Impingement effect of service module reaction control system engine plumes. Results of service module reaction control system plume model force field application to an inflight Skylab mission proximity operation situation with the inflight Skylab response

Plume impingement effects of the service module reaction control system thruster firings were studied to determine if previous flight experience would support the current plume impingement model for the orbiter reaction control system engines. The orbiter reaction control system is used for rotational and translational maneuvers such as those required during rendezvous, braking, docking, and station keeping. Therefore, an understanding of the characteristics and effects of the plume force fields generated by the reaction control system thruster firings were examined to develop the procedures for orbiter/payload proximity operations

Apollo experience report: Flight anomaly resolution

The identification of flight anomalies, the determination of their causes, and the approaches taken for corrective action are described. Interrelationships of the broad range of disciplines involved with the complex systems and the team concept employed to ensure timely and accurate resolution of anomalies are discussed. The documentation techniques and the techniques for management of anomaly resolution are included. Examples of specific anomalies are presented in the original form of their progressive documentation. Flight anomaly resolution functioned as a part of the real-time mission support and postflight testing, and results were included in the postflight documentation

On the Lagrangian structure of 3D consistent systems of asymmetric quad-equations

Recently, the first-named author gave a classification of 3D consistent 6-tuples of quad-equations with the tetrahedron property; several novel asymmetric 6-tuples have been found. Due to 3D consistency, these 6-tuples can be extended to discrete integrable systems on Z^m. We establish Lagrangian structures and flip-invariance of the action functional for the class of discrete integrable systems involving equations for which some of the biquadratics are non-degenerate and some are degenerate. This class covers, among others, some of the above mentioned novel systems.Comment: 21 pp, pdfLaTe

An integrable multicomponent quad equation and its Lagrangian formulation

We present a hierarchy of discrete systems whose first members are the lattice modified Korteweg-de Vries equation, and the lattice modified Boussinesq equation. The N-th member in the hierarchy is an N-component system defined on an elementary plaquette in the 2-dimensional lattice. The system is multidimensionally consistent and a Lagrangian which respects this feature, i.e., which has the desirable closure property, is obtained.Comment: 10 page

Probing the limits of superconductivity

DC voltage versus current measurements of superconductors in a magnetic field are widely interpreted to imply that a phase transition occurs into a state of zero resistance. We show that the widely-used scaling function approach has a problem: Good data collapse occurs for a wide range of critical exponents and temperatures. This strongly suggests that agreement with scaling alone does not prove the existence of the phase transition. We discuss a criterion to determine if the scaling analysis is valid, and find that all of the data in the literature that we have analyzed fail to meet this criterion. Our data on YBCO films, and other data that we have analyzed, are more consistent with the occurrence of small but non-zero resistance at low temperature.Comment: 13 page pdf file, figures included To be published in conference proceedings of SPIE 200

Normal-Superconducting Phase Transition Mimicked by Current Noise

As a superconductor goes from the normal state into the superconducting state, the voltage vs. current characteristics at low currents change from linear to non-linear. We show theoretically and experimentally that the addition of current noise to non-linear voltage vs. current curves will create ohmic behavior. Ohmic response at low currents for temperatures below the critical temperature $T_c$ mimics the phase transition and leads to incorrect values for $T_c$ and the critical exponents $\nu$ and $z$. The ohmic response occurs at low currents, when the applied current $I_0$ is smaller than the width of the probability distribution $\sigma_I$, and will occur in both the zero-field transition and the vortex-glass transition. Our results indicate that the transition temperature and critical exponents extracted from the conventional scaling analysis are inaccurate if current noise is not filtered out. This is a possible explanation for the wide range of critical exponents found in the literature.Comment: 4 pages, 2 figure

Effects of Self-field and Low Magnetic Fields on the Normal-Superconducting Phase Transition

Researchers have studied the normal-superconducting phase transition in the high-$T_c$ cuprates in a magnetic field (the vortex-glass or Bose-glass transition) and in zero field. Often, transport measurements in "zero field" are taken in the Earth's ambient field or in the remnant field of a magnet. We show that fields as small as the Earth's field will alter the shape of the current vs. voltage curves and will result in inaccurate values for the critical temperature $T_c$ and the critical exponents $\nu$ and $z$, and can even destroy the phase transition. This indicates that without proper screening of the magnetic field it is impossible to determine the true zero-field critical parameters, making correct scaling and other data analysis impossible. We also show, theoretically and experimentally, that the self-field generated by the current flowing in the sample has no effect on the current vs. voltage isotherms.Comment: 4 pages, 4 figure