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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Hydrodynamic instability and coalescence of binary neutron stars

We study the importance of hydrodynamic effects on the evolution of coalescing binary neutron stars. Using an approximate energy functional constructed from equilibrium solutions for polytropic binary configuration, we incorporate hydrodynamic effects into the calculation of the orbital decay driven by gravitational wave emission. In particular, we follow the transition between the quasi-static, secular decay of the orbit at large separation and the rapid dynamical evolution of confirgurations approaching contact. We show that a purely Newtonian hydrodynamic instability can significantly accelerate the coalescence at small separation. Such an instability occurs in all close binary configurations containing sufficiently incompressible stars. Calculations are performed for various neutron star masses, radii, and spins. The influence of the stiffness of the equation of state is also explored by varying the effective polytopic index. Typically, we find that the radial infall velocity just prior to contact is about 10% of the tangential orbital velocity. Once the stability limit is reached, the final evolution only takes another orbit. Post-Newtonian effects can move the stability limit to a larger binary separation, and may induce an even larger radial velocity. We also consider the possibiltiy of mass transfer form one neutron star to the other. We show that stable mass transfer is unlikely except when the mass of one of the components is very small (M is less than or approximately 0.4 solar mass) and the viscosity is high enough to maintain corotation. Otherwise, either the two stars come into contact or the dynamical instability sets in before a Roche limit can be reached.

Lai, Dong↗
NASA NTRS1972

Launch window analysis in a new perspective with examples of departures from Earth to Mars

Earth-departure windows are investigated for two round trip stopover missions to Mars. These are the 1981 inbound Venus swingby mission and the 1986 direct minimum-energy mission. The secular effects of planetary oblateness are used to predict the motion of the parking orbit. A procedure is developed for matching the motion of the parking orbit and the escape asymptote. Earth-departure velocity penalties, caused by orbital plane misalinement, are reduced by synchronizing the motion of the parking orbit and the escape trajectory.

Thibodeau, J. R., III↗
NASA NTRS2022

Eta Carinae: An Evolving View of the Central Binary, Its Interacting Winds and Its Foreground Ejecta

FUV spectra of η Car, recorded across two decades with HST/STIS, document multiple changes in resonant lines caused by dissipating extinction in our line of sight. The FUV flux has increased nearly tenfold, which has led to increased ionization of the multiple shells within the Homunculus and photodestruction of H 2 . Comparison of observed resonant line profiles with CMFGEN model profiles allows separation of wind–wind collision and shell absorptions from the primary wind P Cygni profiles. The dissipating occulter preferentially obscured the central binary and interacting winds relative to the very extended primary wind. We are now able to monitor changes in the colliding winds with orbital phase. High-velocity transient absorptions occurred across the most recent periastron passage, indicating acceleration of the primary wind by the secondary wind, which leads to a downstream, high-velocity bow shock that is newly generated every orbital period. There is no evidence of changes in the properties of the binary winds.

Massive stars↗
NASA NTRS1988

Design of a Ram Accelerator mass launch system

The Ram Accelerator, a chemically propelled, impulsive mass launch system, is presented as a viable concept for directly launching acceleration-insensitive payloads into low Earth orbit. The principles of propulsion are based on those of an airbreathing supersonic ramjet. The payload vehicle acts as the ramjet centerbody and travels through a fixed launch tube that acts as the ramjet outer cowling. The launch tube is filled with premixed gaseous fuel and oxidizer mixtures that combust at the base of the vehicle and produce thrust. Two modes of in-tube propulsion involving ramjet cycles are used in sequence to accelerate the vehicle from 0.7 km/sec to 9 km/sec. Requirements for placing a 2000 kg vehicle into a 500-km circular orbit, with a minimum amount of onboard rocket propellant for orbital maneuvers, are examined. It is shown that in-tube propulsion requirements dictate a launch tube length of 5.1 km to achieve an exit velocity of 9 km/sec, with peak accelerations not to exceed 1000 g's. Aerodynamic heating due to atmospheric transit requires minimal ablative protection and the vehicle retains a large percentage of its exit velocity. An indirect orbital insertion maneuver with aerobraking and two apogee burns is examined to minimize the required onboard propellant mass. An appropriate onboard propulsion system design to perform the required orbital maneuvers with minimum mass requirements is also determined. The structural designs of both the launch tube and the payload vehicle are examined using simple structural and finite element analysis for various materials.

Source record↗
NASA NTRS2015

Internship Abstract - Aerosciences and Flight Mechanics Intern

Mars is a hard place to land on, but my internship with NASA's Aerosciences & Flight Mechanics branch has shown me the ways in which men and women will one day land safely. I work on Mars Aerocapture, an aeroassist maneuver that reduces the fuel necessary to "capture" into Martian orbit before a descent. The spacecraft flies through the Martian atmosphere to lose energy through heating before it exits back into space, this time at a slower velocity and in orbit around Mars. Spacecraft will need to maneuver through the Martian atmosphere to accurately hit their orbit, and they will need to survive the generated heat. Engineering teams need simulation data to continue their designs, and the guidance algorithm that ensures a proper orbit insertion needs to be refined - two jobs that fell to me at the summer's start. Engineers within my branch have developed two concept aerocapture vehicles, and I run simulations on their behavior during the maneuver. I also test and refine the guidance algorithm. I spent the first few weeks familiarizing myself with the simulation software, troubleshooting various guidance bugs and writing code. Everything runs smoothly now, and I recently sent my first set of trajectory data to a Thermal Protection System group so they can incorporate it into their heat-bearing material designs. I hope to generate plenty of data in the next few weeks for various engineering groups before my internship ends mid-August. My major accomplishment so far is improving the guidance algorithm. It is a relatively new algorithm that promises higher accuracy and fuel efficiency, but it hasn't undergone extensive testing yet. I've had the opportunity to work with the principal developer - a professor at Iowa State University - to find and fix several issues. I was also assigned the task of expanding the branch's aerodynamic heating simulation software. I am excited to do this because engineers in the future will use my work to generate meaningful data and make design decisions. My internship has taught me to how to teach myself. There are no tutors, study sessions or professor office hours. When I am given an assignment I am expected to figure out how to accomplish it, and I have grown in my problem solving abilities. My summer experience has reinforced my drive to work at NASA, and I can definitely see myself working full time on the aerocapture project, or something similar.

Rangel, John↗
NASA NTRS1977

Mercury's core - The effect of obliquity on the spin-orbit constraints

Constraints were previously placed on various properties of a Mercurian liquid core for compatibility with Mercury's escape from the stable spin-orbit resonance with the spin angular velocity equal to twice the orbital mean motion (the 2n resonance), under the assumption that the planet's obliquity was nearly zero at the time of resonance passage. Capture probabilities at arbitrary nonzero obliquities for the 2n resonance are determined for the cases where the core is strongly or weakly coupled to the mantle. It is found that the capture probabilities are reduced to below unity for all core-fluid viscosities in the weak-coupling limit, but are almost unchanged in the strong-coupling limit. The reduction in capture probability is attributed to reduction of the mantle's spin angular velocity by the core-mantle interaction, which would also reduce the obliquity to negligibly small values before the 2n resonance was even reached. It is concluded that the constraints on the core may still be maintained since Mercury most likely passed through the 2n resonance with nearly zero obliquity.

Peale, S. J.↗
NASA NTRS2008

Extrasolar Planetary Imaging Coronagraph: Visible Nulling Coronagraph Testbed Results

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime ( 5 year goal) and will revisit planets at least three times at intervals of 9 months. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed,

Lyon, Richard G.↗
NASA NTRS2009

Visible Nulling Coronagraph Testbed Results

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept study and a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC would provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 5-year mission lifetime. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables starlight suppression in broadband light from 480-960 nm. To demonstrate the VNC approach and advance it's technology readiness we have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

Lyon, Richard G.↗
NASA NTRS1975

Orbiter entry trajectory corridors: 32000 pound payload, 67.5 percent center of gravity

Thermal and equilibrium glide boundaries were used to analyze and/or design shuttle orbiter entry trajectories. Plots are presented of orbiter thermal and equilibrium glide boundaries in the drag/mass-relative velocity dynamic pressure-relative velocity, and altitude-relative velocity planes for an orbiter having a 32,000 pound payload and a 67.5% center of gravity location. These boundaries were defined for control points 1 through 4 of the shuttle orbiter for 40 deg-30 deg and 38 deg-28 deg ramped angle of attack entry profiles and 40 deg, 38 deg, 35 deg, 30 deg, 28 deg, and 25 deg constant angle of attack entry profiles each at 20 deg, 15 deg, and 10 deg constant body flap settings.

Treybig, J. H.↗
NASA NTRS1991

Foil perforation particulate impact records on LDEF MAP AO023: Incident mass distributions

An array of multiple foils varying from 1.5 to 3.0 microns exposed on Long Duration Exposure Facility's (LEDF's) geocentrically stabilized exposure platform provides perforation distributions which relate to particulate flux mass distributions and impact velocity in LDEF's orbital reference frame. The application of physical modeling enables a preliminary separation into orbital and interplanetary components, both of which have differing velocities and hence penetration effectiveness. Thin foil hypervelocity calibration data and parametric penetration formulae developed to relate target hole diameter to projectile dimensions are critically examined and a new formula offered for the ballistic limit situation. Incorporating projectile density, target density, and target strength and dimensional scaling from submicron particulates to centimeter scale data, it contrast very significantly with previous formulae in the interpretation of space impact data. Perforation flux distributions for the leading, trailing, and space pointing faces and associated mass distributions for the two populations are presented.

Mcdonnell, J. A. M.↗
NASA NTRS1979

Substorm warnings - An ISEE-3 real time data system

The use of solar wind measurements made by ISEE-3 in its halo orbit around the L1 libration point to predict the onsets of magnetospheric substorms and geomagnetic storms is discussed. Consideration is given to the limitations on the predictive ability of the satellite measurements set by the bulk solar wind velocity, the elliptical orbit of the satellite and the correlation lengths of the magnetic field and the solar wind plasma. The ISEE-3 real-time data system is presented, with attention given to the ground receiving stations, the NASCOM communications system, the Multisatellite Operations Control Center and Information Processing Division at the Goddard Space Flight Center, the link between Goddard and the NOAA Space Environmental Services Center, and the NOAA Space Environment Laboratory data acquisition and display data system, which includes displays allowing storm forecasts. It is noted that the entire system should be operational by March, 1980.

Tsurutani, B.↗
NASA NTRS2011

Preliminary Results on the Gravitational Slingshot Effect and the Population of Hyperbolic Meteoroids at Earth

Interstellar meteoroids, solid particles arriving from outside our Solar System, are not easily distinguished from local meteoroids. A velocity above the escape velocity of the Sun is often used as an indicator of a possible interstellar origin. We demonstrate that the gravitational slingshot effect, resulting from the passage of local meteoroid near a planet, can produce hyperbolic meteoroids at the Earth s orbit with excess velocities comparable to those expected of interstellar meteoroids.

Wiegert, P. A.↗
NASA NTRS1981

Introduction to orbital flight planning (1)

This workbook is designed for students interested in space flight planning, who after training, may serve as flight planning aides. Routine flight planning activities requiring engineering-type calculations and analysis are covered. Practice exercises and brief instructions are given for the programming and use of the hand calculator as well as the calculation of position and velocity in the orbital plane. Calculation of relative orbital position is also covered with emphasis upon celestial coordinates and time measurement.

Blackwell, H. E.↗
NASA NTRS2022

The Warm Neptune GJ 3470b Has a Polar Orbit

The warm Neptune GJ 3470b transits a nearby (d = 29 pc) bright slowly rotating M1.5-dwarf star. Using spectroscopic observations during two transits with the newly commissioned NEID spectrometer on the WIYN 3.5 m Telescope at Kitt Peak Observatory, we model the classical Rossiter–McLaughlin effect, yielding a sky-projected obliquity of λ=98 +15 −12 ˚and a v sin i = 0.85 +0.27 −0.33 kms -1 . Leveraging information about the rotation period and size of the host star, our analysis yields a true obliquity of ψ=95 +9 −8 ◦ , revealing that GJ 3470b is on a polar orbit. Using radial velocities from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that the data are compatible with a long-term radial velocity (RV) slope of 𝛾̀=-0.0022±0.0011 ms -1 day -1 over a baseline of 12.9 yr. If the RV slope is due to acceleration from another companion in the system, we show that such a companion is capable of explaining the polar and mildly eccentric orbit of GJ 3470b using two different secular excitation models. The existence of an outer companion can be further constrained with additional RV observations, Gaia astrometry, and future high-contrast imaging observations. Lastly, we show that tidal heating from GJ 3470b’s mild eccentricity has most likely inflated the radius of GJ 3470b by a factor of ∼1.5–1.7, which could help account for its evaporating atmosphere.

Exoplanet astronomy↗
NASA NTRS1993

Collisions and close encounters between massive main-sequence stars

Smooth-particle hydrodynamics is used to investigate collisions and close encounters between two massive main-sequence stars. Approximate scaling relations and fitting formulas are given for the amount of mass loss and for the critical impact parameters for capture or merging. The more massive stars, which have smaller ratios of specific binding energy to the square of escape velocity, are more easily disrupted in collisions. As the relative velocity increases, the orbital energy of the colliding stars can only be dissipated by shock heating, and the critical capture radius decreases much faster than predicted by linear theory. The average fractional mass loss per collision in a cluster is found not to depend sensitively on the stellar velocity dispersion.

Lai, Dong↗
NASA NTRS1972

The effects of trajectory characteristics on scientific objectives for major planetary orbiters.

Outline of specific solutions in the areas of attitude control, interplanetary trajectory parameters, and orbital configurations of major planetary spacecraft. It is shown that inertia wheel supplementation to a three-axis, stabilized attitude control system will substantially reduce propellant weight and attitude jet firings, especially when considering three-year orbital lifetimes as well as interplanetary trip times of several years. Eight interplanetary trajectory parameters including the earth injection energy and the declination of the launch asymptote are shown for a 1980 earth launch mission to Jupiter. The effects of the interplanetary trajectory parameters on the deboost velocities and resulting orbits about Jupiter are summarized. Orbital mode and science interfaces are defined, and a celestial mechanics experiment independent of earth tracking is briefly outlined.

Paul, C. K.↗
NASA NTRS1989

In-space technology development: Atomic oxygen and orbital debris effects

Earlier Shuttle flight experiments have shown atomic oxygen within the orbital environment can interact with many materials to produce surface recession and mass loss and combine catalytically with other constituents to generate visible and infrared glows. In addition to these effects, examinations of returned satellite hardware have shown many spacecraft materials are also susceptible to damage from high velocity impacts with orbital space debris. These effects are of particular concern for large, multi-mission spacecraft, such as Space Station and SDI operational satellites, that will operate in low-Earth orbit (LEO) during the late 1990's. Not only must these spacecraft include materials and exterior coatings that are resistant to atomic oxygen surface interactions, but these materials must also provide adequate protection against erosion and pitting that could result from numerous impacts with small particles (less than 100 microns) of orbital space debris. An overview of these concerns is presented, and activities now underway to develop materials and coatings are outlined that will provide adequate atomic protection for future spacecraft. The report also discusses atomic oxygen and orbital debris flight experiments now under development to expand our limited data base, correlate ground-based measurments with flight results, and develop an orbital debris collision warning system for use by future spacecraft.

Visentine, James T.↗