A Study of Projectile Response to Ballistics Environment 

by Stephen E. Ray, Michael J. Nusca, and James F. Newill 

ARL-TR-3672 November 2005 

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Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5066 

ARL-TR-3672 November 2005 

A Study of Projectile Response to Ballistics Environment 

Stephen E. Ray 

U.S. Army High Performance Computing Research Center 

Michael J. Nusca and James F. Newill 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution is unlimited. 
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A Study of Projectile Response to Ballistics Environment 

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Stephen E. Ray,* Michael J. Nusca, and James F. Newill 

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U.S. Army High Performance Computing Research Center, Minneapolis, MN 

14. ABSTRACT 

The U.S. Army Research Laboratory’s interior ballistics code, ARL-NGEN3, is a state-of-the-art modeling tool providing interior

ballistics predictions and flowfield simulations of the ignition, flamespreading, and combustion of solid-propellant charges used to 

launch projectiles from guns. Modern solid mechanics codes such as DYNA3D and EPIC can complement the ARL-NGEN3 code by 

providing a capability to predict the mechanical response of the projectile to the unsteady, high-pressure environment within the gun 

chamber. This report presents results from an ongoing effort to couple the ARL-NGEN3 code to these solid mechanics codes. The

test problem involves a notional gun ammunition concept in which the projectile afterbody “telescopes” or intrudes significantly into 

the gun chamber that houses the solid propellant charge. Results from the ARL-NGEN3 simulation are shown, and they indicate that 

large pressure waves move radially and, more significantly, axially through the combustion chamber during propellant ignition. 

Results from EPIC and DYNA simulations, which utilize the ARL-NGEN3 pressure data and predict material response, are 

compared; good agreement between the codes is demonstrated. Results are also presented from studies using the EPIC code for 

several different internal projectile configurations. 

15. SUBJECT TERMS

gun charges, solid propellant, multiphase flow, material stress 

16. SECURITY CLASSIFICATION OF: 

19a. NAME OF RESPONSIBLE PERSON

Michael J. Nusca 

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iii

Contents 

List of Figures iv

1. Introduction 1

2. Description of Test Case 2

3. ARL-NGEN3 Results 3

4. EPIC/DYNA3D Comparison 4

5. Further EPIC Results – 1.25-in Wall Projectile 6

6. Initial Rotation of Projectile 7

7. Propellant With Minimal Interface Drag 8

8. The 0.5-in Wall Projectile 8

9. Projectile With Payload 9

10. Summary and Conclusions 11

11. References 12

Distribution List 14
iv

List of Figures 

Figure 1. Axisymmetric representation of notional CTA configuration – chamber, projectile 

afterbody, and four propellant regions shown. Note that region IV fills the annular 

volume (4)..................................................................................................................................2 

Figure 2. Geometry of the notional CTA projectile and the surface of the mesh used in the 

EPIC simulation (left) and the DYNA3D simulation (right).....................................................3 

Figure 3. Pressure-time curves predicted using the ARL-NGEN3 code for geometry shown 

in figure 1 – results for the locations labeled “R,” “M,” and “F” along the chamber wall: 

granular propellant (left) and concentric wrap propellant in region IV having minimal 

axial interphase drag (right). Note that the scales in the right-hand picture are lower than 

those on the left (4, 9). ...............................................................................................................3 

Figure 4. Total stress computed by EPIC (solid line) and DYNA3D (dashed line) near the 

back of the projectile forebody (left) and near the midpoint of the projectile tail (right)..........5 

Figure 5. Total stress at 2.4 ms into the gun firing computed by DYNA3D (left) and EPIC 

(right), near the time of the highest total stress. The red region is where the total stress 

surpassed 90 ksi (621 MPa); the material likely would have failed and the projectile 

damaged in that region...............................................................................................................5 

Figure 6. Total stress computed by EPIC using the full data set (red line) and the sparse data 

set (blue line) near the back of the projectile forebody (left) and near the midpoint of the 

projectile tail (right). ..................................................................................................................6 

Figure 7. Total stress computed by EPIC for the 1.25-in wall projectile, near the projectile 

forebody (left) and in the middle of the projectile tail (right). The blue lines show the 

results from the axisymmetric geometry, and the red lines show the results with the 

rotated projectile. The stress values did not notably diverge until after 4.5 ms. ......................7 

Figure 8. Total stress computed by EPIC for the 1.25-in wall projectile, near the projectile 

forebody (left) and in the middle of the projectile tail (right) using the pressure in the left 

half of figure 3 (blue) and from a minimal-interphase-drag ARL-NGEN3 simulation 

(red). The maximum stress for the latter case is around 150 ksi. .............................................8 

Figure 9. Total stress computed by EPIC for the 0.5-in wall projectile, near the projectile 

forebody (left) and in the middle of the projectile tail (right). Note the much larger 

oscillations and higher peak stress compared to figure 6. .........................................................9 

Figure 10. Total stress in the projectile at 2.4 and 4.4 ms into the gun firing. These times 

correspond to the two peaks in the plots in figure 9. The red regions are where the stress 

has surpassed 200 ksi (1.38 GPa), so it is very unlikely that any conventional metal could 

have survived this gun launch....................................................................................................9 

Figure 11. Geometry of the 0.5-in wall projectile carrying four disks; the disk colors 

correspond to the lines in figure 12. Each disk is held loosely in place by a ridge of steel 

on either side............................................................................................................................10 

Figure 12. Mass-weighted average of the acceleration of the disks shown in figure 11. The 

disks are numbered in order with disk 1 on the left (rearmost disk) and disk 4 on the right 

(foremost disk). The line colors correspond to the disk colors in figure 11. ..........................11
1

1. Introduction 

The interior ballistics environment of the case-telescoped ammunition (CTA) is quite 

challenging since the gun chamber, normally occupied by the solid propellant charge and a 

projectile afterbody of small diameter and significant taper, is redesigned so that fully onequarter of the available chamber volume is occupied by a projectile afterbody of large constant 

diameter. Concurrently, an acceptable level of projectile muzzle velocity must be maintained so 

that the propellant loading density of the gun chamber is quite high. Ignition of this 

tightly-packed charge results in axial pressure waves of such significant amplitude and frequency 

that the survivability of the projectile must now be called into question. What is needed is an 

approach that couples the numerical codes used for charge design and the numerical codes that 

model the structural response of the projectile so that the ammunition designer can arrive at a 

solution that guarantees the successful launch of a useful payload at a lethal velocity. 

Modern interior ballistics (IB) simulation codes are generally capable of modeling the ignition, 

flamespreading, and combustion of densely-packed advanced charges, even those that include a 

variety of propellant shapes, such as grains, sticks, disks, and concentric wraps. Most IB codes 

cannot specifically simulate the CTA configuration since the presence of the projectile afterbody 

represents both an axially discontinuous and a numerically significant area change in the gun 

chamber. The U.S. Army’s ARL-NGEN3 code is a multidimensional, multiphase computational 

fluid dynamics (CFD) code (1–3). The IB flowfield simulation using this code consists of a 

discrete component (the propellant) and a continuous component (the gases initially in the 

chamber and generated by propellant combustion). To capture both types of components, the 

ARL-NGEN3 code uses a uniquely coupled Eulerian-Lagrangian approach (1–3). Previous work 

has reported the utility of the ARL-NGEN3 code in simulating the CTA configuration (4) 

including the simulation of large amplitude pressure waves around the projectile afterbody and 

an unsteady pressure loading of the projectile surface. 

While IB codes accurately compute the motion of the projectile, they do so while treating it as a 

rigid body. Such codes cannot model the full response of the projectile to the pressure load 

imposed on its surface. Vibration and possible damage to or deformation of the projectile are 

excluded from IB models. These mechanical effects can be simulated using modern 

computational solid mechanics (CSM) codes, such as DYNA3D (5) and EPIC (6). DYNA3D 

and EPIC are both explicit finite-element codes for structural mechanics problems. When the 

deformation of the projectile is limited to the elastic regime and contact between the projectile 

and the gun tube occur at relatively low speeds, the accuracy of both the EPIC and DYNA codes 

on such problems has been demonstrated; therefore, one expects both EPIC and DYNA to give 

very accurate results in the IB simulation environment. 
2

2. Description of Test Case 

There are several goals in the first part of this work; among them is a demonstration of the 

accuracy, efficiency, and capabilities of the proposed CFD/CSM coupled modeling approach and 

a determination that the results from DYNA3D and EPIC codes are comparable. To meet these 

goals, a simplified version of the projectile and charge for a notional large-caliber CTA 

configuration was defined for this work (4, 7–10). Figure 1 shows the geometry of the projectile 

afterbody, or tail, and the gun chamber. The chamber is axisymmetric in shape, with no tapering 

or chambrage, and its diameter and initial length are 14 cm (5.5 in) and 84 cm (33.1 in), 

respectively. The intruding projectile tail is also axisymmetric in shape, with an outer diameter 

of 8 cm (3.1 in) and length of 70 cm (27.6 in); the presence of a projectile boattail (i.e., tapered 

afterbody) and/or aerodynamic fins were excluded for simplicity. 

Figure 1. Axisymmetric representation of notional CTA configuration – 

chamber, projectile afterbody, and four propellant regions shown. 

Note that region IV fills the annular volume (4). 

The chamber shown in figure 1 was divided into four regions, each containing a different 

propellant and/or different propellant geometry. Region I contained 25 g of M1 propellant, 

which is initially ignited to start the ARL-NGEN3 simulation, and region II contained 25 g of 

black powder. Regions III and IV were filled with seven-perforated JA2 granular propellant to a 

loading density of 0.9 g/cm3

. 

Figure 2 shows the geometry of the projectiles used in the EPIC and DYNA3D simulations. The 

codes used slightly different geometries for reasons dealing with the mesh generators used for 

each of the codes and that will be further discussed later. The sole geometric difference between 

the two projectiles was that the projectile nosetip was truncated for the projectile used in the 

DYNA3D simulations. All of the walls of the projectiles were assumed to be 1.25 in (3.175 cm) 

thick in the first set of simulations. With the EPIC code, a second set of simulations was run in 

which the walls of the projectile were 0.5 in (1.27 cm) thick. The outer geometry of that 

projectile was identical to that in the left side of figure 2. The projectiles were assumed to be 

made of steel; however, the density of the steel was artificially lowered in order to match the 

40-lb projectile weight used in the ARL-NGEN3 simulations. 
3

Figure 2. Geometry of the notional CTA projectile and the surface of the mesh used in the EPIC simulation (left) 

and the DYNA3D simulation (right). 

3. ARL-NGEN3 Results 

Detailed results from an axisymmetric ARL-NGEN3 simulation of this problem were previously 

published (4, 7–10). The graph on the left of figure 3 shows the pressure from the ARL-NGEN3 

simulation at the points labeled “R,” “M,” and “F” in figure 1. Notice that there is a pressure 

spike that occurs at different times for the three axial locations. This is an indication of the 

strong pressure wave that moves axially through the chamber. The mass of the projectile used in 

the ARL-NGEN3 simulation was 18.1 kg (weight of 40 lb). Given that weight limit, the pressure 

load shown in the left half of figure 3 was likely strong enough to damage or destroy a projectile 

made of any conventional material. 

Figure 3. Pressure-time curves predicted using the ARL-NGEN3 code for geometry shown in figure 1 – results for 

the locations labeled “R,” “M,” and “F” along the chamber wall: granular propellant (left) and concentric 

wrap propellant in region IV having minimal axial interphase drag (right). Note that the scales in the 

right-hand picture are lower than those on the left (4, 9). 

The pressure waves seen in the left half of figure 3 arose from several factors, including the high 

loading density, the geometry of the projectile afterbody, and the resistance to the propellant in 

region IV (see figure 1) to the axial flow of the high-pressure gas generated during propellant 

ignition. Another simulation from ARL-NGEN3 explored the effects of the latter factor. In this 

simulation, the propellant in region IV was assumed to be a concentric wrap propellant with the 

same thermodynamic characteristics of seven-perforated JA2 granules but with minimal 

resistance to gas flow in the axial direction (9, 10). The line plot on the right in figure 3 shows 
4

the pressure at three locations in the combustion chamber. The chamber is seen to pressurize 

more evenly as the pressure waves have been damped significantly. The peak pressure is about 

one-third less than in the previous case and as a result a projectile made of a conventional 

material might be able to survive the launch. The drop in muzzle exit velocity, however, is 

noticeable: 1470 m/s in the former case and 1400 m/s in the latter. Detailed ARL-NGEN3 code 

results for these simulations, including contour plots of the gas pressure and propellant porosity 

fields are available in reference (10).

4. EPIC/DYNA3D Comparison 

In a real gun system any amount of plastic deformation of the projectile is unacceptable. So in 

the present solid mechanics simulations the projectile material was assumed to respond 

elastically throughout the gun-firing simulation. The simulations determined if, when, and 

where the projectile deformed plastically, but they did not predict the effects of such 

deformation. Limiting the response to the elastic regime simplified the problem, and the results 

from DYNA3D and EPIC were expected to agree with each other quite well. 

The pressure on the surface of the projectile afterbody computed by ARL-NGEN3 was used as 

input by DYNA3D and EPIC to simulate the mechanical response of the projectile. The 

geometry of the projectile and the mesh on its surface used in the EPIC and DYNA3D 

simulations was shown in figure 2. The fine details of the mesh were not expected to affect the 

computed response in any appreciable way. Mesh generators that came packaged with 

DYNA3D and with EPIC were used to generate the meshes employed during the respective 

simulations. Therefore, while the size and number of elements in the two meshes were close, the 

meshes were not identical. Based on the algorithms used in the EPIC mesh generator, removing 

the point of the projectile’s nose would hurt the time-step size, while in the other mesh generator, 

including the nose would hurt the time-step size. Provided the mass of the projectiles is equal, 

the presence or absence of the nose was expected to have very little effect. 

A set of simulations was run in order to compare the results from EPIC and DYNA3D; as 

previously mentioned, the results should agree very well. The 1.25-in wall projectiles were used 

in these cases. In these simulations, a smaller pressure file from ARL-NGEN3 was used. In 

order to get this file, the pressure was taken from ARL-NGEN3 every 200 μs, even though 

pressure data was available roughly every 0.3 μs; the resulting reduced pressure set was referred 

to as the “sparse” pressure set. Using the sparse pressure set removed a potential source of noise 

that would make comparisons more difficult. Figure 4 shows the total stress computed by EPIC 

and by DYNA3D at two points on the projectile tail, one near the back of the projectile forebody, 

and one roughly halfway along the tail. The DYNA3D results were previously presented (4, 8–10). 

The meshes used in the simulations were not identical, and so the exact locations where the 

stress was measured were slightly different in the EPIC simulations versus the DYNA3D 
5

simulations. Nonetheless, the results of the two codes in figure 4 are quite close, agreeing well 

on the amplitude, frequency, and phase of the oscillations. Figure 5 shows the total stress at 

2.4 ms into the gun firing as computed by EPIC and DYNA3D. Again, the agreement between 

the two solid mechanics codes is very good, even with the slight variation in geometry and mesh. 

Based on the good agreement and previous validation of the codes, both codes were expected to 

generate accurate results for this class of problems. The EPIC code was used to generate all of 

the solid mechanics results presented in the remainder of this report. 

Figure 4. Total stress computed by EPIC (solid line) and DYNA3D (dashed line) near the back of the projectile 

forebody (left) and near the midpoint of the projectile tail (right). 

Figure 5. Total stress at 2.4 ms into the gun firing computed by DYNA3D (left) and EPIC (right), near the time of 

the highest total stress. The red region is where the total stress surpassed 90 ksi (621 MPa); the material 

likely would have failed and the projectile damaged in that region. 

The stresses shown in figure 4 show a strong frequency at about 4 kHz and then after 8 ms 

another mode starts to be excited with a frequency at about 8 kHz. These are both natural 

frequencies of the projectile. Recall that the solid mechanics and fluid dynamics solvers are not 

fully coupled. Therefore, there is neither damping of the solid vibrational modes nor shifting of 

the projectile’s natural frequencies by the gas. 

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5. Further EPIC Results – 1.25-in Wall Projectile 

A simulation was run with EPIC using the full pressure set from ARL-NGEN3. This simulation 

was run on a SGI Origin 3800 at the U.S. Army Research Laboratory (ARL) Major Shared 

Resource Center. The full data set was too large for EPIC to read into memory, so the simulation 

was broken up into several pieces. Figure 6 shows the stress computed at the same locations as 

in figure 4 using the two data sets. The peak stress is much higher with the full pressure set, and 

the overall response is more oscillatory. 

Figure 6. Total stress computed by EPIC using the full data set (red line) and the sparse data set (blue line) near 

the back of the projectile forebody (left) and near the midpoint of the projectile tail (right). 

As mentioned earlier, the full pressure set was too large for the machine being used. So, the 

pressure was taken from every fourth time level in ARL-NGEN3’s data set, and this reduced set 

was called the “quarter” data set. This data set did fit within the memory of the SGI Origin 

3800. Another EPIC simulation used the quarter pressure set, and the results were compared 

with those that came from the EPIC simulation using the full data set, which are shown in 

figure 6. The two sets of lines almost perfectly overlaid each other, having no visible 

differences, so the results are not shown here. All of the rest of the simulations were performed 

using the quarter set. 

A fast Fourier transform of the pressure from ARL-NGEN3 was performed in order to identify 

the dominant frequencies of the input data. Figure 3 showed line plots demonstrating the trends 

in the pressure in the gun chamber. The ARL-NGEN3 code uses explicit time-stepping, so the 

time-step size varied during the simulation, and the code wrote out the pressure at every time 

step. The pressure was taken every 9.3 μs in order to perform the FFT. The analysis revealed 

that the pressure data had a strong mode near 100 Hz and progressively weaker oscillations near 

500, 1100, and 1700 Hz. The 100-Hz mode was simply the average pressure rise and fall 

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during the gun firing. The 500-Hz mode was the axially-moving pressure wave that appeared as 

the double peak in the left half of figure 3. 

The frequencies of the computed results from the simulated launch of the 1.25-in-thick wall 

projectile using the quarter pressure set were determined. As expected, there were very strong 

signals at 100 and 500 Hz, with slightly weaker signals at 1100 and 1700 Hz. These were the 

forced modes coming from the pressure computed by ARL-NGEN3. In addition, there was a 

very strong signal at 3.7 kHz, with other peaks at 3.2, 7.4, 8.5, and 22.8 kHz, as well as other 

smaller peaks. These frequencies are probably all-natural frequencies of the projectile. 

6. Initial Rotation of Projectile 

In another simulation, the projectile was initially rotated along the long axis by 1°, i.e., raising 

the nose while lowering the tail. In order to accommodate this change, the inner and outer 

diameters of the gun tube were slightly increased. Such changes would be expected to affect the 

ignition, flamespreading, and combustion during the firing cycle, but that effect was neglected, 

and the pressure computed by ARL-NGEN3 using the axisymmetric geometry was used in this 

simulation. Figure 7 shows the total stress at the same two locations in the projectile tail as in 

figure 6. The projectile began to move about 1.5 ms into the firing cycle, and contact with the 

chamber wall was first made shortly thereafter. It is interesting to note that, comparing this case 

with the previous (the axisymmetric projectile placement), the computed stress agreed very well 

until much later in the firing cycle, about 4.5 ms. After that point, the stress is overall higher in 

the case with the initially-rotate projectile. 

Figure 7. Total stress computed by EPIC for the 1.25-in wall projectile, near the projectile forebody (left) and in the 

middle of the projectile tail (right). The blue lines show the results from the axisymmetric geometry, and 

the red lines show the results with the rotated projectile. The stress values did not notably diverge until 

after 4.5 ms. 

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7. Propellant With Minimal Interface Drag 

A desirable feature of the propellant loaded into region IV (see figure 1) is low interphase drag 

(resistance to flow) in the axial direction. An ARL-NGEN3 simulation studied the limiting case, 

in which the granular propellant in region IV had no interphase drag (9). The computed pressure 

looked very similar to that shown in the right half of figure 3, in which, because of the concentric 

wraps in region IV, there is nearly no axial interphase drag. The launch of the projectile in the 

initial axisymmetric placement was studied using the pressure results from the no-interphasedrag simulation. Figure 8 shows the total stress from the EPIC simulation along with a repeat of 

the computed stress from the case first shown in figure 6. The projectile stress for the no-drag 

propellant does not peak until much later and the maximum is lower than for the real propellant 

charge. Given the weight limit on the projectile, it would still be a challenge to design a 

projectile to survive this environment, but it might be possible. 

Figure 8. Total stress computed by EPIC for the 1.25-in wall projectile, near the projectile forebody (left) and 

in the middle of the projectile tail (right) using the pressure in the left half of figure 3 (blue) and from a 

minimal-interphase-drag ARL-NGEN3 simulation (red). The maximum stress for the latter case is 

around 150 ksi. 

8. The 0.5-in Wall Projectile 

A second projectile geometry was used in simulations; in this one, the walls of the projectile are 

0.5 in thick. Again, the density of the metal was adjusted so that the mass of the projectile was 

18.1 kg. EPIC simulated the launch of this projectile using the quarter pressure set coming from 

the ARL-NGEN3 simulation involving granular propellant in region IV (shown in the left picture 

of figure 3). Figure 9 shows the total stress at two points along the projectile tail. The maximum 

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total stress in this case was much higher than previously, surpassing 350 ksi (2.4 GPa), beyond 

the yield stress of most metals. The stress was also noisier than in the previous cases. This 

should all be expected and was caused by the decrease in the wall thickness. Figure 10 shows 

the total stress in the projectile at 2.4 and 4.4 ms into the simulation. As can be seen in the 

pictures, it is very unlikely that a projectile made of any conventional metal could have survived 

the high stresses. 

Figure 9. Total stress computed by EPIC for the 0.5-in wall projectile, near the projectile forebody (left) and in 

the middle of the projectile tail (right). Note the much larger oscillations and higher peak stress 

compared to figure 6. 

Figure 10. Total stress in the projectile at 2.4 and 4.4 ms into the gun firing. These times correspond to the two 

peaks in the plots in figure 9. The red regions are where the stress has surpassed 200 ksi (1.38 GPa), 

so it is very unlikely that any conventional metal could have survived this gun launch. 

9. Projectile With Payload 

As previously stated, one of the goals of this work is a demonstration of the capabilities of a 

coupled CFD/CSM approach to studying gun launches. One of the capabilities lays in the study 

of a payload launched aboard the projectile. The projectiles are hollow and could carry some 

type of payload, perhaps an explosive or some type of electronics package; the 0.5-in wall 

projectile especially has a lot of available volume. We know from the work that a 0.5-in wall 

projectile made of a conventional material probably would not survive the launch. But if the 

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notional projectile were made of some yet-to-be-determined material that met the weight and 

strength requirements posed by the pressure load, then the issue becomes what type of loading 

the payload would experience. To study this, four disks were placed at different locations inside 

of the projectile. Figure 11 shows the inside of the projectile with the disks. All of the disks 

were flat circular plates of polycarbonate to represent perhaps a type of electrical component 

aboard the projectile, and the deformations of the disk were limited to the elastic regime. The 

foremost disk had a diameter of 10.7 cm (4.2 in) and a thickness of 3.9 cm (1.5 in), and the 

diameter and thickness of the other disks were 5.2 cm (2.0 in) and 1.3 cm (0.52 in), respectively. 

Figure 11. Geometry of the 0.5-in wall projectile carrying four disks; the disk colors 

correspond to the lines in figure 12. Each disk is held loosely in place by 

a ridge of steel on either side. 

In order to study the survivability of the disks shown in figure 11, it could be important to know 

the vibrational load and frequencies to which they were subjected. Figure 12 shows the massweighted average of the acceleration of the four disks as a function of time. The foremost disk 

(the green line in figure 12) showed the least oscillations, likely caused by the fact that it was by 

far the largest of the disks and that the projectile forebody probably vibrated less (in terms of 

amplitude) than did the projectile tail. The disk midway along the projectile tail (the red line in 

figure 12) showed the most oscillations. Why that happened has not yet been determined, but it 

likely was caused by the vibrational modes of the projectile tail that were excited during the gun 

launch. 

In addition to the magnitude of the acceleration, the frequencies at which the disks vibrate could 

also be important, especially if they were electronic components. All of the signals showed 

100-, 500-, and 1100-Hz frequencies, all seen in the pressure input. Above that, the disks 

vibrated at 2.5, 5.5, 9 (a rather strong signal), and 13 kHz, and at other higher frequencies. Not 

all of the disks vibrated with every one of these frequencies. There are methods for reducing the 

vibrational load on the disks, but none were studied in this work. For instance, the disks were 

allowed to move a little between the steel ridges holding them in place. Other means of securing 

the disks in place could also have the effect of reducing the vibrational load transmitted to the 

disks. 
11

-2.E+05

0.E+00

2.E+05

4.E+05

6.E+05

8.E+05

1.E+06

0 2 4 6 8 10

Time (ms)

Disk 2

Disk 1

Disk 3

Disk 4

Figure 12. Mass-weighted average of the acceleration of the disks 

shown in figure 11. The disks are numbered in order 

with disk 1 on the left (rearmost disk) and disk 4 on the 

right (foremost disk). The line colors correspond to the 

disk colors in figure 11. 

10. Summary and Conclusions 

The interior ballistics environment of the CTA is quite challenging since the gun chamber, 

normally occupied by the solid propellant charge and a projectile afterbody of small diameter 

and significant taper, are altered so that fully one-quarter of the available chamber volume is 

occupied by a projectile afterbody of large constant diameter. Concurrently, an acceptable level 

of projectile muzzle velocity must be maintained so that the loading density of the gun chamber 

is quite high. Ignition of this tightly-packed charge results in axial pressure waves of such 

significant amplitude and frequency that the survivability of the projectile must now be called 

into question. What is needed is an approach that couples the numerical codes used for charge 

design (ARL-NGEN3) and the numerical codes that model the structural response of the 

projectile (DYNA3D and EPIC) so that the ammunition designer can arrive at a solution that 

guarantees the successful launch of a useful payload at a lethal velocity. The current paper has 

demonstrated that propellant ignition, flamespreading, and combustion results generated using 

the ARL-NGEN3 code, can be as successfully linked to the EPIC code as was previously 

demonstrated for the DYNA3D code. Results from EPIC and DYNA3D, as expected, compared 

quite well with each other. This modeling effort will continue, with results from ARL-NGEN3 

and EPIC being compared with experimental data coming from the work described in (11).
12

11. References 

1. Gough, P. S. Formulation of a Next-Generation Interior Ballistic Code; ARL-CR-68; U.S. 

Army Research Laboratory: Aberdeen Proving Ground, MD, September 1993. 

2. Nusca, M. J.; Gough, P. S. Numerical Model of Multiphase Flows Applied to Solid 

Propellant Combustion in Gun Systems; AIAA Paper No. 1998-3695, July 1998. 

3. Nusca, M. J.; Conroy, P. J. Multiphase CFD Simulations of Solid Propellant Combustion in 

Gun Systems; AIAA Paper No. 2002-1091, January 2002. 

4. Nusca, M. J.; Horst, A. W. Progress in Multidimensional, Two-Phase Simulations of 

Notional Telescoped-Ammunition Propelling Charge. Proceedings of the 39th JANNAF 

Combustion Subcommittee Meeting, Colorado Springs, CO, December 2003; CPIA 

Publication JSC CD-25. 

5. Whirley, R. G.; Engelmann, B. E. DYNA3D – A Nonlinear, Explicit, Three-Dimensional 

Finite Element Code for Solid and Structural Mechanics; UCRL-MA-107254 (Rev. 1); 

Lawrence Livermore National Laboratory: Oak Ridge, TN, November 1993. 

6. Johnson, G. R.; Stryk, R. A.; Holmquist, T. J.; Beissel, S. R. Numerical Algorithms in a 

Lagrangian Hydrocode; WL-TR-1997-7039; Wright Laboratory: Eglin Air Force Base, FL, 

June 1997. 

7. Horst, A. W. Weapon System Constraints on Advances in Gun Propulsion. Proceedings of 

the 5th Joint Classified Bombs/Warheads and Ballistics Symposium, Colorado Springs, CO, 

1–2 June 2002. 

8. Newill, J. F.; Nusca, M. J.; Horst, A. W. Advances in Coupled Projectile-Dynamics/InteriorBallistics Simulations: Coupling the DYNA3D Code and the ARL-NGEN3 Code. 

Proceedings of the 21st International Symposium on Ballistics, Adelaide, South Australia, 

April 2004.

9. Nusca, M. J.; Horst, A. W.; Newill, J. F. Multidimensional, Two-Phase Simulations of 

Notional Telescoped-Ammunition Propelling Charge. Proceedings of the 52nd JANNAF 

Propulsion Meeting, Las Vegas, NV, May 2004; CPIA Publication JPM CD-04. 

10. Nusca, M. J.; Horst, A. W.; Newill, J. F. Multidimensional, Two-Phase Simulations of 

Notional Telescoped-Ammunition Propelling Charge; ARL-TR-3306; U.S. Army Research 

Laboratory: Aberdeen Proving Ground, MD, September 2004. 
13

11. Williams, A. W.; Colburn, J. W.; Howard, S. L.; Brant, A. L.; Nusca, M. J.; Newill, J. F. 

Full-Scale Simulator Studies of a Notional Telescoped-Ammunition Charge. Proceedings of 

the 40th JANNAF Combustion Subcommittee Meeting, Charleston, SC, June 2005. 
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