Search NASA⌕ Search

SEARCH · Search NASA

Results for “constallations”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Precise non-steady-state characterization of solid active materials with no preliminary mechanistic assumptions

This paper presents a straightforward and user-friendly procedure for extracting a reactivity characterization of catalytic reactions on solid materials under non-steady-state conditions, particularly in temporal analysis of products (TAP) experiments. The kinetic parameters derived by this procedure can help with the development of detailed mechanistic understanding. The procedure consists of the following two major steps: 1) Three “Laplace reactivities” are first determined based on the moments of the exit flow pulse response data; 2) Depending on a select kinetic model, kinetic constants of elementary reaction steps can then be expressed as a function of reactivities and determined accordingly. In particular, we distinguish two calculation methods based on the availability and reliability of reactant and product data. The theoretical results are illustrated using a reverse example with given parameters as well as an experimental example of CO oxidation over a supported Au/SiO 2 catalyst. The procedure presented here provides an efficient tool for kinetic characterization of many complex chemical reactions.

03 NATURAL GAS↗
DOE OSTI2019

Optimizing complexity in the kinetic modelling of integrated flue gas purification for pressurized oxy-combustion

A 5-step mechanism and a corresponding kinetic model are presented for integrated flue gas purification, where SOx and NOx are removed during pressurized oxy-coal combustion. Three coupled subsystems (‘blocks”) of gas–liquid transformations are considered: 1) oxidation of NO to NO 2 and dissolution of NO 2 in water; 2) dissolution of SO 2 in the water; and 3) interactions between S- and N- containing substances in the liquid phase. The model has been formulated in terms of only species that can be experimentally measured (model of optimal complexity). Subsystem I is limiting regarding NO removal. Subsystem II is very fast in comparison with the other subsystems and can be treated separately. Analytical expressions for all independent subsystems have been found and compared with computational results for the whole system. The temporal domain of validity of all these subsystems is presented. Finally, the validity of the NO 2 quasi-steady-state assumption is verified, and it is reported that variables such as NO, NO 2 and HNO 3 can be considered decoupled from the whole system since they appear in only Subsystem I, while HSO 3 - and HNO 2 are coupled. The presented kinetic model was verified experimentally by determining the 1:1 ratio of HNO 2 and HNO 3 , in gas–liquid NO-O 2 interaction. Additionally, new experimental facts on kinetic orders and stoichiometry between HNO 2 and HSO 3 - have been used to optimize the model. It is concluded that all NO x - SO x interactions can be essentially grasped by a sequence of only 4 irreversible reactions considering, in addition, the 5th reaction, i.e. the fast ‘SO 2 -water’ equilibrium.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Pulse response analysis using the Y-procedure: A data science approach

We report that pulse response experiments can provide a wealth of data for transient kinetic studies of gas phase heterogeneous reactions, with the ability to paint a detailed picture of intrinsic reaction kinetics pertaining to complex catalytic mechanisms. A novel framework called the Y-Procedure was developed by Yablonsky et al. to extract information from non-steady-state kinetic data (Yablonsky et al., 2007). The Y-Procedure reconstructs the chemical transformation rate and gas composition in the catalytic zone with no a priori assumptions on the kinetic model and is used to relate changes in catalytic reaction rates and kinetic parameters to changes in a catalyst’s surface composition. This paper provides a detailed description of the data science work flow implemented in the Y-procedure through an experimental example of oxygen adsorption on platinum. Lastly, this powerful method, along with a robust list of pre-processing methodology, will enable deeper understanding of kinetic processes and mechanism to be derived from the TAP pulse response technique.

03 NATURAL GAS↗
DOE OSTI2019

Rate/Concentration Kinetic Petals: A Transient Method to Examine the Interplay of Surface Reaction Processes

Transient pulse response experiments are used to construct rate/concentration (RC) kinetic dependencies—RC petals—and provide a new method to distinguish the timing and interplay of adsorption, surface reaction, and product formation on complex (industrial) materials. A petal shape arises as the dynamic “reaction-diffusion” experiment forces the concentration and reaction rate to return to zero. In contrast to the typical steady-state “Langmuir-type” RC dependence, RC petals have two branches, which arise as a result of decoupled gas and surface concentrations in the non-steady-state regime. To demonstrate this approach, the characteristics of petal shapes using ammonia decomposition as a probe reaction are presented. Ammonia, hydrogen, and nitrogen transformation rates are compared on three simple materials: Fe, Co, and a bimetallic CoFe preparation when ammonia is pulsed at 550°C in a low-pressure diffusion reactor. All materials demonstrate a two-branch kinetic RC dependence for ammonia adsorption, and rate constants are quantified in the low-coverage regime. We found that H 2 and N 2 product formation was dependent on the concentration of surface intermediates for all materials with one exception: for Co, an additional fast hydrogen generation process was observed; the rate of which coincided with ammonia adsorption. Nitrogen generation was only significant for CoFe and Co and on the CoFe catalyst, a self-inhibition property was observed. A method for estimating the number of active sites based on the RC petals is presented and was applied to the Fe and CoFe samples. The surface coverage and rate of formation/conversion of surface intermediates are interpreted from the examination of shape characteristics of the RC petals for each material.

36 MATERIALS SCIENCE↗
NASA NTRS2012

The Kepler End-to-End Data Pipeline: From Photons to Far Away Worlds

Launched by NASA on 6 March 2009, the Kepler Mission has been observing more than 100,000 targets in a single patch of sky between the constellations Cygnus and Lyra almost continuously for the last two years looking for planetary systems using the transit method. As of October 2011, the Kepler spacecraft has collected and returned to Earth just over 290 GB of data, identifying 1235 planet candidates with 25 of these candidates confirmed as planets via ground observation. Extracting the telltale signature of a planetary system from stellar photometry where valid signal transients can be small as a 40 ppm is a difficult and exacting task. The end-to end processing of determining planetary candidates from noisy, raw photometric measurements is discussed.

Cygnus constallation↗
NASA NTRS1999

Mars Comm/Nav MicroSat Network

A recent Mars Exploration Program Architecture Definition Study, conducted by NASA with strong international participation, recommands establishment of a low cost in-situ communications and navigation relay satellite network to provide enabling and enhancing support for the international exploration of Mars.

microsatellite↗