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Results for “Marx generator”

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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18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Linear Transformer Drivers for Z-pinch Based Propulsion

The MSFC/UAH team has been developing of a novel power management and distribution system called a Linear Transformer Driver (LTD). LTD's hold the promise of dramatically reducing the required mass to drive a z-pinch by replacing the capacitor banks which constitute half the mass of the entire system. The MSFC?UAH tea, is developing this technology in hope of integrating it with the Pulsed Fission Fusion (PuFF) propulsion concept. High-Voltage pulsed power systems used for Z-Pinch experimentation have in the past largely been based on Marx Generators. Marx generators deliver the voltage and current required for the Z-Pinch, but suffer from two significant drawbacks when applied to a flight system: they are very massive, consisting of high-voltage capacitor banks insulated in oil-filled tanks and they do not lend themselves to rapid pulsing. The overall goal of Phase 2 is to demonstrate the construction of a higher voltage stack from a number of cavities each of the design proven in Phase 1 and to characterize and understand the techniques for designing the stack. The overall goal of Phase 3 is to demonstrate the feasibility of constructing a higher energy cavity from a number of smaller LTD stacks, to characterize and understand the way in which the constituent stacks combine, and to extend this demonstration LTD to serve as the basis for a 64 kJ pulse generator for Z-Pinch experiments.

Adams, Robert↗
NASA NTRS1988

Description of a new full scale lightning simulation facility

A lightning test facility has been constructed in Utah, and the facility has initially been used to test and certify solid rocket motor (SRM) segment shipping containers. The simulator equipment consists of a 17-stage 1.7 MV Marx generator and three current generators. The performance of the Marx is enhanced by use of a distributed peaking capacitor to produce maximum dl/dt's in excess of 4 x 10 to the 11th Amps/sec into large test objects. The current generators consist of the following: (1) a 200 KA underdamped 500 kilojoule high current bank, (2) a critically damped intermediate current bank and (3) an over damped continuing current bank. Total charge transfer for these banks is 270 Coulombs with an action integral in excess of 8 x 10 to the 6th sq Amps-sec. Representative results for the simulator and SRM segment shipping containers are presented.

Papazian, Peter B.↗
NASA NTRS1980

F-5F Shark Nose radome lightning test

A unique F-5F radome wtih a geometry similar to a Shark Nose profile was tested with a high voltage Marx generator, 1,200,000 volts in order to demonstrate the effectiveness of the lightning protection system with currents from 5,000 amperes or greater. An edge discontinuity configuration is a characteristic feature in the forward region of the radome and occasionally serves as an attachment point. The results of nineteen attachment tests at various aspect angles with an air gap of one meter indicated that no damage occurred to the dielectric material of the radom. The test proved the effectiveness of the lightning protection system.

Scott, G. W.↗
NASA NTRS1990

RSRM top hat cover simulator lightning test, volume 1

The test sequence was to measure electric and magnetic fields induced inside a redesigned solid rocket motor case when a simulated lightning discharge strikes an exposed top hat cover simulator. The test sequence was conducted between 21 June and 17 July 1990. Thirty-six high rate-of-rise Marx generator discharges and eight high current bank discharges were injected onto three different test article configurations. Attach points included three locations on the top hat cover simulator and two locations on the mounting bolts. Top hat cover simulator and mounting bolt damage and grain cover damage was observed. Overall electric field levels were well below 30 kilowatts/meter. Electric field levels ranged from 184.7 to 345.9 volts/meter and magnetic field levels were calculated from 6.921 to 39.73 amperes/meter. It is recommended that the redesigned solid rocket motor top hat cover be used in Configuration 1 or Configuration 2 as an interim lightning protection device until a lightweight cover can be designed.

Source record↗
NASA NTRS1968

High-voltage pulse generator developed for wide-gap spark chambers

Low-inductance, high-capacitance Marx pulse generator provides for minimization of internal inductance and suppression of external electromagnetic radiation. The spark gaps of the generator are enclosed in a pressurized nitrogen atmosphere which allows the charging voltage to be varied by changing the nitrogen pressure.

Keller, L. P.↗
NASA NTRS2018

Polymer-Filled Metal Foams for Contamination Resistant Aircraft Leading Edges

Adhesion of contaminants has been identified as a ubiquitous issue for aeronautic exterior surfaces. Organic coatings have been demonstrated to enable reduction in insect residue adhesion as well as a reduction in ice adhesion strength. These approaches however, have yet to demonstrate sufficient durability to enable application to commercial aircraft wing leading edges. High durability materials have been developed in parallel to these efforts; contaminant adhesion issues are not addressed. This work describes a first attempt to identify a solution to the seemingly competing issues of contaminant adhesion and durability. A co-continuous network of organic and metallic domains may provide greater durability, while still enabling the changes in surface-contaminant interactions that have been realized. To that end, unique properties have been achieved through fabrication of composite metal foam materials. Likewise, extensive research has been dedicated toward development of polymeric coatings for mitigation of insect residue adhesion.This work describes initial results from infusion of a low surface free energy epoxy resin into a composite metal foam substrate for the purpose of generating a durable contaminant adhesion-resistant material.

Robbins, Samuel J.↗
NASA NTRS1982

Fabricating Structural Beams

Automatic machine described in new report has demonstrated on Earth feasibility of machine fabricating beams for huge structures in space. Such structures include solar mirrors, radiometer reflectors, microwave power transmitters, solar-thermal power generators, and solar photoelectric generators, ranging in size from few hundred meters long to tens of kilometers long.

Engler, E. E.↗
NASA NTRS1976

RF shaping of silicon ribbon

Electromagnetic force generated by radiofrequency coil is used to shape molten silicon. Shaping coil surrounds melt near solid-liquid interface and induces current in surface region of melt nearly equal to but opposite coil current.

Pelhank, D. A.↗
NASA NTRS1989

NASA/MSFC nozzle test bed

As part of an effort to improve the state-of-the-art in nozzle technology, a solid propulsion test bed facility is being designed and will be located at Marshall Space Flight Center. The test bed will consist of a plasma arc facility and several small scale rocket motor test facilities ranging in size from the ballistic environmental generator motor with a 1/2 in. diameter throat to the MNASA motor with a 9 and 1/2 in. diameter throat capability. The test bed system will be used primarily to study materials behavior from the standpoint of char, erosion, and thermal stress phenomena.

Crose, James G.↗
NASA NTRS2018

Hybrid Lyot Coronagraph for WFIRST: High Contrast Testbed Demonstration in Flight-like Low Flux Environment

In order to validate required operation of the proposed Wide-Field InfraRed Survey Telescope (WFIRST) coronagraph instrument, we have built a testbed in Jet Propulsion Laboratory (JPL), which is analogous to the baseline WFIRST coronagraph instrument architecture. Since its birth in 2016, this testbed, named as Occulting Mask Coronagraph (OMC) testbed, has demonstrated several crucial technological milestones: Broadband high contrast demonstration in both Hybrid Lyot Coronagraph (HLC) and Shape Pupil Coronagraph (SPC) modes while the Low Order Wavefront Sensing and Control (LOWFS/C) subsystem senses and corrects the dynamic flight-like wavefront disturbances. In this paper, we present up-to-date progress of HLC mode demonstration in the OMC testbed. While injecting the flight-like low photon flux starlight with expected Line of Sight (LoS) and Wavefront Error (WFE) perturbation to the OMC testbed, we demonstrate generating high contrast dark hole images. We first study the expected photon flux in actual flight environment, and estimate detection noise and estimation accuracy of the complex electric field if the wavefront sensing algorithm is used based on the pair-wise difference imaging. Then, we introduce our improved scheme to mitigate this photon-starved flight-like low flux environment. As a result, we generate a dark hole that meets the WFIRST raw contrast requirements using the 2nd magnitude star light. We establish the key ideas, describe test setups, and demonstrate test results with data analysis.

Wilson, Daniel↗
NASA NTRS2017

Optimizing the Regularization in Broadband Wavefront Control Algorithm for WFIRST Coronagraph

The WFIRST/AFTA 2.4 m space telescope currently under study includes a stellar coronagraph for the imaging and the spectral characterization of extrasolar planets. The coronagraph employs sequential deformable mirrors to compensate for phase and amplitude errors. Using the optical model of an Occulting Mask Coronagraph (OMC) testbed at the Jet Propulsion Laboratory (JPL), we have investigated and compared through modeling and simulations the performance of several actuator regularization-schemes in broadband wavefront control algorithm used to generate dark holes in an OMC, such as a Hybrid Lyot Coronagraph (HLC). Using the concept of a Tikhonov filter constituting the G-matrix, we have explained what the different regularization schemes do to singular-modes during a wavefront control process called Electric Field Conjugation (EFC). In some cases we confirmed the numerical predictions with the testbed measured results. We present our findings in this paper.

Sidick, Erkin↗
NASA NTRS1995

A study of lightning in winter thunderstorms and the analysis of thunderstorm overflight data

Thunderstorms and the activities associated with them was the emphasis of this final report. The primary goal of the investigation of the dynamics, microphysics, and the electrical properties of tropical thunderstorms, was to understand the process or processes which initiate the precipitation in various convective clouds. A concept that the degree of atmospheric instability that determines the updraft velocity is different between those storms that generate electrical activity and those that do not. This is apparent in temperate latitudes, but in tropical regions, little knowledge of these interactions is available. Several ground monitoring stations have been set up and, along with a waveform recorder at one of the stations, the data collected from these stations will be analyzed in conjunction with other data collected from ship and airborne radars and airborne in situ measurements of electrical activity in coordination with the TOGA-COARE program.

Brook, Marx↗
NASA NTRS2017

Dynamic Testbed Demonstration of WFIRST Coronagraph Low Order Wavefront Sensing and Control (LOWFS/C)

To maintain the required performance of WFIRST Coronagraph in a realistic space environment, a Low Order Wavefront Sensing and Control (LOWFS/C) subsystem is necessary. The LOWFS/C uses a Zernike wavefront sensor (ZWFS) with the phase shifting disk combined with the starlight rejecting occulting mask. For wavefront error corrections, WFIRST LOWFS/C uses a fast steering mirror (FSM) for line-of-sight (LoS) correction, a focusing mirror for focus drift correction, and one of the two deformable mirrors (DM) for other low order wavefront error (WFE) correction. As a part of technology development and demonstration for WFIRST Coronagraph, a dedicated Occulting Mask Coronagraph (OMC) testbed has been built and commissioned. With its configuration similar to the WFIRST flight coronagraph instrument the OMC testbed consists of two coronagraph modes, Shaped Pupil Coronagraph (SPC) and Hybrid Lyot Coronagraph (HLC), a low order wavefront sensor (LOWFS), and an optical telescope assembly (OTA) simulator which can generate realistic LoS drift and jitter as well as low order wavefront error that would be induced by the WFIRST telescope’s vibration and thermal changes. In this paper, we will introduce the concept of WFIRST LOWFS/C, describe the OMC testbed, and present the testbed results of LOWFS sensor performance. We will also present our recent results from the dynamic coronagraph tests in which we have demonstrated of using LOWFS/C to maintain the coronagraph contrast with the presence of WFIRST-like line-of-sight and low order wavefront disturbances.

Zhou, Hanying↗
NASA NTRS2018

Pulsed Fission-Fusion (PuFF)

In September 2013 the NASA Innovative Advanced Concept (NIAC) organization awarded a phase I contract to the PuFF team. Our phase 1 proposal discussed a pulsed fission-fusion propulsion system that injected gaseous deuterium (D) and tritium (T) as a mixture in a column, surrounded concentrically by gaseous uranium fluoride (UF6) and then an outer shell of liquid lithium. A high power current would flow down the liquid lithium and the resulting Lorentz force would compress the column by roughly a factor of 10. The compressed column would reach criticality and a combination of fission and fusion reactions would occur. The fission reactions would further energize the fusion center, and the fusion reactions would generate neutrons that promote more complete burnup of the fission fuel. The lithium liner provides some help as a neutron reflector but also acts as a propulsive medium, being converted to plasma which is then expanded against a magnetic nozzle for thrust. The expansion of the (primarily) lithium plasma against the nozzle's magnetic field inducts a current that is used to charge the system for the next pulse. Our concept also included secondary injection of a Field Reversed Configuration (FRC) plasmoid that would provide a secondary compression direction, axially against the column, and push the column away from the injection manifold, increasing the manifold's survivability.Our phase 1 proposal included modeling the above process first under steady state assumptions and second under a time variant integration. We proposed including these results into a Mars concept vehicle and finally proposing promising conditions to be evaluated experimentally in Phase II. In phase I we quickly realized that we needed to modify our approach. Our steady state work was completed as proposed, and the results indicated that one, a two stage compression system was not needed and two, that we wanted to move away from UF6. The steady state model shows much more margin than expected, to the point that we may well reach breakeven with the Charger – 1 facility, a 572 kJ Marx bank currently under refurbishment at UAH. Additionally we found that using gaseous D-T and UF6, provided a relatively simple prospect of using a pulsed injector, made reaching criticality more difficult. The introduction of large amounts of fluorine meant a radiative sink, sapping power from the fusion plasma and was harder to handle. Therefore we moved to a solid uranium target that held D-T under pressure. In so doing we could move our target closer to criticality and remove any material that did not sustain the reaction.

Fusion↗
NASA NTRS2018

Infrared Computer-Generated Holograms: Design and Application for the WFIRST Grism Using Wavelength-Tuning Interferometry

Interferometers using computer-generated holograms (CGHs) have become the industry standard to accurately measure aspheric optics. The CGH is a diffractive optical element that can create a phase or amplitude distribution and can be manufactured with low uncertainty using modern lithographic techniques. However, these CGHs have conventionally been used with visible light and piezo-shifting interferometers. Testing the performance of transmissive optics in the infrared requires infrared CGHs and an infrared interferometer. Such an instrument is used in this investigation, which introduces its phase shift via wavelength-tuning. A procedure on how to design and manufacture infrared CGHs and how these were successfully used to model and measure the Wide-Field Infrared Survey Telescope grism elements is provided. Additionally, the paper provides a parametric model, simulation results, and calculations of the errors and measurements that come about when interferometers introduce a phase variation via wavelength-tuning interferometry to measure precision aspheres.

Communication↗
NASA NTRS2021

High Contrast Imaging With MEMS Deformable Mirrors in the Decadal Survey Testbed

Deformable mirrors (DMs) are an essential part of any coronagraphic, high contrast instrument. They mitigate optical aberrations in the system and can even be used to generate contrast for the coronagraph. MEMS DMs from Boston Micromachines have been selected as the baseline for two flagship space telescopes proposed to the 2020 Decadal Survey. Although MEMS DMs have over a decade of heritage on ground-based telescopes and in in-air testbeds around the globe, they have not been tested in vacuum down to the ∼10−10 contrast level needed to image terrestrial exoplanets. In this paper, we describe vacuum tests of MEMS DMs in the Decadal Survey Testbed at the Jet Propulsion Laboratory. The first challenge was a bright, temporally incoherent signal, which was identified as electronics noise and removed with a low-pass filter. After that, the contrast has been limited in broadband light by the strong print-through on the DM surfaces. We performed numerical simulations to confirm that conclusion and to characterize the improvements needed to the MEMS DM surfaces and the testbed layout to attain our goal of 10−10 contrast.

Seo, Byoung-Joon↗
NASA NTRSDate not supplied

Model Validation of Phase-Induced Amplitude Apodization Complex Mask Coronagraph for LUVOIR-A in Vacuum

The Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is a coronagraph architecture for the next generation of large space telescopes optimized for habitable exoplanet imaging that can achieve attractive theoretical performance with high throughput at small inner working angles (IWA). PIAACMC designs are compatible with large, on-axis, segmented apertures such as the Large UV / Optical/ Infrared A (LUVOIR-A) concept currently being considered by the decadal survey review which would greatly enhance the possibility to achieve statistically significant scientific yields and signal quality for direct imaging exoplanet surveys. PIAACMC has been recently implemented for LUVOIR-A and is currently being tested in vacuum at JPL’s High-Contrast Imaging Testbed (HCIT). In this work, we review the theoretical performance of the PIAACMC instrument designed to meet a 1e-9 raw contrast goal in 10% broadband light in a region from 2-8 L/D both before and after the wavefront control loop. We use empirical measurements from the vacuum testbed to verify the instrument model and its performance including line-of-sight errors, instrument alignment, and fabricated components. In particular, the model verification includes measured sags of the manufactured PIAA mirrors by NuTek. The CMC mask was manufactured at JPL’s Microdevices Laboratory and we include surface profile characterization measurement. We assess the impact on performance of the different manufacturing and alignment errors.

High-Contrast Imaging↗