A fully ionized plasma is assumed. To this plasma cylindrically-symmetric magnetic fields are applied, thus causing a pinch collapse. The plasma is treated in hydromagnetic approximation, including electric and thermal conductivity. Separate temperatures are assigned to the electrons and ions.Two schemes are developed for solving numerically the resulting system of six partial differential equations: the explicit scheme for rather fast pinches, where a numerical stability requirement causes the timestep to be bounded by the characteristics given by the ALFVEN speed, and an implicit scheme, which consists essentially in converting the momentum equation into a second order difference equation with coefficients determined by iteration; here there is no such restriction on the timestep. These schemes were made to work on the U.K.A.E.A. IBM 704 and IBM 709.A run is described in which the initial state was one with uniform density, temperature and B z field. The boundary temperatures were assumed to remain constant, while the magnetic fields at the boundary were determined by the circuits for the j z and currents. The results of the computations are in good agreement with experimental results obtained at the Technische Hochschule Mün-chen by one of the authors (KÖPPENDÖRFER) .The whole program is a joint effort between A.E.R.E. Harwell and the Max-Planck-Institut, intended to discover by comparison with experiments how good the hydromagnetic approximations are. If the agreement is satisfactory (eventually using a generalised program which includes neutral gas) it should be possible to design experiments so that specified field configurations are set up. This paper treats the simplest possible model for the dynamical problem of the pinch collapse, namely a fully ionized plasma. It is the first of a series of papers dealing with calculations on the pinch. The series will describe a joint attempt by A.E.R.E. Harwell and the Max-Planck-Institut für Physik und Astrophysik, to set up quite general programs for big computers to calculate the pinch effect in hydromagnetic approximation. Within this restriction the equations should be as close as possible to the physics of the actual experiments. The comparison between experiments and these computations should give evidence on how good the hydromagnetic approximation is. It is planned to generalize this program in some respects, e. g. by including neutral gas, anisotropic pressure, toroidal geometry. Eventually one would hope to be able to design circuits to achieve field distributions specified beforehand, e. g. for reasons of stability.The paper consists mainly of three parts. In the first part the set of equations is derived and the boundary conditions are discussed. In the second part the numerical methods are described. The third part gives the comparison between experiments and computations. I. The hydromagnetic equations (two fluid model)A fully ionized plasma is assumed to fill an infinitely long cylinder. Only z and Q magnetic field components are allowed. All quantiti...

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Advances in Li-ion technology mean that manufacturers currently produce cells that have higher energy densities, higher rate capabilities, and longer quoted cycle lives than the currently qualified ABSL space cells. It is therefore possible that cells are available that could enable a lower mass/volume solution for a given application.ABSL carry out regular reviews of commercial off the shelf (COTS) cells, to determine whether any available cells are suitable for space applications, and offer superior performance to those currently qualified. This paper describes the process that is followed to review and test commercial cells. INTRODUCTIONABSL has used the 18650HC(M) for space batteries since 1998; it was employed on the first ever Li-ion space battery for the PROBA-1 mission. Although the detailed performance and life-time characteristics of these cells are very well understood, advances in Li-ion technology mean that manufacturers currently produce cells that have double the energy density of this heritage cell. In addition, cells are available with the same energy density as the HC(M) but with considerably higher rate capabilities. Cells with longer cycle life have also been developed, although there is normally a trade-off in energy density such that a simple comparison cannot be made for end-of-life (EoL) performance.To date, ABSL have qualified three Li-ion cells for space applications, these are:x 18650HC(M). The heritage ABSL cell has a nominal capacity of 1.5Ah (133 Wh/kg) and has been extensively characterised. The design was modified in 2009 to include a central mandrel; this was to ensure a clear vent path in the case of overpressure. The cell was completely re-qualified following this change. x 18650HR. This cell was qualified specifically for a launch vehicle program and later adopted for MARES on the ISS. The cell has lower capacity than the HC(M) cell, but can deliver significantly higher currents. x 18650NL. This cell provides a considerable increase in energy density compared to the HC(M) cell: 189 Wh/kg compared to 133 Wh/kg. COTS cells have been recently assessed to identify those that may provide a performance benefit compared to the currently qualified cells. Due to the long durations for full qualification, and the quantity of life test data required to predict the long term performance, these reviews are carried out regularly. REVIEW PROCESSThe initial stage of any COTS assessment is to determine what cells are available on the market. During the last market survey, cells from over 40 companies were assessed. For this review, a commercially available database was used for the initial search [1]. The database was used to filter the available cells by chemistry and form factor; these were then ranked by performance requirements, e.g. energy density and cycle life.Once the initial list of cells was acquired from the database, the cell specification sheets were obtained. The data from these sheets were then assessed in detail against the cell performance requirements described below....