Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “communication volume”

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.

At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Low Differential Pressure Generator

A method and apparatus for evaluating low differential pressure transducers includes a pressure generator in the form of a piston-cylinder assembly having a piston that may be manually positioned precisely within the cylinder to change the volume and thus the pressure at respective sides of the piston. At one side of the piston the cylinder communicates with a first chamber and at the other side of the piston the cylinder communicates with a second chamber, the first and second chambers being formed within a common tank by a partition wall. The chambers each communicate with the transducer to be evaluated and a standard pre-calibrated transducer the transducers being connected fluidly in parallel so that a pressure differential between air in the two chambers resulting from movement of the piston within the cylinder is communicated to both the transducer to be evaluated and the standard transducer, and the outputs of the transducers is observed and recorded.

Stout, Stephen J.↗
NASA NTRS2006

Li-ion rechargeable batteries on Mars Exploration Rovers

Lithium-ion batteries have contributed significantly to the success of NASA's Mars Rovers, Spirit and Opportunity that have been exploring the surface of Mars for the last two years and performing astounding geological studies to answer the ever-puzzling questions of life beyond Earth and the origin of our planets. Combined with the triple-junction solar cells, the lithium-ion batteries have been powering the robotic rovers, and assist in keeping the rover electronics warm, and in supporting nighttime experimentation and communications. The use of Li-ion batteries has resulted in significant benefits in several categories, such as mass, volume, energy efficiency, self discharge, and above all low temperature performance. Designed initially for the primary mission needs of 300 cycles over 90 days of surface operation, the batteries have been performing admirably, over the last two years. After about 670 days of exploration and at least as many cycles, there is little change in the end-of discharge (EOD) voltages or capacities of these batteries, as estimated from the in-flight data and corroborated by ground testing. Aided by such impressive durability from the Li-ion batteries, both from cycling and calendar life stand point, these rovers are poised to extend their exploration well beyond two years. In this paper, we will describe the performance characteristics of these batteries during launch, cruise phase and on the surface of Mars thus far.

litium ion batteries↗
NASA NTRS2010

Photon Counting Using Edge-Detection Algorithm

New applications such as high-datarate, photon-starved, free-space optical communications require photon counting at flux rates into gigaphoton-per-second regimes coupled with subnanosecond timing accuracy. Current single-photon detectors that are capable of handling such operating conditions are designed in an array format and produce output pulses that span multiple sample times. In order to discern one pulse from another and not to overcount the number of incoming photons, a detection algorithm must be applied to the sampled detector output pulses. As flux rates increase, the ability to implement such a detection algorithm becomes difficult within a digital processor that may reside within a field-programmable gate array (FPGA). Systems have been developed and implemented to both characterize gigahertz bandwidth single-photon detectors, as well as process photon count signals at rates into gigaphotons per second in order to implement communications links at SCPPM (serial concatenated pulse position modulation) encoded data rates exceeding 100 megabits per second with efficiencies greater than two bits per detected photon. A hardware edge-detection algorithm and corresponding signal combining and deserialization hardware were developed to meet these requirements at sample rates up to 10 GHz. The photon discriminator deserializer hardware board accepts four inputs, which allows for the ability to take inputs from a quadphoton counting detector, to support requirements for optical tracking with a reduced number of hardware components. The four inputs are hardware leading-edge detected independently. After leading-edge detection, the resultant samples are ORed together prior to deserialization. The deserialization is performed to reduce the rate at which data is passed to a digital signal processor, perhaps residing within an FPGA. The hardware implements four separate analog inputs that are connected through RF connectors. Each analog input is fed to a high-speed 1-bit comparator, which digitizes the input referenced to an adjustable threshold value. This results in four independent serial sample streams of binary 1s and 0s, which are ORed together at rates up to 10 GHz. This single serial stream is then deserialized by a factor of 16 to create 16 signal lines at a rate of 622.5 MHz or lower for input to a high-speed digital processor assembly. The new design and corresponding hardware can be employed with a quad-photon counting detector capable of handling photon rates on the order of multi-gigaphotons per second, whereas prior art was only capable of handling a single input at 1/4 the flux rate. Additionally, the hardware edge-detection algorithm has provided the ability to process 3-10 higher photon flux rates than previously possible by removing the limitation that photoncounting detector output pulses on multiple channels being ORed not overlap. Now, only the leading edges of the pulses are required to not overlap. This new photon counting digitizer hardware architecture supports a universal front end for an optical communications receiver operating at data rates from kilobits to over one gigabit per second to meet increased mission data volume requirements.

Gin, Jonathan W.↗
NASA NTRSDate not supplied

A Flat-Panel 8x8 Sequentially Rotated Wideband Microstrip Patch Phased Array Antenna for K/Ka-band 6U CubeSat Communications Applications

Flat-panel electronically-scanned phased arrays have recently become a mainstream technology in the areas of radar and satellite applications, particularly due to their low profile and not having to steer the beams mechanically, both of which helps in realizing a lightweight phased array solution that also occupies a smaller volume. Typically for satellite applications, circularly polarized element radiators are often employed in order to deal with the signal fading problem. In this project, the main objective was to design a flat-panel phased array solution for 6U CubeSat communication applications. As for the required specifications, the array should have two operating bands: 22.55–23.55 GHz and 25.5–27.5 GHz, which span part of the K and Ka bands. For both these bands, the panel should be able to radiate dual circular polarization, in both transmit and receive modes, and with a stable gain performance. Since the individual bands are very closely spaced, it was realized that a single wideband design would be a better solution than a closely spaced dual-band design. Thus, a stacked microstrip patch configuration was selected for the element radiator design, which is known to be wideband. Now, it is rather difficult to realize both wide impedance and axial ratio bandwidths simultaneously, and at high frequencies, without complicating the element stacked patch design.. As a result, a sequential rotation technique wasemployed to significantly improves the axial ratio bandwidth and circular polarization purity of an array, all the while improving the pattern symmetry (P. S. Hall, “Application of Sequential Feeding to Wide Bandwidth, Circularly Polarised Microstrip Patch Arrays,” IEE Proc. H (Microw., Antennas Propag.), vol. 136, no. 5, pp. 390–398, Oct. 1989). The designed element radiator is a circularly-polarized probe-fed stacked patch antenna, which has a 10-dB matching bandwidth of 22.3– 30 GHz, with only a 5.14% axial ratio bandwidth around the center frequency of the required band, i.e., ~25 GHz. However, the resulting array demonstrates a very low axial ratio (≪ 3 dB) over the entire bandwidth, due to the application of the sequential rotation technique. The 8×8 array was able to scan up to ±51° and ±40° at frequencies 23.05 GHz and 26.5 GHz (center frequencies of the lower and upper bands), respectively, while maintaining a ≤ 3 dB axial ratio and a ≤ 3 dB gain drop from the corresponding peak broadside value at both the principle and the diagonal radiation planes. The designed layout for the 8×8 phased array prototype is shown in Fig. 1, which is currently undergoing fabrication and RF assembly. The antenna will be tested in the far-field anechoic chambers of the Antenna and Microwave Laboratory (AML) at San Diego State University and at NASA Glenn Research Center (GRC).

5G↗
NASA NTRS2021

Brief Communication: An Empirical Relation Between Center Frequency and Measured Thickness for Radar Sounding of Temperate Glaciers

Radar sounding of the thickness of temperate glaciers is challenged by substantial volume scattering, surface scattering and high attenuation rates. Lower-frequency radar sounders are often deployed to mitigate these effects, but the lack of a global synthesis of their success limits progress in system and survey design. Here we extend a recent global compilation of glacier thickness measurements (GlaThiDa) with the center frequency for radar-sounding surveys. From a maximum reported thickness of ∼ 1500 m near 1 MHz, the maximum thickness sounded decreases by ∼ 500 m per frequency decade. Between 25–100 MHz, newer airborne radar sounders generally outperform older, ground-based ones. Based on globally modeled glacier thicknesses, we conclude that a multi-element, ≤30 MHz airborne radar sounder could survey most temperate glaciers more efficiently.

Joseph A MacGregor↗
NASA NTRS1988

Space station tracking requirements feasibility study, volume 1

The objective of this feasibility study is to determine analytically the accuracies of various sensors being considered as candidates for Space Station use. Specifically, the studies were performed whether or not the candidate sensors are capable of providing the required accuracy, or if alternate sensor approaches be investigated. Other topics related to operation in the Space Station environment were considered as directed by NASA-JCS. The following topics are addressed: (1) Space Station GPS; (2) Space Station Radar; (3) Docking Sensors; (4) Space Station Link Analysis; (5) Antenna Switching, Power Control, and AGC Functions for Multiple Access; (6) Multichannel Modems; (7) FTS/EVA Emergency Shutdown; (8) Space Station Information Systems Coding; (9) Wanderer Study; and (10) Optical Communications System Analysis. Brief overviews of the abovementioned topics are given. Wherever applicable, the appropriate appendices provide detailed technical analysis. The report is presented in two volumes. This is Volume 1, containing the main body and Appendices A through J.

Udalov, Sergei↗
NASA NTRS2007

R.F Microphotonics for NASA Space Communications Applications

An RF microphotonic receiver has-been developed at Ka-band. The receiver consists of a lithium niobate micro-disk that enables RF-optical coupling to occur. The modulated optical signal (- 200 THz) is detected by the high-speed photonic signal processing electronics. When compared with an electronic approach, the microphotonic receiver technology offers 10 times smaller volume, smaller weight, and smaller power consumption; greater sensitivity; and optical isolation for use in extreme environments. The status of the technology development will be summarized, and the potential application of the receiver to NASA space communications systems will be described.

Pouch, John↗
NASA NTRS1988

Space station tracking requirements feasibility study, volume 2

The objective of this feasibility study is to determine analytically the accuracies of various sensors being considered as candidates for Space Station use. Specifically, the studies were performed whether or not the candidate sensors are capable of providing the required accuracy, or if alternate sensor approaches should be investigated. Other topics related to operation in the Space Station environment were considered as directed by NASA-JSC. The following topics are addressed: (1) Space Station GPS; (2) Space Station Radar; (3) Docking Sensors; (4) Space Station Link Analysis; (5) Antenna Switching, Power Control, and AGC Functions for Multiple Access; (6) Multichannel Modems; (7) FTS/EVA Emergency Shutdown; (8) Space Station Information Systems Coding; (9) Wanderer Study; and (10) Optical Communications System Analysis. Brief overviews of the abovementioned topics are given. Wherever applicable, the appropriate appendices provide detailed technical analysis. The report is presented in two volumes. This is Volume 2, containing Appendices K through U.

Udalov, Sergei↗
NASA NTRS1986

Laser diode combining for free space optical communication

The maximization of photon delivery to a distant collector in free space optical communications systems calls for a laser diode-combining technique employing wavelength and/or polarization as the bases of its operation. Design considerations for such a combiner encompass high throughput efficiency, diffraction-limited angular divergence, and reasonable volume constraints. Combiners are presently found to require a generalized Strehl ratio concept which includes relative source misalignment; diffraction grating combiners may have a limited number of laser sources which can meet spectral requirements. Methods for the incorporation of a combiner into a communication system are compared. Power combining is concluded to be the best tradeoff of performance and complexity for all systems, except those that are severely limited by either background radiation or component bandwidth.

Mecherle, G. Stephen↗
NASA NTRS1975

Electronically steerable millimeter wave antenna techniques for space shuttle applications

A large multi-function antenna aperture and related components are described which will perform electronic steering of one or more beams for two of the three applications envisioned: (1) communications, (2) radar, and (3) radiometry. The array consists of a 6-meter folded antenna that fits into two pallets. The communications frequencies are 20 and 30 GHz, while the radar is to operate at 13.9 GHz. Weight, prime power, and volumes are given parametrically; antenna designs, electronics configurations, and mechanical design were studied.

Kummer, W. H.↗
NASA NTRS1995

An approach to efficient mobility management in intelligent networks

Providing personal communication systems supporting full mobility require intelligent networks for tracking mobile users and facilitating outgoing and incoming calls over different physical and network environments. In realizing the intelligent network functionalities, databases play a major role. Currently proposed network architectures envision using the SS7-based signaling network for linking these DB's and also for interconnecting DB's with switches. If the network has to support ubiquitous, seamless mobile services, then it has to support additionally mobile application parts, viz., mobile origination calls, mobile destination calls, mobile location updates and inter-switch handovers. These functions will generate significant amount of data and require them to be transferred between databases (HLR, VLR) and switches (MSC's) very efficiently. In the future, the users (fixed or mobile) may use and communicate with sophisticated CPE's (e.g. multimedia, multipoint and multisession calls) which may require complex signaling functions. This will generate volumness service handling data and require efficient transfer of these message between databases and switches. Consequently, the network providers would be able to add new services and capabilities to their networks incrementally, quickly and cost-effectively.

Murthy, K. M. S.↗
NASA NTRS1998

Exploring the Unknown: Selected Documents in the History of the US Civilian Space Program: Using Space - Volume 3

One of the most important developments of the twentieth century has been the movement of humanity into space with machines and people. The underpinnings of that movement -why it took the shape it did; which individuals and organizations were involved; what factors drove a particular choice of scientific objectives and technologies to be used; and the political, economic, managerial, and international contexts in which the events of the space age unfolded- are all important ingredients of this epoch transition from an earthbound to spacefaring people. This desire to understand the development of spaceflight in the United States sparked this documentary history series. 'Exploring the Unknown' is a multi-volume series containing a selection of key documents in history of the U.S. civil space program. This current volume, Volume III, focusing on the use of space for practical applications, prints 112 key documents on the history of satellite communications, remote sensing of earth, and space as an investment in economic growth, edited for ease of use. Each is introduced by a headnote providing context, bibliographical information, and background information necessary to understanding the document.

Logsdon, John M.↗
NASA NTRS2005

The Origin and Early Evolution of Membrane Proteins

Membrane proteins mediate functions that are essential to all cells. These functions include transport of ions, nutrients and waste products across cell walls, capture of energy and its transduction into the form usable in chemical reactions, transmission of environmental signals to the interior of the cell, cellular growth and cell volume regulation. In the absence of membrane proteins, ancestors of cell (protocells), would have had only very limited capabilities to communicate with their environment. Thus, it is not surprising that membrane proteins are quite common even in simplest prokaryotic cells. Considering that contemporary membrane channels are large and complex, both structurally and functionally, a question arises how their presumably much simpler ancestors could have emerged, perform functions and diversify in early protobiological evolution. Remarkably, despite their overall complexity, structural motifs in membrane proteins are quite simple, with a-helices being most common. This suggests that these proteins might have evolved from simple building blocks. To explain how these blocks could have organized into functional structures, we performed large-scale, accurate computer simulations of folding peptides at a water-membrane interface, their insertion into the membrane, self-assembly into higher-order structures and function. The results of these simulations, combined with analysis of structural and functional experimental data led to the first integrated view of the origin and early evolution of membrane proteins.

Pohorille, Andrew↗
NASA NTRS2007

NASA Bluetooth Wireless Communications

NASA has been interested in wireless communications for many years, especially when the crew size of the International Space Station (ISS) was reduced to two members. NASA began a study to find ways to improve crew efficiency to make sure the ISS could be maintained with limited crew capacity and still be a valuable research testbed in Low-Earth Orbit (LEO). Currently the ISS audio system requires astronauts to be tethered to the audio system, specifically a device called the Audio Terminal Unit (ATU). Wireless communications would remove the tether and allow astronauts to freely float from experiment to experiment without having to worry about moving and reconnecting the associated cabling or finding the space equivalent of an extension cord. A wireless communication system would also improve safety and reduce system susceptibility to Electromagnetic Interference (EMI). Safety would be improved because a crewmember could quickly escape a fire while maintaining communications with the ground and other crewmembers at any location. In addition, it would allow the crew to overcome the volume limitations of the ISS ATU. This is especially important to the Portable Breathing Apparatus (PBA). The next generation of space vehicles and habitats also demand wireless attention. Orion will carry up to six crewmembers in a relatively small cabin. Yet, wireless could become a driving factor to reduce launch weight and increase habitable volume. Six crewmembers, each tethered to a panel, could result in a wiring mess even in nominal operations. In addition to Orion, research is being conducted to determine if Bluetooth is appropriate for Lunar Habitat applications.

Miller, Robert D.↗
NASA NTRS2008

A New Concurrent Multiscale Methodology for Coupling Molecular Dynamics and Finite Element Analyses

The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.

Yamakov, Vesselin↗
NASA NTRS2008

An Embedded Statistical Method for Coupling Molecular Dynamics and Finite Element Analyses

The coupling of molecular dynamics (MD) simulations with finite element methods (FEM) yields computationally efficient models that link fundamental material processes at the atomistic level with continuum field responses at higher length scales. The theoretical challenge involves developing a seamless connection along an interface between two inherently different simulation frameworks. Various specialized methods have been developed to solve particular classes of problems. Many of these methods link the kinematics of individual MD atoms with FEM nodes at their common interface, necessarily requiring that the finite element mesh be refined to atomic resolution. Some of these coupling approaches also require simulations to be carried out at 0 K and restrict modeling to two-dimensional material domains due to difficulties in simulating full three-dimensional material processes. In the present work, a new approach to MD-FEM coupling is developed based on a restatement of the standard boundary value problem used to define a coupled domain. The method replaces a direct linkage of individual MD atoms and finite element (FE) nodes with a statistical averaging of atomistic displacements in local atomic volumes associated with each FE node in an interface region. The FEM and MD computational systems are effectively independent and communicate only through an iterative update of their boundary conditions. With the use of statistical averages of the atomistic quantities to couple the two computational schemes, the developed approach is referred to as an embedded statistical coupling method (ESCM). ESCM provides an enhanced coupling methodology that is inherently applicable to three-dimensional domains, avoids discretization of the continuum model to atomic scale resolution, and permits finite temperature states to be applied.

Saether, E.↗
NASA NTRS2019

Innovative Approaches to Using the International Space Station as a Mars Transit Analog

Human research on the International Space Station (ISS) crew has made significant advances in understanding of the effects of physiology on human health in space missions. However, ISS has not been as suitable for research on other hazards of human spaceflight such as isolation and communications delay. NASA recently completed a special assessment of whether modifications could be made to operations or facilities so that ISS could be used more effectively as an analog to simulate long-duration crew missions beyond low earth orbit. A cross-disciplinary team met to identify concept of operations, trade spaces, challenges, and opportunities to making ISS more operationally relevant as a Mars transit mission analog, and the results and implementation plans are summarized in this manuscript. In addition to the use case of 12-month missions (already in planning by the NASA ISS Program to bound expected Mars transit durations), three new use cases where ISS could provide valuable high-fidelity experience were identified. (1) Testing of operations procedures and medical care could be enhanced by demonstrating crew handling a simulated medical event in microgravity, autonomously, and with significant communications delay. (2) Isolation and confinement effects of deep space transit could be studied on ISS to validate current habitable volume requirements for Mars transit as well as provide context for evaluating the results of the extensive ground-based simulations in HERA and NEK. A trade study of possible operational and hardware changes that would make ISS applicable to these use cases was completed. (3) Surface operations after the physiological deconditioning of a long transit could be conducted to validate crew ability to perform critical ground tasks after 6-month Mars transit and aid in conceptual design of Mars surface element architectures. Each of the case studies includes a trade space between operational impacts on nominal ISS activities and degree of fidelity. A phased approach to implementation means that several "quick start" activities can be done in 2019-2020 at the same time as planning continues for more complex exploration analog options beginning as early as 2022. The team determined that many of these quick-start tasks could be done with available assets, entirely independent of other exploration system development timelines (such as Orion, Space Launch System). The consideration of the full suite of human spaceflight capabilities in the lunar vicinity can also be included as each step in human exploration serves as a simulation opportunity for some aspect of subsequent missions. Further discussions of options with the international community are critical for considering the benefits as well as impacts of simulation activities on ISS, as well as to better formulate future mission architectures.

Robinson, Julie A.↗