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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Advanced X-Ray Sources Ensure Safe Environments

Ames Research Center awarded inXitu Inc. (formerly Microwave Power Technology), of Mountain View, California, an SBIR contract to develop a new design of electron optics for forming and focusing electron beams that is applicable to a broad class of vacuum electron devices. This technology offers an inherently rugged and more efficient X-ray source for material analysis; a compact and rugged X-ray source for smaller rovers on future Mars missions; and electron beam sources to reduce undesirable emissions from small, widely distributed pollution sources; and remediation of polluted sites.

Source record↗
NASA NTRS1986

Technology for Television

A project being conducted by Varian Associates, Inc. and Lewis Research Center would allow a Ultrahigh Frequency (UHF) TV station to save 50% of its electricity cost. Because UHF stations need substantially more transmitter power, an amplifying device was needed. In the early 1970's Dr. Henry Kosmahl of Lewis had developed a radiowave amplifier to improve satellite transmission. He later worked with modifying klystron transmitters, electronic vacuum tubes used to generate and amplify UHF frequencies. If Dr. Kosmahl's multistage depressed collector or MDC can be incorporated into the klystron, the magnetic field shapes of electron beams can be changed to aid the energy recovery function of the MDC.

Source record↗
NASA NTRS2002

Power-Efficient, High-Current-Density, Long-Life Thermionic Cathode Developed for Microwave Amplifier Applications

A power-efficient, miniature, easily manufactured, reservoir-type barium-dispenser thermionic cathode has been developed that offers the significant advantages of simultaneous high electron-emission current density (>2 A/sq cm) and very long life (>100,000 hr of continuous operation) when compared with the commonly used impregnated-type barium-dispenser cathodes. Important applications of this cathode are a wide variety of microwave and millimeter-wave vacuum electronic devices, where high output power and reliability (long life) are essential. We also expect it to enable the practical development of higher purveyance electron guns for lower voltage and more reliable device operation. The low cathode heater power and reduced size and mass are expected to be particularly beneficial in traveling-wave-tube amplifiers (TWTA's) for space communications, where future NASA mission requirements include smaller onboard spacecraft systems, higher data transmission rates (high frequency and output power) and greater electrical efficiency.

Wintucky, Edwin G.↗
NASA NTRS1975

Effect of electron irradiation in vacuum on FEP-A silicon solar cell covers

Fluorinated ethylene-propylene-A (FEP-A) covers on silicon solar cells were irradiated with 1-MeV electrons, in vacuum, to an accumulated fluence equivalent to approximately 28 years in synchronous orbit. The effect of irradiation on the light transmittance of FEP-A was checked by measuring the short-circuit current of the cells after each dose increment. The results indicate no apparent overall loss in transmission due to irradiation of FEP-A. Filter wheel measurements revealed some darkening of the FEP-A at the blue end of the spectrum. Although no delamination from the cell surface was observed while in vacuum, embrittlement of FEP-A occurred at the accumulated dose.

Marsik, S. J.↗
NASA NTRS1985

Miscibility Gap Systems

Immiscible droplets embedded in a host fluid in which a temperature gradient exists migrate toward the hot end of the host fluid because of the temperature dependence of the interfacial energy of the droplet. This thermocapillary migration effect was exploited in the design of a controllable heat valve which is the thermal analog of the electronic vacuum triode. Studies have also been made of test cells that could use thermocapillary migration to facilitate the study of condensation and dissolution kinetics in miscibility-gap solutions.

Schmid, L. A.↗
NASA NTRS2001

Micromachined TWTs for THz Radiation Sources

The Terahertz (THz) region of the electromagnetic spectrum (about 300 - 3000 GHz in frequency or about 0.1 - 1 mm free space wavelength) has enormous potential for high-data-rate communications, spectroscopy, astronomy, space research, medicine, biology, surveillance, remote sensing, industrial process control, etc. It has been characterized as the most scientifically rich, yet under-utilized, region of the electromagnetic spectrum. The most critical roadblock to full exploitation of the THz band is lack of coherent radiation sources that are powerful (0.001 - 1.0 W continuous wave), efficient (> 1%), frequency agile (instantaneously tunable over 1% bandwidths or more), reliable, and comparatively inexpensive. To develop vacuum electron device (VED) radiation sources satisfying these requirements, fabrication and packaging approaches must be heavily considered to minimize costs, in addition to the basic interaction physics and circuit design. To minimize size of the prime power supply, beam voltage must be minimized, preferably 10 kV. Solid state sources satisfy the low voltage requirement, but are many orders of magnitude below power, efficiency, and bandwidth requirements. On the other hand, typical fast-wave VED sources in this regime (e.g., gyrotrons, FELs) tend to be large, expensive, high voltage and very high power devices unsuitable for most of the applications cited above. VEDs based on grating or inter-digital (ID) circuits have been researched and developed. However, achieving forward-wave amplifier operation with instantaneous fractional bandwidths > 1% is problematic for these devices with low-energy (< 15 kV) electron beams. Moreover, the interaction impedance is quite low unless the beam-circuit spacing is kept particularly narrow, often leading to significant beam interception. One solution to satisfy the THz source requirements mentioned above is to develop micromachined VEDs, or "micro-VEDs". Among other benefits, micro-machining technologies provide superior high frequency wall conductivity as a result of superior surface smoothness compared with conventional mechanical or electric discharge machining approaches. Micro-VED technologies are already being applied to the development of millimeter-wave klystrons at Stanford Linear Accelerator Center and submillimeter-wave klystrons at the University of Leeds. We are investigating the use of micro-machining technologies to develop THz regime TWTs, with emphasis on folded-waveguide TWTs. The folded-waveguide TWT (FW-TWT) has several features that make it attractive for THz-regime micro-VED applications. It is a relatively simple circuit to design and fabricate, it is amenable to precision pattern replication by micro-machining, and it is has been demonstrated capable of forward-wave amplification with appreciable bandwidth. We are conducting experimental and computational studies of micro-VED FW-TWTs to examine their feasibility for applications at frequencies from 200 - 1000 GHz.

Booske, John H.↗
NASA NTRS2002

A Low Cost Traveling Wave Tube for Wireless Communications

Demand for high data rate wireless communications is pushing up amplifier power, bandwidth and frequency requirements. Some systems are using vacuum electron devices again because solid-state power amplifiers are not able to efficiently meet the new requirements. The traveling wave tube is the VED of choice because of its excellent broadband capability as well as high power efficiency and frequency. But TWTs are very expensive on a per watt basis below about 200 watts of output power. We propose a new traveling wave tube that utilizes cathode ray tube construction technology and electrostatic focusing. We believe the tube can be built in quantity for under $1,000 each. We discuss several traveling wave tube slow wave circuits that lend themselves to the new construction. We will present modeling results and data on prototype devices.

Vancil, Bernard Kenneth↗
NASA NTRS2002

Test and Analysis Capabilities of the Space Environment Effects Team at Marshall Space Flight Center

Marshall Space Flight Center has developed world-class space environmental effects testing facilities to simulate the space environment. The combined environmental effects test system exposes temperature-controlled samples to simultaneous protons, high- and low-energy electrons, vacuum ultraviolet (VUV) radiation, and near-ultraviolet (NUV) radiation. Separate chambers for studying the effects of NUV and VUV at elevated temperatures are also available. The Atomic Oxygen Beam Facility exposes samples to atomic oxygen of 5 eV energy to simulate low-Earth orbit (LEO). The LEO space plasma simulators are used to study current collection to biased spacecraft surfaces, arcing from insulators and electrical conductivity of materials. Plasma propulsion techniques are analyzed using the Marshall magnetic mirror system. The micro light gas gun simulates micrometeoroid and space debris impacts. Candidate materials and hardware for spacecraft can be evaluated for durability in the space environment with a variety of analytical techniques. Mass, solar absorptance, infrared emittance, transmission, reflectance, bidirectional reflectance distribution function, and surface morphology characterization can be performed. The data from the space environmental effects testing facilities, combined with analytical results from flight experiments, enable the Environmental Effects Group to determine optimum materials for use on spacecraft.

Finckenor, M. M.↗
NASA NTRS2007

High-Power, High-Efficiency Ka-Band Space Traveling-Wave Tube

The L-3 Communications Model 999H traveling-wave tube (TWT) has been demonstrated to generate an output power of 144 W at 60-percent overall efficiency in continuous-wave operation over the frequency band from 31.8 to 32.3 GHz. The best TWT heretofore commercially available for operation in the affected frequency band is characterized by an output power of only 35 W and an efficiency of 50 percent. Moreover, whereas prior TWTs are limited to single output power levels, it has been shown that the output power of the Model 999H can be varied from 54 to 144 W. A TWT is a vacuum electronic device used to amplify microwave signals. TWTs are typically used in free-space communication systems because they are capable of operating at power and efficiency levels significantly higher than those of solid-state devices. In a TWT, an electron beam is generated by an electron gun consisting of a cathode, focusing electrodes, and an anode. The electrons pass through a hole in the anode and are focused into a cylindrical beam by a stack of periodic permanent magnets and travel along the axis of an electrically conductive helix, along which propagates an electromagnetic wave that has been launched by an input signal that is to be amplified. The beam travels within the helix at a velocity close to the phase velocity of the electromagnetic wave. The electromagnetic field decelerates some of the electrons and accelerates others, causing the beam to become formed into electron bunches, which further interact with the electromagnetic wave in such a manner as to surrender kinetic energy to the wave, thereby amplifying the wave. The net result is to amplify the input signal by a factor of about 100,000. After the electrons have passed along the helix, they impinge on electrodes in a collector. The collector decelerates the electrons in such a manner as to recover most of the remaining kinetic energy and thereby significantly increase the power efficiency of the TWT.

Krawczyk, Richard↗
NASA NTRS2001

Terahertz-Regime, Micro-VEDs: Evaluation of Micromachined TWT Conceptual Designs

Summary form only given. The Terahertz (THz) region of the electromagnetic spectrum (approx.300-3000 GHz) has enormous potential for high-data-rate communications, spectroscopy, astronomy, space research, medicine, biology, surveillance, remote sensing, industrial process control, etc. The most critical roadblock to full exploitation of the THz band is lack of coherent radiation sources that are powerful (0.01-10.0 W continuous wave), efficient (>1 %), frequency agile (instantaneously tunable over 1% bandwidths or more), reliable, and relatively inexpensive. Micro-machined Vacuum Electron Devices (micro-VEDs) represent a promising solution. We describe prospects for miniature, THz-regime TWTs fabricated using micromachining techniques. Several approx.600 GHz conceptual designs are compared. Their expected performance has been analyzed using SD, 2.51), and 3D TWT codes. A folded waveguide (FWG) TWT forward-wave amplifier design is presented based on a Northrop Grumman (NGC) optimized design procedure. This conceptual device is compared to the simulated performance of a novel, micro-VED helix TWT. Conceptual FWG TWT backward-wave amplifiers and oscillators are also discussed. A scaled (100 GHz) FWG TWT operating at a relatively low voltage (-12 kV) is under development at NGC. Also, actual-size micromachining experiments are planned to evaluate the feasibility of arrays of micro-VED TWTs. Progress and results of these efforts are described. This work was supported, in part by AFOSR, ONR, and NSF.

Booske, John H.↗
NASA NTRS2008

Vacuum microelectronics and miniature instruments based on application specific electrode-integrated nanotube cathodes (ASINCs)

JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles thay routinely produce > 15 A/cm2 at 5 to 8 V/μm applied fields for extreme environment vacuum electronics and miniature instrumentation. These cathodes have been monolithically integrated with additional electrodes using double siliconon-insulator process.

Mojarradi, M.M.↗
NASA NTRSDate not supplied

Advanced Material Options for the Portable Life Support System

Meeting an aggressive mass requirement is a challenge for new space suit development efforts, including that of the Exploration Extravehicular Mobility Unit Portable Life Support System (PLSS) government reference design. To reduce overall system mass, titanium was selected as the primary metal for the PLSS backplate and thermal loop. However, galvanically compatible metals (Hastelloy, Inconel, Monel) have relatively high densities and require further design complexities such as coatings and more challenging manufacturing. Efforts to reduce the mass of the government reference design for an International Space Station (ISS) or lunar mission were halted due to the government’s transition to a commercial Extravehicular Activity (EVA) services approach, but research was conducted into methodologies for mass savings using advanced materials. With the advent of a lunar Artemis mission and potential for future Mars missions, mass becomes a more critical driver going forward. Therefore, alternative materials and processes must be considered to fully close the mass requirement. There are many new materials and processes that can be considered; however, considerations must be made to ensure galvanic compatibility, radiation concerns for sensitive electronics, vacuum compatibility, tight tolerances, fluid compatibility with oxygen and water, and thread insert options. Individual PLSS components may have different requirements and need to be considered separately for reducing overall mass. This report will touch on comparisons between advanced materials, focusing on composites, additive manufacturing, and plastics. It will also address the different processes that may need to be applied when using these materials in the harsh environment of space. Lastly, it will look at specific components and make recommendations for options to reduce the mass of each one.

Ryan Ogilvie↗
NASA NTRS2024

Advanced Material Options for the Portable Life Support System (PLSS)

Meeting an aggressive mass requirement is a challenge for new space suit development efforts, including that of the Exploration Extravehicular Mobility Unit Portable Life Support System (PLSS) government reference design. To reduce overall system mass, titanium was selected as the primary metal for the PLSS backplate and thermal loop. However, galvanically compatible metals (Hastelloy, Inconel, Monel) have relatively high densities and require further design complexities such as coatings and more challenging manufacturing. Efforts to reduce the mass of the government reference design for an International Space Station (ISS) or lunar mission were halted due to the government’s transition to a commercial Extravehicular Activity (EVA) services approach, but research was conducted into methodologies for mass savings using advanced materials. With the advent of a lunar Artemis mission and potential for future Mars missions, mass becomes a more critical driver going forward. Therefore, alternative materials and processes must be considered to fully close the mass requirement. There are many new materials and processes that can be considered; however, considerations must be made to ensure galvanic compatibility, radiation concerns for sensitive electronics, vacuum compatibility, tight tolerances, fluid compatibility with oxygen and water, and thread insert options. Individual PLSS components may have different requirements and need to be considered separately for reducing overall mass. This report will touch on comparisons between advanced materials, focusing on composites, additive manufacturing, and plastics. It will also address the different processes that may need to be applied when using these materials in the harsh environment of space. Lastly, it will look at specific components and make recommendations for options to reduce the mass of each one.

Ryan Ogilvie↗