The National Space Development Agency of Japan (NASDA) is planning to perform an 'Element Material Exposure Experiment' using the Exposed Facility Flyer Unit (EFFU). This paper presents an initial design of experiments proposed for this project by our company. The EFFU is installed on the Space Flyer Unit (SFU) as a partial model of the Space Station JEM exposed facility. The SFU is scheduled to be launched by H-2 rocket in January or February of 1994, then various tests will be performed for three months, on orbit of 500 km altitude, and it will be retrieved by the U.S. Space Shuttle and returned to the ground. The mission sequence is shown

Hashimoto, Yoshihiro

Ishii, Masahiro

Ito, Masaaki

English

NASA Technical Reports Server

N93-I2783
ELEMENT MATERIAL EXPOSURE EXPERIMENT BY EFFU
Yoshihiro Hashimoto, Masaaki Ito and Masahiro Ishii
Ishikawajima-Harima Heavy Industries Co., Ltd. (IHI)
Tokyo, 190-12, JAPAN
INTRODUCTION
The National Space Development Agency of Japan (NASDA) is plan-
ning to perform an "Element Material Exposure Experiment" using
the Exposed Facility Flyer Unit (EFFU).
This paper presents an initial design of experiments proposed
for this project by our company. The EFFU is installed on the
Space Flyer Unit (SFU) as a partial model of the Space Station
JEM exposed facility. The SFU is scheduled to be launched by
H-II rocket in January or February of 1994, then various tests
will be performed for three months, on orbit of 500 km altitude,
and it will be retrieved by the U.S. Space Shuttle and returned
to the ground. The mission sequence is shown in Figure i.
_3) Mission orbit phase [¢_) O_blt moinlenonce phase ]
llor lhree months I
Mission c.'bit lallitude 482km) __-_
"_'S '.'> --_-- initiaIizingphase, poddledeploy k\_ il.......
Hr_-_-=][Ml_hedoled1994_,_°t_
l_._IJlf,omTooego_h,mo
_l_'_l_JSpaceCeole,l
Payload Op_atlon Center /_.Transfe, to Jopon
[onding at Ken nedy
Space Center
Figure I. Flight operation profile of SFU.
283
https://ntrs.nasa.gov/search.jsp?R=19930003595 2020-03-17T10:34:21+00:00Z
PURPOSE AND MERIT OF THE EXPERIMENT
Two main purposes of the experiments are as follows:
a. Confirmation of strength of element materials to be used
in Japanese Experiment Module (JEM) of the Space Station
Freedom against AO and/or UV in LEO.
b. Research and Development for future projects.
In the LEO environment, the major factors contributing to the
degradation of materials are AO and UV. In some cases, those
synergistic effects must be more important.
SFU's basic attitude is "Solar pointing" (see Figure 2(a)). In
this attitude, one Surface faces the sun at all times and receives
abundant irradiation of ultraviolet rays. To the others, no
direct solar irradiation is given. As for AO irradiation, the
plural panels receive atomic oxygen flux in the same manner (in
sine curve). By using this advantage, three different irradi-
ations are being applied; for example, AO, UV, and AO+UV.
Ioi S.rU
|;rlJ
(a). Solar pointing mode (Basic attitude). (b). Location of installation.
Figure 2. Installation and the flight.
284
FIVE MAIN EXPERIMENTS
Five main experiments proposed by IHI are shown in Table I.
Thermal control coatings and films are our concern because they
are often used as the materials exposed to space and measurements
of LEO component degradation urgently required. They include
anodized, indium-tin-oxide and silicon-dioxide coatings and Teflons.
Three themes are proposed for them (Themes i, 2 and 4).
The only active monitoring performed by the exposure experi-
ments at this time is temperature monitoring; this is done by one
thermistor placed at the center of the sample panel prepared for
this experiment. We have planned unique environment monitoring
equipment to find out both the AO and UV flux (Theme 5).
As a research and development theme, "Comparison of damage among
different direction arrangements of graphite crystals" is pro-
jected (Theme 3).
Purpose and background for each experiment theme are described
in detail later.
Table I. Five Main Experiments
i .
,
3.
.
,
Comparison of durability characteristics among different
anodizing processes.
Growth of erosion from coating defects.
Comparison of damage among different direction
arrangements of graphite crystals.
Effects of UV, AO and their synergism on different types
of fluorocarbon.
SFU orbit environment monitoring by Kapton.
285
COMPARISON OF DURABILITY CHARACTERISTICS
AMONG DIFFERENT ANODIZING PROCESSES
The Purpose of this experiment is to evaluate the strength of
different anodized coatings under the LEO environment. The
objects are coated with chromic, sulphuric and oxalic acid.
Aluminum anodizing is known to be stable against AO attack. There-
fore, anodized aluminum foil used as the outer cover of multi-
layered insulation can be very effective for long-life spacecrafts.
Different anodizing processes produce different surface opti-
cal properties. We expect that there also exists some differ-
ences of durability against AO/UV among those three types of
coating.
Each type of coating has these characteristics as follows:
i. Chromic acid anodizing can give various a/6 by changing volt-
age and processing time (See Figure 3(a)).
2. Sulphuric acid anodizing provides low _ adaptable as a
radiator of spacecrafts.
3. Oxalic acid anodizing is said to be unaffected by UV and
solar absorptance (_) is rather stable.
1.0
Fixed:
Temperature 30_Voltage 38VDC
(100VDC)
0.51 _GS/CH<I. 05
. I I
0.5 1.0
_H
(a). Thermal optical properties obtained by
various anodizing processes(Chromic acid).
1.0
._--------------O-
f/
[ I
0 I0 20
Coating thickness
(b). Relation between c_! and anodizing
thickness (Su]phuric acid).
Figure 3. Thermal optical properties of anodized coating.
286
GROWTH OFEROSIONFROM COATING DEFECTS
The purpose of this experiment is to evaluate the growth of ero-
sion which will start from the coating defects under LEO.
Indium-Tin-Oxide (ITO) or Silicon-dioxide (Si02) coated poly-
meric materials are known to be unaffected by atomic oxygen and
can be applicable to JEM. Since ITO or SiO2 is essentially brit-
tle, however, some defects (like micro cracks) can be a start-
ing point of erosion that cannot be avoided. Pin-holes by micro-
meteoroids or debris, or perforations as air discharges, can also
act in the same manner.
By knowing the quantity of the development of defects and why
they are caused, these coatings can be applicable occasionally
to JEM or Space Station Freedom-- that is, for example, in lim-
itation of duration of usage or in application suffering fewer
AO/UV fluxes.
Three types of defects introduced in this experiment are shown
in Figure 4, along with their sources.
(i) Microcracks 5 cycles'bending of 180 against
1.6 mm diameter mandrel.
(2) Air holes
(3) Pin holes
5_ycl_s
z/._¢#._-
o
,° o,p o
microcracks
Perforation should precede
coating
Air discharging hole
Pinholing is preceded by coating
Pinhole
Figure 4. Making of "defects".
287
COMPARISON OF DAMAGE AMONG
DIFFERENT DIRECTION ARRANGEMENTS
OF GRAPHITE CRYSTALS
The purpose of this experiment is to compare damages among dif-
ferent direction arrangements of graphite crystals in carbon fibers.
In the process of calcining carbon fibers, temperature influ-
ences the direction arrangements of carbon graphite crystals. The
highly developed and closed-packed structure of hexagon is very
stable chemically. This means there can be some differences of
durability in LEO among graphite crystals which have different
direction arrangements. In this experiment, two different
direction arrangements of graphite crystals, such as radial and
quasi-onion, are to be exposed to space (see Figure 5).
In evaluation of damage of post-retrieval samples, these meth-
ods as written below, will be used.
(I) Evaluate the reaction rate by means of measuring "mass loss".
(2) Observe the differences in erosion by inspecting the sur-
face and/or section by SEM or TEM.
(3) Investigate the change of the crystal size and of the
direction arrangements by means of x-ray diffraction.
Radial Onion
Random Quasi-onion
Figure 5. Coal-pitch carbon fibers (processed at 2500°C).
288
EFFECTS OF UV, AO AND THEIR SYNERGISM
ON DIFFERENT TYPES OF FLUOROCARBON
The purpose of this experiment is to evaluate the effects of
UV, AO and their synergism on Teflon films (i.e. FEP, TFE and ETFE)
that have different chemical compositions.
FEP, TFE and ETFE are fluorocarbons (Teflon) which have respec-
tive chemical compositions (See Table II).
Teflon is well known for its anti-UV characteristics and this
can easily be confirmed in the ground simulation testing.
Regarding anti-AO characteristics, Teflon has been said to be
strong because of space shuttle experiments and many ground test-
ings, but the Teflon samples retrieved from SMRM are damaged, dif-
fering from the preceding results. In SMRM, synergism of AO and
UV was investigated only qualitatively (ref. i). Teflon used in
this experiment was not pure fluorocarbon "TFE", but a copoly-
mer of -CH2- and -CF2- (they are equivalent to ETFE). On the other
hand TFEs are composed only of strong -CF2- bondings and have no
weak -CH2- bonding. At this point TFEs can be expected to be sta-
ble satisfactorily in the LEO environment.
Table II. Chemical Composition of Teflons
Name
Cl_m[c_tl
Composition
PTFE
Polylet ra fhJoroethylene
I
-;;jo
PFA
Pelfl_r_Iko_y
11
FFFFFF
t11111
--C--C--C--C--C--C--
llllll
FFFOFF
I
RI
FEI )
Fluorinated Ethylene
Propylene
I_TFE
£_thylene TetrafluorOelhylene
F F
t I
--C--C--
I I
F F
t,, [H.--C--C-- --C--C--C-- --i I I
x F F n H H F F Jlrl
Reference
1. R. H. Liang, K. L. Oda, S. Y. Chung and A. Gupta: 18th Inter-
national SAMPE Technical Conference, Oct. 7-9, 1986.
289
SFUORBITENVIRONMENT MONITORING BY KAPTON
The purpose of this experiment is to acquire transient vari-
ation of irradiation fluence of AO in the flight orbit of SFU.
Parilene (Poliparaxylene) coated Kapton specimens are used. This
coating is vapor deposited and processed to one side. Parilene
can easily be controlled through its coating thickness--almost
to the accuracy of 0.i _m. Being exposed to space, the Parilene
layer of the sample is eroded at first by AO; the Kapton layer
of the base appears in some months.
By preparing Parilene layer specimens of different thicknesses,
we can precisely control the period of exposure time of Kapton
(See Figure 6).
After the retrieval, examining the quantity of the surface ero-
sion, (loss of thickness): At[cm], we can get such plotting as
shown in Figure 7(a). Linearity of the erosion of Kapton with
AO fluence is already confirmed in the LDEF experiment, so we first
confirm this linearity again and then finally get the AO fluence
characteristics shown in Figure 7(b).
llllllllll
9??
?9?
Thickness 0_m 0.4_m 0.S#m 1 2#m 2.4_m
of Parilene --_
Exposed time
of Kapton to--_6months 5months 4months 3months 0month
the space
Figure 6. Mechanism of environment monitor.
AQ _luence
(a) Erosion vs. period.
F
t ,L,apse o_ t_.me afte_ launch t
(b) AO fluence vs. elapsed time.
Figure 7. Expected plottings.
29O
EXPECTED RESULTS AND SCHEDULE
Expected results brought from the experiment are summed up as
follows:
i. After estimating declination quantity of each material dur-
ing 10 years in LEO, we can confirm adaptability of those
materials to JEM.
2. Confirmation and investigation can be achieved about the
validity of ground simulation test equipment of AO
irradiation.*
3. Base data for future development of space materials can be
obtained (reaction data, etc.).
Schedule of this experiment is shown in Figure 8. Ground test-
ing beforehand is very important because the number of the flight
samples is limited. To reflect the results of this experiment
in JEM's design, the schedule is very tight. JEM's system fab-
rication is to start in 1995.
The authors wish to express their sincerest appreciation to the
session chairmen, workshop coordinators and the LDEF Chief Sci-
entist for getting the chance to present this paper. To do this
experiment successfully, advice, comments, and questions are very
helpful and almost indispensable.
FY199 FY1992 FY1993 FY1994 FY1995
_JTl__345S_8910Zl_-6TaglOlH2!_S678 10tl1212 4ssTSglonj2] 2
Milestone , • : : . ::, • : : . i.. "
" ! i 0 ;:'' ' .... - --• SFU--1 P_ " T_t , i . ' " i _ , . . :
• EFVU _ _ _t Rot_i_ ....
_lgn - . .... :
• Sample fitting F_rt_li_ " : ' I [ " " " : :
panel _'_t : : , , - .
...... ' .... r--
:1 _! _i iii: :¢ : :
Ex_rls_t. .....
- _ t_ • : '
Design Pla_lng Pia_i,l£ _tgnofflig_t _terials : E_lu; Ion _al)_ls
i • 7
: Pre_rl_ " _ : _@pb9 ....
TeSt Specimen " i "'_ .... t_rL=tl=flst'V ....
ZPe¢_ .... _ • : .... _ :
• -:"i. :i1-!!i77:i:1:7i-77--:, - :
" T_t .......
Ground Test : : ' _ _ # " ' ! i i
] i
Figure 8. Schedule of the experiment
*IHI has developed its own equipment.
291
J


Element Material Exposure Experiment by EFFU

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