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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Tunable Optical True-Time Delay Devices Would Exploit EIT

Tunable optical true-time delay devices that would exploit electromagnetically induced transparency (EIT) have been proposed. Relative to prior true-time delay devices (for example, devices based on ferroelectric and ferromagnetic materials) and electronically controlled phase shifters, the proposed devices would offer much greater bandwidths. In a typical envisioned application, an optical pulse would be modulated with an ultra-wideband radio-frequency (RF) signal that would convey the information that one seeks to communicate, and it would be required to couple differently delayed replicas of the RF signal to the radiating elements of a phased-array antenna. One or more of the proposed devices would be used to impose the delays and/or generate the delayed replicas of the RF-modulated optical pulse. The beam radiated or received by the antenna would be steered by use of a microprocessor-based control system that would adjust operational parameters of the devices to tune the delays to the required values. EIT is a nonlinear quantum optical interference effect that enables the propagation of light through an initially opaque medium. A suitable medium must have, among other properties, three quantum states (see Figure 1): an excited state (state 3), an upper ground state (state 2), and a lower ground state (state 1). These three states must form a closed system that exhibits no decays to other states in the presence of either or both of two laser beams: (1) a probe beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 1; and (2) a coupling beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 2. The probe beam is the one that is pulsed and modulated with an RF signal.

Kulikov, Igor↗
NASA NTRS1976

Six-beam models in radiative transfer theory

A critical analysis is given of the applicability of six-beam models to radiative transfer in particulate materials. The method of introducing transverse scattering in these models is shown to cause fundamental difficulties in the case of physically plausible phase functions; in particular, the effective absorptivity is abnormally large and thus results in incorrect reflectances and transmittances. Six-beam calculations for several media are compared with accurate solutions, with Chu-Churchill two-beam results, and with a simple modification to the Eddington approximation, the last being generally superior over a wide range of conditions.

Meador, W. E.↗
NASA NTRS2000

On the Dynamics of Two Dimensional Array Beam Scanning Via Coupled Oscillators

This presentation will begin with a description of the previous published work contributing to the results reported here. The previously developed one dimensional continuum model will be generalized to two dimensions and a Green's function for the resulting differential equation will be obtained as an eigenfunction expansion. This will be used to obtain dynamic solutions relevant to the steering of the radiated beam. Finally, some remarks concerning limitations on the interoscillator phase difference will be provided.

Pogorzelski, R. J.↗
NASA NTRS2000

Beam scanning reflectarray antenna with circular polarization

A novel means of scanning a circularly polarized reflectarray antenna. The reflectarray is an array of metallic elements arranged on a surface designed to compensate for the various path lengths of the optical rays from an illuminating feed to the reflecting surface and then to the antenna aperture. With appropriate design, the phase in the aperture can be made to vary linearly in any desired direction and also to produce a radiated beam normal to the constant phase surface. In the case of circular polarization, this path length compensation can be accomplished by rotation of the individual elements.

Huang, John↗
NASA NTRS2012

High Energy/LET Radiation EEE Parts Certification Handbook

Certifying electronic components is a very involved process. It includes pre-coordination with the radiation test facility for time, schedule and cost, as well as intimate work with designers to develop test procedures and hardware. It also involves work with radiation engineers to understand the effects of the radiation field on the test article/setup as well as the analysis and production of a test report. The technical content of traditional ionizing radiation testing protocol is in wide use and generally follows established standards (ref. Appendix C). This document is not intended to cover all these areas but to cover the methodology of using Variable Depth Bragg Peak (VDBP) to accomplish the goal of characterizing an electronic component. The Variable Depth Bragg Peak (VDBP) test method is primarily used for deep space applications of electronics. However, it can be used on any part for any radiation environment, especially those parts where the sensitive volume cannot be reached by the radiation beam. An example of this problem would be issues that arise in de-lidding of parts or in parts with flip-chip designs, etc. The VDBP method is ideally suited to test modern avionics designs which increasingly incorporate commercial off-the-shelf (COTS) parts and units. Johnson Space Center (JSC) developed software provides assistance to users in developing the radiation characterization data from the raw test data.

Reddell, Brandon↗
NASA NTRS2003

STS-112 Mission Highlights Resource Tape Part 2 of 3

An overview of the STS-112 Mission is presented. The fourth flight day begins with a view inside of the Destiny Laboratory of the International Space Station where Expedition Five Commander Valery Korzun is shown. The robotics workstation where Mission Specialist Sandra Mangus and Flight Engineer Peggy Whitson operate Canadarm 2 to lift the S(1) Truss segment out of the payload bay of the Space Shuttle Atlantis and maneuver it for installation onto the S(1) Truss is presented. Mission Specialist Piers Sellers is shown preparing for his six and one half hour spacewalk by performing breathing exercises. Animation of the installation of the S(1) Truss, and also the unbirthing of the S(1) truss is also presented. Mission Specialists David Wolf and Piers Sellers are shown getting suited for their spacewalks. During the spacewalk, David Wolf is removing the antenna assembly from its launched position and Piers Sellers is releasing launch restraints from the Radiator Beam Assembly. A beautiful view of the coast of Texas is captured during this spacewalk. Flight day five shows pilot Pam Melroy and Mission Specialist Dave Wolf working inside of the International Space Station's Quest Airlock. Flight day six is shown with Dave Wolf and Piers Sellers exiting their spacesuits inside of the Quest Airlock Module after a successful spacewalk. This presentation ends with views of the International Space Station's installed S(1) Truss, rotation of the radiator assembly and the radiator's coolant tubing.

Source record↗
NASA NTRS2018

Robotic External Leak Locator (RELL) Leak Plume Field Detection on the International Space Station (ISS)

The Robotic External Leak Locator (RELL) was deployed to the International Space Station (ISS) with the objective of demonstrating the ability to detect and locate small leaks. On-orbit operations began in late November 2016 and following scanning activities to characterize the natural and induced environment of the ISS, RELL focused on the United States External Active Thermal Control System (EATCS). RELL successfully detected ammonia related to a known small ammonia leak in the port-side EATCS, with the highest pressure values around the inboard Radiator Beam Valve Module 1 (RBVM 1). An additional day of scanning was subsequently performed in December 2017 to focus on RBVM 1. RELL was approved for additional external operations in February 2017 with the goal of fine tuning the location of the leak. Using grid scanning patterns, RELL detected ammonia around RBVM 1 and located the approximate source of the leak. The potential leak site was inspected by a crew member during an Extravehicular Activity (EVA) in March 2017, and the suspected radiator-side lines were isolated from the port-side EATCS coolant loop in April 2017. Subsequent monitoring of the system pressures showed that the leak has stopped, indicating RELL accurately located the source of the EATCS leak. These activities verify that RELL enhances the ISS Program's ability to not only locate small leaks, but isolate the source with minimal impact to the entire ISS system.

External Active Thermal Control System↗
NASA NTRS2006

Coupled Oscillator Based Agile Beam Transmitters and Receivers: A Review of Work at JPL

This is a review of the work done at Caltech's Jet Propulsion Laboratory during the past decade on development of the coupled oscillator technology in phased array applications to spacecraft telecommunications. First, some historical background is provided to set the work in context. However, this is by no means intended to be a comprehensive review of all work in this area. Rather, the focus is on the JPL contribution with some mention of other work which provided either insight or motivation. In the mid 1990's, R. A. York, and collaborators proposed that an array of mutually injection locked electronic oscillators could provide appropriately phased signals to the radiating elements of an array antenna such that the radiated beam could be steered merely by tuning the end or perimeter oscillators of the array. York, et al. also proposed a receiving system based on such oscillator arrays in which the oscillators provide properly phased local oscillator signals to be mixed with the signals received by the array elements to remove the phase due to angle of arrival of the incident wave. These concepts were viewed as a promising simplification of the beam steering control system that could result in significant cost, mass, and prime power reduction and were therefore attractive for possible space application.

mutual injection locking↗
NASA NTRS1967

Microwave Driven Magnetic Plasma Accelerator Studies (CYCLOPS)

A microwave-driven cyclotron resonance plasma acceleration device was investigated using argon, krypton, xenon, and mercury as propellants. Limited ranges of propellant flow rate, input power, and magnetic field strength were used. Over-all efficiencies (including the 65% efficiency of the input polarizer) less than 10% were obtained for specific impulse values between 500 and 1500 sec. Power transfer efficiencies, however, approached 100% of the input power available in the right-hand component of the incident circularly polarized radiation. Beam diagnostics using Langmuir probes, cold gas mapping, r-f mapping and ion energy analyses were performed in conjunction with an engine operating in a pulsed mode. Measurements of transverse electron energies at the position of cyclotron resonant absorption yielded energy values more than an order of magnitude lower than anticipated. The measured electron energies were, however, consistent with the low values of average ion energy measured by retarding potential techniques. The low values of average ion energy were also consistent with the measured thrust values. It is hypothesized that ionization and radiation limit the electron kinetic energy to low-values thus limiting the energy which is finally transferred to the ion. Thermalization by electron-electron collision was also identified as an additional loss mechanism. The use of light alkali metals, which have relatively few low lying energy levels to excite, with the input power to mass ratio selected so as to limit the electron energies to less than the second ionization potential, is suggested. It is concluded, however, that the over-all efficiency for such propellants would be less than 40 per cent.

CYCLOPS PLASMA ACCELERATOR↗
NASA NTRS2005

Patch Antenna Fed via Unequal-Crossed-Arm Aperture

A proposed rectangular-patch antenna for transmitting or receiving microwave circularly polarized (CP) radiation would be fed via a cross-shaped aperture that would have unequal arms and would, in turn, be fed at a single point via a microstrip transmission line. As a consequence of the unequal-arm aperture design, the antenna could be made smaller in one dimension, relative to a typical prior CP antenna that comprises a nearly square patch fed via an equal-crossed-arm aperture. Hence, in designing a phased array of such antennas, the antennas could be packed together more closely along one dimension, making it possible to scan the beam radiated by the antenna over a wider angular range in a plane that includes that dimension. Alternatively or in addition, one could lay out transmission lines in the extra spaces created by the shortening in one dimension

Epp, Larry↗
NASA NTRS2004

Dual-Frequency Airborne Scanning Rain Radar Antenna System

A compact, dual-frequency, dual-polarization, wide-angle-scanning antenna system has been developed as part of an airborne instrument for measuring rainfall. This system is an upgraded version of a prior single-frequency airborne rain radar antenna system and was designed to satisfy stringent requirements. One particularly stringent combination of requirements is to generate two dual-polarization (horizontal and vertical polarizations) beams at both frequencies (13.405 and 35.605 GHz) in such a way that the beams radiated from the antenna point in the same direction, have 3-dB angular widths that match within 25 percent, and have low sidelobe levels over a wide scan angle at each polarization-and-frequency combination. In addition, the system is required to exhibit low voltage standing-wave ratios at both frequencies. The system (see figure) includes a flat elliptical scanning reflector and a stationary offset paraboloidal reflector illuminated by a common-aperture feed system that comprises a corrugated horn with four input ports one port for each of the four frequency-and-polarization combinations. The feed horn is designed to simultaneously (1) under-illuminate the reflectors 35.605 GHz and (2) illuminate the reflectors with a 15-dB edge taper at 13.405 GHz. The scanning mirror is rotated in azimuth to scan the antenna beam over an angular range of 20 in the cross-track direction for wide swath coverage, and in elevation to compensate for the motion of the aircraft. The design of common-aperture feed horn makes it possible to obtain the required absolute gain and low side-lobe levels in wide-angle beam scanning. The combination of the common-aperture feed horn with the small (0.3) focal-length-to-diameter ratio of the paraboloidal reflector makes it possible for the overall system to be compact enough that it can be mounted on a DC-8 airplane.

Hussein, Ziad A.↗
NASA NTRS1976

Absorption cell - A modified multiple-traversal device

A modified White-type multiple-transversal absorption cell used with a 5-m Littrow spectrometer is described. It can be introduced at a focus of the radiation beam without altering the beam configuration. The conventional White cell consists of three mirrors of equal focal length, with a distance of two focal lengths separating one of the mirrors from a mirror pair. The modification in the design consists of the addition of two mirrors at a slant placed behind the solitary mirror of the conventional configuration. The mirror arrangement reproduces the configuration of the exit beam for any number of transversals of the cell.

Jennings, D. E.↗
NASA NTRS1977

Design curves for double-heterojunction laser diodes

This paper reviews theoretical double-heterojunction laser design curves relating the structure with the transverse mode order able to propagate, the degree of radiation confinement to the active region, the maximum field intensity within the device, and the radiated beam shape. The curves presented are general and applicable to any double-heterojunction structure where the spacing of the heterojunctions and the refractive index in the relevant regions are known.

Butler, J. K.↗
NASA NTRS1981

Saturnian kilometric radiation: Source locations

The surce locations of both polariation components of the saturn kilometer wavelength radiation were deduced using Voyager 1 and Voyager 2 planetary radio astronomy data and assumptions about radiation beam geometry. Radio source footprints were compared with the surface locations of saturns ultraviolet aurorae, its polar cap boundary, and its polar cusp.

Kaiser, M. L.↗