Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “compact objects”

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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) Instrument Improvements

The Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) combines airborne sun tracking and sky scanning with grating spectroscopy to improve knowledge of atmospheric constituents and their links to air-pollution and climate. Hyper-spectral measurements of direct-beam solar irradiance provide retrievals of gas constituents, aerosol optical depth, and aerosol and thin cloud optical properties. Sky radiance measurements in the principal and almucantar planes enhance retrievals of aerosol absorption, aerosol type, and size mode distribution. Zenith radiance measurements are used to retrieve cloud properties and phase, which in turn are used to quantify the radiative transfer below cloud layers. These airborne measurements tighten the closure between satellite and ground-based measurements. In contrast to the Ames Airborne Tracking Sunphotometer (AATS-14) predecessor instrument, new technologies for each subsystem have been incorporated into 4STAR. In particular, 4STAR utilizes a modular sun-trackingsky-scanning optical head with fiber optic signal transmission to rack mounted spectrometers, permitting miniaturization of the external optical head, and spectrometerdetector configurations that may be tailored for specific scientific objectives. This paper discusses technical challenges relating to compact optical collector design, radiometric dynamic range and stability, and broad spectral coverage at high resolution. Test results benchmarking the performance of the instrument against the AATS-14 standard and emerging science requirements are presented.

Atmopheric Research (4STAR)↗
NASA NTRS1992

Low energy CMOS for space applications

The current focus of NASA's space flight programs reflects a new thrust towards smaller, less costly, and more frequent space missions, when compared to missions such as Galileo, Magellan, or Cassini. Recently, the concept of a microspacecraft was proposed. In this concept, a small, compact spacecraft that weighs tens of kilograms performs focused scientific objectives such as imaging. Similarly, a Mars Lander micro-rover project is under study that will allow miniature robots weighing less than seven kilograms to explore the Martian surface. To bring the microspacecraft and microrover ideas to fruition, one will have to leverage compact 3D multi-chip module-based multiprocessors (MCM) technologies. Low energy CMOS will become increasingly important because of the thermodynamic considerations in cooling compact 3D MCM implementations and also from considerations of the power budget for space applications. In this paper, we show how the operating voltage is related to the threshold voltage of the CMOS transistors for accomplishing a task in VLSI with minimal energy. We also derive expressions for the noise margins at the optimal operating point. We then look at a low voltage CMOS (LVCMOS) technology developed at Stanford University which improves the power consumption over conventional CMOS by a couple of orders of magnitude and consider the suitability of the technology for space applications by characterizing its SEU immunity.

Panwar, Ramesh↗
NASA NTRS2003

Buoyancy Effects in Fully-Modulated, Turbulent Diffusion Flames

Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The objective of this experiment (PuFF, for Pulsed-Fully Flames) is to increase the fundamental understanding of the fuel/air mixing and combustion behavior of pulsed, turbulent diffusion flames by conducting experiments in microgravity. In this research the fuel jet is fully-modulated (i.e., completely shut off between pulses) by an externally controlled valve system. This gives rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing compared to acoustically excited or partially-modulated jets. Normal-gravity experiments suggest that the fully-modulated technique also has the potential for producing turbulent jet flames significantly more compact than steady flames with no increase in exhaust emissions. The technique also simplifies the combustion process by avoiding the acoustic forcing generally present in pulsed combustors. Fundamental issues addressed in this experiment include the impact of buoyancy on the structure and flame length, temperatures, radiation, and emissions of fully-modulated flames.

Hermanson, J. C.↗
NASA NTRS1980

Compact positioning flange

Flange adjusts center of rotation of gimble-mounted objects such as telescopes. Three aluminum plates are machined to have interlocking orthogonal keys and ways. Outer plate is mounted to shaft. Inner plate is attached to object. Middle and inner plate slide along on axis. Screws slide in slots parallel to ways for adjustment, then tighten to lock position along each axis. Device is similar to crossed ways found on industrial machine tools, but simpler, lighter, and much smaller.

Hooper, S. L.↗
NASA NTRS1984

Waste collection subsystem study

Practical ways were explored of improving waste compaction and of providing rapid turnaround between flights at essentially no cost for the space shuttle waste collection subsystem commode. Because of the possible application of a fully developed shuttle commode to the space station, means of providing waste treatment without overboard venting were also considered. Three basic schemes for compaction and rapid turnaround, each fully capable of meeting the objectives, were explored in sufficient depth to bring out the characteristic advantages and disadvantages of each. Tradeoff comparisons were very close between leading contenders and efforts were made to refine the design concepts sufficiently to justify a selection. The concept selected makes use of a sealed canister containing wastes that have been forcibly compacted, which is removable in flight. No selection was made between three superior non-venting treatment methods owing to the need for experimental evaluations of the processes involved. A system requirements definition document has been prepared to define the task for a test embodiment of the selected concept.

Source record↗
NASA NTRS1994

Infrared to x-ray spectral energy distributions of high redshift quasars

We have observed 14 quasars with z greater than 2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z greater than 3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index alpha(sub E)=1.8(sup +2.1, sub -1.4) and no evidence for absorption in excess of the galactic column (alpha(sub E)=1.00(sup +0.28, sub -0.32) assuming N(sub H)=N(sub H)(Gal)). A Position Sensitive Proportional Counter (PSPC) hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, (alpha(sub E)) approximately equals 1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z greater than 2.5, the mean (alpha(sub ox)) is approximately 1.8. This is larger than the mean for quasars with z less than 2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, (alpha(sub ox)) is approximately 1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.

Bechtold, Jill↗
NASA NTRS1984

The Gamma-Ray Observatory mission objectives and its significance for gamma-ray astronomy

The Gamma Ray Observatory (GRO) is an approved NASA mission, programmed for launch in 1988. Its complement of four detectors has established goals: (1) to study the nature of compact gamma-ray sources such as neutron stars and black holes, or objects whose nature is yet to be understood; (2) to search for evidence of nucleosynthesis especially in the regions of supernovae; (3) to study structural features and dynamical properties of the Galaxy; (4) to explore other galaxies, especially the extraordinary types such as radio, Seyferts, and quasars; and (5) to study cosmological effects by examining the diffuse radiation in detail. This paper discusses the design, objectives, and expected scientific results of each of the GRO instruments in view of the GRO mission goals.

Bertsch, D. L.↗
NASA NTRS2013

Accommodating Thickness in Origami-Based Deployable Arrays

The purpose of this work is to create deployment systems with a large ratio of stowed-to-deployed diameter. Deployment from a compact form to a final flat state can be achieved through origami-inspired folding of panels. There are many models capable of this motion when folded in a material with negligible thickness; however, when the application requires the folding of thick, rigid panels, attention must be paid to the effect of material thickness not only on the final folded state, but also during the folding motion (i.e., the panels must not be required to flex to attain the final folded form). The objective is to develop new methods for deployment from a compact folded form to a large circular array (or other final form). This paper describes a mathematical model for modifying the pattern to accommodate material thickness in the context of the design, modeling, and testing of a deployable system inspired by an origami six-sided flasher model. The model is demonstrated in hardware as a 1/20th scale prototype of a deployable solar array for space applications. The resulting prototype has a ratio of stowed-to-deployed diameter of 9.2 (or 1.25 m deployed outer diameter to 0.136 m stowed outer diameter).

flasher↗
NASA NTRS2003

X-ray Emission from the Pre-planetary Nebula Henize 3-1475

We report the first detection of X-ray emission in a pre-planetary nebula, He 3-1475. Pre-planetary nebulae are rare objects in the short transition stage between the asymptotic giant branch (AGB) and planetary nebula evolutionary phases, and He 3-1475, characterized by a remarkable S-shaped chain of optical knots, is one of the most noteworthy members of this class. Observations with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory show the presence of compact emission coincident with the brightest optical knot in this bipolar object, which is displaced from the central star by 2'.7 along the polar axis. Model fits to the X-ray spectrum indicate an X-ray temperature and luminosity, respectively, of (4.3-5.7) x 10(exp 6) K and (4 +/- 1.4) x 10(exp 31) (D/5 kpc)(exp 2) ergs s(exp -1) respectively. Our 3 sigma upper limit on the luminosity of compact X-ray emission from the central star in He 3-1475 is approximately equal to 5 x 10(exp 31) (D/5 kpc)(exp 2) ergs s(exp -1). The detection of X-rays in He 3-1475 is consistent with models in which fast collimated post-AGB outflows are crucial to the shaping of nebulae; we discuss such models in the context of our observations.

circumstellar matter↗
NASA NTRS1988

Far-infrared data for symbiotic stars. II - The IRAS survey observations

IRAS survey data for all known symbiotic binaries are reported. S type systems have 25 micron excesses much larger than those of single red giant stars, suggesting that these objects lose mass more rapidly than do normal giants. D type objects have far-IR colors similar to those of Mira variables, implying mass-loss rate of about 10 to the -6th solar masses/yr. The near-IR extinctions of the D types indicate that their Mira components are enshrouded in optically thick dust shells, while their hot companions lie outside the shells. If this interpretation of the data is correct, then the very red near-IR colors of D type symbiotic stars are caused by extreme amounts of dust absorption rather than dust emission. The small group of D prime objects possesses far-IR colors resembling those of compact planetary nebulae or extreme OH/IR stars. It is speculated that these binaries are not symbiotic stars at all, but contain a hot compact star and an exasymptotic branch giant which is in the process of ejecting a planetary nebula shell.

Kenyon, S. J.↗
NASA NTRS1992

The bow shock structure of IRS 7 - Wind-wind collision near the Galactic center

New structural details of ionized gas associated with IRS 7, a mass-losing supergiant near the Galactic center, are reported, and radio continuum and theoretical maps are compared. High-resolution multiconfiguration VLA observations of IRS 7 reveal ionized gas with a bow shock structure at a wavelength of 2 cm. The apex of the bow shock is facing more toward the cluster of blue stellar objects, known as IRS 16, than Sgr A*, the compact nonthermal source near the Galaxy's dynamical center. It is inferred that the shape of the mass-losing envelope of IRS 7 is influenced by Galactic winds from IRS 16. It is concluded from a comparison of the morphology of the ionized envelope of IRS 7 with simple theoretical modeling of the bow shock structure that the shape of the shock results from the collision between the Galactic center and stellar winds rather than from the motion of IRS 7 through the interstellar medium.

Yusef-Zadeh, Farhad↗
NASA NTRS1993

Kinematic Dynamo In Turbulent Circumstellar Disks

Many circumstellar disks associated with objects ranging from protoplanetary nebulae, to accretion disks around compact stars allow for the generation of magnetic fields by an (alpha)omega dynamo. We have applied kinematic dynamo formalism to geometrically thin accretion disks. We calculate, in the framework of an adiabatic approximation, the normal mode solutions for dynamos operating in disks around compact stars. We then describe the criteria for a viable dynamo in protoplanetary nebulae, and discuss the particular features that make accretion disk dynamos different from planetary, stellar, and galactic dynamos.

Stepinski, T.↗
NASA NTRS2001

An Investigation of Fully Modulated, Turbulent Diffusion Flames in Reduced Gravity

Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The objective of this Flight-Definition experiment (PuFF, for Pulsed-Fully Flames) is to increase the fundamental understanding of the fuel/air mixing and combustion behavior of pulsed, turbulent diffusion flames by conducting experiments in microgravity. In this research the fuel jet is fully modulated (i.e., completely shut off between pulses) by an externally controlled valve system. This gives rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing mechanisms not operative for the case of acoustically excited or partially-modulated jets. The fully-modulated injection approach also simplifies the combustion process by avoiding the acoustic forcing generally present in pulsed combustors. Relatively little is known about the behavior of turbulent flames in reduced-gravity conditions, even in the absence of pulsing. Fundamental issues addressed in this experiment include the impact of buoyancy on the fuel/air mixing and combustion characteristics of fully-modulated flames. It is also important for the planned space experiments to establish the effects of confinement and oxidizer co-flow on these flames.

Hermanson, J. C.↗
NASA NTRS2013

Flight Performance Feasibility Studies for the Max Launch Abort System

In 2007, the NASA Engineering and Safety Center (NESC) initiated the Max Launch Abort System Project to explore crew escape system concepts designed to be fully encapsulated within an aerodynamic fairing and smoothly integrated onto a launch vehicle. One objective of this design was to develop a more compact launch escape vehicle that eliminated the need for an escape tower, as was used in the Mercury and Apollo escape systems and what is planned for the Orion Multi-Purpose Crew Vehicle (MPCV). The benefits for the launch vehicle of eliminating a tower from the escape vehicle design include lower structural weights, reduced bending moments during atmospheric flight, and a decrease in induced aero-acoustic loads. This paper discusses the development of encapsulated, towerless launch escape vehicle concepts, especially as it pertains to the flight performance and systems analysis trade studies conducted to establish mission feasibility and assess system-level performance. Two different towerless escape vehicle designs are discussed in depth: one with allpropulsive control using liquid attitude control thrusters, and a second employing deployable aft swept grid fins to provide passive stability during coast. Simulation results are presented for a range of nominal and off-nominal escape conditions.

Tarabini, Paul V.↗
NASA NTRSDate not supplied

Advanced Composite Solar Sail System (ACS3) Mission Update

The Advanced Composite Solar Sail System (ACS3) will be the first practical solar sail for the National Aeronautics and Space Administration. [1] ACS3 will also be the first spaceflight demonstration of NASA compact deployable composite boom technology.[2] The primary mission objective of ACS3 will be to deploy and characterize an 80-m2 composite boom structure solar sail technology in low Earth orbit. Extended mission goals will be to demonstrate controlled solar sailing flight via a series of orbit raising and lowering maneuvers. Target mission orbit is a 1000 km x 1000 km midnight-noon sun-synchronous orbit. Launch of ACS3 is scheduled for July 2023 with sail deployment in September 2023. Mission duration is expected to be six to nine months. The ACS3 solar sail vehicle is a 12U Cubesat consisting of a bus module, containing flight and solar sail control avionics, and a solar sail module, containing the composite booms and metallized polymer solar sail membranes of the solar sail structure stowed within a boom deployer mechanism. A four-camera instrument suite for 360-degree imaging of the ACS3 solar sail during and after deployment is also housed within the bus module. The ACS3 80-m2 solar sail design is a sub-scale version of an intermediate-size 500-m2 solar sail using NASA deployable composite boom technology. The sail consists of four metallized 2-m thick polyethylene naphthalate (PEN) 20-m2 triangular quadrants supported by four 7-m long lenticular cross-section composite booms. Booms are flattened and co-coiled for stowage within a tape-spool driven deployer mechanism. Total mass of the ACS3 space vehicle including solar sail is 16 kg. An overview of the ACS3 mission and mission systems will be provided in this presentation. This overview will include descriptions of the solar sail structures and materials technology used with ACS3, and discussion of the scalability and extensibility of the ACS3 solar sail to future larger-scale solar sailing mission requirements. An update on progress towards the launch of ACS3 in July 2023 will also be provided. References [1] https://www.nasa.gov/directorates/spacetech/small_spacecraft/ACS3 [2] https://www.nasa.gov/directorates/spacetech/game_changing_development/projects/dcb

Solar sail↗
NASA NTRS1992

An IRAS study of pre-main sequence stars in B209

We have constructed high resolution IRAS maps of the B209 star forming region in the Taurus complex. By combining survey scans with pointed observations using advanced techniques specially developed to handle IRAS data in crowded fields, we have constructed images that reveal two new premain-sequence (PMS) objects. One of these, IRAS 04114+2757G, has FIR colors close to those of typical T Tauri stars and is probably associated with a faint stellar object visible on the POSS prints. The other new PMS source, IRAS 04111+2800G, is a deeply embedded object not detected at 12 microns and not optically visible. The object is projected close to the center of an ammonia core. Our detection of compact blue and red shifted (C-12)O emission peaks around the position of IRAS 04111+2800G confirms the PMS nature and youth of this object. We have examined the reasons for the exclusion of IRAS 04111+2800G and IRAS 04114+2757G from the IRAS Point Source Catalog and estimated the incompleteness of the currently known sample of embedded PMS stars in Taurus. The implications for the determination of evolutionary time scales in low mass star formation are discussed.

Prusti, T.↗
NASA NTRS1993

On Magnetic Dynamos in Thin Accretion Disks around Compact and Young Stars

A variety of geometrically thin accretion disks commonly associated with such astronomical objects as X-ray binaries, cataclysmic variables, and protostars are likely to be seats of MHD dynamo actions. Thin disk geometry and the particular physical environment make accretion disk dynamos different from stellar, planetary, or even galactic dynamos. We discuss those particular features of disk dynamos with emphasis on the difference between protoplanetary disk dynamos and those associated with compact stars. We then describe normal mode solutions for thin disk dynamos and discuss implications for the dynamical behavior of dynamo-magnetized accretion disks.

Stepinski, T. F.↗
NASA NTRS2019

ADEPT Sounding Rocket One (SR-1) Flight Test

A sounding rocket flight test was conducted on a mechanically-deployed entry vehicle (DEV) known as the Adaptable Deployable Entry and Placement Technology (ADEPT). This flight test was a major milestone in a technology development campaign for ADEPT: the application of ADEPT for small secondary payloads. The test was conducted above White Sands Missile Range (WSMR), New Mexico on a SpaceLoft XL rocket on September 12, 2018. The first objective of the SR-1 flight test was to demonstrate that ADEPT could transform from a compact stowed configuration, separate from the launch vehicle, and successfully deploy exo-atmospherically into the desired low ballistic coefficient entry configuration. The second objective was to characterize the aerodynamic performance of the deployed configuration in order to evaluate the faceted blunt body geometry dynamic stability characteristics as it decelerated from supersonic to subsonic speeds.The ADEPT DEV had several sensors on-board and also leveraged third-party data sources for post-flight analysis and trajectory reconstruction. Based upon data review, the launch vehicle met exo-atmospheric delivery performance requirements of spin rate, no re-contact, separation velocity, and delivery altitude. The unique ADEPT forebody geometry (blunted octagonal pyramid, 0.7 m diameter at the rib tips) and aftbody configuration has never flown before. The forebody half cone angle at the ribs is 70 deg, while the half cone angle mid gore is 68.5 deg. The aftbody, where the 3U CubeSat 'payload' resides is a rectangular prism that extends ~ ½ the minimum forebody diameter behind the nose. Understanding DEV blunt body dynamic stability performance is critical for determining how they can be employed for atmospheric entry, descent and landing.The primary data products were used to perform flight mechanics analysis and reconstruct the as-flown trajectory. On-board video recovered post-flight demonstrated that the DEV achieved and maintained the desired entry configuration. Post-flight analyses showed that the vehicle met the threshold of achieving stable flight below Mach = 0.8. The ADEPT project has focused on ballistic, axisymmetric shapes as the logical 'first step' in mission infusion applications. With the current maturation and development of the ballistic (non-lifting) 1 m class ADEPT, the next step in ADEPT maturation is the focus on configurations that are capable of generating lift in order to accomplish aerocapture and precision landing mission capabilities. ADEPT is particularly attractive for evaluating various guidance and control approaches as the deployable structure enables attachment points for various actuation methods such as control surfaces, moving mass elements, or RCS thrusters. The ADEPT sounding rocket flight test provided a low-cost means of achieving significant system level maturity for the 1 m class ADEPT configuration. A description of the technology, system components, flight test execution, and conclusions will be described.

Cassell, Alan↗