FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

NUMBER 10 111
rocket combustion chambers have been developed
elsewhere, but I should like to mention at this point
my former colleague Meyer-Hartwig who devoted
intensive studies to these topics.
There are three significant effects which reduce
the surface temperature: heat absorption by passing
the cooling liquid through the porous wall, heat
absorption by the evaporation of the cooling liquid,
and the additional boundary layer consisting of the
mass addition of cooling liquid at the surface of the
wall. A temperature profile for the cooling of a solid
and a porous wall is represented in Figure 14. At a
gas temperature of 1100°C and a velocity of 600-
700 m/s the surface temperature can be reduced to
100°C applying 0.04 g/(s-cm 2 ) specific mass flow
rate (Figure 15).
Figure 16 shows the application of porous material
in a rocket nozzle. At a chamber pressure of
36 kp/cm 2 and a gas temperature of about 2500 °K,
0.6 g/(scm 2 ) of cooling liquid were fed through the
nozzle wall, which amounts to less than 2 percent of
the main mass flow rate of the combustion chamber.
The porous materials used for the research in sweatcooling
were made from powdered steel and copper.
The strength-to-weight ratio of this material was
almost equal to that of the compact material.
Boundary-layer
Additional
Boundary-layer
Solid Wall Porous Wall
.Cooling
FIGURE 14.—Temperature profiles for solid and porous walls.
WOO
°c
800
600
COO
200
\
\
\
1 \
I N s>
-" - —
02 g/cm 2 sec 01
k
FIGURE 15.—Surface temperature as a function of specific
coolant flow rate.
Figure 17 shows different test bars, orifices, and
rocket nozzles developed in our laboratories. The
development of porous materials for sweat-cooling
was started with nonmetallic ceramics, but in connection
with steel constructions a lot of difficulties
arose due to differing rates of thermal expansion.
Pressure-gas
Cooling -agent
Jacket
1 Cooling-distributer
Two -part tiller
FIGURE 16.—Sweat-cooled material nozzle.
Sweating-nozzle