Evening star., 1961-02-20


| Various schemes to get
around this disadvantage have
been put forward. One was to
build a propellant mixing
plant at the launching site and
actually construct the rocket
right there. The idea looked
good at first, but involved
great expense and considerable
difficulty in quality control.
"Tootsie- Roll" Concept
Other engineers dreamed up
what has been called the
'Tootsie-roll" concept = seq
ments that could be piled one
atop another to make a super
rocket. These segments could
be built at a factory and
shipped one by one to the
launching site.
This was a better idea on
its face than the on-site man.
ufacturing concept, and is the
one favored in one form or an
other by most solid rocket de-
Signers today. But even the
TootSie-roll concept in its sim
plest form has a flaw in 1t. To
understand why, one must
know q little about how q solid
rocket is built.
Essentially such q rocket has
an outer casing which contains
the propellant, and q central
avity running. lengthwise
through the middle Of the
rocket. where actual burning
and thrust development take
place. The rocket is built by
pouring propellant into the
casing around a form, then al
lowing the propellant to hard
len before withdrawing the
form, which Is of the size and
shape of the burning cavity.
When rocket burning oc-
ours, it takes place all along
the central cavity. starting at
the middle and proceeding out
toward the casing. The hot
gases from burning pour out
one end Of the rocket through
nozzles. developing the thrust
that propels the rocket.
Cone Shape Employed
In the original TootSie-roll
concept Of very large rockets,
the diameter of the central
cavity was the same all along
the assembled rocket. Herein
lay the difficulty that plagued
big-rocket designers.
The trouble was that there
would always be more gas try
ing to escape close to the noz-
zle than there was farther up
the rockets central cavity.
Both theoretically and practi-
cally this presented design
problems.
The United Technology ap-
proach to the Tootsie-rch b con.
cept gets around the difficulty,
Mr.. Roberts asserts. by making
the rocket segments slightly
cone-shaped. Both the outside
diameter and the central
burning cavity are slightly big
ger at one end Of o segment
than at the other.
The conical concept has
been tried out at UTC's test
center under a program par
tally funded by the civilian
National Aeronautics and
Space Administration. Three
smallish test rockets develop
ing $4,000 pounds thrust have
been satisfactorily fired.
AS soon as some huge un-
derground curing ovens and
test stands, now virtually COM
pleted, are in working order,
UTC will start building some
super-rockets to see whether
the conical concept works as
well in full-scale practice as
on smaller scale.
Building SoIid-rocket COM
ponent 10 feet in diameter and
10 feet long. weighing perhaps
SO tons, involves a rare COM
bination Of laboratory and
factory methods. Mixing of
fuel and oxidizer ingredients
must be done with milligram
accuracy to insure high-qual-
Iity control. At the other ex-
treme. multi-ton weight-lifting
equipment is needed to man
handle the finished segments.
One Of the most impressive
items on the sprawling, 5000
acre plant near here is a cur
ing oven" "a feet in diameter
and so feet deep. Under condi-
tions Of partial vacuum and
heat carefully controlled to a
fraction Of a degree, rocket
segments bigger than any built
to date can be given much the
same treatment as rubber tires
undergo in their manufacture.
Testing Of such components,
which should develop upward
OF a half million pounds
thrust, will take place on spe-
cial test pads built into the
sides Of deep walled, blind
alley canyons. The rockets will
be tested upside down.; that
is. with their nozzleS pointing
upward. This will be done
partly for safety and partly to
obviate the need for cooling
water in these bone-dry noun
tains.
The lie Of the land Is such
that normally the rocket fir
ings will not be heard in
Greater San Jose. where about
two-thirds Of q million people
live. But when firings take
place during a period Of tenn
perature inversion, hold your
hats" will be the order Of the
day in the city below.
UTC had hoped originally
to situate its test center closer
to the corporate headquarters