1. 5/29/2016
FS/US separation failure: Analysis and simulations (ETDP ISHM Work for FY09/FY10)
Re-contact trajectory
• If two BDM fail on one side of the FS the stage
separation fail.
• The geometrical parameters and velocities of
the re-contact were determined for two BDM
failure.
Objective: develop model and high-fidelity simulations, suggest sensors and detection
algorithm for the complex boundary problem, when it is difficult to decide whether
the mission has to be cancelled or not.
Re-contact trajectory for two BDM
failure. The nozzle extension can be seen
through the inter-stage mesh.
Nozzle deformation
• FE model of the re-contact was build using
ABAQUS explicit. The model include
temperature dependent elastic and plastic
parameters of the nozzle extension material.
• Analysis of the re-contact shows
o Plastic buckling of the nozzle edge
o Bending of the nozzle extension as a whole
o Degradation of the whole nozzle surfaces on
the buckled side
• Analytical estimations and analysis of the
nozzle extension eigen-modes confirm the
conclusion that the result of the re-contact is
nozzle buckling
Y
Z
216.14 in
364.14in
Tstart=130.34 (sec) Tend =130.45 (sec)
Vlat start=3.91 (ft/sec) Vx start=18.40 (ft/sec)
Vlat end =4.12 (ft/sec) Vx end =18.48 (ft/sec)
Dt=0.11 (sec) DL=5.32 (in) DX=24.35 (in)
(a) Nozzle buckling caused by the re-
contact ; (b) One of the eigen-modes of
the nozzle; (c) reaction forces at the fixed
nozzle origin.
8.2 cycles/sec
0 20 40 60 80 100 120 140 160 180
-800
-600
-400
-200
0
200
400
600
θ, deg
Reactionforce,lbf
RX – black; RY
– blue; RZ - red
0.2 sec
(a)
(b)
(c)
Effect of the hot gas flow on the deformed
nozzle
• Formation of the separation shock waves
result in elevated to several atm pressure and
rise of the temperature above 3000K at the
buckled wall.
• FE modeling of the combined effect of heat
flow and pressure shows that thing nozzle
shells at the buckled part will be melt and cut
off by the flow within 0.3 sec.
130.4 130.6 130.8 131 131.2 131.4
-5
-4
-3
-2
-1
0
1
2
3
x 10
5
time, sec
ReactionTorque
case4_
case5_
case2_
case3_
case7_
0 0.2 0.4 0.6 0.8 1
-4
-2
0
2
4
6
x 10
-3
time, sec
Response,Y(t)
Response
Impact
Transient Torque
We calculate transient
torque due to impact.
The response has a form
of damped oscillator
response and can be used
to infer the strength of
the impact and to
estimate the fault
induced damaged of the
nozzle extension on-
board.
1.5 2 2.5 3 3.5
0
1
2
3
4
x 10
4
P,[Pa]
x, m
(a)
NozzleRadius
Axial Position
0 0.25 0.5 0.75 1
0
2
4
6
P/P0
×10
-3
r/R
Nozzle pressure
(b)
2D model of the transient nozzle
flow
We build 2D model of transient
model flow and calibrate it using
exact numerical solution for the
transient flow.
Aftershock
The 2D analytical model of the transient
flow is used for estimation of the transient
pressure and temperature load on the
damaged part of the nozzle due to
formation of the shock wave at the bending
corner of the damaged area of the nozzle.

2. 5/29/2016
FS/US separation failure: Analysis and simulations (ETDP ISHM Work for FY09/FY10)
(a)
(b)
(c)
(d)
(a) Combined effect of the heat flow and
pressure on the thin nozzle shells; (b) Hot
gas flow through the nozzle with cut through
fault; (c) transient stress and temperature in
the thing shell of the nozzle extension; (d)
side thrust as a function of the fault area.
Estimation of the thrust in FLUENT
• FLUENT model of the hot gas flow through
the nozzle in the external free stream was
built. The fault was modeled as a cut through
the nozzle in accordance with the results of
the analysis in the previous section.
• Thrust changes were estimated as a function
of the fault area.
• For the fault area corresponding to two BDM
failure side thrust and fault induced changes
of the main thrust are proportional to the fault
are.
• The side thrust and changes of the main thrust
may be up to 1.5% of the nominal thrust.
• The main conclusion is that fault induced
changes of the thrust are unsustainable.
Summary
 Case of two BDM failure was analyzed. Re-
contact trajectory and corresponding nozzle
deformation were estimated
 The ABAQUS explicit FE model of the re-
contact was developed that shows: (i) plastic
buckling of the nozzle edge; (ii) bending of the
nozzle as a whole ; (iii) degradation of the
whole nozzle surfaces on the buckled side.
 Analysis shows that the most plausible
combined effect of the heat flow and pressure
on the nozzle is cutting off its buckled part.
 Changes of the main and side thrust in the
damaged nozzle were estimated to be of the
order of 98.5% and 1.5% respectively.
 The transient fault induced main and side
thrust and torque are estimated analytically
and using FLUENT model.
 To detect the unsustainable deformation of the
nozzle during the re-contact we suggest to
include detection of the re-contact moment
into the TVC scheme and addition of a set of
break wires and strain gages along the external
circumference of the nozzle extension inlet.
(a)
break-wire
activation sensors
Strain gauges
Maximum strain is
about 10-2
(b)
(a) Rock actuator diagram with re-contact
torque block ; (b) set of break-wires to
detect unsustainable strain during recontact.
0 0.05 0.1 0.15 0.2
0
0.5
1
1.5
2
x 10
5
time, sec
ReactionTorque
press_heat_
bending begins
melting begins
X105
Reversed buckling and
melting in the flow
We apply transient pressure
and temperature loads
determined analytically for the
aftershock flow to ABAQUS
FEM of the nozzle to estimate
time scale of the reversed
buckling and melting of the
damaged area induced by the
flow.
Reversed dynamics of the pressure
load.
We substitute the results of the analysis
of the reversed buckling and melting
back into analytical model of the
transient flow and estimate pressure and
temperature loads on the wall during
reversed buckling and melting. 1.8 2 2.2 2.4 2.6 2.8 3 3.2
0
1
2
3
4
5
6
7
8
9
x 10
4
P,[Pa]
time, sec
exit
wall
α1
= 90o
α2
= 30o
α3
= 50o
bending begins
melting begins
131 132 133 134
-60
-40
-20
0
20
40
T×104,N⋅m
time, sec133.4 133.6 133.8 134 134.2 134.4 134.6
-2
-1.5
-1
-0.5
0
F
main
,[%]
t, sec
133.4 133.6 133.8 134 134.2 134.4 134.6
0
0.5
1
1.5
F
side
,[%]
t, sec
Fault-induced transient torque and thrust.
The results of analytical calculations and numerical estimations (in
ABAQUS and FLUENT) are used to predict the overall transient re fault
induced torque and thrust due to FS/US separation failure caused by two
BDM failure.
Main thrust change in % Side thrust change in %