Historically, many subscale and full-scale rocket motors have employed environmentally and physiologically harmful chemicals during the manufacturing process. This program examines the synergy and interdependency between environmentally acceptable materials for solid rocket motor insulation applications, bonding, corrosion inhibiting, painting, priming, and cleaning, and then implements new materials and processes in subscale motors. Tests have been conducted to eliminate or minimize hazardous chemicals used in the manufacture of modified-NASA materials test motor (MNASA) components and identify alternate materials and/or processes following NASA Operational Environmental Team (NOET) priorities. This presentation describes implementation of high pressure water refurbishment cleaning, aqueous precision cleaning using both Brulin 815 GD and Jettacin, and insulation case bonding using ozone depleting chemical (ODC) compliant primers and adhesives

Deweese, C. Darrell

Dillard, Terry W.

Hutchens, Dale E.

Keen, Jill M.

Lawson, Seth W.

Smith, Gary M.

English

NASA Technical Reports Server

/ 7lJi s3 7j
N95- 31796
IMPLEMENTATION OF ENVIRONMENTALLY COMPLIANT CLEANING AND
INSULATION BONDING FOR MNASA
Dale E. Hutchens
Jill M. Keen
Gary M. Smith
Terry W. Dillard
Thiokol Corporation
Huntsville, Alabama
C. Darrell DeWeese
Seth W. Lawson
NASA MSFC
Huntsville, Alabama
ABSTRACT
Historically, many subscale and full-scale rocket motors have employed environmentally and physiologically harmful
chemicals during the manufacturing process. This program examines the synergy and interdependency between
environmentally acceptable materials for solid rocket motor insulation applications, bonding, corrosion inhibiting,
painting, priming and cleaning; and then implements new materials and processes in subscale motors. Tests have
been conducted to eliminate or minimize hazardous chemicals used in the manufacture of Modified-NASA materials
test motor (MNASA) components and identify alternate materials and/or processed following NASA NASA
Operational Environmental Team (NOET) priorities. This presentation describes implementation of high pressure
water refurbishment cleaning, aqueous precision cleaning using both Brulin 815 GD and Jettacin and insulation
case bonding using Ozone Depleting Chemical (ODC) compliant primers and adhesives.
INTRODUCTION
Marshall Space Flight Center MNASA motors traditionally employ Ozone Depleting Compounds (ODC) and other
environmental and physiological hazards. MNASA is not a flight motor, but a static motor used for material testing
purposes. The hardware is re-used indefinitely making storage and refurbishment operations a necessity. The
motor is comprised of two main parts, the motor case and the four blast tube components (Figure 1). The forward
ramp, the first blast tube component, reduces the diameter of the case down to the diameter of the blast tube.
The forward center and aft center components add test area. The aft dome, the last blast tube component,
reduces the diameter of the blast tube down to the diameter of the nozzle. The blast tube components are used
for testing candidate case and nozzle insulation materials. The MNASA blast tube is stored with Cosmoline 1104,
Rust Veto 266 and Rust Veto 76-HF. The grease is removed by a standard vapor degreasing process employing
1,1,1-trichloroethane and followed by a grit blast. Following the grit blast the interior bonding surface is
immediately coated with appropriate primers and adhesives and the exterior is coated with a paint type primer.
The primary objective of the MNASA-RSRM #4 test was to evaluate the performance of non-asbestos insulations.
The secondary test objective was to serve as a midscale demonstration of ODC-free motor refurbishment and ODC
compliant bond system which are under development for the Redesigned Solid Rocket Motor (RSRM), but several
years from full-scale implementation. Bond system primers and adhesives were screened and downselected under
the Thiokol Non-Asbestos program in Utah. A second program for ODC Elimination in RSRM manufacture
developed both high pressure water refurbishment cleaning and aqueous precision cleaning. These two
technologies are described by Dillard and Keen, respectively, elsewhere in these procedings.
Approved for public release; distribution is unlimited.
*This work was performed under NAS8-38100 with NASA/MSFC.
499
https://ntrs.nasa.gov/search.jsp?R=19950025375 2020-06-16T06:15:08+00:00Z
BACKGROUND RESEARCH
RSRM is unique in solid rocketry in that after boosting the Space Shuttle Orbiter, they are recovered, refurbished
and reused. Like MNASA refurbishment, RSRM refurbishment cleaning must remove paint, insulation, adhesives
and preservative grease. Traditionally such refurbishment cleaning is by vapor degreasing and grit blasting. Water
blast refurbishment testing in support of the RSRM program is currently underway. Preliminary results guided the
selection of test parameters.
After refurbishment cleaning, both RSRM and MNASA are precision cleaned prior to bonding by again vapor
degreasing and grit blasting. The RSRM ODC Elimination program performed preliminary screening on over 150
different cleaners and selected 15 promising cleaners to carry into formal testing. Five cleaners from each of three
categories, organic, semi-aqueous and aqueous, were tested. The candidate cleaners were compared with respect
to cleaning efficiency and bond integrity; the two leading candidates, Brulin 815 GD and Diversey Jettacin, were
carried into this MNASA testing and demonstration.
A hand cleaner was also necessary to facilitate re-cleaning operations that sometimes become necessary during
hardware processing. PF-Degreaser was selected for testing as a hand cleaner in the MNASA program. PF
Degreaser, a mixture of aliphatic petroleum distillates and d-Limonene, has been successfully employed as a hand
and immersion cleaner in manufacturing programs at Thiokol's Huntsville Division for several years.
TESTING
Lab Testing
Prior to manufacturing RSRM-MNASA #4, all proposed cleaning and bonding materials and processes were tested
in laboratory adhesion testing. Witness panels (8" by 12") were prepared using a double vapor degrease, double
grit blast method that has become the standard for all Thiokol ODC testing. The purpose of this preparation is to
erase any "memory" of any chemicals the panels may have been in contact with and return the metal surface to
a pure condition. Panels were then contaminated with the preservatives used on the MNASA hardware, Cosmoline
1104, Rust Veto 76-HF, and Rust Veto 266. Panels then were divided as to what process of cleaning they would
undergo. All panels were black light inepectedand tested for non-volatile residue (NVR}. Panels involved in
aqueous processes were evaluated using water break free tests as well.
R_;RM-MNASA #4 Testing
After successful completion of the lab testing, the various blast tube components of RSRM-MNASA #4 were
cleaned and bonded according to the scheme in Table 1. The aft dome was a baseline control for this test. All
standard, previously employed procedures and materials were used in the aft dome. Because the two center
components are identical in configuration, they were used to demonstrate aqueous spray cleaning using Jettacin
in the forward center and Brulin 815 GD in the aft center. Both components received a post clean grit blast. The
ODC compliant bond system of Chemloke205/Chemloke236X was used in both center components on the blast
tube hardware with Chemloke236X being used at the insulation to insulation bond lines. The forward ramp
received a water blast followed by a vapor degrease and grit blast. The forward ramp represented the first stage
of ODC implementation currently planned for RSRM flight hardware. The aqueous bond system,
Chamloke8051Chemloke828, was applied to the forward ramp. Because actual hardware cannot undergo the
destructive bond testing before firing, 8" by 12= steel witness panels have been traditionally processed along side
the hardware for testing purposes. Water blast and precision spray cleaning parameters observed during the full
scale demonstration are listed in Tables 2 and 3.
Approved for public release; distribution is unlimited.
"This work was performed under NAS8-38100 with NASA/MSFC.
500
TABLE 1 :
MATERIALS TEST SCHEME FOR RSBM MNASA #4
REFURBISHMENT
CLEANING
FORWARD RAMP WB
FORWARD CENTER WB
AFT CENTER WB
AFT DOME VD/GB
PRECISION
CLEANING
VD/GB
Jettacin/GB
Brulin/GB
VD/GB
Leaend
WB = Waterblast
VD = Vapor Degreaser
GB = Grit Blast
CL805 = CHEMLOK 805 (Aqueous)
CL828 -- CHEMOK 828 (Aqueous)
CL205 = CHEMLOK 205 (Organic Solvent)
CL236A = CHEMLOK 236A (Organic Solvent)
CL236X = CHEMLOK 236A (ODC Compliant Organic Solvent)
PRIMER AND
ADHESIVE
CL805/828
CL205/CL236X
CL205/CL236X
CL205/CL236A
Table 2
High Pressure Water Blast
Parameter Setting
Nozzle Hammelmen Rotorjet
Nozzle angle 80 °
Stand off 8"
Pressure 33 ksi
Pass Rate 2"/sec/3.5" wide path
Flow Rate 10 gpm
Barochem rinse 1000 psi
Dry air pressure 70 - 80 psi
Table 3
Precision Spray Cleaning
Parameter Setting
Nozzle 2504
# of cleaner passes 3
Stand off 8 - 10"
Cleaner spray pressure 1000:1:20 psi
Pass rate 4"/sec/8" wide path
Cleaner temperature 150 + 5OF
Rinse pressure 70 ± 10 psi
Dry air pressure 70 - 80 psi
501
RESULTS
NVR results of all refurbishment methods were in the same family and below 2 mg/ft =, which is excellent. Figures
2 and 3 summarize the adhesion results for the lab tests, as well as witness panels accompanying the motor. In
all cases, bond strength, reported as tensile adhesion and peel strength, of the ODC compliant primer/adhesive
systems was roughly the same as the baseline primer/adhesive system (Chemloke205/Chemloke236A). All peel
strengths more than an order of magnitude above the program requirement of 12 pli and more then three times
the program adhesion strength requirement of 100 psi. The primary failure mode in all cases was cohesive within
the rubber insulation. Some significant discoveries were that in this case, water blast followed by a grit blast
produced excellent NVR results, exceptional bond results and immediately following the high pressure water blast,
all panels passed water break free tests.
Figure 4 summarizes testing of the ODC compliant adhesives as insulation ply-to-ply adhesives. As with insulation-
to-steel adhesion above, both candidate ODC compliant systems (Chemlok 205/Chemlok 236X and Chemlok
8051Chemlok 828) performed well. All adhesives performed about equivalently and significantly above the
minimum for MNASA.
CONCLUSIONS
The program objectives were accomplished. An ODC free refurbishment process (high pressure water blast
followed by precision spray cleaning and grit blast) was defined for MNASA that met and significantly exceeded
program requirements. In addition, ODC compliant primers and adhesives were identified for the MNASA-RSRM
#4 bond lines that met and significantly exceeded program requirements. These results help ensure a future
atmosphere of acceptance for these and other ODC free processes.
Not surprisingly, a certain body of unanticipated results fall into the category of "Lessons Learned." This project
is no exception:
• Since water evaporates more slowly than organic solvents with low vapor pressure, the aqueous
adhesives were more prone to run and drip when applied as thick as conventional products. Therefore,
operators should practice with new materials to learn to control them.
• Since the waterblast conditions are so harsh, protective maskants are easily torn, allowing the
adhesive to recontaminate the hardware. Therefore, protective maskants should be avioded prior to
waterblasting.
• Rust inhibitors should either be in the waterblast water, or constantly flowing over the part to be most
effective.
• Water stands on all horizontal surfaces, where possible these should be shimmed unevenly to
encourage drainage.
• Medium pressure missile grade dry air facilitates drying faster than a hot gun.
• While organic vapor masks are probably appropriate for all spray cleaning applications, operators find
solutions such as Jettacin, which contain an organic solvent, more objectional.
ACKNOWLEDGEMENTS
This paper is the result of a collaboration of many individuals. The following people provided assistance and
information: T.N. Thornton, J.R. Newton, K.B. Evans, J. Stevens and K.J. Schulte.
502
InSutatton Test
Section
-'t
i _',', j
' ,/_ Noz.zte
(_J'_ -,--- Af: coma
_.------ aft Center
I_ For.,var_ C_ntar
For_arcl Rim=
5,00O-lb Carlnc_ge Nenaseesto$ Liner
5,000-lb Cartrtage Case Segment
t/11 I 1 i /"1 / / /f
Inert Propellant
Prol=ellant Inhibitor
Figure I. MNASA Motor Test Configuration (Vertical-fired Motor with Nozzle Up)
503
.j r_" I.I.
N
Q)
iw
1.1=
I.U
U=
I
__ -
o 8
u.
mmm
mm
k.-
! : i ]
0 0 0 0 0 0 0
ISd 'sseJ_s el!sUe.l.
0
uP
O'
0
e_
X
X
o0
o
_=_
0
I£)
504
E
E :_
"E l_ n-
D •
tj
0')
ml
u_
1
<
0
(1) A
U. o
0 "5
0 o
i1
1
_ v
0,.
0 o
cN
t'N
D 4'
o
0
o _ o
I'ld 'q_,BuBJ1$ IBed
o o
0
<_
<_
X
co
c_ 0
o
LL
E0o
CN
_r_ O0
i'_ tO
ILL
0
cO
505
o
E _ E
._ < <
Q)
i._
0)
im
U.
c_
m
•_ re
F-<
mm
_Z
m
m
m
506
<1 • II
<
' L
E
._E
.c_
.., (D
z _o0
x
_D
p_
_ Z _
_ _ _J
I
(D
_ 0
ISd 'qlBueJl9 el!suez
0 0 0 0 0 0 0 0
0 tO 0 t._ 0 t._ 0 t_e)
CLEANING VERIFICATIONmINSTRUMENTATION
AND TECHNIQUES 1
507



Implementation of environmentally compliant cleaning and insulation bonding for MNASA

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server