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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Supercritical CO2 Cleaning for Planetary Protection and Contamination Control

We have designed and built a prototype Supercritical CO? Cleaning (SCC) system at JPL. The key features of the system are: 1) the parts inside a high-pressure vessel can be rotated at high speeds; 2) the same thermodynamic condition is maintained during First-In First-Out flushing to keep solvent power constant; and 3) the boil-off during decompression is induced in a separate vessel downstream. Our goal is to demonstrate SCC's ability to remove trace amounts of microbial and organic contaminants down to parts per billion levels from spacecraft material surfaces for future astrobiology missions. The initial cleaning test results showed that SCC can achieve cleanliness levels of 0.01 microgram/cm(sup 2) or less for hydrophobic contaminants such as dioctyl phthalate and silicone and it is less effective in the removal and inactivation of the hydrophilic bacterial spores as expected. However, with the use of a polar co-solvent, the efficacy may improve dramatically. The same results were obtained using liquid CO?. This opens up the possibility of using subcritical cleaning conditions, which may prove to be more compatible with certain spacecraft hardware.

Lin, Ying↗
NASA NTRS1993

Contamination control and plume assessment of low-energy thrusters

A method for evaluating the effects of gases originating from plumes or other direct sources impinging on sensitive surfaces located within their field of view is presented. The method is applied to an Xe ion plasma generator with a thrust of a few mN located near a cryogenic surface. The method is based on experimentally derived plume descriptions of emitted low-pressure vented gases and test results of plume distributions from a similar ion engine. It is concluded that the plume of the Xe neutrals represented by a cosine squared function of the angle is a possible contamination source for certain surfaces of the spacecraft.

Scialdone, John J.↗
NASA NTRS2012

Contamination Control Assessment of the World's Largest Space Environment Simulation Chamber

The Space Power Facility s thermal vacuum test chamber is the largest chamber in the world capable of providing an environment for space simulation. To improve performance and meet stringent requirements of a wide customer base, significant modifications were made to the vacuum chamber. These include major changes to the vacuum system and numerous enhancements to the chamber s unique polar crane, with a goal of providing high cleanliness levels. The significance of these changes and modifications are discussed in this paper. In addition, the composition and arrangement of the pumping system and its impact on molecular back-streaming are discussed in detail. Molecular contamination measurements obtained with a TQCM and witness wafers during two recent integrated system tests of the chamber are presented and discussed. Finally, a concluding remarks section is presented.

Snyder, Aaron↗
NASA NTRS2009

Reactive Distillation and Air Stripping Processes for Water Recycling and Trace Contaminant Control

Reactive distillation designs are considered to reduce the presence of volatile organic compounds in the purified water. Reactive distillation integrates a reactor with a distillation column. A review of the literature in this field has revealed a variety of functional reactive columns in industry. Wastewater may be purified by a combination of a reactor and a distiller (e.g., the EWRS or VPCAR concepts) or, in principle, through a design which integrates the reactor with the distiller. A review of the literature in reactive distillation has identified some different designs in such combinations of reactor and distiller. An evaluation of reactive distillation and reactive air stripping is presented with regards to the reduction of volatile organic compounds in the contaminated water and air. Among the methods presented, an architecture is presented for the evaluation of the simultaneous oxidation of organics in air and water. These and other designs are presented in light of potential improvements in power consumptions and air and water purities for architectures which include catalytic activity integrated into the water processor. In particular, catalytic oxidation of organics may be useful as a tool to remove contaminants that more traditional distillation and/or air stripping columns may not remove. A review of the current leading edge at the commercial level and at the research frontier in catalytically active materials is presented. Themes and directions from the engineering developments in catalyst design are presented conceptually in light of developments in the nanoscale chemistry of a variety of catalyst materials.

Boul, Peter J.↗
NASA NTRS1972

Contamination control through filtration of microorganisms

A description is given of the various kinds of gas and liquid filters used in decontamination and sterilization procedures. Also discussed are filtration mechanisms, characteristics of filter materials, and the factors affecting filter performance. Summaries are included for filter testing and evaluation techniques and the possible application of the filters to spacecraft sterilization.

Stabekis, P. D.↗
NASA NTRS1972

Contamination control by use of ethylene oxide

The uses of ethylene oxide as a decontaminating agent for planetary quarantine related applications are reported. Aspects discussed include: applications and limitations, chemical and physical properties, germicidal activity, methods of applications, and effects on personnel.

Stroud, R. H.↗
NASA NTRS1976

Contamination control in hybrid microelectronic modules

Thin and thick film test specimens were utilized to study the effects of silicone and epoxy hybrid microcircuit coatings on 0.025 mm diameter aluminum and gold ultrasonic bonds, and 0.051 diameter gold pulsed-thermocompression bonds. Chip-to-substrate and substrate-to-substrate geometries were included. Because sealed packages were utilized, a test pattern design was incorporated that allowed the determination of bond failures by making resistance measurements external to the package after the various environmental tests. All wire bonds were non-destructively pull tested prior to sealing. Tests included the PIN test, temperature cycling, and high temperature storage.

Himmel, R. P.↗
NASA NTRS1984

Contamination control and cleanliness level integrity for the Space Shuttle Orbiter PLB, payloads and facilities at KSC

The PLB, its cargo, and payload canister must satisfy the cleanliness requirements of visual clean (VC) level 1, 2, 3, or special as stated in NASA document SN-C-0005A. The specific level of cleanliness is chosen by the payload bay customer for their mission. During orbiter turnaround processing at KSC, the payload bay is exposed to the environments of the Orbiter Processing Facility (OPF) and the Payload Changeout Room (PCR). In supportive response to the orbiter payload bay/facility interface, it is necessary that the facility environment be controlled and monitored to protect the cleanliness/environmental integrity of the payload bay and its cargo. Techniques used to meet environmental requirements during orbiter processing are introduced.

Bartelson, D.↗
NASA NTRS1988

Wide Field/Planetary Camera (WF/PC) contamination control assessment

The major concern of this study was the formation of a haze on the transmissive optics when exposed to a vacuum environment. The phenomena was determined to be a result of molecular transport from a low outgassing structural adhesive. Detailed analysis, both chemical and analytical, were conducted to assess the formation of the haze. Results of the study are given as well as information on clean-up and problem elimination.

Maag, C.↗
NASA NTRS1990

Contamination control of the Cryogenic Limb Array Etalon Spectrometer

The cleanliness requirements of the Cryogenic Limb Array Etalon Spectrometer (CLAES) are described and the control program is assessed with particular emphasis given to the effects of particulate interference. The use of the CLAES is reviewed, and off-axis scatter from the earth is identified as an important noise source. Since the CLAES altitude of interest causes a low-altitude detection of 0.2 deg above the earth's surface, straylight controls are important in the development of the instrument. The development of off-axis rejection and the particulate-cleanliness level are evaluated in terms of those required for a certain BRDF. The control plan is described, and procedures are outlined including cleaning methods and facilities. The modeling predictions and procedural controls are found to effectively satisfy requirements for low scatter levels and out-of-field view-rejection by maximizing straylight control and allowing a margin against noise-equivalent radiance.

Steakley, B. C.↗
NASA NTRS1994

Hubble Space Telescope servicing mission scientific instrument protective enclosure design requirements and contamination controls

The Scientific Instrument Protective Enclosures were designed for the Hubble Space Telescope Servicing Missions to provide a beginning environment to a Scientific Instrument during ground and on orbit activities. The Scientific Instruments required very stringent surface cleanliness and molecular outgassing levels to maintain ultraviolet performance. Data from the First Servicing Mission verified that both the Scientific Instruments and Scientific Instrument Protective Enclosures met surface cleanliness level requirements during ground and on-orbit activities.

Hansen, Patricia A.↗