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At least 343 records · Page 19

Toolkits Control Motion of Complex Robotics

That space is a hazardous environment for humans is common knowledge. Even beyond the obvious lack of air and gravity, the extreme temperatures and exposure to radiation make the human exploration of space a complicated and risky endeavor. The conditions of space and the space suits required to conduct extravehicular activities add layers of difficulty and danger even to tasks that would be simple on Earth (tightening a bolt, for example). For these reasons, the ability to scout distant celestial bodies and perform maintenance and construction in space without direct human involvement offers significant appeal. NASA has repeatedly turned to complex robotics for solutions to extend human presence deep into space at reduced risk and cost and to enhance space operations in low Earth orbit. At Johnson Space Center, engineers explore the potential applications of dexterous robots capable of performing tasks like those of an astronaut during extravehicular activities and even additional ones too delicate or dangerous for human participation. Johnson's Dexterous Robotics Laboratory experiments with a wide spectrum of robot manipulators, such as the Mitsubishi PA-10 and the Robotics Research K-1207i robotic arms. To simplify and enhance the use of these robotic systems, Johnson researchers sought generic control methods that could work effectively across every system.

Source record↗

Desert Research and Technology Studies 2008 Report

During the last two weeks of October 2008, the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) Advanced Extravehicular Activity (AEVA) team led the field test portion of the 2008 Desert Research and Technology Studies (D-RATS) near Flagstaff, AZ. The Desert RATS field test activity is the year-long culmination of various individual science and advanced engineering discipline areas technology and operations development efforts into a coordinated field test demonstration under representative (analog) planetary surface terrain conditions. The 2008 Desert RATS was the eleventh RATS field test and was the most focused and successful test to date with participants from six NASA field centers, three research organizations, one university, and one other government agency. The main test objective was to collect Unpressurized Rover (UPR) and Lunar Electric Rover (LER) engineering performance and human factors metrics while under extended periods of representative mission-based scenario test operations involving long drive distances, night-time driving, Extravehicular Activity (EVA) operations, and overnight campover periods. The test was extremely successful with all teams meeting the primary test objective. This paper summarizes Desert RATS 2008 test hardware, detailed test objectives, test operations, and test results.

Romig, Barbara↗

Vascular uptake of rehydration fluids in hypohydrated men at rest and exercise

The purpose of this study was to formulate and to evaluate rehydration drinks, which would restore total body water and plasma volume (PV), for astronauts to consume before and during extravehicular activity, a few hours before reentry, and immediately after landing. In the first experiment (rest, sitting), five healthy men (23-41 yr), previously dehydrated for 24 hr., drank six (1a, 2, 4, 5, 6, 7) fluid formulations (one each at weekly intervals) and then sat for 70 min. Pre-test PV were measured with Evans blue dye and changes in PV were calculated with the hematocrit-hemoglobin transformation equation. This rest experiment simulated hypohydrated astronauts preparing for reentry. The second experiment (exercise, supine) followed the same protocol except four healthy men (30-46 yr) worked for 70 min. in the supine position on a cycle ergometer at a mean load of 71+/-1 percent of their peak aerobic work capacity. This exercise experiment simulated conditions for astronauts with reduced total body water engaging in extravehicular activity.

Greenleaf, J. E.↗

Prediction of muscle performance during dynamic repetitive movement

BACKGROUND: During long-duration spaceflight, astronauts experience progressive muscle atrophy and often perform strenuous extravehicular activities. Post-flight, there is a lengthy recovery period with an increased risk for injury. Currently, there is a critical need for an enabling tool to optimize muscle performance and to minimize the risk of injury to astronauts while on-orbit and during post-flight recovery. Consequently, these studies were performed to develop a method to address this need. METHODS: Eight test subjects performed a repetitive dynamic exercise to failure at 65% of their upper torso weight using a Lordex spinal machine. Surface electromyography (SEMG) data was collected from the erector spinae back muscle. The SEMG data was evaluated using a 5th order autoregressive (AR) model and linear regression analysis. RESULTS: The best predictor found was an AR parameter, the mean average magnitude of AR poles, with r = 0.75 and p = 0.03. This parameter can predict performance to failure as early as the second repetition of the exercise. CONCLUSION: A method for predicting human muscle performance early during dynamic repetitive exercise was developed. The capability to predict performance to failure has many potential applications to the space program including evaluating countermeasure effectiveness on-orbit, optimizing post-flight recovery, and potential future real-time monitoring capability during extravehicular activity.

Physical Endurance/physiology↗

Extravehicular mobility unit training and astronaut injuries

BACKGROUND: Astronaut spacewalk training can result in a variety of symptom complaints and possible injuries. This study quantified and characterized signs, symptoms, and injuries resulting from extravehicular activity spacesuit training at NASA's Neutral Buoyancy Laboratory, Johnson Space Center, Houston, TX, immersion facility. METHODS: We identified the frequency and incidence of symptoms by location, mechanisms of injury, and effective countermeasures. Recommendations were made to improve injury prevention, astronaut training, test preparation, and training hardware. At the end of each test, a questionnaire was completed documenting signs and symptoms, mechanisms of injury, and countermeasures. RESULTS: Of the 770 tests, there were 190 in which suit symptoms were reported (24.6%). There were a total of 352 reported suit symptom comments. Of those symptoms, 166 were in the hands (47.16%), 73 were in the shoulders (20.7%), and 40 were in the feet (11.4%). Others ranged from 6.0% to 0.28%, respectively, from the legs, arms, neck, trunk, groin, and head. Causal mechanisms for the hands included moisture and hard glove contacts resulting in fingernail injuries; in the shoulders, hard contact with suit components and strain mechanisms; and in the feet, hard boot contact. The severity of symptoms was highest in the shoulders, hands, and feet. CONCLUSIONS: Most signs and symptoms were mild, self-limited, of brief duration, and were well controlled by available countermeasures. Some represented the potential for significant injury with consequences affecting astronaut health and performance. Correction of extravehicular activity training-related injuries requires a multidisciplinary approach to improve prevention, medical intervention, astronaut training, test planning, and suit engineering.

Non-programmatic↗

Space Tools for Servicing, Repairing, and Maintaining Spacecraft

Just like mechanics and technicians on Earth, astronauts use a variety of manual and portable power tools in space to repair, service, and maintain spacecraft, like the Space Shuttle and the International Space Station (ISS), and other satellites, like the Hubble Space Telescope (HST). Space tools are divided into two main operating categories: Intravehicular Activity (IVA) tools and Extravehicular Activity (EVA) tools. N A tools are used by astronauts inside the pressurized habitable compartments of a spacecraft for routine maintenance, repair, and unexpected tasks. EVA tools are used by space-suited astronauts outside of their pressurized spacecraft in the vacuum of space.

Trevino, Robert C.↗

Characterization of Rapid Charging Events Due to Sheath Capacitance and Impact on the International Space Station Plasma Hazard Process

During an Extravehicular Activity (EVA), if the Extravehicular Mobility Unit (EMU) makes galvanic contact with the International Space Station (ISS), a negative Floating Potential (FP) can lead to an arcing hazard when it exceeds -45.5 V, and a positive FP can produce a DC current high enough to stimulate the astronaut’s muscles (5 mA), and also cause a hazard. The Boeing Space Environments team developed and utilizes a Plasma Interaction Model (PIM) in order to calculate the ISS FP based on the plasma environment, ISS velocity, geomagnetic field, solar array and ISS orientation, and solar array regulation to support EVA planning operations. Presently, the model excludes the sheath capacitance, resulting in the total potential drop being across the dielectric surface of the vehicle. Data from the Floating Potential Measurement Unit (FPMU) show this assumption to be generally true. However, Rapid Charging Events (RCE) are often observed in the FPMU data at eclipse exit when the electron number density, Ne, is low (less than 5(sub e)10 m (exp-3)). During these events, the FP can rise more than 40 V in one to five seconds. There is then a relaxation phase where the FP drops back to the normal FP values. The PIM model is not capable of producing these RCEs. It was thought that the inclusion of the sheath in PIM could improve the charging predictions, particularly as related to RCEs. A parametric study was performed to determine what portion of the measured FP is across the sheath for a range of Ne experienced by the ISS, and if the inclusion of the sheath in PIM is necessary. Results show that the potential drop across the sheath is negligible at times when the N(sub e) is greater than 1(sub e)11 m-3. However, there appears to be a transitional region between 1(sub e)10 m(exp -3) and 1(sub e)11 m(exp -3) where the sheath capacitance becomes more significant. During those conditions the potential drop across the sheath can be larger than the potential drop across the dielectric for short periods (1-5 seconds). These results agree remarkably well with measurements made by the FPMU. The inclusion of the sheath explains why high charging measurements occur when the Ne is low at eclipse exit and even times when the solar arrays are not a significant driver (i.e., potentials often rise as the ISS flies through spread-F). Results also show that the RCEs are not a safety concern because the potential drop across the dielectric surface does not exceed -45.5 V. In that case, the EMU would not arc. This gives high confidence in the low probability of an arcing hazard occurring.

plasma environment↗

Advanced Technology Infusion into Spacesuit Systems

Advancement in technology drives our future. The successful implementation of a technology drives its possibilities. The National Aeronautics and Space Administration (NASA) has invested in numerous technologies that have proved to be successful. The desire is to learn from those successes. For a technology to evolve, become a reality, and infuse into NASA’s missions, a compilation of success-oriented factors must exist for the technology to reach fruition. Understanding these factors could help decrease the complexity of technology infusion and bridge the gap between technology developers and system integrators. The knowledge gained could facilitate the design, development, test, and infusion of a technology to be more effective and efficient. Successful technology infusion is complex and can be even more daunting when advanced technologies are infused into complicated systems. NASA, industry, and academia desire to understand the infusion process, along with measuring the success of infusing an advanced technology into a complex system. This paper focuses on complicated systems that necessitate successful infusion of technologies. These systems include NASA’s spacesuits used for extravehicular activity, including the Apollo Extravehicular Mobility Unit (EMU), the Shuttle/International Space Station EMU, and the Exploration EMU (xEMU) architectures. Several life support technologies will be addressed in the xEMU. Those technologies will be discussed, along with a methodology for assessing infusion pathways. The infusion pathways of these life support technologies into spacesuit architectures can form the benchmark for technology infusion into other architectures for lunar and Martian surfaces. The spacesuit system architectures as case studies can provide the foundation of technical knowledge to help NASA and industry’s project managers and system managers integrate advanced technologies more effectively and efficiently.

Cinda Chullen↗

Radiation protection for manned space activities

The Earth's natural radiation environment poses a hazard to manned space activities directly through biological effects and indirectly through effects on materials and electronics. The following standard practices are indicated that address: (1) environment models for all radiation species including uncertainties and temporal variations; (2) upper bound and nominal quality factors for biological radiation effects that include dose, dose rate, critical organ, and linear energy transfer variations; (3) particle transport and shielding methodology including system and man modeling and uncertainty analysis; (4) mission planning that includes active dosimetry, minimizes exposure during extravehicular activities, subjects every mission to a radiation review, and specifies operational procedures for forecasting, recognizing, and dealing with large solar flaes.

Jordan, T. M.↗

Spaceborne construction and operations planning - Decision rules for selecting EVA, telerobot, and combined work-systems

An approach is presented for selecting an appropriate work-system for performing construction and operations tasks by humans and telerobots. The decision to use extravehicular activity (EVA) performed by astronauts, extravehicular robotics (EVR), or a combination of EVA and EVR is determined by the ratio of the marginal costs of EVA, EVR, and IVA. The approach proposed here is useful for examining cost trade-offs between tasks and performing trade studies of task improvement techniques (human or telerobotic).

Smith, Jeffrey H.↗

Evaluation of Thermoregulation After Spaceflight

Altered thermoregulation has been reported following spaceflight simulations such as water immersion and bedrest but it has never been evaluated immediately after actual spaceflight. Impaired thermoregulation may have significant impact during various spaceflight activities such as countermeasure exercise, extravehicular activity (EVA), landing, and egress. It would be manifested as an increased body temperature and heart rate and decreased work capacity and endurance. In this study we evaluated the exercise responses of two crewmembers following a long duration spaceflight and measured their changes in body temperatures, skin blood flow, sweating and heat production during a mild submaximal exercise stress.

Schneider, S. M.↗

STS-110 Post Flight Presentation

The crewmembers of STS-110 (Michael Bloomfield, Commander; Stephen Frick, Pilot; Mission Specialists Ellen Ochoa, Jerry Ross, Rex Walheim, Steve Smith and Lee Morin) narrate this video as footage from the mission is seen, starting with crew suit up, and launch of Atlantis. Various on-orbit activities are shown, including the opening of the payload bay doors, the rendezvous and docking of Atlantis with the International Space Station (ISS). Crew activities shown include loading operations, extravehicular activities (EVAs), robot arm operation and crew living conditions. Specific EVAs footage includes the unloading of the S0 truss from the Atlantis payload bay and installation onto the ISS. The crew is also shown preparing the Mobile Transporter for future use. The video ends with Atlantis undocking from the ISS and landing at Kennedy Space Center.

Source record↗

Refinement of Optimal Work Envelope for Extra-Vehicular Activity (EVA) Suit Operations

The purpose of the Extravehicular Mobility Unit (EMU) Work Envelope study is to determine and revise the work envelope defined in NSTS 07700 "System Description and Design Data - Extravehicular Activities" [1], arising from an action item as a result of the Shoulder Injury Tiger Team findings. The aim of this study is to determine a common work envelope that will encompass a majority of the crew population while minimizing the possibility of shoulder and upper arm injuries. There will be approximately two phases of testing: arm sweep analysis to be performed in the Anthropometry and Biomechanics Facility (ABF), and torso lean testing to be performed on the Precision Air Bearing Facility (PABF). NSTS 07700 defines the preferred work envelope arm reach in terms of maximum reach, and defines the preferred work envelope torso flexibility of a crewmember to be a net 45 degree backwards lean [1]. This test served two functions: to investigate the validity of the standard discussed in NSTS 07700, and to provide recommendations to update this standard if necessary.

Jaramillo, Marcos A.↗

Micrometeoroid and Orbital Debris (MMOD) Testing, Ballistic Limit Definition and Risk Assessment of the Exploration Extravehicular Mobility Unit (xEMU)

A well-known hazard associated with exposure to the space environment is the risk of failure due to an impact from a micrometeoroid and orbital debris (MMOD) particle. As NASA prepares to return astronauts to the moon with the Artemis program, the next generation of spacesuit is in development to support future extravehicular activities (EVAs.) An MMOD impact to the spacesuit is of great concern as a large leak could prevent an astronaut from safely reaching an airlock in time resulting in a loss of life. The exploration extravehicular mobility unit (xEMU) must meet MMOD requirements for multiple environments including those in low earth orbit (LEO) as well as the meteoroid and secondary lunar regolith ejecta environments found on the lunar surface. The subject of this paper is an internal xEMU configuration design developed by NASA Johnson Space Center (JSC) personnel. The xEMU shares similarities with the legacy Extravehicular Mobility Unit (EMU) spacesuit that is currently used for ISS EVAs, however differences in the layup (e.g., materials, thicknesses, and layers) of the fabric environmental protection garment (EPG), portable life support system (xPLSS) and helmet required an extensive test program to determine ballistic performance. Over 100 hypervelocity impact (HVI) tests were performed by the NASA/JSC HVIT and White Sands Test Facility (WSTF) teams on the xEMU EPG, xPLSS and helmet to generate ballistic limit equations (BLEs) for MMOD impacts. Additionally, over 50 low speed tests (< 1km/s) were performed by the NASA/JSC HVIT and Southwest Research Institute (SwRI) teams on the xEMU EPG, xPLSS and helmet to generate BLEs for lunar ejecta impacts. Post testing, ballistic limit equations (BLEs) used to define the performance of the various regions on the xEMU spacesuit were developed from a generic set of BLEs. The HVI and low speed testing was performed to establish a physical basis for the equations with the coefficients and exponents of the generic BLEs adjusted to fit the test data. The xEMU BLEs were added to the NASA/JSC software application used for spacecraft MMOD risk assessments (BUMPER-3). A finite element model (FEM) of the xEMU spacesuit, which defines the size and shape of the spacesuit as well as the locations of the various shielding configurations, was created based on a solid model provided by the xEMU program office. Using the FEM file and added xEMU BLEs, BUMPER-3 assessments of the xEMU spacesuit for probability of no penetration (PNP) were performed. For the LEO assessment of a typical ISS EVA, the orbital debris and meteoroids environments were defined using the latest engineering models, ORDEM 3.2 and MEM-3 respectively. The lunar surface assessment again used the MEM-3 engineering model to define the meteoroid environment along with the current released lunar surface ejecta model, NASA SP-8013 (developed during the Apollo Program). The Space Team in the Natural Environments Branch at Marshall Space Flight Center (MSFC) will soon release the new Lunar Meteoroid Ejecta Engineering Model (LMEEM), at which time the xEMU lunar surface EVA will be reassessed. Assessment of the MMOD risk for an 8-hour, 2-person EVA in both LEO and on the lunar surface showed that the xEMU spacesuit meets the program technical requirement of 1 in 2500 failure odds. Similar to the legacy EMU spacesuit, the majority of the MMOD risk (96% of the LEO EVA risk and 99% of the lunar surface EVA risk) is concentrated in regions of xEMU that are comprised primarily of softgoods (arms, legs, and gloves) rather than the hardgoods (xPLSS, hard upper torso and helmet).

Micrometeoroid↗

Micrometeoroid and Orbital Debris (MMOD) Testing, Ballistic Limit Equation Definition and Risk Assessment of the Exploration Extravehicular Mobility Unit (xEMU)

A well-known hazard associated with exposure to the space environment is the risk of failure due to an impact from a micrometeoroid and orbital debris (MMOD) particle. As NASA prepares to return astronauts to the moon with the Artemis program, the next generation of spacesuit is in development to support future extravehicular activities (EVAs.) An MMOD impact to the spacesuit is of great concern as a large leak could prevent an astronaut from safely reaching an airlock in time resulting in a loss of life. The exploration extravehicular mobility unit (xEMU) must meet MMOD requirements for multiple environments including those in low earth orbit (LEO) as well as the meteoroid and secondary lunar regolith ejecta environments found on the lunar surface. The subject of this paper is an internal xEMU configuration design developed by NASA Johnson Space Center (JSC) personnel. This paper will expand on the hypervelocity impact (HVI) testing and ballistic limit equation (BLE) definition work that was partially presented at the 2nd International Orbital De-bris (IOC-II) Conference held in Sugar Land, TX in December 2023. The xEMU shares similarities with the legacy Extravehicular Mobility Unit (EMU) spacesuit that is currently used for ISS EVAs, however differences in the layup (e.g., materials, thicknesses, and layers) of the fabric environmental protection garment (EPG), portable life support system (xPLSS) and helmet required an extensive test program to determine ballistic performance. Over 100 hypervelocity impact (HVI) tests were performed by the NASA/JSC HVIT and White Sands Test Facility (WSTF) teams on the xEMU EPG, xPLSS and helmet to generate ballistic limit equations (BLEs) for MMOD impacts. Additionally, over 50 low speed tests (< 1km/s) were performed by the NASA/JSC HVIT and Southwest Research Institute (SwRI) teams on the xEMU EPG, xPLSS and helmet to generate BLEs for lunar ejecta impacts. Post testing, ballistic limit equations used to define the performance of the various regions on the xEMU spacesuit were developed from a generic set of BLEs. The HVI and low speed testing was performed to establish a physical basis for the equations with the co-efficients and exponents of the generic BLEs adjusted to fit the test data. The xEMU BLEs were added to the NASA/JSC software application used for space-craft MMOD risk assessments (BUMPER-3). A finite element model (FEM) of the xEMU spacesuit, which defines the size and shape of the spacesuit as well as the locations of the various shielding configurations, was created based on a solid model provided by the xEMU program office. Using the FEM file and added xEMU BLEs, BUMPER-3 assessments of the xEMU spacesuit for probability of no penetration (PNP) were performed. For the LEO assessment of a typical ISS EVA, the orbital debris and meteoroids environments were defined using the latest engineering models, ORDEM 3.2 and MEM-3 respectively. The lunar sur-face assessment again used the MEM-3 engineering model to define the meteoroid environ-ment along with the current released lunar surface ejecta model, NASA SP-8013 (developed during the Apollo Program). The Space Team in the Natural Environments Branch at Mar-shall Space Flight Center (MSFC) will soon release the new Lunar Meteoroid Ejecta Engineering Model (LMEEM), at which time the xEMU lunar surface EVA will be reassessed. Assessment of the MMOD risk for an 8-hour, 2-person EVA in both LEO and on the lunar surface showed that the xEMU spacesuit meets the program technical requirement of 1 in 2500 failure odds. Similar to the legacy EMU spacesuit, the majority of the MMOD risk (96% of the LEO EVA risk and 99% of the lunar surface EVA risk) is concentrated in regions of xEMU that are comprised primarily of softgoods (arms, legs, and gloves) rather than the hardgoods (xPLSS, hard upper torso and helmet).

Micrometeoroid↗

Micrometeoroid and Orbital Debris (MMOD) Testing, Ballistic Limit Equation Definition and Risk Assessment of the Exploration Extravehicular Mobility Unit (XEMU)

A well-known hazard associated with exposure to the space environment is the risk of failure due to an impact from a micrometeoroid and orbital debris (MMOD) particle. As NASA prepares to return astronauts to the moon with the Artemis program, the next generation of spacesuit is in development to support future extravehicular activities (EVAs). An MMOD impact to the spacesuit is of great concern as a large leak could prevent an astronaut from safely reaching an airlock in time resulting in a loss of life. The exploration extravehicular mobility unit (xEMU) must meet MMOD requirements for multiple environments including those in low earth orbit (LEO) as well as the meteoroid and secondary lunar regolith ejecta environments found on the lunar surface. The subject of this paper is an MMOD risk assessment of the internal xEMU configuration design developed by NASA Johnson Space Center (JSC) personnel. Assessment of the MMOD risk for an 8-hour, 2-person EVA in both LEO and on the lunar surface showed that the xEMU spacesuit meets the program technical requirement of 1 in 2500 failure odds.

Micrometeoroid↗

STS-109 Mission Highlights Resource Tape: Flight Days 4 & 5 - Part 2 of 4

This video, Part 2 of 4, shows the activities of the STS-109 crew (Scott Altman, Commander; Duane Carey, Pilot; John Grunsfeld, Payload Commander; Nancy Currie, James Newman, Richard Linnehan, Michael Massimino, Mission Specialists) during flight days 4 and 5. The activities from other flights days can be seen on 'STS-109 Mission Highlights Resource Tape' Part 1 of 4 (internal ID 2002139471), 'STS-109 Mission Highlights Resource Tape' Part 3 of 4 (internal ID 2002139476), and 'STS-109 Mission Highlights Resource Tape' Part 4 of 4 (internal ID 2002137577). The primary activities during these days were EVAs (extravehicular activities) to replace two solar arrays on the HST (Hubble Space Telescope). Footage from flight day 4 records an EVA by Grunsfeld and Linnehan, including their exit from Columbia's payload bay airlock, their stowing of the old HST starboard rigid array on the rigid array carrier in Columbia's payload bay, their attachment of the new array on HST, the installation of a new starboard diode box, and the unfolding of the new array. The pistol grip space tool used to fasten the old array in its new location is shown in use. The video also includes several shots of the HST with Earth in the background. On flight day 5 Newman and Massimino conduct an EVA to change the port side array and diode box on HST. This EVA is very similar to the one on flight day 4, and is covered similarly in the video. A hand operated ratchet is shown in use. In addition to a repeat of the previous tasks, the astronauts change HST's reaction wheel assembly, and because they are ahead of schedule, install installation and lubricate an instrument door on the telescope. The Earth views include a view of Egypt and Israel, with the Nile River, Red Sea, and Mediterranean Sea.

Source record↗

Metabolomic and Genomic Markers of Atherosclerosis as Related to Oxidative Stress, Inflammation, and Vascular Function in Twin Astronauts

Background: Future human space travel will consist primarily of long-duration missions onboard the International Space Station (ISS) or exploration-class missions to Mars, its moons, or nearby asteroids. Astronauts participating in long-duration missions may be at an increased risk of oxidative stress and inflammatory damage due to radiation, psychological stress, altered physical activity, nutritional insufficiency, and hyperoxia during extravehicular activity. By studying one identical twin during his 1-year ISS mission and one ground-based twin, this work extends a current NASA-funded investigation to determine whether these spaceflight factors contribute to an accelerated progression of atherosclerosis. This study of twins affords a unique opportunity to examine the spaceflight-related atherosclerosis risk independent of the confounding factors associated with different genotypes. Purpose: The purpose of this investigation is to determine whether biomarkers of oxidative and inflammatory stress are elevated during and after long-duration spaceflight and determine if a relation exists between levels of these biomarkers and structural and functional indices of atherosclerotic risk measured in the carotid and brachial arteries. These physiological and biochemical data will be extended by using an exploratory approach to investigate the relationship between intermediate phenotypes and risk factors for atherosclerosis and the metabolomic signature from plasma and urine samples. Since metabolites are often the indirect products of gene expression, we will simultaneously assess gene expression and DNA methylation in leukocytes. Hypothesis: We predict that the space-flown twin will experience elevated biomarkers of oxidative stress and inflammatory damage, altered arterial structure and function, accelerated telomere shortening, dysregulation of genes associated with oxidative stress and inflammation, and a metabolic profile shift that is associated with elevated atherosclerosis risk factors. Conversely, these will not be observed in the ground-based twin. Methods: We will measure blood and urine biomarkers of oxidative stress and inflammation as well as arterial structure and function (carotid intima-medial thickness and brachial artery flow-mediated dilation) in one twin astronaut before, during, and after long-duration spaceflight and in his twin serving as a ground-based control. Furthermore, we will measure metabolomics (targeted and untargeted approaches) and genomic markers (DNA methylation, mRNA gene expression, telomere length) to elucidate the molecular mechanisms involved. A panel of biomarkers of oxidative and inflammatory stress will be measured in venous blood samples and 24-hour (in-flight) and 48-hour (pre- and post-flight) urine pools twice before flight, early (flight days 15 and 60) and late (2 weeks before landing) during the mission, and early in the post-flight recovery phase (approximately 3-5 days after landing). Arterial structure, assessed from measures of intima-media thickness, will be measured at the same times. Arterial function will be assessed using brachial flow-mediated dilation, a well-validated measure used to assess endothelium-dependent vasodilation and a sensitive predictor of atherosclerotic risk, only before and after spaceflight. Discussion: Pre- and in-flight data collection is in progress for the space-flown twin, and similar data have been obtained from the ground-based twin. Blood and urine samples will be batch processed when received from ISS after the conclusion of the 1-year mission. Results from these individual subjects will be compared to the larger complement of subjects participating in the companion study currently ongoing in ISS astronauts.

Lee, Stuart M. C.↗