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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.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

X-ray Evaluation of the Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS) Nickel-Replicated Mirrors

X-ray observations of astronomical objects provides diagnostics not available in any other wavelength regime, however the capability of making these observation at a high spatial resolution has proven challenging. Recently, NASA Marshall Space Flight Center (MSFC) has made good progress in employing computer numerical control (CNC) polishing techniques on electroless nickel mandrels as part of our replicated grazing incidence optics program. CNC polishing has afforded the ability to deterministically refine mandrel figure, thereby improving mirror performance. The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a MSFC-led sounding rocket instrument that is designed to make the first ever soft x-ray spectral observations of the Sun spatially resolved along a narrow slit. MaGIXS incorporates some of the first mirrors produced at MSFC using this polishing technique. Here we present the predicted mirror performance obtained from metrology, after completion of CNC polishing, as well as the results of X-ray tests performed on the MaGIXS telescope mirror before and after mounting.

MaGIXS X-ray Tests↗
NASA NTRSDate not supplied

Lessons learned from replicating services for flood prediction and monitoring in Asia to the assessment of hurricane impacts in Central America

In October and November 2020, two dangerous back-to-back hurricanes, Eta and Iota, made landfall in Central America. The SERVIR program - a joint effort of NASA and the U.S. Agency for International Development, and whose motto is “connecting space to village” was able to leverage two tools originally developed for use in other regions for predicting and assessing the flood impacts of the hurricanes. The GEOGLoWS Streamflow Prediction tool - originally implemented in the Hindu Kush Himalayan region - was used for predicting potential flooding ahead of landfall by Eta and Iota. In conjunction, the Hydrologic Remote Sensing Analysis for Floods (HYDRAFloods) framework - originally developed along with SERVIR-Mekong - was used for post-event flood mapping, leveraging its ability to map floods in cloud-covered areas using synthetic aperture radar (SAR) imagery from the Copernicus program. Both tools were used in support of disaster coordination efforts being led by the Central American Regional Disaster Prevention Center (CEPREDENAC), in conjunction with its sister agency, the Regional Water Resources Committee (CRRH). The support provided to regional entities - and to their stakeholder national governments - served as an example of rapid generation of Earth observation products for disaster response. Feedback on those products was also provided, especially in terms of the implications of (i) calibration of predicted river volumes, and (ii) the latency of the input Earth observation imagery and attempts to map the floods’ maximum extents. An upcoming NASA DEVELOP project will also seek to strengthen the capability of CEPREDENAC and CRRH to apply HYDRAFloods for future extreme events. The application of the tools also provides a useful case study on capacity building, in terms of how Earth observation data and models can be replicated across regions.

Capacity building↗
NASA NTRS1984

Control of Self-Replicating Systems

Three concepts proposed for system management and control. Concepts are: internal system for autonomous management and control, separate system for environment monitoring, and optical intelligent system required in especially chaotic environments. Intelligent system responds by making decisions and solving problems in novel situations preprogramed.

Von Tiesenhausen, G.↗
NASA NTRS1983

Electron beam injection experiments - Replication of flight observations in a laboratory beam plasma discharge

Recent electron beam injection experiments in the lower ionosphere have produced two perplexing results: (1) At altitudes from 140 km to 220 km, the beam associated 391.4 nm intensity is relatively independent of altitude despite the decreasing N2 abundance. (2) The radial extent of the perturbed region populated by beam associated energetic electrons significantly exceeds the nominal gyrodiameter for 90 deg injection. A series of laboratory measurements is described in which both of these flight results appear to have been closely reproduced. The laboratory results are reasonably consistent with the transition from a collision dominated to collisionless beam-plasma discharge configuration.

Bernstein, W.↗
NASA NTRS1984

Electroform replication used for multiple X-ray mirror production

The electroforming technique for producing X-ray mirrors is described, and results of X-ray tests performed on copies made from a simple conical mandrel are reported. The design of the mandrel is depicted and the total reflectivity as well as the full-wave half modulation resolution are shown as a function of energy. The reported work has improved on previous studies by providing smaller grazing angles, making measurements at higher energies, producing about four times as many replicas from one mandrel, and obtaining better angular resolution.

Kowalski, M. P.↗
NASA NTRS1983

New techniques for fusion bonding and replication for large glass reflectors

Lightweight, space-deployable glass honeycomb telescope primary mirror structures are produced by a novel method which involves the heating to softening temperature of many borosilicate or silica glass tube sections that are packed to form a honeycomb matrix and filled with a high expansion coefficient refractory sand. The close packed tubes yield a hexagonal-cell honeycomb. Attention is given to the results of an experiment in which a highly refractory master was used to shape a honeycomb of less refractory glass, employing a 1-micron thick, vacuum-deposited gold coating as a parting layer between the two.

Angel, J. R. P.↗
NASA NTRS1985

Performance analysis of the ALOHA protocol with replication in a fading channel for the Mobile Satellite Experiment

The analysis of the ALOHA random access protocol for communications channels with fading is presented. The protocol is modified to send multiple contiguous copies of a message at each transmission attempt. Both pure and slotted ALOHA channels are considered. A general two state model is used for the channel error process to account for the channel fading memory. It is shown that greater throughput and smaller delay may be achieved using repetitions. The model is applied to the analysis of the delay-throughput performance in a fading mobile communications environment. Numerical results are given for NASA's Mobile Satellite Experiment.

Clare, L. P.↗
NASA NTRS1986

Wind tunnel tests of rotor blade sections with replications of ice formations accreted in hover

Full scale reproductions of ice accretions molded during the documentation of a hover test program were fabricated by means of epoxy castings and used for a wind tunnel test program. Surface static pressure distributions were recorded and used to evaluate lift and pitching moment increments while drag was determined by wake surveys. Through the range of the tests, corresponding to those conditions encountered in hover and in flat pitch, integration of the pressure distributions showed negligible changes in lift and in pitching moment, but the drag was significantly increased.

Lee, J. D.↗