Search NASA⌕ Search

SEARCH · Search NASA

Results for “INCLINATION”

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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Secondary instabilities in compressible boundary layers

Secondary instabilities are examined in compressible boundary layers at Mach numbers M(sub infinity) = 0, 0.8, 1.6, and 4.5. It is found that there is a broad-band of highly unstable 3-d secondary disturbances whose growth rates increase with increasing primary wave amplitude. At M(sub infinity) is less than or equal to 1.6, fundamental resonance dominates at relatively high (2-d) primary disturbance amplitude, while subharmonic resonance is characterized by a low (2-d) primary amplitude. At M(sub infinity) = 4.5, the subharmonic instability which arises from the second mode disturbance is the strongest type of secondary instability. The influence of the inclination, theta, of the primary wave with respect to the mean flow direction on secondary instability is investigated at M(sub infinity) = 1.6 for small to moderate values of theta. It is found that the strongest fundamental instability occurs when the primary wave is inclined at 10 deg to the mean flow direction, although a 2-d primary mode yields the most amplified subharmonic. The subharmonic instability at a high value of theta (namely, theta = 45 deg) is also discussed. Finally, a subset of the secondary instability results are compared against direct numerical simulations.

Ng, Lian↗
NASA NTRS1989

Cosmic-ray neutron albedo dose in low-earth orbits

An earth albedo neutron environmental model is proposed which provides a way to estimate neutron exposure in low-earth orbit. It is shown that, in the predominantly low inclination orbits (i=28.5 deg) used in the U.S. space program, the neutron exposures are relatively low (0.7 cSv/y). The neutron exposures are more significant for polar orbital missions and even high inclination missions, such as Skylab (i=57 deg).

Wilson, J. W.↗
NASA NTRS1989

Radiation hazards in low earth orbit, polar orbit, geosynchronous orbit, and deep space

The predicted doses to the blood forming organs and skin of spacecraft crews in low inclination at high inclination and polar orbits, in LEO and in free space are reviewed. Doses from trapped solar radiation and galactic cosmic radiation are covered, and also those to be expected from anomalous, large solar particle events. They are compared with the maximum annual and career doses laid down by the National Council on Radiation protection (1987). The effect of spacecraft and space suit shielding is also considered. Space Shuttle flights have allowed extensive comparison of predicted doses with those measured experimentally. This has revealed some defects in the radiation and magnetic fields models used and has led to extensive reexamination of these models.

Mccormack, Percival D.↗
NASA NTRS1990

A search for eclipses of HD 114762 by a low-mass companion

HD 114762 has an unseen companion with a dynamical mass that satisfies the constraint mass sin i = 2.5 x 10 to the 31st gm. The companion is a good candidate for a planetary-mass object, but the inclination of its orbit is unknown and its mass is indeterminate. Tests were conducted for the specific case of a nearly edge-on orbit by looking for eclipses of HD 114762 by the companion. Although the a priori probability of an eclipse is low, this is a crucial case because the companion has its minimum mass if the orbit is edge on. No eclipses were found with a depth greater than 0.01 mag and, therefore, the inclination of the orbit of HD 114762 is less than 89 deg.

Robinson, Edward L.↗
NASA NTRS1990

Results in orbital evolution of objects in the geosynchronous region

The orbital evolution of objects at or near geosynchronous orbit (GEO) has been simulated to investigate possible hazards to working geosynchronous satellites. Orbits of both large satellites and small particles have been simulated, subject to perturbations by nonspherical geopotential terms, lunar and solar gravity, and solar radiation pressure. Large satellites in initially circular orbits show an expected cycle of inclination change driven by lunar and solar gravity, but very little altitude change. They thus have little chance of colliding with objects at other altitudes. However, if such a satellite is disrupted, debris can reach thousands of kilometers above or below the initial satellite altitude. Small particles in GEO experience two cycles driven by solar radiation: an expected eccentricity cycle and an inclination cycle not expected. Particles generated by GEO insertion stage solid rocket motors typically hit the earth or escape promptly; a small fraction appear to remain in persistent orbits.

Friesen, Larry Jay↗
NASA NTRS1990

Variable magnification glancing incidence x ray telescope

A multispectral glancing incidence x ray telescope is disclosed, which capable of broadband, high resolution imaging of solar and stellar x ray and extreme ultraviolet radiation sources includes a primary optical system which focuses the incoming radiation to a primary focus. Two or more ellipsoidal mirrors are positioned behind the primary focus at an inclination to the optical axis, each mirror having a concave surface coated with a multilayer synthetic microstructure coating to reflect a desired wavelength. The ellipsoidal mirrors are segments of respective ellipsoids having a common first focus coincident with the primary focus. A detector such as an x ray sensitive photographic film is positioned at the second focus of each of the ellipsoids so that each of the ellipsoidal mirrors may reflect the image at the first focus to the detector. In one embodiment the mirrors are inclined at different angles and has its respective second focus at a different location, separate detectors being located at the respective second focus. The mirrors are arranged so that the magnification and field of view differ, and a solenoid activated arm may withdraw at least one mirror from the beam to select the mirror upon which the beam is to impinge so that selected magnifications and fields of view may be detected.

Hoover, Richard↗
NASA NTRS1990

Circumnuclear ionized gas in starburst nuclei

In order to study kinematical properties of starburst nuclei (SBNs), researchers made high-resolution spectroscopy of fifteen SBNs in the H alpha region using an intensified Reticon system attached to the coude focus of the 188-cm reflector at the Okayama Astrophysical Observatory. The instrumental resolution is 21 km s(-1) Full Width Half Maximum (FWHM) at lambda sub H alpha. As for the archetypical SBN, Mrk 538 (=NGC 7714), researchers present high-resolution emission line profiles of several species of ions such as (OIII), (NII), (SII), and (OII). Main results and conclusions are summarized. It has been known that emission-line profiles of SBNs are symmetrical and narrow. However, this high-resolution spectroscopy shows that the observed emission-line profiles of the SBNs have the following asymmetrical patterns; blueward, redward, and double-peaked. It is known that such features have been observed for narrow line regions (NLRs) of active galactic nuclei (AGNs). There is no remarkable correlation between the asymmetry index and the reddening indicator such as a Balmer decrement. Thus the line asymmetry is not attributed to inhomogeneous obscuration in the emitting regions. The observed FWHMs of the H alpha emission lines cover a range from 85 km s(-1) to 318 km s(-1) and are slightly larger than those of (NII) lambda 6584A emission except for the double-peaked SBNs. The FWHMs of H alpha emission show a good correlation with sin i (i is an inclination angle of galaxy). This correlation means that the FWHMs of the SBNs suffer significantly from rotational broadening. Mrk 52 is an anomalous SBN because it has narrow emission line widths for its high inclination angle (cf. Taniguchi 1987). From the above correlation, it is estimated that the intrinsic (i.e., rotation free) FWHMs of H alpha emission are about 50 km s(-1).

Taniguchi, Yoshiaki↗
NASA NTRS1991

Late stages of accumulation and early evolution of the planets

Recently developed solutions of problems are discussed that were traditionally considered fundamental in classical solar system cosmogony: determination of planetary orbit distribution patterns, values for mean eccentricity and orbital inclinations of the planets, and rotation periods and rotation axis inclinations of the planets. Two important cosmochemical aspects of accumulation are examined: the time scale for gas loss from the terrestrial planet zone, and the composition of the planets in terms of isotope data. It was concluded that the early beginning of planet differentiation is a function of the heating of protoplanets during collisions with large (thousands of kilometers) bodies. Energetics, heat mass transfer processes, and characteristic time scales of these processes at the early stages of planet evolution are considered.

Vityazev, Andrey V.↗
NASA NTRS1990

Radiation experiments on Cosmos 2044: K-7-41, parts A, B, C, D, E

The Cosmos 2044 biosatellite mission offered the opportunity for radiation measurements under conditions which are seldom available (an inclination of 82.3 deg and attitude of 294 x 216 km). Measurements were made on the outside of the spacecraft under near-zero shielding conditions. Also, this mission was the first in which active temperature recorders (the ATR-4) were flown to record the temperature profiles of detector stacks. Measurements made on this mission provide a comparison and test for modeling of depth doses and LET spectra for orbital parameters previously unavailable. Tissue absorbed doses from 3480 rad (252 rad/d) down to 0.115 rad (8.33 mrad/d) were measured at different depths (0.0146 and 3.20 g/sq cm, respectively) with averaged TLD readings. The LET spectra yielded maximum and minimum values of integral flux of 27.3 x 10(exp -4) and 3.05 x 10(exp -4)/sq cm/s/sr, of dose rate of 7.01 and 1.20 mrad/d, and of dose equivalent rate of 53.8 and 11.6 mrem/d, for LET(sub infinity)-H2O is greater than or equal to 4 keV/micron. Neutron measurements yielded 0.018 mrem/d in the thermal region, 0.25 mrem/d in the resonance region and 3.3 mrem/d in the high energy region. The TLD depth dose and LET spectra were compared with calculations from the modeling codes. The agreement is good but some further refinements are in order. In comparing measurements on Cosmos 2044 with those from previous Cosmos missions (orbital inclinations of 62.8 deg) there is a greater spread (maximum to minimum) in depth doses and an increased contribution from GCRs, and higher LET particles, in the heavy particle fluxes.

Frank, A. L.↗
NASA NTRS1990

Optimization and guidance of trajectories for coplanar, aeroassisted orbital transfer

Guidance trajectories for coplanar aeroassisted orbital transfer (AOT) from high earth orbit to LEO are presently optimized under the assumption of trajectory control during its endoatmospheric phase by alpha-dependent lift coefficient. Optimal trajectories are first computed by minimizing the total velocity impulse required for AOT; attention is then given to guidance trajectories capable of approximating such key properties of the optimal trajectories as minimum altitude, exit velocity, and exit path inclination, in real time. A switch is made from target-altitude guidance to target path inclination-guidance according to the velocity depletion required for optimum flight.

Miele, A.↗
NASA NTRS1991

Orbits of the six new satellites of Neptune

Orbital elements are presented for the six small satellites of Neptune, 1989N1 through 1989N6, discovered by Voyager 2. Details of the image and orbit analyses are examined. The solution for the orbits of the six satellites is presented in terms of geometric classical Keplerian elements. All six are in nearly circular direct orbits; most of the satellites have low inclinations, except the innermost, 1989N6, which is inclined at 4.7 deg to Neptune's equator.

Owen, W. M., Jr.↗
NASA NTRS1991

Laser geodynamic satellite (LAGEOS II)

The Laser Geodynamic Satellite 2 (LAGEOS 2) is nearly identical to the LAGEOS 1 satellite, which was launched by NASA in 1976. However, LAGEOS 2 is completely passive, and is equipped with fused silian corner reflectors for ranging with ground-based lasers. The addition of LAGEOS 2 will provide the GSFC laser network with significantly increased satellite tracking opportunities, because LAGEOS 1 is at a 110-degree inclination and LAGEOS 2 will be at a 52-degree inclination. The flight profile is given, and information is presented in tabular form on the following topics: Deep Space Network support, frequency assignments, telemetry, tracking, and tracking support responsibility.

Portelli, C.↗
NASA NTRS1992

Prediction of LDEF ionizing radiation environment

The Long Duration Exposure Facility (LDEF) spacecraft flew in a 28.5 deg inclination circular orbit with an altitude in the range from 172 to 258.5 nautical miles. For this orbital altitude and inclination two components contribute most of the penetrating charge particle radiation encountered - the galactic cosmic rays and the geomagnetically trapped Van Allen protons. Where shielding is less than 1.0 g/sq cm geomagnetically trapped electrons make a significant contribution. The 'Vette' models together with the associated magnetic filed models were used to obtain the trapped electron and proton fluences. The mission proton doses were obtained from the fluence using the Burrell proton dose program. For the electron and bremsstrahlung dose we used the Marshall Space Flight Center (MSFC) electron dose program. The predicted doses were in general agreement with those measured with on-board thermoluminescent detector (TLD) dosimeters. The NRL package of programs, Cosmic Ray Effects on MicroElectronics (CREME), was used to calculate the linear energy transfer (LET) spectrum due to galactic cosmic rays (GCR) and trapped protons for comparison with LDEF measurements.

Watts, John W.↗
NASA NTRS1990

Final design of a space debris removal system

The objective is the removal of medium sized orbital debris in low Earth orbits. The design incorporates a transfer vehicle and a netting vehicle to capture the medium size debris. The system is based near an operational space station located at 28.5 degrees inclination and 400 km altitude. The system uses ground based tracking to determine the location of a satellite breakup or debris cloud. This data is unloaded to the transfer vehicle, and the transfer vehicle proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit, where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground, and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the system has the ability to capture 50 pieces of orbital debris. One mission will take about six months. The system is designed to allow for a 30 degree inclination change on the outgoing and incoming trips of the transfer vehicle.

Carlson, Erika↗
NASA NTRS1992

Origin of orbital debris impacts on Long Duration Exposure Facility's (LDEF) trailing surfaces

Orbital debris tracked by the US Space Command is mostly in near circular orbit around the Earth. If small debris were in the same types of orbits, there would be very few orbital debris impacts on the Long Duration Exposure Facility's (LDEF's) trailing surfaces. However, at least 15 percent of the impacts found on the trailing A03 gold surface was found to be orbital debris impacts. This measurement suggests that the orbital distribution of small debris is not the same as that of larger debris. Although this is not a total surprise, since modelling of satellite breakups has predicted different distributions, it does raise questions as to what types of orbits could be responsible for these impacts. A model was developed to explain these LDEF results. The model calculates the expected debris impact crater distribution around LDEF, as a function of debris orbital parameters. The results show that only low inclination and highly elliptical orbits could be responsible for these impacts. The most common object left in this type of orbit is an orbital transfer stage, used by the US and ESA to place objects into geosynchronous orbit, and inclinations near 28 and 7 degrees for the US and ESA, respectively. Even large fragments from satellites, which break up in these types of orbits, are difficult to observe from the ground; consequently, little is known about the number and characteristics of breakups in these orbits. The LDEF data suggest that these objects are breaking up. The LDEF data also suggest that the ratio of the contribution of small debris from this type of orbit to the contribution from circular orbits is about an order of magnitude larger than the same ratio for debris tracked by the US Space Command.

Kessler, Donald J.↗
NASA NTRS1992

Analysis of orbital perturbations acting on objects in orbits near geosynchronous earth orbit

The paper presents a numerical investigation of orbital evolution for objects started in GEO or in orbits near GEO in order to study potential orbital debris problems in this region. Perturbations simulated include nonspherical terms in the earth's geopotential field, lunar and solar gravity, and solar radiation pressure. Objects simulated include large satellites, for which solar radiation pressure is insignificant, and small particles, for which solar radiation pressure is an important force. Results for large satellites are largely in agreement with previous GEO studies that used classical perturbation techniques. The orbit plane of GEO satellites placed in a stable plane orbit inclined approximately 7.3 deg to the equator experience very little precession, remaining always within 1.2 percent of their initial orientation. Solar radiation pressure generates two major effects on small particles: an orbital eccentricity oscillation anticipated from previous research, and an oscillation in orbital inclination.

Friesen, Larry J.↗
NASA NTRS1991

The tropical rainfall measuring mission (TRMM) and its role in studies of climate variations

Adequate measurement of rainfall over the global tropics can only be made from space, using an inclined low orbit and a combination of sensors. A relatively low-budget earth probe satellite called the tropical rainfall measuring mission (TRMM) is described. It is an approved joint project between the United States and Japan, with an intended launch by the Japanese in 1996. It will fly at an orbit elevation of 350 km and an inclination of 35 deg. Radiation instruments were added to the payload in late 1990. The TRMM rain package, its instruments, expected products, and some results of prelaunch research on the orbit sampling, rain retrievals, and ground validation procedures are discussed.

Simpson, Joanne↗
NASA NTRS1992

On Martell and Kaitchuck's model for the intermediate polar FO Aquarii

Attention is given to the proposals of Martell and Kaitchuck (1991) that FO Aqr is a low-inclination system, rather than an eclipsing system, as recently claimed, and that the dominant periodicity (21 min) is the beat period rather than the white dwarf spin period, as is commonly supposed. It is shown that both proposals make it harder to understand the observations of this star, while there is no substantive evidence in their favor. It is concluded that FO Aqr is most likely a high-inclination system in which the secondary eclipses part of the accretion flow.

Mukai, Koji↗