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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Experimental Investigation of a Direct-drive Hall Thruster and Solar Array System at Power Levels up to 10 kW

As NASA considers future exploration missions, high-power solar-electric propulsion (SEP) plays a prominent role in achieving many mission goals. Studies of high-power SEP systems (i.e. tens to hundreds of kilowatts) suggest that significant mass savings may be realized by implementing a direct-drive power system, so NASA recently established the National Direct-Drive Testbed to examine technical issues identified by previous investigations. The testbed includes a 12-kW solar array and power control station designed to power single and multiple Hall thrusters over a wide range of voltages and currents. In this paper, single Hall thruster operation directly from solar array output at discharge voltages of 200 to 450 V and discharge powers of 1 to 10 kW is reported. Hall thruster control and operation is shown to be simple and no different than for operation on conventional power supplies. Thruster and power system electrical oscillations were investigated over a large range of operating conditions and with different filter capacitances. Thruster oscillations were the same as for conventional power supplies, did not adversely affect solar array operation, and were independent of filter capacitance from 8 to 80 ?F. Solar array current and voltage oscillations were very small compared to their mean values and showed a modest dependence on capacitor size. No instabilities or anomalous behavior were observed in the thruster or power system at any operating condition investigated, including near and at the array peak power point. Thruster startup using the anode propellant flow as the power 'switch' was shown to be simple and reliable with system transients mitigated by the proper selection of filter capacitance size. Shutdown via cutoff of propellant flow was also demonstrated. A simple electrical circuit model was developed and is shown to have good agreement with the experimental data.

Snyder, John S.↗
NASA NTRS2015

Optimization of an Aeroservoelastic Wing with Distributed Multiple Control Surfaces

This paper considers the aeroelastic optimization of a subsonic transport wingbox under a variety of static and dynamic aeroelastic constraints. Three types of design variables are utilized: structural variables (skin thickness, stiffener details), the quasi-steady deflection scheduling of a series of control surfaces distributed along the trailing edge for maneuver load alleviation and trim attainment, and the design details of an LQR controller, which commands oscillatory hinge moments into those same control surfaces. Optimization problems are solved where a closed loop flutter constraint is forced to satisfy the required flight margin, and mass reduction benefits are realized by relaxing the open loop flutter requirements.

Stanford, Bret K.↗
NASA NTRS1981

Effect of elastic end rings on the eigenfrequencies of thin cylinders

The effect of elastic end rings on the eigenfrequencies of thin cylindrical shells is studied by using an exact solution of the linear eigenvalue problem. The out-of-plane and torsional rigidities of the rings are responsible for the overall shell stiffness. Considerable mode interaction exists for modes with low circumferential wave numbers when the mass of the ring is comparable with that of the shell. The hypothetical simply supported and clamped boundary conditions are practically impossible to realize with a finite-mass ring for relatively short and thin shells.

El Raheb, M.↗
NASA NTRS1997

Human life support for advanced space exploration

The requirements for a human life support system for long-duration space missions are reviewed. The system design of a controlled ecological life support system is briefly described, followed by a more detailed account of the study of the conceptual design of a Lunar Based CELSS. The latter is to provide a safe, reliable, recycling lunar base life support system based on a hybrid physicochemical/biological representative technology. The most important conclusion reached by this study is that implementation of a completely recycling CELSS approach for a lunar base is not only feasible, but eminently practical. On a cumulative launch mass basis, a 4-person Lunar Base CELSS would pay for itself in approximately 2.6 years relative to a physicochemical air/water recycling system with resupply of food from the Earth. For crew sizes of 30 and 100, the breakeven point would come even sooner, after 2.1 and 1.7 years, respectively, due to the increased mass savings that can be realized with the larger plant growth units. Two other conclusions are particularly important with regard to the orientation of future research and technology development. First, the mass estimates of the Lunar Base CELSS indicate that a primary design objective in implementing this kind of system must be to minimized the mass and power requirement of the food production plant growth units, which greatly surpass those of the other air and water recycling systems. Consequently, substantial research must be directed at identifying ways to produce food more efficiently. On the other hand, detailed studies to identify the best technology options for the other subsystems should not be expected to produce dramatic reductions in either mass or power requirement of a Lunar Base CELSS. The most crucial evaluation criterion must, therefore, be the capability for functional integration of these technologies into the ultimate design of the system. Secondly, this study illustrates that existing or near-term technologies are adequate to implement a Lunar Base CELSS. There are no apparent "show-stoppers" which require the development of new technologies. However, there are several areas in which new materials and technologies could be used for a more efficient implementation of the system, e.g., by decreasing mass or power requirement and increasing recycling efficiency. These areas must be further addressed through research and development. Finally, although this study focused on the development of a Lunar Base CELSS, the same technologies and a nearly identical design would be appropriate for a Mars base. Actually, except for the distance of transportation, the implementation of a CELSS on Mars would even be easier than it would be on the Moon. The presence of atmospheric CO2 on Mars, although in low concentration, coupled with the fact that the day/night cycle on Mars is very similar to that on Earth, makes the use of light-weight, greenhouse-like structures for growing food plants even more feasible than on the Moon. There are some environmental problems, which would have to be dealt with, like dust storms and the large amount of the ultraviolet radiation incident on the planet's surface. However, the materials and methods are largely available today to develop such a life support system for a Mars base.

Review, Tutorial↗
NASA NTRS1995

A Segmented Time-of-Flight Mass Spectrometer

The present paper describes the design of a time-of-flight mass spectrometer (TOFMS) in which the single flight tube of a conventional TOFMS has been replaced by several cylindrical electrostatic lenses in tandem. By a judicious choice of voltages on these lenses, an improved TOFMS has been realized which has a superior mass and energy resolution, shorter flight lengths, excellent signal-to-noise ratio and less stringent requirements on the bias voltages.

Srivastava, S. K.↗
NASA NTRS1994

A Segmented Time-of-Flight Mass Spectrometer

A time-of-flight mass spectrometer (TOFMS) is described in which the single flight tube of a conventional TOFMS has been replaced by several cylindrical electrostatic lenses in tandem. By a judicious choice of voltages on these lenses, an improved TOFMS has been realized which has a superior mass and energy resolution, shorter flight lengths, excellent signal-to-noise ratio, and less stringent requirements on the bias voltages.

time-of-flight↗
NASA NTRS1956

Zero-angle-of-attack Performance of Two-dimensional Inlets near Mach Number 3

An extensive program was undertaken to investigate the effect of several geometric variables on the performance of two-dimensional inlets. This investigation included inlets having single-wedge, double-wedge, and isentropic compression ramps with various side-plate configurations and subsonic diffusers. The tests were conducted over a range of Reynolds number based on inlet height from 0.50 to 2.67(sup x)10(sup 6). Generally, the performance levels of the two-dimensional inlets were somewhat below those obtained previously with comparable axisymmetric models. At Mach number 3.05 the optimum total-pressure recovery was obtained with an isentropic inlet which compressed the external flow to a Mach number of 1.88. Rectangular side plates and a long high-exit-Mach-number subsonic diffuser with filleted corners were used with this inlet. A critical total-pressure recovery of 0.71 was realized with a corresponding mass-flow ratio of 0.965. Subcritical stability to a mass-flow ratio of 0.60 was obtained.

Woollett, Richard R↗
NASA NTRS1998

Pulsed Plasma Thruster Technology Development and Flight Demonstration Program

Because of anticipated near- and far-term mission needs for innovative new electric propulsion technologies, the NASA On-Board Propulsion program is sponsoring NASA Lewis Research Centers' Pulsed Plasma Thruster (PPT) technology development program to rapidly advance PPT technology. This is a joint effort of Lewis' On-Board Propulsion Branch and Space Flight Project Branch. Building on state-of-the-art technology developed and flown in the 1970's and 1980's for Department of Defense missions, newly developed PPT program designs are realizing significant gains in system mass reduction, thrust to mass ratio, total impulse to mass ratio, and variability of impulse bit.

Peterson, Todd T.↗
NASA NTRS2007

RF and Optical Communications: A Comparison of High Data Rate Returns From Deep Space in the 2020 Timeframe

As NASA proceeds with plans for increased science data return and higher data transfer capacity for science missions, both RF and optical communications are viable candidates for significantly higher-rate communications from deep space to Earth. With the inherent advantages, smaller apertures and larger bandwidths, of optical communications, it is reasonable to expect that at some point in time and combination of increasing distance and data rate, the rapidly emerging optical capabilities would become more advantageous than the more mature and evolving RF techniques. This paper presents a comparison of the burden to a spacecraft by both RF and optical communications systems for data rates of 10, 100, and 1000 Mbps and large distances. Advanced technology for RF and optical communication systems have been considered for projecting capabilities in the 2020 timeframe. For the comparisons drawn, the optical and RF ground terminals were selected to be similar in cost. The RF system selected is composed of forty-five 12-meter antennas, whereas the selected optical system is equivalent to a 10-meter optical telescope. Potential differences in availability are disregarded since the focus of this study is on spacecraft mass and power burden for high-rate mission data, under the assumption that essential communications will be provided by low-rate, high availability RF. For both the RF and optical systems, the required EIRP, for a given data rate and a given distance, was achieved by a design that realized the lowest possible communications subsystem mass (power + aperture) consistent with achieving the lowest technology risk. A key conclusion of this paper is that optical communications has great potential for high data rates and distances of 2.67 AU and beyond, but requires R&D and flight demonstrations to prove out technologies.

Williams, W. Dan↗
NASA NTRS1984

Coronal mass ejection recurrence studies indicating global activity and local suppression

The distribution of time intervals between successive coronal mass ejection events observed from the SMM and Skylab coronagraphs has been analyzed. Histograms of such recurrence times show that mass ejections tend to cluster in periods of activity. Evidence is found for simultaneous activity on a global scale. A second result is that, statistically, limb regions within + or - 59 deg position angle of a mass ejection show a marked absence of subsequent observable ejections for approximately 10 h. Flares of importance greater than or equal to 1 show no such deficit; however, large disparitons brusques tend similarly to be suppressed, for 24 h. This result, together with the closer association of mass ejection with eruptive prominences rather than with flares and the realization that eruptive prominences are rarely if ever seen without an accompanying mass ejection, obviates suggestions that magnetohydrodynamic conditions in the outflow following the earlier mass ejection hide subsequent coronal events.

Wagner, W. J.↗
DOE OSTI2025

Cold freeze out of superheavy dark matter and Hubble tension

We present a unified framework, the "X miracle", in which dark matter consists of superheavy, nonthermal X particles whose relic abundance is determined not by the conventional weak-scale, semi-relativistic ("hot") freeze-out of WIMPs, but by annihilation or decay occurring within the smallest and earliest gravitationally bound objects. Unlike thermal WIMPs, which decouple at velocities of order 0.3c with relic abundance ρ∞ set by weak-scale interactions, X particles are produced nonthermally with an initial overabun dance ρ ini >> ρ ∞ . They become nonrelativistic extremely early, redshift to ultra-cold velocities, allowing collapse into compact bound structures characterized by a novel quantum gravitational scale, r X = 4$\hbar$ 2 $/Gm^3_X$ = 10 −13 m $\hbar$$/m_Xc$, much larger than the Compton wavelength. The framework predicts a particle mass of 10 12 GeV and an enhanced cross section of 10 −21 m 3 /s. Overlapping particle wavefunctions in these compact structures drive annihilation or decay into additional radiation, leading to a "cold" freeze-out that converts most of ρ ini into radiation while leaving a relic density ρ ∞ . Solutions to the Boltzmann equation indicate that an extreme ("big") depletion, with only one particle in a billion surviving, yields an additional radiation contribution $ΔN_{eff}$ ≈ 0.4, which could help alleviate the Hubble tension. For particles of 10 12 GeV, the scenario predicts a dark coupling constant α X = 0.09 that is responsible for an instanton-induced decay process, consistent with current UHECR bounds. Early collapse at 10 −6 s may release binding energy as high-frequency (100kHz) gravitational waves or ultralight GUT-scale axions (10 −9 eV). Superheavy sterile neutrinos provide a natural particle realization, linking dark matter to neutrino mass and baryogenesis. If gravitationally produced, this framework favors high-scale inflation and effi cient reheating. The "X miracle" thus demonstrates that dark matter need not be weak-scale: gravitational dynamics can control freeze-out and evolution, producing multi-messenger observational signatures in UHECRs, axions, gravitational waves, and small-scale structures.

Xu, Zhijie Jay [Pacific Northwest National Laborat↗
NASA NTRS1989

Tidal disruption of open clusters in their parent molecular clouds

A simple model of tidal encounters has been applied to the problem of an open cluster in a clumpy molecular cloud. The parameters of the clumps are taken from the Blitz, Stark, and Long (1988) catalog of clumps in the Rosette molecular cloud. Encounters are modeled as impulsive, rectilinear collisions between Plummer spheres, but the tidal approximation is not invoked. Mass and binding energy changes during an encounter are computed by considering the velocity impulses given to individual stars in a random realization of a Plummer sphere. Mean rates of mass and binding energy loss are then computed by integrating over many encounters. Self-similar evolutionary calculations using these rates indicate that the disruption process is most sensitive to the cluster radius and relatively insensitive to cluster mass. The calculations indicate that clusters which are born in a cloud similar to the Rosette with a cluster radius greater than about 2.5 pc will not survive long enough to leave the cloud. The majority of clusters, however, have smaller radii and will survive the passage through their parent cloud.

Long, Kevin↗
NASA NTRS1989

Experimental investigation into passive damping enhancement for space structures

This work presents experiments which were conducted to verify kinetic and strain energy damping enhancement schemes for large/precision space structures. Two types of damping mechanisms were applied to a 5 meter long, 10 bay aluminum box truss with a quasi free-free three-dimensional suspension. Tuneable proof mass dampers (PMDs) were implemented with space realizable linear electromechanical drivers. Tuneable piezoelectric truss members were designed and constructed for the demonstration of resonant shunted piezoelectric damping concepts. The truss damping was measured and compared to analytical predictions obtained from a frequency domain system modeling technique. The proof mass damper implementation was found to increase first mode damping from 0.6 percent of critical to 6.4 percent of critical with a system mass increase of 2.7 percent. The resonant shunted piezoelectrics increased first mode damping to 6.0 percent with a similar mass penalty.

Hagood, Nesbitt W.↗
NASA NTRS1977

Magnetic bearing momentum wheels with magnetic gimballing capability for 3-axis active attitude control and energy storage

Magnetic bearings used for the suspension of momentum wheels provide conclusive advantages: the low friction torques and the absence of abrasion allow the realization of lightweight high speed wheels with high angular momentum and energy storage capacity and virtually unlimited lifetime. The use of actively controlled bearings provides a magnetic gimballing capability by applying the external signals to the two servo loops controlling the rotational degrees of freedom. Thus, an attitude control system can be realized by using only one rotating mass for 3-axis active satellite stabilization.

Sindlinger, R. S.↗
NASA NTRS1980

Effects of boundary-layer treatment on cryogenic wind-tunnel controls

Various techniques of realizing the desired boundary layer wall mass removal are considered in order to obtain the desired flow field over the model for various airfoils. The complementary problem of overall thermodynamic equilibrium maintenance created by the side wall boundary layer bleed is also addressed.

Balakrishna, S.↗
NASA NTRS1981

Severe storms requirements for precipitation information

Moisture can play an important if not dominant role in supplying energy to tropical and extra-tropical weather systems. In the tropics where the air is almost saturated only the slightest amount of uplift is required to initiate the release of vast amounts of latent heat to fuel systems as diverse as convective cloud clusters and hurricanes. The role of latent heating on extra-tropical systems is much more subtle. While the primary energy source for synoptic-scale systems is often the release of gravitational potential energy through the sinking of cold air and the rising of warm, it seems that the latent heat that is eventually realized through slow uplift of large masses of air can significantly modify the evolution of the system. An analysis of the energetics of the storm of March 25 to 27, 1978 over the eastern USA to understand the implications of the heat released due to the vast cloudy area associated with warm frontal overrunning was performed.

Adler, R. F.↗
NASA NTRS1991

Experimental investigation of helicopter vibration reduction using rotor blade aeroelastic tailoring

A wind tunnel investigation has been conducted to parametrically investigate the effect of blade nonstructural mass on helicopter fixed- and rotating-system vibratory loads. The data were obtained using Mach- and aeroelastically-scaled model rotor blades which allowed for the addition of concentrated nonstructural masses at multiple points along the blade radius. Testing was conducted for advance ratios ranging from 0.10 to 0.35 for ten blade mass configurations. Three thrust levels were obtained at representative full-scale shaft angles for each configuration. Results indicate that proper placement of blade nonstructural mass can provide reductions in fixed-system vibratory loads, but that correct mass placement and the loads reduction realized are dependent upon flight condition. The data base obtained with this investigation provides a comprehensive set of fixed-system shears and moments, blade moment, and blade flap and lag response. The data set is well suited for use in the correlation and development of advanced rotorcraft analyses.

Wilbur, Matthew L.↗
NASA NTRS2008

Advanced Imaging for Space Science

Future NASA interferometric missions will realize high-resolution with less mass and volume compared to filled-apertures thus saving in cost over comparable filled-aperture systems. However, interferometeric aperture systems give reduced sensitivity requiring longer integration times to achieve a desired signal-to-noise ratio but is likely the only cost effective path forward for high-resolution space imaging.

Lyon, Richard G.↗