Determining Thermal Capabilities for External Transfer Operations on the International Space Station

External transfers on the International Space Station (ISS) have a degree of difficulty caused by the severity of the radiative thermal environment and the complexity of the operational choreography to perform the installation and activation of the hardware. These transfers can be performed robotically, by astronauts during an Extra Vehicular Activity (EVA - spacewalk), or combination of robotic/crew operations. Robotic transfers may include capability to intermittently power the hardware; while the hardware remains unpowered for EVA operations. Robotic transfers can be staged to occur in a favorable thermal environment, though typically take longer than a transfer by crew during an EVA where the hardware may not be robotically compatible. The hardware is under passive thermal control, use of optics/multi-layer insulation/heaters, while being transferred from/to a visiting vehicle, airlock, stowage platform, or external ISS structure and may include additional design components, such as removable protective blankets, to meet the transfer requirements. Thermal analysis must be performed to determine the capability of the hardware being transferred to provide the Mission Control team the products necessary to plan and execute the operation while establishing an awareness for any contingency response. An overview of the thermal aspects in planning these types of transfer operations, the analytical approaches and assumptions, and examples of results are provided in this paper

The Design and Testing of the LSSIF Advanced Thermal Control System

The Life Support Systems Integration Facility (LSSIF) provides a platform to design and evaluate advanced manned space systems at NASA Johnson Space Center (JSC). The LSSIF Early Human Testing Initiative requires the integration of such subsystems to enable human occupancy of the 6 meter chamber for a 90 day closed volume test. The Advanced Thermal Control System (TCS) is an important component of the integrated system by supplying coolant to the subsystems within the chamber, such as the Air Revitalization System. The TCS incorporates an advanced high efficiency, heat pump to reject waste heat from the chamber to an external sink or 'lift' temperature that emulates a Lunar environment. The heat pump is the High Lift Heat Pump, developed by Foster-Miller, Inc., and is the main test article of the TCS. The heat pump prototype utilizes a non-CFC refrigerant in a design where the thermal requirements exceed existing terrestrial technology. These operating requirements provide a unique opportunity to design and test an advanced integrated thermal system and the associated controls. The design, control, and systems integration of the heat pump and the TCS also have terrestrial technology application. This paper addresses the design of the TCS and the heat pump, along with the control scheme to fully test the heat pump. Design approaches utilized in the LSSIF TCS are promoted for implementation in terrestrial thermal systems. The results of the preliminary thermal and fluid analyses used to develop the control of the thermal systems will also be discussed. The paper includes objectives for the 90 day human test and the test setup. Finally, conclusions will be drawn and recommendations for Earth design application are submitted

Parents and Peers as Social Influences to Deter Antisocial Behavior

Growth curve analyses were used to investigate parents’ and peers’ influence on adolescents’ choice to abstain from antisocial behavior in a community-based sample of 416 early adolescents living in the Southeastern United States. Participants were primarily European American (91%) and 51% were girls. Both parents and peers were important influences on the choice to abstain from antisocial behavior. Over the four-year period adolescents relied increasingly on parents as influences and relied less on peers as influences to deter antisocial behavior. Significant gender differences emerged and suggested that female adolescents relied more on social influences than did male adolescents but that as time progressed male adolescents increased the rate at which they relied on peers. Higher family income was associated with choosing peers as a social influence at wave 1, but no other significant income associations were found. Understanding influences on adolescents’ abstinence choices is important for preventing antisocial behavior

Are the sources of interest the same for everyone? Using multilevel mixture models to explore individual differences in appraisal structures.

How does personality influence the relationship between appraisals and emotions? Recent research suggests individual differences in appraisal structures: people may differ in an emotion's appraisal pattern. We explored individual differences in interest's appraisal structure, assessed as the within-person covariance of appraisals with interest. People viewed images of abstract visual art and provided ratings of interest and of interest's appraisals (novelty–complexity and coping potential) for each picture. A multilevel mixture model found two between-person classes that reflected distinct within-person appraisal styles. For people in the larger class (68%), the novelty–complexity appraisal had a stronger effect on interest; for people in the smaller class (32%), the coping potential appraisal had a stronger effect. People in the larger class were significantly higher in appetitive traits related to novelty seeking (e.g., sensation seeking, openness to experience, and trait curiosity), suggesting that the appraisal classes have substantive meaning. We conclude by discussing the value of within-person mixture models for the study of personality and appraisal

Lattice effects observed in chaotic dynamics of experimental populations

Animals and many plants are counted in discrete units. The collection of possible values (state space) of population numbers is thus a nonnegative integer lattice. Despite this fact, many mathematical population models assume a continuum of system states. The complex dynamics, such as chaos, often displayed by such continuous-state models have stimulated much ecological research; yet discretestate models with bounded population size can display only cyclic behavior. Motivated by data from a population experiment, we compared the predictions of discrete-state and continuous-state population models. Neither the discrete- nor continuous-state models completely account for the data. Rather, the observed dynamics are explained by a stochastic blending of the chaotic dynamics predicted by the continuous-state model and the cyclic dynamics predicted by the discretestate models. We suggest that such lattice effects could be an important component of natural population fluctuations. The discovery that simple deterministic population models can display complex aperiodi

Changes in Drop-Jump Landing Biomechanics During Prolonged Intermittent Exercise

Background: As injury rates rise in the later stages of sporting activities, a better understanding of lower extremity biomechanics in the later phases of gamelike situations may improve training and injury prevention programs.Hypothesis: Lower extremity biomechanics of a drop-jump task (extracted from a principal components analysis) would reveal factors associated with risk of anterior cruciate ligament injury during a 90-minute individualized intermittent exercise protocol (IEP) and for 1 hour following the IEP.Study Design: Controlled laboratory study.Level of Evidence: Level 4.Methods: Fifty-nine athletes (29 women, 30 men) completed 3 sessions. The first session assessed fitness for an IEP designed to simulate the demands of a soccer match. An experimental session assessed drop-jump biomechanics, after a dynamic warm-up, every 15 minutes during the 90-minute IEP, and for 1 hour following the IEP. A control session with no exercise assessed drop-jump performance at the same intervals.Results: Two biomechanical factors early in the first half (hip flexion at initial contact and hip loading; ankle loading and knee shear force) decreased at the end of the IEP and into the 60-minute recovery period, while a third factor (knee loading) decreased only during the recovery period (P = 0.05).Conclusion: The individualized sport-specific IEP may have more subtle effects on landing biomechanics when compared with short-term, exhaustive fatigue protocols.Clinical Relevance: Potentially injurious landing biomechanics may not occur until the later stages of soccer activity

Changes in Fatigue, Multiplanar Knee Laxity, and Landing Biomechanics During Intermittent Exercise

Context: Knee laxity increases during exercise. However, no one, to our knowledge, has examined whether these increases contribute to higher-risk landing biomechanics during prolonged, fatiguing exercise.Objectives: To examine associations between changes in fatigue (measured as sprint time [SPTIME]), multiplanar knee laxity (anterior-posterior [APLAX], varus-valgus [VVLAX] knee laxity, and internal-external rotation [IERLAX]) knee laxity and landing biomechanics during prolonged, intermittent exercise.Design: Descriptive laboratory study.Setting: Laboratory and gymnasium.Patients or Other Participants: A total of 30 male (age = 20.3 ± 2.0 years, height = 1.79 ± 0.05 m, mass = 75.2 ± 7.2 kg) and 29 female (age = 20.5 ± 2.3 years, height = 1.67 ± 0.08 m, mass = 61.8 ± 9.0 kg) competitive athletes.Intervention(s): A 90-minute intermittent exercise protocol (IEP) designed to simulate the physiologic and biomechanical demands of a soccer match.Main Outcome Measure(s): We measured SPTIME, APLAX, and landing biomechanics before and after warm-up, every 15 minutes during the IEP, and every 15 minutes for 1 hour after the IEP. We measured VVLAX and IERLAX before and after the warm-up, at 45 and 90 minutes during the IEP, and at 30 minutes after the IEP. We used hierarchical linear modeling to examine associations between exercise-related changes in SPTIME and knee laxity with exercise-related changes in landing biomechanics while controlling for initial (before warm-up) knee laxity.Results: We found that SPTIME had a more global effect on landing biomechanics in women than in men, resulting in a more upright landing and a reduction in landing forces and out-of-plane motions about the knee. As APLAX increased with exercise, women increased their knee internal-rotation motion (P = .02), and men increased their hip-flexion motion and energy-absorption (P = .006) and knee-extensor loads (P = .04). As VVLAX and IERLAX increased, women went through greater knee-valgus motion and dorsiflexion and absorbed more energy at the knee (P = .05), whereas men were positioned in greater hip external and knee internal rotation and knee valgus throughout the landing (P = .03). The observed fatigue- and laxity-related changes in landing biomechanics during exercise often depended on initial knee laxity.Conclusions: Both exercise-related changes in fatigue and knee laxity were associated with higher-risk landing biomechanics during prolonged exercise. These relationships were more pronounced in participants with greater initial knee laxity

Influence of Lean Body Mass and Strength on Landing Energetics

Purpose: Less lean body mass may limit one’s ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing.Methods: Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subject’s maximal eccentric strength capabilities.Results: LELM was a significant predictor of EAKNEE (R2 = 0.22, P < 0.01) in females but not in males (R2 = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43–423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05–8.40). No significant relationships were observed in males.Conclusions: LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities

Effects of an Individualized Soccer Match Simulation on Vertical Stiffness and Impedance

An observed relationship between soccer match duration and injury has led to research examining the changes in lower extremity mechanics and performance with fatiguing exercise. Because many fatigue protocols are designed to result in substantial muscular deficits, they may not reflect the fatigue associated with sport-specific demands that have been associated with the increasing incidence of injury as the match progresses. Thus, the aim of this study was to systematically analyze the progressive changes in lower extremity mechanics and performance during an individualized exercise protocol designed to simulate a 90-minute soccer match. Previous match analysis data were used to systematically develop a simulated soccer match exercise protocol that was individualized to the participant's fitness level. Twenty-four National Collegiate Athletic Association Division I soccer players (12 men, 12 women) participated in 2 testing sessions. In the first session, the participants completed the Yo-Yo Intermittent Recovery Test Level 1 to assess their fitness level and determine the 5 submaximal running intensities for their soccer match simulation. In the second test session, progressive changes in the rating of perceived exertion (RPE), lower extremity performance (vertical jump height, sprint speed, and cutting speed), and movement mechanics (jumping vertical stiffness and terminal landing impedance) were measured during the soccer match simulation. The average match simulation running distance was 10,165 ± 1,001 m, consistent with soccer match analysis research. Time-related increases in RPE, and decrements in sprinting, and cutting speed were observed, suggesting that fatigue increased as the simulation progressed. However, there were no time-related decreases in vertical jump height, changes in lower extremity vertical stiffness in jumping, or vertical impedance during landing. Secondary analyses indicated that the coordinative changes responsible for the maintenance of stiffness and impedance differed between the dominant and nondominant limbs. Despite an increase in RPE to near exhaustive levels, and decrements in sprint and cutting performance, the participants were able to maintain jump performance and movement mechanics. Interestingly, the coordinative changes that allowed for the maintenance of vertical stiffness and impedance varied between limbs. Thus, suggesting that unilateral training for performance and injury prevention in soccer-specific populations should be considered