Substrates to be contaminated and contamination source were prepared. Additional information on paint spray method apparatus was obtained. Silver teflon second surface mirror samples and S 13 GLO paint samples were mounted, photographed under the microscope and measured to establish baseline data. Atomic oxygen cleaning and spray painting are being considered. Electrostatic powder and plasma spray coating systems appear to have serious drawbacks

Racette, G. W.

English

NASA Technical Reports Server

ON ORBIT SURFACING
•OF THERMAL CONTROL SURFACES
CPMTRACT NO. NAS8 - 35342
MONTHLY PROGRESS REPORT #7
MAY, 1984
.PREPARED FOR
GEORGE C. MARSHALL SPACE. FLIGHT CENTER
MARSHALL SPACE FLIGHT CENTER
'ALABAMA 35812
SUBMITTED BY
'GENERAL ELECTRIC COMPANY
•SPACE DIVISION
VALLEY FORGE SPACE CENTER
•P. 0. BOX 8555
PHILADELPHIA, PA. 19101
L. J. AMORE, PROGRAM MANAGER
6.. W. RACETTE, PRINCIPAL INVESTIGATOR
https://ntrs.nasa.gov/search.jsp?R=19840023196 2020-03-20T21:02:17+00:00Z
MONTHLY PROGRESS REPORT
ON ORBIT SURFACING OF THERMAL CONTROL SURFACES
A. Program Objective
The objective of this program is to support future long term space missions by
developing and testing on orbit surfacing methods for thermal control surfaces.
This program is to:
(1) Determine the performance requirements for on orbit surfacing of
thermal control and other optical surfaces.
(2} Define methods of on orbit surfacing of thermal control and optical
surfaces and select promising methods for laboratory facility studies.
[3) Perform a feasibility study of selected surfacing methods for final
selection of a particular method or methods for full development of
the process and instrumentation.
B. Work Perfromed during this period
f> o •-•-••'o
Substrates to be contaminated and contamination source were prepared. Additional
information on paint spray method apparatus was obtained. Status of.program
was reviewed on site with contractor representative.
Paint Spray Apparatus ..
Last month, a patent application for a paint spray apparatus to be used by a
free flying astronaut was briefly described. The inventors of this, device have
been contacted and additional information obtained.
•The apparatus was developed at Johnson Space Center and was originally designed
for use in repairing shuttle tiles for reentry.- Formal report on the device,
except for the patent application, was not completed because increased confidence
in shuttle tile reliability caused termination of .the program. However, astronauts
were trained to use it and testing in vacuum and also in ballistic trajectory
aircraft was performed, and. a,patent is pending and expected to be issued in the
-—^ near future. The inventors afr-e :.J. • F.' Kuninecz and M. F. Lausten.
Although it has not actually been used in orbit, the device was designed so the
astronaut could use it either attached or unattached to the vehicle being sprayed.
• Patent application sketch and description is in appendex A.
Capacity of the gun is about 0.5 liter. It' took 4 guns to cover 25 square feet.
This is about 50 ft^/gallon. This is substantially below the standard paint
spray efficiency. The low efficiency was apparently partly the result of the
rough surface being-sprayed and partly.becuase additional carrier was required
for the vacuum application.
-2-
However, it is estimated that the evaporation rate effect cause only a doubling
of the carrier needed in air. Thus a smooth surface would result in a higher
coverage efficiency.
The paint used in the shuttle application was basically silicon carbide in
alcohol carrier plus a dispersant to prevent the silicon carbide from sticking
together in globs as a result of storage. Only 1 to 2% binder was used because '-•-•
the material stuck quite well to the rough surface being sprayed.
An open urethane foam acted as spray shield and filter. There was some difficulty
with this because the shield was designed to conform to typical spacecraft shapes
but the urethane foam loses flexibility when cold. It tends to become cold in
operation because of evaporation cooling by the carrier. It becomes brittle and
is subject to breaking. One of the inventors (O.K.) indicates he would solve
this polyimide foam in any future model.
There was no difficulty with the nozzle or filter clogging during operation,
though there would be after a number of uses. Leaks in the various passages
did cause clogging because of evaporation of carrier near the leak. Careful
production and assembly is needed. The inventors are not aware of any other
similar effort.
Experimental
S 13 GLO paint samples and silver teflon second surface mirror samples have been
mounted, photographed under microscope and the^v
 s measured to establish base-
line data on particular samples to be contaminated and then cleaned. Also a
contamination source oven with urethane contaminant has been prepared. These
will be used for cleaning studies after compeltion of vacuum system improvements
being accomplished without contract support. Additional TQCM measurements pre-
viously referred to will also be accomplished at that time.
Last month it was also mentioned that removal of acryllic adhesive residue after
removal of thermal control tapes per strip/replace renewal method would be
difficult. This was confirmed by a short test which showed that, in the lab, it
took several minutes to clean off a residue spot about one inch square using
either isopropyl alcohol or acetone. Additionally it is difficult to keep the
adhesive of the removal tool which redeposits it. It must be noted that it may
not be necessary to remove the residue.
Contractor Review
Roger Linton of MSFC visited Valley Forge for on site review of the program to
date and discussion of future work. The advantages and disadvantages of various
systems of cleaning as identified to date were reviewed. The atomic oxygen dis-
charge source and photo dissociation source which have been used were described
and examined.
It was noted that consideration of atomic oxygen cleaning and spray painting
refurbishment is encouraging. Electrostatic powder and plasma spray coating
systems appear to have serious drawbacks. Other systems, such as sputtering,
heat or laser cleaning, strippable/replaceable coatings and abrasive cleaning
have some disadvantages but require more study. Future direction and the
goal of proceeding to more developed systems were also reviewed.
-3-
C. Plans For Next Period
During the next month, study of the various cleaning processes will continue.
Atomic oxygen cleaning experiments will be resumed upon completion of G.E.
funded vacuum system improvements.
D. Performance, program schedule and/or cost are not being impeded by any
current problems. . •
E. Cumulative costs as of May 20 are $29,728. Estimate of physical completion
of contract is 52%. Physical completion is on schedule relative to
comulative costs.
A P P E N D I X A
PATENT APPLICATION
DESCRIPTION OF
.SPRAY GUN FOR SPACE
USE
CM S C - 18852 Ser.# 392,094)
(JUNE 25, 1982)
DESCRIPtlON OF THE DRAWINGS
20 Fig. 1 illustrates a cross-sectional view of the invention.
Fig. 2"shows a detailed cross-sectional view of the trigger activated value
• of the. invention. ..
DETAILED DESCRIPTION OF THE INVENTION
Referring now to Fig. 1, the mumeral 11 generally indicates the self-contained
25 spray applicator as herein described. The spray applicator 11 includes a accumulator
12, a spray gun 13, and a spray shield 14. Turning now to the accumularor 12, the
major components thereof include a rigid outer shell or canister 15, which contains
30 inner flexible bladder 16 and a head 26. The liquid coating material 17 is contained
within the bladder 16. A pressurized propellent 18 may be injected into the outer shell
12 so as to apply a constructive force on the bladder 16, thereby inducing the liquid
35 coating.material 17 to exit the bladder through an outlet passageway 19 located in head
26 at one end of the outer shell and bladder. The pressurized propel!ant may be injected
into the rigid outer shell through an adapter assembly 20 threaded within the accumulator
at the end opposite the outlet passageway 19. The adapter assembly -20 inches a valve
21 for controlled injection of the propellant, a conventional 0-ring 22 annuarly mounted
5 with respect to the adapter assembly so as to rpovide an effective seal with respect to
the pressurized propellant contained within the accumulator, and a removable adapter
10 plug 23 threaded above the exposed'end of the valve 21 and an additional 0-ring 24.
The accumulator 12 will further include one or more weighted balls 25, the motion
which within the bladder assure agitation and uniform distribution of the liquid coating .
15 material 17 contained therein, which may tend to stratify and.separate during prolonged
periods of storage and inactivity. Further, head 26 includes a plurality of orifices
2 7 of sufficient diameter and location so as to. assure uninterrupted flow of the liquid
20 coating material 17 despite any interference from the mixing balls or coagulated material
of any individual orifice. The accumulator 12 will further include a suitable insulation
layer 28, whereby the contents thereof are protected from the temperature conditions
' in the ambient environment during operation of the spray applicator, and in addition
25 the temperature thereof may be controlled during periods of storage prior to use. This
insulation layer 2.8 is applied in a nearly continuous envelope of material over the outer
surface of the outer shell 15.
The escaping coating material 17 is channeled through a passageway 19 in value
30 .assembly 31 connecting the accumulating 12 and the spray gun assembly 13. A shut off.
plug assembly 30 and external handle 32 in valve assembly 31 may be manually placed in
an open position during periods of extended operation and conversely placed in a closed
35 position during periods of inactivity, so as to effectively reduce the possibility of
seepage or leakage of the liquid .
-5-
coating material under pressure during storage. Further,
the valve assembly 31 will include a removable filter 34,
whereby unacceptably large droplets or coagulated masses
of coating material are prevented from entering the spray
5 gun assembly. The filter 34 is accessible from the outside
through an opening 37 in the valve assembly 31. The opening
37 is sealed by a hex plug 35 and a conventional 0-ring 36,
both of which may be removed for extraction and cleaning of
the filter 34 as necessary.
10 ' As previously mentioned, the 'valve assembly 31 connects
the accumulator 12 to the spray gun 13. The spray gun 13
includes'handle 39. .A handle, support assembly 41 connects
the handle 39 to the accumulator 12 to provide support and.
strength to the overall assembly. The handle support .assem-
1.5 bly 41 includes a .bracket 42 fixed at one end to the handle
39 and mounted on the other end on the outer shell 15 of
the accumulator 12. The bracket 42 is mounted in encircling
engagement with the outer shell 15 through the use of a hose
clamp 43. The shell 15 is insulated from bracket 42 and
20 hose clamp 43 by means of a felt 45. The handle support
assembly 41 will further include a tether ring 46, whereby
a convenient means is provided to secure the spray applicator
to the space craft or the operator.
The spray gun 13. further includes a trigger means 47,
25 which in the preferred embodiment of. the invention includes'
a lever 48 pivotally mounted to the spray gun handle 39 at
one end thereof and in a closed position is substantially
parallel to the handle 39, and when the lever 43 is rotated
manually towards the handle. 39, it assumes an open position.
30 The significance of the open and closed positions of the
.lever 4-8 'will be explained more fully at a later time.. A
. self-locking trigger Lock'49 is further provided to prevent
inadvertent operation of the spray applicator. A- lock
spindle 50 is mounted in the spray gun handle 39. A lock
35' spring 52 is concentrically mounted 'on the lock spindle 50 .
• -so as to prevent the lock 49 from rotating into an indentation
-6-
79 in the body of the trigger lever 48. .However, the lock,
spiring 52 exerts a 'torsional force on the asymmetrical
lock 49 so as to prevent it from assuming the orientation
suitable for engagement and insertion into the identation
5 79. Thus, movement of the trigger lever 48 towards the
handle 39 and therefore into an open position, is prevented
until the torsional force exerted by the trigger spring 52
is manually overcome and the lock 49 is rotated so as to
be inserted into the identation 79. Also included is a
10 spring stop 54, for a second spring 77, which is concentri-
cally arranged behind the"lock spindle 50 and may be adjust-
ably positioned inside the handle 39 and locked thereon by
means of a conventional set screws or the like 55. The
spring load for sealing valve set 65 by shut off needle 64
15 is adjusted by insertion and rotation of a hex head wrench
into stop 54 through a hole 78 to increase or decrease the
load on spring 77.
The action of the trigger means 47 actuates a valve 56
controlling the outflow of liquid coating material 17 into
20 passageway 80. Positioning the trigger means 47 in an open
position correspondingly opens the valve 56 allowing the
liquid coating material 17 to escape through a nozzle 57 to
the ambient environment in the form of a pressurized spray.
Concentrically, mounted with respect to the nozzle 57, is a
25 spray shield assembly 14, previously mentioned. The spray
shield assembly 14 is S3 constructed as to allow the vent-
ing of any associated gases fro.n the emitting spray of
liquid coating material, while simultaneously entraping co-
agulated particles deviating from the desired path of the
30 emitting spray, or bouncing back from the surface being
coated.
The spray shield assembly is comprised of an inner
shield layer 53 and an outer shield layer 59, both layers
concentrically arranged and adjacent one another. The
35 inner shield 53 and the outer shield 59 are both construc-
ted of an open cell flexible urethane foam material, with
-7-
the inner shield having a core shell structure and the
outer shield 59 having a fine cell structure. Specifically,
the inner shield will have a composition of approximately
35 pores per inch, whereas the outer shield will have a
5 composition of approximately 65 pores per inch. Thus, in
operation, the larger particles of material deviating from
the emitting spray, as well as splashback from the surface
being coated, will be entrapped by the core cell structure
of the inner shield 58 and finer particles will penetrate
10 the inner shield but will be prevented from leaving the
spray shield assembly by the fine cell structure of the
outer shield 59, while stil1.allowing the venting of gas
from the vacuum evaporated coating fluid. Attachment of
the spray shield assembly to the spray applicator will be
15 accomplished by an annular flange 60, which will be mechani-
cally attached by a screw 61.
Fig. 2 shows in detail the structure of the valve 56,
including an inlet body 62 defining passageways 53 and 50
connecting at one end the valve assembly 31 and at the
20 other end, through passageway 80, the nozzle 57. The flow
of liquid coating material 17 through the passageway 80 is
controlled through the positioning of a shut off needle 64
concentrically located along the center axis of the passage-
. way 50. The shut off needle has a first end which is conn-
25 ected to the trigger means 47, whereby when the trigger
means is in a closed position, the shut off needle is for-
cibly engaged with a plastic valve seat 65 so as to seal off
the nozzle 57 from the coating in passageway 50. When the
trigger means 47 is in an open position, the shut off needle
30 64 is retracted and no longer engages the valve seat 65 nor
obstructs the flow of liquid coating material 17 through the
passageway 80.
The shut off needle 64 is allowed to slide in and out
of the inlet body 62, yet be sealed to the passageway 50
35 so as to prevent the unwanted emittance of liquid coating
material 17, except through the nozzle 57, by a series of
-8-
sealing materials shown in Fig. 2. Concentrically arranged around the shut
off needle 64 is a shaft seal 75 which includes spring loaded Teflon.
0-ring 66 is suitably concentrically arranged with respect to the shaft
5 seal and shut off needle 64. The shut off needle 64 also has suitable
threads within the inlet body 62 so as to compress the shaft seal 75
against a packing stop 68, whereby an effective seal is maintaiaed
with respect to the inlet body 62 and passageway 50.
TO In operation, the trigger means 47 is placed in an open position,
thus retracting the shut off need le 64 from the valve seat 65 allowing
the emittance of liquid coating material 17 through the passageway 80
and the nozzle 57. The nozzle 57 includes a nozzle tip 69 designed to
15 properly atomize the coating in the cacuum environment. Nozzle 57 necks
down to an orifice 70 and then conically widens to a funnel like area
71 which shapes and guides the emitting spray of liquid coating material.
Under the conditions of zero gravity and vacuum in the ambient environment,
20 it has been observed that an orfice of .020 inches in diameter offers the
optimum control of the emitting spray when used in conjunction with a
funnel with an angular cross-section of 90°.
-9-
SPRAY APPLICATOR FOR SPRAYING COATINGS
AND -OTHER FLUIDS - IN SPACE
ABSTRACT ' . . ' ' •
The object of the invention is to provide a self-
contained spray applicator for one handed operation in a
zero gravity vacuum environment by a free-flying astronaut
5 not attached to any spacecraft while avoiding contamination
of the operator by back spray.
Said applicator includes a rigid .accumulator (12) for
•containment of a fluid (17) within a flexible bladder (16),
the fluid being, urged out of the accumulator under pressure
10 through a spray gun (13). The spray gun includes a spring
loaded lockable trigger (47) which controls a valve (56).
When in an open position, the fluid passes through the
valve into the ambient environment in the form of a spray.
A spray shield' (14.) is provided which directs the flow of
15 the spray from the applicator by trapping errant particles
of. spray yet allowing the passage of e.scaping gases through
•its material. This reduces the reactive force "exerted by
the escaping spray on the operator of the applicator. The
spray, shield consists of two concentric .layers of open
20 celled urethane foam with the inner layer consisting of a
'coarser grain than the outer, thereby trapping progressively
finer particles of spray.
59
66


On orbit surfacing of thermal control surfaces

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