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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Simulations of Hayabusa2 Atmospheric Entry and Comparisons with Data from the Imaging Campaign

Results from flow and radiation simulations for the Hayabusa2 Sample Return Capsule (SRC) along its best-estimated trajectory (BET) are presented. Flow fields are first computed at several points along the best-estimated trajectory for a freestream consisting of N2, O2, Ar, CO2, and H2O; the last three are trace species in Earth’s atmosphere. The thermal response of an assumed ablative material is estimated and flow fields are recomputed at each time point with modified surface temperature distributions. The spectral radiance, from the combination of an aeroheated capsule and the high-temperature shock layer around it, is computed on an imaging plane for a given view angle and slant range at each time point. The radiance is transported through the intervening atmosphere between the Hayabusa2 SRC and the observing aircraft and upon integration over solid angle representing the field of view of the instruments converted to a spectral irradiance. The spectral irradiance is convolved with the instrument function to obtain results that can be directly compared with measurement. Fair to good comparisons with measurements required shifting the time coordinate of measurements by 7.5 s. The disagreement between prediction and measurement is substantial after about 72.5 s along the BET. Additional computations seem to support the idea of flow transition over the capsule.

Atmospheric entry↗
NASA NTRSDate not supplied

Simulations of Hayabusa2 Atmospheric Entry and Comparisons with Data from the Imaging Campaign

Results from flow and radiation simulations for the Hayabusa2 Sample Return Capsule (SRC) along its best-estimated trajectory (BET) are presented. Flow fields are first computed at several points along the best-estimated trajectory for a freestream consisting of N2, O2, Ar, CO2, and H2O; the last three are trace species in Earth’s atmosphere. The thermal response of an assumed ablative material is estimated and flow fields are recomputed at each time point with modified surface temperature distributions. The spectral radiance, from the combination of an aeroheated capsule and the high-temperature shock layer around it, is computed on an imaging plane for a given view angle and slant range at each time point. The radiance is transported through the intervening atmosphere between the Hayabusa2 SRC and the observing aircraft and upon integration over solid angle representing the field of view of the instruments converted to a spectral irradiance. The spectral irradiance is convolved with the instrument function to obtain results that can be directly compared with measurement. Fair to good comparisons with measurements required shifting the time coordinate of measurements by 7.5 s. The disagreement between prediction and measurement is substantial after about 72.5 s along the BET. Additional computations seem to support the idea of flow transition over the capsule.

Atmospheric entry↗
NASA NTRSDate not supplied

Sample Return and Preliminary Examination Timeline for the OSIRIS-REx Mission

NASA’s OSIRIS-REx spacecraft collected a sample of asteroid (101955) Bennu on October 20, 2020, using the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) [1,2,3]. After sample acquisition, the TAGSAM collection head was stowed in the Sample Return Capsule (SRC; Fig. 1) for transport back to Earth. On September 24, 2023, the OSIRIS-Rex spacecraft will fly by Earth and release the SRC, which will land at the Utah Test and Training Range (UTTR). The sample will be transported to the OSIRIS-REx curation facility, located within NASA’s Johnson Space Center (JSC), where it will be examined, cataloged, and allocated for scientific analyses. Here we describe the timeline of operations for the return, recovery, and initial characterization of the Bennu sample.

Asteroid↗
NASA NTRS2024

Investigating the Physical Modification of the Bennu Sample During Entry, Descent, and Landing

On September 24, 2023, the OSIRIS-REx Sample Return Capsule (SRC) entered Earth’s atmosphere and landed in the Utah Test and Training Range (UTTR). Preliminary examination of the returned Bennu sample has confirmed that OSIRIS-REx sample mass exceeds the mission requirement of 60 g of material. The sample consists of particles that range from a few centimeters to microscopic fines. During the SRC’s entry, descent, and landing (EDL) sequence, it may have experienced (i) peak decelerations of 10s of g (ii) tumbling, and (iii) touchdown at approximately 10 m/s, which could have induced physical modification of the sample. In addition, the act of sampling may have altered or biased the physical properties of the collected materials. Here, we investigate the likelihood and extent of physical modification of the sample between collection and return using observations and modeling. This work addresses the mission’s hypothesis 12, which concerns, in part, the modification of the sample during collection and Earth entry.

asteroid↗
NASA NTRS1980

Flame tube parametric studies for control of fuel bound nitrogen using rich-lean two-stage combustion

An experimental parametric study of rich-lean two-stage combustion in a flame tube is described and approaches for minimizing the conversion of fuel-bound nitrogen to nitrogen oxides in a premixed, homogeneous combustion system are evaluated. Air at 672 K and 0.48 MPa was premixed with fuel blends of propane, toluene, and pyridine at primary equivalence ratios ranging from 0.5 to 2.0 and secondary equivalence ratios of 0.5 to 0.7. Distillates of SRC-II, a coal syncrude, were also tested. The blended fuels were proportioned to vary fuel hydrogen composition from 9.0 to 18.3 weight percent and fuel nitrogen composition from zero to 1.5 weight percent. Rich-lean combustion proved effective in reducing fuel nitrogen to NO sub x conversion; conversion rates up to 10 times lower than those normally produced by single-stage combustion were achieved. The optimum primary equivalence ratio, where the least NO sub x was produced and combustion efficiency was acceptable, shifted between 1.4 and 1.7 with changes in fuel nitrogen content and fuel hydrogen content. Increasing levels of fuel nitrogen content lowered the conversion rate, but not enough to avoid higher NO sub x emissions as fuel nitrogen increased.

Schultz, D. F.↗
NASA NTRS1981

Catalytic combustion of coal-derived liquids

A noble metal catalytic reactor was tested with three grades of SRC 2 coal derived liquids, naphtha, middle distillate, and a blend of three parts middle distillate to one part heavy distillate. A petroleum derived number 2 diesel fuel was also tested to provide a direct comparison. The catalytic reactor was tested at inlet temperatures from 600 to 800 K, reference velocities from 10 to 20 m/s, lean fuel air ratios, and a pressure of 3 x 10 to the 5th power Pa. Compared to the diesel, the naphtha gave slightly better combustion efficiency, the middle distillate was almost identical, and the middle heavy blend was slightly poorer. The coal derived liquid fuels contained from 0.58 to 0.95 percent nitrogen by weight. Conversion of fuel nitrogen to NOx was approximately 75 percent for all three grades of the coal derived liquids.

Bulzan, D. L.↗
NASA NTRS1982

Low NO sub x heavy fuel combustor concept program. Phase 1A: Combustion technology generation coal gas fuels

Combustion tests of two scaled burners using actual coal gas from a 25 ton/day fluidized bed coal gasifier are described. The two combustor configurations studied were a ceramic lined, staged rich/lean burner and an integral, all metal multiannual swirl burner (MASB). The tests were conducted over a range of temperature and pressures representative of current industrial combustion turbine inlet conditions. Tests on the rich lean burner were conducted at three levels of product gas heating values: 104, 197 and 254 btu/scf. Corresponding levels of NOx emissions were 5, 20 and 70 ppmv. Nitrogen was added to the fuel in the form of ammonia, and conversion efficiencies of fuel nitrogen to NOx were on the order of 4 percent to 12 percent, which is somewhat lower than the 14 percent to 18 percent conversion efficiency when src-2 liquid fuel was used. The MASB was tested only on medium btu gas (220 to 270 btu/scf), and produced approximately 80 ppmv NOx at rated engine conditions. Both burners operated similarly on actual coal gas and erbs fuel, and all heating values tested can be successfully burned in current machines.

Sherlock, T. P.↗
NASA NTRS1982

On the geodetic applications of simultaneous range-differencing to LAGEOS

The possibility of improving the accuracy of geodetic results by use of simultaneously observed ranges to Lageos, in a differencing mode, from pairs of stations was studied. Simulation tests show that model errors can be effectively minimized by simultaneous range differencing (SRD) for a rather broad class of network satellite pass configurations. The methods of least squares approximation are compared with monomials and Chebyshev polynomials and the cubic spline interpolation. Analysis of three types of orbital biases (radial, along- and across track) shows that radial biases are the ones most efficiently minimized in the SRC mode. The degree to which the other two can be minimized depends on the type of parameters under estimation and the geometry of the problem. Sensitivity analyses of the SRD observation show that for baseline length estimations the most useful data are those collected in a direction parallel to the baseline and at a low elevation. Estimating individual baseline lengths with respect to an assumed but fixed orbit not only decreases the cost, but it further reduces the effects of model biases on the results as opposed to a network solution. Analogous results and conclusions are obtained for the estimates of the coordinates of the pole.

Pablis, E. C.↗
NASA NTRS1983

Summary of synfuel characterization and combustion studies

Combustion component research studies aimed at evolving environmentally acceptable approaches for burning coal derived fuels for ground power applications were performed at the NASA Lewis Research Center under a program titled the ""Critical Research and Support Technology Program'' (CRT). The work was funded by the Department of Energy and was performed in four tasks. This report summarizes these tasks which have all been previously reported. In addition some previously unreported data from Task 4 is also presented. The first, Task 1 consisted of a literature survey aimed at determining the properties of synthetic fuels. This was followed by a computer modeling effort, Task 2, to predict the exhaust emissions resulting from burning coal liquids by various combustion techniques such as lean and rich-lean combustion. The computer predictions were then compared to the results of a flame tube rig, Task 3, in which the fuel properties were varied to simulate coal liquids. Two actual SRC 2 coal liquids were tested in this flame tube task.

Schultz, D. F.↗
NASA NTRS1984

Notes on the system TV Geminorum

Low-resolution SWP spectra and high-resolution LWR spectra of the SRc variable star TV Gem have been studied. The available ultraviolet spectrophotometry and UBV photometry of the system can be interpreted in terms of the blended light from a B3.5 IV star and an M1 Iab star. The separation of the two stars is less than about 3 arc sec. Since the magnitude difference is a minimum in the B filter, being about 1.6 mag there, direct observation of TV Gem in a passband at 4400 A under conditions of good seeing might reveal the blue companion. No evidence was found for absorption lines of Mg II formed in the part of the wind of the M star which is projected against the disk of the B star.

Underhill, A. B.↗
NASA NTRS1984

Dark Cloud and Globule Distribution for Galactic Longitudes 230 to 360 Degrees

A catalogue of dark nebulae and globules was compiled from a study of the ESO-B and SRC-J sky atlas for galactic longitudes 230 deg 1 360 deg. This catalogue closes the great southern gap open since the work of Lynds (1962). Listed were 489 dark nebulae and 311 globules. The catalogue contains positions, sizes, opacities, and the van den Bergh classification on the filamentary morphology of dark clouds. Statistics are presented concerning the northern and southern distributions and sizes of the nebulae.

Feitzinger, J. V.↗
NASA NTRS1987

Axial ratios and orientations for 100 Galactic globular star clusters

Axial ratios and major-axis orientations determined from image processing of Palomar and SRC Sky Survey material are tabulated for a sample of 100 Galactic globular clusters. From a subsample of 99 clusters, the mean axial ratio is found to be 0.93 + or - 0.01. Given that only 32 percent are flatter than b/a less than 0.9, and 5 percent flatter than 0.8, the clusters are found to be quite spherical. As predicted by King (1961 and 1966), tidal interactions by the Galaxy on the cluster are not the means by which the observed ellipticities are produced. Rather, Galactic absorption effects may have a moderate but not dominant effect on the clusters' observed ellipticities, as suggested by van den Bergh (1984). The alternate mechanisms of cluster rotation or anisotropic internal velocity distributions, or both, are considered to be more likely. The observed distribution of axial ratios is statistically indistinguishable from that of a similar-size sample of rotationally flattened clusters, which have axial-ratio values lying in the range of 0.75 less than b/a less than 0.83, and the major axes of which are oriented randomly in space.

White, Raymond E.↗
NASA NTRS1990

Aerothermodynamic environments for Mars entry, Mars return, and lunar return aerobraking missions

The aeroheating environments to vehicles undergoing Mars aerocapture, earth aerocapture from Mars, and earth aerocapture from the moon are presented. An engineering approach for the analysis of various types of vehicles and trajectories was taken, rather than performing a benchmark computation for a specific point at a selected time point in a trajectory. The radiation into Mars using the Mars Rover Sample Return (MRSR) 2-ft nose radius bionic remains a small contributor of heating for 6 to 10 km/sec; however, at 12 km/sec it becomes comparable with the convection. For earth aerocapture, returning from Mars, peak radiation for the MRSR SRC is only 25 percent of the peak convection for the 12-km/sec trajectory. However, when large vehicles are considered with this trajectory, peak radiation can become 2 to 4 times higher than the peak convection. For both Mars entry and return, a partially ablative Thermal Protection System (TPS) would be required, but for Lunar Transfer Vehicle return an all-reusable TPS can be used.

Rochelle, W. C.↗
NASA NTRS1991

TPS design for aerobraking at Earth and Mars

An investigation was made to determine the feasibility of using an aerobrake system for manned and unmanned missions to Mars, and to Earth from Mars and lunar orbits. A preliminary thermal protection system (TPS) was examined for five unmanned small nose radius, straight bi-conic vehicles and a scaled up Aeroassist Flight Experiment (AFE) vehicle aerocapturing at Mars. Analyses were also conducted for the scaled up AFE and an unmanned Sample Return Cannister (SRC) returning from Mars and aerocapturing into Earth orbit. Also analyzed were three different classes of lunar transfer vehicles (LTV's): an expendable scaled up modified Apollo Command Module (CM), a raked cone (modified AFT), and three large nose radius domed cylinders. The LTV's would be used to transport personnel and supplies between Earth and the moon in order to establish a manned base on the lunar surface. The TPS for all vehicles analyzed is shown to have an advantage over an all-propulsive velocity reduction for orbit insertion. Results indicate that TPS weight penalties of less than 28 percent can be achieved using current material technology, and slightly less than the most favorable LTV using advanced material technology.

Williams, S. D.↗
NASA NTRS1992

Microgravity accelerometer characterization on Columbia STS-32 mission

The Honeywell In-Space Accelerometer (HISA) is a three-axis microgravity accelerometer instrument package recently developed by Honeywell Systems and Research Center (SRC) to monitor oscillatory and transient accelerations onboard spacecraft and spaceborne structures. The HISA was designed to be co-located with materials and life sciences experiments to record real-time accelerometer event data, sampling time, and temperature. The HISA was originally developed to monitor the microgravity disturbances associated with a polymer morphology experiment developed by 3M Company in Minneapolis, Minnesota. The HISA was first flight tested with the 3M experiment on the Space Shuttle Atlantis STS-34 in October 1989. The HISA was successfully flown on a second shuttle mission (Columbia STS-32 in January 1990) in support of the NASA JSC-sponsored Microgravity Disturbances Experiment (MDE), which focused on the effects of microgravity disturbances on the growth of high-quality Indium crystals. The primary objective of the STS-32 MDE experiment was to investigate the effects of crew-induced gravity disturbances on the microstructure (crystal defects and uniformity of impurity distribution) of float-zone-grown crystals. The float-zone technique involves establishing a suspended molten zone between two cylindrical samples a pure, single-crystal sample and an impure, polycrystalline sample. Microgravity disturbances due to crew treadmill activity and orbiter maneuvering system thruster firings were sensed and recorded by the HISA to understand their effects on the stability of the float zone. The principle of operation of the HISA, the flight configuration of the HISA supporting the MDE experiment, and the characterization of STS-32 treadmill disturbance data are summarized.

Schoess, Jeff↗
NASA NTRS1993

Scheduling with partial orders and a causal model

In an ongoing project at Honeywell SRC, we are constructing a prototype scheduling system for a NASA domain using the 'Time Map Manager' (TMM). The TMM representations are flexible enough to permit the representation of precedence constraints, metric constraints between activities, and constraints relative to a variety of references (e.g., Mission Elapsed Time vs. Mission Day). The TMM also supports a simple form of causal reasoning (projection), dynamic database updates, and monitoring specified database properties as changes occur over time. The greatest apparent advantage to using the TMM is the flexibility added to the scheduling process: schedules are constructed by a process of 'iterative refinement,' in which scheduling decisions correspond to constraining an activity either with respect to another activity or with respect to one time line. The schedule becomes more detailed as activities and constraints are added. Undoing a scheduling decision means removing a constraint, not removing an activity from a specified place on the time line. For example, we can move an activity around on the time line by deleting constraints and adding new ones.

Boddy, Mark↗
NASA NTRS1993

The United States digital recording industry

The recording industry resembles the semiconductor industry in several aspects. Both are large (greater than $60 Billion/year revenues); both are considered critical technologies supporting national objectives; both are experiencing increased competition from foreign suppliers; they recognize significant opportunities for both technological and market growth in the decade to come; and both realize that a key to this future growth lies in alliances among industry, academia, and government. The semiconductor industry has made significant investments in alliances relating to manufacturing technologies (SEMATECH) and to joint long-term technology research centered in universities (SRC). The federal government has provided funding support of these efforts in recognition of the critical roles semiconductor technologies play in national interests. The recording industry is now also forming critical alliances, but has been slower in starting and in gaining broad recognition by government agencies and legislators that the industry needs federal support. Traditionally, the recording industry has been viewed as mature, stable, and, while critical to national interests, able to chart and fund its own course toward future national needs. That perception is fortunately changing.

Simonds, John L.↗