Some Thoughts on Satisfying Spacecraft Passivation Requirements

Most spacecraft have at least one pressurized vessel on board. In addition to a hole, it is possible that a pressure vessel may experience catastrophic failure (i.e. rupture) as a result of a hypervelocity impact. If a tank rupture were to occur on-orbit following a micrometeoroid or orbital debris particle impact, for example, not only could it lead to loss of life, but it would also generate a tremendous amount of debris that could compromise future space assets working in similar orbits. As a result, NASA and other space faring nations have put in place spacecraft design requirements to prevent additional sizable debris from being created in the event of pressure vessel rupture or catastrophic failure. In general, these requirements state that a spacecraft’s stored energy devices are to be passivated at the end of a spacecraft’s mission or useful life. Programs whose spacecraft designs are not be able to comply with some aspects of those requirements employ an alternative, so-called “soft passivation”, option. This paper provides a summary of a project performed with the intent of providing some possible guidelines and considerations that can be used by satellite programs to help satisfy passivation requirements using a “soft passivation” approach, that is, when not able to perform complete hard passivation

Scaled momentum spectra in deep inelastic scattering at HERA

Charged particle production has been studied in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 0.44 fb(-1). Distributions of scaled momenta in the Breit frame are presented for particles in the current fragmentation region. The evolution of these spectra with the photon virtuality, Q(2), is described in the kinematic region 10 < Q(2) < 41000 Ge V-2. Next-to-leading-order and modified leading-log-approximation QCD calculations as well as predictions from Monte Carlo models are compared to the data. The results are also compared to e(+)e(-) annihilation data. The dependences of the pseudorapidity distribution of the particles on Q(2) and on the energy in the gamma p system, W, are presented and interpreted in the context of the hypothesis of limiting fragmentation

Combined Measurement and QCD Analysis of the Inclusive e+- p Scattering Cross Sections at HERA

A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised ep scattering at HERA during the period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer squared, Q^2, and in Bjorken x. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions HERAPDF1.0 with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result