The Design, Development and Testing of a Propulsion System for the SNAP-1 Nanosatellite

It has frequently been proposed to use very small nanosatellites for missions requiring orbital agility. Whether it be swarms of satellites for scientific or remote-sensing measurements, constellations for communications or single satellites for remote inspection, all require some way of modifying their respective orbits. Novel, high-technology solutions to this requirement have been proposed from MEMS to solar sails. Notwithstanding the eventual availability of such advanced nanosatellite propulsion technologies, the Surrey Space Centre has developed a miniature propulsion subsystem using technology readily available today. On 28th June 2000 Surrey launched SNAP-1, the first in a series of Surrey Nanosatellite Application Platform missions. Amongst other features of this new 6.5 kg nanosatellite is a butane liquefied gas propulsion subsystem to meet the spacecraft\u27s mission requirement of 1 m/s delta V. With a total mass budget of 450 grams, including propellant, dry mass, structural support and drive electronics, this propulsion system will be one of the smallest ever to have flown on a spacecraft. This paper describes some of the interesting challenges in producing such a small system, especially in a seven month concept to launch site program. The flight propulsion system will be described, including novel techniques such as using a coiled tube in the place of a conventional propellant tank. The choice of butane as a propellant will be discussed

Next generation forensic taphonomy: Automation for experimental, field-based research.

Determining the post-mortem interval (PMI) is often a critical goal in forensic casework. Consequently, the discipline of forensic taphonomy has involved considerable research efforts towards achieving this goal, with substantial strides made in the past 40 years. Importantly, quantification of decompositional data (and the models derived from them) and standardisation in experimental protocols are being increasingly recognised as key components of this drive. However, despite the discipline's best efforts, significant challenges remain. Still lacking are standardisation of many core components of experimental design, forensic realism in experimental design, true quantitative measures of the progression of decay, and high-resolution data. Without these critical elements, large-scale, synthesised multi-biogeographically representative datasets - necessary for building comprehensive models of decay to precisely estimate PMI - remain elusive. To address these limitations, we propose the automation of taphonomic data collection. We present the world's first reported fully automated, remotely operable forensic taphonomic data collection system, inclusive of technical design details. Through laboratory testing and field deployments, the apparatus substantially reduced the cost of actualistic (field-based) forensic taphonomic data collection, improved data resolution, and provided for more forensically realistic experimental deployments and simultaneous multi-biogeographic experiments. We argue that this device represents a quantum leap in experimental methodology in this field, paving the way for the next generation of forensic taphonomic research and, we hope, attainment of the elusive goal of precise estimation of PMI. [Abstract copyright: Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.

Analysis of a General Family of Regularized Navier-Stokes and MHD Models

We consider a general family of regularized Navier-Stokes and Magnetohydrodynamics (MHD) models on n-dimensional smooth compact Riemannian manifolds with or without boundary, with n greater than or equal to 2. This family captures most of the specific regularized models that have been proposed and analyzed in the literature, including the Navier-Stokes equations, the Navier-Stokes-alpha model, the Leray-alpha model, the Modified Leray-alpha model, the Simplified Bardina model, the Navier-Stokes-Voight model, the Navier-Stokes-alpha-like models, and certain MHD models, in addition to representing a larger 3-parameter family of models not previously analyzed. We give a unified analysis of the entire three-parameter family using only abstract mapping properties of the principle dissipation and smoothing operators, and then use specific parameterizations to obtain the sharpest results. We first establish existence and regularity results, and under appropriate assumptions show uniqueness and stability. We then establish results for singular perturbations, including the inviscid and alpha limits. Next we show existence of a global attractor for the general model, and give estimates for its dimension. We finish by establishing some results on determining operators for subfamilies of dissipative and non-dissipative models. In addition to establishing a number of results for all models in this general family, the framework recovers most of the previous results on existence, regularity, uniqueness, stability, attractor existence and dimension, and determining operators for well-known members of this family.Comment: 37 pages; references added, minor typos corrected, minor changes to revise for publicatio

Episodic temporal generalization : a developmental study

Groups of 5-year-olds, 10-year-olds, and adults completed either an episodic temporal generalization task, in which no stimuli were repeated, or a repeated standard temporal generalization task, in which there was a fixed standard that was repeated on every trial. Significant developmental improvements were found on both tasks. In both tasks, gradients of performance over two different stimulus ranges superimposed well when plotted on the same relative scale. Performance was similar for the adults and 10-year-olds across tasks, but the 5-year-olds performed better on the repeated standard task. These findings suggest that perceptual processes are a source of scalar variability in timing, and that there are developmental changes in levels of such variability