SEARCH · Engineering Papers

Results for “eccentricity space”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

NASA NTRS1987

Three-step labyrinth seal for high-performance turbomachines

A three-step labyrinth seal with 12, 11, and 10 labyrinth teeth per step, respectively, was tested under static (nonrotating) conditions. The configuration represented the seal for a high-performance turbopump (e.g., the space shuttle main engine fuel pump). The test data included critical mass flux and pressure profiles over a wide range of fluid conditions at concentric, partially eccentric, and fully eccentric seal positions. The seal mass fluxes (leakage rates) were lower over the entire range of fluid conditions tested than those for data collected for similar straight and three-step cylindrical seals, and this conformed somewhat to expectations. However, the pressure profiles for the eccentric positions indicated little, if any, direct stiffness for this configuration in contrast to significant direct stiffness reported for the straight and three-step cylindrical seals over the range of test conditions. Seal dynamics depend on geometric configuration, inlet and exit parameters, fluid phase, and rotation. The method of corresponding states was applied to the mass flux data, which were found to have a pressure dependency for helium.

Hendricks, Robert C.↗

NASA NTRS1983

Transformations of the perturbed two-body problem to unperturbed harmonic oscillators

Singular, nonlinear, and Liapunov unstable equations are made regular and linear through transformations that change the perturbed planar problem of two bodies into unperturbed and undamped harmonic oscillators with constant coefficients, so that the stable solution may be immediately written in terms of the new variables. The use of arbitrary and special functions for the transformations allows the systematic discussion of previously introduced and novel anomalies. For the case of the unperturbed two-body problem, it is proved that if transformations are power functions of the radial variable, only the eccentric and the true anomalies (with the corresponding transformations of the radial variable) will result in harmonic oscillators. The present method significantly reduces computation requirements in autonomous space operations.

Szebehely, V.↗

NASA NTRS1985

Rotordynamic coefficients for compressible flow in tapered annular seals

Derivation of the governing equations for compressible flow in a tapered annular seal is based on Hirs' turbulent bulk-flow model. Zeroth and first-order perturbation equations are developed by an expansion in the eccentricity ratio. These equations are numerically integrated to obtain the leakage, and the direct and cross-coupled stiffness and damping coefficients. Seal parameters similar to the Space Shuttle Main Engine High Pressure Oxidizer Turbopump are used to demonstrate output from the analysis procedure. The effects of preswirl and seal taper are shown for three different length-to-diameter ratios. Generally the results indicate that prerotating the fluid significantly increases the cross-coupled stiffness but has little effect on the other coefficients, and increasing the convergent taper increases the direct stiffness while decreasing the direct damping and cross-coupled stiffness.

Nelson, C. C.↗

NASA NTRS1987

Urey Prize Lecture - Chaotic dynamics in the solar system

Attention is given to solar system cases in which chaotic solutions of Newton's equations are important, as in chaotic rotation and orbital evolution. Hyperion is noted to be tumbling chaotically; chaotic orbital evolution is suggested to be of fundamental importance to an accounting for the Kirkwood gaps in asteroid distribution and for the phase space boundary of the chaotic zone at the 3/1 mean-motion commensurability with Jupiter. In addition, chaotic trajectories in the 2/1 chaotic zone reach very high eccentricities by a route that carries them to high inclinations temporarily.

Wisdom, Jack↗

NASA NTRS2013

STIS Coronagraphic Imaging of Fomalhaut: Main Belt Structure and the Orbit of Fomalhaut b

We present new optical coronagraphic data of Fomalhaut obtained with HST/STIS in 2010 and 2012. Fomalhaut b is recovered at both epochs to high significance. The observations include the discoveries of tenuous nebulosity beyond the main dust belt detected to at least 209AU projected radius, and a approx. 50AU wide azimuthal gap in the belt northward of Fomalhaut b. The two epochs of Space Telescope Imaging Spectrograph (STIS) photometry exclude optical variability greater than 35%. A Markov chain Monte Carlo analysis demonstrates that the orbit of Fomalhaut b is highly eccentric, with e = 0.8 +/- 0.1, a = 177 +/- 68AU, and q = 32 +/- 24AU. Fomalhaut b is apsidally aligned with the belt and 90% of allowed orbits have mutual inclination <=36 deg. Fomalhaut b's orbit is belt crossing in the sky plane projection, but only 12% of possible orbits have ascending or descending nodes within a 25AU wide belt annulus. The high eccentricity invokes a dynamical history where Fomalhaut b may have experienced a significant dynamical interaction with a hypothetical planet Fomalhaut c, and the current orbital configuration may be relatively short-lived. The Tisserand parameter with respect to a hypothetical Fomalhaut planet at 30AU or 120AU lies in the range 2-3, similar to highly eccentric dwarf planets in our solar system. We argue that Fomalhaut b's minimum mass is that of a dwarf planet in order for a circumplanetary satellite system to remain bound to a sufficient radius from the planet to be consistent with the dust scattered light hypothesis. In the coplanar case, Fomalhaut b will collide with the main belt around 2032, and the subsequent emergent phenomena may help determine its physical nature.

Tisserand parameter↗

NASA NTRS2019

The mass and density of the dwarf planet (225088) 2007 OR10

The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e ≈ 0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused by the Kozai mechanism. Dynamical considerations also suggest that the moon is small, D(eff) < 100 km. Based on the newly determined system mass of 1.75 ·10^21 kg, 2007 OR10 is the fifth most massive dwarf planet after Eris, Pluto, Haumea and Makemake. The newly determined orbit has also been considered as an additional option in our radiometric analysis, provided that the moon orbits in the equatorial plane of the primary. Assuming a spherical shape for the primary this approach provides a size of 1230 ± 50 km, with a slight dependence on the satellite orbit orientation and primary rotation rate chosen, and a bulk density of 1.75 ± 0.07 g/cu.cm for the primary. A previous size estimate that assumed an equator-on configuration (1535(−225,+75) km) would provide a density of 0.92(−0.14,+0.46) g/cu.cm, unexpectedly low for a 1000 km-sized dwarf planet.

Csaba Kiss↗

NASA NTRS1992

Intramuscular pressure: A better tool than EMG to optimize exercise for long-duration space flight

A serious problem experienced by astronauts during long-duration space flight is muscle atrophy. In order to develop countermeasures for this problem, a simple method for monitoring in vivo function of specific muscles is needed. Previous studies document that both intramuscular pressure (IMP) and electromyography (EMG) provide quantitative indices of muscle contraction force during isometric exercise. However, at present there are no data available concerning the usefulness of IMP versus EMG during dynamic exercise. Methods: IMP (Myopress catheter) and surface EMG activity were measured continuously and simultaneously in the tibalis anterior (TA) and soleus (SOL) muscles of 9 normal male volunteers (28-54 years). These parameters were recorded during both concentric and eccentric exercises which consisted of plantarflexon and dorsiflexon of the ankle joint. A Lido Active Isokinetic Dynamometer concurrently recorded ankle joint torque and position. Results: Intramuscular pressure correlated linearly with contraction force for both SOL (r exp 2 = 0.037) and TA (R exp 2 = 0.716 and r exp 2 = 0.802, respectively). During eccentric exercises, SOL and TA IMP also correlated linearly with contraction force (r(exp 2) = 0.883 and r(exp 2) = 0.904 respectively), but SOL and TA EMG correlated poorly with force (r(exp 2) = 0.489 and r(exp 2) = 0.702 respectively). Conclusion: IMP measurement provides a better index of muscle contraction force than EMG during concentric and eccentric exercise. IMP reflects intrinsic mechanical properties of individual muscles, such as length tension relationships. Although invasive, IMP provides a more powerful tool and EMG for developing exercise hardware and protocols for astronauts exposed to long-duration space flight.

Hargens, A. R.↗

NASA NTRS1973

Diffraction studies applicable to 60-foot microwave research facilities

The principal features of this document are the analysis of a large dual-reflector antenna system by vector Kirchhoff theory, the evaluation of subreflector aperture-blocking, determination of the diffraction and blockage effects of a subreflector mounting structure, and an estimate of strut-blockage effects. Most of the computations are for a frequency of 15.3 GHz, and were carried out using the IBM 360/91 and 360/95 systems at Goddard Space Flight Center. The FORTRAN 4 computer program used to perform the computations is of a general and modular type so that various system parameters such as frequency, eccentricity, diameter, focal-length, etc. can be varied at will. The parameters of the 60-foot NRL Ku-band installation at Waldorf, Maryland, were entered into the program for purposes of this report. Similar calculations could be performed for the NELC installation at La Posta, California, the NASA Wallops Station facility in Virginia, and other antenna systems, by a simple change in IBM control cards. A comparison is made between secondary radiation patterns of the NRL antenna measured by DOD Satellite and those obtained by analytical/numerical methods at a frequency of 7.3 GHz.

Schmidt, R. F.↗

NASA NTRS2001

Evaluation of Relative Navigation Algorithms for Formation-Flying Satellites

Goddard Space Flight Center is currently developing advanced spacecraft systems to provide autonomous navigation and control of formation flyers. This paper discusses autonomous relative navigation performance for formations in eccentric, medium, and high-altitude Earth orbits using Global Positioning System (GPS) Standard Positioning Service (SPS) and intersatellite range measurements. The performance of several candidate relative navigation approaches is evaluated. These analyses indicate that the relative navigation accuracy is primarily a function of the frequency of acquisition and tracking of the GPS signals. A relative navigation position accuracy of 0.5 meters root-mean-square (RMS) can be achieved for formations in medium-attitude eccentric orbits that can continuously track at least one GPS signal. A relative navigation position accuracy of better than 75 meters RMS can be achieved for formations in high-altitude eccentric orbits that have sparse tracking of the GPS signals. The addition of round-trip intersatellite range measurements can significantly improve relative navigation accuracy for formations with sparse tracking of the GPS signals.

Kelbel, David↗

NASA NTRS2016

In-Space Production of Storable Propellants

Our exploration of the feasibility of in-space production of storable propellants from resourcesavailable on asteroids, and also on Mars and the Moon, has considered the process of sampleacquisition; the energy requirements for heating and volatile release; the thermodynamic behaviorof gas release from minerals and organic polymers containing hydrogen, oxygen, carbon, sulfur,and nitrogen; purification of the released water and carbon dioxide; the storage and transportation of these materials in the condensed state; synthesis of fuels including methanol and dimethyl ether(DME); and the co-production, concentration, stability, and storage of the complementary oxidizer high-test hydrogen peroxide (HTP). We call attention to the ability of the storable propellant/oxidizer combination of DME and HTP to carry out deep-space missions and to perform retrieval and relocation of any and all space-derived resources, such as retrieving asteroidal metal to high Earth orbit. This study's analyses are based on returning resources to a storage/processing/dispensing facility in a Highly Eccentric Earth Orbit (HEEO) with a perigee above geosynchronous orbit and an apogee approach or beyond the Moon's orbit.The methane/LOX option, notable for good engine performance, has not been included in this study because our scope includes only fully storable propellants.

Lewis, John S.↗

NASA NTRS2010

Triaxial Swirl Injector Element for Liquid-Fueled Engines

A triaxial injector is a single bi-propellant injection element located at the center of the injector body. The injector element consists of three nested, hydraulic swirl injectors. A small portion of the total fuel is injected through the central hydraulic injector, all of the oxidizer is injected through the middle concentric hydraulic swirl injector, and the balance of the fuel is injected through an outer concentric injection system. The configuration has been shown to provide good flame stabilization and the desired fuel-rich wall boundary condition. The injector design is well suited for preburner applications. Preburner injectors operate at extreme oxygen-to-fuel mass ratios, either very rich or very lean. The goal of a preburner is to create a uniform drive gas for the turbomachinery, while carefully controlling the temperature so as not to stress or damage turbine blades. The triaxial injector concept permits the lean propellant to be sandwiched between two layers of the rich propellant, while the hydraulic atomization characteristics of the swirl injectors promote interpropellant mixing and, ultimately, good combustion efficiency. This innovation is suited to a wide range of liquid oxidizer and liquid fuels, including hydrogen, methane, and kerosene. Prototype testing with the triaxial swirl injector demonstrated excellent injector and combustion chamber thermal compatibility and good combustion performance, both at levels far superior to a pintle injector. Initial testing with the prototype injector demonstrated over 96-percent combustion efficiency. The design showed excellent high -frequency combustion stability characteristics with oxygen and kerosene propellants. Unlike the more conventional pintle injector, there is not a large bluff body that must be cooled. The absence of a protruding center body enhances the thermal durability of the triaxial swirl injector. The hydraulic atomization characteristics of the innovation allow the design to be rapidly scaled from small in-space applications [500-5,000 lbf (2.2 22.2 kN)] to large thrust engine applications [80,000 lbf (356 kN) and beyond]. The triaxial injector is also less sensitive to eccentricities, manufacturing tolerances, and gap width of many traditional coaxial and pintle injector designs. The triaxial-injector injection orifice configuration provides for high injection stiffness. The low parts count and relatively large injector design features are amenable to low-cost production.

Muss, Jeff↗

NASA NTRS2017

Novel Musculoskeletal Loading and Assessment System

Ground based and ISS (International Space Station) exercise research have shown that axial loading via two-point loading at the shoulders and load quality (i.e. consistent load and at least 1:1 concentric to eccentric ratio) are extremely important to optimize musculoskeletal adaptations to resistance exercise. The Advanced Resistance Exercise Device (ARED) is on ISS now and is the "state of the art" for resistance exercise capabilities in microgravity; however, the ARED is far too large and power consuming for exploration vehicles. The single cable exercise device design selected for MPCV (Multi-Purpose Crew Vehicle), does not readily allow for the two-point loading at the shoulders.

Downs, Meghan E.↗

DOE OSTI2024

Dynamical instability in multi-orbiter systems with gas friction

ABSTRACT Closely packed multiplanet systems are known to experience dynamical instability if the spacings between the planets are too small. Such instability can be tempered by the frictional forces acting on the planets from gaseous discs. A similar situation applies to stellar-mass black holes embedded in active galactic nuclei discs around supermassive black holes. We use N-body integrations to evaluate how the frictional damping of orbital eccentricity affects the growth of dynamical instability for a wide range of K (the difference in the planetary semimajor axes in units of the mutual Hill radius) and (unequal) planet masses. We find that, in general, the stable region (large K) and unstable region (small K) are separated by a “grey zone”, where the (in)stability is not guaranteed. We report the numerical values of the critical spacing for stability Kcrit and the “grey zone” range in different systems, and provide fitting formulae for arbitrary frictional forcing strength. We show that the stability of a system depends on the damping time-scale τ relative to the zero-friction instability growth time-scale tinst: two-planet systems are stable if tinst ≳ τ; three-planet systems require tinst ≳ 10τ−100τ. When K is sufficiently small, tinst can be less than the synodic period between the planets, which makes frictional stabilization unlikely to occur. As K increases, tinst tends to grow exponentially, but can also fluctuate by a few orders of magnitude. We also devise a linear map to analyse the dynamical instability of the “planet + test mass” system, and find qualitative agreement with N-body simulations.

Li, Jiaru (ORCID:0000000155507421)↗

NASA NTRS1986

Oil-Free Compressor

Compressor pistons moved by eccentric shaft need no lubricants. Compressor has shaft, middle section is eccentric in relation to end sections. Driven by brushless dc motor, shaft turns inner races of set of four cam bearings. Outer cam-bearing races in turn actuate four pistons spaced equally apart, around and along shaft. Each outer bearing race held in position by pressure exerted on it by piston. Because no frictional motion between piston and outer bearing race, lubricant between them unnecessary. Cam bearings themselves contain potted internal lubricant. Originally proposed for use in space, new compressor for refrigerators or freezers does not depend on pool of oil for lubricating its pistons. Operated in any orientation.

Fitzjerrell, D. G.↗

NASA NTRS1993

Increased technetium uptake is not equivalent to muscle necrosis: scintigraphic, morphological and intramuscular pressure analyses of sore muscles after exercise

A scintigraphic technique employing technetium pyrophosphate uptake was used to identify the area of skeletal muscle damage in the lower leg of four runners 24 h after an ultramarathon footrace (160 km). Most of the race had been run downhill which incorporated an extensive amount of eccentric work. Soreness was diffuse throughout the posterior region of the lower leg. In order to interpret what increased technetium uptake reflects and to express extreme endurance related damages, a biopsy was taken from the 3-D position of abnormal uptake. In addition, intramuscular pressures were determined in the deep posterior compartment. Scintigraphs revealed increased technetium pyrophosphate uptake in the medial portion of the gastrocnemius muscle. For 3698 fibres analysed, 33 fibres (1%) were necrotic, while a few other fibres were either atrophic or irregular shaped. A cluster of necrotic fibres occurred at the fascicular periphery for one subject and fibre type grouping occurred for another. Ultrastructural analysis revealed Z-line streaming near many capillaries and variously altered subsarcolemmal mitochondria including some with paracrystalline inclusions. The majority of the capillaries included thickened and irregular shaped endothelial cells. Intramuscular pressures of the deep posterior compartment were slightly elevated (12-15 mmHg) for three of the four subjects. Increased technetium uptake following extreme endurance running does not just reflect muscle necrosis but also subtle fibre abnormalities. Collectively, these pathological findings are attributed to relative ischaemia occurring during the race and during pre-race training, whereas, intramuscular pressure elevations associated with muscle soreness are attributed to mechanical stress caused by extensive eccentric work during the race.

NASA Program Space Physiology and Countermeasures↗

NASA NTRS1983

Flight path design issues for the TOPEX mission

The proposed Ocean Topography Experiment (TOPEX) is an earth satellite mission currently under consideration by NASA. The primary purpose of the experiment is to determine the general circulation of the oceans and its variability. High precision, space based altimeter measurements will be combined with surface measurements and ocean models to accomplish the mission objectives. The paper will discuss mission requirements on orbit design, orbit selection space, derived requirements on navigation and satellite design issues which impact orbit selection. Unique aspects of the TOPEX orbit design are highlighted, such as high precision repeating orbits, 'frozen orbit' values of eccentricity and periapses, precise maneuver and orbit determination requirements and insuring crossing arcs over a calibration-site.

Frautnick, J. C.↗

NASA NTRS1999

Quantifying Biomechanical Characteristics of Jumping Exercises in 1G and in Simulated and True Microgravity

Exercise in microgravity is one of the most promising countermeasures to the dual problems of space flight-induced bone loss and muscle atrophy. Although exercise in microgravity has been studied extensively from a metabolic standpoint, little research has focused on the efficacy of different forms of exercise for maintaining musculoskeletal integrity. Exercise protocols have not been effective in preventing muscle atrophy and bone loss during space flight, especially in the lower extremities. In 1-G, however, animal experiments have clearly indicated that: (1) certain bone strains and strain rates do stimulate bone deposition, and (2) repetitive loading of the lower extremity can increase osteonal bone formation even as proximally as the vertebral column. Such studies have also indicated that a relatively small number of appropriate loading cycles may lead to bone deposition. This suggests that an optimal exercise regimen might be able to maintain bone and muscle integrity during space flight. Since there is evidence that the bones and muscles of the lower limbs are particularly affected by space flight, the present study addressed two major aims: (1) quantify externally applied impact loads and rates of loading under the feet during tethered jumping exercises, and (2) determine the amount of eccentric and concentric whole-muscle activity during these jumping exercises in true and in simulated zero-gravity.

Davis, B. L.↗

NASA NTRS1985

Report of the Transportation Panel

Tether applications for space transportation are covered: (1) payload boast; (2) upper stage boost; (3) E.T. deboost; (4) shuttle deboost; (5) shuttle docking ; (6) payload and OTV boost; (7) OTV payload boost; (8) lunar assist and eccentricity change; (9) aeromaneuvering by remote sail or kite; (10) electrodynamic deceleration; and (11) lunar and planetary applications. The first seven transfer momentum between two masses at the tether tips, and the remaining for use tethers for controlled interaction with the environment.

Vallerani, E.↗