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All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Atlas V Launch Incorporated NASA Glenn Thermal Barrier

In the Spring of 2002, Aerojet experienced a major failure during a qualification test of the solid rocket motor that they were developing for the Atlas V Enhanced Expendable Launch Vehicle. In that test, hot combustion gas reached the O-rings in the nozzle-to-case joint and caused a structural failure that resulted in loss of the nozzle and aft dome sections of the motor. To improve the design of this joint, Aerojet decided to incorporate three braided carbon-fiber thermal barriers developed at the NASA Glenn Research Center. The thermal barriers were used to block the searing-hot 5500 F pressurized gases from reaching the temperature-sensitive O-rings that seal the joint. Glenn originally developed the thermal barriers for the nozzle joints of the space shuttle solid rocket motors, and Aerojet decided to use them on the basis of the results of several successful ground tests of the thermal barriers in the shuttle rockets. Aerojet undertook an aggressive schedule to redesign the rocket nozzle-to-case joint with the thermal barriers and to qualify it in time for a launch planned for the middle of 2003. They performed two successful qualification tests (Oct. and Dec. 2002) in which the Glenn thermal barriers effectively protected the O-rings. These qualification tests saved hundreds of thousands of dollars in development costs and put the Lockheed-Martin/Aerojet team back on schedule. On July 17, 2003, the first flight of an Atlas V boosted with solid rocket motors successfully launched a commercial satellite into orbit from Cape Canaveral Air Force Station. Aero-jet's two 67-ft solid rocket boosters performed flawlessly, with each providing thrust in excess of 250,000 lbf. Both motors incorporated three Glenn-developed thermal barriers in their nozzle-to-case joints. The Cablevision satellite launched on this mission will be used to provide direct-to-home satellite television programming for the U.S. market starting in late 2003. The Atlas V is a product of the military's Enhanced Expendable Launch Vehicle program designed to provide assured military access to space. It can lift payloads up to 19,100 lb to geosynchronous transfer orbit and was designed to meet Department of Defense, commercial, and NASA needs. The Atlas V and Delta IV are two launch systems being considered by NASA to launch the Orbital Space Plane/Crew Exploration Vehicle. The launch and rocket costs of this mission are valued at $250 million. Successful application of the Glenn thermal barrier to the Atlas V program was an enormous breakthrough for the program's technical and schedule success.

Dunlap, Patrick H., Jr.↗
NASA NTRS2016

Stellar Laboratories

For the spectral analysis of high-resolution and high signal-to-noise (SN) spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation. Aims: To identify molybdenum lines in the ultraviolet (UV) spectra of the DA-type white dwarf G191B2B and the DO-type white dwarf RE 0503289 and, to determine their photospheric Mo abundances, reliable Mo iv-vii oscillator strengths are used. Methods: We newly calculated Mo iv-vii oscillator strengths to consider their radiative and collisional bound-bound transitions indetail in our NLTE stellar-atmosphere models for the analysis of Mo lines exhibited in high-resolution and high SN UV observations of RE 0503289.Results. We identified 12 Mo v and nine Mo vi lines in the UV spectrum of RE 0503289 and measured a photospheric Mo abundance of 1.2 3.0 104(mass fraction, 22 500 56 400 times the solar abundance). In addition, from the As v and Sn iv resonance lines,we measured mass fractions of arsenic (0.51.3 105, about 300 1200 times solar) and tin (1.33.2 104, about 14 300 35 200 times solar). For G191B2B, upper limits were determined for the abundances of Mo (5.3 107, 100 times solar) and, in addition, for Kr (1.1106, 10 times solar) and Xe (1.7107, 10 times solar). The arsenic abundance was determined (2.35.9 107, about 21 53 times solar). A new, registered German Astrophysical Virtual Observatory (GAVO) service, TOSS, has been constructed to provide weighted oscillator strengths and transition probabilities.Conclusions. Reliable measurements and calculations of atomic data are a prerequisite for stellar-atmosphere modeling. Observed Mo v-vi line profiles in the UV spectrum of the white dwarf RE 0503289 were well reproduced with our newly calculated oscillator strengths. For the first time, this allowed the photospheric Mo abundance in a white dwarf to be determined.

Rauch, T.↗
NASA NTRS1981

On the origin and distribution of C IV and Si IV ions in the neighboring interstellar medium

IUE spectrometer observational data are reported on the C IV, Si IV, and N V absorption lines in 46 distant stars at FWHM resolution of 30 km/sec. A simple analytic theory is given for these contributions, including the effects of ionization by a soft X-ray background. While for some of the most distant field stars a photoionized contribution may be ruled out, C IV absorption lines are detected which are shallow and broad. It is suggested that what are being detected in these cases are contributions from the hot interstellar gas that is responsible for the O VI absorption lines. Most of the Si IV and C IV lines probably arise in the H II regions surrounding the observed star or its neighbors.

Cowie, L. L.↗
NASA NTRS1987

The moderately interacting Algol-type eclipsing binary RY Geminorum

Ultraviolet spectra of the Algol-type semidetached system RY Geminorum, whose components can be described as A0 V and K0 IV, have been matched to the ultraviolet spectrum by Kurucz (1979) model atmospheres, and a best fit is found for T(eff) = 9150 K. Comparison with standard star spectra requires that this value be raised to 9400 K. The color excess of the system is determined to be no more than E(B-V) = 0.03 mag; the distance to the system is about 360 pc. The masses are approximately 2.36 and 0.38 solar masses, and the radii are 2.5 and 5.8 solar radii, respectively. The separation of the two centers is 26 solar radii. Evidence for a circumstellar line absorption is found in optical and ultraviolet spectrograms, and evidence is found in IUE spectra taken in partial eclipse for circumstellar emission lines of the type detected previously in the WS Serpentis stars and in several semidetected systems of the Algol type.

Plavec, Mirek J.↗
NASA NTRS1992

Spectral synthesis in the ultraviolet. IV - A library of mean stellar groups

A library of mean UV stellar energy distributions is derived from IUE spectrophotometry of 218 stars. The spectra cover 1230-3200 A with a spectral resolution of about 6 A. They have been corrected for interstellar extinction and converted to a common flux and wavelength scale. Individual stars were combined into standard groups according to their continuum colors, observed UV spectral morphology, MK luminosity class, and metal abundance. The library consists of 56 groups: 21 dwarf(V), 8 subgiant(IV), 16 giant(III), and supergiant(I + II) groups, covering O3-M4 spectral types. A metal-poor sequence is included, containing four dwarf and two giant groups, as is a metal-enhanced sequence with a single dwarf, subgiant, and giant group. Spectral indices characterizing the continuum and several strong absorption features are examined as temperature, luminosity, and abundance diagnostics. The library is intended to serve as a basis for interpreting the composite UV spectra of a wide variety of stellar systems, e.g., elliptical galaxies, starburst systems, and high-redshift galaxies.

Fanelli, Michael N.↗
DOE OSTI2021

Amidinate Supporting Ligands Influence Molecularity in Formation of Uranium Nitrides

Uranium nitride complexes are attractive targets for chemists as molecular models for the bonding, reactivity, and magnetic properties of next-generation nuclear fuels, but these molecules are uncommon and can be difficult to isolate due to their high reactivity. Here, we describe the synthesis of three new multinuclear uranium nitride complexes, [U(BCMA) 2 ] 2 (μ-N)(μ-κ 1 :κ 1 -BCMA) (7), [(U(BIMA) 2 ) 2 (μ-N)(μ-N i Pr)(K 2 (μ-η 3 :η 3 -CH 2 CHN i Pr)] 2 (8), and [U(BIMA) 2 ] 2 (μ-N)(μ-κ 1 :κ 1 -BIMA) (9) (BCMA = N,N-bis(cyclohexyl)methylamidinate, BIMA = N,N-bis(iso-propyl)methylamidinate), from U(III) and U(IV) amidinate precursors. By varying the amidinate ligand substituents and azide source, we were able to influence the composition and size of these nitride complexes. 15 N isotopic labeling experiments confirmed the bridging nitride moieties in 7–9 were formed via two-electron reduction of azide. The tetra-uranium cluster 8 was isolated in 99% yield via reductive cleavage of the amidinate ligands; this unusual molecule contains nitrogen-based ligands with formal 1–, 2–, and 3– charges. Additionally, chemical oxidation of the U(IV) precursor U(N 3 )(BCMA) 3 yielded the cationic U(V) species [U(N 3 )(BCMA) 3 ][OTf]. Magnetic susceptibility measurements confirmed a U(IV) oxidation state for the uranium centers in the three nitride-bridged complexes and provided a comparison of magnetic behavior in the structurally related U(III)-U(IV)-U(V) series U(BCMA) 3 , U(N 3 )(BCMA) 3 , and [U(N 3 )(BCMA) 3 ][OTf]. At 240 K, the magnetic moments in this series decreased with increasing oxidation state, i.e., U(III) > U(IV) > U(V); this trend follows the decreasing number of 5f valence electrons along this series.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Multiple oxidation states of uranium stabilized by an O , N , O -ligand

Elements of the 5f row maintain a wide variety of oxidation states that have been exploited in synthesis, catalysis, and separations. Herein, we describe the complexation of an O,N,O chelator, ExPh, with uranium in the (IV) and (VI) (uranyl) oxidation states. These two uranium complexes, U(IV)ExPh and UO 2 ExPh, respectively, were characterized in the solid state via single-crystal X-ray diffraction (SC-XRD) analysis. Electrochemical studies using cyclic voltammetry were employed to investigate the multiple redox events associated with the U(IV) complex. Spectro-electrochemical analysis of U(IV)ExPh provided spectroscopic evidence of a stable U(V) species. Chemical oxidation of U(IV)ExPh allowed isolation of the U(V) complex, U(V)ExPh. All three stable uranium complexes produced in this study were characterized via IR, UV-vis and NMR spectroscopies, and micro-spectrophotometry. On the other hand, efforts to reduce U(IV)ExPh to the corresponding U(III) species or produce this putative complex directly from ExPh failed to yield an isolable product. The stabilization of three formal oxidation states of uranium, coupled with previous lanthanide-row results, paves the way for studies of ExPh and its analogues in minor actinide chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Chromospheres and coronae in the T Tauri stars

The Tauri stars exhibit strong far ultraviolet emission lines of C II, III, IV; OI; Si II, III; IV; and sometimes N V and He II. Surface fluxes of the lines for several T Tauri stars were computed, drawing upon both International Ultraviolet Explorer observations and published spectra. The surface fluxes are quite high. The FUV lines together account for 0.1% of the stellar luminosity. These results indicate the presence of active relatively dense chromospheres. The Tauri stars showing very strong visual emission spectra exhibit weakened high temperature FUV lines of C IV and N V, as well as He II which may be produced by X-rays. In the same stars, no X-ray emission was detected with Einstein. Among all the T Tauri stars the X-ray luminosities are deficient by factors of 100 to 1000 compared to the FUV lines. It is argued that the X-ray flux has not been heavily absorbed by circumstellar gas, as has been previously suggested, but that the X-rays are truly underluminous, perhaps due to the stellar wind. It is suggested that the birth and development of the chromosphere and corona may be occurring during the T Tauri stage of protostellar evolution.

Imhoff, C. L.↗
NASA NTRS1994

X-ray planetary nebulae

A study of IUE archival low-dispersion spectra was conducted in an attempt to correlate the C IV/He II and C III)/C IV emission line ratios as indicators of X-ray emission in planetary nebulae. The presence of P Cygni lines revealed a strong correlation for planetaries known to exhibit X-ray emission. Of the twelve planetaries definitely known to emit X-rays, eleven have been observed with IUE and all but one show ultraviolet lines with very strong P Cygni profiles for at least one, and sometimes all, of the N V, O V, or C IV lines which are indicative of strong stellar winds. Twenty planetary nebulae are identified as likely candidates for X-ray sources, based on their high IUE emission line flux ratios for C IV/He II as well as prevalence of P Cygni lines. Some misconceptions based on outdated IUE data are corrected.

Feibelman, Walter A.↗
NASA NTRS1984

HRTS II EUV observations of a solar ephemeral region

HRTS II has been used to observe the EUV emission of a small bipolar magnetic feature or ephemeral region, where strong EUV line enhancement exhibits contrasts (measured relative to the quiet sun) which range from 10 to 70. The substantiality of the Lyman-alpha and C II-O V emission, and the absence of any measurable emission in coronal forbidden lines, sets a temperature range for the loop's active part of the order of 16,000-300,000 K. The use of the ratios of allowed lines as temperature diagnostics yields temperatures that are very near ionization equilibrium temperatures, and the use of chromospheric lines to form a wavelength standard yields absolute velocities ranging in magnitude from zero to 12 km/sec for C IV, N IV, and O V. This flow is interpreted as a siphon flow.

Roussel-Dupre, R.↗
NASA NTRS2012

ELaNa - Educational Launch of Nanosatellite Providing Routine RideShare Opportunities

Since the creation of the NASA CubeSat Launch Initiative (NCSLI), the need for CubeSat rideshares has dramatically increased. After only three releases of the initiative, a total of 66 CubeSats now await launch opportunities. So, how is this challenge being resolved? NASA's Launch Services Program (LSP) has studied how to integrate PPODs on Athena, Atlas V, and Delta IV launch vehicles and has been instrumental in developing several carrier systems to support CubeSats as rideshares on NASA missions. In support of the first two ELaNa missions the Poly-Picosatellite Orbital Deployer (P-POD) was adapted for use on a Taurus XL (ELaNa I) and a Delta n (ELaNa III). Four P-PODs, which contained a total eight CubeSats, were used on these first ELaNa missions. Next up is ELaNa VI, which will launch on an Atlas V in August 2012. The four ELaNa VI CubeSats, in three P-PODs, are awaiting launch, having been integrated in the NPSCuLite. To increase rideshare capabilities, the Launch Services Program (LSP) is working to integrate P-PODs on Falcon 9 missions. The proposed Falcon 9 manifest will provide greater opportunities for the CubeSat community. For years, the standard CubeSat size was 1 U to 3U. As the desire to include more science in each cube grows, so does the standard CubeSat size. No longer is a 1 U, 1.5U, 2U or 3U CubeSat the only option available; the new CubeSat standard will include 6U and possibly even 12U. With each increase in CubeSat size, the CubeSat community is pushing the capability of the current P-POD design. Not only is the carrier system affected, but integration to the Launch Vehicle is also a concern. The development of a system to accommodate not only the 3U P-POD but also carriers for larger CubeSats is ongoing. LSP considers payloads in the lkg to 180 kg range rideshare or small/secondary payloads. As new and emerging small payloads are developed, rideshare opportunities and carrier systems need to be identified and secured. The development of a rideshare carrier system is not always cost effective. Sometimes a launch vehicle with an excellent performance record appears to be a great rideshare candidate however, after completing a feasibility study, LSP may determine that the cost of the rideshare carrier system is too great and, due to budget constraints, the development cannot go forward. With the current budget environment, one cost effective way to secure rideshare opportunities is to look for synergy with other government organizations that share the same interest.

Skrobot, Garrett Lee↗
NASA NTRS1985

Photoionization models for the wind from TW Vir

Line profiles are examined for the resonance doublets of the ions C IV, Si IV, and N V in the spectrum of the dwarf nova TW Virginis as observed by Cordova and Mason (1982). Line strengths depend on the abundances of the scattering ions and hence on the physical characteristics in the stellar wind. Results of the study show that the observed UV line ratios from TW Vir cannot be produced by photoionization by either an unattenuated single bremsstrahlung or by a single blackbody spectrum. Satisfactory values of the abundance ratios can be produced by bremsstrahlung spectra extending into the X-ray region which have low-energy cutoffs near the N IV threshold energy at 77 eV and have fluxes corresponding to an ionization parameter xi-sub-br of about 10. A finding that the flux in the soft X-ray bremsstrahlung component must exceed the EUV blackbody flux by at least an order of magnitude has implications for theories of the continuum emission from cataclysmic variables.

Kallman, T.↗
NASA NTRS1987

Rapid variability of P Cygni lines in massive X-ray binaries

In early-type X-ray binaries, the recombination time scales for ions such as C IV, Si IV, and N V in the stellar winds of their massive OB companion stars can be very short compared to typical X-ray pulsation or fluctuation time scales. Thus, the authors predict that the 'bleached zones', in which these ions are removed from the stellar wind by X-ray photoionization, will track the X-ray beam as it rotates and that the P Cygni line profiles due to these ions will pulsate. With the IUE satellite the authors obtained low-resolution UV spectra of the binary X-ray system HD 77581/4U 0900-40 resolved into six phase bins of the 283 s pulse period; the observed upper limit to the pulse amplitude of the equivalent width of C IV 1550 A was less than the predicted value. However, the pulsations should be easy to observe with the Hubble Space Telescope.

Kallman, Timothy R.↗
NASA NTRS2002

A Multi-Wavelength Study of the Hot Component of the Interstellar Medium

The goals of this research are as follows: (1) Using the large number of lines of sight available in the ME database, identify the lines of sight with high-velocity components in interstellar lines, from neutral species through Si VI, C IV, and N V; (2) Compare the column density of the main components (i.e. low velocity components) of the interstellar lines with distance, galactic longitude and latitude, and galactic radial position. Derive statistics on the distribution of components in space (e.g. mean free path, mean column density of a component). Compare with model predictions for the column densities in the walls of old SNR bubbles and superbubbles, in evaporating cloud boundaries and in turbulent mixing layers; (3) For the lines of sight associated with multiple high velocity, high ionization components, model the shock parameters for the associated superbubble and SNR to provide more accurate energy input information for hot phase models and galactic halo models. Thus far 49 lines of sight with at least one high velocity component to the C IV lines have been identified; and (4) Obtain higher resolution data for the lines of sight with high velocity components (and a few without) to further refine these models.

Nichols, Joy↗
DOE OSTI2020

Mineral-specific heterogeneous neptunium sorption onto geological repository rocks in oxic and anoxic conditions and various temperatures

Neptunium poses challenges for radioactive wastes management due to its long half-life and ingrowth from americium decay, as well as its high mobility in water in its oxidized forms. Np(V)-bearing aqueous solutions were contacted with polished and crushed gneiss and dolerite from the Yeniseisky site, Russia, which is under consideration as a location for an underground repository, both in oxic and anoxic conditions at 20 and 90 °C. Neptunium sorption on crushed gneiss and dolerite in oxic conditions at 20 °C was quite low, but increased substantially in anoxic conditions. Autoradiography on samples treated at 20 °C revealed that sorbed Np was associated mostly with dark colored iron-bearing minerals, and solvent extraction indicated partial reduction of Np(V) to Np(IV). Sorption of Np from aqueous solutions contacted with dolerite and gneiss at 90 °C was in all cases higher than at the lower temperature. Autoradiography of polished rock samples treated in anoxic conditions at 90 °C revealed that Fe-bearing minerals had 3–4 orders of magnitude more Np sorbed on them than the quartz and feldspar grains. X-ray photoelectron spectroscopy indicated this sorbed Np was present as NpO 2 . This study supports the concept that the geologic conditions present at the planned repository site will retard Np migration.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1993

31 Cygni: The B star and the wind

I have followed photospheric and wind absorptions in International Ultraviolet Explorer (IUE) spectra over much of the orbit of this K4 Ib+B3-4 binary system, using interstellar lines to transform all the velocities to a scale with the interstellar medium at -10.1 km/s. Results are as follows: Interstellar Fe II lines give NL (Fe(+)) = 1-2 x 10(exp 14)/sq cm with a Doppler width of 7 km/s; depletions of heavy elements along the line of sight to this star are similar to those for other stars with low interstellar densities. Photospheric lines yield a new velocity amplitude for the B star, K(sub B) = 23.2 +/- 1.0 km/s, which gives the mass ratio M(sub K)/M(sub B) = 1.66 and masses M(sub B) = 7.1 solar mass and M(sub K) = 11.7 solar mass. Existing photometry gives R(sub K) = 197 solar radius, R(sub B) = 5.2 solar radius, and i = 87.19 deg. Breadths of photospheric lines imply the rotational velocity of the B star is V sin i = 70-80 km/s. Most of the wind features are formed in a shell much larger than the binary system for which the terminal velocity seems to be 73 +/- 2 km/s, but it may be as high as approximately 90 km/s. The Doppler width (approximately 13 km/s) of Fe II shell lines likely results from acceleration of the wind, although it could reflect orbital motion of the K supergiant. Shell lines of Mg II and Si II are roughly consistent with Fe II, although their strengths are phase dependent, while S II requires a somewhat thicker shell in S(+) than in Fe(+) with a greater spread in expansion velocity. Shell lines of O I and N I are abnormally weak, if detected at all, and this implies that hydrogen is ionized throughout much of the wind. Lines of highly ionized species (C IV, Si Iv, and N V) appear sporadically in the spectrum and have inverse P Cyg profiles implying collapse (probably of an accretion disk) onto the B star. They do not seem to be isolated at particular phases as might be expected for formation in a conical shock front around an accretion column. I argue that the wind is roughly isotopic and is accelerated slowly, in agreement with existing ideas about winds.

Eaton, Joel A.↗
NASA NTRS2012

Space Transportation Infrastructure Supported By Propellant Depots

A space transportation infrastructure is described that utilizes propellant depot servicing platforms to support all foreseeable missions in the Earth-Moon vicinity and deep space out to Mars. The infrastructure utilizes current expendable launch vehicle (ELV) systems such as the Delta IV Heavy, Atlas V, and Falcon 9, for all crew, cargo, and propellant launches to orbit. Propellant launches are made to Low-Earth-Orbit (LEO) Depot and an Earth-Moon Lagrange Point 1 (L1) Depot to support a new reusable in-space transportation vehicles. The LEO Depot supports missions to Geosynchronous Earth Orbit (GEO) for satellite servicing and to L1 for L1 Depot missions. The L1 Depot supports Lunar, Earth-Sun L2 (ESL2), Asteroid and Mars Missions. New vehicle design concepts are presented that can be launched on current 5 meter diameter ELV systems. These new reusable vehicle concepts include a Crew Transfer Vehicle (CTV) for crew transportation between the LEO Depot, L1 Depot and missions beyond L1; a new reusable lunar lander for crew transportation between the L1 Depot and the lunar surface; and Mars orbital Depot are based on International Space Station (ISS) heritage hardware. Data provided includes the number of launches required for each mission utilizing current ELV systems (Delta IV Heavy or equivalent) and the approximate vehicle masses and propellant requirements. Also included is a discussion on affordability with ideas on technologies that could reduce the number of launches required and thoughts on how this infrastructure include competitive bidding for ELV flights and propellant services, developments of new reusable in-space vehicles and development of a multiuse infrastructure that can support many government and commercial missions simultaneously.

Smitherman, David↗
NASA NTRS1989

An interpretation of the line profile variations in the IUE spectrum of the Wolf-Rayet binary Gamma(2) Velorum

An analysis of the variable profiles of the high-temperature resonance lines of Si IV in the IUE spectrum of gamma(2) Vel has made it possible to describe these profiles as a superposition of two different profiles, namely, a P Cygni profile that remains practically stationary throughout the orbital cycle and an absorption profile that moves back and forth with phase. To these two profiles is added a very sharp, strong absorption that ought to arise in the layers of the extended gaseous envelope that merge with the interstellar medium. The absorption that moves back and forth during the system's orbital revolution has been interpreted as suggesting a stream going away from the system at an angle of some 110 deg from the direction of the radius vector joining the Wolf-Rayet star with its companion. Such a stream seems to project upon a dense concentration of matter that is located somewhere in the volume between the two stars and moves away at some -700 km/s, and should result from the collision of the winds from the two components. The high-temperature resonance lines of N V and C IV very likely behave similarly to Si IV.

Brandi, Estela↗