Synergies Between Space Research and Space ...

AIAA 2007-547

45th AIAA Aerospace Sciences Meeting and Exhibit 8 - 11 January 2007, Reno, Nevada

Synergies between Space Research and Space Operations— Examples from the International Space Station Judy M. Tate 1 Engineering Science Contract Group, NASA Johnson Space Center, Houston, TX 77058 USA John K. Bartlett 2, Julie A. Robinson 3, Christian C. Maender2, Lakshmi Putcha 4, Scott M. Smith4, Mark A. Bowman 5 NASA Johnson Space Center, Houston, TX 77058 USA Scott A. Dulchavsky 6 Henry Ford Health System, Detroit, MI 48202 USA Ashot E. Sargsyan 7 Wyle Laboratories, NASA Johnson Space Center, Houston, TX 77058 USA Sharon K. Miller 8, Bruce A. Banks8, Kim K. deGroh8 NASA Glenn Research Center, Cleveland, OH 44135 USA and Denver Tsui 9 Engineering Science Contract Group, NASA Johnson Space Center, Houston, TX 77058 USA

Primary objectives for the International Space Station (ISS) in support of the Vision for Space Exploration include conducting research to counteract the harmful effects of space on human health, test new space technologies, and learn to operate long-duration space missions. In pursuit of these objectives, NASA is interested in closer cooperation between the ISS operational community, scientists, and engineers. To develop the exploration vehicles for missions to the moon and Mars, NASA must test materials, foods, and medicines to ensure their performance in the space environment. These results will enable important decisions on the materials to be used for future space vehicles. Another critical factor for the success on future missions beyond Earth orbit is the capability for repairs of equipment. On the ISS, the practice of crewmembers performing repairs in microgravity will increase our understanding of the repair processes in space; when these capabilities are needed during future space exploration missions, we will have the knowledge and experience to perform them. The ISS is a unique and irreplaceable training ground for building the operational knowledge required to safely conduct future exploration missions, and the growing links within the science, engineering and operations communities are reinforcing the value of that training. Current interactions between the communities that support the ISS have already produced many synergies that are significantly accelerating NASA's advancement towards future exploration missions in support of the Vision. 1

ISS Program Scientist’s Office, International Space Station, Mail Code JE-5EA. ISS Payloads Office, International Space Station, Mail Code OZ. 3 ISS Program Scientist’s Office, International Space Station, Mail Code OA. 4 Human Research and Countermeasures Division, Space Life Sciences, Mail Code SK. 5 Human Space Flight Program – Russia, International Space Station, Mail Code OK. 6 Medical Operations Branch, Space Medicine Division, Space Life Sciences, Mail Code SD2/WLS. 7 Henry Ford Health System, CFP-1 RM 110. 8 Electro-Physics Branch, Power and Electric Propulsion Division, Mail Code MS309-2. 9 Biomedical Systems, Engineering, Mail Code EB. 2

1 American Institute of Aeronautics and Astronautics This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

I. Introduction

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NDER the Vision for Space Exploration , NASA is now retooling to replace the Space Shuttle, return to the moon by 2020 and use the knowledge gained from all previous programs to send the first humans to Mars. NASA’s primary objectives for the International Space Station (ISS) in support of the Vision are to conduct research to counteract the harmful effects of space on human health, test new space technologies, and learn to operate longduration space missions. Prior to the announcement of the Vision, each of these objectives were being pursued by separate communities—researchers, engineers, and operations specialists. 2 The applied nature of exploration-relevant research on the ISS can be expected to provide many opportunities for the synergies between daily operations in space and scientific research. To illustrate the importance of such relationships, we present examples of synergies between science, engineering and operations that have occurred on the ISS to date. The examples fall into three categories: medical, materials, and in-space repair. Interactions between the communities in support of the ISS have produced synergies that will significantly improve the success of future exploration missions in support of the Vision.

II. Medical Research and Flight Medicine Each crewmember on the ISS participates as a subject in as many as six different medical investigations during their mission. At the same time, a flight surgeon operationally monitors the health of each crewmember throughout their stay on the ISS, a clinical medicine process known within NASA as flight medicine. We provide two examples of synergies in this area which have changed both the research objectives and the clinical applications of research results. The new ISS Medical Project (ISSMP) seeks to bring such synergies to all ongoing and future human research on the ISS. 3 A. Diagnostic Ultrasound Research and Telemedicine Much of the ISS biomedical research hardware has been designated by the operational medical community as a potential augmentation to the ISS Integrated Medical System, designed to diagnose and treat injured or ill crewmembers. For example, the Human Research Facility -1 (HRF-1) on the ISS includes the first permanent medical imaging capability for diagnostic ultrasound in space. Ultrasound is a medical imaging technique that uses high-frequency sound waves and their echoes to map internal human anatomy. Ultrasound has long been used to diagnose a variety of medical conditions, including gallstones and kidney stones, muscle and ligament injuries, and even eye trauma, something impossible to perform with conventional X-ray techniques. 4 Although it was always anticipated that the equipment would be used if a medical contingency arose on orbit, the original medical operational uses were relatively narrow in scope. 5 The Advanced Diagnostic Ultrasound in Microgravity ∗ (ADUM, Scott A. Dulchavsky, Henry Ford Health System, Detroit, MI) investigation established the ability of minimally trained crewmembers to obtain diagnosticquality imagery for a wide-variety of organs and systems in microgravity. On board the ISS, ultrasound has been adapted as a useful tool to diagnose medical emergencies that could occur during space missions5. The ultrasound device transmits high-quality images from scans by satellite to trained medical personnel on Earth, who could then suggest appropriate treatment. The images are transmitted in real time, with only a slight delay (< 2-seconds); ADUM gives crewmembers the tools to assess injuries using real-time remote assistance from medical experts on Earth. ADUM enhanced the medical support capability on the ISS missions, by transforming research hardware into an available operational capability. The technology is equally applicable on lunar and Mars missions, though the transmission delays would be slightly longer resulting in near real-time operations. 6,7,8 Protecting medical privacy while performing ADUM on board the ISS presented significant operational hurdles. The video data and voice discussions could not be simply transmitted on open channels throughout mission control, and care needed to be taken to protect privacy at each point in transmission between researchers and the crewmembers. Thus voice and video from the ISS were both privatized for the ultrasound scan session. The video traveled from the ISS to a console in the Mission Control Center in Houston (known as “Houston TV”). From Houston TV the video was restricted and sent to a separate building, the video distribution center at Johnson Space Center (JSC), or “Johnson TV”, not for distribution but to be “recorded only” for later review by the ADUM principal investigator. From Houston TV the video was also sent via a dedicated, restricted video line to the JSC Telescience Support Center (TSC), a mission monitoring console near mission control that is used by researchers during operations of their experiments. The video was made available to the medical investigators on console in the ∗

This study was supported by NASA Flight Grant NNJ04HB07A and the National Space Biomedical Research Institute Grant SMS00301. 2 American Institute of Aeronautics and Astronautics

TSC, and simultaneously provided to the principal investigator at the Henry Ford Health System in Detroit, Michigan via a secured website connection (see Fig. 1 for a detailed flow of information from the ISS to the investigator). As for audio, the Space-to-Ground (S/G) communications were “privatized” (restricted to private channels only accessible by a limited few) for communication between the crew and the researchers. Of the two S/G loops aboard the ISS, S/G2 was privatized by the Ground Controller in the Mission Control Center so the crewmembers could talk directly and privately to the medical investigators in the TSC. Utilizing an internet voice distribution system (IVODS) the investigator in Detroit was also able to speak directly to the crew and provide words of guidance. The other voice loop, S/G1, was left in normal mode to allow for communication with the rest of the control team, as needed. Equipment status information was also continuously available to ground controllers to monitor the operational equipment on board the ISS, without interfering with the medically sensitive video and private voice communications.

Figure 1. ADUM Data flowchart. Pictorially exhibits how the ADUM video and voice traveled from ISS to Johnson Space Center in Houston, Texas then to the ADUM principal investigator in Detroit, Michigan. The operational approaches developed to support ADUM have extended possible applications of telemedicine far beyond what was originally envisioned. As this investigation revealed the potential uses of ultrasound in a variety of medical contingencies, more investigational sessions were conducted to obtain additional observations of the “space normal” conformation of healthy organs in microgravity.6,7,8 The ADUM investigation used scientific approaches to develop methodology for operational space medicine, such methodology is just as useful and enabling for space biomedical research. During the operation of ADUM on the ISS, scientists, engineers, and operations specialists accumulated an unprecedented amount of new knowledge and special expertise. ADUM results are therefore quite enabling not just for operational medical use, but also for 3 American Institute of Aeronautics and Astronautics

subsequent HRF research activities, as they reduced pre-flight crew training requirements for the ISS ultrasound; reduced crew and system time expenditures from prohibitive to reasonable levels6; enabled research planning due to the established methodology and experience with ultrasound protocol and application development for microgravity use6; set examples of the ISS-based ultrasound use and research published in peer-reviewed literature or available from the investigator and research support teams7; established validated solutions for private data protection in full compliance with the current privacy laws and regulations, as well as with applicable NASA and the ISS policies and practices.5 ADUM is a bright example of an investigation on the cusp of medical practice and biomedical research. It uses the same principle which has propelled world-class medical institutions to excellence––utilizing the synergies in the areas of patient care, teaching, and research and managing them in a mutually enabling fashion. The successful results of ADUM have also made their way into professional sports. Trainers for the 2006 Winter Olympics and three major professional sports teams in Detroit, Michigan, including the Red Wings (hockey), Tigers (baseball) and Lions (football) have begun using the ultrasound remote guidance techniques developed on the ISS. Just as the ISS crewmembers were trained to obtain medical-quality diagnostic ultrasound images in space with the help of remote guidance from experts on Earth, sport physicians and trainers can now perform similar scans on injured players at each of their respective sport complexes by taking advantage of ultrasound experts available remotely. 9 Rapid, point-of-care diagnosis during an athletic event is only one of the potential benefits of this new ultrasound technology. The principal investigator for ADUM is investigating video streaming technology, which could extend use of this technology to ambulances and accident scenes as well as remote areas. This will allow emergency care decisions, such as transport to local hospitals versus trauma centers, to be made with greater certainty. Dr. Dulchavsky is also working with the military, fire and rescue agencies, since the method could benefit search and rescue operations following natural disasters in remote areas where a doctor might not be readily available in person.9 B. Foot Force Measurements and Exercise Prescriptions It is well known that reduced loads on muscles and bones in microgravity are the major reason for the bone and muscle loss observed in long-duration crewmembers on the ISS. Tension between muscle and bone on Earth fosters the renewal of bone, and without exercise in orbit, crewmembers bones begin to break down faster than they are reformed. 10,11 Daily exercise while in a microgravity environment is critical for crewmembers to maintain the muscle strength to complete necessary tasks, including strenuous extra vehicular activities (EVAs, or spacewalks). To maintain bone and muscle mass for crewmembers the ISS houses three types of exercise equipment: weightlifting––the Interim Resistive Exercise Device (IRED), stationary bicycle––the Cycle Ergometer with Vibration Isolation System (CEVIS), and treadmill––the Treadmill Vibration Isolation and Stabilization (TVIS).3 Figure 2. Exercise Equipment on ISS. From left to right, The Foot/Ground Reaction Forces Astronaut William S. (Bill) McArthur, Expedition 12 commander During Spaceflight (Foot, Peter Cavanagh, and NASA ISS science officer, uses the CEVIS while participating The Cleveland Clinic, Cleveland, OH) in the Foot experiment in the Destiny laboratory of the ISS. experiment investigated how crewmembers McArthur wore the specially instrumented Lower Extremity utilize their lower extremities during Monitoring Suit (LEMS), cycling tights outfitted with sensors, normal workdays in space. Crewmembers during the experiment (ISS012E18576). McArthur, equipped put on instrumented trousers that measured with a bungee harness, exercises on the TVIS while participating the electrical impulses associated with in the final run of the Foot experiment in the Zvezda Service muscle activity and contained goniometers Module of the ISS (ISS012E20120). (angle sensors) to measure ankle, knee, and hip movements. They also wore a pair of running shoes instrumented with force sensors to accurately measure the 4 American Institute of Aeronautics and Astronautics

loading on the feet that takes place in microgravity, mainly during exercise periods. Besides providing a better understanding on how crewmembers use their legs in space, this study has provided quantitative data measuring actual loading on a crewmember during exercise periods on the treadmill, stationary bicycle, and resistive exercise device. Measuring the actual forces which a crewmember is subjected together with pre- and post-flight measurements of bone density and muscle volume provided the first insight into potential correlations between forces they experience in microgravity and resulting bone and muscle loss.13 The original experiment objectives were focused on comparing typical daily activity on Earth and on the ISS. Early in the experiment, the participating crewmember suggested additional runs focused on different settings of the exercise hardware. Preliminary results from this subject indicated that forces experienced during treadmill runs were approximately 63% of the forces that would have been experienced while running on a treadmill on Earth— these lower forces were accompanied by significant loss of bone mass. 12 These data support the investigators’ understanding that varying forces available via different settings on the exercise hardware is important for evaluating the effectiveness of exercise countermeasures against bone and muscle loss. By working with the operational team that defines the exercise protocols for crewmembers on orbit, the experimental runs performed by the next three subjects yielded information not only on daily activity, but also on the force capabilities of the exercise hardware currently on the ISS. Further analyses are ongoing, but the research results are expected to significantly change exercise prescriptions for subsequent ISS crewmembers, as well as influence designs for future exercise hardware. Two important lessons learned from operating exercise equipment on the ISS to date are 1) hardware should be designed for modular upgrades to accommodate changing exercise prescriptions, and 2) exercise equipment designed for shorter missions has been less reliable with months and years of heavy use on the ISS. For example, the IRED hardware was designed to provide up to 136 kg (300 lbs) of force for resistive exercise. However, before it was deployed, research had shown that 272 kg (600 lbs) of force was required for exercise prescriptions to minimize bone and muscle loss. Provisions were made to augment forces using bungees, but their use complicates set-up and operations. In addition, the rotary elastomeric springs which provide the resistive force in IRED and the cords that transferred the force to the harnesses and handles used by crewmembers proved to have a more limited life than was originally intended. This necessitated complex in-flight maintenance procedures to replace parts reaching the end of their life. The TVIS system proved even more problematic over the past six years of the ISS operation. The first problem was with the running surface itself. The treadmill portion of TVIS uses a unique running surface called a Uniflex Belt. It consists of rigid slats fastened to a flexible substrate in such a way that it bends easily in one direction but does not bend in the other direction. This design was chosen for two reasons: 1) lower friction than the design used in most commercial treadmills, and 2) the additional mass in the belt provides much higher inertia, which helps to minimize motor speed variations with foot strikes, thus reducing current peak demands. Unanticipated problems with fatigue life in the plastic material used to make the belt slats resulted in the need for crewmembers in Expedition 2 to completely replace the running surface with aluminum slats. Subsequently, a problem was encountered with bearings in the chassis structure that supports the Uniflex belt. This necessitated another series of complex maintenance procedures; initially to temporarily remove faulty bearings, and later to replace the entire support structure inside the chassis. Another problematic element has been the Subject Load Device (SLD) system, which use adjustable springs to apply a restraint force approximating the crewmember’s body weight on Earth. The NASA-provided SLD system was designed to accommodate walking and running; however, the Russian Federal Space Agency (FSA) treadmill exercise protocols also include knee bends, squats, and other exercises. While modifications were attempted to provide the range of travel and linearity of load force over the range of travel that Russian physiologists desired, the results were less than satisfactory. Furthermore, there are reliability problems with the steel cables and pulleys used to connect the SLD to the harness worn by the crewmembers, and with the harness itself, which most find uncomfortable. Specialists are still struggling with how to overcome the challenge of designing items on Earth for use in space, especially when they can only be tested in long-term microgravity environments. Over the years some of the electronic elements of the TVIS have also had to be replaced, which has presented the challenge of how to calibrate integrated systems on-orbit when only pieces are being replaced. Elements of the vibration isolation and stabilization (VIS) system have also needed repairs – the wire rope isolators have limited life, and stabilizer and gyroscope modules have experienced failures. Flight planners now schedule routine inspections of all TVIS chassis elements on a monthly basis, and plans are made to periodically replace the entire TVIS chassis. The next generation of exercise devices are now being developed to incorporate lessons learned and provide improved exercise capabilities. Work is also underway to improve the harness designs that transfer the forces onto the human body for IRED and TVIS12. The ISS provides an important opportunity for long-duration testing of the 5 American Institute of Aeronautics and Astronautics

next generation of exercise technology, and for validation of the role of exercise combined with other countermeasures in protecting against bone and muscle loss so that future crewmembers will reach their destinations strong and ready to explore.

III. Materials in Space The space environment poses many hazards to spacecraft, including intense ultraviolet radiation, corrosive attacks from atomic oxygen, radical temperature swings, micrometeoroid strikes and orbital debris. To ensure future spacecraft can handle the rigors of long-duration space flight, NASA studies the exposure of materials to the space environment. A. Materials Testing on the International Space Station To travel on long duration missions materials which can withstand the rigors of space flight must be used in the development of future spacecraft. The Materials International Space Station Experiment (MISSE) functions as a testbed for several hundred materials and coatings samples, testing their survivability under the corrosive effects of the space environment; including micrometeoroid and orbital debris strikes, atomic oxygen attack, intense ultraviolet radiation from the sun, charged particle radiation, and extreme temperature swings. Results will provide a better understanding of the durability of various materials in this environment. The MISSE (William H. Kinard, Langley Research Center, Hampton, VA, and Robert Walters, Naval Research Laboratory, Washington, DC) consists of a series of carriers mounted externally on the ISS to test the durability of a wide range of materials and devices exposed to the space environment that are used in both human spacecraft and in unmanned vehicles. For example, white and colored coating materials produced by two companies (AZ Technology, Huntsville, AL and Alion Science, McLean, VA) are under consideration for use on the Crew Exploration Vehicle and Crew Launch Vehicle (CEV/CLV); samples of these materials flew on MISSE-1 and 2 and MISSE5, are currently on orbit as part of MISSE-3 and 4, and will also be tested as part of MISSE-6. Besides being used in thermal control, electrically conductive versions of the white coatings are used to dissipate static electricity on spacecraft. These materials are also used in making docking targets as well as in the printing of various logos. Return of the coating samples allows evaluation of the long-term stability of the coatings, their adhesion to the substrate, and comparisons of new formulations with previous standards. Samples flown as part of MISSE-1 and 2 were mounted outside the ISS for 4 years, were retrieved during STS-114 and are now providing important insight into the observed changes in Figure 3. MISSE deployed on the exterior materials on some areas of the ISS. For some spacecraft International Space Station. From top to materials, such as polyimide Kapton used in solar array blankets, bottom: MISSE-4 following deployment on a layer of aluminum or silicon dioxide is coated onto the Kapton the outside of ISS on August 3, 2006 to provide protection from degradation by atomic oxygen. (ISS013E63396). Oblique view of MISSE Investigators from Glenn Research Center (Bruce A. Banks, with Earth and space background Sharon K. Miller, and Aaron Snyder) have documented (ISS005E17107). accelerated degradation in materials that have protective layers on both sides of the Kapton. 13 When both the top and bottom surfaces of the Kapton are aluminized and a molecule of atomic oxygen gets in through a small defect on the spaceexposed side, the oxygen atom is trapped bouncing around inside until it reacts causing oxidation or until it leaves the entrance hole. 14 The result is the growth of a cavity in a process called undercutting. In the undercutting process, the aluminum or silicon dioxide coating can be left free-standing and then may be released and contaminate other areas of the spacecraft. By using Kapton that is only protected from atomic oxygen on the outside, the atomic oxygen is less trapped and there is much less undercutting degradation. Observations of degradation of the MISSE samples show the improvement when there is a single protective layer, and the performance of alternative protective 6 American Institute of Aeronautics and Astronautics

coatings for the Kapton such as a layer of silicon dioxide. One set of samples flown on MISSE-2 allows measurement of the pattern of atomic oxygen undercutting through controlled simulated defects in a protective silicon dioxide layer.13 The results are important to the materials selection for solar arrays on the ISS, satellites, and future spacecraft. Another Glenn Research Center MISSE-2 experiment called the Polymer Erosion and Contamination Experiment (PEACE, Kim K. de Groh and Bruce A. Banks collaborating with students from Hathaway Brown School) has documented long-duration low Earth orbit atomic oxygen erosion yield data (Ey, the volume loss per incident oxygen atom, cm3/atom) for 41 different polymers, the widest variety of polymers ever tested in space. 15 This MISSE-2 data is being used to allow proper selection of materials and thickness for future longduration space flight missions. The MISSE-2 data is also being used to develop a predictive tool for atomic oxygen erosion prediction of new polymers without requiring flight testing. MISSE-5, launched during the STS-114 was retrieved in September 2006 during the STS-115 mission after 13 months of space exposure. MISSE-5 contains three investigations. The Forward Technology Solar Cell Experiment (FTSCE), designed to test the performance of 36 current and advanced generation solar cells for use on future spacecraft. The Second Prototype Communication Satellite System (PCSat-2), which provided a communications system and tested the Amateur Satellite Service off-the-shelf solution for telemetry command and control. Both the FTSCE and PCSat-2 are active experiments; the third experiment, the MISSE-5 Thermal Blanket Materials Experiment, was a passive experiment designed to evaluate the Figure 4. MISSE-5. Post-flight examination of degradation of more than 200 materials in the space MISSE-5 at the Naval Research Laboratory, environment. Post-flight analyses are currently being Washington, DC. conducted on the retrieved MISSE-5 experiments. MISSE-6, the next in the MISSE series, will test three types of elastomer materials to decide what will be used to create the seals (O-rings) for the CEV Advanced Docking and Berthing System/Low Impact Docking System, in addition to many other samples. Some of the seals will be exposed to the space environment while others will be shielded. The exposed seals will experience radiation, atomic oxygen, micrometeoroids, temperature and vacuum effects; whereas the shielded seals will only experience the temperature and vacuum effects. Another seal that will be tested is shielded with a metallic coating to determine if this approach will protect it from radiation and atomic oxygen damage. The results of the exposure will help engineers select the best performing material. B. Stability of Nutrients and Pharmaceuticals Stability of materials in the space environment is not only important for construction of vehicles, but also for the health of the crew. Data gathered from past Space Shuttle missions suggests that pharmaceuticals tested exhibited significant degradation even after relatively brief periods of space flight. 16 The effects observed included decreases in physical stability and chemical content of drug formulations of sufficient magnitude resulting in a failure to meet shelf-life requirements stipulated by the Food and Drug Administration (FDA). Physical or chemical instability of foods and pharmaceuticals could render the products less effective or ineffective in maintaining adequate health or providing desired efficacy of treatment for crewmembers during space missions. The stability of pharmaceuticals and foods used daily by the crew must be protected from degradation and improved to ensure the health of crewmembers during long-duration missions. Many nutrients (e.g., vitamins, amino acids, fatty acids) have complex chemical structures, similar to pharmaceuticals. Assessment of nutritional status in the ISS crewmembers has shown changes which cannot be explained on the basis of the expected food content of these nutrients16. If the space environment, most likely related to radiation, is altering the nutrient content of foods on the ISS, this could have a devastating impact on extended space missions. The stability of pharmaceuticals and foods used daily by the crew must be maintained to ensure safe exploration in the future. The Stability of Pharmacotherapeutic and Nutritional Compounds (Stability, Scott M. Smith, and Lakshmi Putcha, NASA Johnson Space Center, Houston, TX) investigation will further 7 American Institute of Aeronautics and Astronautics

evaluate space foods and pharmaceutical formulations to determine the effects of extended storage on the ISS. Past studies have indicated that eight percent of all drug treatments during space flight on Space Shuttle missions were reported as ineffective. Pharmaceutical instability may modify effectiveness and safety, and may contribute to treatment failure in space. As a part of the Stability investigation, several identical packages of pharmaceuticals and foods are passively exposed to the internal ISS environment. The packages will be returned following approximately 0.5, 6, 12 and 18-months of exposure. This experiment is quantifying the stability of key nutrients and pharmaceuticals compared to matched items stored in controlled environments on the ground. Although the food system is normally considered an operational system, this applied work is likely to transform our understanding of the effect of the space environment on foods and medicines. This study is expected to provide important insight into the stability of antibiotics, antihistamines, and other pharmaceuticals in addition to vitamin content in pre-packed space foods16. Knowing the time course of effects of radiation and temperature Figure 5. Scientists at Johnson Space Center in will facilitate a new directive for the development of Houston, TX. Analyzing the Stability samples food and food storage systems for future space vehicles returned on STS-121. The Stability experiment is the and selection of medications that will help to protect the first experiment as part of the new integrated ISS health of the crews on the ISS and on future exploration Medical Project (ISSMP). missions.

IV. In Space Repair For future crews on long-duration missions, repairing onboard equipment may be critical to mission success, but conducting repairs in space can be challenging. Performing repairs in the ISS’s microgravity aboard the ISS will help to develop an understanding of repair processes in space so that when such repair capabilities are needed in the future, we will have the knowledge and experience to perform them and help keep vital systems operating for exploration. A. Repairing Non-functional Research Hardware in Orbit On the ISS, the original maintenance and repair concept was only to replace major assemblies known as Orbital Replacement Units (ORUs), but this soon evolved to include removal and replacement of smaller sub-assemblies such as circuit cards when possible because of limitations in the available mass and volume that could be delivered to orbit (upmass). The next step to reduce the size of the items being replaced is component-level repair, with soldering as an important technique. However, previous studies have indicated that soldering in space is significantly different from the same process on Earth. 17 One example of unplanned on-orbit repair of research hardware involved a middeck-locker sized thermoelectric incubator/refrigerator/freezer called ARCTIC™ (Oceaneering International, Houston, TX). The ARCTIC™ was designed to operate as an incubator Figure 6. ARCTIC™ Repair on ISS. Shows the (providing temperatures up to +37°C) or as a refrigerator disassembled ARCTIC-1 unit. The inset images are or freezer (providing temperatures as low as -25°C) the corroded thermoelectric elements within the aboard the ISS. Cooling was accomplished via ARCTIC™ (ISS006E46793, ISS006E46757, thermoelectric elements with heat rejection either into ISS006E46308). the avionics air system or the moderate temperature cooling loop (water) in the EXpedite the PRocessing of 8 American Institute of Aeronautics and Astronautics

Experiments to Space Station (ExPRESS) racks onboard the ISS. Two ARCTIC units were delivered to the ISS to support biological research experiments in 2002. ARCTIC-1 operated as a freezer with a set temperature -25°C, while ARCTIC-2 operated in refrigerator mode at +4°C. The two ARCTIC™ units operated continuously for a combined total of 6,870 hours during Expeditions 4 and 5, supporting several investigations, before both units experienced failures in the thermoelectric heat exchangers and lost the ability to cool. One unit was returned to Earth for detailed failure analysis, while the other remained on orbit. The ground-based investigation revealed that moisture incursion into the heat exchanger element (which was thought to be hermetically sealed) caused corrosion of the electrical connections on the Peltier thermoelectric elements. Eventually, the corrosion became severe enough to break connections, rendering the heat exchanger nonfunctional. 18 While these units were not designed for on-orbit repair, it was decided that due to the delay in the launch of a much larger freezer following the Columbia accident, an unprecedented effort would be made to salvage the one remaining unit. A team of specialists on the ground developed an elaborate yet flexible in-flight maintenance repair procedure that allowed the crewmember an unprecedented amount of freedom to use his own judgment on the steps to be taken. The procedure used only tools and materials available on-orbit, and depended on an on-board crewmember’s considerable electronics skills and experience in his home workshop. The team broke new ground in procedures development, deviating from the conventional format for NASA on-board flight procedures in favor of an approach resembling commercially available automobile repair manuals (it was dubbed by the team the “Chilton’s Manual” format). In addition, the traditional procedures validation process (wherein procedures are validated using flight-like hardware) had to be omitted since there was no hardware available on the ground to work with (the other ARCTIC™ unit had been completely disassembled during the failure investigation process). Payload operators and Flight Directors allowed ARCTIC™ engineers unprecedented opportunities to communicate with the crewmembers on-orbit. Instead of passing information and answers to crewmember questions through flight controllers to the CapCom (astronaut acting as the spacecraft communicator) for relay to the crewmember, the engineers were able to use the S/G loops to speak directly with the crewmember performing the repair. This greatly improved communications and reduced the chance of communications errors inherent when messages are relayed.18 The six-stage repair process involved removal of 150 fasteners and small parts; disassembly of system components, including removal of insulation; removal of corrosion that had precipitated the failure in the first place; testing of individual Peltier elements to determine which were still functional after cleaning; repair of the heat pump, which involved very complex soldering techniques to re-connect the functional Peltier coolers and bypass bad ones; testing and rewiring of the repaired freezer components; reassembly of the heat pump; installation of the heat pump in the freezer and testing of fluid lines for leaks; reassembly of the freezer housing; and finally testing of the repaired freezer. Of particular note is the fact that the crewmember had to create new solder pads (contacts) on some of the Peltier elements to allow wires to be connected where corrosion had ruined the original contacts. While the corrosion had damaged the unit to the point that the thermoelectric elements failed again after about 24-hours of operation, the fact that it operated at all was remarkable in view of the amount of damage observed in the heat exchanger. Engineers and technicians who saw the photographs of the damaged heat exchanger and the repairs that were made observed that the tasks performed would have been difficult for experienced technicians working in a well-equipped repair shop on Earth. The repair demonstrated the ability of a crewmember with the appropriate skills to perform complex repairs on hardware that was not designed to be serviced in-flight.18 B. Soldering Tests in Microgravity Soldering is an important general technique that may be needed for repair of spacecraft either in orbit or on the way to the moon or Mars. On Earth, soldering depends on gravity and convection for proper solidification, joint shape, joint integrity and microstructure. Some detrimental gas bubbles or void spaces form in the solder joint at contact surfaces. These voids reduce the thermal and electrical conductivity as well as provide sites for crack initiation. In the reduced gravity environment on orbit, bubbles have less chance to escape and weaker joints are more of a problem than on Earth.19 The objective of In Space Soldering Investigation (ISSI, Richard Grugel, NASA Marshall Space Flight Center, Huntsville, AL) was to examine how solder flows in space without the presence of convection and other gravitational forces and to assess the quality

Figure 7. ISSI operations on ISS. ISS Science Officer Mike Fincke, using a soldering iron to perform ISSI operations during Expedition 9.

9 American Institute of Aeronautics and Astronautics

and strength of solder joints formed in space. Soldering tests were done on metal alloy wires of various configurations designed to evaluate the effectiveness of different geometries typical of the kinds of operations that might be required during future long-duration space flights. Samples have now been returned to Earth and are undergoing analysis. The ISSI helped develop our understanding of soldering processes in space so that when such repair capabilities are needed, we will have the knowledge and experience to perform them. 19 Samples from ISSI and the ARCTIC™ repair are now being analyzed to determine the structure of the materials and identify better soldering techniques. C. Repairing Environmental Systems To successfully live and work in the environment of space, the ISS environment must be monitored to ensure the health of the crew living and working there. Effects of pollutants are magnified on the ISS because the crew exposure is continuous. Sources of physical, chemical, and microbiological contaminants include humans and other organisms, food, cabin surface materials, and experiment devices. One hazard is the off-gassing of vapors from plastics and other items on the ISS; although this is a small hazard, the accumulation of these contaminants in the air can prove dangerous to crew health. The Volatile Organic Analyzer (VOA, NASA Johnson Space Center, Houston, TX) is an atmospheric analysis device on the ISS that detects, identifies, and quantifies a selected list of volatile organic compounds (e.g. ethanol, methanol and 2-propanol) that are harmful to humans at high levels in a closed environment, such as the ISS. Operational experience in on-orbit component repair has now also been applied to the disabled VOA, which was successfully repaired on-orbit. The VOA utilizes gas chromatography to separate compound mixtures in a preFigure 8. In-flight repair concentrated sample and then identifies the specific compounds by ion-mobility of the VOA. Astronaut mass spectrometry. Since its installation in 2001, the VOA has successfully William McArthur Jr., quantified the concentration levels for volatile compounds in the ISS. However Expedition 12 commander two blown thermal fuses in 2005 rendered the VOA inoperable. A diagnostic and NASA space station procedure was developed on ground and then performed on orbit which confirmed science officer, performs that the thermal fuses on both the channels were prematurely opened. Although the in-flight maintenance on thermal fuses were rated correctly for the design, data on the fuses confirmed that the Volatile Organic sustained operation at near fuse set-point temperatures will compromised the life Analyzer in the Destiny of the fuses, causing the fuses to open prematurely due to degradation of its laboratory of the ISS internal components. Once the fuse opens, the use of that circuit is lost; any open (ISS012E10245). circuit results in the loss of at least one complete channel on the VOA 20. Once the root cause was identified, a three-day in-flight maintenance procedure was performed on the VOA in December 2005 which successfully replaced four thermal fuses and all planned onorbit maintenance items20. Since the repair in December 2005, the VOA has performed over 40 sample analyses of volatile organic compounds, and 60 calibration runs on the ISS. Recently, a new fault has rendered the VOA to operate on one channel only. Currently a diagnostic activity is being planned for 2007.

VI. Conclusions Through synergies between many groups supporting the ISS, NASA is achieving it’s objectives for the Vision. The examples of cooperation between research, operations, and engineering discussed in this paper have led to increased knowledge for successful completion of long-duration human space missions. Research to counteract the harmful effects of space flight on human health is being achieved by cooperation between medical researchers and medical operators as well as engineers. The MISSE is testing new space technologies that will be used in future spacecraft; the Stability investigation is verifying the potency of food and medicines to maintain crew health during exploration. NASA is learning how to operate long-duration space missions through daily interaction with the ISS and is learning to perform more complex repairs of items in space that had been attempted before. These ISS synergies have laid the groundwork for future space exploration by humans. We have provided examples of synergies between research, operations, and engineering that have led to increased knowledge for successful completion of long-duration human space missions. The synergies between those that maintain and operate the ISS and those that use it as a research platform are laying the groundwork for future human space exploration beyond low Earth orbit. 21 10 American Institute of Aeronautics and Astronautics

Acknowledgments We would like to thank the many ISS investigators and operators whom discussed their experiments, operations and provided preliminary results. We would also like to thank Mick Culp, ISS Payloads Office for his editorial comments and Frances Brown, Engineering Science Contract Group, NASA Johnson Space Center, Houston, TX for her work in creating diagrams for this paper.

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