Heat transfer to throat tubes in a square-chambered rocket engine at the NASA Lewis Research Center

A gaseous H2/O2 rocket engine was constructed at the NASA-Lewis to provide a high heat flux source representative of the heat flux to the blades in the high pressure fuel turbopump (HPFTP) during startup of the space shuttle main engines. The high heat flux source was required to evaluate the durability of thermal barrier coatings being investigated for use on these blades. The heat transfer, and specifically, the heat flux to tubes located at the throat of the test rocket engine was evaluated and compared to the heat flux to the blades in the HPFTP during engine startup. Gas temperatures, pressures and heat transfer coefficients in the test rocket engine were measured. Near surface metal temperatures below thin thermal barrier coatings were also measured at various angular orientations around the throat tube to indicate the angular dependence of the heat transfer coefficients. A finite difference model for a throat tube was developed and a thermal analysis was performed using the measured gas temperatures and the derived heat transfer coefficients to predict metal temperatures in the tube. Near surface metal temperatures of an uncoated throat tube were measured at the stagnation point and showed good agreement with temperatures predicted by the thermal model. The maximum heat flux to the throat tube was calculated and compared to that predicted for the leading edge of an HPFTP blade. It is shown that the heat flux to an uncooled throat tube is slightly greater than the heat flux to an HPFTP blade during engine startup

Role of the methylene amidogen (H2CN) radical in the atmospheres of Titan and Jupiter

The methylene amidogen (H2CN) radical can be shown to be an important intermediate in models for the formation of HCN (via N + CH3) and the recombination of H to H2 (via H + HCN) on Titan as well as in models for the formation of HCN (via NH2 + C2H3) in the atmosphere of Jupiter. Experiments in our laboratory in a discharge flow system with mass spectrometric detection of both reactants and products have established that the major product channel (90 percent for the reaction N + CH3 is that leading to H2CN + H. The same result was obtained for N + CD3 yields D2CN + D. The rate constant for the reaction D + D2CN yields DCN + D2 was measured for the first time and k(298 K) greater than 7 x 10(exp -11) cu cm/s was found. The same result was obtained for the H atom reaction. This is the final step in the reaction sequence leading to HCN on both Titan and Jupiter and to formation of H2 from H on Titan. The first measurement of the ionization potentials for H2CN and D2CN was also made. From electron impact studies I.P. = (9.6 + or - 1.0) eV was obtained for both radicals. An upperlimit of I.P. less than 11.6 eV came from observations of the H2CN radical by photoionization mass spectrometry using an Ar resonance lamp (106.7 nm). Further photoionization experiments are planned using synchrotron radiation plus monochromator as a tunable vacuum UV light source

Stabilization and precise calibration of a continuous-wave difference frequency spectrometer by use of a simple transfer cavity

A novel, simple, and inexpensive calibration scheme for a continuous-wave difference frequency spectrometer is presented, based on the stabilization of an open transfer cavity by locking onto the output of a polarization stabilized HeNe laser. High frequency, acoustic fluctuations of the transfer cavity length are compensated with a piezoelectric transducer mounted mirror, while long term drift in cavity length is controlled by thermal feedback. A single mode Ar+ laser, used with a single mode ring dye laser in the difference frequency generation of 2–4 µm light, is then locked onto a suitable fringe of this stable cavity, achieving a very small long term drift and furthermore reducing the free running Ar+ linewidth to about 1 MHz. The dye laser scan provides tunability in the difference frequency mixing process, and is calibrated by marker fringes with the same stable cavity. Due to the absolute stability of the marker cavity, precise frequency determination of near infrared molecular transitions is achieved via interpolation between these marker fringes. It is shown theoretically that the residual error of this scheme due to the dispersion of air in the transfer cavity is quite small, and experimentally that a frequency precision on the order of 1 MHz per hour is routinely obtained with respect to molecular transitions. Review of Scientific Instruments is copyrighted by The American Institute of Physics

Program evaluation of the community aftercare program, Canadian Mental Health Association Waterloo region

This paper describes an evaluation of the Community Aftercare Program, a program of the Canadian Mental Health Association, Waterloo Region. This case management program offers long-term support to psychiatrically disabled adults who were once hospitalized and now live in this community. Ten people from the Community Aftercare Program and ten individuals who were on the waiting list for the program were interviewed for this static group comparison design. Using a stakeholder approach, data were collected on measures of hospitalization, adaptive functioning, community integration, social support networks, employment, housing, service use, and quality of life. Results indicated that the program clients had fewer days of hospitalization after entering the program. They also had a better quality of housing, felt better about their housing, and were more satisfied with the way they spend their spare time than the waiting list group. Qualitative data suggested that there was less variability in functioning of the program clients are compared to people on the waiting list. Limitations of the waiting list as a comparison group and recommendations for future evaluations are discussed

Beyond the Born-Oppenheimer approximation: high-resolution overtone spectroscopy of H2D+ and D2H+

Transitions to overtone 2v2 and 2v3, and combination v2 + v3 vibrations in jet-cooled H2D+ and D2H+ molecular ions have been measured for the first time by high-resolution IR spectroscopy. The source of these ions is a pulsed slit jet supersonic discharge, which allows for efficient generation, rotational cooling, and high frequency (100 KHz) concentration modulation for detection via sensitive lock-in detection methods. Isotopic substitution and high-resolution overtone spectroscopy in this fundamental molecular ion permit a systematic, first principles investigation of Born–Oppenheimer "breakdown" effects due to large amplitude vibrational motion as well as provide rigorous tests of approximate theoretical methods beyond the Born–Oppenheimer level. The observed overtone transitions are in remarkably good agreement (<0.1 cm–1) with non-Born–Oppenheimer ab initio theoretical predictions, with small but systematic deviations for 2v2, 2v + 3v, and 2v3 excited states indicating directions for further improvement in such treatments. Spectroscopic assignment and analysis of the isotopomeric transitions reveals strong Coriolis mixing between near resonant 2v3 and 2v + 3v vibrations in D2H+. Population-independent line intensity ratios for transitions from common lower states indicate excellent overall agreement with theoretical predictions for D2H+, but with statistically significant discrepancies noted for H2D+. Finally, H2D+ versus D2H+ isotopomer populations are analyzed as a function of D2/H2 mixing ratio and can be well described by steady state kinetics in the slit discharge expansion

Solute transport during the cyclic oxidation of Ni-Cr-Al alloys

Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered

Overlay coating degradation by simultaneous oxidation and coating/substrate interdiffusion

Degradation of NiCrAlZr overlay coatings on various NiCrAl substrates was examined after cyclic oxidation. Concentration/distance profiles were measured in the coating and substrate after various oxidation exposures at 1150 C. For each stubstrate, the Al content in the coating decreased rapidly. The concentration/distance profiles, and particularly that for Al, reflected the oxide spalling resistance of each coated substrate. A numerical model was developed to simulate diffusion associated with overlay-coating degradation by oxidation and coating/substrate interdiffusion. Input to the numerical model consisted of the Cr and Al content of the coating and substrate, ternary diffusivities, and various oxide spalling parameters. The model predicts the Cr and Al concentrations in the coating and substrate after any number of oxidation/thermal cycles. The numerical model also predicts coating failure based on the ability of the coating to supply sufficient Al to the oxide scale. The validity of the model was confirmed by comparison of the predicted and measured concentration/distance profiles. The model was subsequently used to identify the most critical system parameters affecting coating life

What makes you not a Sikh? : a preliminary mapping of values

This study sets out to establish which Sikh values contrasted with or were shared by non-Sikh adolescents. A survey of attitude toward a variety of Sikh values was fielded in a sample of 364 non-Sikh schoolchildren aged between 13 and 15 in London. Values where attitudes were least positive concerned Sikh duties/code of conduct, festivals, rituals, prayer Gurdwara attendance, listening to scripture recitation, the amrit initiation. Sikh values empathized with by non-Sikhs concerned family pride, charity, easy access to ordination and Gurdwaras, maintaining the five Ks, seeing God in all things, abstaining from meat and alcohol and belief in the stories of Guru Nanak. Further significant differences of attitude toward Sikhism were found in comparisons by sex, age and religious affiliation. Findings are applied to teaching Sikhism to pupils of no faith adherence. The study recommends the extension of values mapping to specifically Sikh populations