FINAL REPORT ON PHASE II FOUR-INCH ROCKET CONTRACT NO. RD-45 RESEARCH ORDER NO. 13

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03624A000900010079-5
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 18
• Document Creation Date: December 23, 2016
• Document Release Date: August 7, 2013
• Sequence Number: 79
• Publication Date: September 25, 1956
• Content Type: REPORT

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September 25, 1956
MAY
DOC 7 ci )0/ DATE 29 ;9B? BY D4323
ORIG COMP C-3 -A0 OPI TYPE 417_3
ORIG CLASS -5 PAGES RV CL;z5S
JUST '7/7-- NEXT REV .'"?e?-(-) AM: NH 10-2
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FINAL REPORT
ON
PHASE II
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FOUR-INCH ROCKET
L_ _J
1210-E-1
Contract No. RD-45
Research Order No. 13
--tt-t CONFIDENTIAL
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TABLE OF CONTENTS
I. INTRODUCTION 1
II. STATIC TESTING 2
III. FLIGHT TESTING 3
A. SPIN STABILIZED ROCKETS 3
B. FIN STABILIZED ROCKETS 6
IV. SUMMARY 9
V. FINANCIAL STATEMENT. 10
VI. PLATES ? ? 11/16
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SHRET
INTRODUCTION
The transfer of the Four-Inch Rocket project
also marked
the transition from Phase I to Phase II.
At the close of Phase I, the internal ballistics study was
established and the basic component material study was
well advanced. Immediately following the transfer, the
spin stabilized rocket was redesigned in an effort to
eliminate failures due to limitations in the strength
of plastic materials.
New personnel were acquainted with the past history of the
project and trained in rocket fundamentals and the fabri-
cation of plastic parts.
A proposed flight test area was investigated at another
site. The general conclusion of the groups involved was
that while it was possible to use the area, it was rather
unsuitable from the standpoint of safety and the extensive
precautions required such as road blocks and aerial guards.
An inspection trip was made to another area situated at
This seemed sufficiently suitable to all
concerned and plans were made for its use.
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II. STATIC TESTING
To facilitate static testing of rocket motors, a reinforced
concrete slab was poured in the test area and a braced steel
test stand was constructed and erected on the slab (as may
be seen in Plate 1). A 300 foot cable connected the equip-
ment at the test stand to an oscilloscope which was especial-
ly modified for use on the project. Following the transfer
of the propellant powder to
static tests were
made on a single tube steel motor to test the instrumenta-
tion and familiarize personnel with firing procedures.
During this period, the multitube motor was completely
redesigned and many static tests were made to study the
strength of construction and internal ballistics of a
single plastic tube motor which was an integral part of
the design. After this method of tube construction had
been proven, many tests were made of the new three tube
design, testing the strength of head block materials.
Additional static testing was done to develop the best
possible bonding resin for use in bonding the nozzle and
plug inside the motor tube. All of the components of the
proposed model were successfully static tested and con-
struction was started on flight test models.
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SECRET
III III. FLIGHT TESTING
As stated in Section 12 an inspection of a flight test area
at another site indicated that it was, on the whole, un-
suitable for our purposes. An area was selected at
that was satisfactory to all concerned. This area is
approximately 300 by 4500 feet, fairly clear and level.
Recently, approval was given to extend this area to ap-
proximately 7000 feet by conducting flight tests which
would cross a public road that would require intermittent
blocking.
A. Spin Stabilized Rockets
A spinner type rocket attains its stability by spinning
longitudinally at a rate of approximately 600 rpm.
One method of achieving this spin is to divert a portion
of the rearward thrust so that its line of action
misses the center of gravity, thus producing a torque.
In the case of the multi-tube rocket, this was done by
canting each nozzle at an angle to its lever arm, some-
what as in the fashion of a pinwheel. In the redesigned
model of this rocket an attempt was made to obviate the
failures of previous models by making the tube assembly
able to withstand the pressure within itself thus
reducing the stress in the interconnecting head section.
Basically, the design consisted of a four-inch diameter
motor with three or six tubes, each employing a canted
nozzle. Each tube was plugged at the head end and a
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connecting hole was bored in the plug through the side
wall of the tube, as illustrated in Plate 2. The tubes
were oriented in the motor head so that the bored holes
connected to a central cavity and were bonded in place
with epoxy resin. The pressure in the central cavity
was contained by a hollowed plug sealed with 0-rings, as
may be seen in Plate 31 along with a bored head into
which has been laminated a central reinforced care. The
payload compartment was a length of spiral wound paper
tubing, capped by a polyester ogive, which may be seen
in Plate 4 as the completely assembled rocket.
This motor possesses several advantages from a design
standpoint, since the head can be made smaller and
lighter. This would require less fuel and smaller
stresses in takeoff. The main benefits of the design
are that the principle effect of the pressure is con-
fined within the tube and, in addition, since the pres-
surized area of the head is quite small, the stresses
within the head are greatly reduced. By the utilization
of either three or six tubes, the attainment of two
ranges is facilitated.
Considerable time and effort was spent on the develop-
ment of this type rocket, since it was compact and
permitted easy utilization of the proposed time delay.
It was felt by all concerned, that it was desirable to
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develop this design if at all possible because of its
many advantages. In practice, however, the factors that
made the design suitable from a pressure standpoint were
undesirable due to reetriction of gas flow. In crder
to reduce the pressurized areas in the head, the cross-
port size had been reduced to a 3/8" drilled hole, with
the result that pressure equalization through this port
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did not take place rapidly enough, g ith resultant
instability in flight. The crossport area was increased
considerably through evolution of several revised head
blocks, such as shown in Plate 3, and although increased
stability resulted, the flights were still not considered
satisfactory. Another rocket was constructed with an
aluminum head with crossports considerably larger than
before, which materially increased its stability. The
area of these ports, however, was too large to be made
safely in plastic. Thus, it became increasingly evident
that the problem of sufficient pressure equalization
area versus the limited strength of plastics was incapable
of solution within the project's limitations in either
time or money.
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SttRII
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B. Fin Stabilized Rockets
As mentioned earlier, although the problems involved in
a spinner rocket are not incapable of solution, the re-
maining four months allotted to Phase II in the project
were insufficient to produce another new design concept
which could overcome the limitations of the two previous
designs. The design of a finned rocket, however, is
much simpler in that fewer components are required and
the operating principles are more fully developed, especially
in the case of the low powered miniature rocket in which
we are interested. Basically, the stability of finned
rockets is achieved by providing sufficient lateral fin
area as rearward as possible from the center of gravity,
a task much easier than providing a balanced spin rate.
The biggest advantage from the standpoint of time and
money is that the internal gas pressure is completely
contained in a single motor tube whose operation had been
repeatedly demonstrated previously.
The design consists of a finned motor tube which is glued
into the base socket of the cargo compartment. To pro-
vide sufficient stability a delta fin was evolved whose
over-all width was three times that of the rocket body.
A launcher was designed with four internal ribs, the
rocket fins lying between the ribs and the rocket body
guiding on the ribs or rails. Success was met almost
immediately, with several 1,000 meter shot groups landing
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within circles 70 - 80 meters in diameter. The equivalent
payload capacity of this model was 22 ounces, simulated
by an appropriately shaped block of wood, as may be seen
in Plate 5.
During this time, another model was evolved whose design
was better suited to production. Since more propellant
would be required for a longer range, the motor tube size
was increased to accomodate three sticks of propellant
side by side. By this means, the length of a single
stick of propellant can be shortened. A long length
of propellant tends to split due to internal pressure
build up. The fins were made of a smoother material to
provide less drag. The head or payload section consisted
of a 9" length of 3" 0.D. paper tubing capped by an ogive
at the front and a base cap at the rear, which also had
a recess to receive the motor tube. The payload tube
held 660 grams of leaflets packed in three sections.
Flights were made with this style rocket to determine the
propellant ratio required to produce a range of 1,000
meters at burst point. A group of four rockets with the
proper weight and propellant ratio landed within a circle
of 50 meters in diameter at an average distance of 1,080
meters on the ground, which corresponds to a distance of
1,020 meters at burst point. The complete rocket, which
is essentially a production prototype, may be seen in
Plate 6.
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A system of bursting was devised which would eject the
payload as in the fashion of a mortar. This system
possesses the advantage of separating the leaflet section
from the motor section before the motor section is de-
stroyed by a larger blast; therefore, resulting in less
leaflet damage. The time fuse for the unit is under
development at this time, as is the system for destroying
the motor section of the rocket.
By increasing the length of the motor tube, sufficient
propellant can be carried for a range of 3,000 meters.
Following the static test of three ten inch grains in
such a motor, rockets were test fired into an earth
covered hillside at a distance of 125 feet. Although
some trouble was encountered in these models, one unit
apparently reached full acceleration, burying itself
deeply into the hillside. No damage to the unit was
observed which could be attributed to acceleration effects.
An approval to extend our present range has been granted
so that longer flight tests can be accomodated.
MOI
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411 IV, SUMMARY
The work in Phase II has established the design of a finned
rocket capable of carrying a 22 ounce payload 1,000 meters
with a probable dispersion of 50 - 60 mils. Sufficient
static and flight tests have been made to establish the
reliability and functioning of the design.
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Each component has had a design aimed at production although
it is anticipated that minor changes will be required to
facilitate a production model.
Tests have been made establishing the basis for a 3,000
meter model, although it is anticipated that completion of
this model may take longer than was first anticipated.
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V. FINANCIAL STATEMENT
Total Amount of Contract (Phase II)
Total Obligations to June 30, 1956
Balance of Contract (Phase II)
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PLATE 1
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PLATE 2
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PLATE 3
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PLATE 4
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PLATE 5
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PLATE 6
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