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PubMed1997

An anthropomorphic hand exoskeleton to prevent astronaut hand fatigue during extravehicular activities.

This correspondence presents a prototype of a powered hand exoskeleton that is designed to fit over the gloved hand of an astronaut and offset the stiffness of the pressurized space suit. This will keep the productive time spent in extravehicular activity from being constrained by hand fatigue. The exoskeleton has a three-finger design, the third and fourth fingers being combined to lighten and simplify the assembly. The motions of the hand are monitored by an array of pressure sensors mounted between the exoskeleton and the hand. Controller commands are determined by a state-of-the-art programmable microcontroller using pressure sensor input. These commands are applied to a PWM driven dc motor array which provides the motive power to move the exoskeleton fingers. The resultant motion of the exoskeleton allows the astronaut to perform both precision grasping tasks with the thumb and forefinger, as well as a power grasp with the entire hand.

Anthropometry↗

PubMedDate not supplied

[Hypobaric nitrogen-oxygen atmosphere as a method of preventing altitude decompression sickness].

It has been shown experimentally that the development of altitude decompression disease at 250 and 180 mm Hg can be prevented by preliminary desaturation in the nitrogen-oxygen hypobaric atmosphere (60% N2 and 40% O2 at 550 mm Hg). This has been demonstrated in 38 experiments on 21 test subjects. The use of this atmosphere in space cabin prevents the development of decompression disease upon a decrease of the cabin pressure to 250 mm Hg and upon extravehicular activity in a space suit with 180--200 mm Hg.

Adult↗

PubMed2005

Effects of N-acetylcysteine on glutathione oxidation and fatigue during handgrip exercise.

Fatigue of hand and forearm muscle groups can limit task performance by astronauts wearing space suits. Countermeasures to delay fatigue would therefore be useful to the space program. N-acetylcysteine (NAC) has been shown to inhibit fatigue during other tasks so we tested its effects during handgrip exercise. Volunteers practiced isometric handgrip maneuvers until performance was reproducible over three successive sessions (baseline). Performance then was retested after ingesting NAC (150 mg.kg(-1)) or saline. Drug administration increased NAC and cysteine blood levels (P < 0.001). Performance of sustained maximal efforts was unaffected. During repetitive submaximal efforts, NAC delayed fatigue (130% baseline) and inhibited glutathione oxidation. Saline did not alter glutathione status or performance of sustained maneuvers; repetitive task performance was increased by 15% (P < 0.05), a placebo effect. These data indicate that NAC supports glutathione homeostasis in exercising humans and may delay muscle fatigue during repetitive handgrip exercise. Our findings support oxidative stress as a causal factor in human muscle fatigue and argue for larger translational studies to define NAC effects on human performance.

Acetylcysteine↗

PubMedDate not supplied

[Relation between the probability of development of altitude-decompression disorders and the duration of pre-exposure to a hypobaric atmosphere].

Healthy volunteers, aged 21-47 years, were kept in an altitude chamber. Before decompression to a residual pressure of 293.3 GPa the test subjects were consecutively exposed to 1120 GPa for 2 hrs and then to 733.3 GPa for 24, 18 or 12 hrs. At 293.3 GPa the test subjects performed a moderate workload for 6 hrs. It has been concluded that prior to the use of a space suit with the working pressure 0.3 kgf/cm2 (293.3 GPa) the time of exposure to a hypobaric normoxic (29-30% O2) atmosphere with the total barometric pressure 733.3 GPa should not be less than 18 hrs and it should preferably be 24 hrs. In this situation decompression safety of 6-hr extravehicular activity can be predicted with a high probability.

Adaptation, Physiological↗

PubMedDate not supplied

[External respiration and gas exchange in space flights].

This is an overview of investigations performed in actual and simulated flights to study the effects of microgravity and acceleration, space cabin and space suit artificial atmosphere on the respiratory function. The conceptual prediction of the effects that the space environment produces on the respiratory system suggests the following changes in respiration, gas exchange, and acid-base equilibrium: respiration biomechanics; gas diffusion and ventilation-perfusion ratios in the lungs; regulation of respiration and function of respiratory muscles; lung hydration and blood filling; respiratory changes in acid-base equilibrium and blood gases. Besides, the combined effect of microgravity, acceleration, low barometric pressure and modified gas composition may cause lung atelectases and concomitant disorders in pulmonary ventilation and gas exchange. These changes may have an adverse effect on the health condition and physical work capacity.

Acceleration↗

PubMed1994

NASA and Russian Space Agency sign agreement for additional Space Shuttle/Mir missions

On December 16, 1993 NASA Administrator Daniel S. Goldin [correction of Golden] and the Russian Space Agency (RSA) director Yuri Koptev signed a protocol agreeing to up to 10 Shuttle flights to Mir with a total of 24 months time aboard Mir for U.S. astronants, a program of scientific and technological research, and the upgrade and extension of the Mir lifetime during the period 1995-1997. This is the first of a three-phase program in human spaceflight cooperation which may culminate in the construction of an international Space Station. This agreement starts joint development of spacecraft environmental control and life support systems and potential common space suit.

Humans↗

PubMed2002

[Characteristics of the human thermal state and environment in long-term space flight].

Summarized are data of many-year studies of thermal loading and thermal state of humans in different microclimates. Comparative analysis of various approaches to thermal monitoring of cosmonauts in space suits was performed with the conclusion about advantages of parotid thermometry. To set microclimate standards for long-term space flight, a complex index of the environment cooling potential (ECP) based on the use of an electrical dynamic catathermometer has been proposed. A correlation between ECP values and cosmonaut's thermal sensations was elicited. For the most part, the proposed recommendations have been verified or introduced in the space crew medical care system.

Astronauts↗

PubMed1993

Rationale for a hyperbaric treatment capability at a Lunar Station.

Missions to establish a permanent presence on the Moon will include a significant amount of extravehicular activity (EVA), which carries the risk of decompression sickness (DCS). Factors which will influence that risk include: cabin and space suit pressure environments, frequency of an activity level during EVA, and the possibility of a loss-of-pressure mishap. These factors were considered for Space Station Freedom (SSF), resulting in the decision to include a hyperbaric airlock capable of treating DCS. Using concepts from operational medicine, the need for such a capability is determined by its influence on mission risk. In comparison to SSF, a Lunar Station will have gravity, a higher EVA rate, physically more DCS provocative EVA, and little, if any, capacity for medical evacuation. Therefore, unless Lunar mission planners can provide pressure environments that offer near zero risk of DCS for nominal operations, a hyperbaric treatment capability should be included.

Aerospace Medicine↗

PubMed1978

Prevalence of fungi during Skylab missions.

Samples for mycological analysis were collected from surfaces in the Skylab spacecraft before launch and during flight for each manned mission. Fungal contamination levels were low during the first two flights; however, the species recovered were different for each mission. On the third mission, widespread contamination of the Skylab spacecraft with Aspergillus and Pencillium spp. was detected. This contamination was traced to several contaminated space suit undergarments.

Aspergillus↗

PubMed1981

[Man in the condition of weightlessness (author's transl)].

In the space flights by the USA and USSR to date adequate experience has been obtained on the adaptation of man to living conditions in space--with the technical assistance of an artificial protective atmosphere in the space ship or space suit--and to the singular factor of "weightlessness" (microgravity, low gravity) and how he re-adjusts again after returning to a gravitational field. There is no ultimate or absolute physiological barrier for long term space flight--with one exception: decalcification of the skeleton. For short space flights, however, space sickness is a serious disorder.

Adaptation, Physiological↗

PubMed1980

Automatic control of human thermal comfort by a liquid-cooled garment.

Astronauts utilize water cooling in a liquid-cooled garment to maintain thermal comfort during extravehicular activities (EVA's). In the Apollo and Skylab Programs, manual control of the cooling water was a necessary operation to ensure proper control of body heat storage for the EVA crewman. The development of an automatic thermal control system would be a valuable asset to the conduct of EVA, relieving the crewman of a task that can interfere with his EVA objectives. An analytical model of human thermoregulation was used to develop the equations governing the operation of such an automatic controller. A series of tests verified the feasibility of a controller utilizing only a measurement of the difference in coolant temperature into and out of the astronaut's liquid-cooled garment and an estimate of environmental heat loss to maintain the proper crewman thermal balance. Three test subjects performed over a wide range of metabolic rates, and the crewman heat balance was maintained well within allowable medical limits. This study demonstrates the use of a mathematical model to generate previously unknown physiological relationships between human thermal comfort and liquid cooled garment performance. In so doing, it quantitates physiological parameters that are difficult to relate directly by experiment. Index terms: body temperature regulation, space suit cooling, temperature control, human thermoregulation.

Aerospace Medicine↗

PubMed1987

Man in space.

Today, more than 20 years after the first in the world man's space walk, soviet cosmonautics gained large experience of extravehicular activity (EVA). Space suits of high reliability, onboard facilities for passing through the airlock, sets of special tools and technological rigging, as well as procedures for carrying out various EVA's were developed. In the course of the Salyut-7 space station orbital operation the EVA's have become regular. The author of the report as the participant of the EVA's considers the main steps of man activities in space and analyzes specific problems arised in performing such activities.

Astronauts↗

PubMed1963

Estimates of radiation doses in space on the basis of current data.

A gross survey of data on Van Allen belt radiations, galactic cosmic radiation, and solar cosmic radiation is presented. On the basis of these data that are, in part, fragmentary and uncertain, upper and lower limits of rad doses under different amounts of mass shielding are estimated. The estimates are preliminary especially in the cases of chance encounter with solar flare protons. Generally, the relative biological effectiveness of the high energetic space radiations and their secondaries appear insufficiently known to give detailed biological or rem doses. The overall ionization dosage of the low level galactic cosmic radiation in free space is estimated to be even in solar minimum years equivalent to less than 50 rem/year or 1 rem/week. Mass shielding up to 80 g/cm2 would not reduce the ionization dosage but would shield against heavy primaries and heavy ionizing secondaries, thus reducing the biological dose. The flux of energetic protons in the maximum intensity zone of the inner Van Allen belt is by about four orders of magnitude higher, their energy and penetration power, of course, lower. A shield of 25 g/cm2 would reduce the dose rate from 20 rad/hour under 2 g/cm2 to 5 rad/hour. These proton dose rates and also the electron and X-radiation dose rates under some g/cm2 shielding of low z-number material will not constitute a radiation hazard for flights straight through the inner and outer belt in about two hours. Staying within the maximum of the inner belt for two days would, however, lead even within 25 g/cm2 depth of outer shield and body itself to a dose of 200 rad which is on the permissible limit. Extreme solar cosmic ray events or proton showers of high intensity and a duration of days occurred with a frequency of 1-4 per year during the last highly active cycle. For the penetrating, most intense high energy event of February 23, 1956, the dose within 25 g/cm2 is estimated to have been in the order of 50 rad. In most cases the dose decreased more rapidly with penetration depth and would have been even in multiple events with such high shielding below critical levels, especially on inner organs. On the surface of the body and in a lightly shielded space vehicle or protected by a space suit only the dose can, especially in multiple events, reach values of 1000 rad and more.

Atmosphere↗

PubMed1998

Towards new paradigms for the treatment of hypobaric decompression sickness.

Altitude induced (hypobaric) decompression sickness (DCS) has long been treated with ground level oxygen and U.S. Navy Treatment Tables 5 and 6. These treatment tables originate from surface excursion diving and, when implemented, require significant resource allocation. Although they are effective treatment regimens, these tables were not developed for treating hypobaric DCS which has an etiology similar to saturation diving DCS. In this review, different treatment options for hypobaric DCS are presented. These options include more aggressive use of ground level oxygen and treatment tables using a maximum pressure of 2 atmospheres (ATA). Specific attention is given to USAF Table VIII, an experimental hypobaric DCS treatment-table, and space suit overpressurization treatment. This paradigm shift for DCS treatment is based on a projected increase in hypobaric DCS treatment from exposure to low pressure during several operational conditions: cruise flight in the next generation aircraft (e.g., F-22); high altitude, unpressurized flight by special operations forces; and the extraordinary amount of extravehicular activity (EVA) required to construct the international space station. Anticipating the need to treat DCS encountered during these and other activities, it is proposed that 2 ATA or less hyperbaric oxygen (HBO) treatment conjoined with new collapsible chamber technology can be used to address these issues in a safe and cost effective fashion.

Aerospace Medicine↗

PubMedDate not supplied

[Probability of altitude decompression sickness during a suited exit from a space ship having a near-Earth atmosphere].

A large number (550) pressure chamber experiments in which 200 suited subjects simulated an egress from the spacecraft (decompression from 760 to 20--10 mm Hg) showed a relationship between decompression sickness frequency and severity, space suit absolute pressure (160--310 mm Hg), time of the exposure (1--10 hours) and desaturation (15--60 min), and exercise load (150--400 Cal/hr). Without desaturation there were no decompression sickness symptoms at a suit pressure of 270--310 mm Hg. An egress into space in a suit at a pressure of 160--230 mm Hg after 15--60 min desaturation induced bends of different severity. Less frequent cases of decompression sickness in our experiments as compared with the literature data (obtained on unsuited subjects) can be attributed to the peculiar kinematics of movements and excessive pressure in the suit.

Adult↗

PubMedDate not supplied

[Prevention of decompression sickness as applied to conditions of multiple space walks].

Six 3-day experiments were carried out in an altitude chamber in which 6 test subjects took part. The experiments simulated repeated extra-vehicular activities--intensive work at an altitude of 10,000 m in a helmet or at an altitude of 40,000 m on a space suit pressurized at 200 mm Hg. It was demonstrated that altitude decompression could be prevented by desaturation--prolonged exposure to the hypobaric atmosphere (430 mm Hg) and 100% O2 or a 40% O2 and 60% N2 mixture. During the 3-day experiment the test subjects made seven 3--4 hour excursions, showing no symptoms of decompression disease.

Adult↗

PubMedDate not supplied

[Physiologico-hygienic provisions for cosmonauts for their orbital flight].

This paper briefly describes physiologo-hygienic evaluations of space suits, data of the preflight training and extravehicular activities of the Salyut-6 crewmembers. It discusses changes in physiological parameters, energy expenditures, heat release and associated performance of the autonomic life support system. The paper also analyzes physiologo-hygienic aspects of the extravehicular activity of the Salyut-6 crewmembers.

Aerospace Medicine↗

PubMed1994

As assessment of habitat pressure, oxygen fraction, and EVA suit design for space operations.

At high cabin pressure [e.g. 1013 hPa (14.7 psi) 21% O2] there are serious issues relative to specification of suit pressure and the need for prebreathing. A high pressure suit will be costly but use of the existing, flexible suit requires up to 6 h of prebreathing. Or one could use a cabin pressure of 700 hPa (10.2 psi) prior to extravehicular activity (EVA) in order to use the existing suit with only 1 h of prebreathing. If these normal cabin pressures and O2 levels are utilized, existing physiological and medical databases apply, providing a known basis for evaluating effects of long duration space missions. If a 345 hPa (5 psi), 70-100% O2 atmosphere is adopted the existing suit can be used with no prebreathing required. However, there is no reference database on physiological effects under the conditions of lower pressure and higher O2 concentration. This paper considers the major issues involved in defining habitat pressure, O2 fraction, and EVA suit design for operations in space. A preliminary model for evaluating habitat/suit pressure and O2% strategies is presented.

Aerospace Medicine↗