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PubMed1998

[Low vacuum as a ground simulation method for studies of gas convection heat transfer inside manned spacecraft].

Owing to reduced gravity on the orbit, the convection model of the environment inside the manned spacecraft becomes complicated, and it is difficult to simulate under 1G condition for related studies on the ground. The author described a method using low vacuum to simulate the effect of reduced gravity on gas convection heat transfer for ground studies of environmental control and lifesupport system of manned spacecraft. It is demonstrated that when suitable experimental vessel and appropriate method are used, it is possible that convection heat transfer of the environment inside the manned spacecraft flying on the orbit may be simulated successfully on the ground.

Air Conditioning↗

PubMed1999

[Analysis of mass optimization of manned spacecraft ECLSS thermo-hydraulic network].

OBJECTIVE: To reduce the weight of manned spacecraft Environment Control and Life Support System (ECLSS). METHOD: Based on network analysis theory, the flow and thermo-hydraulic network composed of gas and liquid loops in manned spacecraft ECLSS was explored to reduce the weight of ECLSS. The physical models and mathematical models of flow, heat transfer and weight calculation in the network were established. The thermodynamic parameters and weight of the network were calculated on the bases of energy balance, heat transfer relation and the component weight relation. And influencing factors on the system weight were discussed. RESULT: (1) There is an optimal pipe diameter in the system and the diameter is influenced by flow rate to a large extent; (2) The weight can be reduced by raising inlet temperature properly; (3) The best heat exchange layout makes the weight lightest. CONCLUSION: The obtained results are of importance for reducing launching weight of manned spacecraft.

Air Conditioning↗

PubMed1997

Carcinogens in spacecraft air.

The health effects of long-term exposure to ionizing radiation during spaceflight are a major concern to NASA, especially for missions beyond low-Earth orbit. Experiments involving astronauts will be conducted during the next few years to improve the risk assessment for exposures to ionizing radiation during flights; however, concomitant exposure to certain airborne chemical carcinogens during these experiments could confound the results of radiation experiments. Carcinogens can reach the spacecraft atmosphere from leaking thrusters, from off-gassing materials, from chemical experiments and from human metabolism. The Johnson Space Center Toxicology Group routinely analyzes atmospheric samples collected aboard spacecraft. The exposure limits for radiomimetic compounds such as benzene are reduced because of the potential interaction between radiation and chemical exposures. Analysis of recent spacecraft air samples indicates that the following carcinogens are often present in measurable concentrations: acetaldehyde, dichloromethane, formaldehyde and isoprene. Occasionally, the carcinogens 1,2-dichloroethane, acrolein, benzene and furan are found in atmospheric samples. During normal operating conditions, the low concentrations of and limited periods of exposure to airborne carcinogens are thought to pose minimal health risks to crew members, and should not confound experiments involving sensitive methods to detect biological effects of ionizing radiation.

Acetaldehyde↗

PubMed2001

Deflection of spacecraft trajectories as a new test of general relativity.

We derive a simple formula which gives the general relativistic deflection of a spacecraft, idealized as a point mass, for all values of the asymptotic speed V(infinity) (0< or =V(infinity)< or =1). Using this formula we suggest a new test of general relativity (GR) which can be carried out during a proposed interstellar mission that involves a close pass of the Sun. We show that, with foreseeable improvements in spacecraft tracking sensitivity, the deflection of a spacecraft's trajectory in the gravitational field of the Sun could provide a new test of GR.

Gravitation↗

PubMed1977

Microbiological profiles of the Viking spacecraft.

Planetary quarantine requirements associated with the launch of two Viking spacecraft necessitated microbiological assessment during assembly and testing at Cape Canaveral and the Kennedy Space Center. Samples were collected from selected surface of the Viking Lander Capsules (VLC), Orbiters, (VO), and Shrouds at predetermined intervals during assembly and testing. Approximately 7,000 samples were assayed. Levels of bacterial spores per square meter on the VLC-1 and VLC-2 were 1.6 x 10(2) and 9.7 x 10(1), respectively, prior to dry-heat sterilization. The ranges of aerobic mesophilic microorganisms detected on the VO-1 and VO-2 at various sampling events were 4.2 x 10(2) to 4.3 x 10(3) and 2.3 x 10(2) to 8.9 x 10(3)/m2, respectively. Approximately 1,300 colonies were picked from culture plates, identified, lypholipized, and stored for future reference. About 75% of all isolates were microorganisms considered indigenous to humans; the remaining isolates were associated with soil and dust in the environment. The percentage of microorganisms of human origin was consistent with results obtained with previous automated spacecraft but slightly lower than those observed for manned (Apollo) spacecraft.

Actinomycetales↗

PubMed2005

Survival of spacecraft-associated microorganisms under simulated martian UV irradiation.

Spore-forming microbes recovered from spacecraft surfaces and assembly facilities were exposed to simulated Martian UV irradiation. The effects of UVA (315 to 400 nm), UVA+B (280 to 400 nm), and the full UV spectrum (200 to 400 nm) on the survival of microorganisms were studied at UV intensities expected to strike the surfaces of Mars. Microbial species isolated from the surfaces of several spacecraft, including Mars Odyssey, X-2000 (avionics), and the International Space Station, and their assembly facilities were identified using 16S rRNA gene sequencing. Forty-three Bacillus spore lines were screened, and 19 isolates showed resistance to UVC irradiation (200 to 280 nm) after exposure to 1,000 J m(-2) of UVC irradiation at 254 nm using a low-pressure mercury lamp. Spores of Bacillus species isolated from spacecraft-associated surfaces were more resistant than a standard dosimetric strain, Bacillus subtilis 168. In addition, the exposure time required for UVA+B irradiation to reduce the viable spore numbers by 90% was 35-fold longer than the exposure time required for the full UV spectrum to do this, confirming that UVC is the primary biocidal bandwidth. Among the Bacillus species tested, spores of a Bacillus pumilus strain showed the greatest resistance to all three UV bandwidths, as well as the total spectrum. The resistance to simulated Mars UV irradiation was strain specific; B. pumilus SAFR-032 exhibited greater resistance than all other strains tested. The isolation of organisms like B. pumilus SAFR-032 and the greater survival of this organism (sixfold) than of the standard dosimetric strains should be considered when the sanitation capabilities of UV irradiation are determined.

Bacillus↗

PubMed1974

Comparison of media for detection of fungi on spacecraft.

Five media, including Trypticase soy agar (TSA; BBL) pour plates, spread plates of TSA, Mycophil agar with chloromycetin, Mycophil agar with chloromycetin and Actidione, and cornmeal agar with chloromycetin were quantitatively and qualitatively compared for the detection of fungi on spacecraft. Cornmeal agar with chloromycetin yielded the highest number of fungal colonies, although not always significantly higher than Mycophil agar with chloromycetin or TSA spread plates. Cornmeal agar with chloromycetin also gave the best qualitative representation of fungi on the spacecraft, recovering 68% of the genera found from all media. This medium yielded 10 times the number of fungal colonies and 3 times the number of genera found on TSA pour plates as currently used for spacecraft assay.

Agar↗

PubMed1992

A model of radiation conditions during spacecraft flights in the interplanetary space and in the Earth's magnetosphere.

Based on the available measurement data, simulations of radiation conditions during spacecraft flights in the interplanetary space and in the Earth's and Jupiter's radiation belts has been carried out. The > or = 10 MeV and > or = 30 MeV solar flare proton fluence forecast has been proposed for Cycle 22. Radiation conditions due to both magnetospheric electrons and protons and to solar flare protons, magnetic rigidity cutoff being taken into account, have been evaluated on spacecraft trajectories in the Earth's and Jupiter's magnetospheres.

Cosmic Radiation↗

PubMed1994

Investigation of the low-energy component of primary cosmic radiation on the outside of spacecrafts.

We have developed a method to investigate the low-energy radiation environment on the outside of spacecrafts. Thereby, ultra-thin thermoluminescent (TL) detectors on the base of CaF2:Mn-PTFE are arranged in stacks and exposed to the unshielded cosmic radiation. The dose distribution within a stack is determined by successive evaluation of the thin TL sheets. The analysis of LiF thermoluminescent detector glow curves permits conclusions on the dose contribution caused by either low-energy electrons or by protons. The method was applied aboard Russian COSMOS spacecrafts as well as the MIR station. It was shown that along low-earth orbits dose rates up to 10 Gy/day within the first few mg/cm2 are typical, mainly as a result of the electron impact.

Cosmic Radiation↗

PubMed2006

An ultrasonic array sensor for spacecraft leak direction finding.

We have developed an ultrasonic array sensor useable for locating air leaks in manned spacecraft and have found that this sensor locates leaks in a 1-m(2) plate to within 2 cm. The sensor consists of a 63-element multiplexed array plus a reference element, all constructed from a single PZT disc and a printed circuit board. Cross-correlations of signals from the array elements with signals from the single reference element provide a measurement of the leak noise passing through the spacecraft skin under the array. A spatial Fourier transform reveals the dominant direction of propagation. Triangulation from multiple sensor locations can be used to find the source of the leak.

Equipment Design↗

PubMed2003

Survival of endospores of Bacillus subtilis on spacecraft surfaces under simulated martian environments: implications for the forward contamination of Mars.

Experiments were conducted in a Mars simulation chamber (MSC) to characterize the survival of endospores of Bacillus subtilis under high UV irradiation and simulated martian conditions. The MSC was used to create Mars surface environments in which pressure (8.5 mb), temperature (-80, -40, -10, or +23 degrees C), gas composition (Earth-normal N2/O2 mix, pure N2, pure CO2, or a Mars gas mix), and UV-VIS-NIR fluence rates (200-1200 nm) were maintained within tight limits. The Mars gas mix was composed of CO2 (95.3%), N2 (2.7%), Ar (1.7%), O2 (0.2%), and water vapor (0.03%). Experiments were conducted to measure the effects of pressure, gas composition, and temperature alone or in combination with Mars-normal UV-VIS-NIR light environments. Endospores of B. subtilis, were deposited on aluminum coupons as monolayers in which the average density applied to coupons was 2.47 x 10(6) bacteria per sample. Populations of B. subtilis placed on aluminum coupons and subjected to an Earth-normal temperature (23 degrees C), pressure (1013 mb), and gas mix (normal N2/O2 ratio) but illuminated with a Mars-normal UV-VIS-NIR spectrum were reduced by over 99.9% after 30 sec exposure to Mars-normal UV fluence rates. However, it required at least 15 min of Mars-normal UV exposure to reduce bacterial populations on aluminum coupons to non-recoverable levels. These results were duplicated when bacteria were exposed to Mars-normal environments of temperature (-10 degrees C), pressure (8.5 mb), gas composition (pure CO2), and UV fluence rates. In other experiments, results indicated that the gas composition of the atmosphere and the temperature of the bacterial monolayers at the time of Mars UV exposure had no effects on the survival of bacterial endospores. But Mars-normal pressures (8.5 mb) were found to reduce survival by approximately 20-35% compared to Earth-normal pressures (1013 mb). The primary implications of these results are (a) that greater than 99.9% of bacterial populations on sun-exposed surfaces of spacecraft are likely to be inactivated within a few tens of seconds to a few minutes on the surface of Mars, and (b) that within a single Mars day under clear-sky conditions bacterial populations on sun-exposed surfaces of spacecraft will be sterilized. Furthermore, these results suggest that the high UV fluence rates on the martian surface can be an important resource in minimizing the forward contamination of Mars.

Atmospheric Pressure↗

PubMed2000

Research into the effects of astronaut motion on the spacecraft: a review.

The paper reviews the research that has been undertaken to understand and quantify the disturbance effects of the astronaut's motion inside and outside the spacecraft on the vehicle's attitude and acceleratory environment. In early investigations, the dynamic interaction of astronauts, modeled as point masses, and the spacecraft, modelled as a rigid body, was analyzed. Through ground-based experiments and the modeling of astronaut-induced forces and moments as stochastic processes, it became possible to estimate the magnitude and energy content of the loads produced by the astronaut. The first experiment in space to measure the astronaut-induced disturbances was conducted on the Skylab orbital station. Loads generated while performing routine operations were measured on board the Space Shuttle in 1994 and on the space station Mir in 1996-1997.

Acceleration↗

PubMed1999

Adsorption processes in spacecraft environmental control and life support systems.

The environmental control and life support system on a spacecraft maintains a safe and comfortable environment in which the crew can live and work by supplying oxygen and water and by removing carbon dioxide, water vapor, and trace contaminants from cabin air. Although open-loop systems have been used successfully in the past for short-duration missions, the economics of current and future long-duration missions in space will make nearly complete recycling of air and water imperative. A variety of operations will be necessary to achieve the goal of nearly complete recycling. These include separation and reduction of carbon dioxide, removal of trace gas-phase contaminants, recovery and purification of humidity condensate, purification and polishing of wastewater streams, and others. Several of these can be performed totally or in part by adsorption processes. These processes are good candidates to perform separations and purifications in space due to their gravity independence, high reliability, relative high energy efficiency, design flexibility, technological maturity, and regenerative nature. For these reasons, adsorption has historically played a key role in life support on U.S. and Russian piloted spacecraft. Among the life support applications that can be achieved through use of adsorption technology are removal of trace contaminants and carbon dioxide from cabin air and recovery of potable water from waste streams. In each of these cases adsorption technology has been selected for use onboard the International Space Station. The requirements, science, and hardware for these applications are discussed. Human space exploration may eventually lead to construction of planetary habitats. These habitats may provide additional opportunities for use of adsorption processes, such as control of greenhouse gas composition, and may have different resources available to them, such as gases present in the planetary atmosphere. Separation and purification processes based on adsorption can be expected to continue to fulfill environmental control and life support needs on future missions.

Adsorption↗

PubMed1993

A search for life on Earth from the Galileo spacecraft.

In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth. Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence. These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.

Atmosphere↗

PubMed2001

[Optimization analysis of ventilation and dehumidification in manned spacecraft].

OBJECTIVE: To achieve the optimized design of system operational parameters and system components in air ventilation and dehumidification of manned spacecraft. METHOD: Mathematical-physical model of air ventilation and dehumidification system was established. Through the design of optimal operational parameters for system performance, heat and moisture in the cabin of manned spacecraft could be removed effectively, dewing could be prevented, and the comfort demand of the astronauts could be met. Equivalent mass of the system in different operational parameters and system components was analyzed by calculation. RESULT: The dew point temperature and the comfortability depended on the temperature and humidity of the influx, ventilation rate, and evaporation of moisture in the cabin. There were two ways to control the operational parameters of air ventilation and dehumidification system. The method based on controlling temperature didn't use recuperative heat exchangers in the loop, and the system structure for the design was simple, but it didn't meet the requirement of dissipating moisture in some conditions. The other method was based on controlling the moisture, and it could steadily keep the dew point temperature in the cabin and control the occurrence of dew. But the system structure of this design was relatively complex. CONCLUSION: Mass and power consumption of the system could be reduced by selecting appropriate parameters and adopting the measures of optimization.

Air Conditioning↗

PubMed1964

Gnotobiotic techniques and their application to spacecraft fabrication.

Several colonies of rats and mice have been reared totally free of viable microorganisms, some for over 10 years. A variety of other species including monkeys, dogs, sheep and swine have been maintained under the same conditions for shorter periods. This operation requires more precise control of microbic contamination than can be achieved by conventional techniques. The necessary control was realized by the use of apparatus termed "isolators". Obtaining sterility is a biological problem but its maintenance is an engineering problem. The gnotobiotic animal has been shown to be more sensitive to some microbic contamination than in vitro culture media. Apparently complex spacecraft cannot be sterilized effectively by postassembly treatment alone. Therefore, sterile subassemblies must be made as required with final assembly in a sterile environment to avoid trapping viable organisms. This can be accomplished within isolators since there appears to be no size limitations to the apparatus developed for biological and medical applications. Repairs and testing procedures under sterile conditions are possible with the isolator system. Fabrication of spacecraft within closed sterile isolators should present no major engineering problems provided all of the components are sterilizable.

Animals↗

PubMed1966

Microbial contaminants in the interiors of spacecraft components.

The hazard from microbiological contamination in the interiors of components of planetary-impacting spacecraft has been generally recognized, but techniques for experimentally evaluating the significance of this hazard have been unavailable. A goal in sterilizing early Mars-impacting payloads is the elimination of the possibility that a microbial stowaway will cause the extraterrestrial-life detection techniques falsely to indicate existence of Martian life, particularly if none exists. Another goal is the prevention of changes in Martian ecology. Several promising life-detection techniques were evaluated in an experimental study of methods to detect microbial populations inside spacecraft-type materials after pulverization or being dissolved. The type of material inspected has a greater effect on the sensitivity of the detection method than any other parameter studied. Through culturing abraded particles, a bacillus inoculum of 100 spores per milliliter can be detected in solid propellants. Fifty percent of an inoculum can be recovered from some solids soluble in nontoxic solvents. For many of the solids studied, however, the culturing techniques used were unable to detect inoculums of 10(6) spores per milliliter of solid. The techniques other than culturing did not discriminate between living and dead cells. As with products of the food and pharmaceutical industries, assurance of sterility in the final product never rests in a negative sterility test on a copy of the product. A negative sterility test is certainly most meaningful for a product for which a very sensitive sterility test has been developed. When a sensitive final-product sterility test is not available, assurance of sterility depends more heavily on other information such as the manufacturing history of the product.

Bacillus subtilis↗

PubMed2003

[Safety and reliability verification for manned spacecraft crew support facilities].

OBJECTIVE: To verify reliability and safety of the crew support facilities on board manned spacecraft. METHOD: Several comprehensive qualitative and quantitative projection verification technique, such as analysis, check, demonstration, tests and reliability assessment, were used. RESULT: Work-items that were specified in the reliability and safety program were realized. Assurance measures for safety and reliability critical items were available. FMEA and SHA and FTA were brought in all around. Safety and reliability on equipment levels and system levels was fully carried out. CONCLUSION: The facility safety and reliability achieved design specification and met the requirements of spaceflight tests for manned spacecraft.

Ergonomics↗