Engineering topics

James, John

Publications and source records attributed to James, John.

6 records

NASA NTRS2006

Airborne Dust in Space Vehicles and Habitats

Airborne dust, suspended inside a space vehicle or in future celestial habitats, can present a serious threat to crew health if it is not controlled. During the Apollo missions to the moon, lunar dust brought inside the capsule caused eye irritation and breathing difficulty to the crew when they launched from the moon and re-acquired "microgravity." During Shuttle flights reactive and toxic dusts such as lithium hydroxide have created a risk to crew health, and fine particles from combustion events can be especially worrisome. Under nominal spaceflight conditions, airborne dusts and particles tend to be larger than on earth because of the absence of gravity settling. Aboard the ISS, dusts are effectively managed by HEPA filters, although floating dust in newly-arrived modules can be a nuisance. Future missions to the moon and to Mars will present additional challenges because of the possibility that external dust will enter the breathing atmosphere of the habitat and reach the crew's respiratory system. Testing with simulated lunar and Martian dust has shown that these materials are toxic when placed into the lungs of test animals. Defining and evaluating the physical and chemical properties of Martian dusts through robotic missions will challenge our ability to prepare better dust simulants and to determine the risk to crew health from exposure to such dusts.

James, John↗

NASA NTRS2000

Pulmonary Toxicity of Simulated Lunar and Martian Dusts Intratracheally Instilled into Mice

The National Aeronautics and Space Administration (NASA) is contemplating sending humans to Mars and to the Moon for further exploration. Equipment designated for these extraterrestrial bases will require testing in simulated Martian or lunar environments. The properties of Hawaiian and San Francisco Mountain volcanic ashes make them suitable to be used in these test environments as Martian and lunar dust simulants, respectively. The present toxicity study was conducted to address NASA's concern about the health risk of dust exposures in the test facilities. In addition, the results obtained on these simulants can be used to design a toxicity study of actual moon dust and Martian dust, which will probably be available in a few years. Respirable portions of lunar soil simulant (LSS) and Martian soil simulant (MSS) were separated from their respective raw materials. These soil simulants, together- with fine titanium dioxide (negative control for fibrogenesis in mice), and crystalline silica (positive control) were each intratracheally instilled in saline to groups of 4 male mice (C57BL/6J, 2-3 months old) at 0.1 mg/mouse (LD) or lmg/mouse (HD). The lungs were harvested 7 or 90 days after the single dust treatment for histopathological examination. Lungs of the LSS-LD groups on either the 7- or 90-day study showed no evidence of inflammation, edema, or fibrosis. Clumps of particles and an increased number of macrophages, visible in the lungs examined after 7 days, were absent after 90 days. The LSS-HD-7d group showed mild to moderate alveolitis with neutrophilic and lymphocytic infiltration, and mild perivascular and peribronchiolar inflammation. The LSS-HD-90d group showed signs of chronic inflammation: septal thickening, mild perivascular and peribronchiolar inflammation, mild alveolitis and some fibrosis. Foci of particle-laden macrophages (PLMs) were still visible. Lungs of the MSS-LD-7d group revealed mild focal intraalveolar inflammation with neutrophilic and lymphocytic infiltration, and mild perivascular and peribronchiolar inflammation. The MSS-LD-90d group showed PLMs and scattered foci of mild fibrosis. The MSS-HD-7d group showed large foci of PLMs, intraalveolar debris, mild to moderate focal alveolitis, and mild to moderate perivascular and peribronchiolar inflammation. The MSS-HD-90d group showed focal chronic mild to moderate alveolitis and fibrosis. To mimic the oxidative and reactive properties of Martian surface dust in the test animals, groups of 4 mice were exposed to ozone (0.5 ppm for 3 hours) prior to instillation of the MSS. Lung lesions in the MSS groups were more severe with the ozone pretreatment. The O3-MSS-HD-90d group had wide spread intraalveolar debris, focal moderate alveolitis and fibrosis. The results for the titanium dioxide and quartz controls were consistent with the known pulmonary toxicity of these compounds. The overall severity of toxic injury to the lungs was TiO2<LSS<MSS<MSS+O3<quartz. In general, the toxic responses increased with the increase of dust burden in the lung. Except for TiO2, the increased duration of dust presence in the lung from 7 to 90 days transformed the acute inflammatory response to a chronic inflammatory lesion.

Lam, Chiu-Wing↗

NASA NTRS1999

Environmental Health

The Environmental Health activity for the Extended Duration Orbiter Medical Project (EDOMP) was formed to develop an overall strategy for safeguarding crew members from potential airborne hazards anticipated on missions of extended duration. These efforts were necessary because of major modifications to the air revitalization system of the U.S. Space Shuttle and an increased potential for environmental health risks associated with longer space flights. Degradation of air quality in the Shuttle during a space flight mission has the potential to affect the performance of the crew not only during piloting, landing, or egress, but also during space flight. It was anticipated that the risk of significant deterioration in air quality would increase with extended mission lengths and could result from: (1) a major chemical contamination incident, such as a thermodegradation event or toxic leak, (2) continual accumulation of volatile organic compounds to unacceptable levels, (3) excessive levels of airborne particles, (4) excessive levels of microorganisms, or (5) accumulation of airborne pathogens.

Pierson, Duane↗

NASA NTRS1992

First entry operations for spacecraft

First entry procedures implemented in the industrial setting are considered to identify those applicable to the situation on the SSF. Particular attention is given to consequences when these procedures are not followed. Operational scenarios for nominal first entry procedures intended to verify air quality before the crew enters the module are outlined. Components of the Environmental Health System will provide necessary monitoring capability to protect crew health and safety during the planned first entry procedures of the man-tended capability phase of the SSF program. It is apparent that first-entry scenarios have drawn heavily upon industry experience, tempered with the specific characteristics of the space flight environment.

Wilson, Steven↗

NASA NTRS1992

A Volatile Organic Analyzer for Space Station - Description and evaluation of a gas chromatography/ion mobility spectrometer

An on-board Volatile Organic Analyzer (VOA), an essential component of the Environmental Health System (EHS) air-quality monitoring strategy, is described. The strategy is aimed at warning the crew and ground personnel if volatile compounds exceed safe exposure limits. The VOA uses a combination of gas chromatography (GC) and ion-mobility spectrometry (IMS) for environmental monitoring and analysis. It is concluded that the VOA dual-mode detection capability and the ion mobilities in the drift region are unique features that can assist in the resolution of coeluting GC peaks. The VOA is capable of accurately identifying and quantifying target compounds in a complex mixture.

Limero, Thomas↗

NASA NTRS1992

The role of Environmental Health System air quality monitors in Space Station Contingency Operations

This paper describes the Space Station Freedom (SSF) Environmental Health System's air-quality monitoring strategy and instrumentation. A two-tier system has been developed, consisting of first-alert instruments that warn the crew of airborne contamination and a volatile organic analyzer that can identify volatile organic contaminants in near-real time. The strategy for air quality monitoring on SSF is designed to provide early detection so that the contamination can be confined to one module and so that crew health and safety can be protected throughout the contingency event. The use of air-quality monitors in fixed and portable modes will be presented as a means of following the progress of decontamination efforts and ensuring acceptable air quality in a module after an incident. The technology of each instrument will be reviewed briefly; the main focus of this paper, however, will be the use of air-quality monitors before, during, and after contingency incidents.

Limero, Thomas F.↗