since the actual temperatures in the fireball interior can only be surmised;
the surface is certainly much cooler, and we can observe only the surface.
The published data may be found in the literature.¢»3,4,> These data are
summarized in the curves given in Figure 1. Although there is some
scatter to the data, it is clear that gamma goes through a broad minimum,
and is of the order 1.2.
|
Thus Taylor's theoretical scaling constant K =
1.740 differs from the experimental value K = 1.709 by only 2 percent, and
we use the experimental number in evaluating all USAEC test shots.
The
energetic equation is, then,
E = 1.709p R°t~* (ergs)
.
(2)
In practice the USAEC has measured the fireball diameter, rather than the
radius, and has used a different set of units throughout,
Expressing Din
meters, t in milliseconds, p, in grams/liter, and E in kilotons, relation
(2) may be rewritten:
5
E = 1.272 x 1078pD°t™
kilotons
(3)
where we use the conversion factor, one kiloton = 4.2 x 1019 ergs.
This conversion factor, although somewhat arbitrary, has been used
consistently.
os. G. Logan and C. E, Treanor, Tables of Thermodynamic Properties of
Air from 3,000°to 10,000°K, Cornell Aeronautical Lab Report BE-1007-A3,
January 1957.
3
J.O. Hirschfelder and C. F. Curtiss, Thermodynamic Properties of
Air, II, Naval Research Lab Report CM-472, University of Wisconsin,
June 1948.
43, Hilsenrath and C. W. Beckett, Tables of Thermodynamic Properties
of Argon-Free Air to 15,000°K, Arnold Engineering Development Center
Report AEDC-TN-56-12 (ASTIA AD-98974).
° Thermodynamic Properties of Highly lonized Air, AFSWC-TR-56-35
(ASTIA AD-96303), Kirtland Air Force Base, New Mexico.
6