Power systems research at MSFC

Power systems research reviews at Marshall Space Flight Cente

Energy loss mechanism for suspended micro- and nanoresonators due to the Casimir force

A so far not considered energy loss mechanism in suspended micro- and nanoresonators due to noncontact acoustical energy loss is investigated theoretically. The mechanism consists on the conversion of the mechanical energy from the vibratory motion of the resonator into acoustic waves on large nearby structures, such as the substrate, due to the coupling between the resonator and those structures resulting from the Casimir force acting over the separation gaps. Analytical expressions for the resulting quality factor Q for cantilever and bridge micro- and nanoresonators in close proximity to an underlying substrate are derived and the relevance of the mechanism is investigated, demonstrating its importance when nanometric gaps are involved

New Models for a Triaxial Milky Way Spheroid and Effect on the Microlensing Optical Depth to the Large Magellanic Cloud

We obtain models for a triaxial Milky Way spheroid based on data by Newberg and Yanny. The best fits to the data occur for a spheroid center that is shifted by 3kpc from the Galactic Center. We investigate effects of the triaxiality on the microlensing optical depth to the Large Magellanic Cloud (LMC). The optical depth can be used to ascertain the number of Massive Compact Halo Objects (MACHOs); a larger spheroid contribution would imply fewer Halo MACHOs. On the one hand, the triaxiality gives rise to more spheroid mass along the line of sight between us and the LMC and thus a larger optical depth. However, shifting the spheroid center leads to an effect that goes in the other direction: the best fit to the spheroid center is_away_ from the line of sight to the LMC. As a consequence, these two effects tend to cancel so that the change in optical depth due to the Newberg/Yanny triaxial halo is at most 50%. After subtracting the spheroid contribution in the four models we consider, the MACHO contribution (central value) to the mass of the Galactic Halo varies from \~(8-20)% if all excess lensing events observed by the MACHO collaboration are assumed to be due to MACHOs. Here the maximum is due to the original MACHO collaboration results and the minimum is consistent with 0% at the 1 sigma error level in the data.Comment: 26 pages, 2 figures. v2: minor revisions. v3: expanded discussion of the local spheroid density and minor revisions to match version published in Journal of Cosmology and Astroparticle Physics (JCAP

Wannier-Stark ladders in one-dimensional elastic systems

The optical analogues of Bloch oscillations and their associated Wannier-Stark ladders have been recently analyzed. In this paper we propose an elastic realization of these ladders, employing for this purpose the torsional vibrations of specially designed one-dimensional elastic systems. We have measured, for the first time, the ladder wave amplitudes, which are not directly accessible either in the quantum mechanical or optical cases. The wave amplitudes are spatially localized and coincide rather well with theoretically predicted amplitudes. The rods we analyze can be used to localize different frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let

Artemis Curation: Preparing for Sample Return from the Lunar South Pole

Space Policy Directive-1 mandates that the United States will lead the return of humans to the Moon for long-term exploration and utilization, followed by human missions to Mars and other destinations. In addition, the Vice President stated that It is the stated policy of this administration and the United States of America to return American astronauts to the Moon within the next five years, that is, by 2024. These efforts, under the umbrella of the recently formed Artemis Program, include such historic goals as the flight of the first woman to the Moon and the exploration of the lunar south-polar region. Among the top priorities of the Artemis Program is the return of a suite of geologic samples, providing new and significant opportunities for progressing lunar science and human exploration. In particular, successful sample return is necessary for understanding the history of volatiles in the Solar System and the evolution of the Earth-Moon system, fully constraining the hazards of the lunar polar environment for astronauts, and providing the necessary data for constraining the abundance and distribution of resources for in-situ resource utilization (ISRU). Here we summarize the ef-forts of the Astromaterials Acquisition and Curation Office (hereafter referred to as the Curation Office) to ensure the success of Artemis sample return (per NASA Policy Directive (NPD) 7100.10E)

Anomalous quantum chaotic behavior in nanoelectromechanical structures

It is predicted that for sufficiently strong electron-phonon coupling an anomalous quantum chaotic behavior develops in certain types of suspended electro-mechanical nanostructures, here comprised by a thin cylindrical quantum dot (billiard) on a suspended rectangular dielectric plate. The deformation potential and piezoelectric interactions are considered. As a result of the electron-phonon coupling between the two systems the spectral statistics of the electro-mechanic eigenenergies exhibit an anomalous behavior. If the center of the quantum dot is located at one of the symmetry axes of the rectangular plate, the energy level distributions correspond to the Gaussian Orthogonal Ensemble (GOE), otherwise they belong to the Gaussian Unitary Ensemble (GUE), even though the system is time-reversal invariant.Comment: 4 pages, pdf forma