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Distributions of current, potential, electron density and pressure and ion velocity vector orientation in MPD arc, verifying electromagnetic effects presence
This paper examines the vehicle antenna requirements for mobile satellite systems. The antenna parameters are discussed in the light of the requirements and the limitations in performance imposed by the physical constraints of antenna and by vehicle geometries. Measurements of diffraction and antenna noise temperature in an operational environment are examined, as well as their effects on system margins. Mechanical versus electronic designs are compared with regards to performance, cost, reliability, and design complexity. Comparisons between open-loop and close-loop tracking systems are made and the effects of bandwidth, sidelobe levels, operational constraints, vehicle angular velocity, and acceleration are discussed. Some consideration is given to the use of hybrid systems employing both open and closed-loop tracking. Changes to antenna/terminal specifications are recommended which will provide greater design flexibility and increase the likelihood of meeting the performance and operational requirements.
The need to detect unauthorized usage of intentionally transmitting portable electronic devices (PEDs) onboard commercial aircraft is growing, while still allowing passengers to use selected unintentionally transmitting devices, such as laptop computers and CD players during non-critical stages of flight. The following paper presents an installed system for detecting PEDs over multiple frequency bands. Additionally, the advantages of a fixed verses mobile system are discussed. While data is presented to cover the frequency range of 20 MHz to 6.5 GHz, special attention was given to the Cellular/PCS bands as well as Bluetooth and the FRS radio bands. Measurement data from both the semi-anechoic and reverberation chambers are then analyzed and correlated with data collected onboard a commercial aircraft to determine the dominant mode of coupling inside the passenger cabin of the aircraft versus distance from the source. As a final check of system feasibility, several PEDs transmission signatures were recorded and compared with the expected levels.
Features, capabilities, and projected performances and missions of the Manned Maneuvering Unit (MMU) are described. A zero gravity, autonomous, six degree of freedom mobility system using gaseous nitrogen for propulsion, the MMU is equipped with jets for attitude and rotational control, 24 thrusters total, with each providing 7.5 N thrust. The unit is controled from hand controllers used by the pilot, in addition to an automatic attitude control using outputs from a gyroscope pack in the control electronics assembly. EVA periods of 6 hrs are possible with the 150 kg MMU and its fuel complement of 12 kg of gaseous N. Refueling is allowed through an Orbiter interface at the same location the MMU is stowed. The MMU has a delta-V capability of 20 m/sec, with a thrust duration of 7085 N-sec, implying the EVA suit limit will be reached before propellant can be exhausted. The results of various mission simulations for the MMU are reported.
Investigations of high-latitude, middle-atmosphere ion properties have been conducted using rocket probe techniques. Electrodynamics studies have addressed: mesospheric dynamics and small-scale structure (the MAC/EPSILON Campaign during October-November 1977); ionization effects associated with highly energetic greater than or equal to 1 MeV) precipitating electrons (the MAC/REP Program during May 1990); and the characteristics of noctilucent cloud (NLC) and polar mesosphere summer echo (PMSE) regions (the NLC-91 Campaign during July-August 1991). Recent developments in Gerdien condenser probe theory, using computational fluid dynamics to model ion collection, have resulted in more accurate evaluation of the ion mobilities and number densities. Measurements of very small ion mobilities are thought to indicate an aerosol ion presence in the upper mesosphere.
The effects of a 2.0 at.% addition of Ta to a model Ni-Al-Cr superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The addition of Ta results in appreciable strengthening, and the morphology is found to evolve from a bimodal distribution of spheroidal precipitates, to cuboidal precipitates aligned along the elastically soft <001>-type directions. Tantalum is observed to partition preferentially to the gamma -precipitate phase and decreases the mobility of Ni in the gamma- matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma -precipitate/gamma-matrix heterophase interface.
Marshall Space Flight Center mobile communications platform designs for future lunar missions led to improvements to fleets of tactical robots now being deployed by U.S. Army. The Multi-function Agile Remote Control Robot (MARCbot) helps soldiers search out and identify improvised explosive devices. NASA used the MARCbots to test its mobile communications platform, and in working with it, made the robot faster while adding capabilities -- upgrading to a digital camera, encrypting the controllers and video transmission, as well as increasing the range and adding communications abilities. They also simplified the design, providing more plug-and-play sensors and replacing some of the complex electronics with more trouble-free, low-cost components. Applied Geo Technology, a tribally-owned corporation in Choctaw, Mississippi, was given the task of manufacturing the modified robots. The company is now producing 40 units per month, 300 of which have already been deployed overseas.
Proposals for adapting modern airship technologies for military missions have mostly focused on exploiting the airships high flight endurance and low fuel requirement to conduct direct surveillance missions requiring high degrees of persistence over the areas to be observed. While this mission has value, it constrains the airship in two regards. (1) It places all the surveillance sensors, communication systems, and other mission equipment in the airship itself. (2) It requires the airship to be physically in the vicinity of the areas to be directly observed. A more advanced utilization of airship technology would be to add the capability to deploy a separate set of surveillance equipment, thereby enabling indirect and distributed observation operations. This can be undertaken by installing surveillance equipment in a squadron of unmanned aircraft systems (UAS) that can be carried and operated remotely from the airship, and then return to the airship as a base of support. This could be accomplished by deploying 20-30 UASs on an optionally manned (5 person crew) airship. The mission focus of the airship UAS carrier would be for support of distributed intelligence, surveillance and reconnaissance (ISR), close air support (CAS), maritime patrol and interdiction, electronic warfare (EW), persistent area dominance and missile defense. The logic for utilizing an airship carrier over a ground base to deploy UAS will be examined. Whether to be used as a stand-alone platform or in concert with conventional intelligence gathering techniques, the airship UAS carrier can provide the following benefits: a mobile base that will remain accessible despite political fallout which may render a ground base unavailable for use, the psychological impact of a power projection tool that has no geographical limits (imagined in the same way a naval carrier group projects power), cost-saving intelligence gathering over manned alternatives (assumption), and a wider area of influence when compared to an immobile ground base that must facilitate the transfer of UAS to other bases in order to overfly particular areas (all operations, launch, recover, etc. take place from the airship).
This paper will report the status of the Emergency Response Robotics project, a teleoperated mobile robot system being developed at JPL for use by the JPL Fire Department/HAZMAT Team. The project, which began in 1991, has been focused on developing a robotic vehicle which can be quickly deployed by HAZMAT Team personnel for first entry into an incident site. The primary goals of the system are to gain access to the site, locate and identify the hazard, and aid in its mitigation. The involvement of JPL Fire Department/HAZMAT Team personnel has been critical in guiding the design and evaluation of the system. A unique feature of the current robot, called HAZBOT III, is its special design for operation in combustible environments. This includes the use of all solid state electronics, brushless motors, and internal pressurization. Demonstration and testing of the system with HAZMAT Team personnel has shown that teleoperated robots, such as HAZBOT III, can successfully gain access to incident sites locating and identifying hazardous material spills. Work is continuing to enable more complex missions through the addition of appropriate sensor technology and enhancement of the operator interface.
Hall effect and mobility measurements were conducted on undoped Hg(0.8)Cd(0.2)Te crystals which were quenched to room temperature after being subjected to equilibration at temperatures ranging from 400 to 655 C in various Hg atmospheres. The variation of the hole concentration in the cooled crystals at 77 K as a function of Hg's partial pressure at the equilibration temperature, together with a comparison of the hole mobility in the undoped samples with that in copper-doped ones, yields a defect model for the undoped crystals according to which they are intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. In the second part of this paper, the effects of indium doping are considered. The concentration of electrons obtained in the cooled crystals was found to be lower than the intrinsic carrier concentration at the equilibration temperatures. A defect model is proposed according to which most of the indium is incorporated as In2Te3(s) dissolved in the crystal, with only a small fraction of indium acting as single donors occupying Hg lattice sites.
The WALRUS is a wheeled articulating land rover that will provide Ames Research Center with a reliable, autonomous vehicle for demonstrating and evaluating advanced technologies. The vehicle is one component of the Ames Research Center's on-going Human Exploration Demonstration Project. Ames Research Center requested a system capable of traversing a broad spectrum of surface types and obstacles. In addition, this vehicle must have an autonomous navigation and control system on board and its own source of power. The resulting design is a rover that articulates in two planes of motion to allow for increased mobility and stability. The rover is driven by six conical shaped aluminum wheels, each with an independent, internally coupled motor. Mounted on the rover are two housings and a removable remote control system. In the housings, the motor controller board, tilt sensor, navigation circuitry, and QED board are mounted. Finally, the rover's motors and electronics are powered by thirty C-cell rechargeable batteries, which are located in the rover wheels and recharged by a specially designed battery charger.
Water ice nanoclusters are useful analogs for studying a variety of processes that occur within icy grains in the extraterrestrial environment. The surface of ice nanoclusters prepared in the laboratory is similar to the surface of interstellar ice grains. In cold molecular clouds, the silicate cores of interstellar grains are typically approx. 100 nm in diameter and have a coating of impure amorphous water ice. Depositional, thermal and radiolytic processes leave the surface and subsurface molecules in a disordered state. In this state, structural defects become mobile and reactions of trapped gases and small molecules can occur. The large surface area of nanocluster deposits relative to their bulk allows for routine observation of such surface-mediated processes. Furthermore, the disordered surface and subsurface layers in nanocluster deposits mimic the structure of amorphous ice rinds found on interstellar dust grains. Transmission Electron Microscopy (TEM has been used tn characterize the crystallinity, growth mechanism, and size distribution of nanoclusters formed from a mixture of water vapor with an inert carrier gas that has been rapidly cooled to 77K. E M imaging reveals a Gaussian size distribution around a modal diameter that increases from approx. 15 to 30 nm as the percentage of water vapor within the mixture increases from 0.5 to 2.007, respectively . TEM bright and dark field imaging also reveals the crystalline nature of the clusters. h4any of the clusters show a mosaic structure in which crystalline domains originate at the center Other images show mirror planes that are separated by approx. 10 nm. Electron diffraction patterns of these clusters show that the clusters are composed of cubic ice with only a small hexagonal component. Further, the crystalline domain size is approximately the same as the modal diameter suggesting that the clusters are single crystals.
This Technology Description Document (TDD) provides an overview of the technology for the Phase 1 Baseline and Phase 2 Fused demonstrations of the Integrated Arrival, Departure, and Surface (IADS) prototype system of the National Aeronautics and Space Administration’s (NASA) Airspace Technology Demonstration 2 (ATD-2) project, which has been demonstrated since October of 2017 at Charlotte Douglas International Airport (CLT). Development, integration, and field demonstration of relevant technologies of the IADS system directly address recommendations made by the Next Generation Air Transportation System (NextGen) Integration Working Group (NIWG) on Surface and Data Sharing and the Surface Collaborative Decision Making (Surface CDM) concept of operations developed jointly by the Federal Aviation Administration (FAA) and aviation industry partners. NASA has been developing the IADS traffic management system under the ATD-2 project in coordination with the FAA, flight operators, CLT airport operators, and the National Air Traffic Controllers Association (NATCA). The primary goal of ATD-2 is to improve the predictability and operational efficiency of the air traffic system in metroplex environments, through the enhancement, development, and integration of the nation’s most advanced and sophisticated arrival, departure, and surface prediction, scheduling, and management systems. The ATD-2 project is a 5-year research activity beginning in 2015 and extending through 2020. The Phase 1 Baseline IADS capability resulting from the ATD-2 research has been demonstrated at the CLT airport since the beginning of October 2017. Phase 1 provided data exchange and integration with the initial demonstration of the integrated system of strategic and tactical scheduling, collaborative tactical surface metering, tactical departure scheduling to an en route meter point and overhead stream insertion, initial integration of a TFDM SWIM prototype feed, and an early implementation prototype of a Terminal Flight Data Manager (TFDM) Electronic Flight Data (EFD) system. The strategic surface scheduling element of the capability is consistent with the Surface CDM Concept of Operations published in 2014 by the FAA Surface Operations Directorate.1 The Phase 2 Fused IADS system provided substantial updates to baseline IADS Demonstration capability. Improvements were made to the IADS modeler; tactical surface scheduling, and metering; tactical departure scheduling for overhead stream insertion; Electronic Flight Data (EFD) and the integration with the FAA Advanced Electronic Flight Strip (AEFS); RTC/RMTC, and departure trajectories. New capabilities included a TFDM SWIM prototype feed and delivery of IADS data via the TFDM Terminal Publication (TTP) service of the FAA’s SWIM system; strategic surface scheduling and metering as well as fusion with tactical surface metering; integration and ingestion of data from TTP-connected Mobile App and texting industry for General Aviation (GA) flights; and expansion of airspace deployments to include adjacent Center automation, in particular interface with the Atlanta Center (ZTL) arrival metering TBFM system to evaluate pre-scheduling of flights. Improvements in Data Analysis and System Health (DASH) monitoring and updates were completed as well.
In 1997, the United States [NASA] and the Paton Electric Welding Institute are scheduled to cooperate in a flight demonstration on the U.S. Space Shuttle to demonstrate the feasibility of welding in space for a possible repair option for the International Space Station Alpha. This endeavor, known as the International Space Welding Experiment (ISWE), will involve astronauts performing various welding exercises such as brazing, cutting, welding, and coating using an electron beam space welding system that was developed by the E.O. Paton Electric Welding Institute (PWI), Kiev Ukraine. This electron beam welding system known as the "Universal Weld System" consists of hand tools capable of brazing, cutting, autogeneous welding, and coating using an 8 kV (8000 volts) electron beam. The electron beam hand tools have also been developed by the Paton Welding Institute with greater capabilities than the original hand tool, including filler wire feeding, to be used with the Universal Weld System on the U.S. Space Shuttle Bay as part of ISWE. The hand tool(s) known as the Ukrainian Universal Hand [Electron Beam Welding] Tool (UHT) will be utilized for the ISWE Space Shuttle flight welding exercises to perform welding on various metal alloy samples. A total of 61 metal alloy samples, which include 304 stainless steel, Ti-6AI-4V, 2219 aluminum, and 5456 aluminum alloys, have been provided by NASA for the ISWE electron beam welding exercises using the UHT. These samples were chosen to replicate both the U.S. and Russian module materials. The ISWE requires extravehicular activity (EVA) of two astronauts to perform the space shuttle electron beam welding operations of the 61 alloy samples. This study was undertaken to determine if a hazard could exist with ISWE during the electron beam welding exercises in the Space Shuttle Bay using the Ukrainian Universal Weld System with the UHT. The safety issue has been raised with regard to molten metal detachments as a result of several possible causes such as welder procedural error, externally applied impulsive forces(s), filler wire entrainment and snap-out, cutting expulsion, and puddle expulsion. Molten metal detachment from either the weld/cut substrate or weld wire could present harm to a astronaut in the space environment it the detachment was ti burn through the fabric of the astronaut Extravehicular Mobility Unit (EMC). In this paper an experimental test was performed in a 4 ft. x 4 ft. vacuum chamber at MSFC enabling protective garment to be exposed to the molten metal drop detachments to over 12 inches. The chamber was evacuated to vacuum levels of at least 1 x 10(exp -5) torr (50 micro-torr) during operation of the 1.0 kW Universal Hand Tool (UHT). The UHT was manually operated at the power mode appropriate for each material and thickness. The space suit protective welding garment, made of Teflon fabric (10 oz. per yard) with a plain weave, was placed on the floor of the vacuum chamber to catch the molten metal drop detachments. A pendulum release mechanism consisting of four hammers, each weighing approximately 3.65 lbs, was used to apply an impact forces to the weld sample/plate during both the electron beam welding and cutting exercises. Measurements were made of the horizontal fling distances of the detached molten metal drops. The volume of a molten metal drop can also be estimated from the size of the cut. Utilizing equations, calculations were made to determine chande in surafec area (Delat a(surface)) for 304 stainless steel for cutting based on measurements of metal drop sizes at the cut edges. For the cut sample of 304 stainless steel based on measurement of the drop size at the edge, Delta-a(surface) was determined to be 0.0054 2 in . Calculations have indicated only a small amount of energy is required to detach a liquid metal drop. For example, approximately only 0.000005 ft-lb of energy is necessary to detach a liquid metal steel drop based on the above theoretical analysis. However, some of the energy will be absorbed by the plate before it reaches the metal drop. Based on the theoretical calculations, it was determined that during a weld cutting exercise, the titanium alloy would be the most difficult to detach molten metal droplets followed by stainless steel and then by aluminum. The results of the experimental effort have shown that molten metal will detach if large enough of a hammer blow is applied to the weld sample plate during the full penetration welding and cutting exercises. However, no molten metal detachments occurred as a result of the filler wire snap-out tests from the weld puddle since it was too difficult to cause the metal to flick-out from the pool. Molten metal detachments, though not large in size, did result from the direct application of the electron beam on the end of the filler weld wire.
A high-performance MODFET structure grown by MBE with the incorporation of a single quantum well In(0.15)Ga(0.85)As layer for the transport of two-dimensional electron gas has been critically examined for its thermal stability at 80 K and low-frequency noise form 0.01 to 10 to the 8th Hz. Experimental results indicate that the behavior of this device in both these respects is much superior when compared with the same behavior of conventional MODFETs. A maximum low-field carrier mobility of 29,000 sq cm/s at 80 K and an average carrier saturation velocity of 2 x 10 to the 7th cm/s at 300 K in a 1-micron gate device clearly indicate that the quality of the pseudomorphic quantum well (InGaAs) layer is either comparable or better than that of the usual GaAs buffer layer. The deep level spectra, obtained through photo-FET measurements, and the low-frequency noise spectra at different temperatures obtained for the new pseudomorphic and conventional MODFET's have clearly indicated that contributions from various deep levels present in the new structure are significantly reduced.
Radiation belts around Planets have sufficient high energy electron flux to penetrate spacecraft skins and statically charge insulators inside the electronic boxes. For example, geosynchronous-orbit Earth spacecraft require 100 mils aluminum shielding to sufficiently attenuate the fast electron flux. Electrons are stopped and accumulate slowly in the insulated materials to produce strong electric fields. Typically the field strength achieves a threshold for occasional spontaneous discharge in the insulating material. The field strength remains high yet pulsing is infrequent. Charge can leak off if the insulator is sufficiently leaky. The conductivity of insulators is usually controlled by mobile ions such as H and OH in ground service. In space the mobile ions are eventually out-gassed. The resistivity of several insulators is known to increase over three decades after exposure to vacuum for several months. Insulators in space were seen to pulse more frequently as they aged.
LED Helmet Extravehicular Activity Helmet Interchangeable Portable (LEHIP) lights for the Extravehicular Mobility Unit (EMU) have been built and tested and are currently being used on the International Space Station. A design is presented of the passive thermal control system consisting of a chamber filled with aluminum foam and wax. A thermal math model of LEHIP was built and correlated by test to show that the thermal design maintains electronic components within hot and cold limits for a 7 hour spacewalk in the most extreme EVA average environments, and do not pose a hazard to the crew or to components of the EMU.
Optical coatings of disordered thin film SiO,/SiO, samples undergoing electron beam bombardment exhibited a cathodoluminescence effect. Measurements were made of the absolute illuminance and emission spectra as functions of incident electron energy (0.2 keV to 30 keV). flux (approx. 0.1 nA/sq cm to > 100 nA/sq cm) and power (<50 nW/sq cm to > 3mW/sq cm) for coatings (approx.60 nm to approx.200 nm thick) on reflective metal substrates over a range of sample temperatures (approx.40 K to approx.400 K) and emission wavelengths (approx.260 nm to approx.5000 nm). Illuminance reached a plateau saturation intensity I(sub sat) approx. 10(exp -4)W/sq cm. scaling as [I(sub mc)/(I + I(sub mc)/I(sub sat)] as incident power I(sub mc) approached I(sub sat). Well below I(sub sat), illuminance scaled linearly with incident power for lower-energy non-penetrating radiation that deposited all of its energy in the dielectric film. At higher incident energies (> 1-5 keV) electrons penetrate the dielectric, depositing only a fraction of their energy in the dielectric film, where deposited energy scales as the ratio of film thickness to penetration range. Since electron range exhibits a peak below approx. 1 keV, the illuminance decreased with increasing energy for penetrating radiation. The temperature dependence of the illuminance. in general, increased with decreasing temperature. Changes in apparent color with temperature were also observed. Four bands in the UV/VIS/NIR range from 300 nm to 1000 nm were observed in spectral measurements; no significant luminescence was detected in a range from approx. 1000 nm to approx. 5000 nm. These different bands either increased or decreased in intensity and shifted slightly in energy with decreasing temperature. Our measurements are explained in terms of simple disordered band theory models based on atomic-scale stochastic transport of electrons in highly disordered insulating materials. The theoretical models provide a fundamental basis for understanding the dependence of cathodoluminescence on irradiation time, incident flux and energy. and sample thickness and temperature. The observed luminescence occurs when an incident high energy electron excites a valence band electron into the conduction band. Following the excitation. a complex series of transitions take place between the extended conduction states and the long-lived localized trapped states (or chromophores) associated with structural or compositional defects in the dielectric materials. Thc transport equations and models of thc spatial and energy distribution of the trapped states below the mobility edge, their occupancy, and transitions provide microscopic scale insights into this macroscopic phenomenon. Our observations and theoretical models are also compared with similar previous room temperature studies of similar SiO2 films.