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The R&D phase of the project actually extended over a period of some seven years, in the course of which a completely operative experimental weapon known as the NIKE R&D System was created. It comprised most of the essential components of a realistic tactical system, the first practical embodiment of which eventually overtook it when a tactical design, designated as NIKE I, was put into customer's test and even troop training operation while the R&D phase was still in its final stage.
This chapter describes the evolution of the NIKE System--how it
progressed from a drawing board conception, through a series of
developmental stages, to reach its climax as a complete experimental
system for demonstration and test purposes beginning in late 1951. An
effort is made to relate the NIKE development story in historical
sequence as it unfolded itself; however, to minimize interruption and
resumption of the tale of developmental progress of various components,
the presentation must necessarily depart from a true chronological
narrative. Yet, the various development phases of the program are
divided roughly into calendar years for easy reference. The completion
of one program phase and the beginning of the next did not always
coincide with the new year or recur at twelve-month intervals; and the
design, shop, laboratory, and field work of the various development
phases had to overlap.
The first outline of a hopeful minimum schedule, drafted as early as 27
July 1945, envisioned the execution of NIKE development by four
agencies as listed in Figure 1. As the project progressed, however, this
rather optimistic schedule had to be repeatedly revised. For instance,
the total number of articles tested tripled the number visualized in the
original estimate, and the time of the entire R&D program extended to
April 1952--that is, to six and three-quarters years rather than four.
The actual history of the project, as viewed in retrospect, is
reflected in Figure 2. The progress of the complex system is divided
into major channels of pursuit relating to the computer, the radars, the
control machinery, the booster, the missile structure, its aerodynamic
performance, and its damage potential. Here again, the story cannot be
told by merely following these columns through the years, because the
efforts overlap, branch off, and recombine, and because other components
such as the launcher, the test equipment, and accessories came into
focal view as specific problems were encountered.
In line with the schedule shown in Figure 2, the project was broken
down into several phases, each of which was established as a yearly
development program. The 1946 Missile, designated as Model NIKE-46, was
to be designed and fabricated far a field test program to study
uncontrolled vertical flight. Wooden dummies and powered NIKE-46
missiles were scheduled for firing at White Sands Proving Ground to
provide information on launching methods, booster propulsion,
separation, motor performance, and flight stability data. The NIKE-47
model was to be a revised version of the KIKE-46 for continued
uncontrolled vertical flight studies. Programmed control and roll
stabilization were to be incorporated and tested in the NIKE-48 model.
The final product, with full ground control and warhead provisions, was
scheduled for completion and test as the Nike-49 model.
As specified in the initial AAGM study, the NIKE Missile was to be
designed to provide a defense against aircraft capable of flying at 600
miles per hour at 60,000 feet altitude. The approximate practical
horizontal range of the weapon was to be on the order of 12 miles. The
highly maneuverable, high-speed missile was to be launched and steered
from the ground, and guided to impact by signals derived from a radar
tracing system.
The missile was proposed to be about 19 feet long, with an overall
weight of 1,000 pounds, 300 pounds of which would be the weight of the
fuel and oxidizer. Four large triangular fins were to be provided at
the aft end of the fuselage, with four movable surfaces forward for
missile control and guidance. The missile was to be fired vertically
from a launching assembly of guide rails, and boosted to supersonic
speed in about two seconds by a high-thrust booster unit having eight
solid fuel rockets, with a total thrust of 93,000 pounds, arranged
concentrically about the tail of the missile. The weight of this type
of booster unit, with fins, was calculated at 2,020 pounds.
At the end of the boost phase, the booster assembly would be
dropped and the missile would travel under its own liquid-fuel rocket
power until the propellants were consumed, then zoom to impact. The
performance characteristics were calculated on the basis of the use of
a 3,000 pound thrust, regeneratively cooled rocket sustaining motor,
with an aniline mixture as fuel and red fuming nitric acid as oxidizer,
having a burn-out at 24.3 seconds after launching. The propellant tanks
would be pressurized by metered pressure from a high-pressure nitrogen storage system.
The velocities expected from the missile were initially conceived at
1,750 feet per second at the end of a booster phase of 1.8 seconds,
increasing almost continually to about 2,500 feet per second at the end
of the missile meter operation, then decreasing to 1,150 feet per second
at 96,000 feet during the zooming period. Calculations of velocity were
not established beyond this point--a Mach number of l.2--because of
uncertainty of control in the transonic region. The accelerations
expected were about 25g at the start, increasing to about 35g at the end
of the booster phase. A missile maneuverability requirement of 5g at
40,000 feet was tentatively chosen.
A stabilization system was to be incorporated to control the movement of
the missile in roll, pitch, and yaw. A guidance system would maintain
the missile upon an optimum trajectory to the point of fragmentation,
based on data supplied by two radars--one tracking the target and the
other tracking the missile--correlated and converted into steering
information by a computer. The plan called for optimum fragmentation of
the missile and warhead by a burst signal computed for each encounter
for greatest kill probability.l
The NIKE R&D System, which was later developed by the foregoing
specifications, is a lineal descendant of the original system conceived
in the AAGM Report and differs from it only in comparatively minor
respects. The nature of these changes and the subsequent history of
Nike development are fully treated in succeeding portions of this Chapter.
The latter half of 1945 and early 1946 was spent in planning the
detailed requirements of the various components and in making early
design studies and tests. The DAC came into the picture at this time
and began a complete study of the aerodynamics of the missile as proposed
in the initial AAGM study. Booster design was also started at this time
by the AeroJet Manufacturing Company.
One of the first deliberate departures from the original system
recommendations, accepted in the fall of 1945, concerned the radar
tracking system. A study of the angular accuracy requirements of the
tracking radars and echo fluctuation measurements on metal-painted free
balloons and airplanes in flight revealed that conical lobing methods
would be inadequate to yield the required smoothness and accuracy of
data.l
Radars had been used extensively during the war, not
only for surveillance and detection, but also for the pointing of
antiaircraft guns. Yet none of these was sufficiently accurate for the
problems posed by the guided missile. Since the standard lobing radars
developed during the war were limited by rapid pulse-to-pulse fading, it
was obvious that a more accurate radar would have to be developed
specifically for NIKE. The smoothness of output would have to be such
that target acceleration maneuvers could be promptly detected and
countered without long delays necessitated by smoothing rough data.
Hence a decision was made to develop a radar system which would provide
an independent measurement of angular error on each pulse (monopulse
type) and thus eliminate angular perturbations caused by rapid pulse-to-
pulse fading.
Two different monopulse systems were studied. One was a phase comparison system,
and the other an amplitude null system, in which the
rapid fading signals received from the two-lobed beams are subtracted
from each other to obtain the angle error signal. The latter method was
decided upon because it was simpler and more readily mechanized.
Of other radar features, attention was focused on the problem of
obtaining high transmitter power with a wide range of tunability to
attain maximum protection from jamming. This study resulted in the
development of 250-kilowatt X-band and 1000-kilowatt S-band tunable
magnetrons for the NIKE and T-33 radars.
A missile model of 0.4 scale vas built in order to measure its radar
reflectivity. Tests with a K-band radar illuminating the model led to
the conclusion that in reflection tracking a range of between 50,000 and
100,000 feet could be attained with a radar peak power of 125 kilowatts
at X-band. This would barely meet the original requirement of a 60,000
foot range for the missile. Meanwhile, it was found desirable to extend
missile performance to 150,000 feet and the missile tracing range a like
distance. To obtain a reliable signal from the missile by reflection
tracking to this range would have required techniques too far beyond the
state of the art. The only alternative vas to place a beacon responder
in the missile to insure a clear missile signal. There were a number of
other equally important factors that justified the use of the beacon
responder. First the missile had to be acquired in the launcher
the presence of strong ground echoes; second, at the separation
of booster from the missile, both parts were likely to return equally strong
reflection signals so that the booster could pull the radar off the missile;
third, the flame during motor burning might cause tracking interference; and
finally, during the end game the missile radar would have trouble distinguishing
between the missile and target as the ranges became coincident.
All of these problems were successfully solved by the responder, which
provided an echo signal considerably stronger and different in frequency
from any of the interfering signals.
Next to be considered were the problems connected with the design
and operation of a suitable responder of very light weight. To obtain
the features of a responder, it was only necessary to add a relatively
small transmitter unit to the X-band receiver which was already required
an board the missile to receive the steering and burst orders. Modulator
circuits of the ground-to-missile communication system were constructed
and successfully tested in the laboratory far performance.
Early in the design study phase, it became apparent that the actuators
for tile control surfaces3
would require servomechanisms whose
speed and torque exceeded that of any type then available. Because of the
wide range of aerodynamic stiffness encountered, it was also recognized that
the servos would have to be stable over a range of gain of
aerodynamic hinge moments could be of the order of 2,000 inch-pounds in
the case of roll, and 700 inch-pounds in the case of steering. Full
deflection of fifteen degrees would have to be attained in about 0.1
second. A study of the problem indicated that it should be possible to
fulfill these requirements with a hydraulic servo system governed by an
electrically controlled valve. Since no valve was available to meet
these requirements, a special development program was initiated to
produce a series of hydraulic valves which were eventually used in all
NIKE missiles.
As to the control scheme for the servo system, it was agreed that
the main feedback would have to come from a free position gyro for roll
control and from transverse accelerometers for the steering orders.
Gyroscopes of various makes had already been developed for other purposes and
mainly required the installation of suitable potentiometer
pick-ups. Accelerometer transducers, however, were not currently
available in a suitable range and with appropriate damping. Consequently, a
program was initiated to develop a special NIKE accelerometer transducer with
magnetic damping. The hydraulic servo power system comprising actuator pistons,
pressure vessels, and plumbing
could be recruited with minor refinements from the contemporary
aircraft hydraulic art.
In the meantime, DAC had started an intensive study to determine
the aerodynamic characteristics likely to be obtained from the missile
configuration assumed in the AAGM Report. The advantages of the canard
arrangement and the delta shape of the cruciform rear fins were soon
confirmed and retained throughout the development. The movable
fins in the forward part, however, were redesigned. They were reduced in area, moved
farther ahead toward the nose for greater leverage, and their shape was altered from
trapezoidal to a twenty-three-degree semi-vertex angle delta for lower drag and smaller
center of pressure
shift. Wind-tunnel test, were then conducted on a scale model of the
new configuration at a Mach number of 1.72 in the only supersonic facility then
available; vis., the Ballistics Research Laboratory at Aberdeen Proving Ground
(APG). Though scanty in many respects, the test results gave the first directly
applicable data concerning the aerodynamic behavior of this type vehicle in lift,
brag, and pitching moment.4
Moreover, they partly confirmed and partly
eased the conservative assumptions or restrictions adapted in the AAGM Report.
The NIKE missile structure was to be designed to provide adequate
strength and rigidity with the least possible weight. Since a missile is expended
on each flight, non-strategic materials were to be used wherever possible without
sacrificing the strength-to-weight ratio needed to obtain rapid acceleration during
the boost phase and high maneuverability during the guided flight phase.
Other factors influencing the missile body design were aerodynamic smoothness, warhead
fragment spray pattern, component packaging, and access to installations. Surface
smoothness and the minimum practical thickness compatible with rigidity requirements
were the main design criteria for the fins.
A preliminary design study of a practical missile structure dealt
with such problems as weight estimates, the center of gravity due to fuel
consumption, fuel flow, and ease of fabrication and assembly. For ease of fabrication,
the tank structures were changed to comprise two spherical air pressure tanks and two
separate cylindrical tanks for acid and aniline fuel, respectively. This simplified
the fin attach structure
and facilitated tank testing and accommodation of accessories in
functionally-grouped sub-assemblies. The electronic guidance compartment and center
warhead were interchanged to improve balance. In the area of control fins and their
mechanisms, staggered shafts for pitch and yaw fins were advocated. As to the rear
body, a sturdy motor mount
was envisioned, with its plumbing readily accessible.
On the basis of experience just being gained with WAC CORPORAL missiles
undergoing tests at White Sands Proving Ground (WSPG)
[Now known as White Sands Missile Range-name changed in 1958.],
design studies of cooled and uncooled motors were begun at AeroJet Corporation.
The choice of a suitable and industrially procurable booster was
narrowed down to two alternatives: one comprising eight ten-inch T-1OE1
rockets, and the other a quadruple cluster of thirteen and one-half-inch
Aerojet rockets. Canting the rockets or their nozzles was considered
as a possible means to reduce or avoid undesirable thrust moments. The
booster-to-missile attachment was studied with a view to avoiding high
loads and separation difficulties.
A continuing program of warhead design and experiments was carried
on between BTL and BRL. The first proposed warhead consisted of a
small tapered central cylinder of high explosive which would eject a
mass of shrapnel pellets in a flat expanding shaped disk shower, whose
velocity was essentially the missile's terminal velocity. Meanwhile, new data on
small high-velocity fragmentation warheads made these appear
more attractive from the lethality point of view and also because they
allowed for the possibility of an effective tail chase. For the next
four years, an experimental program was carried on to produce an adequately
wide fragment beam, to obtain uniform velocity distribution over the beam,
and to provide uniform break-up into fragments of the double-wound wrap of
wire which constituted the source of the lethal particles.5
The design studies and decisions just discussed were reviewed in a
planning conference on 28 January 1946, and the development program for
the 1946 NIKE was established.
The period essentially covering the year 1946 was deliberately
devoted to the independent development of major system components, which
was pushed forward on many technical fronts. It included laboratory
simulator work and culminated in the first real experimental missile
firings on the test range.
As stated in the section dealing with the plan of development, the
1946 NIKE was to be designed and fabricated for uncontrolled vertical
flight tests to provide information on launching methods, booster propulsion,
separation, motor performance, and flight stability. While
the preliminary design studies were being reduced to practical
application in the form of the 1946 NIKE missile, work was continued on
development of ground guidance components for installation and test
in later missiles.
Radar
To gain experience with monopulse tracking in the X-band region, an
SCR-545 radar was converted to this new type of operation. In making
this conversion, the antenna system was replaced by a monopulse rapid-
fading (RF) system with a lens antenna. The performance of the SCR-545
mount for the monopulse system was improved by the addition of tachometer
feedback in the angle servos.
As originally envisioned in the AAGM Report, the target and missile
tracking radars were to be combined into a single mount with two separate
lens antennas mounted on a rotatable beam structure on top of a common radar van.
The azimuth of the target radar beam was to be adjusted by moving the entire beam
structure, and the difference between the target azimuth and the missile azimuth
was to be adjusted by moving the missile radar antenna with respect to the beam
structure. This original plan was dropped mainly because of the excessive power
requirements to meet the slewing rates and because of the problem of one antenna
assembly shadowing the other when mounted in such close proximity.
Consideration was then given to the idea of having both antennas
rotate in azimuth with respect to the beam structure and making the beam
structure rotate only as required to prevent shadowing. Further study
of this dual mount, however, revealed serious drawbacks, such as severe
requirements of the mechanical rigidity of the top-heavy rotating super-
structure, bending of the beam assembly due to solar heat, and the
problem of placement of a common vehicle so that radar visibility is
obtained in all launchers without jeopardy of best target coverage of
the defense zone.
To avoid these difficulties, it was finally decided to abandon the
dual mount structure and accept completely separate mounts as a more
attractive solution. With each track antenna assembly mounted on a
separate low-slung flat bed trailer, both mounts must be accurately leveled
and an adjustable parallax correction provided in the computer.
The basic power supply for the radar was standardized at 400 cycles
per second rather than the usual sixty cycles per second because of saving
in weight and size for power equipment. Experimental studies of the acquisition
radar resulted in the choice of S-band and in the raising of the power requirement
of the tunable magnetron tube to 1,000
kilowatts.
Computer
In a system such as NIKE, the characteristics of the guidance computer are
of critical importance during the last few seconds before
intercept. It was recognized that one of the terminal accuracy problems
centered around the possibility of filtering out the tracking noise
without unduly delaying the recognition of a true target maneuver. Same
thought was given to determining the optimum steering function by hand
computations; however, it was soon realized that the enormous number of sample
computations required would make such a procedure virtually
impossible.
Consequently, early in 1946, an analog device called the Computer-Analyzer
was build specifically to analyze the end game. This apparatus
solved the guidance equations in two dimensions so that lateral miss
could be studied under wide variations in the steering order equations,
the noise level, the smoothing and stability parameters, and the magnitude,
nature, and timing of target evasion. Over 7,000 runs, comprising nearly 700
distinct situations, were made and analyzed. From these runs emerged optimum
smoothing, prediction, and order-shaping techniques, in addition to a large
body of knowledge concerning the effects of various kinds of target maneuvers.
The circuits of the R&D computer were based on this analysis.
By the end of 1946, the computer design had advanced to a block
diagram stage from which the detail design could be made. The computer
philosophy adopted was quite different from that conceived in the original AAGM
Report, but most of the basic plans were retained in modified form. To simplify
the prediction process, the coordinate system of the computer was changed from
the polar radar form to Cartesian earthbound axes, oriented according to the
pre-launch axis bearing of the missile gyro. This presentation was more adapted
to overcome the parallax problems inherent to the two separate antenna stations
for missile and target radars, and the considerable separation required by the
radar and launching sites. It also afforded greater flexibility in choosing the
most advantageous trajectory shape, as well as easing the resolution of steering
orders into their pitch and yaw components. These changes also necessitated the
introduction of a new method of trajectory shaping to approach the most efficient
night path.
Detail design studies were started on the subjects of steering
order computer, prelaunch computer, burst computer, sequence of operation,
component accuracies, voltage regulation, standardized feedback amplifiers,
radar-to-computer data, transmission system, and visual
means for displaying the attack.7
NIKE-46 Missile
At the beginning of the 1946 development period, a decision had been made to
proceed with the manufacture of fourteen experimental
missiles for flight test at WSPD in the fall of the same year. The
first four of these were to be ballasted wooden dummies simulating a
missile in shape and inherent dynamic properties only. In addition to
furnishing much needed drag information, they were destined to prove booster propulsion
and separation or to show what unexpected problems
might arise. The other ten were to be real missiles in the sense that
they would be equipped with a self-sustaining power plant. No attempt
was yet to be made at roll stabilization. Neither would these missiles
be controlled in pitch or yaw; their fins were to be fixed. The purpose of the latter
ten rounds was to study power plant operation and
flight stability under power.
Wind-tunnel tests of the 7.5 per cent model of the NIKE missile
were continued at APG to cover an intermediate speed (Mach number 1.28), in addition
to the higher one (Mach number 1.72) previously explored.
These experiments were supplemented by subsonic teats on other scaled
models in the ten-foot wind tunnel at the California Institute of
Technology. Lift, drag, and stability, as well as aileron and control fin
hinge moments, were determined and found to be generally satisfactory.
The design of the first test missile was frozen by the middle of February, 1946.
This design (see Figure 3) embodied a cruciform delta wing canard configuration,
the details of which have already been discussed. Though basic requirement of the
concept8 were maintained during the engineering
and fabrication of the 1946 missile, certain revisions were
made in the light of actual design development and in the
adaption or the missile to its uncontrolled test program functions.
Figure 3. NIKE-46 Missile & Booster in 4-Rail Launcher (12 Nov 46, WSFG)
Booster Assembly.
Among the principal changes was the use of four parallel Aerojet solid fuel
(Paraplex) rockets with uncanted
nozzles, designed to deliver a thrust of 22,000 pounds each for two
seconds and impel the 1946 type of test missile to supersonic velocity.
The early designs-based on the grouping of eight T10E1 11,000-pound
thrust rocket units-were discarded at the end of March 1946, when the
development of the larger Aerojet units had sufficiently progressed for
incorporation in the 1946 program. Development of the 22,000-pound-thrust
booster rocket for the NIKE-46 was initiated at the Aerojet Engineering
Corporation in April 1046, under a subcontract from DAC.
Aerojet was to furnish 56 boosters, to be assembled in clusters of four
each bye DAC. Preliminary development of the booster assembly was completed
in July 1946 and static proof firings were started in the
following month. Out of a total of 68 full-scale firings, eight failures
were experienced, two of which occurred at WSPG. One additional failure
occurred near the end of boost in a WSPGP launching, when the nozzle of
one unit was burned through. Although the test results indicated a need
for further improvement in reliability and reproducibility, booster
performance gave promise of ultimate fulfillment of the desired degree of
reproducibility.
The propellant finally selected for the booster rocket consisted of
a single perforated grain Paraplex-base fuel and potassium perchlorate
oxidizer. The particular formulation of constituents used for this
application was designated as AK-6 propellant (formerly called PF-6),
having the following composition by weight: Potassium Perchlorate, 73L%;
Paraplex P-10, 26.85%; and Tertiary-Butyl Hydrogen Peroxide, 0.15%. The
ignition element consisted of granular black blasting powder contained in
a plastic capsule, together with two ordinary electric blasting squibs which
served as initiators.9
Power Plant The power plant for the Nike-46 missiles comprised a
bi-propellant, regeneratively cooled, liquid rocket motor. Developed and
manufactured by AeroJet as Model X21AL-2600, the 40-pound motor was designed
to produce a sea level thrust of 2,600 pounds for 21 seconds A fuel mixture
containing about 65% aniline and 35% furfuryl alcohol
was oxidized by red fuming nitric acid. The liquid load consisted of
220 pounds of oxidizer and 80 pounds of fuel. The propellant tanks were
constructed as integral structural parts of the missile fuselage.
Development of the rocket engine for the 1946 NIKE was initiated at
AeroJet late in 1945, under a subcontract from DAC. Aerojet was to
furnish rocket meters, control valves, and pressure regulators (for
pressure feed system) for ten missiles. Other components of the power
plant, including tanks, lines, and starting valve, were designed and
fabricated by DAC. The development tests were completed by the end of
April 1946.
The design of the prototype assemblies vas predicated on the final
version of the respective experimental assemblies. The prototype motor
and control valve were successfully fire-tested on the thrust stand
during May. Final proof fire tests were made in a mockup of the actual
NIKE installation, using the field firing sequence. Test results were
equal to specification requirements and the design was declared adequate.
The complete power plant was then subjected to a fall-scale static test at
WSPG. Acceptance tests on the tenth motor were completed in
September 1946.10
Structural Arrangements In the structural arrangements, the delta
shape was selected for both the control fins and main fins to improve
the lift-to-drag ratio, and the control fins were moved farther forward
along the missile body than was suggested in the basic plan. The design
studies revealed that considerable advantage could be gained in the use
of two spherical tanks for the high-pressure gas storage, mounted between
separate tanks for the oxidizer and the fuel. With this arrangement, the
space around the spheres could be used for improved wing-attach structure
and power plant components, and the aft section could be removed as a unit
for easy access to the motor installation. The wing structure vas designed,
in conjunction with the booster assembly, to reduce the moment arm of the
applied thrust of individual booster cylinders.
After allocations had been made for missile components, the length
of the missile vas increased from the proposed 19 feet to 19.5 feet in
order to provide additional warhead space. The proposed warhead was
first divided into tun units, one to be located in the nose section and
the other in the aft section. On the basis of fragmentation tests, it
was later decided to divide the warheads into three sections--one located
in the nose section, another in the middle section forward of the oxidizer
tank, and the third in the afterbody of the vehicle forward of the motor
installation. Space intended for the warheads, control mechanisms, and
radio equipment of the final missile was used for instrumentation and
beacon radio installations in the NIKE-46.11
Instrumentation
All experimental missiles were instrumented in an effort to gain as much quantitative
performance information as feasible from each and every flight. The R&D design
philosophy was governed by a decision that missiles were never to be fired as
mere test vehicles but as steps in the evolution of the eventual weapon.
Consequently, instrumentation had to be accommodated where space could be
found. During the early stages of the test program when no control equipment
or warheads were carried in the missile, there was sufficient room for
internal instrumentation. However, as development progressed and more
control mechanisms were carried in test flights, less space remained for
instrumentation. In the final version, which included warheads, no internal
space was left and external instrumentation had to suffice.
The original program called for simple missile-borne instrumentation to
record linear accelerations and rolling motion in flight of the powered test
missiles. Telemetry was expected to emerge eventually as the ultimate solution
for future missile-flight test-recording work; however, none of the missile
telemetry development programs then being pursued had progressed far enough
to produce a reliable apparatus that would fit into the NIKE test rounds at
the time the NIKE-46 program was crystallized. Therefore, a conventional
photographic system of recording instruments was used in the hope that a
legible film might be recovered from the impact wreckage. No recording
instruments were carried by the three dummy rounds. Each powered missile
was equipped with a radar beacon to serve as a tracking
aid.l2
Launcher Equipment
The basic launcher arrangement, as taken from the AAGM Report, consisted of
four vertical guide rails spaced at 900 about the missile,
but passing within the booster structure. As the booster cylinders-originally
eight Tl0El units-were supported outside the guide rails, the members had to
be cantilevered from a rigid base. In later design development of the booster,
when the T1OE1 rockets were replaced by four Aerojet 22,000-pound thrust motors,
further restrictions were placed on the size and location of the guide rails
which could be accommodated
within the booster structure. The length and cross-section of the rails
were determined by calculating the cantilever length feasible for the moment
of inertia of the members and consideration of the booster velocity and
stability which would be obtained in the launcher at take-off.
The design of the mechanism for raising and lowering the rails was
dictated by the availability of component equipment. This problem eliminated
hydraulic mechanisms, and to a large degree restricted the
kind of electric actuator, which would be considered. A one horsepower
electric motor was selected to drive a cable drum through a worm gear
reducer.
The first such mechanical launcher, from which the 1946 series of
test missiles were to be launched at WSPG, was built in the form of an
assembly of four parallel steel rails of hollow rectangular cross-section welded to
8 pivoted root frame on which it could be tilted to a horizontal position for loading
and raised for (nearly) vertical launching. (Note launcher assembly in Figure 3.)
During the launching operation, the missile would slide upward between the rails,
guided by pins, while
launcher proved adequate, it was subject to appreciable vibrations which
were difficult to measure. The vibration problem was later eliminated
in several steps of redesign of the launcher, all aimed at making it
sturdier and simpler.13
Missile Designations
For record purposes, the missiles were identified by a double set of
labels; viz., a "Round Number" and a "Missile Number." The Round Number
was a chronological firing test serial number, the dummies being identified
by alphabetical letters beginning with Round A and powered flight launchings
by numerals beginning with Round 1. The Missile Number, which served as a
factory identification number, consisted of two symbols separated by a hyphen,
the first part denoting the design year or model number and the second pert
(after the hyphen) denoting a chronological manufacturing serial number.
Dummy missiles were serially designated by letters placed after the model
number prefix--e.g., NIKE-46-A--while powered missiles were distinguished
by numerals, beginning with Missile No. NIKE 46-1.14
First Experimental Firings
In the fall of 1946, test facilities at WSPG were readied for the
first experimental series of NIKE firings. Fourteen missiles had been
manufactured and delivered, four of which were inert (wooden) dummies and ten were
powered but uncontrolled missiles. The dummy missiles were constructed by mounting
production-type main and control fins to solid
fuselages made with laminated mahogany. All the test missiles were ballasted
with lead to bring the gross weight to 1,000 pounds, as originally
specified for the final weapon. The expendable portion of this weight
amounted to 312 pounds--220 lbs. oxidizer, 8O lbs. fuel, and 12 lbs. air.
The basic design characteristics of the NIKE-46 missile and its
components have already been discussed.
Before conducting the first flight test, one missile (No. 46-1)
was static-fired to prove power plant operation, to test the servicing
and firing equipment, to determine the effect of motor operation on
performance of the radar beacon and missile instrumentation equipment,
and to familiarize the field personnel with the techniques involved.
After the static test firing on 17 September 1946, Missile 46-1 was
returned to the DAC Santa Monica Plant, where it was inspected and
overhauled. It was then sent back to WSPG and flight fired as Round 4
of the test series.
Flight firings of the NIKE-46 missile began at WSPG on 24 September
1946 and continued through 28 January 1947. Of the fourteen missiles provided
for the 1946 test program, three wooden dummies and eight powered but uncontrolled
missiles were actually expended during this series of firings. A ninth round
(Missile No. 46-4) was recovered intact, though damaged, after a booster misfire.
(One dummy and one actual missile--46-D and 46-10--were not fired in this series
but were reserved for a future test purposes.)l5
A brief account of
the first twelve flight firings is given in Table 1 of Appendix 5.
(dummy) tests were entirely successful. The boosters detached themselves at altitudes
of about 2,000 feet and the missiles coasted to altitudes
of 30,600, 43,300, and 42,150 feet, respectively. These unpowered tests convincingly
demonstrated the feasibility of vertical take-off under boost
thrust, acceleration to a supersonic velocity of about 1,900 feet per second, and
stable flight before and after booster separation.
Figure 4. NIKE 46-1 in Flight (18 Oct 46, WSPG)
The first unguided powered missile tests followed in rapid succession.
They were spectacular and full of dramatic surprises. The very first one,
fired on 8 October 1946, made a completely successful
flight, reaching an estimated peak altitude of 140,000 feet. The
second round traveled 17 miles and the eighth over 25 miles, demonstrating
not only more than the predicted range capability, but also the need for
safety destruction in case of a runaway.16
Both the second and eighth rounds reached a peak altitude of over 100,000 feet.
However, the other rounds were unsuccessful because of poor
a peak altitude of only 58,900 feet, exhibited intermittent motor
operation and poor separation of the missile-booster combination.
The separation problem repeated itself in the fourth and fifth rounds; the
sixth and seventh rounds were wrecked by booster explosions during
launch; and the ninth round was a booster misfire.
Failure of motor operation in Round 4 and complete loss of the
motor after separation in Round 5, together with other evidence of
structural damage, led to the conclusion that some violent lurch was
caused and damage was inflicted by the booster upon the missile aft
section during separation. This trouble was presumably due to some
irregularity of thrust or premature burn-out of one or more of the
four rocket boosters. To remedy this problem, guide rails were installed
between the missile and the booster, and the booster nozzles were canted
so that the line of thrust of each booster would pass through the center
of gravity of the missile. Some thought was given to changing the entire
booster concept; however, it was decided to continue with the four-booster
unite, at least for the time being, so that other parts of the program could
advance on schedule.
Information obtained from missile tracking radars was very meager
since the tracking beacon was silenced in every instance by violent
events during or at the end of boost, frustrating the planned tracking
tests. The troubles encountered in the first few rounds were diagnosed
with reasonable certainty and corrected: however, in most of the latter
rounds the beacon vas damaged along with other items in the rear of the
missile. The fact that the beacon failed during boost rather than at
separation indicated the existence of more problems than those attributed
to poor separation.
The discovery, analysis, and clarification of problems encountered
during these experimental firings came as a result of elaborate
instrumentation. Arrangements had been made with WSPG to obtain maximum
coverage of the missile trajectory from the network of cinetheodolite
stations then available. This was still in a somewhat rudimentary stage
in 1946; time correlation of stations was precarious and indirect, frame
sequence was four exposures per second at best, and evaluation was
unmechanized and painfully slow. Thus, the accuracy of position data
obtained was hardly sufficient to determine acceleration to a
significant precision.
It was therefore fortunate that provision had been made to equip
the missile with airborne instruments. In the early period, before the
advent of reliable radio telemetry, this was done by means of a flight
recorder which consisted of two missile-borne motion picture cameras
photographing tvo sets of instruments in flight. These instruments were
axial end transverse accelerometers, a fuel regulator pressure gauge,
several aerodynamic pressure gauges, and a heliograph. The latter was a
specially developed optical device which, with the aid of four extreme
wide-angle lenses, produced a pictorial record of the relative position
of the sun and the horizon. From these records, the history of the
attitude and orientation of the missile in space could be reconstructed
by a somewhat laborious evaluation technique. But first the impact of
the missile on the ground had to be located by a search team and the
armored film cases had to be recovered from the wreckage. It was often
necessary to dig a considerable depth before retrieving the film records.
To improve the changes of film records surviving the impact, film magazines
were protected by means of armored cases and shock-absorbing packing, and
the velocity of impact was reduced by blasting the main fins during descent.
The photographic records disclosed a number of significant episodes.
One was the occurrence of a prolonged stable corkscrew motion of Round 2
on its spectacular 17-mile flight. A somewhat similar motion was observed
on Round 3 which was also troubled by malfunction of the pressure regulator
in the fuel feed system, and a chemical fuel fire started in flight which
eventually set off the fin destructor, causing the missile to tumble during
its subsequent descent. improvised booster-borne cameras gave pictorial
evidence of kinematic separation difficulties.
In November 1946, while the field test program was still in progress
and before the seriousness of the booster difficulties was fully realized,
a planning conference was held at WSPG to map out a tentative but optimistic
missile test program for the next two years. This program was designed to
lead in a systematic sequence of stages to the development of a practical
missile which could be flown under command of radar and computer as soon as
the latter equipment became available. Thus the system guidance loop would
be demonstrated in action. The development test program envisioned the
successive construction of a family of missiles
controllable to a gradually increasing degree. In case of troubles or
malfunctions, it was decided that the firing program would be interrupted
or expanded and recognized errors rectified before proceeding.
Radar Development
In 1947 radar development effort was directed toward the determination of the
best antenna configuration and antenna axes orientation. After investigating various
alternatives, the requirement of tracking the target through the zenith was
eliminated. This region was not considered
sufficiently important to justify the additional complexity in a guided missile
system in which the intercepts usually occur on the incoming course.
Considerable development and experimental work was also devoted to radar gain
control. Since the speed of response of the gain control circuits in a monopulse
was no longer limited by the lobing rate, the initial work was directed toward
proving an instantaneous gain control circuit in which the gain would be properly
set for the level of such {?each?} return pulse. Such a circuit was tried
successfully but was later replaced by a simpler wide-band integrating type
of automatic gain control.
During the fall of 1947, the improvised experimental monopulse radar set
was equipped with a 6-foot X-band lens and put through extensive three-coordinate
operation, tracking various aerial targets at Whippany, New Jersey. Accuracies
considerably better than one angular mil were consistently attained for short
periods and one decimil deemed within reach. While much work was destined to
be done before achieving consistent high accuracy, the superiority of this type
radar over any previously available
system was already convincingly demonstrated.
While the above tracking tests were in progress, basic advances were
made in the improvement of rapid-fading plumbing for the mono-pulse radar
then under development for the field test program at WSPG. Comparison
studies were conducted on Hybrid rings and tees to determine the advantages
of each, particularly
tin regard to wide-band operation. Hybrid
rings in tandem proved to be the better and were adopted for the final
R&D monopulse plumbing. At the same time, studies were made to find the
best method of fabricating the plumbing to meet the close mechanical tolerances
required.18
The NIKE-47 test missiles were beacon-tracked at WSPG with an SCR-584 radar
modified for operation in the X-band. Radar tracking in these test was
generally good. Acquisition of missile in the launcher and automatic
tracking of missile during boost and separation were accomplished and
verified as a solution to the missile acquisition problem.
However the microphonic response of the beacon to boost shock was troublesome.
A greater signal output was considered necessary to improve the
signal-to-noise ratio, and better antenna pattern in the missile
tail aspect appeared desirable.19
The 1947 missiles were also equipped with improvised "fail-safe" circuits
to enable detonation of the missile in the event of loss of contact between
the ground radar and the missile-borne beacon.20
Computer
Studies of the various computer section and their detail design were continued.
The problem of
radar-to-computer data transmission
received particular attention due to the great accuracy required of the
voltages representing the missile and target positions in space. Two possible
methods were under consideration: (1) the construction of exceptionally accurate
potentiometers to be directly driven by the radar shafts, as in gun fire director
systems; or (2) a two-speed synchro data transmission system driving two-speed
potentiometers in the computer.
The original AAGM assumptions on the aerodynamic capabilities of the
missile proved to be unnecessarily conservative. Investigation revealed that
the time of night could be shortened and computer computations simplified by
adopting a flight path which-though departing from the optimum in range-would
follow a single dive order sustained until the
missile had turned from vertical flight onto a ballistic trajectory
through the predicted point of intercept. This control scheme was eventually
adopted for the NIKE R&D Test System.
The original scheme of stabilizing the missile in roll was replaced
by a more flexible scheme which was actually easier to mechanize but
conceptionally more involved. In place of keeping the "belly" fins
precisely vertical, it holds the plane of the "transverse" fins normal
to the vertical orientation plane in which the free gyro is released at
take-off.
Click here to go to rest of Chapter 3
Figure 1. Tentative NIKE Development
Schedule-July 1945
Figure 2. Steps of Nike Development
January 1946 to January 1
(January 1941 to December 1947)
Footnotes for Chapter 3 - THE DEVELOPMENT PROGRAM LEADING TO SYSTEM TESTS
