Evaluation of Space Enviroment
and Effects on Materials
(ESEM) Archive System
NASA Langley Research Center
Hampton, Virginia

Final Report
United States Developed ESEM Experiments
Evaluation of Space Environment and Effects on Materials

Flown on STS-85 as one element of a NASA - NASDA collaboration.
	NASA - Langley Research Center Hampton, VA 23681-2199

Acknowledgments

The United States ESEM Team members would like to express their gratitude to the Japanese ESEM Team members. First, for the opportunity to participate with them in the NASDA / NASA collaborative to implement the ESEM Experiments. Second, for their frequent and helpful support to us during the development of the ESEM experiments we provided. And third, for the very generous sharing of information regarding the ESEM experiments they developed and the results of their post-flight analysis. In particular the United States team would like to recognize the following Japanese team members:

Mr. Kichiro Imagawa, National Space Development Agency of Japan
Mr. Yutaka Okada, National Space Development Agency of Japan
Mr. Chiaki Kamakura, National Space Development Agency of Japan
Mr. Katsumi Fusegi, Ishikawajima-Harima Heavy Industries Co., Ltd.,Japan
Mr. Masaaki Ichikawa, Ishikawajima-Harima Heavy Industries Co., Ltd.,Japan
Mr. Yukihito Kitizawa, Ishikawajima-Harima Heavy Industries Co., Ltd.,Japan
Mr. Raita Amagata, Ishikawajima-Harima Heavy Industries Co., Ltd.,Japan

The Principle Investigators for the United States ESEM experiments would also like to thank the other NASA ESEM Team Members at the Langley Research Center and in particular Ms. Junilla I. Applin and Mr. Robert A Dillman who served as the Manager and Chief Engineer for the ESEM Project at the Langley Research Center for jobs well done.

Contributing Authors

Junilla I. Applin, John W. Connell, Robert A. Dillman, Gale A. Harvey, Donald H. Humes, James L. Jones, William H. Kinard, & Sheila A.Thibeault

National Aeronautics and Space Administration
Langley Research Center, Hampton, VA


Richard L. Kiefer, Robert A. Orwoll, J. E. Harrison, & V. M. Ronesi

College of William & Mary
Williamsburg, VA


Gary G. Pippin

Boeing Phantom Works
Seattle, WA

INTRODUCTION
The Evaluation of Space Environment and Effects on Materials (ESEM) experiments were developed, flown in-space on the STS-85 mission, returned to Earth and analyzed as one element of a collaboration between the National Space Development Agency (NASDA) of Japan and the National Aeronautics and Space Agency (NASA) of the United States (U.S.). The principle element of this Japanese / U.S. collaboration was the flight demonstration of the manipulator system NASDA is developing to service the Exposure Facility (EF) which will be a part of the Japanese Experiment Module (JEM) on the International Space Station (ISS).

The primary objectives of the ESEM experiments were to investigate atomic oxygen effects on materials, cosmic dust and man-made debris, and Shuttle induced contamination. The secondary objective of the ESEM collaboration was to identify and evaluate candidate space exposure experiments for the EF and other attached payload sites that will be provided on the ISS truss structure when the ISS becomes operational; and, to evaluate approaches that may be used to perform the identified candidate experiments.

This three part document is the final report on the U.S. efforts in the ESEM collaboration. The Japanese have also prepared a final report on their efforts and that Japanese report and this U.S. report represent the final reporting on the total NASDA / NASA ESEM collaboration.

Part I of this document provides a brief overview of the ESEM experiments, how they were accommodated on the STS-85 mission, the STS-85 Mission profile and the Japanese and U.S. roles in implementing these experiments. Part II provides detailed descriptions of the U.S. developed ESEM experiments and the final results obtained from their post-flight analyses. Part III identifies candidate exposure type experiments that should be considered for flight on the EF and other ISS sites; and, it discusses approaches to these candidate experiments.

Additional information on the U.S. ESEM experiments can be obtained at this Internet site.

PART I

Overview of the ESEM Experiments - The Japanese and the U.S. investigators each developed separate experiments to address the 3 primary ESEM objectives. All of the developed experiments were passive, relying solely on comparisons of pre-flight observations and post-flight observations to establish the effects of the in-situ space exposure on the flight specimens. The specimens that were flown in the U.S. experiments to investigate the atomic oxygen effects and Shuttle induced contamination are shown in Figure 1.

There were differences in the U.S. and the Japanese approaches to some of the atomic oxygen and contamination experiments, thus allowing these different approaches to be evaluated as candidates for future space exposure experiments on the ISS. For example, Japanese and U.S. investigators both exposed materials and coatings specimens directly to the atomic oxygen flux to investigate the effects. One U.S. investigator also exposed specimens in concentrators that were conceived to increase the atomic oxygen flux and the Solar flux on the specimens and thus to provide accelerated time testing.

The U.S. experiment to collect cosmic dust and man-made debris utilized the Aerogel specimens shown in Figure 2. The very low density Aerogel appears cloudy, but transparent, in the aluminum mounting frame.

The Japanese experiment to collect cosmic dust and man-made debris also used Aerogel, however, the Japanese investigators deposited a gold film on the exposed surface of their Aerogel anticipating that the film would aid the post flight searches to locate impact sites. The Aerogel used by the U.S. investigators had no coating and it was more dense than the Japanese Aerogel. As with the atomic oxygen experiments, these differences provided opportunities to evaluate the different approaches as candidates for future experiments on ISS.

Accommodations for the ESEM Experiments: The Japanese and the U.S. ESEM specimens were mounted on five panels which were in turn attached to the stair step like structure shown in Figure 3.

Figure 3. Photograph of the ESEM Experiment specimens
mounted on the stair step like support structure.

The Aerogel specimens for the NASDA and the NASA cosmic dust and debris collection experiments were mounted on the top panel. The specimens for the NASDA atomic oxygen, materials and contamination experiments were mounted on the next three panels. The specimens for the NASA atomic oxygen, materials, and contamination experiments were mounted on the bottom panel.

As stated in the Introduction, the ESEM experiments were exposed to the space environments during the STS-85 Shuttle Mission. The support structure with the ESEM experiments was mounted on an MPESS Pallet for the transportation to and from space and for the exposure in space with the Shuttle. The hardware for the Japanese Manipulator Flight Demonstration (MFD) was also mounted on the same MPESS Pallet. Figure 4 is a photograph of this MPESS Pallet with the ESEM and MFD hardware being installed in the Shuttle cargo bay.

Figure 4. A photograph of the MPESS Pallet, the ESEM Experiment support structure and the MFD hardware being installed in the Shuttle cargo bay.

STS-85 Mission Profile: The key phases with the Discovery vehicle on the STS-85 Mission for the ESEM Experiments are illustrated in Figure 5. These phases were namely, the launch to orbit, the on-orbit exposure, and the landing to retrieve the experiment specimens.

The experiment specimens were exposed to the environments that existed in the Discovery cargo bay during the final preparations for launch and during the lift-off to orbit phase of the mission. The cargo bay doors were opened on orbit at 12:16 PM EDT on August 7, 1997 - 1 hour and 35 minutes after the lift-off of the Discovery for the STS-85 Mission. The doors were closed at 3:32 am EDT on August 19, 1997 - shortly before the de-orbit burn. This allowed the ESEM experiment specimens to be exposed to the space environments for 11 days, 15 hours and 16 minutes. The ESEM specimens were again exposed to the environments that existed in the Discovery cargo bay during the de-orbit and landing phase of the mission and during the post-landing de-integration operations at Kennedy Space Center (KSC).

The orbit of the Discovery on the STS-85 mission was near circular at an inclination of 57⁰. The altitude of the orbit for most of the mission was approximately 160 nautical miles. The time history of the orbit altitude during the entire mission is presented in Appendix A with the discussion of the NASA Cosmic Dust and Debris Capture Experiment. The orientation of the Discovery was changed frequently during the mission. A table of the orientation with respect to the velocity vector is also presented in Appendix A.

An estimate of the atomic oxygen fluence on the experiment specimens while on orbit with the cargo bay doors open is presented in Appendix B with the discussion of the Boeing specimens flown on the ESEM experiment.

After the Discovery landed at the KSC and was towed into the Orbiter Processing Facility, the MPESS Pallet with the ESEM hardware and the MFD hardware was removed from the cargo bay. After removal, the MPESS Pallet was transported to the O&C Facility where the panels with the ESEM experiments were removed from the support structure and the specimens were released to the principle investigators for shipment back to their respective laboratories for analysis.

NASDA and NASA Roles in ESEM: The development and flight qualification of the Japanese and the U.S. ESEM Experiments was independently performed by each respective party. Each party was also independently responsible for the transportation of their qualified hardware to the KSC for integration into the flight ready ESEM payload for the Shuttle.

An ESEM Project Office was established at the LaRC to manage the development and qualification of the U.S. ESEM Experiments. Junilla I. Applin was the ESEM Project Manager and Robert Dillman was the Project Chief Engineer. This project office was also responsible for the design of the attachment hardware for the U.S. experiment specimens and for all of the necessary qualification testing. The Principle Investigators (PI’s) for each of the U.S. experiments were responsible for the development of their respective test specimens and for the pre-flight characterization of their specimens.

NASDA was responsible for the pre-flight integration of the ESEM experiment hardware with the MFD hardware on the MPESS Pallet. NASA was responsible responsible for the integration of the MPESS Pallet in the Shuttle cargo bay, the Shuttle flight operations required for the STS-85 Mission, and for the removal of the MPESS Pallet from the cargo bay after the retrieval. NASDA was then responsible for the post-flight de-integration of the ESEM and MFD hardware from the MPESS Pallet after it was removed from the cargo bay and for the release of the hardware to the responsible parties. Each party was then independently responsible for the post-flight analysis and reporting of the results from the ESEM Experiments they developed.

PART II

NASA assembled five experiments for the ESEM collaboration. The detailed descriptions of these experiments and the final results of the post-flight analysis of each are presented in Appendices A through E. These appendices were written by the Principle Investigators associated with each respective experiment.

Appendix A, THE COSMIC DUST COLLECTION EXPERIMENT ON STS-85, is authored by Donald H. Humes and William H. Kinard of the NASA Langley Research Center, Hampton, Virginia. The data on the Discovery attitude and orbital altitude history is also presented in Appendix A. This experiment was funded as a part of the NASA Space Environments and Effects Program at the NASA, Marshall Space Flight Center, Huntsville, Alabama.

Appendix B, FINAL REPORT ON ANALYSIS OF BOEING SPECIMENS FLOWN ON THE EFFECTS OF SPACE ENVIRONMENT ON MATERIALS EXPERIMENT, is authored by Harold G. Pippin of the Boeing Phantom Works, Seattle, Washington. An estimate of the atomic oxygen fluence the ESEM Experiments were exposed to during the STS-85 Mission is also presented in Appendix B. The Boeing Company funded this experiment as a part of their internal research and development activities (IRAD)

Appendix C, THE EFFECTS OF THE SPACE ENVIRONMENT ON POLYETHERIMIDE FILMS, is authored by R. L. Kiefer, R. A. Orwoll, J. E. Harrison and V. M. Ronesi of The College of William and Mary, Williamsburg, Virginia; and, by S. A. Thibeault of the NASA Langley Research Center, Hampton, Virginia. This experiment was funded as an element of the Precision Deployable and Inflatable Structures Program at the Langley Research Center.

Appendix D, THE EFFECT OF LOW EARTH ORBIT ATOMIC OXYGEN EXPOSURE ON PHENYLPHOSPHINE OXIDE-CONTAINING POLYMERS, is authored by John W. Connell of the NASA Langley Research Center, Hampton, Virginia. This experiment was also funded as an element of the Precision Deployable and Inflatable Structures Program at the Langley Research Center.

Appendix E, SHUTTLE INDUCED CONTAMINATION, is authored by Gale A. Harvey of the NASA Langley Research Center, Hampton, Virginia. This experiment was funded as a part of the NASA Space Environments and Effects Program at the NASA, Marshall Space Flight Center, Huntsville, Alabama.

PART III

Background on Exposure Experiments for the ISS
Accommodations for in-situ exposure experiments were envisioned in most of the early concepts for space stations and such accommodations have survived in the evolution’s of these concepts becoming first a part of the Skylab, later a part of the Mir, and now to be a part of the ISS when construction is completed.

The value of the experiments that can be performed using such space exposure accommodations was vividly illustrated in the treasure trove of science and technology data that has been generated from the experiments flown on the Long Duration Exposure Facility (LDEF) and from similar exposure experiments flown on Skylab, Shuttle, and Mir.

As stated in the introduction to this report, the secondary objective of the ESEM collaboration was to identify and evaluate candidate experiments and approaches to these experiments for the EF on the JEM and other attached payload sites that will be provided when the ISS becomes operational.

The U.S. ESEM Investigators comments on such experiments and approaches, which are reported here, are based on their experience with the ESEM experiments and on their experience with exposure experiments on the LDEF and the Mir. Candidate exposure experiments are discussed first. The technical approaches to these experiments are discussed second.

Candidate Exposure Experiments for the ISS
Categories of Experiments - Candidate in-situ space exposure experiments for the ISS can be placed in one or more of the following three categories:

experiments to measure the exposure environments that are being encountered by the ISS
experiments to measure the effects of the environments that are being encountered by the ISS on exposed surfaces
experiments to utilize the exposure environments that are being encountered by the ISS to accomplish other objectives

Candidate experiments for the ISS have been identified in all three categories, however, because of the experience of the U.S. ESEM investigators, the evaluations discussed here are limited to experiments in the first and second categories only. It should be pointed out that only a few of the many candidate experiments that should be considered are address in this section.

Induced Environments and Effects - The natural environments found in the high inclination low Earth orbit of the ISS (i.e., ionizing radiation, atomic species, solar radiation, meteoroids) have, with some exceptions, been reasonably well characterized. The environments that will be induced by the presence of the ISS, the logistic vehicles flying to and from the ISS and by other orbiting spacecraft are not so well characterized. Exposure experiments to address these induced environments and their effects should be given high priorities for early flights on the ISS.

The more critical of these induced environments will probably result from the molecular outgassing of materials, overboard vents or dumps of gases and liquids, and particles that are released from the ISS, docked logistic vehicle, and other spacecraft operations. Examples of these induced environments and some of their effects are illustrated in Figures 6 through 10. Figure 6., is a photograph of an LDEF experiment tray showing depositions that resulted from the molecular outgassing of a silicon rubber gasket on the facility.

Figure 6. Depositions on an LDEF experiment tray that resulted from molecular outgassing of silicon rubber.

The deposition area that was exposure to atomic oxygen and solar UV radiation during the 69 month LDEF Mission has been colored making it more visible.

A photograph of zinc surfaces that were a part of the MEEP Polished Plate Meteoroid and Debris Experiment is shown in Figure 7.

These surfaces were exposed on the Mir for approximately 19 months. The spattering of drops from liquids vented from the Mir or the Shuttle while it was docked to the Mir can be seen on the surfaces of the plates. Several of the drops actually ran on the zinc surface after the impingement.

         
Figure 7. Splatters on zinc plates that resulted from liquids vented from Mir or the Shuttle while it was docked to Mir. The zinc plates were exposed on Mir for 18 months as a part of the MEEP.

A photograph of a fiber particle released from the Shuttle cargo bay liner that impacted the ESEM Cosmic Dust Collection Experiment is shown in Figure 8. This experiment and the illustrated fiber is discussed in Appendix A of this report.

Figure 8. Fiber particle from Shuttle cargo bay liner collected in ESEM Cosmic Dust Collection Experiment.

A larger particle that was released from a surface on the LDEF and then later impacted on an LDEF experiment thermal blanket causing the blanket to rip is shown in Figure 9.

Figure 9. A 6061-T6 aluminum particle released from an LDEF surface that later impacted another surface on the facility.

This particle, which was found at it’s impact site after retrieval of the LDEF from orbit, was produced during the manufacture of the LDEF in a drilling operation on one of the facilities 6061-T6 structural members.

Another larger oxidized silver particle of unknown origin that also impacted on an LDEF experiment thermal blanket is shown in Figure 10.

This particle, which was also found at it’s impact site after the retrieval of the LDEF, had pitted black surfaces which indicate that it had been exposed to the atomic oxygen environment in space for an extended period of time. The particle probably was a silver electrical connect that broke free from a spacecraft.

The severity to future spacecraft of these illustrated self induced environments will depend on the specific spacecraft systems that are impacted by them. The absorption or emission of thermal coatings can be changed thus altering temperatures; changes can occur in the optical properties of windows thus limiting the data that can be gathered through the window; the solar transmission of covers on solar cells can be diminished resulting in less power generation; materials can be corroded; and, physical impact damage can result in punctures of pressure vessels and other types of mechanical damage.

What ever the specific effects turn out to be, spacecraft will encounter them even with the best of efforts to midigate them. They were encountered in Skylab, Shuttle, LDEF and Mir missions; and, they are expected in the ISS missions. The NASA ISS Program, in fact, has a plan for an Environment Monitoring Package (EMP) to fly on the station, however, the resources for the development of the EMP have not to date been authorized. The requirements in this EMP plan state that the following environments will be monitored: a) ion and neutral gas constituency, b) mass deposition, c) ambient pressure, and d) plasma properties. Both NASDA, the European Space Agency (ESA) and Russia also have plans to development environmental monitoring instruments for the ISS. Additional information on these monitoring plans can be obtained at the following Internet site:

http://www1.msfc.nasa.gov/JA/JA51/emp.html

The instruments planned in these monitoring packages are generally active and relatively expensive; and, the emphasis of these packages is on monitoring the environments - not on monitoring the effects of the environments. The monitoring experiments discussed in the following sections of this report generally involve passive and inexpensive approaches that can be complimentary to the planned active instrument packages and in times of limited budgets these less expensive experiments maybe easier to implement early in the ISS construction phase.

Approaches to In-Situ Exposure Experiments for ISS
ISS Inspections - Regular inspections of the condition of all of the exposed surfaces of the ISS components using well thought out protocols can provide the best single approach to monitor the induced environments the ISS is encountering and also to establish the synergistic effects these induced environments and the natural space environments are having on materials and systems. Since the induced environments can vary widely between different locations on the ISS, the regular inspections of all surfaces is emphasized. Because of the size of the ISS, the regular inspection of all ISS surfaces will also increases the likelihood that rare events, such as the impact of larger debris particle, can be observed.

The regular ISS inspections will be analogous to the inspections of the Shuttles that are currently performed after each flight to look for meteoroid and debris impact damage. The Shuttle inspections provided the data that allerted mission planners of the fact that the debris impact flux on the Shuttle was increasing and thus they needed to limit ram direction exposures of the Shuttle’s impact vulnerable open cargo bay. This illustrates the type of benefit the ISS can realize through regular inspections.

To support the analysis of the data from inspections of the ISS surfaces, specimens of the various types of exposed materials should be maintained in terrestrial laboratories. Experiences with LDEF, Mir and ESEM experiments have demonstrated that these control specimens can on occasions be critical when attempting to re-create in the laboratory the conditions that resulted in specific effects observed during the inspections.

Also to support the analysis of inspection data, an accurate, complete and user friendly data base of the ISS operational history should be maintained. This data base will also be valuable to support the analysis of data obtained from other experiments on the ISS. This data base should include information such as - the history of the ISS orbit parameters, the ISS attitude history (particularly with respect to the velocity vector), the event time lines associated with logistic flights to and from the ISS, the event time lines of ISS and onboard experiment operations, and anomalies noted in ISS system operations. Experience with experiments on the Shuttle and on the Mir has shown that such historical data can be very difficult to obtain after a mission when it was not planned for in advance.

Exposure of Retrievable Test Specimens - The exposure, at different locations on the ISS, of well characterized specimens that can later be retrieved for detailed laboratory investigations provides another excellent approach to monitor the induced environments that the ISS is encountering and the effects of these environments. Retrieved specimens will allow a broad spectrum of laboratory tools and instruments to be utilized in the post flight analysis and thus the generation of much more detailed data than can be obtained from the in-situ ISS inspections. The retrieved specimens can be materials that are identical to ISS materials, materials for other applications that are exposed to investigate their stability in the ISS environment, or, special materials that are exposed for studies of specific environments such as contamination collectors.

The ESEM experiments had examples of all of these types of specimens. The Atomic Oxygen Effects on Materials experiment (Appendix B) exposed specimens of materials used in the ISS construction. The two ESEM experiments described in Appendix C and Appendix D exposed new materials that are being developed for other applications to investigate their resistance to bombardment by atomic oxygen. The shuttle induced contamination experiment described in Appendix E exposed special materials to collect contamination and the Cosmic Dust Collection experiment (Appendix A) exposed special materials collect fragments of impacting micrometeoroids and man-made debris.

The use of concentrators, such as shown in Figure11 and described in Appendix B, to increase the atomic oxygen and the Solar flux on retrievable specimens that are exposed on the ISS can be beneficial. They can allow early previews of effects that won’t be seen until later on ISS materials and components. Such previews may allow mitigation steps to be taken before the environments seriously effect materials on the ISS and thus it’s operations.

Figure 11. Photographs of atomic oxygen and solar flux concentrators developed by Boeing Phantom Works and flown on ESEM.

It should be noted that some experiments, when utilizing retrievable test specimens, may suffer from the restricted sampling capabilities that can be provided with a limited number of relatively small size specimens. This limitation is not a factor for experiments investigating, for example, atomic oxygen or solar ultra violet effects. For experiments looking for data on rare events such as meteoroid and debris impacts this limitation can be major factor.

Figure 12. The NASA - LaRC concept for an In-situ Scanner for Orbiting Debris (ISOD).

The effective sampling area for ISOD scanning for 1 mm size particles compared with the effective sampling areas for surface inspections of the ISS and LDEF is illustrated in Figure 13.

Since ISOD can detect larger particles at greater distances, it has an even more effective sampling area for 1 to 10 cm particles when compared with sampling from ISS or LDEF inspections

Figure 13. Illustration of the effective area in which debris larger than 1 mm can be monitored compared with the effective monitoring areas achieved by inspecting the surfaces of the ISS or the LDEF.

Concluding Remarks regarding Exposure Experiments for ISS

The need to monitor the induced environments surrounding the ISS and the synergistic effects they (and the natural space environments) are having on the ISS and other on-board systems can not be over emphasized. The monitoring of these environments can identify potential problem situations early and the mitigation steps that should be considered. Without the monitoring and the implementation of the indicated mitigation steps, unexpected induced environments can reduce the performance and even the life of ISS systems; and, they can have detrimental effects on exposure experiments on the ISS.

Many other spacecraft will encounter induced and natural space environments similar to those the ISS encounters; thus, the monitoring of the induced environments and the synergistic effects they and the natural space environments are having on ISS will produce a data base that will be valuable to the designers of these other spacecraft.

The EMP planned by NASA and the other environmental monitoring experiments planned by NASDA, ESA and Russia should be implemented.

The U.S. developed ESEM experiments are examples of other experiments that can and should also be emplimented on the ISS in the early phase of it’s operation. The ESEM experiments successfully accomplished their objectives which were focused on environmental effects. The approaches they employed offer valid and inexpensive approaches for early ISS exposure environment and environmental effects experiments and the data they can obtain can compliment the data from the planned EMP and other related experiments.

The regular inspection of the ISS external surfaces following carefully planned protocols with supporting data bases and achieved material samples is another proven and inexpensive approach for monitoring environments and environmental effects and it too should be implemented early in the ISS construction phase. The data from these inspections can also compliment the data expected from the EMP and other experiments.

Because of the potential impact to the ISS of the man-made orbiting debris environment and because terresterial instruments can not reliably monitor the populations of debris in the 1 mm to 1 cm size range, an in-situ scanning instrument such as the ISOD should be a high priority candidate exposure experiment for the ISS. Debris monitoring in this size range is not included in the NASA plans for an EMP nor is it included in the NASDA, ESA or Russian plans for environmental monitoring experiments.

Appendix A | Appendix B | Appendix C | Appendix D | Appendix E

---

AORP | Clementine | EuReCa | ESEM | Hubble
LDEF | MDIM | MEEP | MIS | MPID