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246 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Detection of Chemical Precursors of Explosives

Certain selected chemicals associated with terrorist activities are too unstable to be prepared in final form. These chemicals are often prepared as precursor components, to be combined at a time immediately preceding the detonation. One example is a liquid explosive, which usually requires an oxidizer, an energy source, and a chemical or physical mechanism to combine the other components. Detection of the oxidizer (e.g. H2O2) or the energy source (e.g., nitromethane) is often possible, but must be performed in a short time interval (e.g., 5 15 seconds) and in an environment with a very small concentration (e.g.,1 100 ppm), because the target chemical(s) is carried in a sealed container. These needs are met by this invention, which provides a system and associated method for detecting one or more chemical precursors (components) of a multi-component explosive compound. Different carbon nanotubes (CNTs) are loaded (by doping, impregnation, coating, or other functionalization process) for detecting of different chemical substances that are the chemical precursors, respectively, if these precursors are present in a gas to which the CNTs are exposed. After exposure to the gas, a measured electrical parameter (e.g. voltage or current that correlate to impedance, conductivity, capacitance, inductance, etc.) changes with time and concentration in a predictable manner if a selected chemical precursor is present, and will approach an asymptotic value promptly after exposure to the precursor. The measured voltage or current are compared with one or more sequences of their reference values for one or more known target precursor molecules, and a most probable concentration value is estimated for each one, two, or more target molecules. An error value is computed, based on differences of voltage or current for the measured and reference values, using the most probable concentration values. Where the error value is less than a threshold, the system concludes that the target molecule is likely. Presence of one, two, or more target molecules in the gas can be sensed from a single set of measurements.

Li, Jing↗
NASA NTRS2014

Global and Regional Impacts of HONO on the Chemical Composition of Clouds and Aerosols

Recently, realistic simulation of nitrous acid (HONO) based on the HONO/NO(sub x) ratio of 0.02 was found to have a significant impact on the global budgets of HO(sub x) (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation.

HONO↗
NASA NTRS2015

Genesis Solar Wind Sample 61422: Experiment in Variation of Sequence of Cleaning Solvent for Removing Carbon-Bearing Contamination

The recovered Genesis collector fragments are heavily contaminated with crash-derived particulate debris. However, megasonic treatment with ultra-pure-water (UPW; resistivity (is) greater than18 meg-ohm-cm) removes essentially all particulate contamination greater than 5 microns in size [e.g.1] and is thus of considerable importance. Optical imaging of Si sample 60336 revealed the presence of a large C-rich particle after UPW treatment that was not present prior to UPW. Such handling contamination is occasionally observed, but such contaminants are normally easily removed by UPW cleaning. The 60336 particle was exceptional in that, surprisingly, it was not removed by additional UPW or by hot xylene or by aqua regia treatment. It was eventually removed by treatment with NH3-H2O2. Our best interpretation of the origin of the 60336 particle was that it was adhesive from the Post-It notes used to stabilize samples for transport from Utah after the hard landing. It is possible that the insoluble nature of the 60336 particle comes from interaction of the Post-It adhesive with UPW. An occasional bit of Post-It adhesive is not a major concern, but C particulate contamination also occurs from the heat shield of the Sample Return Capsule (SRC) and this is mixed with inorganic contamination from the SRC and the Utah landing site. If UPW exposure also produced an insoluble residue from SRC C, this would be a major problem in chemical treatments to produce clean surfaces for analysis. This paper reports experiments to test whether particulate contamination was removed more easily if UPW treatment was not used.

Allton, J. H.↗
NASA NTRS2014

Global and Regional Impacts of HONO on the Chemical Composition of Clouds and Aerosols

Recently, realistic simulation of nitrous acid (HONO) based on the HONO / NOx ratio of 0.02 was found to have a significant impact on the global budgets of HOx (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation

Global and regional impacts↗
NASA NTRS2017

Vertical Profiles of Mars 1.27 Micrometer O2 Dayglow from MRO CRISM Limb Spectra: Seasonal/global Behaviors, Comparisons to LMDGCM Simulations, and a Global Definition for Mars Water Vapor Profiles

Since July of 2009, The Compact Reconnaissance Imaging Spectral Mapper (CRISM) onboard the Mars Re- connaissance Orbiter (MRO) has periodically obtained pole-to-pole observations (i.e., full MRO orbits) of limb scanned visible/near IR spectra (lambda= 0.4 - 4.0 micrometers, delta lambda approx. 10 nm- Murchie et al., 2007). These CRISM limb observations support the first seasonally and spatially extensive set of Mars 1.27 micometers O2 (1 delta(sub g)) day-glow profile retrievals (approx. 1100) over greater than or equal to 8-80 km altitudes. Their comparison to Laboratoire de Meteorologie Dynamique (LMD) global climate model (GCM) simulated O2 (1 delta(sub g)) volume emission rate (VER) profiles, as a function of altitude, latitude, and season (solar longitude, L(sub s), supports several key conclusions regarding Mars atmospheric water vapor (which is derived from O2 (1 delta(sub g)) emission rates), Mars O3, and the collisional de-excitation of O2 (1 delta(sub g)) in the Mars CO2 atmosphere. Current (Navarro et al., 2014) LMDGCM simulations of Mars atmospheric water vapor fall 2-3 times below CRISM derived water vapor abundances at 20-40 km altitudes over low-to-mid latitudes in northern spring (L(sub s) = 30-60 deg), and northern mid-to-high latitudes over northern summer (L(sub s) = 60-140 deg). In contrast, LMDGCM simulated water vapor is 2-5 times greater than CRISM derived values at all latitudes and seasons above 40 km, within the aphelion cloud belt (ACB), and over high-southern to mid-southern latitudes in southern summer (L(sub s) = 190-340 deg) at 15-35 km altitudes. Overall, the solstitial summer-to-winter hemisphere gradients in water vapor are reversed between the LMDGCM modeled versus the CRISM derived water vapor abundances above 10-30 km altitudes. LMDGCM-CRISM differences in water vapor profiles correlate with LMDGCM-CRISM differences in cloud mixing profiles; and likely reflect limitations in simulating cloud microphysics and radiative forcing, both of which restrict meridional transport of water from summer- to-winter hemispheres on Mars (Clancy et al., 1996; Montmessin et al., 2004; Steele et al., 2014; Navarro et al., 2014) and depend on uncertain cloud microphysical properties (Navarro et al., 2014). The derived low-to-mid latitude changes in Mars water vapor vertical distributions should reduce current model- data disagreements in column O3 and H2O2 abundances over low-to-mid latitudes (e.g., within the ACB; Lefevre et al., 2008; Encrenaz et al., 2015; Clancy et al., 2016). Lastly, the global/seasonal average com- parison of CRISM and LMDGCM O2 (1 delta(sub g)) VER below 20 km altitudes indicates a factor of approx. 3 times lower value (0.25 x 10(exp -20) cu cm sec(exp -1)) for the CO2 collisional de-excitation rate coefficient of O2 (1 delta(sub g)) than derived recently by Guslyakova et al. (2016).

Clancy, R. Todd↗
NASA NTRS2019

Picture this SELFI: Submillimeter Enceladus Life Fundamentals Instrument

The Submillimeter Enceladus Life Fundamentals Instrument (SELFI) is a passive remote sensing submillimeter heterodyne spectrometer being developed at NASA GSFC under NASA's Maturation of Instruments for Solar System Exploration (MatISSE) program. SELFI will advance submillimeter receiver technology by 1) investigating the chemical and isotopic compositions and corresponding densities of Enceladus' plume material, their vertical thermal structures, and the transport mechanisms within the plumes, and 2) characterizing the source regions from which the plumes emerge. The Enceladus plumes are important in the context of life and habitability of its subsurface ocean environment. SELFI remote sensing measurements will 1) measure the spatial and temporal variabilities in the plume chemical compositions, 2) provide insight in to Enceladus' subsurface ocean environment by monitoring H2O, HDO, d18O, and d17O, 3) constrain the oxidation state of the subsurface ocean using H2O2 and O3, and 4) utilize the SO2 and H2S spectral signatures to constrain the impact arising from both the sea-floor volcanoes and pre-biotic molecules. Moreover, the detection of the remaining molecular species (14 in total) is vital to improving the current state of knowledge of Enceladus' subsurface ocean habitability this also permits us to explore the chemical alteration processes arising from primordial volatiles that have been observed in comets. Lastly, SELFI's continuum observations enable the correlation between observed variations in plume activity with surface temperatures.SELFI is currently being developed under a technology maturation program that will advance the RF-to-digital electronics of a submillimeter-wave heterodyne spectrometer to simultaneously observe fourteen molecular species with resonances between 530 GHz and 600 GHz. SELFI will have fine radiometric resolution, high spectral resolution (resolving power R > 106), multiple continuum channels and a high dynamical range, necessary to map Enceladus across its 30 K to 250 K temperature range. Under the MatISSE program, SELFI will advance from TRL 4 to 6 four key technologies of the RF-to-digital subsystem, which are: 1) the RF low noise amplifier design; 2) the single-sideband (SSB) mixer and local oscillator; 3) the IF assembly down-converter that maps the fourteen species to 2 x 500 MHz bandwidth; and 4) the digital spectrometer electronics.

Racette, Paul↗
NASA NTRSDate not supplied

Radiocatalyst for Radiation Protection and Microbial Control

Radiocatalysts are materials that reduce the activation energy required to split water into hydrogen and reactive oxygen species (ROS). They are activated by radiation and can be used to improve the ability of water to act as a radiation barrier. This paper reports the results of an experimental evaluation of a gold radiocatalyst. This work provides a preliminary evaluation of the ability of these types of catalysts to increase the efficiency of water hydrolysis when exposed to different types of radiation (GCR). Although the radiation exposure devices used in this testing were not capable of generating radiation as diverse as is commonly found in space, the testing is useful in evaluating the function of these radiocatalytic nanoparticles when exposed to a a subset of the types of radiation that are found in GCR. The results are relevant to evaluating the use of this material for both space radiation protection and the production of useful byproducts, such as ROS, which can be used to maintain the sterility of stored water supplies. Radiocatalysts are materials typically used in radiation cancer therapy to improve the kill rate of tumors. These nanoparticles can be directly injected into tumors or functionalized to enter tumor cells via the blood stream. When they are exposed to radiation, they produce ROS. ROS are water hydrolysis products such as OH¯, O¯, O3, H2O2. This study used radiocatalytic 1.8 nm gold nanoparticles functionalized with citrate. These nanoparticles were tested through exposure to Xrays, 56Fe particles and gamma rays to demonstrate activity to a variety of radiation sources. The results demonstrate that radiocatalysts can improve the radiation absorption of water by a factor of 3 to 8 and can effectively kill bacteria at radiation levels above 1 Gy.

radiocatalyst radiation protection biocide↗
NASA NTRS2023

Heterogeneity and Chemical Reactivity of the Remote Troposphere Defined By Aircraft Measurements - Corrected

The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic oceans. In this paper we present and analyze a data set of 10 s (2 km) merged and gap-filled observations of the key reactive species driving the chemical budgets of O3 and CH4 (O3, CH4, CO, H2O, HCHO, H2O2, CH3OOH, C2H6, higher alkanes, alkenes, aromatics, NOx, HNO3, HNO4, peroxyacetyl nitrate, and other organic nitrates), consisting of 146 494 distinct air parcels from ATom deployments 1 through 4. Six models calculated the O3 and CH4 photochemical tendencies from this modeling data stream for ATom 1. We find that 80 %–90 % of the total reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies that tropospheric chemistry is driven by a fraction of all the air. Surprisingly, the probability densities of species and reactivities averaged on a model scale (100 km) differ only slightly from the 2 km ATom 10 s data, indicating that much of the heterogeneity in tropospheric chemistry can be captured with current global chemistry models. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find generally good agreement with the reactivity rates for O3 and CH4. Models distinctly underestimate O3 production below 2 km relative to the mid-troposphere, and this can be traced to lower NOx levels than observed. Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation.

Tropospheric Chemistry↗
NASA NTRS2023

Tunable Laser Spectrometers for Planetary Science

Distinguishing planetary formation and evolution pathways and understanding the origins of volatiles on planetary bodies requires determination of relative abundances and isotope ratios in the noble gases, and also of the isotope ratios in C, H, N, O and S at high precisions. Traditional planetary mass spectrometers uniquely provide excellent survey capability including the noble gas relative abundances and their isotope ratios. However, to distinguish planetary evolution models for the outer planets, stable isotope ratios in C and O require precisions of ∼10 or better, readily achievable with a tunable laser spectrometer (TLS). As demonstrated on the Mars Curiosity rover, and as planned for a now-selected NASA Venus mission, tunable laser spectrometers play a unique role synergistic with the capabilities of planetary mass spectrometers. The TLS technique of recording infrared absorption spectra at ultrahigh resolution (resolving power λ/δλ ∼ 5 million) provides unambiguous detection of a wide variety of gases such as H2O, H2O2, H2CO, HOCl, NO, NO2, HNO3, N2O, O3, CO, CO2, NH3, N2H4, PH3, H2S, SO2, OCS, HCl, HF, O2, HCN, and CH4, C2H2, C2H4, C2H6 at parts-per-billion levels. Through line-depth or line-area ratio comparisons of adjacent spectral lines, planetary TLS instruments can achieve isotope ratio measurements in C, H, N, O, and S molecules at precisions of ∼1–2, including for the triple isotope components of O and S. Expected performance of TLS instruments for Venus, Saturn, Enceladus and Uranus will be described as constrained by actual measurements reported at Mars on the Curiosity rover.

Planetary↗
NASA NTRSDate not supplied

Additive Manufacturing and Experimental Characterization of Nickel-Titanium Shape-Memory Alloy Wick Structures and Heat Pipes for Spacecraft Thermal Control

Shape memory alloys (SMA), such as those based on nickel-titanium (NiTi), are increasingly being applied as multifunctional spacecraft components. For thermal management applications, NiTi flow tubing hinges and self-deploying loop heat pipes have been demonstrated. Emerging additive manufacturing (AM) processes are enabling more complex SMA devices than can be formed from conventional plain wire, tubing, and sheet stock materials. This paper presents our progress toward applying powder bed fusion AM to producing porous NiTi wicks and NiTi-H2O heat pipes, which could be embedded in thermally deploying radiators for spacecraft thermal management. AM near-equiatomic NiTi (55.1 wt% Ni) porous wick specimens were produced with a range of deposition parameters. Transient acetone rate-of-rise experiments were performed to estimate wick permeability (K) and average pore radius (r_pore) values and identify parameter sets with high capillary performance. Surface treatments were evaluated to achieve hydrophilic wick structures. Evaluated treatments included chemical oxide growth with H2O2, oxide and sodium titanate growth with NaOH solution, and ultrasonic cleaning with specialty detergents that can remove hydrocarbon contaminants. The most durable hydrophilic surface conditions were obtained with the NaOH treatment. High performing wick deposition parameters were used to produce a full AM NiTi heat pipe, which was treated with NaOH solution to activate the wick. This heat pipe was operated on a test stand in the inverted configuration (upper evaporator and lower condenser), and demonstrated stable nearly isothermal operation for 150 hrs.

Thermal management↗
NASA NTRSDate not supplied

Additive Manufacturing and Experimental Characterization of Nickel-Titanium Shape-Memory Alloy Wick Structures and Heat Pipes for Spacecraft Thermal Control

Shape memory alloys (SMA), such as those based on nickel-titanium (NiTi), are increasingly being applied as multifunctional spacecraft components. For thermal management applications, NiTi flow tubing hinges and self-deploying loop heat pipes have been demonstrated. Emerging additive manufacturing (AM) processes are enabling more complex SMA devices than can be formed from conventional plain wire, tubing, and sheet stock materials. This paper presents our progress toward applying powder bed fusion AM to producing porous NiTi wicks and NiTi-H2O heat pipes, which could be embedded in thermally deploying radiators for spacecraft thermal management. AM near-equiatomic NiTi (55.1 wt% Ni) porous wick specimens were produced with a range of deposition parameters. Transient acetone rate-of-rise experiments were performed to estimate wick permeability (K) and average pore radius (r_pore) values and identify parameter sets with high capillary performance. Surface treatments were evaluated to achieve hydrophilic wick structures. Evaluated treatments included chemical oxide growth with H2O2, oxide and sodium titanate growth with NaOH solution, and ultrasonic cleaning with specialty detergents that can remove hydrocarbon contaminants. The most durable hydrophilic surface conditions were obtained with the NaOH treatment. High performing wick deposition parameters were used to produce a full AM NiTi heat pipe, which was treated with NaOH solution to activate the wick. This heat pipe was operated on a test stand in the inverted configuration (upper evaporator and lower condenser), and demonstrated stable nearly isothermal operation for 150 hrs.

Thermal management↗