On orbit validation of solar sailing control laws with thin-film spacecraft

Many innovative approaches to solar sail mission and trajectory design have been proposed over the years, but very few ever have the opportunity to be validated on orbit with real spacecraft. Thin- Film Spacecraft/Lander/Rovers (TF-SL Rs) are a new class of very low cost, low mass space vehicle which are ideal for inexpensively and quickly testing in flight new approaches to solar sailing. This paper describes using TF- SLR based micro solar sails to implement a generic solar sail test bed on orbit. TF -SLRs are high area- to-mass ratio (A/m) spacecraft developed for very low cost consumer and scientific deep space missions. Typically based on a 5 μm or thinner metalised substrate, they include an integrated avionics and payload system -on-chip (SoC) die bonded to the substrate with passive components and solar cells printed or deposited by Metal Organic Chemical Vapour Deposition (MOCVD). The avionics include UHF/S- band transceivers, processors, storage, sensors and attitude control provided by integrated magnetorquers and reflectivity control devices. Resulting spacecraft have a typical thickness of less than 50 μm, are 80 mm in diameter, and have a mass of less than 100 mg resulting in sail loads of less than 20 g/m 2 . TF -SLRs are currently designed for direct dispensing in swarms from free flying 0.5U Interplanetary CubeSats or dispensers attached to launch vehicles. Larger 160 mm, 320 mm and 640 mm diameter TF -SLRs utilizing a CubeSat compatible TWIST deployment mechanism that maintains the high A/m ratio are also under development. We are developing a mission to demonstrate the utility of these devices as a test bed for experimenting with a variety of mission designs and control laws. Batches of up to one hundred TF- SLRs will be released on earth escape trajectories, with each batch executing a heterogeneous or homogenous mixture of control laws and experiments. Up to four releases at different points in orbit are currently envisaged with experiments currently being studied in MATLAB and GMA T including managing the rate of separation of individual spacecraft, station keeping and single deployment/substantially divergent trajectory development. It is also hoped to be able to demonstrate uploading new experiment designs while in orbit and to make this capability available to researchers around the world. A suitable earth escape mission is currently being sought and it is hoped the test bed could be on orbit in 2017/18

Topological optimization of compliant adaptive wing structure

Load-path-based topology optimization is used to synthesize a compliant adaptive aircraft wing leading edge, which deforms in a prescribed way when subject to a single point internal actuation. The load-path-based optimization method requires the specification of a parent lattice. Increasing the complexity of this lattice means the number of parameters required for a complete representation of the structure in the topology optimization becomes prohibitive, although it is desirable to enable a full exploration of the design space. A new method based on graph theory and network analysis is proposed, which enables a substantial reduction in the required number of parameters to represent the parent lattice. The results from this load-path-based approach are compared with those obtained from the better-known density-based topology optimization method

Effects of Viscoelasticity on the Deployment of Bistable Tape Springs

The effects of stowage on the deployment of composite bistable tape springs are studied. A viscoelastic analytical model is used to predict the relaxation and stability of the structure in its coiled state. The time-dependent stability analysis reveals that the structure remains bistable throughout the relaxation process. A dynamic model is then applied to predict the deployment of the structure once it is released. Experimental deployment results match the deployment predictions within 3% for the case where no stowage is applied. It is shown that stowage causes an increase in the deployment time; in this case, experimental deployment times overshoot those predicted by the model. Secondary effects are observed at high stowage temperatures, which are not predicted by the analytical model. These effects include an abrupt change in the deployment dynamics and a large increase in the deployment time (deployment latency). At higher temperatures still, i.e. for stowage at 100°C, the structure fails to deploy and becomes stable at all extended lengths

Altitude dependence of atmospheric temperature trends: Climate models versus observation

As a consequence of greenhouse forcing, all state of the art general circulation models predict a positive temperature trend that is greater for the troposphere than the surface. This predicted positive trend increases in value with altitude until it reaches a maximum ratio with respect to the surface of as much as 1.5 to 2.0 at about 200 to 400 hPa. However, the temperature trends from several independent observational data sets show decreasing as well as mostly negative values. This disparity indicates that the three models examined here fail to account for the effects of greenhouse forcings.Comment: 9 pages, 3 figure

Uncovering \u27Hidden\u27 Signals: Previously Presumed Visual Signals Likely Generate Air Particle Movement

Wolf spiders within the genus Schizocosa have become a model system for exploring the form and function of multimodal communication. In terms of male signaling, much past research has focused on the role and importance of dynamic and static visual and substrate-borne vibratory communication. Studies on S. retrorsa, however, have found that female-male pairs were able to successfully mate in the absence of both visual and vibratory stimuli, suggesting a reduced or non-existent role of these signaling modalities in this species. Given these prior findings, it has been suggested that S. retrorsa males may utilize an additional signaling modality during courtship-air particle movement, often referred to as near-field sound-which they likely produce with rapid leg waving and receive using thin filiform sensory hairs called trichobothria. In this study, we tested the role of air-particle movement in mating success by conducting two independent sets of mating trials with randomly paired S. retrorsa females and males in the dark and on granite (i.e., without visual or vibratory signals) in two different signaling environments-(i) without ( No Noise ) and (ii) with ( Noise ) introduced air-particle movement intended to disrupt signaling in that modality. We also ran foraging trials in No Noise/Noise environments to explore the impact of our treatments on overall behavior. Across both mating experiments, our treatments significantly impacted mating success, with more mating in the No Noise signaling environments compared to the Noise environments. The rate of leg waving-a previously assumed visual dynamic movement that has also been shown to be able to produce air particle displacement-was higher in the No Noise than Noise environments. Across both treatments, males with higher rates of leg waving had higher mating success. In contrast to mating trials results, foraging success was not influenced by Noise. Our results indicate that artificially induced air particle movement disrupts successful mating and alters male courtship signaling but does not interfere with a female\u27s ability to receive and assess the rate of male leg waving

Reactive direction control for a mobile robot: A locust-like control of escape direction emerges when a bilateral pair of model locust visual neurons are integrated

Locusts possess a bilateral pair of uniquely identifiable visual neurons that respond vigorously to the image of an approaching object. These neurons are called the lobula giant movement detectors (LGMDs). The locust LGMDs have been extensively studied and this has lead to the development of an LGMD model for use as an artificial collision detector in robotic applications. To date, robots have been equipped with only a single, central artificial LGMD sensor, and this triggers a non-directional stop or rotation when a potentially colliding object is detected. Clearly, for a robot to behave autonomously, it must react differently to stimuli approaching from different directions. In this study, we implement a bilateral pair of LGMD models in Khepera robots equipped with normal and panoramic cameras. We integrate the responses of these LGMD models using methodologies inspired by research on escape direction control in cockroaches. Using ‘randomised winner-take-all’ or ‘steering wheel’ algorithms for LGMD model integration, the khepera robots could escape an approaching threat in real time and with a similar distribution of escape directions as real locusts. We also found that by optimising these algorithms, we could use them to integrate the left and right DCMD responses of real jumping locusts offline and reproduce the actual escape directions that the locusts took in a particular trial. Our results significantly advance the development of an artificial collision detection and evasion system based on the locust LGMD by allowing it reactive control over robot behaviour. The success of this approach may also indicate some important areas to be pursued in future biological research

“When it goes back to my normal I suppose”: a qualitative study using online focus groups to explore perceptions of ‘control’ amongst people with eczema and parents of children with eczema in the UK

Objective: To inform the development of a core outcome set for eczema by engaging with people with eczema and parents of children with eczema to understand their experiences and understanding of the concept “eczema control”. Design: 37 participants took part in a total of 6 semi-structured online focus groups held in a typed chatroom with 5-7 participants per group. Three groups involved adults with eczema and three groups involved parents of children with eczema. Framework analysis was used for data analysis. Setting: A community-based sample was recruited from across the UK via social media and email. Participants: 19 adults aged 17-61 (15/19 female, 16/19 white) and 18 parents of children with eczema aged 9 months-17 years (9/18 female, 18/19 white). Results: Four main themes were identified. 1) “Commonalities and differences in the experiences of control”: a reduction in symptoms such as itch and sleep loss characterised eczema control, but what level was acceptable differed across participants. 2) “Eczema control goes beyond the skin”: psychological factors, social factors, the constant scratching and the impact on everyday activities are a variety of ways an individual can be impacted. 3) “Stepping up and down of treatment”: participants’ stepped-up treatment in response to loss of control, but several factors complicated this behaviour. Control needed to be maintained after stepped-up treatment ended to be acceptable. 4) “How to measure control”: self-report was generally preferred to allow frequent measurements and to capture unobservable features. Although most thought their eczema needed to be measured frequently, many also felt that this was not always realistic or desirable. Conclusions: Eczema “control” is a complex experience for people with eczema and parents of children with the condition. These experiences could have important implications on how long-term control should be measured in eczema clinical trials and clinical practice

The innervation of the enthesis organ of the rat achilles tendon

PURPOSE: The enthesis (bony insertion of a tendon or ligament) is a common site of overuse injuries in sport. Because enthesopathies can be painful, it is often assumed that the enthesis is highly innervated-but with little evidence to support the assumption. The Achilles tendon has one of the most complex of attachment sites, for together with adjacent tissues, the enthesis itself forms part of an 'enthesis organ' which reduces stress concentration at the bony interface. These adjacent structures include a 'sesamoid fibrocartilage' in the tendon, a 'periosteal fibrocartilage' on the superior tuberosity of the calcaneus, and a fat pad which extends into the retrocalcaneal bursa during plantarflexion. The purpose of the present study is to investigate the innervation of the whole enthesis organ complex. METHODS: The tendon attachment site was removed from one leg of 3 male Wistar rats at each of the following ages-neonates, 4 weeks, 12 weeks, and 24 months. The tissue was fixed in 4% paraformaldehyde, prepared for routine indirect immunohistochemistry and cryosectioned in the sagittal plane. Serial sections were immunolabelled with polyclonal antibodies to protein gene product 9.5, substance P, calcitonin gene related peptide and neurofilament 200. Histology reference sections were stained with toluidine blue. RESULTS: No nerve fibers were detected at the enthesis itself or in the sesamoid and periosteal fib ro cartilages in rats of any age. However, the fat pad was richly supplied by nerve fibers which immunolabelled with all of the antibodies used. It also contained abundant mast cells. The innervation of the fat pad was confirmed in 10 human Achilles tendons obtained from the Department of Forensic Medicine at the Ludwig-Maximilians-Universität, in accordance with the ethical regulations of Munich University. The nerve fibers again immunolabelled with all antibodies and formed an intricate network in which the fibers lay between individual fat cells. CONCLUSION: We suggest that healthy entheses are not innervated because of the high levels of mechanical loading experienced at insertion sites. However, the striking innervation of the adjacent fat pad suggests that it may have an unheralded proprioceptive role monitoring changes in insertional angle between tendon and bone that occur as a result of foot movements