Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “exploration techniques”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Innovative Balloon Buoyancy Techniques for Atmospheric Exploration

Until quite recently, the only practical means to control balloon buoyancy, and thus altitude, required consuming large amounts of fuel or the limited venting of helium balloons and/or dropping of ballast. With recent discoveries at JPL, novel long-life, balloon buoyancy techniques have been discovered that for the first time allow balloons to float in the primarily hydrogen atmospheres of Jupiter, Saturn, Uranus, and Neptune (using ambient fill-gas), and by using renewable energy sources, allow multiple controlled landings on Venus (using atmospheric temperature differences), Mars (solar heat), Titan (RTG heat), and Earth (planet radiant heat).

Balloon Planetary Aerobot Buoyancy Mars Titan Venu↗
DOE OSTI2018

Electron microscopy techniques employed to explore mitochondrial defects in the developing rat brain following ketamine treatment

Ketamine, an FDA-approved N-methyl-D-aspartate (NMDA) receptor antagonist, is commonly used for general pediatric anesthesia. Accumulating evidence has indicated that prolonged exposure to ketamine induces widespread apoptotic cell death in the developing brains of experimental animals. Although mitochondria are known to play a pivotal role in cell death, little is known about the alterations in mitochondrial ultrastructure that occur during ketamine-induced neurotoxicity. The objective of this pilot study was to utilize classic and contemporary methods in electron microscopy to study the impact of ketamine on the structure of mitochondria in the developing rat brain. While transmission electron microscopy (TEM) was employed to comprehensively study mitochondrial inner membrane topology, serial block-face scanning electron microscopy (SBF-SEM) was used as a complementary technique to compare the overall mitochondrial morphology from a representative treated and untreated neuron. In this study, postnatal day 7 (PND-7) Sprague-Dawley rats were treated with ketamine or saline (6 subcutaneous injections × 20 mg/kg or 10 ml/kg, respectively, at 2-h intervals with a 6-h withdrawal period after the last injection, n=6 each group). Samples from the frontal cortex were harvested and analyzed using TEM or SBF-SEM. While classic TEM revealed that repeated ketamine exposure induces significant mitochondrial swelling in neurons, the newer technique of SBF-SEM confirmed the mitochondrial swelling in three dimensions (3D) and showed that ketamine exposure may also induce mitochondrial fission, which was not observable in the two dimensions (2D) of TEM. Furthermore, 3D statistical analysis of these reconstructed mitochondria appeared to show that ketamine-treated mitochondria had significantly larger volumes per unit surface area than mitochondria from the untreated neuron. The ultrastructural mitochondrial alterations demonstrated here by TEM and SBF-SEM support ketamine’s proposed mechanism of neurotoxicity in the developing rat brain.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1979

Neutron-gamma techniques for planetary exploration

Chemical analysis of planetary surfaces is necessary for the understanding of the origin and evolutionary processes of the solar system. Orbital lunar geochemical experiments performed during the Apollo 15 and 16 demonstrated that even with a low neutron flux (fast and thermal), reliable results could be extracted. The possibility of using a compact 14 MeV neutron generator for geochemical analysis of planetary surfaces, comets and asteroids is currently studied. This method allows the determination of bulk chemical composition, even in the presence of an atmosphere. This would be possible on the surface of Venus, for example, where alternate methods such as sample return are impractical. This method can be used for continuous monitoring of elemental abundances from a roving vehicle, for example, on the surface of Mars.

Johnson, R. G.↗
NASA NTRS2016

Exploring Surface Analysis Techniques for the Detection of Molecular Contaminants on Spacecraft

Molecular contamination is a known area of concern for spacecraft. To mitigate this risk, projects involving space flight hardware set requirements in a contamination control plan that establishes an allocation budget for the exposure of non-volatile residues (NVR) onto critical surfaces. The purpose of this work will focus on non-contact surface analysis and in situ monitoring to mitigate molecular contamination on space flight hardware. By using Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM-EDS) with Raman Spectroscopy, an unlikely contaminant was identified on space flight hardware. Using traditional and surface analysis methods provided the broader view of the contamination sources allowing for best fit solutions to prevent any future exposure.

Rutherford, Gugu N.↗
NASA NTRSDate not supplied

A Rapid Target-Search Technique for KBO Exploration Trajectories

A rapid, grid-based, target-search algorithm is presented to find candidate se-quences of small-body encounters for mission design. The algorithm is especially relevant for cases with large combinatorial spaces. In this paper, the al-gorithm is used to identify candidate flyby sequences of multiple Kuiper-Belt Ob-jects (KBOs). Before reaching the first KBO in the sequence, the trajectories in this paper first use gravity assists at one or more of the giant planets to pump-uptheir orbital energy—reducing launch C3. The target-search algorithm consists offour sequential steps: (1) parameter definition, (2) fine-tuned Lambert-based gridsearch of ballistic trajectories visiting one KBO, (3) rapid, ∆V-based proximitysearch for additional KBOs using the state transition matrices (STMs), and (4) tra-jectory optimization of the most promising KBO sequences using the EvolutionaryMission Trajectory Generator (EMTG). The paper also defines an empirical-basedprocess to characterize the maximum step size for the target arrival dates in theLambert grid search. Lastly, a candidate mission to two KBOs is presented. Theresults indicate that the ∆V computed from the STM propagations is not repre-sentative of the final ∆V computed in EMTG; however, it does serve as a useful‘reachability’ metric to identify nearby KBOs.

Miguel Benayas Penas↗
NASA NTRS1984

Spin dynamics and horizon sensor performance for the Solar Mesosphere Explorer

Numerical techniques for obtaining the trigger altitude of the Solar Mesosphere Explorer (SME) are detailed. The SME has a pair of fixed horizon sensors for attitude determination and initiation of the data acquisition procedures for measuring ozone concentrations at the limb. The spacecraft spin rate is calculated as each of the horizon sensors marks the limb with a pulse telemetered to the ground. A best fit spin dynamics model that takes into account the history of the satellite spin angle and all disturbances to the spin is described. Analyses show that the trigger altitude is calculated to an accuracy of 1.5-2.0 km. A significant indicator of the limb altitude is the stratospheric temperature at the 5 mb pressure level.

Lawrence, G. M.↗
NASA NTRS2000

Dynamic Stall Characteristics of Drooped Leading Edge Airfoils

Helicopters in high-speed forward flight usually experience large regions of dynamic stall over the retreating side of the rotor disk. The rapid variations in the lift and pitching moments associated with the stall process can result in vibratory loads, and can cause fatigue and failure of pitch links. In some instances, the large time lag between the aerodynamic forces and the blade motion can trigger stall flutter. A number of techniques for the alleviation of dynamic stall have been proposed and studied by researchers. Passive and active control techniques have both been explored. Passive techniques include the use of high solidity rotors that reduce the lift coefficients of individual blades, leading edge slots and leading edge slats. Active control techniques include steady and unsteady blowing, and dynamically deformable leading edge (DDLE) airfoils. Considerable amount of experimental and numerical data has been collected on the effectiveness of these concepts. One concept that has not received as much attention is the drooped-leading edge airfoil idea. It has been observed in wind tunnel studies and flight tests that drooped leading edge airfoils can have a milder dynamic stall, with a significantly milder load hysteresis. Drooped leading edge airfoils may not, however, be suitable at other conditions, e.g. in hover, or in transonic flow. Work needs to be done on the analysis and design of drooped leading edge airfoils for efficient operation in a variety of flight regimes (hover, dynamic stall, and transonic flow). One concept that is worthy of investigation is the dynamically drooping airfoil, where the leading edge shape is changed roughly once-per-rev to mitigate the dynamic stall.

Sankar, Lakshmi N.↗
DOE OSTI2014

SU-F-BRE-12: Optical Resonator Water Calorimeter

Purpose: Water calorimetry based on resistance thermometry has matured as a primary standard. Developing an optical technique hold the promise to push the boundaries of what is currently achievable with dosimetry. We will present a feasibility study and the current progress of construction of a Fabry-Perot resonator for dose to water measurement. Additionally, estimations of the theoretical limits resonator sensitivity and potential sources of noise for the system are described. Methods: A temperature change from the dose to water would be measured by the change in the index of refraction from the water in the cavity. Calculations are presented of the expected signal from the resonator for dose to water. The Fabry-Perot resonator constructed from optical quality narrowband mirrors is described. A water cell will be inserted into the cavity gap to provide the medium swept cavity length technique is explored as a specific implementation of this technique. Results: Calculations indicate that a dose to water on the order of a Gray is measureable with a reasonably implementable system. A resonator is currently under construction and progress towards a proof of principle measurement will be presented. The primary sources of noise, in order of importance, are expected to be; optical absorption by the medium, mechanical perturbations of the cavity length and thermal expansion of the optical mounts. Estimations of these noise sources and mitigation techniques will be discussed. Conclusion: A Fabry-Perot resonator is a promising technique for measuring the absorbed dose to water from a radiotherapy beam. This technique has the potential to serve as a check on the current primary standard for dose to water measurements. As well, i0074 may be the foundation for a new class of optical property based dosimetry measurement.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS1977

Infrared and millimeter wave techniques for the Cosmic Background Explorer Satellite

The Cosmic Background Explorer Satellite will employ infrared and microwave techniques to gain information about the very early universe. Three instruments will cover the spectral range from 8 microns to 13 mm, determining both the spectrum and angular distribution of the large scale background radiation fields. A cryogenic polarizing Michelson interferometric spectrometer will measure the spectrum of the 3 deg K relic radiation from the big bang with precision. Four differential microwave radiometers will map the sky from 23 to 90 GHz in a search for anisotropy of the universe. A broadband cryogenic IR photometer will map zodiacal dust emission, galactic dust, and an extragalactic residual component.

Mather, J. C.↗