The resupply interface mechanism RMS compatibility test

Spacecraft on-orbit servicing consists of exchanging components such as payloads, orbital replacement units (ORUs), and consumables. To accomplish the exchange of consumables, the receiving vehicle must mate to the supplier vehicle. Mating can be accomplished by a variety of docking procedures. However, these docking schemes are mission dependent and can vary from shuttle bay berthing to autonomous rendezvous and docking. Satisfying the many docking conditions will require use of an innovative docking device. The device must provide fluid, electrical, pneumatic and data transfer between vehicles. Also, the proper stiffness must be obtained and sustained between the vehicles. A device to accomplish this, the resupply interface mechanism (RIM), was developed. The RIM is a unique device because it grasps the mating vehicle, draws the two vehicles together, simultaneously mates all connectors, and rigidizes the mating devices. The NASA-Johnson Manipulator Development Facility was used to study how compatible the RIM is to on orbit docking and berthing. The facility contains a shuttle cargo bay mockup with a remote manipulator system (RMS). This RMS is used to prepare crew members for shuttle missions involving spacecraft berthing operations. The MDF proved to be an excellant system for testing the RIM/RMS compatibility. The elements examined during the RIM JSC test were: RIM gross and fine alignment; berthing method sequence; visual cuing aids; utility connections; and RIM overall performance. The results showed that the RIM is a good device for spacecraft berthing operations. Mating was accomplished during every test run and all test operators (crew members) felt that the RIM is an effective device. The purpose of the JSC RIM test and its results are discussed

Manned Mars mission on-orbit operations FTS capabilities assessment

This document presents an overview of the characteristics and capabilities of the flight telerobotic servicer (FTS), under development at GSFC at the time the report was prepared; the project has since been cancelled. The assessment was directed toward developing the FTS to enable assembly and servicing of the Mars vehicle at the space station; facilitate rendezvous, docking, and fluid transfer operations involving the Mars vehicle fuel tank; to perform strip-mining operations on the lunar/martian surfaces; and to construct a three-story shelter on the martian surface. The report considers the FTS' mechanical, electrical, thermal, and operational subsystems, as well as its proposed manipulator capabilities

Experience with Delay-Tolerant Networking from Orbit

We describe the first use from space of the Bundle Protocol for Delay-Tolerant Networking (DTN) and lessons learned from experiments made and experience gained with this protocol. The Disaster Monitoring Constellation (DMC), constructed by Surrey Satellite Technology Ltd (SSTL), is a multiple-satellite Earth-imaging low-Earth-orbit sensor network in which recorded image swaths are stored onboard each satellite and later downloaded from the satellite payloads to a ground station. Store-and-forward of images with capture and later download gives each satellite the characteristics of a node in a disruption-tolerant network. Originally developed for the Interplanetary Internet, DTNs are now under investigation in an Internet Research Task Force (IRTF) DTN research group (RG), which has developed a bundle architecture and protocol. The DMC is technically advanced in its adoption of the Internet Protocol (IP) for its imaging payloads and for satellite command and control, based around reuse of commercial networking and link protocols. These satellites use of IP has enabled earlier experiments with the Cisco router in Low Earth Orbit (CLEO) onboard the constellation s UK-DMC satellite. Earth images are downloaded from the satellites using a custom IP-based high-speed transfer protocol developed by SSTL, Saratoga, which tolerates unusual link environments. Saratoga has been documented in the Internet Engineering Task Force (IETF) for wider adoption. We experiment with the use of DTNRG bundle concepts onboard the UK-DMC satellite, by examining how Saratoga can be used as a DTN convergence layer to carry the DTNRG Bundle Protocol, so that sensor images can be delivered to ground stations and beyond as bundles. Our practical experience with the first successful use of the DTNRG Bundle Protocol in a space environment gives us insights into the design of the Bundle Protocol and enables us to identify issues that must be addressed before wider deployment of the Bundle Protocol. Published in 2010 by John Wiley & Sons, Ltd. KEY WORDS: Internet; UK-DMC; satellite; Delay-Tolerant Networking (DTN); Bundle Protoco

Severe mental illness and cardioprotective medication prescribing:qualitative study in general practice

BACKGROUND: Patients with severe mental illness (SMI) die 10-20 years earlier than the general population. They have a higher risk of cardiovascular disease (CVD) yet may experience lower cardioprotective medication prescribing. AIM: To understand the challenges experienced by GPs in prescribing cardioprotective medication to patients with SMI. DESIGN AND SETTING: A qualitative study with 15 GPs from 11 practices in two Scottish Health Boards, including practices servicing highly-deprived areas (Deep End). METHOD: Semi-structured 1:1 interviews with fully-qualified GPs with clinical experience of patients with SMI. Interviews were transcribed verbatim and analysed thematically. RESULTS: Participants aimed to routinely prescribe cardioprotective medication to relevant patients with SMI but were hampered by various challenges. These included: lack of funding for chronic disease management, insufficient consultation time, workforce shortages, IT infrastructure and navigating boundaries with mental health services. Patient-related challenges included: patients’ complex health and social needs, their understandable prioritisation of mental health needs/existing physical conditions and presentation during crises. Participants emphasised continuity of care as fundamental in engaging this patient group in effective cardiovascular health management. A cross-cutting theme was the current GP workforce crisis leading to ‘firefighting’ and diminishing capacity for primary prevention. This was particularly acute in Deep End practices, which have a high proportion of patients with complex needs and greater resource challenges. CONCLUSION: Although participants aspire to prescribe cardioprotective medication to patients with SMI, professional, system and patient-level barriers often make this challenging, particularly in deprived areas due to patient complexity and the inverse care law. KEYWORDS Cardiovascular Disease; General Practice; Healthcare Inequalities; Mental Disorders; Prescribing Patterns; Qualitative Research. <br/

Angular momentum of the electromagnetic field: the plane wave paradox resolved

The angular momentum of a classical electromagnetic plane wave of arbitrary extent is predicted to be, on theoretical grounds, exactly zero. However, finite sections of circularly polarized plane waves are found experimentally to carry angular momentum and it is known that the contribution to the angular momentum arises from the edges of the beam. A mathematical model is described that gives a quantitative account of this effect and resolves the paradox.Comment: 12 pages, 1 figur

Cosmological perturbation theory and conserved quantities in the large-scale limit

The linear cosmological perturbation theory of an almost homogeneous and isotropic perfect fluid universe is reconsidered and formally simplified by introducing new covariant and gauge-invariant variables with physical interpretations on hypersurfaces of constant expansion, constant curvature or constant energy density. The existence of conserved perturbation quantities on scales larger than the Hubble scale is discussed. The quantity which is conserved on large scales in a flat background universe may be expressed in terms of the fractional, spatial gradient of the energy density on constant expansion hypersurfaces or, alternatively, with the help of expansion or curvature perturbation variables on hypersurfaces of constant energy density. For nonvanishing background curvature the perturbation dynamics is most suitably described in terms of energy density perturbations on hypersurfaces of constant curvature.Comment: 12 pages, Revtex, to appear in Class.Quantum Gra

Slim Epistemology with a Thick Skin

The distinction between ‘thick’ and ‘thin’ value concepts, and its importance to ethical theory, has been an active topic in recent meta-ethics. This paper defends three claims regarding the parallel issue about thick and thin epistemic concepts. (1) Analogy with ethics offers no straightforward way to establish a good, clear distinction between thick and thin epistemic concepts. (2) Assuming there is such a distinction, there are no semantic grounds for assigning thick epistemic concepts priority over the thin. (3) Nor does the structure of substantive epistemological theory establish that thick epistemic concepts enjoy systematic theoretical priority over the thin. In sum, a good case has yet to be made for any radical theoretical turn to thicker epistemology

Perspective on gravitational self-force analyses

A point particle of mass $\mu$ moving on a geodesic creates a perturbation $h_{ab}$, of the spacetime metric $g_{ab}$, that diverges at the particle. Simple expressions are given for the singular $\mu/r$ part of $h_{ab}$ and its distortion caused by the spacetime. This singular part h^\SS_{ab} is described in different coordinate systems and in different gauges. Subtracting h^\SS_{ab} from $h_{ab}$ leaves a regular remainder $h^\R_{ab}$. The self-force on the particle from its own gravitational field adjusts the world line at \Or(\mu) to be a geodesic of $g_{ab}+h^\R_{ab}$; this adjustment includes all of the effects of radiation reaction. For the case that the particle is a small non-rotating black hole, we give a uniformly valid approximation to a solution of the Einstein equations, with a remainder of \Or(\mu^2) as $\mu\to0$. An example presents the actual steps involved in a self-force calculation. Gauge freedom introduces ambiguity in perturbation analysis. However, physically interesting problems avoid this ambiguity.Comment: 40 pages, to appear in a special issue of CQG on radiation reaction, contains additional references, improved notation for tensor harmonic

Optimizing crop production through control of water and salinity levels in the soil

Sizable investments have been made and continue to be made throughout the world to develop irrigation potentials. Recent food shortages have heightened the concern for obtaining greater returns to irrigation through improved water management and use. A knowledge of how plant growth cycles relate to moisture and salinity levels in the root zone is prerequisite to developing practical ways of maintaining optimum conditions for maximum production per unit of water concerned. This research further defines the role of irrigation timing and salinity management on crop production, and proposes practical techniques for predicting the crop response to management measures. Some of the advantages and special features of the research program outlined by the report are listed as follows: 1. The experimental design is unique in that a sprinkler line is used as a single source of water. This approach provides large volumes of yield data as influenced by water supplies available to the crop. These data will provide information on the following: a. Accurate evaluation of the basic water requirements of crops. b. The optimal sequencing of deficits during crop growth stages. c. The establishment of yield versus evapotranspiration relationships over the entire range of wter supply from rainfall (dryland) to over-irrigation. d. An evaluation of soil water holding capacities in terms of its contributions to the water needs of the crop. This information provides guidance on how to best utilize the root system of a given crop type as a water gathering tool in terms of time during the growing season. For example, planting date, plant spacing, and fertilizer practices will be influenced by this information. 2. The experimental layout is versatile in that it lends itself to a study of the effects on plant growth of input parameters other than water, such as fertility levels and plant spacing. 3. The design can be readily adapted to accommodate several varieties and/or species in the same experiment. 4. The research results are practical and generally applicable to a wide range of crop, climate, soil, and water supply (non site specific and site specific) conditions. 5. The research provides a clear demonstration (both visual and quantitative) of the beneficial effects of proper management practices on crop production. 6. The research deals with both domestic and international water problems involving crop production, namely, the influence of available soil measure and soil salinity on plant yields. 7. The research techniques are readily adaptable to application in developing countries. a. A sprinkler system for irrigation is not necessary though desireable. b. The research procedures are simple, inexpensive, easy to perform, and yet provide much information. 8. The research involves the join efforts of several institutions and utilizes highly experienced research principal investigators who have a proven record of effectively working together as an integrated team. 9. The validity of the research approach and the viability of the results have been demonstrated by current research. The main tasks remaining are to broaden the crop base and to test and demonstrate the applicability of the results to other areas throughout the world