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PubMed1987

Spacelab experiments on space motion sickness.

Recent research results from ground and flight experiments on motion sickness and space sickness conducted by the Man Vehicle Laboratory are reviewed. New tools developed include a mathematical model for motion sickness, a method for quantitative measurements of skin pallor and blush in ambulatory subjects, and a magnitude estimation technique for ratio scaling of nausea or discomfort. These have been used to experimentally study the time course of skin pallor and subjective symptoms in laboratory motion sickness. In prolonged sickness, subjects become hypersensitive to nauseogenic stimuli. Results of a Spacelab-1 flight experiment are described in which four observers documented the stimulus factors for and the symptoms/signs of space sickness. The clinical character of space sickness differs somewhat from acute laboratory motion sickness. However SL-1 findings support the view that space sickness is fundamentally a motion sickness. Symptoms were subjectively alleviated by head movement restriction, maintenance of a familiar orientation with respect to the visual environment, and wedging between or strapping onto surfaces which provided broad contact cues confirming the absence of body motion.

Adaptation, Physiological↗

PubMed1993

Limitations to the study of man in space in the U.S. space program.

Research on humans conducted during spaceflight is fraught both with great opportunities and great obstacles. The purpose of this paper is to review some of the limitations to research in space in the United States with hope that an informed scientific community may lead to more rapid and efficient solution of these problems. Limitations arise because opportunities to study the same astronauts in well-controlled situations on repeated spaceflights are practically non-existent. Human research opportunities are further limited by the necessity of avoiding simultaneous mutually-interfering experiments. Environmental factors, including diet and other physiological perturbations concomitant with spaceflight, also complicate research design and interpretation. Technical limitations to research methods and opportunities further restrict the development of the knowledge base. Finally, Earth analogues of space travel all suffer from inadequacies. Though all of these obstacles will eventually be overcome, creativity, diligence, and persistence are required to further our knowledge of humans in space.

Humans↗

PubMed1989

Assessing applicants to the NASA flight program for their renal stone-forming potential.

Spaceflight could provoke formation of kidney stones, in part by causing hypercalciuria and hyperphosphaturia. Applicants for spaceflight who have metabolic or environmental derangements to begin with might be particularly susceptible to stone formation in space. We, therefore, analyzed 24-h urine samples for stone-forming risk factors in 104 male applicants before their selection into the astronaut-mission specialist corps. The urinary environment was abnormally supersaturated with calcium oxalate in 25.0% of applicants, brushite in 36.5%, and monosodium urate in 66.3%, predisposing these applicants to crystallization of stone-forming calcium salts. This high level of supersaturation was caused by both "metabolic" and environmental disturbances. Thus, hypercalciuria was found in 11.5% of applicants, hyperoxaluria in 2.9%, hyperuricosuria in 18.3% and hypocitraturia in 5.8%. Environmental derangements were generally more prominent, as indicated by low urine volume of less than 2 L.d-1 in 84.6%, high urinary phosphate in 24.4%, and high urinary sodium in 10.6% of applicants. The results suggest that most of the abnormal stone risk factors disclosed among applicants for spaceflight programs were environmental in origin.

Adult↗

PubMed2002

Development of U.S.-Russian medical support procedures for long-duration spaceflight: the NASA-Mir experience.

As the Russian Space Agency and the U.S. National Aeronautics and Space Administration began in the mid-1990s to plan a preliminary cooperative flight program in anticipation of the International Space Station, programmatic and philosophical differences became apparent in the technical and medical approaches of the two agencies. This paper briefly describes some of these differences and the process by which the two sides resolved differences in their approaches to the medical selection and certification of NASA-Mir crewmembers. These negotiations formed the basis for developing policies on other aspects of the medical support function for international missions, including crew training, preflight and postflight data collection, and rehabilitation protocols. The experience gained through this cooperative effort has been invaluable for developing medical care capabilities for the International Space Station.

Certification↗

PubMed2000

[Transmission and exchange of genetic information during bacterial conjugation in ground-based simulations of the factors of orbital flight].

Control laboratory experiments on bacterial conjugation under simulated spaceflight conditions were performed with the use of new equipment (bioreactor RECOMB-2 and container BIOMAGNISTAT) within the RSA-NASA science program. External parameters were selected and the plan of simulation of a space experiment was verified to ensure high efficiency of the conjugative transfer of chromosomal and plasmid DNA and storage of hybrids on the ground. Genetic analysis of conjugative hybrids E. coli supported the hypothesized possibility of transfer of a whole bacterial chromosome during conjugation that will lead to relative stabilization of the diploid state. Earlier this hypothesis was used to interpret results of experiments performed on MIR in 1992-1993. Hence, the ground laboratory investigations proved the conclusion about high probability of transfer of large fragments or even a whole chromosome during space flight. Screening of the geomagnetic field by BIOMAGNISTAT increases the probability of conjugative contacts between cells and is likely to slightly inhibit the processes of recombination.

Conjugation, Genetic↗

PubMed2002

Human motion planning based on recursive dynamics and optimal control techniques.

This paper presents an efficient optimal control and recursive dynamics-based computer animation system for simulating and controlling the motion of articulated figures. A quasi-Newton nonlinear programming technique (super-linear convergence) is implemented to solve minimum torque-based human motion-planning problems. The explicit analytical gradients needed in the dynamics are derived using a matrix exponential formulation and Lie algebra. Cubic spline functions are used to make the search space for an optimal solution finite. Based on our formulations, our method is well conditioned and robust, in addition to being computationally efficient. To better illustrate the efficiency of our method, we present results of natural looking and physically correct human motions for a variety of human motion tasks involving open and closed loop kinematic chains.

Algorithms↗

PubMed1999

The response of bone to unloading.

Skeletal unloading leads to decreased bone formation and decreased bone mass. Bone resorption is uncoupled from bone formation, contributing to the bone loss. During spaceflight bone is lost principally from the bones most loaded in the 1-g environment, and some redistribution of bone from the lower extremities to the head appears to take place. Although changes in calcitropic hormones have been demonstrated during skeletal unloading (PTH and 1,25(OH)2D decrease), it remains unclear whether such changes account for or are in response to the changes in bone formation and resorption. Bed rest studies with human volunteers and hindlimb elevation studies with rats have provided useful data to help explain the changes in bone formation during spaceflight. These models of skeletal unloading reproduce a number of the conditions associated with microgravity, and the findings from such studies confirm many of the observations made during spaceflight. Determining the mechanism(s) by which loading of bone is sensed and translated into a signal(s) controlling bone formation remains the holy grail in this field. Such investigations couple biophysics to biochemistry to cell and molecular biology. Although studies with cell cultures have revealed biochemical responses to mechanical loads comparable to that seen in intact bone, it seems likely that matrix-cell interactions underlie much of the mechanocoupling. The role for systemic hormones such as PTH, GH, and 1,25(OH)2D compared to locally produced factors such as IGF-I, PTHrP, BMPs, and TGF-beta in modulating the cellular response to load remains unclear. As the mechanism(s) by which bone responds to mechanical load with increased bone formation are further elucidated, applications of this knowledge to other etiologies of osteoporosis are likely to develop. Skeletal unloading provides a perturbation in bone mineral homeostasis that can be used to understand the mechanisms by which bone mineral homeostasis is maintained, with the expectation that such understanding will lead to effective treatment for disuse osteoporosis.

Animals↗

PubMed1996

Control of red blood cell mass in spaceflight.

The effect of spaceflight on red blood cell mass (RBCM), plasma volume (PV), erythron iron turnover, serum erythropoietin, and red blood cell (RBC) production and survival and indexes were determined for six astronauts on two shuttle missions, 9 and 14 days in duration, respectively. PV decreased within the first day. RBCM decreased because of destruction of RBCs either newly released or scheduled to be released from the bone marrow. Older RBCs survived normally. On return to Earth, plasma volume increased, hemoglobin concentration and RBC count declined, and serum erythropoietin increased. We propose that entry into microgravity results in acute plethora as a result of a decrease in vascular space. PV decreases, causing an increase in hemoglobin concentration that effects a decrease in erythropoietin or other growth factors or cytokines. The RBCM decreases by destruction of recently formed RBCs to a level appropriate for the microgravity environment. Return to Earth results sequentially in acute hypovolemia as vascular space dependent on gravity is refilled, an increase in plasma volume, a decrease in hemoglobin concentration (anemia), and an increase in serum erythropoietin.

Adaptation, Physiological↗

PubMed1989

Late cataractogenesis caused by particulate radiations and photons in long-lived mammalian species.

Radiation cataractogenesis induced by small acute doses of particulate radiations and photons in the New Zealand white (NZW) rabbit (Oryctolagus cuniculus), the beagle dog (Canis familiaris) and the rhesus monkey (Macaca mulatta) is discussed in the context of the use of animal models to assess the radiation hazards faced by humans during lengthy sojourns in deep space. Attention is paid to: 1) the importance of lifespan studies with long-lived species--the above animals have median lifespans in captivity of 5-7, 13-14 and approximately 25 years, respectively; 2) the magnitudes of possible dose thresholds for cataractogenesis from sparsely ionizing radiations and the modifications of those thresholds by the late degenerative phase of the phenomenon.

Animals↗

PubMed2004

Group interactions during space missions.

INTRODUCTION: Previous anecdotal reports from space and results from space simulation studies on Earth have suggested that the group interactions of crewmembers during space missions can be problematic in ways that can negatively affect crew safety and the accomplishment of mission goals. METHODS: To assess the interpersonal environment of space crewmembers, we used a set of standard questionnaires that were completed by 5 astronauts, 8 cosmonauts, and 58 American and Russian mission control personnel who participated in the Shuttle/Mir Program. RESULTS: Although we did not find strong evidence supporting predicted decrements in tension and cohesion during the second half of the missions, we did find that both crewmembers and mission control personnel displaced unpleasant emotions to monitoring personnel outside of their group. We also found significant differences between Americans and Russians in terms of measures of satisfaction with their interpersonal and work environments. CONCLUSIONS: These findings suggest a number of countermeasures to help future space crews deal with potential maladaptive group interactions. These countermeasures address issues at the time of selection, during prelaunch training, during the mission itself, and after the crew returns to Earth.

Astronauts↗

PubMed1990

Medical considerations for extending human presence in space.

The prospects for extending the length of time that humans can safely remain in space depend partly on resolution of a number of medical issues. Physiologic effects of weightlessness that may affect health during flight include loss of body fluid, functional alterations in the cardiovascular system, loss of red blood cells and bone mineral, compromised immune system function, and neurosensory disturbances. Some of the physiologic adaptations to weightlessness contribute to difficulties with readaptation to Earth's gravity. These include cardiovascular deconditioning and loss of body fluids and electrolytes; red blood cell mass; muscle mass, strength, and endurance; and bone mineral. Potentially harmful factors in space flight that are not related to weightlessness include radiation, altered circadian rhythms and rest/work cycles, and the closed, isolated environment of the spacecraft. There is no evidence that space flight has long-term effects on humans, except that bone mass lost during flight may not be replaced, and radiation damage is cumulative. However, the number of people who have spent several months or longer in space is still small. Only carefully-planned experiments in space preceded by thorough ground-based studies can provide the information needed to increase the amount of time humans can safely spend in space.

Adaptation, Physiological↗

PubMed1992

Radiation issues for piloted Mars mission.

Man is now entering an era of colonizing the moon and exploration of Mars. The crewmembers of a piloted mission to Mars will be exposed to inner belt trapped protons, the outer trapped electrons, and the galactic cosmic radiation. In addition there is always the added risk of acute exposure to a solar particle event. Current radiation risk is estimated using the idea of absorbed dose and ICRP-26, LET-dependent quality factors. In a spacecraft with aluminum walls (2 g cm-2) at solar minimum the calculated dose equivalent is 0.73 Sv for a 406-day mission. Based on the current thinking this leads to an excess cancer mortality in a 35 year male of about 1%. About 75% of the dose equivalent is contributed by HZE particles and target fragments with average quality factors of 10.3 and 20, respectively. The entire concept of absorbed dose, quality factor, and dose equivalent as applied to such missions needs to be reexamined, in light of the fact that less than 50% of the nuclei in the body of the astronaut would have been traversed by a single GCR nuclei in the 406-day mission. Clearly, more biologically relevant information about the effects of heavy ions and target fragments is needed and fluence based risk estimation strategy developed for such long term stays in space.

Adult↗

PubMed2004

Personality characteristics and trait clusters in final stage astronaut selection.

INTRODUCTION: This paper presents personality testing data from final stage applicants to the NASA astronaut program. Questions addressed include whether personality predicted final selection into the astronaut corps, whether women and men demonstrated typical gender differences in personality, and whether three characteristic clusters found in other high performance populations replicated in this group. METHODS: Between 1989 and 1995, 259 final stage astronauts completed the Personal Characteristic Inventory (PCI) which assesses personality characteristics related to the broad traits of Instrumentality and Expressivity. In addition, 147 of these individuals also completed an abbreviated version of the NEO Five Factor Inventory (NEO-FFI) which assesses the "Big Five" traits of Neuroticism, Extraversion, Openness, Agreeableness, And Conscientiousness. RESULTS: Three previously identified trait clusters (Right, Wrong, and No Stuff) were found to replicate in this population. No differences were found on the PCI or on the modified NEO-FFI between applicants who were chosen to become astronauts (n = 63) and those who were not (n = 196). Men scored higher than women on competitiveness, but lower on expressivity and achievement strivings. DISCUSSION: These analyses suggest that the "Right Stuff," "Wrong Stuff" and "No Stuff" clusters originally described in airline pilots and other high performance groups also exist within this population. Consistent with findings from other high performance populations, men and women tend to differ to a lesser extent than found in the general population, particularly on traits related to achievement motivation. Personality trait testing did not predict which applicants were most likely to be accepted into the astronaut corps.

Astronauts↗

PubMed1989

The evolution of complex life.

In considering the probabilities that intelligent life might exist elsewhere in the Universe, it is important to ask questions about the factors governing the emergence of complex living organisms in the context of evolutionary biology, planetary environments and events in space. Two important problems arise. First, what can be learned about the general laws governing the evolution of complex life anywhere in space by studying its history on the Earth? Second, how is the evolution of complex life affected by events in space? To address these problems, a series of Science Workshops on the Evolution of Complex Life was held at the Ames Research Center. Included in this paper are highlights of those workshops, with particular emphasis on the first question, namely the evolution of complex extraterrestrial life.

Animals↗

PubMed2000

Development of a 10-day cycle menu for Advanced Life Support.

The Advanced Life Support (ALS) program at NASA-Johnson Space Center was initiated for use in long-duration space missions. With weight and volume restrictions and prolonged periods between resupply from Earth, as much as 90% of the energy requirements must come from food grown, processed, and prepared in space. ALS involves the use of hydroponically grown crops to supply and regenerate air and food for the crew. A 10-day cycle menu has been developed consisting of items prepared from the baseline crop list: potato, sweet potato, brown rice, wheat, peanut, soybean, lettuce, tomato, carrot, chard, radish, spinach, green onion, and dry beans (pinto and lentil). Of the recipes created for the menu, resupply items contributed only 4.54% by weight and 9.18% of the total calories. The menu has been analyzed to conform to the baseline crop list and nutrient recommendations for long-duration space missions.

Adult↗

PubMed2005

Human behavioral research in space: quandaries for research subjects and researchers.

With the advent of long-duration spaceflight on board the International Space Station (ISS) and possible future missions beyond low Earth orbit (LEO) such as Mars, it is critical that those at NASA have a realistic assessment of the challenges that will face individuals on long-duration missions so that they can develop preventive and real-time countermeasures to behavioral health issues. While space travellers are very interested in having countermeasures to the deleterious effects of space missions, they have a powerful disincentive to participate in this research if they feel it could in any way negatively affect their flight status. The behavioral issues of isolation and confinement for extended-duration space missions are reviewed. Areas of basic and clinical behavioral research are listed. And the classical clinical model for research is not considered appropriate for the current configuration of the space program. The use of analogue environments and advanced statistical analysis are suggested as ways to address the limited spaceflight research opportunities. The challenge of research subject or patient confidentiality vs. mission safety and issues of personal flight status are addressed.

Adaptation, Physiological↗

PubMed1990

An Antarctic research outpost as a model for planetary exploration.

During the next 50 years, human civilization may well begin expanding into the solar system. This colonization of extraterrestrial bodies will most likely begin with the establishment of small research outposts on the Moon and/or Mars. In all probability these facilities, designed primarily for conducting exploration and basic science, will have international participation in their crews, logistical support and funding. High fidelity Earth-based simulations of planetary exploration could help prepare for these expensive and complex operations. Antarctica provides one possible venue for such a simulation. The hostile and remote dry valleys of southern Victoria Land offer a valid analog to the Martian environment but are sufficiently accessible to allow routine logistical support and to assure the relative safety of their inhabitants. An Antarctic research outpost designed as a planetary exploration simulation facility would have great potential as a testbed and training site for the operation of future Mars bases and represents a near-term, relatively low-cost alternative to other precursor activities. Antarctica already enjoys an international dimension, an aspect that is more than symbolically appropriate to an international endeavor of unprecedented scientific and social significance--planetary exploration by humans. Potential uses of such a facility include: 1) studying human factors in an isolated environment (including long-term interactions among an international crew); 2) testing emerging technologies (e.g., advanced life support facilities such as a partial bioregenerative life support system, advanced analytical and sample acquisition instrumentation and equipment, etc.); and 3) conducting basic scientific research similar to the research that will be conducted on Mars, while contributing to the planning for human exploration. (Research of this type is already ongoing in Antarctica).

Antarctic Regions↗

PubMed1991

Space adaptation syndrome: multiple etiological factors and individual differences.

Space motion sickness is a significant operational concern in the American and Soviet space programs. Nearly 70% of all astronauts and cosmonauts are affected to some degree during their first several days of flight. It is now beginning to appear that space motion sickness like terrestrial motion sickness is the consequence of multiple etiological factors. As we come to understand basic mechanisms of spatial orientation and sensory-motor adaptation we can begin to predict etiological factors in different motion environments. Individuals vary greatly in the extent to which they are susceptible to these different factors. However, individuals seem to be relatively self-consistent in terms of their rates of adaptation to provocative stimulation and their retention of adaptation. Attempts to relate susceptibility to motion sickness during the microgravity phases of parabolic flight maneuvers to vestibular function under 1G and 0G test conditions are described.

Adaptation, Physiological↗