The objective was to develop a model of internal ballistics in solid rocket motors to model case breach faults and provide early warning. The model couples PDEs for gas dynamics with ODEs for grain regression, nozzle ablation, and fault dynamics. It was verified against high-fidelity simulations and able to accurately predict nominal and off-nominal regimes. An algorithm was developed to infer fault parameters in-flight and predict fault evolution. Operational envelopes were created showing regions of failure for case breaches at different times and positions.

1. HF Fluent model
velocity distribution
Case Breach Fault in Solid Rocket Motor:
System Modeling, FD&P for sub-scale SRB from ground tests data
THE OBJECTIVE is to develop SRM early warning system: uses the direct
detection sensor data and provides a real-time learning of the parameters of the
set of low-order physics models for onset and progression of system faults and
autonomously generates the robust prediction of fault evolution for a possible
decision on a safe crew abort. Models include prior knowledge of thermal, fluid
dynamics and material processes in SRM.
Approach and key results
• We develop a model of the SRM internal dynamics in the presence of the
case breach fault. The model is verified using FLUENT high-fidelity
simulations.
• The model is applied to reconstruct dynamics of the fault (area of the hole
in the forward pressure) and thrust dynamics.
• Algorithms for realtime fault detection and forward prediction were
developed0 2 4 6 8 10
-400
0
400
800
1200
1600
t, sec
F
total
,lbf
measured
filtered measurements
nozzle thrust
breach thrust
total
0 2 4 6 8 10
0
200
400
600
800
1000
1200
t, sec
p,psi
RECONSTRUCTED THRUST DYNAMICS
Time window used for diagnostics of
the fault parameters
Prediction of the pressure 8 sec
forward in time
( )
( ) ( )
1
0 0
1 1
max 0
0
2 2
0
( ), ,
( ), ,
net b Nt
p Nt m
Nt
net b c
p h b
m m mel m m
c A A p Rp
p a t R v
Va V p R
c A A Qp
p p p p a t R v
Va V q C T T
β β
ρ ρ ρ ρ ξ
ρ
γ
γρ ξ
ρ ρ
− −
   Γ
=− + − + =   
   
Γ
=− + − + = +
+ −  



2. Convergence of the predictions for the case breach area (top) pressure
(middle) and thrust (bottom). The nominal values of the pressure and
thrust are shown by blue solid lines. The mean predicted values are
shown by red dashed lines. The shaded green areas indicate twice
standard deviation of the predicted values.
The gimbal tuning envelope illustrating the three regions for a case
breach applied at the point closest to the igniter along the rocket at
0 deg. The figure shows each side thrust profile for each onset time
for the given position. The region of failure was determined by a
minimum altitude requirement.
THE OBJECTIVE of the project was to develop model of internal ballistics of large segmented motor in off-nominal
regimes and an algorithm for diagnostic & prognostic of the case breach fault. The model consists of a set of
coupled PDEs for gas dynamics and ODEs for the grain regression, nozzle ablation, and fault dynamics. It is solved
by integration in a regime of steady burning to obtain spatial distributions of the state variables with a time
resolution up to 0.1 sec. We verify the solution by comparison with the results of high-fidelity simulations
performed by 3rd party.
THE RESULTS
• The model of internal ballistics of the SRB was developed that reproduces very accurately results of the
proprietary ATK code and allows one to predict nominal and a number of off nominal regimes (bore chocking,
nozzle blocking, case breach, propellant cracking).
• An algorithm for in-flight inference of the fault parameters is derived.
• An operational envelopes for the ascent of the SRB in the presence of case breach fault were created.
FAULT INITIATION
LEARNING TIME
PREDICTION TIME
0 20 40 60 80 100 120
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
x 10
5
time (sec)
SideThrust(lbf)
Side thrust vs fault start time
Sidethrust(lbf)
0 20 40 60 80
100 120
2
1.6
1.2
0.8
0.4
0
x106
Time, sec
MISSION LOSS REGION
STABILITY LOSS OF THE TVC
0 10 20 30 40
600
700
800
900
x, m
p(t,x),psi
Case breach in multi-section solid rocket booster:
internal ballistics modeling and vehicle trajectory simulations