ses overview on et foam revised - nasa · pdf filean overview of spray-on foam insulation...
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An Overview of Spray-On Foam InsulationApplications on the Space Shuttle’s ExternalTank: Foam Applications and Foam Shedding
MechanismsRoy M. Sullivan∗ ‡
Research EngineerBradley A. Lerch∗
Research EngineerPatrick R. Rogers†
Aerospace Engineer
Jeffery S. Sparks†Materials Engineer
The Columbia Accident Investigation Board (CAIB) concluded that the cause of the tragicloss of the Space Shuttle Columbia and its crew was a breach in the thermal protection systemon the leading edge of the left wing. The breach was initiated by a piece of insulating foamthat separated from the left bipod ramp of the External Tank and struck the wing in thevicinity of the lower half of Reinforced Carbon-Carbon panel No. 8 at 81.9 seconds afterlaunch. The CAIB conclusion has spawned numerous studies to identify the cause of andfactors influencing foam shedding and foam debris liberation from the External Tank duringascent.
The symposium on the Thermo-mechanics and Fracture of Space Shuttle External TankSpray-On Foam Insulation is a collection of presentations that discuss the physics and me-chanics of the ET SOFI with the objective of improving analytical and numerical methodsfor predicting foam thermo-mechanical and fracture behavior. This keynote presentation setsthe stage for the presentations contained in this symposium by introducing the audience tothe various types of SOFI applications on the Shuttle’s External Tank and by discussing thevarious mechanisms that are believed to be the cause of foam shedding during the Shuttle’sascent to space.
∗Mechanics and Lifing Branch, NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH44135
†NASA Marshall Space Flight Center, Marshall Space Flight Center, AL 35812‡Corresponding Author; Contact Email: [email protected]
Session-PaperNumber
https://ntrs.nasa.gov/search.jsp?R=20070008105 2018-05-18T16:58:49+00:00Z
1G
lenn
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earc
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ente
r at L
ewis
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ld
An
Ove
rvie
w o
f Spr
ay-O
n Fo
am In
sula
tion
App
licat
ions
on
the
Spac
e Sh
uttle
’s E
xter
nal T
ank:
Foa
m A
pplic
atio
ns
and
Foam
She
ddin
g M
echa
nism
s
Roy
M. S
ulliv
an a
nd B
radl
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. Ler
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2G
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The
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mp
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ctP
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Pos
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5G
lenn
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earc
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The
Spac
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uttle
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ank
6G
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earc
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•Len
gth:
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met
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7G
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9G
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Exte
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ray-
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latio
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10G
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Ext
erna
l Tan
k’s S
pray
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sula
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(SO
FI)
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pplie
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ualit
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ting.
11G
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12G
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Res
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Fie
ld
13G
lenn
Res
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ld
Acr
eage
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m•A
utom
ated
spra
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CFI
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ual C
lose
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•Spr
ayed
or m
olde
d ar
ound
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ngs/
flang
es w
here
aut
omat
ed
spra
ying
is n
ot p
ossi
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ual S
pray
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olyu
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ded
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se-o
uts:
PD
L-10
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olyu
reth
ane)
Exte
rnal
Tan
k Sp
ray-
On
Foam
Insu
latio
n (S
OFI
)
14G
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Bip
od F
ittin
g an
d R
amp
Clo
seou
t
15G
lenn
Res
earc
h C
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r at L
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Fie
ld
Prot
rusi
on A
ir L
oad
(PA
L) R
amp
Add
ed e
arly
in S
huttl
e P
rogr
am to
avo
id a
ny p
oten
tial a
erod
ynam
ic
inst
abili
ty re
sulti
ng fr
om th
e pr
essu
rizat
ion
lines
and
cab
le tr
ay
16G
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h C
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ld
Ice
Fro
st R
amps
Cov
er th
e pr
essu
rizat
ion
line
and
cabl
e tra
y su
ppor
t fitt
ings
to p
reve
nt ic
e fo
rmat
ion .
17G
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h C
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18G
lenn
Res
earc
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Fie
ld
Inte
rtan
kF
lang
e TP
S C
lose
outs
19G
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h C
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Fie
ld
Typi
cal F
light
Loa
ds o
n ET
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m A
pplic
atio
ns
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odyn
amic
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eatin
gA
erod
ynam
ic
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r
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ogen
ic
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pera
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F)Su
bstra
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lexu
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Mem
bran
e Fo
rces
Tank
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lFo
am In
sula
tion
20G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Aer
odyn
amic
Hea
ting
Tank
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l
Virg
in S
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m
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t Aff
ecte
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har L
ayer
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ated
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eria
l
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-423
o F
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o F
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pera
ture
s
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cted
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m T
empe
ratu
re P
rofil
e
21G
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Res
earc
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Fie
ld
Figu
re 3
.5 –
Cel
l Geo
met
ry, N
CFI
24-1
24
•97%
air;
R=0
.03
•pol
ymer
ic c
ell w
alls
•due
to it
s mic
rost
ruct
ure,
mat
eria
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niso
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osse
ss
diff
eren
t mat
eria
l pro
perti
es in
diff
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t dire
ctio
ns)
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rost
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ure
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llel-t
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e di
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ion
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endi
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-ris
e di
rect
ion
22G
lenn
Res
earc
h C
ente
r at L
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Fie
ld
Loca
l Mat
eria
l Dire
ctio
ns a
nd K
nitli
nes
Kni
t Lin
e D
ista
nce
Kni
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esR
ise
Dire
ctio
n
L 1 Ris
eD
irect
ion
Kni
t Lin
e C
ells
Kni
t Lin
e
L 3
23G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
CT
Imag
e of
PA
L R
amp
Kni
tline
dire
ctio
n an
d lo
cal m
ater
ial d
irect
ions
vary
with
pos
ition
with
in th
e fo
am a
pplic
atio
ns
24G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Type
s of
Sig
nific
ant F
oam
Def
ects
Voi
d•R
isin
g fo
am g
row
s tog
ethe
r and
seal
s in
a v
oid.
Mor
e eq
uiax
edsh
ape
than
a ro
llove
r.
Rol
love
r•R
isin
g fo
am o
verl
aps a
ndcr
eate
s lon
g po
cket
Cra
ck•S
tres
s rel
ief f
rom
thic
k ap
plic
atio
nK
nitli
neD
elam
inat
ion
•Inc
orre
ct o
verl
ap ti
me.
•Sec
ond
pass
app
lied
too
thin
or t
oo th
ick.
25G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Foam
She
ddin
g M
echa
nism
s
26G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Aer
odyn
amic
H
eatin
gHow
Spr
ay D
efec
ts C
an L
ead
to D
ivot
ing
Spra
y de
fect
con
tain
ing
air a
t 1 a
tmpr
essu
re
As h
eat p
enet
rate
s the
foam
, pr
essu
re in
def
ect v
oid
rises
.
Poss
ibly
resu
lting
in
foam
failu
re a
nd d
ivot
.
27G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
0.00
1 se
c0.
001
sec
Popc
orni
ng
28G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
70°F
Am
bien
t Air
-315
°F
-300
°F
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AIR
Vap
or
Clou
d
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ot
AIR
AIR
-315
°F
•Int
erna
l dis
cont
inui
ties,
with
a p
ath
to th
e su
rfac
e, c
an p
ull
nitr
ogen
or
air
into
the
foam
thro
ugh
a pr
oces
s of d
ensi
ficat
ion.
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id w
arm
ing
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ng a
scen
t can
cau
se v
apor
izat
ion,
a r
apid
ris
e in
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ssur
e an
d fo
am d
ivot
s.
Cry
o-pu
mpi
ng
29G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Sub-
laye
r Cra
ckin
g, C
rack
Pro
paga
tion
and
Subs
eque
nt D
elam
inat
ion
from
Sub
stra
te
Cra
ck
Del
amin
atio
n
30G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Des
ign
and
Proc
ess
Cha
nges
to R
educ
e Pr
open
sity
an
d Se
verit
y of
Foa
m L
oss
Dur
ing
Asc
ent
31G
lenn
Res
earc
h C
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r at L
ewis
Fie
ld
Rem
ove
Foam
Ram
pA
dd H
eate
rs (t
o pr
even
t ice
form
atio
n)In
cone
lfitt
ing
(hig
her t
empe
ratu
re m
etal
fo
r ext
erna
l aer
odyn
amic
hea
ting)
Insu
late
d fit
ting
from
col
d cr
yoge
n w
ith
phen
olic
insu
lato
r
Old
Des
ign
New
Des
ign
Red
esig
ned
the
Bip
od C
lose
out a
nd F
ittin
g
32G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
•Rig
orou
s pro
cess
val
idat
ion
with
dis
sect
ions
•Tig
hten
ed sp
ray
para
met
ers:
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pera
ture
•Rel
ativ
e hu
mid
ity•T
ime
betw
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subs
eque
nt sp
ray
pass
es•T
wo
oper
ator
s for
all
spra
ys (“
seco
nd se
t of
eyes
”)•W
itnes
s pan
els a
nd h
igh-
fidel
ity m
ocku
ps•V
ideo
revi
ews
Impr
oved
Spr
ay T
echn
ique
s (T
ight
er S
pecs
) to
min
imiz
e oc
curr
ence
and
sev
erity
of f
oam
def
ects
and
voi
ds.
Red
esig
ned
Bip
od C
lose
out
Moc
kup
Spra
y in
Pro
gres
s
33G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Rem
oved
the
LOx
and
LH2
PAL
ram
ps
34G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Spac
e Sh
uttle
Flig
ht S
afet
y C
ertif
icat
ion
isB
ased
on…
1)El
imin
atin
g o
r miti
gatin
g cr
itica
l sou
rces
of d
ebris
by
desi
gn•
Bip
od re
desi
gn•
PAL
ram
p el
imin
atio
n•
LH2
flang
e re
desi
gn2)
Und
erst
andi
ng th
e m
axim
um e
xpec
ted
size
and
tran
spor
t m
echa
nism
for r
emai
ning
deb
ris th
at is
gen
erat
ed.
3) U
nder
stan
ding
the
impa
ct to
lera
nce
for a
ny d
ebris
that
can
st
ill b
e ge
nera
ted
and
can
reac
h th
e sh
uttle
.4)
Con
tinge
ncy
plan
s•
Impa
ct d
etec
tion
and
on o
rbit
insp
ectio
ns•
Safe
hav
en a
t Int
erna
tiona
l Spa
ce S
tatio
n
35G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
•im
prov
ing
stru
ctur
al a
naly
sis m
etho
ds fo
r spr
ay-o
n fo
am a
pplic
atio
ns•i
mpr
ovin
g ab
ility
to d
etec
t voi
ds/fl
aws i
n fo
am a
pplic
atio
ns•i
mpr
ovin
g un
ders
tand
ing
of c
rack
pro
paga
tion
and
frac
ture
beh
avio
r of
Ext
erna
l Tan
k fo
ams
Con
tinue
to im
prov
e th
e en
gine
erin
g in
fras
truc
ture
to e
nsur
e sa
fe
and
relia
ble
foam
app
licat
ions
by…
….
36G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Impr
ovin
g St
ruct
ural
Ana
lysi
s Met
hods
for F
oam
App
licat
ions
•Acc
urat
e re
pres
enta
tion
of th
erm
o-st
ruct
ural
resp
onse
ove
r wid
e te
mpe
ratu
rera
nge:
cry
ogen
ic h
ydro
gen
(-42
3 o F
) to
500
o F.
•Acc
ount
for t
he c
ellu
lar n
atur
e of
the
mat
eria
l.•A
ccou
nt fo
r int
erna
l cel
l gas
pre
ssur
es a
nd th
eir e
ffec
t on
stru
ctur
al re
spon
se.
•Acc
ount
for o
rthot
ropi
c m
ater
ial b
ehav
ior a
nd a
rbitr
ary
orie
ntat
ion
of th
ekn
itlin
esw
.r.t.
glob
al c
oord
inat
es.
•Met
hod
shou
ld b
e em
bedd
ed in
a fi
nite
ele
men
t ana
lysi
s to
be c
apab
le o
f m
odel
ing
the
com
plex
geo
met
ries o
f the
var
ious
foam
app
licat
ions
.
37G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Impr
ovin
g ab
ility
to d
etec
t voi
ds/fl
aws i
n fo
am a
pplic
atio
ns•N
on-d
estru
ctiv
e ev
alua
tion
(ND
E) te
chni
ques
bei
ng d
evel
oped
for E
T fo
am•B
acks
catte
r X-r
ay•T
erah
ertz
•S
hear
ogra
phy
•Ins
pect
ion
tech
niqu
es h
ave
not y
et b
een
certi
fied,
dat
a us
ed fo
r eng
inee
ring
info
rmat
ion
only
38G
lenn
Res
earc
h C
ente
r at L
ewis
Fie
ld
Impr
ovin
g F
ract
ure
Mec
hani
cs A
naly
sis M
etho
ds fo
r Foa
m
How
val
id is
line
ar e
last
ic fr
actu
re
mec
hani
cs fo
r ET
foam
s?