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DOE OSTI2023

Modeling of the spray-induced wall stress acting on the ignition assistance device

This research introduces a novel wall-stress model called the Spray-Induced Wall Stress (SIWS) model, which considers the effects of spray-wall impingement and the resulting formation of wall stress within the Lagrangian spray modeling framework. The primary objective of this paper is to provide a mathematical description of the fundamental physics underlying the model. Subsequently, the proposed model is validated using existing experimental data. Here, the remainder of the study focuses on the practical application of the model to an ignition assistance device. Specifically, this device is installed in a compression ignition engine and designed to enhance ignition in aviation-fueled high-altitude aircraft propulsion systems. The research sheds light on the mechanical impulse caused by the high-speed impact of the spray jet, leading to the accumulation of mechanical stress on the rigid body of the ignition assistance device. Previous studies on fluid-structure interaction have only considered the interaction between the gas phase and the solid wall. However, the SIWS model incorporates the additional impact of the impinging liquid spray jet. Consequently, the simulated stress distribution on the ignition assistance device can be estimated by considering both the gas-phase-induced term and the spray-induced term simultaneously.

33 ADVANCED PROPULSION SYSTEMS↗

NASA NTRS2018

Influence of Load Profile on Biomechanics of the Squat and Deadlift

Long duration space travel will expose astronauts to extended periods of reduced gravity. Since gravity is not present to assist loading, astronauts will use resistive and aerobic exercise regimes for the duration of the space flight to counteract the effect reduced gravity has on the body. Astronauts will exercise on a flywheel based device on the second Orion Exploration Mission (EM2). The effect that the flywheel load profile has on biomechanics is unknown when compared to free weights or a simulated free weight profile. The purpose of this evaluation is to compare the differences in lower body kinematics and kinetics between the flywheel and free weight profile. Test subjects were instrumented with reflective markers for motion capture data collection while exercising on the Device for Aerobic and Resistive Training (DART) prototype developed by TDA Research, Inc. of Wheat Ridge, CO. Exercises performed were either the squat while wearing a harness or deadlift while grasping a T-bar, both of which interfaced with the DART through a rope cable. The DART, a motorized device controlled via software, is capable of producing different load profiles. Profiles include simulated free weights with adjustable eccentric overload capability and flywheel. Test variables included the applied device load and the load profile, both set through the DART software interface. Motion capture data was collected with a 12 camera system (Smart-DX, BTS Bioengineering, Brooklyn, NY). Bilateral ground reaction force data were collected with force plates (P6000, BTS Bioengineering). DART cable force was recorded through an internal load cell. Data was collected from a total of four test subjects. The three repetition maximum was determined for each test subject for both squat and deadlift. High, medium and low loads were determined based on this maximum. The test subject performed five repetitions of each exercise at each load and each test trial was repeated twice. Cadence was controlled during exercising. Biomechanical data were used to drive the models utilizing the OpenSim software platform. Subject specific models were scaled to match the anthropometrics of the test subjects and used to estimate the peak joint angle, joint range of motion, the peak joint moment and the joint moment impulse of the lower extremity joints and the lumbar joint.These are preliminary results because the data analysis is ongoing. There was a lot of inter-subject variability, however, in general, there was a greater peak lumbar flexion angle for the flywheel squat exercise. There was a trend towards a greater range of motion at the hip for the squat exercise with free weight. There was also a greater hip extension, lumbar extension and ankle plantar flexion impulse moment during the squat exercise with free weight. During the deadlift exercise, the peak knee flexion angle and peak knee extension moment were greater when using the free weight profile. For deadlift, the hip extension, lumbar extension and ankle plantar flexion impulse moment tended to be greater with the free weight profile. Overall, the kinematic and kinetic outcomes for the flywheel profile were either statistically the same as free weight profile in many cases, significantly reduced in a few cases, and rarely higher.

Bioengineering↗

NASA NTRS2023

Solar Flare Ribbon Fronts. I. Constraining Flare Energy Deposition with IRIS Spectroscopy

Spectral lines formed at lower atmospheric layers show peculiar profiles at the "leading edge" of ribbons during solar flares. In particular, increased absorption of the BBSO/GST He I λ10830 line, as well as broad and centrally reversed profiles in the spectra of the Mg II and C II lines observed by the IRIS satellite, has been reported. In this work, we aim to understand the physical origin of such peculiar IRIS profiles, which seem to be common of many, if not all, flares. To achieve this, we quantify the spectral properties of the IRIS Mg II profiles at the ribbon leading edge during four large flares and perform a detailed comparison with a grid of radiative hydrodynamic models using the RADYN+FP code. We also studied their transition region (TR) counterparts, finding that these ribbon front locations are regions where TR emission and chromospheric evaporation are considerably weaker compared to other parts of the ribbons. Based on our comparison between the IRIS observations and modeling, our interpretation is that there are different heating regimes at play in the leading edge and the main bright part of the ribbons. More specifically, we suggest that bombardment of the chromosphere by more gradual and modest nonthermal electron energy fluxes can qualitatively explain the IRIS observations at the ribbon leading front, while stronger and more impulsive energy fluxes are required to drive chromospheric evaporation and more intense TR emission in the bright ribbon. Our results provide a possible physical origin for the peculiar behavior of the IRIS chromospheric lines in the ribbon leading edge and new constraints for the flare models.

Solar flares↗

DOE OSTI2022

A Novel Fault Diagnosis Approach for Rolling Bearing Based on CWT and Adaptive Sparse Representation

Extraction and enhancement of weak impulse signature is the key of rolling bearing fault prognostics in which case the features are often weak and covered by noise. Tunable Q-factor wavelet transform (TQWT), as an emerging wavelet construction theory developed in a frequency domain explicitly, has the advantages of matching with the specific oscillation behavior of signal components. In this article, an adaptive sparse representation (ASR) method is proposed, which integrates the sparse code shrinkage (SCS) and parameter optimization into TQWT. However, direct application of ASR is difficult to extract fault signatures at the early stage or low-speed operation due to weak fault symptoms and background noise. A novel fault diagnosis strategy based on continuous wavelet transform (CWT) and ASR is investigated. CWT owns significant advantages on multiscale subdivision and weak signal detection. The results of simulated and experimental vibration signal analyses verify the effectiveness of the proposed method in accurately extracting weak impulse features from the noise environment.

Yuan, Xing↗

NASA NTRS1987

Energetics and dynamics of simple impulsive solar flares

Flare energetics and dynamics were studied using observations of simple impulsive spike bursts. A large, homogeneous set of events was selected to enable the most definite tests possible of competing flare models, in the absence of spatially resolved observations. The emission mechanisms and specific flare models that were considered in this investigation are described, and the derivations of the parameters that were tested are presented. Results of the correlation analysis between soft and hard X-ray energetics are also presented. The ion conduction front model and tests of that model with the well-observed spike bursts are described. Finally, conclusions drawn from this investigation and suggestions for future studies are discussed.

Starr, R.↗

NASA NTRS1988

Energetics and dynamics of simple impulsive solar flares

Starr, R.↗

NASA NTRS2010

Advanced Spectroscopic and Thermal Imaging Instrumentation for Shock Tube and Ballistic Range Facilities

The Electric Arc Shock Tube (EAST) facility and Hypervelocity Free Flight Aerodynamic Facility (HFFAF, an aeroballistic range) at NASA Ames support basic research in aerothermodynamic phenomena of atmospheric entry, specifically shock layer radiation spectroscopy, convective and radiative heat transfer, and transition to turbulence. Innovative optical instrumentation has been developed and implemented to meet the challenges posed from obtaining such data in these impulse facilities. Spatially and spectrally resolved measurements of absolute radiance of a travelling shock wave in EAST are acquired using multiplexed, time-gated imaging spectrographs. Nearly complete spectral coverage from the vacuum ultraviolet to the near infrared is possible in a single experiment. Time-gated thermal imaging of ballistic range models in flight enables quantitative, global measurements of surface temperature. These images can be interpreted to determine convective heat transfer rates and reveal transition to turbulence due to isolated and distributed surface roughness at hypersonic velocities. The focus of this paper is a detailed description of the optical instrumentation currently in use in the EAST and HFFAF.

Grinstead, Jay H.↗

NASA NTRS2010

Advanced Spectroscopic and Thermal Imaging Instrumentation for Shock Tube and Ballistic Range Facilities

Grinstead, Jay H.↗

NASA NTRS2003

Living with a Star: New Opportunities in Sun-Climate Research

Living With a Star is a NASA initiative employing the combination of dedicated spacecraft with targeted research and modeling efforts to improve what we know of solar effects of all kinds on the Earth and its surrounding space environment, with particular emphasis on those that have significant practical impacts on life and society. The highest priority among these concerns is the subject of this report: the potential effects of solar variability on regional and global climate, including the extent to which solar variability has contributed to the well-documented warming of the Earth in the last 100 years. Understanding how the climate system reacts to external forcing from the Sun will also greatly improve our knowledge of how climate will respond to other climate drivers, including those of anthropogenic origin. A parallel element of the LWS program addresses solar effects on space weather : the impulsive emissions of charged particles, short-wave electromagnetic radiation and magnetic disturbances in the upper atmosphere and near-Earth environment that also affect life and society. These include a wide variety of solar impacts on aeronautics, astronautics, electric power transmission, and national defense. Specific examples are (1) the impacts of potentially- damaging high energy radiation and atomic particles of solar origin on satellites and satellite operations, spacecraft electronics systems and components, electronic communications, electric power distribution grids, navigational and GPS systems, and high altitude aircraft; and (2) the threat of sporadic, high-energy solar radiation to astronauts and high altitude aircraft passengers and crews. Elements of the LWS program include an array of dedicated spacecraft in near- Earth and near-Sun orbits that will closely study and observe both the Sun itself and the impacts of its variations on the Earth's radiation belts and magnetosphere, the upper atmosphere, and ionosphere. These spacecraft, positioned to study and monitor changing conditions in the Sun-Earth neighborhood, will also serve as sentinels of solar storms and impulsive events.

Source record↗

NASA NTRS1979

A Ganymede lander mission

The paper addresses the dynamical problem and question of technical feasibility associated with delivering a simple, semi-hard lander to one of the Galilean satellites, Ganymede. Emphasis is placed on the identification of a viable, not necessarily optimal, baseline trajectory and maneuver sequence. Simplicity is stressed in the lander's use of two fixed-impulse solid rockets for landing maneuvers. It is shown through an error analysis that navigation and maneuver execution errors can be compensated on the baseline descent trajectory by controlling just the thrust direction. Finally, specific subsystem capabilities needed on the lander to achieve a successful touchdown within a specific performance envelope are also identified.

Boain, R. J.↗

NASA NTRS1986

The solar flare extreme ultraviolet to hard X-ray ratio

Simultaneous measurements of the peak 10-1030 A extreme ultraviolet (EUV) flux enhancement and more than 10 keV hard X-ray (HXR) peak flux of many solar flare bursts, ranging over about four orders of magnitude in HXR intensity, are studied. A real departure from linearity is found in the relationship between the peak EUV and HXR fluxes in impulsive flare bursts. This relationship is well described by a given power law. Comparison of the predictions of the impulsive nonthermal thick-target electron beam model with observations shows that the model satisfactorily predicts the observed time differences between the HXR and EUV peaks and explains the data very well under given specific assumptions. It is concluded that the high-energy fluxes implied by the invariant area thick-target model cannot be completely ruled out, while the invariant area model with smaller low cutoff requires impossibly large beam densities. A later alternative thick-target model is suggested.

Mcclymont, A. N.↗

NASA NTRS2013

Control Requirements to Support Manual Piloting Capability

The manual piloting requirements specified under the NASA Constellation Program involved Cooper-Harper ratings, which are a qualitative and subjective evaluation from experienced pilots. This type of verification entails a significant investment of resources to assess a completed design and is not one that can easily or meaningfully be applied upfront in the design phase. The evolution of the Multi-Purpose Crew Vehicle Program to include an independently developed propulsion system from an international partner makes application of Cooper-Harper based design requirements inadequate. To mitigate this issue, a novel solution was developed to reformulate the necessary piloting capability into quantifiable requirements. A trio of requirements was designed which specify control authority, precision, and impulse residuals enabling propulsion design within specified guidance and control boundaries. These requirements have been evaluated against both the existing Orion design and the proposed ESA design and have been found to achieve the desired specificity. The requirement set is capable of being applied to the development of other spacecraft in support of manual piloting.

Merancy, Nujoud↗

NASA NTRS1990

Method and apparatus for determining time, direction, and composition of impacting space particles

A space particle collector for recording the time specific particles are captured, and its direction at the time of capture, utilizes an array of targets, each comprised of an MOS capacitor on a chip charged from an external source and discharged upon impact by a particle through a tab on the chip that serves as a fuse. Any impacting particle creates a crater, but only the first will cause a discharge of the capacitor. A substantial part of the metal film around the first crater is burned off by the discharge current. The time of the impulse which burns the tab, and the identification of the target, is recorded together with data from flight instruments. The metal film is partitioned into pie sections to provide a plurality of targets on each of an array of silicon wafers, thus increasing the total number of identified particles that can be collected. It is thus certain which particles were captured at what specific times.

Kinard, William H.↗

NASA NTRS2012

2011-2012 Dryden Center Innovation Fund End of the Year Report: Altitude-Compensating Rocket Nozzles

This report highlights one of the many successful projects at the NASA Dryden Flight Research Center that was approved for FY12 funding under the Center Innovation Fund. This project was focused on advancing the technology readiness level of one specific type of altitude-compensating nozzle: the dual-bell rocket nozzle. When considering a rocket's performance over its entire integrated trajectory, the dual-bell nozzle has been predicted to achieve a higher total impulse over the conventional bell nozzle, which is expected to result in a greater capability of payload mass to low-Earth orbit. Although the dual-bell rocket nozzle has been thoroughly studied for several decades, this nozzle has still not been adequately tested in a relevant flight-like environment. This report provides highlights and top-level details on the FY12 feasibility effort to advance this promising technology through flight test, a collaborative effort which leverages NASA Marshall's dual-bell nozzle research and development with Dryden's expertise in propulsion-focused flight testing. To accomplish this goal, the NASA F-15B is proposed as the testbed for the initial flight-test campaign to advance this greatly needed capability.

Jones, Daniel S.↗

NASA NTRS1998

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, can be correlated with well characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us, for the first time, to quantitatively characterize actual g-jitter effects on an actual crystal growth experiment and to properly calibrate our models of g-jitter effects on crystal growth.

Favier, J.-J.↗

NASA NTRS1999

Study of Interesting Solidification Phenomena on the Ground and in Space (MEPHISTO)

Real-time Seebeck voltage variations in a Sn-Bi melt during directional solidification in the MEPHISTO spaceflight experiment flown on the USMP-3 mission, have been correlated with well-characterized thruster firings and an Orbiter Main System (OMS) burn. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-crystal interface. This allowed us to make a direct comparison of numerical simulations with the experimentally obtained Seebeck signals. Based on the results of preflight and real-time computations, several well-defined thruster firing events were programmed to occur at specific times during the experiment. In particular, we simulated the effects of the thruster firings on melt and crystal composition in a directionally solidifying Sn-Bi alloy. The relative accelerations produced by the firings were simulated by impulsive accelerations of the same magnitude, duration and orientation as the requested firings. A comparison of the simulation results with the Seebeck signal indicates that there is a good agreement between the two. This unique opportunity allows us to make the first quantitative characterization of actual g-jitter effects on an actual crystal growth experiment and to calibrate our models of g-jitter effects on crystal growth.

Alexander, J. Iwan D.↗

NASA NTRS1988

Planetographic clustering of low-altitude impulsive electric signals in the night ionosphere of Venus

This paper presents maps of the locations of electromagnetic signals, presumably caused by lightning, which were observed at 730 Hz during the first three nighttime observing seasons of Pioneer Venus Orbiter when the spacecraft reached altitudes low enough to detect the signals. The maps show that there are specific 'active regions' of enhanced signal occurrence, and that at least some of these active regions appear to remain fixed in planetographic coordinates from year to year.

Russel, C. T.↗

NASA NTRS1992

Observations of the solar corona with a high resolution EUV imaging spectrograph

An extreme ultraviolet imaging spectrograph was used to obtain coronal observations with high spectral and spatial resolution. The imaging properties of the instrument enable measurements of spectral line shapes and positions in discrete spatial elements of a region, so that the dynamic characteristics of the coronal plasma, as well as the distribution of emission measure with temperature and well known density diagnostics, can be studied for specific features. The instrumentation is described and several results of a sounding rocket flight on 5 May 1989, when the corona over NOAA Region 5464 including emission over the umbra of the region's largest sunspot and the pre-impulsive phase emission of a small flare was recorded, are summarized.

Neupert, Werner M.↗