Model, Sabot Design and Free-Flight Tests of the DRDC-ISL A1, A2 and A3 Models

Model, Sabot Design and Free-Flight Tests of the DRDC-ISL A1, A2 AND A3 Models

A. Dupuis M. Boivin DRDC Valcartier

M. Normand MAETEC

Defence R&D Canada – Valcartier Technical Memorandum DRDC Valcartier TM 2003-077 July 2003 Copy No:______

Model, Sabot Design and Free-Flight Tests of the DRDC-ISL A1, A2 and A3 Models

A. Dupuis DRDC-Valcartier M. Normand MAETEC M. Boivin DRDC-Valcartier

Defence R&D Canada Valcartier Technical Memorandum TM 2003-077 2003-07-22 Author

A. Dupuis

Approved by

E. Fournier Head, Precision Weapons Section

Approved for release by

E. Fournier Head, Precision Weapons Section

Terms of release: The information contained herein is proprietary to Her Majesty and is provided to the recipient on the understanding that it will be used for information and evaluation purposes only. Any commercial use including use for manufacture is prohibited. Release to third parties of this publication or information contained herein is prohibited without the prior written consent of Defence R&D Canada.

Preliminary free - flight tests were conducted to verify the integrity of sabots and the A1, A2 and A3 DRDC-ISL model configurations launched from a powdered gun in the velocity range of 200 to 1400 m/s. Projectiles of each configuration were fired as well as a series of slugs for charge determination. The propellant charge mass, muzzle velocity, maximum accelerations and drag coefficient were determined for each shot when fired from a 110-mm smooth bore gun and a 105-mm rifled one with and without a high-low pressure chamber adapter.

Résumé

Des essais préliminaires ont été effectués pour vérifier le bon fonctionnement des concepts de sabots et des modèles RDDC-ISL A1, A2 et A3 tirés d’un canon à poudre dans la gamme de vitesses situées entre 200 et 1400 m/s. Des projectiles de chaque configuration ont été lancés ainsi qu’une série de balles noyaux pour déterminer les chargespropulsives.Onadéterminéachargepropulsive,lesvitessesàlabouchedu canon, les accélérations maxima et les coefficients de traînée pour chaque tir d’un canon de 110 mm à âme lisse et de 105 mm rayé avec ou sans adaptateur de pression haute-basse situé dans la chambre du canon.

TM 2003-077 i This page intentionally left blank.

ii TM 2003-077 Executive summary

Many options are being considered to improve the performance of existing weapons systems. For example, increasing the range of artillery shells beyond the actual range of 40 km and providing them with some maneuverability on the battlefield to enhance the hit probability on selected high threat targets could be of great advantage to the Canadian Forces. The use of novel controls on missiles as, for example, lateral jets, lattices fins and thrust vector control could increase their performance over classical control surfaces. The available information on how such modifications could improve the aerodynamic performance over the classical projectile or missile shapes is rather limited.

As part as a joint effort between DRDC and the French German Institute under the auspices of the Franco-Canadian Accord, a project was set up to study the flight dynamic behavior of a very long range artillery shell with wings and of lattice finned controls on a missile body. The objective was to conduct a fundamental study of the aerodynamic phenomena associated to these type types of control surfaces, their maneuverability, and to compare the results with those furnished by other means such as lateral jets, impulse systems and classical planar control surfaces. Various methodologies available to each establishment such as simulations tools to predict the aerodynamics (CFD and semi-empirical/analytical), and experiments (wind tunnel, aeroballistic range and open range tests) would be utilized in a complementary fashion to avoid duplication of effort.

This memorandum presents the projectile and sabot designs as well as the preliminary free-flight trials that are required prior to aeroballistic range firings. The intent of these trials was to conduct a charge determination, to verify the model-sabot integrity at launch and the projectile stability of the models so as not to damage the aeroballistic range instrumentation. Projectiles were fired from a 110-mm smooth bore and a 105- mm rifled gun with and without a Hi-Lo adapter. The propellant charge mass, muzzle velocity, maximum acceleration and drag coefficients were determined for each shot.

Dupuis, A., Normand, M., Boivin, M,. 2003. Model, Sabot Design and Free-Flight Tests of the DRDC-ISL A1, A2 and A3 Models. TM-2003-077 Defence R&D Canada Valcartier.

TM 2003-077 iii Sommaire

Plusieurs options sont entrain d’être examinées pour améliorer la performance des systèmes d’armes existants. Par exemple, augmenter la portée d’un obus d’artillerie au-delà des 40 km actuels en leur donnant une certaine manœuvrabilité sur le terrain pour accroître la probabilité de frappe sur certaines cibles menaçantes pourrait représenter un avantage énorme pour les Forces canadiennes. L’utilisation de contrôles novateurs sur des missiles, comme, des jets latéraux, des ailettes en treillis et de contrôle de la poussée vectorielle pourraient augmenter leur performance sur les surfaces de contrôle classiques. L’information disponible pour comprendre comment ces modifications pourraient améliorer la performance aérodynamique sur les projectiles et missiles classiques est très limitée.

Dans un effort conjoint entre le RDDC et l’Institut de recherches franco-allemand sous les auspices de l’Accord franco-canadien, un projet a été amorcé pour étudier la dynamique du vol d’obus d’artillerie de très longue portée avec des surfaces portantes et des ailettes en treillis sur un corps de missile. L’objectif était l’étude fondamentale des phénomènes aérodynamiques associés à l’usage de ce type de gouverne, leur pilotage par l’utilisation des connaissances nouvelles acquises et la comparaison des résultats obtenus avec ceux fournis par d’autres moyens conventionnels de pilotage tels que jets latéraux, dispositifs impulsionnels et surfaces portantes classiques. Des méthodologies existantes aux deux centres de recherche comme les outils de prédiction de coefficients aérodynamiques (calculs numériques et semi- empiriques/analytiques) et les moyens expérimentaux (soufflerie, corridor aérobalistique et champs de tirs) ont été utilisés d’une façon complémentaire pour éviter la duplication des travaux.

Ce mémorandum présente la conception des sabots et des projectiles ainsi que les essais préliminaires requis avant d’effectuer des essais au corridor aérobalistique. Le but de ces essais était de déterminer la charge propulsive, vérifier l’intégrité du modèle et du sabot lors du lancement et de la stabilité des modèles en vol afin de ne pas endommager l’instrumentation du corridor aérobalistique. Les projectiles ont été tirés d’un canon 110 mm à âme lisse et d’un canon de 105 mm rayé, avec ou sans un adaptateur de pression haute-basse, situé dans la chambre du canon. La charge propulsive, les vitesses à la bouche du canon, les accélérations maxima et les coefficients de traînée ont été déterminés pour chaque tir d’un canon.

Dupuis, A., Normand, M., Boivin, M. 2003. Model, Sabot Design and Free-Flight Tests of the DRDC-ISL A1, A2 and A3 Models. TM 2003-077 Defence R&D Canada Valcartier.

iv TM 2003-077 Table of contents

Abstract/Résumé ...... i

Executive summary...... iii

Sommaire ...... iv

Table of contents ...... v

List of figures ...... vii

Acknowledgements ...... x

1. Introduction ...... 1

2. Projectile Configuration ...... 2 2.1 Model A1 - Artillery Shell with Wings ...... 2 2.2 Model A3 - Missile with Grid Fins...... 2 2.3 Model A2 - Artillery Shell with Grid Fins...... 3

3. Experimental Site and Instrumentation...... 4 3.1 Test Particularities ...... 4

4. Model, Sabot Design and Tests for A1 Model...... 6 4.1 Model Design for A1 Configuration...... 6 4.2 Sabot Design for A1 Model ...... 7 4.3 Sabot-Model Integrity Trials 1 (Oct. 99) for A1 Model ...... 8 4.3.1 Comments and Discussions ...... 10 4.4 Sabot-Model Integrity Trials 2 (July 00) for A1 Model ...... 10 4.4.1 Comments and Discussions ...... 11 4.5 Sabot-Model Integrity Trials 3 (Nov. 00) for A1 Model ...... 12 4.5.1 Comments and Discussions ...... 13 4.6 Final Sabot Design for A1 Model...... 14

5. Model, Sabot Design and Tests for A3 Model...... 15 5.1 Model Design for A3 Configuration...... 15

TM 2003-077 v 5.2 Sabot Design for A3 Model ...... 15 5.3 Sabot-Model Integrity Trials 1 (Oct. 99) for A3 Model ...... 16 5.3.1 Comments an Discussions ...... 17 5.4 Sabot-Model Integrity Trials 2 (July 00) for A3 Model ...... 17 5.4.1 Comments and Discussions ...... 18

6. Model, Sabot Design and Tests for A2 Model...... 19

7. Conclusions ...... 20

8. References ...... 21

Annex A - Measured Roll Orientations...... 62

List of symbols/abbreviations/acronyms/initialisms...... 66

Distribution list...... 67

vi TM 2003-077 List of figures

Figure 1. Model A1 - Artillery shell concept with wings (all dimensions in caliber, 1 cal = 30 mm)...... 23

Figure 2. Model A3 - Grid finned projectile (all dimensions in caliber, 1 cal = 30 mm) ...... 24

Figure 3. Model A2 - Artillery shell concept with grid fins (all dimensions in caliber, 1 cal = 30 mm)...... 25

Figure 4. Schematic of the test site ...... 26

Figure 5. Photograph of test set up ...... 27

Figure 6. Hi-Lo 110 mm chambre adapter...... 28

Figure 7. Schematics of A1 projectile design ...... 29

Figure 8. Sabot schematic for the A1 projectile...... 30

Figure 9. Photograph of sabot package for A1 model ...... 30

Figure 10. Photographs of A1 sabot pieces...... 31

Figure 11. Sabot schematic for the slug for A1 model ...... 32

Figure 12. Velocity and acceleration history for Slug SLA1-3...... 32

Figure 13. Sabot separation for A1 model - Shot A1-08, VMUZ = 240.0 m/s...... 33

Figure 14. Photographs of recovered sabot pieces for A1 model ...... 34

Figure 15. Photograph of recovered polycarbonate section...... 35

Figure 16. Modified sabot schematic for the A1 projectile - July 00...... 36

Figure 17. Photograph of modified sabot package for A1 model - July 00 ...... 36

Figure 18. Sabot separation for A1 model - Shot A1-24, VMUZ = 218.1 m/s...... 37

Figure 19. Sabot separation for A1 model - Shot A1-22, VMUZ = 215.7 m/s...... 37

Figure 20. Sabot separation for A1 model - Shot A1-25, VMUZ = 215.0 m/s...... 38

Figure 21. Sabot separation for A1 model - Shot A1-23, VMUZ = 212.7 m/s...... 38

Figure 22. Sabot separation for A1 model - Shot A1-31, VMUZ = 233. m/s...... 39

TM 2003-077 vii Figure 23. Sabot separation for A1 model - Shot A1-33, VMUZ = 233.6 m/s...... 39

Figure 24. Sabot separation for A1 model - Shot A1-32, VMUZ = 213.8 m/s...... 40

Figure 25. Sabot separation for A1 model - Shot A1-34, VMUZ = 208.9 m/s...... 41

Figure 26. Schematic of final design for the A1 projectile...... 42

Figure 27. Photograph of A3 projectile with brass nose...... 43

Figure 28. Sabot schematic for the A3 projectile...... 44

Figure 29. Photograph of sabot package for A3 model ...... 44

Figure 30. Sabot separation for A3 model - Shot A3-03, VMUZ = 859.4 m/s...... 45

Figure 31. Sabot separation for A3 model - Shot A3-05, VMUZ = 1173.1 m/s...... 45

Figure 32. Photograph of sabot package for A3 model - July 00...... 46

Figure 33. Sabot separation for A3 model - Shot A3-21, VMUZ = 1158.4 m/s...... 47

Figure 34. Photograph of A2 projectile ...... 48

Figure 35. Sabot schematic for the A2 projectile...... 49

Figure 36. Photograph of sabot package for A2 model ...... 49

List of tables

Table 1. Firing Conditions for A1 model - Trial 1 (Oct 99) ...... 50

Table 2. Results from gun firing for 3.25 slugs (Oct 99)...... 50

Table 3. Measured physical properties of A1 projectiles (Oct. 99) ...... 51

Table 4. Results from gun firing for A1 Model - Trial 1 (Oct 99)...... 52

Table 5. Measured physical properties of A1 projectiles (July 00) ...... 53

Table 6. Firing Conditions for A1 model - Trial 2 (July 00) ...... 53

Table 7. Results from gun firing for A1 Model - Trial 2 (July 00)...... 54

Table 8. Deduced drag coefficient for A1 Model - Trial 2 (July 00)...... 55

viii TM 2003-077 Table 9. Measured physical properties of A1 projectiles (Nov. 00) ...... 55

Table 10. Firing Conditions for A1 model - Trial 3 (Nov 00) ...... 55

Table 11. Results from gun firing for A1 Model - Trial 3 (Nov 00)...... 56

Table 12. Deduced drag coefficient for A1 Model - Trial 3 (Nov 00)...... 56

Table 13. Measured physical properties of A3 projectiles (Oct. 99) ...... 57

Table 14. Firing Conditions for A3 model - Trial 1 (Oct 99) ...... 57

Table 15. Results from gun firing for A3 Model - Trial 1 (Oct 99)...... 58

Table 16. Deduced drag coefficient for A3 Model - Trial 1 (Oct 99)...... 58

Table 17. Measured physical properties of A3 projectiles (July 00) ...... 59

Table 18. Firing Conditions for A3 model - Trial 2 (July 00) ...... 59

Table 19. Results from gun firing for A3 Model - Trial 2 (July 00)...... 60

Table 20. Deduced drag coefficient for A3 Model - Trial 2 (July 00)...... 60

Table 21. Measured physical properties of A2 projectiles (Oct 99) ...... 61

Table 22. Results from gun firing for 2.2 kg slugs (Oct 99)...... 61

TM 2003-077 ix Acknowledgements

The authors would like to thank ISL for the fabrication of the models that were utilized for the trials as well as Drs. V. Fleck and C. Berner of ISL for their many discussions on the design of the A1 model for the aeroballistic range tests. Thanks are also due to the CEEM-V trials team for the successful completion of these tests.

x TM 2003-077 This page intentionally left blank.

TM 2003-077 xi

1. Introduction

The Defence Research and Development Canada (DRDC) - Valcartier and the French- German Research Institute (ISL), in Saint-Louis, France, agreed, under the auspices of AS 14 of the Franco-Canadian Accord, to conduct an extensive experimental and computational investigation on three projectile configurations. Both research establishments have wind tunnels, aeroballistic range facilities, open ranges and computational fluid dynamic (CFD) means to determine the aerodynamic characteristics and the stability of any projectile configuration. The aim was to use a triangular exploration (wind tunnel, free-flight and computational) to reduce as much as possible the number of required aerodynamic tests, which tend to be quite expensive. Every effort was made to use the available tools at both establishments, in a complementary fashion rather than duplicative, to maximize the efficiency.

Many options are being examined by both research establishments to improve the performance of existing weapons platforms or by investigating novel technologies that could be used with present systems by increasing their current capabilities. One example consists in increasing the range of artillery shells beyond 40 km by using deployable wings during the flight, and by providing them with some maneuverability on the battlefield. This would enhance the hit probability on selected high threat targets, or if a type of visual system could be mounted in the shell, it could also be used as an observing stage. The use of lattice, or grid, fins could increase the performance of missiles over classical aerodynamic control surfaces to improve maneuvering capability at high angles of attack. The available information on how such modifications would improve the aerodynamic performance over the classical projectile or missile shapes is rather limited. Before characterizing any enhancements, it is necessary to provide detailed and reliable information on reference test cases so as to be able to quantify any improvements over the classical projectile.

The objective of this investigation was to design the projectiles and the sabots to launch them, as well as to conduct the necessary trials that are required prior to aeroballistic range tests at DRDC-Valcartier. The intents of these trials were to conduct a charge determination, to verify the model-sabot integrity at launch and the projectile stability of the models so as not to damage the aeroballistic range instrumentation. The projectile configurations were fired from a 110-mm smooth bore and a 105-mm rifled gun with and without a Hi-Lo adapter. One configuration consisted of an idealized 155 mm shell with wings and one with grid fins while the third one was a missile body with grid fins. The propellant charge mass, muzzle velocity, maximum acceleration and drag coefficients were determined for each shot.

This study was conducted as part of a cooperative research program between DRDC and ISL under the auspices of AS-14 entitled “Projectiles et missiles pilotés par ailettes en treillis” of the Franco-Canadian Accord. This work was performed at DRDC Valcartier between October 1999 and November 2000 under Work Unit 3eb12, Flight Dynamics for Missile Performance Studies.

TM 2003-XX 1 2. Projectile Configuration

2.1 Model A1 - Artillery Shell with Wings

The usual method to increase the range of an artillery projectile is to reduce the drag through the use of devices such as a base bleed units or rocket-assist. This type of devices permits to extend the range of a standard 155 mm shell in the range of 30-40 km. The use of the lift force in order to compensate the gravity force acting on the projectile is another concept for obtaining an equivalent or an augmented range of actual 155 mm projectiles. This solution requires that the projectile fly with an upward directed angle of attack for a very long range and to maintain a lift to drag ratio. A spinning projectile flies during a great part of its trajectory with an angle of attack (yaw of repose). The orientation and the magnitude of this angle depend, beside other parameters, on the moment of the aerodynamic force. This moment can be used to control the angle of attack, or the yaw of repose.

A previous study [1] has shown the feasibility of using the yaw of repose in an astute fashion to maintain a continuous angle of attack in order to increase the range of an artillery shell. That study only reported on results obtained for an idealized artillery projectile configuration with and without lifting surfaces. An optimized configuration of a 155mm spinning artillery shell with canted lifting surfaces located slightly downward the center of gravity is shown in Fig. 1. Critical aspects were the center of pressure location, the angle of cant of the fins and the spin rate. The Mach number range of interest lied between 0.6 and 0.8.

The final projectile configuration that was chosen for the study is shown in Fig. 1. It consisted of a secant-ogive-cylinder projectile with an l/d of 5.65 representative of a typical 155 mm shell (Fig. 1a). The four straight profiled fins located at 1.9 cal from the base have a total span of 3.0 cal and a chord of 0.5 cal. The fins cants were modified for the different trials and this will be discussed in a further section. The ogive length was 3.00 cal with a radius of 10.12 cal and a meplat of 0.088 cal.

The fins were profiled (Fig. 1b) at a radius of 1.264 cal with a mid span thickness of 0.053 cal. The leading and trailing edges were rounded at a radius of 0.002 cal. The free-flight models were 30.0 mm in diameter. The centre of gravity positions as well as the physical properties will be provided in later sections when discussing the design of the models.

2.2 Model A3 - Missile with Grid Fins

The use of grid fins as a stabilization and control device on projectiles and missiles offers an interesting alternative to the classical fin design. Their easy storage for deployment, low hinge moments and high angle of attack performance are their main advantages while their main shortcoming is a higher drag penalty [2]. The projectiles studied [2] had an l/d of 16 with very thin webbed lattice fins oriented in a X shape.

2 TM 2003-077 For this project, it was decided to simplify the configuration as much as possible so that detailed measurements around the fins could be conducted with ease and to make sure that they could be fired at high velocities, up to Mach 4.0. Previous free-flight tests were not successful at high velocities due to structural failure of the lattice fins.

The projectile configuration that was retained for this joint project is shown in Fig. 2. The reference configuration was the Air Force Finner [3] body equipped with four grid fins, as shown in Fig. 2a. The body consisted of a 2.5 caliber tangent-ogive followed by a 7.5 caliber cylinder. The fins were placed at 0.7 calibers from the base. The total span is 2.4 calibers with a chord of 0.08 calibers. These last dimensions and placements were typical of missiles systems that were studied based on a literature survey on the data that was available at that time. The reference diameter for the free- flight models was 30.0 mm.

The grid fin, presented in Fig. 2b, has nine cells with thick walls. Thick walls were chosen to allow wind tunnel static wall pressure measurements on the central cell. This grid fin geometry, contrary to many other papers [2, 4-8], has a vertical cell orientation instead of a cruciform one. This was done to simplify the geometry to be able to understand basic aerodynamic phenomena of simple cells. Each cell is rectangular with a width of 0.124 caliber and a height of 0.161 caliber. In order to avoid possible structure deficiencies during free-flight tests, a solid base was designed to mount the fins on the body. One set of fins was canted at 2.0° to provide a spin rate and one set was deflected at 0.5° to provide a trim angle.

This configuration was tested at two different center of gravity positions and these will be detailed in a later section. The Mach number of interest for this configuration was from 0.6 to 4.0.

2.3 Model A2 - Artillery Shell with Grid Fins

As mentioned previously, the concept for the artillery shell with wings uses an astute control of the yaw of repose to maintain an ideal angle of attack to increase the range. For this to occur using this principle, the center of pressure has to be moved in flight fore and aft the center of gravity. To displace the center of pressure aft of the center of gravity, one design concept was to investigate the use of deployable grid fins at the aft end of the artillery shell, which would be controlled by the autopilot during flight.

The projectile configuration is shown in Fig. 3. The projectile body (Fig. 3a) is the same as Model A1 and the grid fins (Fig. 3b) are the identical to the ones of the A3 model, as well as their placements on the model. In this case, the center of gravity was to be tested at one position and it was located at 3.43 cal from the nose of the projectile. The reference diameter of the projectile for the free-flight tests was also 30.0 mm and the Mach number range of interest was subsonic, i.e. in between 0.6 to 0.8. The fins were also canted in the same manner as Model A3. The models were made of steel.

TM 2003-077 3 3. Experimental Site and Instrumentation

The integrity trials were conducted at two sites at DRDC-V. The first series of trials took place at Butt 4 and the remaining ones one took place at the 2000 m precision range. The trial set up was basically the same at both test sites with minor modifications. A schematic of the test set-up is shown in Fig. 4. A sabot trap was installed at approximately 9.2 m from the gun muzzle to duplicate the launch configuration at the aeroballistic range. This is particularly important for the sabot petal separation. Two high-speed photographic stations were positioned fore and aft (6.3 m and 11.5 m from the gun muzzle) of the sabot trap to photograph the sabot separation and model integrity. A target was situated at 150 m from the muzzle. Also, two packs of yaw cards were installed at 20 m and 30 m from the muzzle. This consisted of three yaw cards separated by 0.5 m. One of the fins of each projectile was painted blue and it was possible to obtain the roll orientation.

Two radars were utilized for these tests. One to obtain the acceleration of the sabot- model package inside the gun tube and a second to obtain the velocity history of the projectile in flight. The detailed configuration and location of the radars are shown in Fig. 4. The acceleration in the gun tube was measured by a continuous Doppler type radar with a transmission frequency of 35 GHz. It was placed behind the gun and aimed at a metalized mylar radar signal reflecting mirror placed in front of the sabot trap. The mirror was located on the side of the firing line to avoid model disturbance or damage, and oriented towards and inside the gun muzzle. The data analysis was then conducted with a Fast Fourier Transform (FFT) analyzer to obtain the velocity and acceleration history inside the gun tube.

The projectile velocity was measured with a continuous Doppler radar with a frequency of 10.492 GHz. This radar was situated passed the sabot trap (at 12.0 m) looking down range and 0.9 m below the line of fire. The projectile’s velocity history and its muzzle velocity were obtained from this radar. The signal processing was conducted with a FFT analyzer.

The chamber pressures were not measured in these trials since enough data was obtained from previous similar trials.

Photographs of the test set can be seen in Fig. 5.

3.1 Test Particularities

It took three sets of trials to finalise the A1 sabot and model design, two for the A3 grid fin model and the A2 model was not fired for reasons that will be explained later. The velocities of interest for the A1 and A2 projectile were of the order 210 m/s while those for the A3 projectile were from 210 m/s to 1360 m/s.

4 TM 2003-077 The A1 model projectile was fired from a 105 mm rifled gun with a twist of 1 turn in 18 calibers while the A2 and A3 projectiles were due to be fired from a 110 mm smooth bore gun. At the low launch velocities of 210 m/s to 350 m/s, a special Hi - Lo adapter (Fig. 6) was utilized in the gun chamber to obtain consistent gun pressures to propel the model-sabots at low repetitive muzzle velocities and to achieve the lowest launch accelerations as possible. Since these muzzle velocities are quite low, a standard 105-mm cartridge would not be suitable. The propellant mass required in a standard cartridge would be too small to obtain adequate uniform burning of the propellant and would lead to inconsistent muzzle velocities. The Hi-Lo adapter fits in the chamber of the 110-mm and 105-mm gun tubes to equalize the pressure in the gun tube

The Hi-Lo adapter comprises several components (Fig. 6): an obturator, a diffuser, a joining shaft, a standard M63 primer, O-ring seals on the adapter and on the diffuser, and an end nut. For these trials, the 9.525 mm diffuser was utilized. Several other diffusers were available but not used in this trial. A propellant charge is placed around the shaft (High pressure section) between the obturator and the diffuser, and it is ignited by the burning gases from the primer escaping the holes in the shaft. The pressure in the gun tube (Low pressure section) is controlled by the escaping gases through the nozzles of the diffuser.

TM 2003-077 5 4. Model, Sabot Design and Tests for A1 Model

4.1 Model Design for A1 Configuration

The model design for the A1 configuration (Fig. 1) was quite a challenge since it had to be fired in two stability conditions. With a center of gravity ( XCG ) aft of the center of pressure ( XCP ), the projectile is statically unstable and it has to be spin stabilized to maintain a gyroscopically stable flight. This implies that the projectile has to be fired from rifled tube and the projectile has to be specifically designed for the aeroballistic range tests. The initial flight dynamic studies [1] were based on a full- scale 155 mm, which do not hold for a scaled 30 mm model. The critical aspects in these cases are the spin rate, the center of gravity position relative to the center of pressure and the lift to drag ratio. The gun tube that was available at DRDC-V to fire such a projectile was the 105 mm rifled gun. It has a twist of 1 turn in 18 calibers.

There was also interest in firing the projectile, from this same gun tube, in a statically stable condition, that is when the XCG is forward of the XCP . The reason for this is that for full-scale operation on a 155 mm shell, as explained earlier, the shell would fly in both stability conditions. The aerodynamic properties are required to be known in thesameregimeofspinrates.

The placement of the wings on the body was fixed as with [1] as shown in Fig. 1, and the aerodynamic coefficients were predicted with four tools, numerical simulations from CFD [1], and with semi-empirical/analytical tools, PRODAS [9], AP95 [10] and DATCOM [11]. The crucial parameter that the projectile had to be designed around was the center of pressure location. An average of the four predicted values was taken and it was fixed at 3.03 cal from the nose. The next step was to conduct a series of six- degree-of-freedom trajectory simulations with PRODAS [9] at various center of gravity positions (which implies modeling the model completely with various material densities) and fin cants to make sure that the projectile would not divert by more than 1.0 m in cross range over a distance of 150.0 m. It should be noted that the available aerodynamic data was very limited, especially the dynamic derivatives, roll damping and roll producing moments due to fin cant. All simulations were conducted at a muzzle velocity of 210 m/s, which yielded an initial spin rate of roughly 700 rad/s. The projectile that caused the most challenge was the gyroscopically stable one.

After many 6DOF simulations, both at DRDC-V and ISL, it was decided to design the gyroscopically stable projectile with the center of gravity located at 93.6 mm (3.12 cal) from the nose of the projectile and the statically stable projectile at 81.5 mm (2.72 cal) from the nose. Both projectiles would have the fins canted at 4.0° so as to maintain the required spin rate to have a gyroscopic stable projectile.

The detailed model designs were then made and sketches of the projectiles can be found in Fig. 7. Due to the amount of detailed drawings only schematics will be shown in this report and the full drawings are available from DRDC-V on a need to know basis. The statically stable projectile is shown in Fig 7a. The steel base portion of the

6 TM 2003-077 model was hollowed to have the center of gravity forward. The nose section was made of a tungsten allow. To obtain the right center of gravity position for the gyroscopically stable projectile (Fig. 7b), which is further aft the other one, the tungsten nose was hollowed out a bit and merged on a full steel base.

4.2 Sabot Design for A1 Model

Since the sub caliber projectiles have to be launched from a powdered gun to conduct tests in the DRDC-V aeroballistic range, special sabots have to be designed to fire them. Since the model configuration in this case was spin stabilized, a rifled gun was utilized. The standard gun employed at DRDC-V to fire spin-stabilized projectiles of these dimensions with sabots in the aeroballistic range is a 105 mm rifled gun.

Several aspects have to be considered when designing sabots and models. They are: projectile configuration, total mass, sabot separation at the sabot trap located at 9.2 m from the muzzle at the aeroballistic range, muzzle velocity desired, gun accelerations, etc. The last three mentioned have to be consistent from round to round. In this case, the muzzle velocity desired was approximately 210 m/s (Mach 0.6).

A schematic of the sabot design to launch the A1 projectile from the 105 mm rifled gun tube is shown in Fig. 8 and a photograph of the sabot package is shown in Fig. 9. It consists of a four solid petal aluminum shell that is split along the same direction as the fin locations. The width of these cuts are the such that the total fin span, at 4.0° cant, has a snug fit and is in contact with both petal surface. The aluminum body is covered with a polycarbonate material, that includes the driving band at the back end, that will protrude in the rifling of the gun tube to transmit the torque to the sabot when fired. The aft section of the aluminum body was roughened with grooves (Fig. 10a) so that the polycarbonate ring (Fig. 10b) does not slip with respect to the aluminum body when fired. The aft end of the sabot as well as the seal were based on a standard sabot to launch an in service 105 mm projectile. Therefore, if the contact between the polycarbonate ring and the aluminum body is successful, the full spin rate will be transmitted to the sabot during launch. The low launch velocity of 210 m/s for this combination was considered to be a possible problem since the petal separation is caused by the centripetal acceleration at the muzzle. This type of sabot, even though successful at muzzle velocities of 1500 m/s, was never tested at these low launch velocities. This also implies that the amount of material along the saw cut lengths at the aft end of the sabot has to be adjusted to make sure that they break evenly to have symmetric petal separation. The sabots were manufactured at DRDC-V while the projectiles were made at ISL. The total sabot-model mass was roughly 3.2 kg.

A roll pin was added at the aft end of the model (Fig. 9) so as to be able to measure the roll orientation of the projectile when conducting tests in the aeroballistic range.

TM 2003-077 7 4.3 Sabot-Model Integrity Trials 1 (Oct. 99) for A1 Model

The main objectives of the trials were: a. verify if the sabots and models could survive the launch loads over the required speed regime, b. confirm adequate sabot separation at the sabot trap, c. assure that the projectiles have adequate stability to reach the target, d. obtain some drag coefficient data over the required speed regime. The propellant charges required to obtain the required muzzle velocities were also obtained. All the tests were conducted with the N-3-1-1 (0.035” web) propellant. This propellant was well suited to obtain the required muzzle velocities of interest with the Hi - Lo adapter.

The results of all the gun launches will be given for each projectile below in individual sections. The accelerations were measured with a radar looking down the barrel through a reflector and only the maxima achieved are reported. The muzzle velocities from the radar aimed inside the bore and the one looking downrange are also provided.

The drag coefficient was determined for each stable projectile from the Doppler velocity radar. It was calculated from the measured retard.

The first series of tests to verify the sabot functioning were conducted in October 1999. Since the HI-LO adaptor had never been used with the rifled tube, a series of slugs were designed and fired before firing the projectiles to obtain the right mass of propellant charge to obtain the desired velocity. Also the engraving force required was not known and the smooth bore data would be of little to no use.

A schematic of the slug is shown in Fig. 11. The aluminum shell, the polycarbonate ring, the grooves and the aft base were exactly the same as the A1 sabot design. A ballast mass was inserted to approximate the mass of the A1 sabot-model package. There were no petals for this case. This would also confirm that the engraving process and that the torque from the rifling would be transmitted correctly. The mass of the slug was 3.25 kg.

The atmospheric conditions at the time of firing are given in Table 1 and the results for the slug firings are provided in Table 2. The propellant charge mass, the maximum accelerations achieved, the measured in bore and Doppler radar deduced muzzle velocities are provided. The last columns gives some general comments on sabot separation, if the projectile was stable and the impact of the projectile at the targets relative to the aim point. Z is positive downwards and Y is positive to the right when looking downrange.

Three slugs were fired. The first slug remained stuck in the barrel after a displacement of 27.0 mm with a propellant charge of 80.0 g. It was dislodged by firing a very high charge. The driving band diameter was reduced to 107.29 mm from the original 108.71mm. With these modifications, a second slug was fired at the same charge and it successfully exited the gun tube at a velocity of 245.1 m/s. A third slug was fired with

8 TM 2003-077 the same modifications and charge as the previous one to obtain validation. It was also successfully fired with very similar results. The desired muzzle velocity is roughly 30 m/s higher then desired. A typical velocity and acceleration history in the barrel is showninFig.12forSlugSLA1-3.

The next series of tests consisted of firing the A1 model. The measured physical properties of each test projectile are provided in Table 3. The measured center of gravity positions are very close to the designed parameters of 3.12 cal and 2.72 cal from the nose. The mass of the aft and forward center of gravity projectiles were roughly 922.0 g and 904.0 g, respectively. Unfortunately, there was an error in the fin cant angle. Instead of being +4.0° they were at -4.0°. This implies that, even if the sabot achieved full spin rate at the muzzle, the spin rate of the model would decay very rapidly and spin to an equilibrium negative steady spin rate. Six-degree-of-freedom trajectory simulations confirmed this also. This means that all the models with the aft center of gravity positions (Models A1-01 to A1-05) could not be fired, as they would be gyroscopically unstable and unsafe to fire. It was decided that the models with the forward center of gravity positions could be fired, as they were statically stable. The effect of the very rapid change in spin rate was of a concern on the flight dynamics performance, but it was deemed necessary to launch them to at least verify sabot separation, integrity and to confirm that the full spin rate could be transmitted.

The firing conditions are provided in Table 1 and the results in Table 4. The sabot of the first shot (A1-10) was modified so that the driving band was the same as the two slugs that were successfully fired. The shot was fired with 80 g of propellant and the sabot did not open at exit, but the muzzle velocity was good.

It was decided to modify the sabot for the second shot (A1-09) by cutting the slots further in the base till there was 5.33 mm of wall left. The saw cuts were filled with resin. Again the sabot did not open but the muzzle velocity was correct.

The sabot of the third shot (A1-08) was modified by still cutting deeper in the back end till there was 2.3 mm of wall left and by cutting the slots in the polycarbonate up to the driving band. The sabot opened very quickly and more than the sabot trap dimensions (1.22 m x 1.22 m) at 9.2 m from the muzzle. The projectile was unstable at the target and it entered at 90.0°. The muzzle velocity was similar to the other shots. Photographs of the sabot separation for this shot can be seen in Fig. 13.

For the next shot, A1-07, the polycarbonate ring was only split halfway to the driving band and all the other conditions were as the prior shot. The results were very similar to shot A1-08, that is, a quick sabot opening and the projectile unstable, with a slight drop in muzzle velocity. The recovered sabot pieces indicated that there was impact between the sabot and the model at launch.

The last shot, A1-06, was a repeat of A1-08, with a slightly lower charge. The results were the same as the A1-08, but with a muzzle velocity of 213.0 m/s. Again the recovered sabot pieces showed impact of the model on the sabot and these are shown in Fig. 14. The arrows point out where the impact occurred during separation at the muzzle and this was probably the cause for the projectile being unstable. A recovered

TM 2003-077 9 polycarbonate ring (Fig. 15) shows the imprint of the rifling indicating that the torque from rifling was transmitted to the sabot to produce the required spin rate.

4.3.1 Comments and Discussions

The action of the sabot in the gun tube is correct. It transmits the torque to the model and propels it to the muzzle without breakage. The problem exists at separation where there is impact of the sabot petals with the model at the moment when the petals rotate. This rotation speed has to be reduced by reducing the mass of the petals combined with a slight modification at the base of the sabot where there is contact, and possibly by adding a pusher pad. The desired muzzle velocities were obtained. The fins on the models will also have to be oriented in the right direction.

4.4 Sabot-Model Integrity Trials 2 (July 00) for A1 Model

A series of wind tunnel tests were conducted on the A1 projectile [12] and the results showed that the XCP was very close to the predicted values and therefore the same center of gravity positions were kept for this second series of tests. The wind tunnel roll producing moment due to the fin cant was quite different from the predicted one, higher by a factor of 5.0. But since the value of the roll damping moment was not known, it was decided to keep the angle of the fins at 4.0°.

Six projectiles were requested for the second series of tests, three with a forward center of gravity and three with an aft center of gravity. The physical properties of each test projectile are provided in Table. 5. The fins were all canted at +4.0°.

The modifications to the sabot that were made during the first trial were kept and it was additionally modified as follows for the second series of tests as shown in the schematic of Fig. 16 and in the photograph of Fig. 17. The first modification consisted in lightening the sabot petals by drilling out some material in the center of each petal. The second modification was to remove some material at the base of the sabot where the impact was noticed. The option of using an aluminum cylindrical spacer between the model and the sabot was retained. The total mass of the modified model-sabot package was 2.76 kg.

The second series of tests occurred in July 2000 and the firing conditions are provided in Table 6 and the results in Table 7. The first shot was a forward XCG projectile (A1-21), which is a statically stable projectile, with a propellant mass of 70.0 g. The cylindrical pad was not used. The sabot separation was good, the projectile was stable at the muzzle, but there was a slight impact trace on one of the recovered sabot petal. The projectile was unstable at 150.0 m. The muzzle velocity is a bit high.

The second projectile fired, A1-24, an aft XCG projectile that is gyroscopically stabilized, was fired with a reduced charge to lower the launch velocity. The launch was successful and the projectile was stable at the muzzle, and at the yaw card at 30.0

10 TM 2003-077 m, but it was unstable at 150.0 m. The velocity was reduced to roughly 215 m/s. A photograph of the projectile in flight can be seen in Fig. 18 at the first camera position.

A second statically stable projectile, A1-22, was fired. The launch was very good and the projectile was stable up to the target. The muzzle velocity at this charge was repeatable. The in bore data was not determined. The sabot separation can be seen in Fig. 19 at the first camera position.

A second aft XCG projectile was fired, A1-25, and a very bad launch occurred as shown in Fig. 20. There is no doubt that there was a very adverse sabot separation and that there was contact.

This shot was followed by the remaining statically stable projectile, A1-23, and a good launch was achieved and the projectile was stable all the way to the target. A photograph of the model in flight can be seen in Fig. 21 at the second camera position.

The last projectile available was fired (A1-26), and in this case the cylindrical spacer was installed. The sabot opening was a lot less than the other ones and again the projectile was unstable at the muzzle. The recovered sabot pieces again showed traces of impact between the model and sabot.

The drag coefficient was determined from the Doppler radar velocities for two shots that reached the target. It was calculated from the measured retard and they are provided in Table 8. The CD is roughly 0.25 at Mach 0.6.

The roll orientations of the projectiles on the yaw cards were also determined for four of the shots. These are giving in Annex A. The spin rates were deduced where applicable.

4.4.1 Comments and Discussions

An asymmetric sabot separation occurs with the present sabot design fired with a propellant charge of 60.0 g since there is still too much material at the end of the sabot to break. The present 2.3 mm of wall thickness left should be further reduced to 1.52 mm. As proof that the breakage is uneven, a component of two polycarbonate segments were recuperated un-separated. This has the effect that the aluminum petals impact the sabot trap randomly, that is, two petals impact the sabot trap at a different radius from the firing line while the other two miss the sabot trap completely.

The consequence of having two petals non separated on the model while it flies along the firing line with one fin stuck in between them would be tragic on the trajectory.

The engraving of the driving band from the rifling of the tube has to also be done in a symmetric fashion. As there are 28 grooves in the gun tube and that there are four polycarbonate segments on the sabot, special care has to be

TM 2003-077 11 taken to make sure that 4 grooves (multiple of 7) coincide with the four saw cuts of the petals when loading the gun.

The amount of material to break from the polycarbonate ring should also be weakened by increasing the slot to halfway along the driving band and at half thickness to make sure that the breakage be even from one segment to another.

With some roll data and spin rate available, it was possible to obtain the roll- damping coefficient by holding the roll producing moment to the wind tunnel values. This was first done with the statically stable models where the projectile was stable over 150.0 m. Afterwards, 6DOF trajectory simulations were conducted with the aft center of gravity projectile, and it was shown that a fin cant in between 7.0° and 8.0° was necessary to obtain a gyroscopically stable projectile over 150.0 m. These results coincide with the results for projectile A1-24 which was stable at 30.0 m and unstable at the target, showing a loss of gyroscopically stability since the required spin was not maintained at a fin cant of 4.0°.

After discussion with ISL personnel, it was decided to fire more projectiles in another series of tests with minor sabot modifications. Two projectiles with the forward XCG with a fin cant of 4.0° would be fired and two projectiles with the aft XCG with a fin cant of 8.0°.

4.5 Sabot-Model Integrity Trials 3 (Nov. 00) for A1 Model

The sabot design was basically the same as the last series with the slight modifications that were suggested in the last section. The physical properties of the tested projectiles are given in Table 9. The trials took place in November 2000 and the firing conditions are provided in Table 10 and the results in Table 11.

The first shot fired, A1-31, provided very good results. Good sabot separation was achieved and the projectile attained the target with no large yaw. The velocity was a bit higher than the previous trial at the same charge since there is less resistance due to driving band being thinner. A photograph of the projectile in flight at the second camera station is show in Fig. 22. A small amount yaw is discernable. The imprints on the yaw cards also showed very little yaw.

An aft XCG projectile with a fin cant angle of 8.0°, A1-33, was then fired at the same charge. There was a good sabot separation and pictures of the separation are shown in Fig. 23. At the first camera position the yaw angle is very low while it is very high at the second camera position. It did not impact the target at 150.0 m.

A second projectile with a forward XCG , A1-32, was fired at a slightly reduced charge. There was sabot-model impact and high yaw angles at both camera positions,

12 TM 2003-077 as seen in Fig. 24. At the yaw card positions, the angles were low and there was no impact on the target at 150.0 m. The measured roll orientations are given in the annex.

The last available shot, A1-34, was fired with similar results as shot A1-33 (Fig. 25). The sabot separation was good but there appears to have been some model-sabot contact.

The deduced drag coefficients for two shots are given in Table. 12. The drag at Mach 0.7 is a bit higher than at Mach 0.6 partially due to a standard Mach number rise in this region and possible also to higher angles of attack. The second shot definitely had very high angles of attack to produce such a high drag.

4.5.1 Comments and Discussions

The modifications to the sabot have made the separation of the sabot symmetric but it is still missing the dimensions of the sabot trap. To alleviate this, a special set up will be required at the aeroballistic range to make sure that the sabot petals are captured. The separation of the petals was measured by putting a cardboard at 7.3 m from the muzzle. The separation of the petals was very symmetric, for two consecutive shots, and at a radius of 65 cm from the firing line.

The results show that there is still some contact between the sabot and the models and it seems to be happening more with the model with the aft XCG than the forward one. As a matter of fact, all the aft XCG models fired had a very poor flight dynamic behavior. The fact that the aft XCG has a solid base (Fig. 7b) and the forward one has an opening at the base (Fig. 7a) might shed some crucial information. As the sabot opens, the pivot point of the opening will be at the base of the petals close to the model. In the first test, impacts were noticed at the base of the petals over a small region. A small amount of material was removed from the sabot for the second series of tests and there was some success with the forward XCG models and none with the aft one. But some sabot impacts were still noticed on one shot of the forward XCG and all of the aft ones. The last trial again functioned relatively well for the forward XCG and not for the aft XCG . Therefore it is possible, and very probable, that the contact between the sabot and the model still occurs at the pivoting point of the sabot opening when the petals rotate. The last trial showed that, at least, with the latest sabot modifications that the sabot was opening in a symmetric fashion.

TM 2003-077 13 4.6 Final Sabot Design for A1 Model

With the comments of the last section, a final sabot design was brought forward and the schematic is shown in Fig. 26. The major modifications are at the base of the sabot. More material was removed from the sabot in the section just aft of the model. The prime objective of the new sabot design was to displace the pivot point of the opening process further back, on a plastic ball bearing, rather than at the junction of the four petals of the previous designs. This will have the effect of momentary retard the angular rotation and the opening of the sabot with respect to the contact point at the base of the model with the sabot. This will permit a prolonged time for the axial separation of model. This should also help in enforcing a symmetric separation of the sabot petals. All the other modifications to the driving band were kept. This will be the sabot that will be used for the aeroballistic range tests.

After discussion with ISL, it was agreed that the first three models to be fired in the aeroballistic range program would be the configuration with the forward XCG with a fin cant of 4.0°. For security reasons the movable butt in the aeroballistic range will be located at 130.0 m form the muzzle to stop the projectiles. If these launches are a success, two projectiles with the aft XCG location with a fin cant of 8.0° would then be fired. The propellant charge mass is 55.0 g to obtain a velocity of 210.0 m/s.

14 TM 2003-077 5. Model, Sabot Design and Tests for A3 Model

5.1 Model Design for A3 Configuration

The main concern in the model design for the A3 grid finned configuration (Fig. 2) was the possibility of structural failure of the fins at the base. The expected launch accelerations were of the order of 30 000 gn at Mach 4.0. Since the body of the A3 configuration is the Air Force Finner [3] and that some aeroballistic range tests had been conducted also at DREV on that configuration [13], it was decided to keep the same center of gravity position for the grid finned model. This would allow an easier comparison of the aerodynamic results, especially for the dynamic derivatives. The center of gravity position for the Air Force Finner projectile was 4.8 cal from the nose of the projectile [3, 13].

Therefore the body was made of an aluminum alloy with a brass nose. A photograph of the model is shown in Fig. 27. The aft end of the projectile demonstrating the grid fin attachments to the model body is shown in Fig. 27b. The fins were made of high proof steel and they were glued in slots in the aluminum body. The placement of the roll pin to measure the roll orientation in the aeroballistic range tests is easily seen. The physical properties of the A3 projectiles for the first series of tests are given in Table 13. The center of gravity is located at about 4.84 cal from the nose and the mass of the projectile is roughly 665 g.

5.2 Sabot Design for A3 Model Since this model configuration in this case is fin stabilized, a smooth bore gun was utilized. The standard gun employed at DRDC-V to fire fin-stabilized projectiles of these dimensions in the aeroballistic range is a 110-mm smooth bore gun. A schematic of the sabot design for the A3 projectile is show in Fig. 28. It is a two- petal sabot design made of aluminium. It had four projectile centering screws at the front of the sabot. The lengths of the saw cuts on each side were adjusted to obtain adequate petal separation for the expected velocities. A sabot base seal pad was also used to prevent gas leakage past the sabot body.

A pivot pin, which is in line with the saw cuts, was added to force the sabot opening at that point. A polycarbonate ring with a 5° angle is positioned at the aft end of the sabot. There are two reasons for this. The first one, is to have a good pressure seal between the sabot and the gun tube so as to be able to have a known shot start pressure which helps in having consistent muzzle velocities at the same propellant charge mass. The second reason is that, as the sabot leaves the gun tube, the high radial pressure acting on the rear ring relative to the front part, causes the pivoting action at the pivot point of the sabot petals. The mass of the combined sabot-projectile was approximately 2.7 kg.

TM 2003-077 15 A photograph of the sabot-model package is shown in Fig. 29

5.3 Sabot-Model Integrity Trials 1 (Oct. 99) for A3 Model

The first series of tests to verify the sabot functioning for the A3 model were conducted in October 1999. Since model-sabot combinations of this mass were fired previously, a charge determination was not necessary since enough data was available. The velocity of interest for the A3 projectile was from 210 m/s (Mach 0.6) to 1200 m/s (Mach 3.5).

Just prior to the free-flight trials for the A3 projectile, some wind tunnel results [14 and 15] became available. Those results showed that this projectile, with the present center of gravity position, was statically unstable for all Mach numbers below 2.5. The test plan was modified so as to test the sabot-projectile configuration at Mach 2.5 and above.

The firing conditions at the time of firing are provided in Table 14 and the results in Table 15. The propellant type that was used was NQM-044. The first shot, A3-01, was fired as close as possible to Mach 2.5. The sabot separation was correct and the petals impacted the sabot trap. The projectile was unstable for the reasons explained previously.

The second shot, A3-04, was fired at a reduced charge to obtain a velocity of about 675.0 m/s. This was done to make sure the wind tunnel results were correct and the free-flight trials confirmed that the projectile was unstable. The sabot separation was correct.

The third shot fired, A3-03, was fired at the same charge as the first tests. The velocity obtained as slightly higher than the first shot, and the projectile was stable and it impacted the target at 150.0 m. This also confirms the wind tunnel results that static stability occurs just above Mach 2.5. A photograph of the projectile in flight is provided in Fig. 30 at the second camera position.

The last shot fired for this configuration, A3-05, was at a velocity of about 1173 m/s (Mach 3.5). The maximum accelerations measured were roughly 25 000 gn and the fins survived the launch loads. The projectile was stable and it impacted the target. The sabot separation is show in Fig. 31 at the first camera position.

The reduced drag coefficients from the Doppler measured velocity are provided in Table 16 and, as expected, they are high compared to planar fin.

16 TM 2003-077 5.3.1 Comments an Discussions

The separation and functioning of the sabot at 860.0 m/s and 1175 m/s performed as designed. The main concern is, unexpectedly, that the projectile is unstable below Mach 2.5 at the present center of gravity position. The wind tunnel results [14 and 15] show that it would be impractical to try to fire the A3 projectile subsonically. To increase the Mach number range, the only option was to displace the center of gravity location forward on the projectile.

Based on the wind tunnel results and a stability analysis, it was shown that, replacing the brass nose by a tungsten one would displace the center of gravity position forward by about one caliber. This would allow having a stable projectile from about Mach 1.4 and higher.

It was therefore decided to have a second series of tests with the tungsten nose projectile to verify that the stresses at the base of the model would not be surpassed at the higher velocities.

5.4 Sabot-Model Integrity Trials 2 (July 00) for A3 Model

There were no sabot design changes for the second series of tests. The nose section of the model was replaced with a tungsten one. A photograph of the sabot-model package is shown in Fig. 32. The total mass was roughly 2.9 kg.

The physical properties of the projectiles with the tungsten nose are furnished in Table 17. The center of gravity location is at 4.03 cal of the nose, about 0.8 cal more than the brass nose projectile. The mass of the projectile increased by about 200 g, to 880.0 g

Three projectiles were fired in the second series of tests conducted in July of 2000. The firing conditions are provided in Table 18 and the results are presented in Table 19. The chamber pressures were measured in these trials. The first shot fired at about Mach 3.5, A3-21, was completely successful. The sabot separation is shown in Fig. 33.

The second shot, A3-22, fired at a velocity of 675.1 m/s, or Mach 2.0, was also successful in all the aspects.

The third shot, A3-23, was not successful since the sabot did not open enough. The amount of material along the saw cuts at the base of the sabot will have to be reduced till there is about 0.13 mm to 0.38 mm of material left.

The deduced drag coefficients for the two successful shots are supplied in Table 20. The CD are basically the same as the first series of tests

TM 2003-077 17 5.4.1 Comments and Discussions

Overall, the sabot functioning is very satisfactory from Mach 1.5 to 3.5 with the tungsten model. The model is stable at Mach 1.5 and above, and the fins survive the launch loads.

It is planned to fire about 10 projectiles in the aeroballistic from Mach 1.5 to 3.5 to obtain the aerodynamic coefficients and stability derivatives of this grid fin configuration

18 TM 2003-077 6. Model, Sabot Design and Tests for A2 Model

The Mach number of interest of the A2 projectile configuration (Fig. 3) was about 0.6. Since the A3 model was unstable subsonically it was highly likely that the A2 projectile configuration would also be unstable. Wind tunnel tests confirmed this hypothesis. Therefore, it was not possible to fire this projectile at that Mach number and at the center of gravity position of the fabricated projectiles. For completeness purposes, the sabot design will be presented as well as the test results for two slugs of the same mass.

The models were made of steel and the measured physical properties are supplied in Table 21. The center of gravity position is located at 3.4 cal from the nose and the mass is about 730.0 g. A photograph of the A2 projectile is shown in Fig. 34. The fins were made of high proof steel and they were glued in slots in the steel body.

A schematic of the sabot design is illustrated in Fig. 35 and a photograph of the sabot package is shown in Fig. 36. The sabot pieces and functioning are the same as the A3 projectile. The total mass of the sabot and model was around 2.18 kg.

The gun tube to be utilized was the 110 mm smooth bore gun with the HI-LO adaptor. There were no data for the HI-LO adaptor at this sabot-projectile mass. Therefore, two slugs were fabricated at mass of 2.21 kg. The results of this test are provided in Table 22. The muzzle velocities obtained for propellant charge masses of 40.0 g and 80.0 g were 170.7 m/s and 263.9 m/s, respectively.

The wind tunnel results showed that the center of pressure was located at 0.8 cal from the nose at Mach 0.6. It was deemed impossible, based on those results, to displace the center of gravity position ahead of this location and to have a statically stable projectile and a structurally sound one. Therefore, the aeroballistic range trials for the A2 projectile were not pursed any further.

TM 2003-077 19 7. Conclusions

The model and sabot design of the A1, A2 and A3 projectile configurations for the joint DRDC-ISL project were presented.

The initial free-flight trials to test the sabot concepts to launch the three configurations were successfully completed. The velocity of interest, depending on the configuration, ranged from 210 to 1200 m/s. A 110-mm smooth bore and 105 mm rifled gun tubes with and without a special Hi-Lo adapter were used to launch the projectiles. A series of slugs were fired to obtain the required propulsive charge to obtain a specific velocity in some cases. The propellant charge mass, muzzle velocity, maximum acceleration were determined for each shot and the drag coefficient was deduced from the stable projectiles.

Three trials were necessary to obtain a safe sabot to launch the A1 projectile configuration. A total of eighteen shots were fired. The design of the sabot and the projectile proved to be quite a challenge. The engraving process, the symmetric petal separation, as well as avoiding model sabot contact at separation at a velocity of 210 m/s and at high spin rates simultaneously, were finally resolved.

The sabot concept for the A3 projectile worked as expected. The projectile was modified to have its center of gravity position more forward than the first design. This was done since the latticed finned projectile was statically unstable. The new projectile design will allow testing from Mach 1.4 to 3.5.

The A2 projectile was never fired since the projectile was unstable at the Mach number range of interest of 0.6. It was believed impossible to displace the center of gravity position to obtain a statically stable projectile and a structurally sound one. Therefore, the aeroballistic range trials for the A2 projectile will not be pursed.

The next step in the project is to fire the two different configurations in the DRDC Valcartier aeroballistic range to determine their aerodynamic characteristics and stability derivatives (static and dynamic) with the goal of establishing a reliable database.

20 TM 2003-077 8. References

1. Fleck, V., Berner, C., "Increase of Range for an Artillery Projectile by Using the Lift Force", Proceedings 16th International Ballistics Symposium, San Francisco, CA, USA, 23-27 September 1996, ISL Report PU 355/96

2. Abate, G., Winchenbach, G. and Hathaway, W., “Transonic Aerodynamic and Scaling Issues for Lattice Projectiles Tested in Ballistic Ranges”, 19th International Symposium on Ballistics, 7-11 May, 2001, Interlaken, Switzerland.

3. West, K. O., "Comparison of Free-flight Spark Range and Wind Tunnel Test Data for a Generic Missile Configuration at Mach Numbers From 0.6 to 2.5", AFATL-TR-81-87

4. Washington, W.D., Miller, M.S., "Experimental Investigations on Grid Fin Aerodynamics: A Synopsis of Nine Wind Tunnel and Three Flight Tests", RTO- MP-5 AC/323(AVT)TP/3, November 1998

5. Simpson, G.M., Saddler, A.J., "Lattice Controls: A Comparison with Conventional Planar Fins", RTO-MP-5 AC/323(AVT)TP/3, November 1998

6. Abate, G.L., Duckerschein, R.P., Hathaway, W., "Subsonic/Transonic Free- Flight Tests of a generic Missile with Grid Fins", AIAA Paper 2000-0937, 38th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, USA, Jan. 2000

7. Fournier, E., “Aerodynamic Coefficients Measurements of a High L/D Projectile with Grid Fins”, DREV TM 2001-035, April 2001, UNCLASSIFIED

8 DeSpirito, J., Edge, H., Weinacht, P., Sahu, J. and Dinavahi, S., “Computational Fluid Dynamics (CFD) Analysis of a Generic Missile with Grid Fins”, ARL-TR- 2318, September 2000

9. "Projectile Design Analysis System (PRODAS), P2000 V 2.2.17", Arrow Tech Associates Inc., 2000.

10. Moore, F. G., McInville, R., M. and Hymer, T., "The 1995 Version of the NSWC Aeroprediction Code: Part I - Summary of New Theoretical Methodology", Naval Surface Weapons Center, NSWCCDD/TR-94/379, February 1995

11. Burns,K.A.,Deters,K.J.,Stoy,S.L.,Vukelich,S.R.andBlake,W.B, "Missile Datcom Users Manual - Revision 6/93", WL-TR-93-3043, June 1993

12. Dupuis, A.D. and Berner, C., “Wind Tunnel Tests of a Long Range Artillery Shell concept”, AIAA-2002-4416, August 2002.

TM 2003-077 21 13. Dupuis, A. D. and Hathaway, W., “Aeroballistic Range Tests of the Air Force Finner Reference Projectile”, DRDC Valcartier TM 2002-008, May 2002, UNCLASSIFIED

14. Berner, C., and Dupuis, A., “Wind Tunnel Tests of a Grid Finned Projectile Configuration”, AIAA 2001-0105, 39th Aerospace Sciences Meeting and Exhibit, 8-11 January 2001, Reno, Nevada (ISL PU346/2000)

15 Dupuis, A. and Berner, C., “Aerodynamic Aspects of a Grid finned Projectile at Subsonic and Supersonic Velocities”, 19th International Symposium on Ballistics, Interlaken, Switzerland, 7-11 May 2001

22 TM 2003-077 0.50

R 10.12 1.00

0.088 δ 1.00

3.00

1.90

5.65

Figure 1a. General geometry

R 0.002 0.50

0.053

R 1.264

Figure 1b. Fin details

Figure 1. Model A1 - Artillery shell concept with wings (all dimensions in caliber, 1 cal = 30 mm)

TM 2003-077 23 R6.53

R 0.007 0.44 1.00

0.7 2.50 0.7

10.00

Figure 2a. Overall geometry

0.44 0.08

0.124

0.017 0.161 0.55 0.70

0.017

0.075

0.13

Figure 2b. Fin details Figure 2. Model A3 - Grid finned projectile (all dimensions in caliber, 1 cal = 30 mm)

24 TM 2003-077 R 10.12

0.088 1.00 0.44

3.00 0.70

3.43 0.70

5.65

Figure 3a. Overall geometry

0.44 0.08

0.124

0.017 0.161 0.55 0.70

0.017

0.075

0.13

Figure 3b. Fin details Figure 3. Model A2 - Artillery shell concept with grid fins (all dimensions in caliber, 1 cal = 30 mm)

TM 2003-077 25 26

12.0 m

35 GHz 1.2 m 7.2 m RADAR 1m

Reflecting Sabot ED - 850 110 mm gun Blast mirror trap Radar guage

Yaw card packs at 20.0 m and 30.0 m

Ballistic Synchro 6.3 m Camera 9.2 m 11.5 m 150.0 m M2003-077 TM

Figure 4. Schematic of the test site

TM 2003-XX 26 Figure 5a. View 1

Figure 5a. View 2 Figure 5. Photograph of test set up

TM 2003-XX 27 28

1 - M-63 primer 5 - Diffuser 2 - Obturator 6 - “O” ring 3-“O”ring 7-Nut 4-Shaft Figure 6. Hi-Lo 110 mm chambre adapter M2003-077 TM

TM 2003-XX 28 Figure 7a. Statically stable projectile; XCG = 2.72 cal from nose

Figure 7b. Gyroscopically stable projectile; XCG = 3.12 cal from nose

Figure 7. Schematics of A1 projectile design

TM 2003-XX 29 1 - Base seal 3 - Aluminium sabot body 2 - Polycarbonate ring 4 - A1 Projectile Figure 8. Sabot schematic for the A1 projectile

Figure 9. Photograph of sabot package for A1 model

30 TM 2003-077 Figure 10a. Grooved portion of sabot body

Figure 10b. Polycarbonate section Figure 10. Photographs of A1 sabot pieces

TM 2003-077 31 1 - Polycarbonate sabot 3 - Ballast 2 - Retaining pin 4 - Seal Figure 11. Sabot schematic for the slug for A1 model

250.0 35000.0

30000.0

200.0 25000.0

20000.0 150.0

15000.0

100.0 10000.0

5000.0 50.0

0.0

0.0 -5000.0 -0.035 -0.030 -0.025 -0.020 -0.015 -0.010 -0.005 0.000 0.005 Time (s)

Figure 12. Velocity and acceleration history for Slug SLA1-3

32 TM 2003-077 Figure 13a. Camera 1

Figure 13b. Camera 2

Figure 13. Sabot separation for A1 model - Shot A1-08, VMUZ =240.0m/s

TM 2003-077 33 Figure 14a. View 1

Model sabot contact

Figure 14b. View 2 Figure 14. Photographs of recovered sabot pieces for A1 model

34 TM 2003-077 Figure 15. Photograph of recovered polycarbonate section

TM 2003-077 35 1 - Base seal 3 - Aluminium sabot body 2 - Polycarbonate ring 4 - A1 Projectile 5 - Optional cylindrical pad Figure 16. Modified sabot schematic for the A1 projectile - July 00

Figure 17. Photograph of modified sabot package for A1 model - July 00

36 TM 2003-077 Figure 18. Sabot separation for A1 model - Shot A1-24, VMUZ =218.1m/s

Figure 19. Sabot separation for A1 model - Shot A1-22, VMUZ =215.7m/s

TM 2003-077 37 Figure 20. Sabot separation for A1 model - Shot A1-25, VMUZ =215.0m/s

Figure 21. Sabot separation for A1 model - Shot A1-23, VMUZ =212.7m/s

38 TM 2003-077 Figure 22. Sabot separation for A1 model - Shot A1-31, VMUZ = 233. m/s

Figure 23a. Camera 1

Figure 23b. Camera 2

Figure 23. Sabot separation for A1 model - Shot A1-33, VMUZ =233.6m/s

TM 2003-077 39 Figure 24a. Camera 1

Figure 24b. Camera 2

Figure 24. Sabot separation for A1 model - Shot A1-32, VMUZ =213.8m/s

40 TM 2003-077 Figure 25a. Camera 1

Figure 25b. Camera 2

Figure 25. Sabot separation for A1 model - Shot A1-34, VMUZ =208.9m/s

TM 2003-077 41 1 - Base seal 3 - Aluminium sabot body 2 - Polycarbonate ring 4 - A1 Projectile 5-Pivotballbearing

Figure 26. Schematic of final design for the A1 projectile

42 TM 2003-077 Figure 27a. Plan view

Figure 27b. Rear view Figure 27. Photograph of A3 projectile with brass nose

TM 2003-077 43 1 - 5.0° polycarbonate ring 4 - Aluminium petal 2 - Centering screws 5 - Seal pad 3 - A3 projectile 6 - Pivot pin Figure 28. Sabot schematic for the A3 projectile

Figure 29. Photograph of sabot package for A3 model

44 TM 2003-077 Figure 30. Sabot separation for A3 model - Shot A3-03, VMUZ =859.4m/s

Figure 31. Sabot separation for A3 model - Shot A3-05, VMUZ = 1173.1 m/s

TM 2003-077 45 Figure 32. Photograph of sabot package for A3 model - July 00

46 TM 2003-077 Figure 33a. Camera 1

Figure 33b. Camera 2

Figure 33. Sabot separation for A3 model - Shot A3-21, VMUZ = 1158.4 m/s

TM 2003-077 47 Figure 34. Photograph of A2 projectile

48 TM 2003-077 1 - 5.0° polycarbonate ring 4 - Aluminium petal 2 - Centering screws 5 - Seal pad 3 - A2 projectile 6 - Pivot pin Figure 35. Sabot schematic for the A2 projectile

Figure 36. Photograph of sabot package for A2 model

TM 2003-077 49 Table 1. Firing Conditions for A1 model - Trial 1 (Oct 99)

Model Date Atmospheric Atmospheric Number Fired Temperature Pressure (°C) (mBar)

A1-10 25/10/99 0.6 996.0 A1-09 25/10/99 1.6 996.2 A1-08 26/10/99 1.3 991.8 A1-07 26/10/99 3.8 989.6 A1-06 27/10/99 2.2 1004.8

Table 2. Results from gun firing for 3.25 slugs (Oct 99) 105 mm HI-LO – 9.525 DIFFUSER PROPELLANT TYPE: N-311 – 0.035 MTOT = 3.25 kg Doppler Model Propellant Max In bore Radar Comments Number Mass Acc. Muzzle Muzzle Velocity Velocity (g) (gn) (m/s) (m/s)

Slug stuck in barrel after 27 mm displacement SLA1-1 80.0 - - - Slug pushed out with high propellant charge

Driving band diameter reduced to 107.29 mm from 108.71 mm SLA1-2 80.0 3245 240.5 245.1 Good results Impact at 150 m Z = -2.5 m Y = -0.2 m

Repeat of SLA1-2 Good results SLA1-3 80.0 3361 240.5 241.5 Impact at 150 m Z = -1.5 m Y=+1.0m

50 TM 2003-077 Table 3. Measured physical properties of A1 projectiles (Oct. 99)

CG CG CG Model d l from from from m IX IY Number nose nose nose (mm) (mm) (mm) (cal) (cg/l) (g) (g-cm2) (g-cm2)

A1-01 30.00 169.520 93.983 3.133 0.554 921.9 1131.33 15881.01 A1-02 30.00 169.545 93.899 3.130 0.554 922.0 1131.04 15892.80 A1-03 30.00 169.672 93.980 3.133 0.554 923.1 1130.44 15945.12 A1-04 29.99 169.622 94.008 3.134 0.554 922.6 1129.36 15947.20 A1-05 30.00 169.647 94.155 3.139 0.555 921.2 1130.58 15874.12

A1-06 29.99 169.571 81.788 2.727 0.482 903.5 1088.96 13312.95 A1-07 29.99 169.545 81.742 2.726 0.482 905.3 1093.09 13341.18 A1-08 29.99 169.571 81.715 2.725 0.482 905.6 1093.72 13348.39 A1-09 30.00 169.622 81.826 2.728 0.482 903.1 1089.28 13324.29 A1-10 29.99 169.571 81.648 2.722 0.482 904.7 1090.70 13342.53

TM 2003-077 51 Table 4. Results from gun firing for A1 Model - Trial 1 (Oct 99) 105 mm HI-LO – 9.525 DIFFUSER PROPELLANT TYPE: N-311 – 0.035 MTOT = 3.15 kg Doppler Model Propellant Max In bore Radar Comments Number Mass Acc. Muzzle Muzzle Velocity Velocity (g) (gn) (m/s) (m/s)

Driving band diameter at 107.29 mm A1-10 80.0 3354 247.0 250.0 Sabot did not open - To much plastic to break

- Sabot modified by saw cutting deeper A1-09 80.0 2553 247.5 251.3 5.33 mm wall left - Slots filled with resin - Sabot did not open

- Saw cuts made deeper leaves 2.3 mm wall - Slot split to driving band - Sabot opened very fast A1-08 80.0 2496 240.0 see note1 more than sabot trap size - Projectile unstable -Impactat150m Z = +1.8 m Y = -0.5 m (90° orientation impact)

- Slots split halfway to driving band A1-07 80.0 2448 229.1 see note 1 - Results similar to A1-08 - Evidence of impact of sabot and model

- Repeat of A1-08 A1-06 70.0 1813 213.0 see note 1 -Sameresults - Evidence of impact of sabot and model 1 since projectile was unstable, unable to obtain accurate muzzle velocity

52 TM 2003-077 Table 5. Measured physical properties of A1 projectiles (July 00)

CG CG CG Model d l from from from m IX IY Number nose nose nose (mm) (mm) (mm) (cal) (cg/l) (g) (g-cm2) (g-cm2)

A1-21 30.00 169.583 81.410 2.714 0.480 900.3 1089.73 13147.72 A1-22 29.97 169.622 81.593 2.722 0.481 902.1 1091.06 13273.21 A1-23 29.99 169.672 81.689 2.724 0.481 906.4 1096.38 13385.87

A1-24 29.97 169.634 93.835 3.131 0.553 922.6 1130.67 15914.94 A1-25 29.98 169.660 93.846 3.130 0.553 922.5 1130.94 15934.61 A1-26 29.98 169.533 93.820 3.129 0.553 921.1 1130.40 15862.55

Table 6. Firing Conditions for A1 model - Trial 2 (July 00)

Model Date Atmospheric Atmospheric Number Fired Temperature Pressure (°C) (mBar) A1-21 10/07/00 19.5 983.4 A1-24 10/07/00 23.3 983.1 A1-22 11/07/00 16.6 989.5 A1-25 11/07/00 16.7 989.9 A1-23 11/07/00 18.3 990.1 A1-26 11/07/00 18.8 990.3

TM 2003-077 53 Table 7. Results from gun firing for A1 Model - Trial 2 (July 00) 105 mm HI-LO – 9.525 DIFFUSER PROPELLANT TYPE: N-311 – 0.035 MTOT = 2.76 kg Doppler Model Propellant Max In bore Radar Comments Number Mass Acc. Muzzle Muzzle Velocity Velocity (g) (gn) (m/s) (m/s) Good sabot separation Stable at muzzle Unstable at 150 m Impact traces on sabot petal A1-21 70.0 2440 250.0 245.7 due to model Impact at 150 m Z = +1.9 m Y = -1.7 m Good sabot separation Projectile stable A1-22 60.0 - - 215.7 Impact at 150 m Z = 1.6 m Y = -0.1 m Good sabot separation Projectile stable A1-23 60.0 2055 210.0 212.7 Impact at 150 m Z = 2.1 m Y = -0.05 m Good sabot separation Stable at 30 m Unstable at 150 m A1-24 60.0 1960 220.0 218.1 Impact at 150 m Z = +2.2 m Y = -2.0 m Bad launch A1-25 60.0 2215 215.0 205.2 Projectile unstable at muzzle No impact at 150 m Install base bad in sabot Sabot opened a lot less than other shots A1-26 60.0 1945 205.0 204.5 Projectile unstable at muzzle No impact at 150 m Traces of impact between model and sabot

54 TM 2003-077 Table 8. Deduced drag coefficient for A1 Model - Trial 2 (July 00)

Model Mach CD Number Number

A1-22 0.63 0.248 A1-23 0.62 0.254

Table 9. Measured physical properties of A1 projectiles (Nov. 00)

CG CG CG Model d l from from from m IX IY Number nose nose nose (mm) (mm) (mm) (cal) (cg/l) (g) (g-cm2) (g-cm2)

A1-31 29.98 169.520 81.471 2.718 0.481 904.2 1086.47 13223.75 A1-32 29.98 169.558 81.556 2.721 0.481 904.1 1087.00 13254.61

A1-33 29.97 169.571 93.574 3.122 0.552 928.6 1132.70 16130.19 A1-34 29.97 169.583 93.626 3.124 0.552 928.8 1132.77 16137.92

Table 10. Firing Conditions for A1 model - Trial 3 (Nov 00)

Model Date Atmospheric Atmospheric Number Fired Temperature Pressure (°C) (mBar) A1-31 14/11/00 6.1 983.3 A1-33 14/11/00 5.8 982.8 A1-32 15/11/00 3.1 973.7 A1-34 15/11/00 3.8 973.0

TM 2003-077 55 Table 11. Results from gun firing for A1 Model - Trial 3 (Nov 00) 105 mm HI-LO – 9.525 DIFFUSER PROPELLANT TYPE: N-311 – 0.035 MTOT = 2.74 kg Doppler Model Propellant Max In bore Radar Comments Number Mass Acc. Muzzle Muzzle Velocity Velocity (g) (gn) (m/s) (m/s)

Sabot opening more than sabot dimensions Good sabot separation A1-31 60.0 2240 232.3 233.9 Projectile stable (δ=4.0°) Impact at 150 m Z = +2.2 m Y = -0.6 m

Contact sabot - model A1-32 Hi yaw on Camera 1 and 2 55.0 2300 210.0 213.8 (δ=4.0°) Projectile stable at yaw cards No impact at 150 m

Good sabot separation A1-33 Projectile No yaw at Cam 1 60.0 2220 223.6 (δ=8.0°) unstable High yaw on Cam 2 No impact at 150 m

A1-34 Projectile 55.0 2135 208.9 Good sabot separation (δ=8.0°) unstable No impact at 150 m

Table 12. Deduced drag coefficient for A1 Model - Trial 3 (Nov 00)

Model Mach CD Number Number

A1-31 0.70 0.347 A1-32 0.64 1.606

56 TM 2003-077 Table 13. Measured physical properties of A3 projectiles (Oct. 99)

CG CG CG Model d l from from from m IX IY Number nose nose nose (mm) (mm) (mm) (cal) (cg/l) (g) (g-cm2) (g-cm2)

A3-01 30.00 299.848 145.044 4.835 0.484 663.7 742.93 48403.08 A3-03 29.99 300.000 145.011 4.835 0.483 664.0 742.30 48464.71 A3-04 30.00 299.975 145.034 4.835 0.483 664.2 744.64 48448.90 A3-05 30.00 299.975 145.034 4.835 0.483 663.9 743.18 48489.65

Table 14. Firing Conditions for A3 model - Trial 1 (Oct 99)

Model Date Atmospheric Atmospheric Number Fired Temperature Pressure (°C) (mBar) A3-01 13/10/99 5.7 995.6 A3-04 13/10/99 6.9 990.9 A3-03 14/10/99 4.2 985.4 A3-05 14/10/99 4.4 987.0

TM 2003-077 57 Table 15. Results from gun firing for A3 Model - Trial 1 (Oct 99) 110 mm PROPELLANT TYPE: NQM-044 MTOT = 2.7 kg Doppler Model Propellant Max In bore Radar Comments Number Mass Acc. Muzzle Muzzle Velocity Velocity (kg) (gn) (m/s) (m/s)

Good sabot separation A3-01 2.72 11450 832.8 833.8 Projectile unstable Missed target at 150 m

Good sabot separation A3-04 1.81 7318 674.0 674.5 Projectile unstable Missed target at 150 m

Good sabot separation Impact at 150 m A3-03 2.72 12134 859.2 859.4 Z = +0.1 m Y = -0.1 m

Good sabot separation Impact at 150 m A3-05 4.08 24593 1174.5 1173.1 Z = -0.1 m Y = -1.0 m

Table 16. Deduced drag coefficient for A3 Model - Trial 1 (Oct 99)

Model Mach CD Number Number A3-03 2.57 0.945 A3-05 3.51 1.080

58 TM 2003-077 Table 17. Measured physical properties of A3 projectiles (July 00)

CG CG CG Model d l from from from m IX IY Number nose nose nose (mm) (mm) (mm) (cal) (cg/l) (g) (g-cm2) (g-cm2)

A3-21 29.98 299.911 120.874 4.031 0.403 879.9 953.26 64349.39 A3-22 29.96 299.873 120.765 4.031 0.403 878.3 950.19 64270.32 A3-23 29.96 300.013 120.973 4.037 0.403 877.2 949.81 64292.91

Table 18. Firing Conditions for A3 model - Trial 2 (July 00)

Model Date Atmospheric Atmospheric Number Fired Temperature Pressure (°C) (mBar) A3-21 5/07/00 18.0 989.8 A3-22 5/07/00 17.3 990.0 A3-23 6/07/00 19.7 993.3

TM 2003-077 59 Table 19. Results from gun firing for A3 Model - Trial 2 (July 00) 110 mm PROPELLANT TYPE: NQM-044 MTOT = 2.9 kg Doppler Model Propellant Chamber Max In bore Radar Comments Number Mass Pressure Acc. Muzzle Muzzle Velocity Velocity (kg) (MPa) (gn) (m/s) (m/s)

Good sabot separation Projectile stable A3-21 4.08 104.5 23385 1158.0 1158.4 Impact at 150 m Z = -0.3 m Y = 0.0 m

Good sabot separation Projectile stable A3-22 1.81 23.4 - - 675.1 Impact at 150 m Z = -0.2 m Y = -0.2 m

Bad sabot separation A3-23 1.36 - 4880 555.0 556.4 Split sabot more along sawcuts

Table 20. Deduced drag coefficient for A3 Model - Trial 2 (July 00)

Model Mach CD Number Number

A3-21 3.39 0.902 A3-22 1.98 1.179

60 TM 2003-077 Table 21. Measured physical properties of A2 projectiles (Oct 99)

Model d l CG CG CG m IX IY Number from from from (mm) (mm) nose nose nose (g) (g- (g-cm2) (mm) (cal) (cg/l) cm2)

A2-01 29.98 169.495 103.030 3.437 0.608 727.4 777.43 12225.85 A2-02 29.98 169.444 102.967 3.434 0.608 727.2 776.77 12201.67

Table 22. Results from gun firing for 2.2 kg slugs (Oct 99) 110 mm HI-LO – 9.525 DIFFUSER PROPELLANT TYPE: N-311 – 0.035 MTOT = 2.21 kg Doppler Model Propellant Max In bore Radar Comments Number Mass Acc. Muzzle Muzzle Velocity Velocity (g) (gn) (m/s) (m/s)

SLA2-1 40.0 1250 171.3 170.7 Good shot

SLA2-2 80.0 - - 263.9 Good shot

TM 2003-077 61 Annex A - Measured Roll Orientations

62 TM 2003-077 MODEL A1-21 (cg forward)

φ′ Vmuz = 245.7 m/s; muz = 190.4 °/m