tne total thermal radiation occurs over lenger periods of time, this
permits correspondingly longer periods for heat to be conducted away
from the surface and into the interior of their radiated object.
substances which are not shown in such takes the average surface
temperature may be estimated roughiy from the following equation:
Fer