FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

42
Figure 15. The dispersion of the measured values is
again due substantially to the poor behavior of the
recording drum. The burning rate of the cordite
follows more or less a po.75-HO.7s iaw j" o r the Cpowder
an exponent of 0.53 best fits the results.
Several theoretical works were also carried out.
Figure 16 shows, for instance, the results of a theory
developed for the calculation of the pressure distribution
within the hole of a tubular charge for a
burning rate given by ap n . The coefficient £ is given
where 8 is the propellant density, r the hole radius
assumed constant, and T the gas temperature at
the burning surface. R and y have the conventional
meanings. The distance from the middle section of
the hole is indicated by s. The terminal points on
each curve correspond to choked conditions at the
two ends of the hole (this way my first contact with
the fundamental importance of Mach 1 even in the
presence of combustion phenomena). Choking ap-
FIGURE 14.—Front view of the pendulum test stand with
chamber.
c
2
(A
E
o
1.5
0
1.5
0.5
--
-
-
_ .1
B •
C *
0 *
6 •
>. •
1 •
LA
O
* /
/
•
— —
o
'
/b
—
— __ — —
SMITHSONIAN ANNALS OF FLIGHT
1
- -- .... —
'/
/
/ /
... 1 / /
/ • v' •
*
/* • •
i
/ <
rf>
• /
' #
o
• —
— ....
—
i
/
_..
.._.
y
""
/
.s
/
JRDITE
T
—
100 200
K
^
*
•
t i
A
1 1 1 1
P0LVERE C
- -
— —
... _.
- _
150
200
FIGURE 15.—Burning rates for cordite (top) and for C-powder.
pears for a certain charge length, beyond which no
steady solution to the problem exists and the pressure
must steadily rise in the hole. It seemed to me
at first that this was an important finding, and I
was disappointed when I calculated that for the
actual charges the maximum value of the abscissa
—