NIKE-47 Missile

Because the NIKE-47 was designed to serve generally the same functions in tests of launching and unmaneuvering vertical flight as the NIKE-46, the basic configuration of the 1946 missile was retained. However, in light of the previous year's test results, several modifications were made

to incorporate newly-designed equipment.

The missile boat-tail section was redesigned and strengthened, with corresponding booster structural changes, for improved application of boost thrust and smoother separation or the booster from the missile. Improved rigidity of the booster assembly was effected by an overall strengthening of components, together with structural additions to give improved guidance of booster along launcher rails, to place the boost thrust against the missile base, and to prevent side movement of the booster relative to the missile during separation. Pointed caps which had previously served to streamline the booster motors and apply the thrust to the trailing edge of the missile rear fins, were deleted. The after-body of the NIKE-47 was designed to rest snugly in a cylindrical sleeve mounted within the booster structure. This arrangement afforded positive contact between the booster and missile during separation, thus preventing the booster from developing an angle of attack or sideward velocity before the beet-tail was sufficiently clear of the booster structure, as had been experienced in some of the 1946 tests.

A number of changes were also made in the internal design and performance characteristics of the multiple rocket booster to correct the separation problems arising from uneven or unequal thrust forces during the boost phase. The single Aeroplex K-6 propellant grain used in the NIKE-46 booster was replaced with two grains of Aeroplex K-14, which burns at a slower rate and with consequent lower chamber pressures. The thrust was reduced from a nominal 22,000 pounds to 18,000 pounds per motor, but the duration of burning was extended from about 2 to 2.5 seconds. Changes were made to give more positive support to the propellant grain, and measures were taken in the field to keep the propellant grains at fairly even temperatures during a conditioning period prior to the firing. A new igniter was also developed.

The power plant system for the NIKE-47 was rebuilt around an improved design of the Aerojet Model 2l-AL-2600 acid-aniline motor. This motor was ten pounds lighter than that of the NIKE-46, but it possessed essentially the same capabilities, delivering 2600 pounds (sea level) thrust for about 21 seconds. In the new power plant system, a single- unit inertia-actuated starter valve-propellants feed regulator replaced the two previous separate components. Burst diaphragms in the propellant tank air inlet lines not only prevented premature mixing of the fuel and oxidizer, but also the premature entry of propellants into the motor.²²

NIKE-47 Test Program

Five dummies (without motors) and four powered missiles were fired in the NIKE-47 series. These tests were conducted as a continuation of the tests begun in 1946 to study launching techniques, and to obtain additional aerodynamic and performance data an the missile in free flight.

The NIKE-47 firings were conducted in the following order:

Date	Round No.	Missile No.
9-22-47	D	47-E
9-26-47	E	47-F
10- 7-47	F	47-G
10-16-47	G	47-H
10-23-47	H	47-1
10-28-47	10	47-12
l0-30-47	11	47-13
12- 9-47	12	47-15
12- 9-47	13	47-16

The five dummy missiles (Rounds D through H) were made of hollow steel bodies with standard missile aft sections and fixed fins. Satisfactory flights were obtained in all dummy rounds, their peak altitudes ranging from 29,300 to 34,000 feet. The boosters for these rounds were equipped with nozzles outwardly canted (four at 15^o and one at 17.5^o) to minimize any turning moment about the center of gravity due to uneven thrust cessation among the four independently burning rockets. Clean separation was indeed achieved. Telemetering transmitters carried on the boosters gave good, informative records of booster burning pressures. With the various improvements in powder gain support and in nozzle manufacturing, it seemed that the quadruple boasters now gave an acceptable performance and separation. however, the deviation from the predicted climb path was excessive. Precise inspection and measurements of the canted nozzles disclosed dimensional variations which gave rise to unpredictable burning behavior and fusion, and hence thrust eccentricities, the elimination of which would have required the development of new manufacturing processes. To obviate this difficulty, it was decided to return to straight nozzles for the four powered missile launchings.

Following the dummy tests, four powered but uncontrolled missiles were fired, all of them with the new Aerojet power plant already described. With one exception, they gave evidence of satisfactory boost and separation. In one round the separation method performed admirably under extremely adverse conditions. Two of the four rounds attained peak altitudes of about 120,000 and 115,000 feet in smooth trajectories; the other two rounds were frustrated by premature detonation. Analysis of the aerodynamic data obtained in the tests showed that the drag was very Close to the originally estimated values or much higher than the 1946 values. This effect was to be further investigated in the 1948 flights.²³

Launcher and Accessory Devices

Several improvements were made on the launcher. Its four 20-foot rectangular cantilever rails were replaced by heavy walled steel tubing which was easier to repair or replace in case of accidental damage. Guiding action during launch was now applied entirely to the booster structure rather than partly to the missile body. A second launcher was built portable so that it could be disassembled for transportation and set up on any flat surface in the field for firing. Erection was accomplished by means of a hydraulic strut instead of the electric winch of the earlier models. Eventually the launcher rails were shortened by three feet so that the effective guide length was reduced from fifteen and one-half feet to twelve and one-half feet, which was considered to be the best compromise between guidance and accessibility.

A number of accessory devices were developed which greatly facilitated the assembly, checkout, and handling and servicing of the missiles at the Proving Ground and enabled the crews to carry on a continuous work schedule.²⁴

---- very poor image - very fat booster Photo from http://www.wsmr.army.mil/paopage/Pages/NikeAj.htm

---- "Page 50 consisted of a graphic that ceased to be legible." as per Claus Martel MARTEL-CR@ccsmtp.redstone.army.mil

----- start page 51 -6

next planning conference held in October 1947 Even though some problems of boost dispersion and power plant operation bad not been fully solved, it was decided to begin these tests in the summer of 1948. Meanwhile, plans were made to devote additional specimens of the 1947 model to a determined attack on the unsolved problems and to conclude their tests and evaluation in time to catch up with the control function tests, even if they should overlap. Such an overlap did occur and ran into the months of July, August and September 1948.

Radar Development

Apart from the missile performance test program, the design of the missile-tracking radar progressed and took definite shape in 1948. Principal effort was directed toward the design and construction of the monopulse angle tracking radar model for the missile tracking and ground steering phase scheduled to start at WSPD in mid-1949. For the NIKE systems field test phase, the duplex mount arrangement of the original plan-two antennas separated by 12 feet on a common rotating platform-- was abandoned in favor of two identical radar mounts placed 50 to 100 feet apart. By December 1948, the components of this radar were well along in manufacture and the set was scheduled for systems test early in 1949.

Considerable effort was also devoted to the design of components for the radar, especially the rapid-fading plumbing and associated receiver circuitry. After extensive laboratory experimentation, a satisfactory automatic gain control circuit was developed. The various wave guide plumbing parts were made by an electroplating process that produced very smooth internal wave guide surfaces within the allowable tolerance requirements. (This radar vas destined to transmit steering orders from a clock-governed programmer to the missiles during Phase 4 tests in 1950 and remain at WSPG well beyond the R&D System Tests in 1951 and 1952.)

In the meantime, the aircraft tracking data collected at Whippany during 1947 and 1948 on the modified SCR-545 monopulse system were being analyzed for the influence of range and glint on tracking smoothness and accuracy.²⁵

Computer Development

The actual construction of many of the commuter components was started in 1948 after accuracy studies had established the equipment requirements. It was determined that error sources would not lead to significant degradation of the NIKE system performance, that they were not serious, and were significant only in a few places in the computer.

The design of components and major assemblies had progressed to the point where the overall computer assembly arrangement was established and the design of computer housing started. A decision had been made to employ the synchro data transmission alternative between radars and computer, and design work on this equipment had reached a stage corresponding to other computer sections.

Another decision made at this time concerned the use of plotting boards rather than oscillographs to display the course of the engagement. Plotting boards present the picture at a considerably enlarged scale and give a permanent recording of the pre-launch predicted intercept paint and the missile and target trajectories.

Booster Development

Because of the uneven burning troubles experienced with the Aerojet cluster-type booster, a new and radical approach was tried in 1948; namely, that of a powerful single-r0clret booster which bad been perfected by the Allegany Ballistics laboratory. This booster was designed for the JPL-JHU²⁶ Bumblebee ram-jet to meet performance criteria similar to that established for the NIKE. Its double-base solid propellant of OV composition, prepared by the solvent method and cast with internal combustion surfaces, burned with nearly smokeless exhaust, while the AeroJet Paraplex rocket produced a dense smoke. The single-rocket motor alone was about 120 inches in overall length and 17 inches in diameter. Its average thrust over a burning time of 2.6 seconds was rated at 51,100 pounds, with a total impulse of 140,000 pound seconds. The propellant had a specific impulse of 187 pound seconds per pound.

In March 1948, designs were completed and fabrication was started to adapt the Allegany rocket as a single-unit booster for the NIKE. Naturally, the single booster had to be installed aft of, and in line with, the missile itself. This resulted in a rather long missile-booster combination, mainly because a space had to be provided between the booster and missile to avoid obstruction of the missile motor exhaust.²⁷ The connecting structure was built in the form of a sleeve and ring attached to the front end of the booster can by means of struts or legs, leaning ample vent area for the motor flame. A conical steel cap with a ---- start page 54 -9 graphite tip was attached over the booster chamber end to protect it from the beat and erosion of the looter flame. Because of differences in the center of gravity and the center of pressure in these missiles, a set of booster fins was designed to give positive subsonic and supersonic stability to the combination during launching Each booster was to have four fins of modified diamond configuration mounted near the aft end of the chamber.²⁸

During field feats conducted later in the year, a comparative study was made of the two booster designs under consideration--one comprised of a single Allegany JATO T39 2.6DS-51,000 solid propellant rocket²⁹ and the other of four AeroJet JATO 2.5KS-18,000C-2 rockets.³⁰ The performance characteristics of the two boosters were essentially the same; but from the standpoint of cost, assembly, and handling, as well as the possible tactical advantage of being smokeless, the single thrust-unit booster possessed definite advantages. Consequently, it was decided that the Allegany rocket would be adapted for future NIKE field tests. No further development of Aerojet cluster boosters was scheduled, but they continued to be fired until the stock was depleted.³¹

Launcher Development

To accommodate the long single booster, a new single-rail launcher was built. Its design was based on a refined pattern of the preceding Launcher No. 2 (portable, four-rail), in that an erectable rail assembly was supported on a flat tripodal base and the entire structure could be easily disassembled into manageable sections. This new monorail launcher, designated as No. 3, is shown in figure 7. It weighed only about 5,000 pounds, in contrast to 12,000 pounds for the portable four-rail launcher. It had a loading height of 5 feet, an erected height of 18 feet, and an overall height of 35 feet when loaded with the missile and booster.

Figure 7. Launcher No. 3-- Single-Rail (WWPG Photo)

In the nine test rounds fired later in the year with the Allegany booster, the single-rail Launcher was highly satisfactory, particularly in regard to the simple and rapid loading methods it afforded and accessibility for pre-firing servicing of the missile and Booster. These factors had a significant bearing on the decision to change to the single booster for NIKE.

Based on the success of the new single-rail launcher, preliminary drawings were completed for a light-weight mobile launcher, incorporating the running gear of an M-2 40 mm antiaircraft gun carriage. Possessing all major characteristics of Launcher No. 3, the new version was to be completely mobile and weigh about 3,000 pounds.³²

1948 Field Test Program

During the summer and fall of 1948, 26 full-scale NIKE firings were conducted at WSPG. These were divided into three test series--48-0, 48-1, and 48-2--each based on a separate design of the NIKE for the phase development plan of the project. From these designs emerged NIKE Models 484 and 490, which were to constitute the final missile configuration.

Three NIKE missiles (Rounds 31, 32, and 33) not expended in the 1948 program were returned to DAC for modification of the ram pressure system and control system. These were reserved for use in the first part of the 1949 field tests.

NIKE 48-0 Test Series

In a group designated as the NIKE 48-0 series, four Model NIKE-47 live (powered) missiles and one dummy, which had not been expended the previous year, were modified and fired in free-flight tests with the new Allegany single thrust-rocket booster. The primary objectives were to test the new launcher and booster, to obtain aerodynamic data on the booster-missile, and to continue to free-flight performance study. (See Table No. 2 of Appendix 5.)

The single booster, equipped with four suitably large trapezoidal fins, was first tested on dummy Round J, 17 June 1948. Although launching and early boost was satisfactory, this first flight was terminated by booster fin failure prior to separation.

After modifications had been made to strengthen the booster fins, three powered missiles (Rounds 14, 15, and 16) were fired in vertical flight tests, and a fourth (Round 17) at a slant elevation of 40^o north from vertical. In three of these rounds the motor burning time was shorter than expected. In the first test, a reduction in burning time of 2 or 3 seconds was apparently caused by incomplete filling of the acid tank, but high lateral accelerations could have uncovered the fuel tank outlet. In the third powered round, burnout occurred 5.5 seconds early. Uncovering of the tank outlets appeared to be the only possible explanation in this case. Burning time was two seconds short in the slant elevation firing, but due to the nature of the trajectory it was expected that some propellant would be trapped in the tombs as the openings became exposed. The firing at slant elevation presented no serious problems of launching, boosting, or missile performance.

Telemetered data obtained from missile-borne Bendix equipment, added for the 1948 tests, indicated lateral accelerations up to 4.5 to 6g during motor burning, apparently as the result of asymmetric thrust. The flight in which the motor had reached full burning time was detonated 1.9 seconds after burnout because the horizontal velocity was in excess of range safely limits. Because of the reduced thrust, the peak altitudes and times of flight were lower than predicted, but analysis of data further confirmed that the aerodynamic performance of the missile was satisfactory and the estimates of most aerodynamic characteristics were fairly accurate.

An improved explosive charge--17 ounces of cast TNT and 3 ounces of cast Tetryl-had been installed in the NIKE-47 powered missiles. As before, the charge could be detonated by beacon command or by a fail-safe system in the missile. In the four rounds fired, command detonation was accomplished when called for and the missile detonation was effective.³³

NIKE 48-1 Test Series

Most of the 1948 field program was devoted to tests of the NIKE 48-1 ---- start page 60 -15 series, consisting of four Model NIKE-47 dummies and 13 NIKE-48 live rounds of the cluster booster-missile configuration (See Table 3 of Appendix 5.) Three of the dummies were fired in launching and free-flight tests; one was allocated for a functional check of the detonator system operation. The live missiles, of the same aerodynamic design as the NIKE-47, were equipped with roll stabilization and steering controls, operated in response to orders from a missile borne programmer. The programmed control tests of these missiles were divided into two phases: Phase I calling only for repeated roll stabilization from induced spins, and phase II for pitch maneuvers in yaw and roll stabilized flights. Accordingly, the missiles were built to fulfill these test functions. For Phase I, the forward control fin mechanisms were locked. The power plant and general structural design of the NIKE-48 was very similar to the NIKE-47.

Of the 48-1 powered missile series, all but the first, which was destroyed by a booster explosion,³⁴ were successful as far as launch, boost, and separation were concerned. In most of the 48-1 rounds, the motor operation was also successful; however, there was continued evidence of lateral accelerations produced during the burning phase, apparently as a result of eccentric motor thrust. In one firing (Round 27), the motor produced thrust only for about 7 to 8 seconds. Test records indicated that the fuel system burst diaphragm only partially ruptured, causing an abnormally lean mixture and reduced cooling flow; the motor chamber wall was burned through near the nozzle entrance. Other than this instance, there were no significant occasions of premature burnout.

The roll stabilization, however, gave considerable trouble. Its nature was tedious to explore and could not have been readily understood had it not been for a detailed and extensive analysis of the 28 channel records of the telemetry. As noted above, the first NIKE 48-1 test (Round 18) yielded no information because of a booster explosion. The next three phase I tests (Round. 19 through 21) showed that the aerodynamic roll damping was smaller than had been predicted and that the addition of artificial damping was required. This was accomplished by the installation of a roll-rate gyro by means of which a damping signal was fed into the aileron control circuit, beginning with Round 22. At high angular rates its signal is sufficiently large to dominate the situation and cause the ailerons to deflect in the direction to stop the missile independent of the momentary roll position. When the roll rate is reduced to a low value, the roll position gyro regains control and brings the missile to the desired orientation.

The fifth missile roll stabilized when commanded, so the sixth was fired as a phase 2 steering control round. This missile (Round 23) shared a violent steering instability with resulting oscillations. The absence of any high frequencies formed a basis upon which to change the circuits for another steering control round. However, before the next steering round was fired, it was discovered that the only explanation for several discrepancies in data from Round 22 was that the roll gyro brush had been grounded. The stabilizations of Round 22 could be explained as entirely fortuitous, as all of them had occurred under conditions where some of the previous missiles had roll stabilized.

Therefore, another Phase 1 (Round 24) vas fired to gain further information on the performance of the roll control system with the rate- gym installed. The gym operated satisfactorily in this test, but the need for more roll damping was indicated. This vas obtained by doubling the rate-gyro voltage in Round 25, which was also a phase 1 missile. Greatly improved roll stabilization resulted, so the second phase 2 missile was fired as Round 26.

Although considerably improved over the first phase 2 missile, instability was still present and an intensive investigation of the steering circuitry vas undertaken. To verify the aerodynamic and missile dynamic data to be applied in this study, Round 27 was fired with a missile wired for step fin-position commands, in contrast to standard step accelerations, and the resulting transients were to give the necessary information. Round 27 was not adequate for this purpose, however, because of motor and timer malfunctions. Round 28 was then successfully fired for the same objectives.

On the basis of these data and other information obtained in the study, the steering circuits sere redesigned and Rounds 29 and 30 were fired after the changes. These rounds confirmed the general analysis and final remedy was tested in Rounds 31, 31, and 33 during May 1949 (see Table 4 of Appendix 5). The remedy consisted of a refinement of the ram pressure responsive attenuator in the servo circuit, not only in the roll control system but henceforth also in the suitably changed shaping network of the steering order circuit.³⁵

NIKE 48-2 Test Series

Another part of the 1948 NIKE missile program comprised the development and test of the NIKE 48-2 missile, a revised aerodynamic design. During the NIKE design studies early in 1948, trajectory computations indicated that, to obtain optimum range, the effective main fin area of the missile should be reduced by one-third. This conclusion was applied in the new fin design for the NIKE 48-2, and in addition, the fin thickness

was reduced from 6% to 2.5% to decrease wave drag. Revisions to provide space for larger warheads were also made in the fuselage design, including an increase in length from 235 to 255 inches, changing the shape of the after-body from a boat-tail to a cylindrical shape, and attachment of an external tunnel fairing along the body to house electrical wiring and plumbing lines.³⁶ Four dummy missiles of this configuration were fired in August and September 1948 (see Table 5, Appendix 5).

During June and July, however, tests of a 7.5% scale model in the APG supersonic wind tunnel indicated that the NIKE 48-2 possessed unsatisfactory stability and roll characteristics. These tests resulted in several major configuration changes, such as returning to the original fin area, decreasing the distance between the control fins and main fins, and installing four small tunnels instead of the single large tunnel. This modified version, now known as the NIKE 484, vas assigned for steering and roll tests to be conducted in 1949.³⁷

Ancillary Activities
System Tester. At Whippany the design and construction of the Analog System Tester had proceeded to the point where many of the computer components had been thoroughly bench tested. The target simulator part of the machine was essentially completed. When supplemented by parts simulating missile aerodynamics, it was pressed into service as a missile trajectory computer which took over in a more versatile and rapid manner the sort of tasks which had bean preliminarily fulfilled by the improvised trajectory plotter made in Santa Monica in 1947.

Planning Conferences. The sixth planning conference was held at WSFG, in September l948 during the Phase l and 2 overlap. The seventh conference followed in March 1949 at Santa Monica during the recess in the firing program while changes were made in the missile which led to the successful conclusion of Phase 2 in May 1949. In these conferences the status of progress was reviewed and plans were mapped out for the field program of Phases 3 and 4 scheduled for the winter of 1949-50, and for a comprehensive 490 series of firings to be scheduled for the second half of 1950, realizing that various improvements developed in the meantime would require proof testing. This would move the complete NIKE System Trials into 1951, which fumed out to be the earliest year in which radar, computer, targets, and accessories could be ready for them.³⁸

The monopulse radar successfully tracked all missiles from the launcher, through boost and separation, and in many cases to impact. Missiles fired into clouds or at night were tracked without difficulty, demonstrating the all weather reliability of the guidance system. Several missiles were controlled manually toward a ground target location and the communication system functioned satisfactorily down to very small angles of elevation.³⁹

Computer

Having reached the stage of a frozen circuit design, the detail design of the NIKE Computer and the construction of its components progressed rapidly. A considerable amount of equipment had already been completed and was in the process of being tested as individual components. work was concentrated on the construction of modulator amplifiers, demodulators, switching amplifiers, and on the testing and improvement of components. Manufacture of the data receiver and the synchro-data-transmission units, with their precision potentiometers and extensive gearing, entered the final stage with every indication of meeting the stringent accuracy requirements.

Effort was also directed toward the electrical design of associated test equipment. Of primary concern here was the so-called "test bay" containing sufficient facilities to check overall computer operation on a test problem basis in the field. Additional portable equipment was to be designed for general maintenance of the computer.⁴⁰

Missile

An analysis of available flight test data indicated that steering response and roll behavior should be adequate under all significant conditions with the recently revised control circuits providing ample damping. New IBM Fourier techniques were developed to compute the transient behavior of the missile in acceleration controlled test flights. These calculations and the flight test success to date created sufficient confidence for the planned Phase 3 series of tests to be skipped and the limited number of test missiles better exploited. Good agreement of flight test stability measurements with wind-tunnel observations was secured. Despite the stability-maneuverability dilemma brought on by the non-linear moment characteristic in the transition from small to large angle of attack, an acceptable compromise was sought and eventually found by shifting the center of gravity farther aft in the missile.

Several changes were made in the missile. The interior equipment was repackaged for better accessibility and space utilization; the three oil accumulators were manifolded to insure that all control components would remain operative together; and some changes were made in the telemetry system to adopt more shockproof and more linear transducers, improved sampling commutators, and finer ram pressure gauges. The ram pressure probe was embodied in a new nose spike-type telemetry antenna. Wind tunnel tests trying out ailerons with various types or aerodynamic balance features designed to reduce the hinge moments and thus to conserve oil, led to a compromise solution for the simple trailing edge aileron configuration. To provide some of the ballast needed on non-warhead missiles, the main fins were machined from solid aluminum alloy.

In an effort to avoid premature motor stalling when transverse or negative accelerations cause propellant liquid to surge or slash and uncover the tank outlets, several designs of conical internal hoppers and flexible bladders, which would keep the outlets covered until all fuel was exhausted, were developed and tried under laboratory and test stand conditions. The answer to the minimization of eccentric thrust was eventually found in rigorous control of nozzle manufacture and alignment. The only other change introduced in the power plant structure was in the tank configuration. The propellant and air tanks were made into an integral unit.

Launcher

Many improvements and additions were made to the launching equipment, including an experimental, extremely light, portable monorail launcher. Although the original monorail launcher weighed only 5,000 pounds, an effort was made to develop one that would be extremely light so that it could be readily transported by air and assembled by manpower alone. Such a launcher was actually built. By virtue of efficient design and extensive use of aluminum alloy, the overall wight, excluding ballast boxes, was reduced to 2,050 pounds. A demonstration proved that the components could be satisfactorily handled by an eight-man crew, requiring less than ten minutes to unload and assemble the launcher. however, the lightweight model was considerably more expensive than the standard model; it was stored after having been used for only a few test firings.⁴¹

NIKE 484 Test program

Although the NIKE 484 field tests were primarily intended to demonstrate missile behavior under severe and complex pitch and yaw command conditions, they served a number of secondary purposes dictated partly by necessity, partly by opportunity. They did indeed demonstrate NIKE to be a true guided missile, remotely controllable from the ground, thus proving the command guidance link of the missile-tracking radar with the beacon and order transmission links over the monopulse radar beam. The sixteen missiles gave further proof of the suitability of the present configuration, components, structure, and methods of construction. Several variations were introduced which indicated the feasibility and desirability of moving the center of gravity closer to the center of pressure, and of starting the sustaining motor after booster separation.⁴² A detailed outline of test results is given in Table 6 of Appendix 5.

In general, roll stabilization of the missiles was very good and at times excellent. Telemetering records and radar tracking indicated that the missile received and accurately executed all commands. But these results were not accomplished without incidents and problems. For instance, it was found that first order dynamic structural bending vibrations of the missile body at about 20 cycles per second (cps) were being sensed by the control accelerometers and rate gyros, thus catastrophically upsetting the response of the missile to control orders. This trouble was finally eliminated by relocating the accelerometers closer to a node and inserting attenuation at 20 cps in the rate gyro circuit. Another unforeseen problem was encountered with some of the control valves, which functioned erratically and caused some intermittent control discontinuities. Several circuit changes and the establishment of proper oil cleanliness procedures were necessary to eliminate this difficulty.

Figure 11. NIKE Missile 484-50 in Launcher (WSPG, 20 Apr 50)

In four of the last five rounds, the low-power klystron beacon was replaced by a new, more powerful magnetron beacon with gratifying results. Round 43 was deliberately guided through the transonic phase and for a considerable time in the subsonic regime with satisfactory response in pitch and yaw.

Several rounds were launched from the new portable lightweight monorail launcher which gave excellent service. launch, boost, and separation from the single booster were successful in all cases. One round carried a new angle of attach meter which provided aerodynamic stability data confirming wind-tunnel measurements. Designed to give an accurate measurement in subsonic, as well as supersonic flight, the new instrument was developed by DAC, in conjunction with G. M. Giannini & Company. It telemeters the angles of pitch and yaw.

The 484 field tests proved that the prototype design was satisfactory and that it could be scaled down by a third without impairing its accuracy. This change favorably increased the frequency response and was therefore incorporated in a subsequent model which was carried by many of the NIKE 490 series missiles.⁴³

Planning Conference

The eighth planning conference, held at WSPG late in March 1950, concerned itself, first, with a digest of flight test results as far as they had accrued; and second, it considered conclusions and recommendations for the next phase of the test program. The then remaining six 484 missiles were to bracket all parameter ranges and insure proof of proper roll and steering control at high altitudes and low dynamic pressures or wherever else it may be critical. Of the next series of missiles to be produced-and designated as Model 490--another batch of at least sixteen was to be assigned to a precise performance test program in 1950 before embarking upon the official NIKE system trials in 1951. All of these tests had to be scheduled and interspersed with the activities required on behalf of the development of the tactical version NIKE I.⁴⁴

A second computer, to be retained for use in the laboratory system tester, was in the final wiring and preliminary testing stage. The test bays, to be associated with both computers for checking purposes, were in process of construction.⁴⁵

Missile

Based on observations made during the previous (484) test series, a number of changes were introduced in the missile structure, which became identified as the 490 family. Some of the innovations were prompted by the desire to improve performance and facilitate production, while others were intended to eliminate difficulties previously experienced. The most important of these changes are briefly described below.

1. The sustainer motor was started after separation to provide increased range and to simplify and lighten the booster~missile support sleeve.
2. The center of gravity of the missile was placed closer to the dynamic balance point (or center of pressure) to inprove aerodynamic response (or supersonic maneuver capabilities).
3. Beacon antennas for reception and transmission were separated to simplify waveguide components.
4. Electronic components were repackaged to provide greater ease of adjustment.
5. Manufacturing tolerances on the hydraulic control valves were eased to facilitate production.
6. A new type of composite fin construction was used to facilitate production, save fifty pounds in weight, and give a smaller moment of inertia.
7. Two of the test missiles were equipped with experimental bladder-type propellant tanks in an effort to obtain continuous and complete expulsion of liquid fuels.

In general, the changes noted in items 1 through 4, above, gave very satisfactory results. The other changes, however, resulted in difficulties. While the delayed starting of the sustainer motor (item 1) was satisfactory for all intents and purposes of the test, it added the complication of short motor burning time. This early burnout--noted in all but one of the first ten firings-was attributed to the bursting of propellant (acid line) diaphragms during boost acceleration and the consequent loss of oxidizer (acid) prior to motor ignition. The two flight tests conducted with the bladder-type propellant tanks (item 7) were unsuccessful because of sealing difficulties (oxidizer bladder unable to withstand negative accelerations at the end of boost). This approach was abandoned in favor of a fixed hopper-type tank structure which worked satisfactorily in later firings. Early in the program, it became apparent that the other two changes introduced in the 494 missile were causing a recurrence of certain roll and steering oscillations which had been eliminated during the 484 test series. Specifically, the change in the hydraulic control valves (item 5) gave a persistent 2-cps oscillation in the steering circuits; and the decreased moment of inertia (item 6) resulted in loose roll control which network changes failed to eliminate completely. While these oscillations did not significantly impair the missile control, they seemed to be wasteful of hydraulic oil and they prevented the gathering of clear-cut aerodynamic performance data.

Even though the objectives of the 1950 firing program had not been fully achieved, the program was discontinued with the firing of the tenth missile (Round 59) in December 1950, so that the information already available could be studied in more detail and necessary modifications accomplished. The ten missiles fired in the fall program exhibited satisfactory launch, boost, separation, and motor ignition. With a few minor exceptions, the radar tracking and command link performed in a very satisfactory manner. Detailed results of these ten firings are given in Table 7 of Appendix 5.⁴⁶

The first three months of 1951 were devoted to the elimination of trouble sources and modification of the remaining six 490A missiles, which were to be launched as a part of the Spring Supplementary Firing Program. The hydraulic valves were thoroughly tested and then redesigned, reducing the valve plunger port overlap ratio as much as possible and thus reducing the non-linearity of valve characteristics. Changes were also made in the electrical network to increase the gain margin at large phase angles. Hydraulic fin locks for the launching period aid not perform any more positively than zero g steering orders and were therefore discarded after the fall tests in favor of the latter method. The roll control circuitry was changed to make the servo gain a function of dynamic pressure and thus tighten up the control to overcome troubles attributed to the small roll moment of inertia. To prevent loss of oxidizer during boost and thus insure normal motor burning time, a new propellant control valve, with inter-linked burst diaphragms, was developed for the acid-aniline motors. Be an alternative, three of the six NIKE 490A missiles were equipped with experimental acid-gasoline power plants.⁴⁷ Some of the supplementary test rounds were also equipped with arming devices and fuzes, the proper function of which was demonstrated by telemetry and by detonation of an explosive spotting charge. These arming devices, designated as Type T93, had been developed by Frankford Arsenal and tested in the laboratory. The spotting charge was designed to supply a burst indication for those system test missiles which were not to carry live warheads. It consisted essentially of a smoke-producing explosive contained in a tube which extended across the center warhead compartment. Both ends of the charge were ignited simultaneously to give a visible smoke puff and thus simulate a warhead burst.⁴⁸

The NIKE 490A Supplementary Firing Program (Rounds 60 through 65) began an 12 April 1951 and continued intermittently through 14 July 1951. It was primarily designed to prove the various remedies noted above, with secondary objectives of testing alternatives and accessories, preparatory to the first R&D system tests in October 1951 These field tests were very disappointing, to say the least. Test objectives were successfully achieved in only two of the rounds; the other four were marred by component failures, chiefly in the control system. A brief account of these field tests is given below. (For further details, see Table 8 of Appendix 5.)

The first two rounds (60 and 61) were fired primarily to test the effectiveness of modifications made in the acid-aniline power plant system to insure full duration of motor burning. Secondary objectives were to test the Frankford arming device and spotting charge. Both rounds made satisfactory flights. Burning times were normal and there was no indication of propellant loss during boost. The Frankford arming devices and spotting charges operated satisfactorily.⁴⁹

Round 62 was flown with the control system fully operable to demonstrate revisions made in the control network, and to test the acid-aniline power plant system under maneuvering conditions. A high frequency oscillation in the pitch and yaw steering channels caused the malfunction of this round. Except for some sporadic burning just before burnout, the missile motor continued to operate satisfactorily during the oscillations.

The primary objective of Round 63 was to test the new acid-gasoline power plant system in flight. It was frustrated by an explosion during the starting phase. No repetition of this experiment could be scheduled during the R&D Program; however, the obvious advantages of a missile motor burning a fuel that would be readily available almost anywhere remained as an incentive.

Rounds 64 and 65 were flown to test further revisions in the central network, as well as changes made in the acid-aniline power plant system to correct hard start conditions noted in earlier rounds. In Round 64, a malfunction occurred before separation (missile lost propellants and had sporadic motor burning during boost), resulting in erroneous command acceleration levels. In Round 65, the booster and power plant operation was normal during launch phase: however, a malfunction occurred in the missile at take-off, causing an unbalance of the control signal. Difficulties experienced in both of these rounds were attributed to component failures in the control system.⁵⁰

The component development and proof test phase of the NIKE project was scheduled to end with the last 490A missile firing (Round 65) in July 1951, and demonstration of the complete R&D System was to begin with the firing of Round 66 (490B series) in October 1951. However, the latter 490A test results clearly showed that complete reliability of all control system components still had not been achieved, and that further modifications and supplementary field tests would be required in order to preclude the recurrence of malfunctions during R&D System firings against drone targets. The necessary control circuit modifications were later completed and successfully tested in Round 66 on 16 October 1951.

The NIKE missile was now ready for the supreme test--firing against drone aircraft.

{----- end of chapter 3}

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