Kinetics of formation and decay of Cz produced by passing shock waves through dilute C2H2+Ar mixtures were studied at temperatures in the range 4860-6920 K. The kinetics of formation of Cz were in essential agreement with a postulated simple two-step dissociation of CzH2 by Ar. The rate constant for the dissociation of Ct by Ar was found to be ~c ~, A ~ = *'.'') exp( -583. &59 kJ mol-'/RT) cm3 molecufe-l s-l.The diatomic molecule of carbon, C 2 , is well known to be a product of the high temperature pyrolysis of simple organic molecules.1 The reactions of this species are important in many areas of high temperature chemistry.2 In an investigation of negative ion formation from carbon we have found that a proper kinetic treatment of C , formation necessitates an understanding of the rates and mechanism of C2 formation and dissociation.Acetylene is a usual initial reagent for Cz. The pyrolysis of acetone has been much studied at considerably lower temperatures than those at which C2 appreciably di~sociates.~-~ In these low temperature studies (< 2500 K) the importance of polymer intermediates has been demonstrated.* At sufficiently high temperatures ( > 4800 K) and at high dilutions in argon the formation and decay of C , from acetylene should be considerably simplified. Polymer products, at least at equilibrium, are negligible at these temperatures. There has been only one prior report of an attempt to measure the rate of dissociation of C2. Fairbairn' investigated the pyrolysis of several organic molecules at temperatures above 5000 K, but concluded that the observed decay of C2 somehow was coupled to the overall decomposition rate of the initial reagent. We report the kinetics of formation and dissociation of C2 in dilute mixtures of acetylene with argon. EXPERIMENTALThe high temperature pyrolysis of dilute mixtures of acetylene with argon was studied by passing a shock wave through the gas. The basic details of the shock tube have been described previously.lo All observations behind the incident shack were carried out 2.95 m from the diaphragm, giving a usable flow time of between 150-200~s (laboratory time). The emission spectrum of the Cz Swan system arising from the shock-heated gas was monitored by a Hamamatsu R213 photomultiplier at the exit slit of a Hilger and Watts monochromator. The voltage signaI from the photomultiplier was displayed on a storage oscilloscope. The monochromator was set at 514 nm and had a spectral bandpass of 1.0 nm. Initial photographic recording using a time-resolved spectrograph3 indicated that the emission at 514 nm arose only from Cz. By means of two narrow slits in the optical path, optical time resolution of better than 0.3 p s was achieved.C.I.G. special high purity acetylene and argon were used without further purification.

In recent years a renaissance of diffusion bonding can be observed. Beside applications in the aerospace industry more and more industrial users take advantage of the solid state joining process. The progressive development of micro technologies results from the systematic miniaturization efforts for electrical, optical and mechanical components. A major role for this is taken by the application of scale effects. Today, micro structured-components are already deployed in telecommunication, mechanical engineering, medicine-and biotechnology.During this continuous top-down process the performance of a component should at least be equal or rather enhanced as compared to the conventional processed part. Increasing computational power needs a safely controlled and managed heat generation and distribution in any of such components. This is not only important for electronic devices, but also for tools used for micro injection molding. With the combination of machining or laser cutting and subsequent diffusion bonding it is possible to freely design and manufacture the required parts with an inside structure. In this paper an enhanced process chain for production of parts by a lamination technology, which is capable to solve scale restrictions, is presented as well as application examples and process specific features, Fig. 1.

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An overview of the development and implementation of spectroscopic diagnostic techniques for high enthalpy facilities (with examples from HEG) is given. Spectrally and spatially resolved results with NO LIF at 193 nm on HEG are given for the free stream and for various models (European HERMES, Japanese HOPE, aerobraking configuration, cylinder, and sphere). The problems of luminosity, fluorescence quenching, nonlinear effects, and corrections needed for single-shot measurements are discussed with reference to the HEG results and to extensive tests carried out on a specially designed heated cell capable of providing controlled NO conditions in a flow system. Other spectroscopic techniques such as emission spectroscopy, tunable diode laser absorption, and flash lamp absorption are referred to briefly.

Funded by the European Space Agency (ESA), the Ariane 5 Program has been developed under the responsibility of the CNES, the French Space Agency. Attitude Control of the Ariane 5 Mission is carried out by the SCA (Systeme Controle d'Attitude), developed by Astrium‐Space Transportation (Astrium‐ST). It is the blow down hydrazine system using gaseous nitrogen as pressurant. The ARIANE 5 ‐SCA Tank ‐ Fig.1 ‐ is manufactured from TiAl6V4‐hemispheres essentially performed via Super Plastic Forming (SPF) process. The tank shell wall thickness achieved need not to be mechanically reworked except small domains prepared for welding. Vis‐à‐vis the common tank production which employs hemispheres resulted by mechanical milling out of forged shell, the SPF provides certainly saving on milling efforts as well as significant reduction on material wasting. Also shown that is for tank component submitted to space application, the SPF as production method commonly undergoes development and verification efforts in engineering elaborating focused on Test‐shell, Qualification‐shell and such which provides samples for material strength and technological verifications. Enclosing is also a brief overall display addressing successful use of SPF‐shell in producing tanks for the space flight today. Up to now more then 100 Tanks have been manufactured by Astrium‐ST and > 90 Tanks were successful used in Ariane 5 launchers with various missions.