Engineering topics

Allton, J. H.

Publications and source records attributed to Allton, J. H..

At least 55 records · Page 3

NASA NTRS2011

Technical Tension Between Achieving Particulate and Molecular Organic Environmental Cleanliness: Data from Astromaterial Curation Laboratories

NASA Johnson Space Center operates clean curation facilities for Apollo lunar, Antarctic meteorite, stratospheric cosmic dust, Stardust comet and Genesis solar wind samples. Each of these collections is curated separately due unique requirements. The purpose of this abstract is to highlight the technical tensions between providing particulate cleanliness and molecular cleanliness, illustrated using data from curation laboratories. Strict control of three components are required for curating samples cleanly: a clean environment; clean containers and tools that touch samples; and use of non-shedding materials of cleanable chemistry and smooth surface finish. This abstract focuses on environmental cleanliness and the technical tension between achieving particulate and molecular cleanliness. An environment in which a sample is manipulated or stored can be a room, an enclosed glovebox (or robotic isolation chamber) or an individual sample container.

Allton, J. H.↗

NASA NTRS2009

Decontaminating Solar Wind Samples with the Genesis Ultra-Pure Water Megasonic Wafer Spin Cleaner

The Genesis sample return capsule, though broken during the landing impact, contained most of the shattered ultra-pure solar wind collectors comprised of silicon and other semiconductor wafers materials. Post-flight analysis revealed that all wafer fragments were littered with surface particle contamination from spacecraft debris as well as soil from the impact site. This particulate contamination interferes with some analyses of solar wind. In early 2005, the Genesis science team decided to investigate methods for removing the surface particle contamination prior to solar wind analysis.

Calaway, Michael J.↗

NASA NTRS2008

Stereomicroscope Inspection of Polished Aluminum Collector 50684.0

The Genesis polished aluminum "kidney" collector was damaged during the hard landing of the capsule on September 8, 2004 in the Utah desert. The kidney was introduced into the Genesis (ISO class 4) cleanroom laboratory on November 4, 2004 and stored under nitrogen cover gas. The collector is currently fastened to a highly polished stainless steel plate for secure handling. Curatorial work at JSC has made successful subdivision and subsequent allocation of samples from the kidney.

Rodriquez, M. C.↗

NASA NTRS2008

Cleaning Genesis Solar Wind Collectors with Ultrapure Water: Residual Contaminant Particle Analysis

Additional experience has been gained in removing contaminant particles from the surface of Genesis solar wind collectors fragments by using megasonically activated ultrapure water (UPW)[1]. The curatorial facility has cleaned six of the eight array collector material types to date: silicon (Si), sapphire (SAP), silicon-on-sapphire (SOS), diamond-like carbon-on-silicon (DOS), gold-on-sapphire (AuOS), and germanium (Ge). Here we make estimates of cleaning effectiveness using image analysis of particle size distributions and an SEM/EDS reconnaissance of particle chemistry on the surface of UPW-cleaned silicon fragments (Fig. 1). Other particle removal techniques are reported by [2] and initial assessment of molecular film removal is reported by [3].

Allton, J. H.↗

NASA NTRS2008

Preliminary Quantification of Image Color Gradient on Genesis Concentrator Silicon Carbine Target 60001

The Genesis spacecraft concentrator was a device to focus solar wind ions onto a 6-cm diameter target area, thus concentrating the solar wind by 20X [1]. The target area was comprised of 4 quadrants held in place by a gold-coated stainless steel "cross" (Fig. 1). To date, two SiC and one chemical vapor deposited (CVD) quadrants have been imaged at 5X using a Leica DM-6000M in autoscan mode. Complete imaging of SiC sample 60001 required 1036 images. The mosaic of images is shown in Fig. 2 and position of analyzed areas in Fig. 3. This mosaic imaging is part of the curatorial documentation of surface condition and mapping of contamination. Higher magnification (50X) images of selected areas of the target and individual contaminant particles are compiled into reports which may be requested from the Genesis Curator [2].

Allton, J. H.↗

NASA NTRS2007

Genesis Contingency Planning and Mishap Recovery: The Sample Curation View

Planning for sample preservation and curation was part of mission design from the beginning. One of the scientific objectives for Genesis included collecting samples of three regimes of the solar wind in addition to collecting bulk solar wind during the mission. Collectors were fabricated in different thicknesses for each regime of the solar wind and attached to separate frames exposed to the solar wind during specific periods of solar activity associated with each regime. The original plan to determine the solar regime sampled for specific collectors was to identify to which frame the collector was attached. However, the collectors were dislodged during the hard landing making identification by frame attachment impossible. Because regimes were also identified by thickness of the collector, the regime sampled is identified by measuring fragment thickness. A variety of collector materials and thin films applied to substrates were selected and qualified for flight. This diversity provided elemental measurement in more than one material, mitigating effects of diffusion rates and/or radiation damage. It also mitigated against different material and substrate strengths resulting in differing effects of the hard landing. For example, silicon crystal substrates broke into smaller fragments than sapphire-based substrates and diamond surfaces were more resilient to flying debris damage than gold. The primary responsibility of the curation team for recovery was process documentation. Contingency planning for the recovery phase expanded this responsibility to include not only equipment to document, but also gather, contain and identify samples from the landing area and the recovered spacecraft. The team developed contingency plans for various scenarios as part of mission planning that included topographic maps to aid in site recovery and identification of different modes of transport and purge capability depending on damage. A clean tent, set-up at Utah Test & Training Range to control the environment for processing the sample return capsule and cleanly installing a nitrogen purge to the canister, was used to control the environment for extracting collector fragments from the damaged canister and to document and package over 10,000 collector fragments.

Stansbery, E. K.↗

NASA NTRS2007

Clean Assembly of Genesis Collector Canister for Flight: Lessons for Planetary Sample Return

Measurement of solar composition in the Genesis collectors requires not only high sensitivity but very low blanks; thus, very strict collector contamination minimization was required beginning with mission planning and continuing through hardware design, fabrication, assembly and testing. Genesis started with clean collectors and kept them clean inside of a canister. The mounting hardware and container for the clean collectors were designed to be cleanable, with access to all surfaces for cleaning. Major structural components were made of aluminum and cleaned with megasonically energized ultrapure water (UPW). The UPW purity was >18 M resistivity. Although aluminum is relatively difficult to clean, the Genesis protocol achieved level 25 and level 50 cleanliness on large structural parts; however, the experience suggests that surface treatments may be helpful on future missions. All cleaning was performed in an ISO Class 4 (Class 10) cleanroom immediately adjacent to an ISO Class 4 assembly room; thus, no plastic packaging was required for transport. Persons assembling the canister were totally enclosed in cleanroom suits with face shield and HEPA filter exhaust from suit. Interior canister materials, including fasteners, were installed, untouched by gloves, using tweezers and other stainless steel tools. Sealants/lubricants were not exposed inside the canister, but vented to the exterior and applied in extremely small amounts using special tools. The canister was closed in ISO Class 4, not to be opened until on station at Earth-Sun L1. Throughout the cleaning and assembly, coupons of reference materials that were cleaned at the same time as the flight hardware were archived for future reference and blanks. Likewise reference collectors were archived. Post-mission analysis of collectors has made use of these archived reference materials.

Allton, J. H.↗

NASA NTRS2007

Genesis Concentrator Target Particle Contamination Mapping and Material Identification

The majority of surface particles were found to be < 5 microns in diameter with increasing numbers close to the optical resolution limit of 0.3 microns. Acceleration grid EDS results show that the majority of materials appear to be from the SRC shell and SLA materials which include carbon-carbon fibers and Si-rich microspheres in a possible silicone binder. Other major debris material from the SRC included white paint, kapton, collector array fragments, and Al. Image analysis also revealed that SRC materials were also found mixed with the Utah mud and salt deposits. The EDS analysis of the acceleration grid showed that particles < 1 m where generally carbon based particles. Chemical cleaning techniques with Xylene and HF in an ultrasonic bath are currently being investigated for removal of small particles by the Genesis science team as well as ultra-pure water megasonic cleaning by the JSC team [4]. Removal of organic contamination from target materials is also being investigated by the science team with the use of UV-ozone cleaning devices at JSC and Open University [5]. In preparation for solar wind oxygen analyses at UCLA and Open University [1, 2], surface particle contamination on three Genesis concentrator targets was closely examined to evaluate cleaning strategies. Two silicon carbide (Genesis sample # 60001 and 60003) and one chemical vapor deposited (CVD) 13C concentrator target (60002) were imaged and mosaic mapped with optical microscopes. The resulting full target mosaic images and particle feature maps were subsequently compared with non-flight, but flight-like, concentrator targets and sample return capsule (SRC) materials. Contamination found on the flown concentrator acceleration grid was further examined using a scanning electron microscope (SEM). Energy dispersive X-ray spectroscopy (EDS) for particle identification was subsequently compared with the optical images from the flown targets. Figure 1 show that all three targets imaged in this report are fully intact and do not show any signs of material fractures. However, previous ellipsometry results and overview imaging of both flown SiC targets show a solar wind irradiation gradient from the center focal point to the outer edge [3]. In addition, due to the hard landing, each target has experienced varying degrees of impacts, scratches, and particle debris from the spacecraft and Utah impact site.

Calaway, Michael J.↗

NASA NTRS2007

Decontamination of Genesis Array Materials by UV Ozone Cleaning

Shortly after the NASA Genesis Mission sample return capsule returned to earth on September 8, 2004, the science team discovered that all nine ultra-pure semiconductor materials were contaminated with a thin molecular organic film approximately 0 to 100 angstroms thick. The organic contaminate layer, possibly a silicone, situated on the surface of the materials is speculated to have formed by condensation of organic matter from spacecraft off-gassing at the Lagrange 1 halo orbit during times of solar exposure. While the valuable solar wind atoms are safely secured directly below this organic contamination and/or native oxide layer in approximately the first 1000 angstroms of the ultra-pure material substrate, some analytical techniques that precisely measure solar wind elemental abundances require the removal of this organic contaminate. In 2005, Genesis science team laboratories began to develop various methods for removing the organic thin film without removing the precious material substrate that contained the solar wind atoms. Stephen Sestak and colleagues at Open University first experimented with ultraviolet radiation ozone (UV/O3) cleaning of several non-flight and flown Genesis silicon wafer fragments under a pure flowing oxygen environment. The UV/O3 technique was able to successfully remove organic contamination without etching into the bulk material substrate. At NASA Johnson Space Center Genesis Curation Laboratory, we have installed an UV/O3 cleaning devise in an ambient air environment to further experimentally test the removal of the organic contamination on Genesis wafer materials. Preliminary results from XPS analysis show that the UV/O3 cleaning instrument is a good non-destructive method for removing carbon contamination from flown Genesis array samples. However, spectroscopic ellipsometry results show little change in the thickness of the surface film. All experiments to date have shown UV/O3 cleaning method to be the best non-destructive method for removing organic contamination from the surface of the Genesis materials. The UV/O3 cleaning process can also clean carbon contamination to levels below non-flight standards. This can be seen by comparing sample 60260's carbon 10667 cps with non-flight Si carbon 21675 cps. Therefore, surface carbon contamination should not hinder the analysis of solar wind.

Calaway, Michael J.↗

NASA NTRS2007

Organics in APOLLO Lunar Samples

One of many unknowns prior to the Apollo landings concerned the possibility of life, its remains, or its organic precursors on the surface of the Moon. While the existence of lunar organisms was considered highly unlikely, a program of biological quarantine and testing for the astronauts, the Apollo Command Modules, and the lunar rock and soil samples, was instituted in the Lunar Receiving Laboratory (LRL). No conclusive evidence of lunar organisms, was detected and the quarantine program was ended after Apollo 14. Analyses for organic compounds were also con-ducted. Considerable effort was expended, during lunar surface operations and in the LRL, to minimize and quantify organic contamination. Post-Apollo curatorial operations and cleaning minimize contamination from particulates, oxygen, and water but no longer specifically address organic contamination. The organic compounds measured in Apollo samples are generally consistent with known sources of contamination.

Allen, C. C.↗

NASA NTRS2006

Cleaning Surface Particle Contamination with Ultrapure Water (UPW) Megasonic Flow on Genesis Array Collectors

The hard landing experienced by the Genesis sample return capsule breached the science canister containing the solar wind collectors. This impact into the damp lakebed contaminated collector surfaces with pulverized collector and spacecraft materials and Utah sediment and brine residue. The gold foil, polished aluminum, and bulk metallic glass remained intact, but the solar wind bulk and regime-specific array collectors were jarred loose from their frames and fractured into greater than 10,000 specimens. After a year of investigation and cleaning experimentation, the Genesis Science Team determined that array collectors had 4 classes of contaminants: particles, molecular film, submicron inorganic particulate ("aerosol"), and pre-launch surface contamination. We discuss here use of megasonically energized ultrapure water (UPW) for removing particulate debris from array collector fragments.

Allton, J. H.↗

NASA NTRS2006

Genesis Spacecraft Science Canister Preliminary Inspection and Cleaning

The Genesis science canister is an aluminum cylinder (75 cm diameter and 35 cm tall) hinged at the mid-line for opening. This canister was cleaned and assembled in an ISO level 4 (Class 10) clean room at Johnson Space Center (JSC) prior to launch. The clean solar collectors were installed and the canister closed in the cleanroom to preserve collector cleanliness. The canister remained closed until opened on station at Earth-Sun L1 for solar wind collection. At the conclusion of collection, the canister was again closed to preserve collector cleanliness during Earth return and re-entry. Upon impacting the dry Utah lakebed at 300 kph the science canister integrity was breached. The canister was returned to JSC. The canister shell was briefly examined, imaged, gently cleaned of dust and packaged for storage in anticipation of future detailed examination. The condition of the science canister shell noted during this brief examination is presented here. The canister interior components were packaged and stored without imaging due to time constraints.

Hittle, J. D.↗

NASA NTRS2005

Size Distribution of Genesis Solar Wind Array Collector Fragments Recovered

Genesis launched in 2001 with 271 whole and 30 half hexagonally-shaped collectors mounted on 5 arrays, comprised of 9 materials described in [1]. The array collectors were damaged during re-entry impact in Utah in 2004 [2], breaking into many smaller pieces and dust. A compilation of the number and approximate size of the fragments recovered was compiled from notes made during the field packaging performed in the Class 10,000 cleanroom at Utah Test and Training Range [3].

Allton, J. H.↗

NASA NTRS2005

Initial Subdivision of Genesis Early Science Polished Aluminum Collector

A large surface, about 245 square centimeters, of highly polished aluminum 6061 T6 alloy was attached to the science canister thermal panel for the purpose of collecting solar wind noble gases. The analysis of this collector will be part of the Genesis Early Science results. The pre-launch configuration of the collector is shown. The collector sustained some damage during the recovery impact in Utah, September 8, 2004.

Allton, J. H.↗

NASA NTRS2005

Genesis: Removing Contamination from Sample Collectors

The Genesis mission returned to Earth on September 8, 2004, experiencing a non-nominal reentry. The parachutes which were supposed to slow and stabilize the capsule throughout the return failed to deploy, causing the capsule to impact the desert floor at a speed of nearly 200 MPH. Both the science canister and the major components of the SRC were returned before nightfall on September 8 to the prestaged cleanroom at UTTR , avoiding prolonged exposure or pending weather changes which might further contaminate the samples. The majority of the contaminants introduced as a result of the anomalous landing were in the form of particulates, including UTTR dust and soil, carbon-carbon heat shield material, and shattered collector dust (primarily silicon and germanium). Additional information is included in the original extended abstract.

Lauer, H. V.↗

NASA NTRS2005

Status of Genesis Mo-Pt Foils

A total of 8,000 sq cm of Mo-coated Pt foils were exposed to solar wind for 884 days by the Genesis mission. Solar wind ions were captured in the surface of the Mo. Our objective is the measurement of long-lived radionuclides, such as Be-10, Al-26, Cl-36, and Mn-53, and short-lived radionuclides, such as Na-22 and Mn-54, in the captured sample of solar wind. The expected flux of these nuclides in the solar wind is 100 atom/sq cm yr or less. The hard landing of the SRC (Sample Return Capsule) at UTTR (Utah Test and Training Range) has resulted in contaminated and crumpled foils. Here we present a status report and revised plan for processing the foils.

Nishiizumi, K.↗

NASA NTRS2003

A Future Moon Mission: Curatorial Statistics on Regolith Fragments Applicable to Sample Collection by Raking

The strategy of raking rock fragments from the lunar regolith as a means of acquiring representative samples has wide support due to science return, spacecraft simplicity (reliability) and economy [3, 4, 5]. While there exists widespread agreement that raking or sieving the bulk regolith is good strategy, there is lively discussion about the minimum sample size. Advocates of consor-tium studies desire fragments large enough to support petrologic and isotopic studies. Fragments from 5 to 10 mm are thought adequate [4, 5]. Yet, Jolliff et al. [6] demonstrated use of 2-4 mm fragments as repre-sentative of larger rocks. Here we make use of cura-torial records and sample catalogs to give a different perspective on minimum sample size for a robotic sample collector.

Allton, J. H.↗

NASA NTRS2003

Genesis Discovery Mission: Science Canister Processing at JSC

Genesis addresses questions about materials and processes involved in the origins of the solar system by providing precise knowledge of solar isotopic and elemental compositions. Solar wind ions are collected and returned to Earth for analyses. The spacecraft has two primary instruments to collect solar wind: a set of collector arrays each of which can deploy to sample different solar wind regimes, and a concentrator that is an electrostatic mirror to concentrate and focus low mass ions onto a 6 cm target. One of the key challenges to obtaining a good sample of solar wind, uncontaminated by terrestrial atoms, is to have clean collection surfaces in a clean sample canister and clean facilities to handle the samples for allocation and future reference. The Johnson Space Center (JSC) is responsible for contamination control for the mission, for ensuring the cleanliness of collection surfaces, and for providing a clean environment for handling of the samples. The level of cleanliness required is high; at the time of analysis (after sample return), the surface contamination by C, N, O must each be <10(exp 15) atoms/sq cm and for other elements the number of atoms/sq cm of each surface contaminant shall not exceed the estimated solar wind fluence of the species (varies by element between U at approx. 10(exp 4) atoms/sq cm to Fe, Si, Mg, and Ne at approx. 10(exp 12) atoms/sq cm).

Stansbery, E. K.↗