NASA s activities to prepare for Flight LF1 (STS-114) included development of a method to repair the Thermal Protection System (TPS) of the Orbiter s leading edge should it be damaged during ascent by impacts from foam, ice, etc . Reinforced Carbon-Carbon (RCC) is used for the leading edge TPS. The repair material that was developed is named Non- Oxide Adhesive eXperimental (NOAX). NOAX is an uncured adhesive material that acts as an ablative repair material. NOAX completes curing during the Orbiter s descent. The Thermal Protection System (TPS) Detailed Test Objective 848 (DTO 848) performed on Flight LF1 (STS-114) characterized the working life, porosity void size in a micro-gravity environment, and the on-orbit performance of the repairs to pre-damaged samples. DTO 848 is also scheduled for Flight ULF1.1 (STS-121) for further characterization of NOAX on-orbit performance. Due to the high material outgassing rates of the NOAX material and concerns with contamination impacts to optically sensitive surfaces, ASTM E 1559 outgassing tests were performed to determine NOAX condensable outgassing rates as a function of time and temperature. Sensitive surfaces of concern include the Extravehicular Mobility Unit (EMU) visor, cameras, and other sensors in proximity to the experiment during the initial time after application. This paper discusses NOAX outgassing characteristics, how the amount of deposition on optically sensitive surfaces while the NOAX is being manipulated on the pre-damaged RCC samples was determined by analysis, and how flight rules were developed to protect those optically sensitive surfaces from excessive contamination where necessary

Campbell, Colin

Engle, Michael

Garrett, Jeff

Koontz, Steven

McCroskey, Doug

Mikatarian, Ron

Schmidl, Danny

Smith, Kendall A.

Soares, Carlos E.

NASA Technical Reports Server

  
American Institute of Aeronautics and Astronautics 
 
1
Space Shuttle Thermal Protection System Repair  
Flight Experiment Induced Contamination Impacts 
Kendall A. Smith*, Carlos E. Soares, Ron Mikatarian, Danny Schmidl  
Boeing, Houston, TX, 77059 
Colin Campbell, Steven Koontz, Michael Engle 
NASA JSC, Houston, TX, 77058 
and 
Doug McCroskey, Jeff Garrett 
Outgassing Services International, Mountain View, CA, 94043 
NASA’s activities to prepare for Flight LF1 (STS-114) included development of a method 
to repair the Thermal Protection System (TPS) of the Orbiter’s leading edge should it be 
damaged during ascent by impacts from foam, ice, etc…. Reinforced Carbon-Carbon (RCC) 
is used for the leading edge TPS. The repair material that was developed is named Non-
Oxide Adhesive eXperimental (NOAX). NOAX is an uncured adhesive material that acts as 
an ablative repair material. NOAX completes curing during the Orbiter’s descent. The 
Thermal Protection System (TPS) Detailed Test Objective 848 (DTO 848) performed on 
Flight LF1 (STS-114) characterized the working life, porosity void size in a micro-gravity 
environment, and the on-orbit performance of the repairs to pre-damaged samples. DTO 
848 is also scheduled for Flight ULF1.1 (STS-121) for further characterization of NOAX on-
orbit performance. Due to the high material outgassing rates of the NOAX material and 
concerns with contamination impacts to optically sensitive surfaces, ASTM E 1559 
outgassing tests were performed to determine NOAX condensable outgassing rates as a 
function of time and temperature. Sensitive surfaces of concern include the Extravehicular 
Mobility Unit (EMU) visor, cameras, and other sensors in proximity to the experiment 
during the initial time after application. This paper discusses NOAX outgassing 
characteristics, how the amount of deposition on optically sensitive surfaces while the NOAX 
is being manipulated on the pre-damaged RCC samples was determined by analysis, and 
how flight rules were developed to protect those optically sensitive surfaces from excessive 
contamination where necessary.  
Nomenclature 
Å = Angstrom (1Å = 10-8 cm)  
AO =  Atomic Oxygen 
CSA = Canadian Space Agency 
CMG = Control Moment Gyro 
DTO = Detailed Test Objective  
EMU = Extra-Vehicular Mobility Unit 
EVA = Extra-Vehicular Activity  
FSE = Flight Support Equipment 
HTV = Human-rated Thermal Vacuum 
ISS = International Space Station  
LMC = Lightweight MPESS Carrier 
MPESS = Multi-Purpose Experiment Support Structure 
                                                          
* Engineer/Scientist, Boeing-Houston, 13100 Space Center Blvd. HB3-20 . 
https://ntrs.nasa.gov/search.jsp?R=20080026302 2019-08-30T04:44:34+00:00Z
  
American Institute of Aeronautics and Astronautics 
 
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DTO 848
Figure 1: DTO 848 in Orbiter Payload Bay 
NASA = National Aeronautics and Space Administration 
NOAX = Non-Oxide Adhesive eXperimental 
OBSS = Orbiter Boom Sensor System  
OSI = Outgassing Services International 
PLB = Payload Bay 
QCM = Quartz Crystal Microbalance 
QTGA = QCM Thermogravimetric Analysis 
RCC = Reinforced Carbon-Carbon 
SRMS = Shuttle Remote Manipulator System  
SSRMS = Space Station Remote Manipulator System 
STS = Space Transportation System 
TPS = Thermal Protection System 
UVR =  Ultraviolet Radiation 
 
I. Introduction 
S part of NASA's preparation for Flight LF1 (STS-114), a method was developed to repair the Reinforced 
Carbon-Carbon (RCC) on the leading edge of the Orbiter should it be damaged during ascent. The Non-Oxide 
Adhesive eXperimental (NOAX) material was developed to act as a cure-in-place ablative repair material [1]. The 
Thermal Protection System (TPS) Detailed Test Objective 848 (DTO 848) was performed on Flight LF1 (STS-114). 
A total of 3 pre-damaged RCC samples were flown 
for Flight LF1. Test objectives include evaluation of 
micro-gravity impacts on the material behavior 
during application and degassing, as well as, in the 
resultant porosity of hardened repairs. Additionally, 
evaluations were made with respect to hardened 
vacuum, sinusoidal temperature profiles, and 
attributes such as protuberance, step heights, ramp 
angles, surface roughness, micro-cracking and 
material layer thickness in the Low Earth Orbit 
(LEO) environment. DTO 848 is also scheduled for 
ULF1.1 (STS-121) to further characterize NOAX on-
orbit performance. Figure 1 shows the location of the 
experiment inside the Orbiter Payload Bay. Figure 2 
shows the configuration of the RCC samples in the 
Lightweight Multi-Purpose Experiment Support 
Structure (MPESS) Carrier (LMC) which is located in the back of the Orbiter Payload bay.  
During Human-rated Thermal Vacuum (HTV) 
testing, where an astronaut performs a simulated 
repair in a large vacuum chamber, fogging of the 
Extra-vehicular Mobility Unit (EMU) visor was 
observed when dispensing NOAX onto RCC 
samples at a temperature of 49°C within a time 
period of 15 minutes. The EMU visor was estimated 
to be at a temperature of -34°C while in the HTV 
due to the presence of liquid nitrogen cooled walls 
and the lack of a solar simulator. In contrast, 
thermal conditions on-orbit are known to be more 
benign, with the EMU visor operating in a 
temperature range of -10°C to 16°C. Removal of the 
deposited material using EVA wipes during HTV 
testing was successful, however, there is a concern 
that when the contaminated visor is exposed to the on-orbit environment (Ultraviolet Radiation (UVR) and Atomic 
Oxygen  (AO)), the material may fix to the surface of the visor and be difficult to remove.  
A
Damaged RCC 
OBSS Survey 
(R285-12) 
EWA DTO:  EV 
Free Floater  
Damaged RCC 
Crack Repair 
DTO 
(R1-47 #13) 
Aft
Port
Forward
Crack Repair Material 
Porosity Sample 
 
Figure 2: LF1 Configuration of LMC with RCC samples1 
  
American Institute of Aeronautics and Astronautics 
 
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Due to the high material outgassing rates of the NOAX material and concerns about contamination sensitive 
surfaces (including the potential hazard of fogging of the EMU visor), ASTM E 1559 outgassing tests were 
performed to determine the condensable outgassing rate for NOAX as a function of time during the curing 
process[2]. During the first Flight LF1 EVA, NOAX was applied to one of three pre-damaged RCC samples. 
Another sample was used for an Orbital Boom Sensor System (OBSS) scan to evaluate the ability of the OBSS to 
detect damage on the RCC. The other samples were not used due to EVA time limitations. 
 
II. Materials Outgassing Induced Contamination 
Contaminant deposition and accumulation, in conjunction with exposure to the LEO environment (UVR and 
AO), can produce degradation of the optical properties of contamination sensitive surfaces. Characterization and 
modeling of optical property degradation is crucial to the long-term operation and performance of equipment 
sensitive to optical degradation [3,4,5]. 
ASTM E 1559 testing of ISS materials focus on outgassing rates toward the end of the six day test. Due to the 
comparatively short time period that the NOAX material will be on-orbit and the presence of sensitive surfaces, such 
as the EMU visor and OBSS optical sensors, during the first few hours of outgassing, it was critical to understand 
the initial outgassing rate behavior of the NOAX material. Additionally, this was the first known test of an uncured 
material in an ASTM E 1559 chamber. Special care had to be taken to ensure that the initial rate information could 
be accurately captured. Several samples of NOAX were supplied for ASTM E 1559 testing. A test duration of 48 
hours was selected and the source and receiver temperatures were selected to afford comparison to ground test 
conditions and predicted on-orbit conditions. A QCM Thermogravimetric Analysis (QTGA) was performed to 
determine the nature and relative abundance of the outgassed species. 
Composition analysis conducted during the QTGA indicated that the deposited material was composed primarily 
of several related complex organic or organic-silica compounds. The QTGA also confirmed the presence of a liquid 
deposit between temperatures of -53°C and -33°C. This is an indirect observation based on the behavior of the QCM 
during the QTGA, actual range where liquid is present may be broader. The QTGA also demonstrated that not all of 
the deposited material was a permanent deposit. For a 100Å layer of contaminate, approximately 20% of the 
material deposited on the -34°C QCM evaporated during a 5 hour period. For a 500Å layer, only 10% of the 
material evaporated during a 5 hour period. Following the isothermal period, the -34°C QCM was heated at a rate of 
approximately 1°C/min. After reaching a temperature of 22°C most of the deposited material had evaporated. A 
conservative estimate of the evaporation rate during the warm up is 8Å/min.  
III. Non-Oxide Adhesive eXperimental 
Behavior 
During testing in the Human-rated Thermal 
Vacuum Chamber (HTV), profuse bubbling was 
observed particularly for NOAX applied at higher 
temperatures. In addition, condensation of material 
on the EMU visor was observed. This material was 
easily removed in the HTV, but on-orbit conditions, 
particularly with exposure to AO and UVR might 
cause the material to be difficult or impossible to 
remove on-orbit.  
As can be seen in Figure 3, the first visible 
instance of fogging occurred after approximately 15 
minutes of exposure to NOAX at 49°C with the 
visor at -34°C. Since NOAX was being dispensed 
continuously, the effective amount on the test 
surface during this period was approximately 8 in2. 
Using the initial outgassing rate a deposit with an 
average thickness on the order of 30Å to 120Å, respectively, would be expected due to the NOAX for the first 
instance of fogging in the timeline shown in Figure 3. It should be noted that a deposit of this thickness would not be 
expected to significantly impact the optical properties of the visor, therefore the deposit likely coalesced into 
droplets. The visor in the HTV had also already been exposed to a significant amount of NOAX at lower 
temperatures which may have also contributed to the fogging of the visor. 
  
Figure 3: Timeline for dispensing of NOAX in HTV 
  
American Institute of Aeronautics and Astronautics 
 
4
During the on-orbit DTO, with the NOAX being at the nominal temperature of 27°C, approximately 2Å to 8Å of 
material will deposit. If the temperature of the NOAX increases to 38°C, then the amount of deposition would 
increase to between 7Å and 29Å. If the temperature of the NOAX increases to 49°C, then the amount of deposition 
would increase to between 11Å and 46Å. For the nominal case with the NOAX at 27°C, the amount of deposition is 
several orders of magnitude less than seen in the HTV and is highly unlikely to cause fogging of the visor. 
The on-orbit DTO confirmed this prediction, as no fogging of the EMU visor was observed. Also, due to the 
zero gravity environment, bubbling did not occur, instead the material swelled slightly like rising bread. A swiping 
motion was discovered to work best to remove the volatile material from the NOAX to aid in application and curing. 
Figure 4 shows the NOAX after it has been applied 
during the DTO. 
 
IV. ISS and Orbiter Sensitive Surfaces 
Outgassing contamination onto ISS optically 
sensitive surfaces is limited to 30Å/yr. ISS sensitive 
surfaces include the Lab window, and Space Station 
Remote Manipulator System (SSRMS) camera 
lenses. The SSRMS was used to observe the crew 
during the DTO and to perform operations in the 
Payload Bay which would place it in close 
proximity to the DTO including the removal of a 
replacement Control Moment Gyro (CMG) being 
delivered by the Orbiter. The hardware owner of the 
SSRMS, the Canadian Space Agency (CSA), agreed 
to allow up to 10Å of contamination on the lens for 
this DTO. The Lab window was to be open for brief 
periods of time for situational awareness. Since the 
Lab window is a science window with extreme sensitivity to deposited materials it was imperative to ensure that this 
surface receives minimal contamination. 
Deposition onto Orbiter optically sensitive surfaces is less of a concern than ISS sensitive surfaces, since it is 
possible to clean or replace these surfaces when the Orbiter returns to Earth. Sensitive surfaces on the Orbiter 
include the Shuttle Remote Manipulator System (SRMS) cameras, the Orbiter Boom Sensor System (OBSS), and 
the Orbiter Payload Bay cameras. 
Discussions with the Orbiter 
Project Office resulted in a limit 
of 100Å of contamination for the 
SRMS cameras and the Orbiter 
Payload Bay cameras to prevent 
degradation of the use of these 
instruments while on-orbit. Since 
the OBSS is a highly sensitive 
instrument designed for analyzing 
of the Orbiter TPS it is desirable 
to maintain contamination levels 
on this instrument at minimal 
levels so an acceptable 
contamination level of 10Å was 
assigned to the OBSS. Planned 
operations for the OBSS included 
a scan of a damaged tile sample 
on the LMC 3 hours after the 
DTO has been performed. This 
would have placed the OBSS 
approximately 5 ft away from the 
NOAX covered samples for about 
 
Figure 4: NOAX Application for DTO 848 
 
Figure 5:  Deposition due to Orbiter DTO 848 on LF1 onto ISS after 5 
days 
Å after 5 days Formatted: Font: 10 pt, Bold
  
American Institute of Aeronautics and Astronautics 
 
5
30 minutes. Only the aft port side Payload Bay camera was in a position to receive NOAX contamination as the 
other cameras were shielded by equipment or were too far from the DTO to be a concern. 
As can be seen from Figure 5, less than an Angstrom of contamination was predicted for NOAX at the nominal 
temperature of 27°C. These levels will have a negligible impact on the ISS system level requirements. If the nominal 
temperature of the NOAX increased to 49°C, the deposition would still be negligible compared to the system level 
requirement. For the Lab Window, contamination due to the DTO will be a second or third order effect compared to 
the contribution of the Orbiter itself.  
Flight rules and on-orbit support prevented the SSRMS cameras from exceeding their contamination limits. 
Figure 6 details the levels of 
contamination that were predicted for 
the Payload Bay. If the Payload Bay 
camera looked directly at the DTO for 
the entire on-orbit duration, it would 
receive less than 30Å of contamination 
(most of which would be deposited in 
the first 6 hours). The SRMS would 
not exceed its limit of 100Å of 
contamination as long as it remained at 
least 3.5 ft away from the DTO. 
The OBSS is at highest risk of 
exposure to contamination when it 
performs a scan of a damaged RCC 
sample approximately 3 hours after the 
DTO has been performed. Analysis 
shows that the OBSS would receive 
less than 1Å of contamination during 
this half hour scan of the RCC sample 
for the nominal temperature of 27°C. If 
the temperature increases to 38°C the 
amount of contamination received 
increases to 2.5Å for the half hour 
scan. The ISS attitude was constrained to maintain temperatures less than 38°C. 
 
V. CONCLUSIONS 
No visor fogging was observed (as predicted) and no optical degradation of the OBSS sensors and the 
SSRMS/SRMS/PLB cameras occurred due to Flight LF1 (STS-114) DTO 848. It was also found that on-orbit 
temperatures were significantly lower than expected, resulting in over prediction of contaminant deposits.  
In addition, the contamination observed in the HTV (EMU visor fogging) was successfully explained, and it was 
determined that conditions on-orbit would not cause fogging to occur.  
Also, an uncured ablative repair compound was successfully tested for condensable outgassing rates, and the 
critical initial time data was utilized for analysis tasks. The analysis results were used to generate flight rules to 
mitigate impacts to the ISS, EMU and Orbiter optically sensitive surfaces, as required. 
The analysis tools and techniques developed for ISS external contamination analysis were critical to modeling 
contamination transport. Techniques used for Flight LF1 DTO 848 will be used for Flight ULF1.1 DTO 848. New 
analyses will be conducted due to a substantial increase of NOAX usage and possible changes in the Orbiter Payload 
Bay thermal environment. 
 
VI. REFERENCES  
1Master Development Test Plan for the RCC On-orbit Crack Repair Material (JSC-62487) 
2ASTM, “Standard Test Method for Contamination Outgassing Characteristics of Spacecraft Materials, E 1559 – 
03,” ASTM International, Oct. 2003. 
Å after 5 days
CMG
FSE
 
Figure 6: Angstroms of Contamination in Orbiter Payload Bay 
after 5 Days of Outgassing from NOAX on LF1 (STS-114) 
  
American Institute of Aeronautics and Astronautics 
 
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3Soares, C., Mikatarian, R. and Barsamian, H., “International Space Station Bipropellant Plume Contamination 
Model,” 8th AIAA/ASMT Joint Thermophysics and Heat Transfer Conference, AIAA 2002-3016, St. Louis, 
Missouri, 24-27 June 2002. 
4Soares, C.E. and Mikatarian, R.R., “Understanding and Control of External Contamination on the International 
Space Station,” Proceedings of the 9th International Symposium on Materials in a Space Environment, European 
Space Agency (ESA) publication SP-540, Noordwijk, The Netherlands, 2003. 
5Boeder, P.A., Visentine, J.T., Shaw, C.G., Carniglia, C. K., Alred, J.W., Soares, C.E., "Effect of a silicone 
contaminant film on the transmittance properties of AR-coated fused silica", SPIE-04, 2004. 


Space Shuttle Thermal Protection System Repair Flight Experiment Induced Contamination Impacts

Space Shuttle Thermal Protection System Repair Flight Experiment Induced Contamination Impacts

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