The Juno Radiation Monitoring (RM) Investigation

The Radiation Monitoring Investigation of the Juno Mission will actively retrieve and analyze the noise signatures from penetrating radiation in the images of Juno’s star cameras and science instruments at Jupiter. The investigation’s objective is to profile Jupiter’s \(>10\mbox{-MeV}\) electron environment in regions of the Jovian magnetosphere which today are still largely unexplored. This paper discusses the primary instruments on Juno which contribute to the investigation’s data suite, the measurements of camera noise from penetrating particles, spectral sensitivities and measurement ranges of the instruments, calibrations performed prior to Juno’s first science orbit, and how the measurements may be used to infer the external relativistic electron environment.     

A Stochastic Algorithm for Sensitivity Analysis

A direct stochastic sensitivity analysis algorithm is developed for linear dynamical systems having incompletely known input statistics. The new algorithm extends previous results by applying covariance propagation concepts which utilize as a forcing function the sensitivity covariance matrix associated with the uncertainty in the elements of the system input covariance matrix itself. The developed algorithm is evaluated in the context of a generalized sensitivity analysis formulation involving nonlinear transformations on the input signals. Numerical results are provided to demonstrate the usefulness of the new algorithm.     

RPC-ICA: The Ion Composition Analyzer of the Rosetta Plasma Consortium

The Ion Composition Analyzer (ICA) is part of the Rosetta Plasma Consortium (RPC). ICA is designed to measure the three-dimensional distribution function of positive ions in order to study the interaction between the solar wind and cometary particles. The instrument has a mass resolution high enough to resolve the major species such as protons, helium, oxygen, molecular ions, and heavy ions characteristic of dusty plasma regions. ICA consists of an electrostatic acceptance angle filter, an electrostatic energy filter, and a magnetic momentum filter. Particles are detected using large diameter (100 mm) microchannel plates and a two-dimensional anode system. ICA has its own processor for data reduction/compression and formatting. The energy range of the instrument is from 25 eV to 40 keV and an angular field-of-view of 360° × 90° is achieved through electrostatic deflection of incoming particles.     

Design of high-efficiency series-resonant converters aboveresonance

Power losses in series-resonant converters (SRCs) operated above resonance are examined for the purpose of developing design guidelines leading to SRC designs with the highest possible operating efficiencies. Loss expressions are formulated and analyzed as functions of normalized voltage conversion ratio M and normalized output current J for the controlled transistor switches, antiparallel diodes, bridge diodes, and resonant capacitor. Overall losses range from a low of nearly 9% to a maximum of about 17%. Operating efficiencies corresponding to these losses range from a high of 92% to a low of 85%. Operation at the maximum efficiency of 92% occurs at values of M close to unity and is not highly dependent on J. However, in a practical closed-loop regulated SRC, operation with M too close to unity could provide an insufficient design margin, given component tolerances or other variations     

Human locomotion and workload for simulated lunar and Martian environments

Human locomotion in simulated lunar and Martian environments is investigated. A unique human-rated underwater treadmill and an adjustable ballasting harness simulate partial gravity in order to better understand how gravity determines the biomechanics and energetics of human locomotion. This study has two research aspects, biomechanics and energetics. The fundamental biomechanics measurements are continuously recorded vertical forces as exerted by subjects of the treadmill which is instrumented with a force platform. Experimental results indicate that peak vertical force and stride frequency decrease as the gravity level is reduced. Foot contact time is independent of gravity level. Oxygen uptake measurements, VO2, constitute the energetics, or workload, data for this study. As theory predicts, locomotion energy requirements for lunar (1/6-g) and Martian (3/8-g) gravity levels are significantly less than at 1-g. The observed variation in workload with gravity level is nonmonotonic, however, in over half the subject population. The hypothesis is offered that energy expenditure increases for lunar, as compared with Martian, locomotion due to the subject "wasting energy" for stability and posture control in simulated lunar gravity. Biomechanics data could influence advanced spacesuit design and planetary habitat design, while workload data will help define oxygen requirements for planetary life support systems.     

Navier–Stokes solvers in European aircraft design

The paper gives a broad perspective of the progress made during the last 10 years in solving the Navier–Stokes equations and traces how this simulation technique went from being a specialized research topic to a practical engineering tool that design engineers use on a routine basis.

The scope is limited to Navier–Stokes solvers applied to industrial design of airframes with attention focused particularly on developments in Europe. An overview of the different Navier–Stokes codes used in Europe is given, and on-going developments are outlined.

The current state of progress is illustrated by computed steady and unsteady solutions to industrial problems, ranging from airfoil characteristics, flow around an isolated wing, to full aircraft configurations.

A discussion on the future industrial design environment is given, and developments in Europe towards a more integrated design approach with underlying concepts like ‘concurrent engineering (CE)’ and the ‘virtual product (VP)’ are summarized. The paper concludes with a discussion on future challenging applications.     

Laboratory Experiments on Preplanetary Dust Aggregation

For a better understanding of the processes which lead to the formation of planetesimals in the early solar nebula, we performed an extensive series of laboratory experiments. We find that the capture velocities in collisions between spherical grains are more than one order of magnitude higher than predicted by Chokshi et al (1993). In contrast, irregular grains have no capture threshold and can be better described by a sticking probability which is typically a few 10%, even for velocities exceeding 10 m/s. However, adhesion forces between spherical, micron-sized particles match the theoretical predictions very well, although contact areas and deformations are of the order of inter-atomic distances only. Aggregation experiments in rarefied turbulent gases reveal the fractal nature of dust aggregates. Mass distribution functions are bell-shaped. Similar behaviour can be found in aggregation experiments with sedimenting particles. Experiments on collision-induced aggregate compaction and fragmentation match the numerical simulations by Dominik and Tielens (1997) very well if revised experimental values of the break-up energy (from our impact experiments) and the rolling-friction force (from our AFM measurements on particle chains) are used. This revised version was published online in June 2006 with corrections to the Cover Date.