Guideline requirements for serviceable spacecraft grasping/berthing/docking interfaces based on simulations and flight experience (survey paper)

As space vehicles and structures become larger and more complex, the development of systems to assist humans in assembling, operating, maintaining, and performing space rescue or retrieval of these vehicles and structures becomes increasingly important. With the diversity of international spacecraft, both manned and unmanned, planned to be in orbit in the future, a set of guidelines for berthing and docking subsystems is mandatory if servicing, resupply, and retrieval is to become practical on an international level. Successful interaction between these space systems and ground and/or space-based humans requires standardized and effective operational interface designs, particularly with respect to space grasping/berthing/docking interface mechanisms. This paper defines the spacecraft mechanical interfaces necessary to create a standard dynamic envelope for joining two free-flying spacecraft in a 'hard' berth or dock with each other in space. A review was made of past space flights and dynamics simulations dating back to 1962 to obtain necessary parameters and their values for successful manually controlled and autonomous spacecraft docking/berthing. The various spacecraft docking/berthing mechanisms and concepts are illustrated along with their dynamic capture and impact tolerances including maximum contact velocity along the approach axis and in the y-z plane; capture linear misalignment tolerances; and maximum capture roll, pitch, and yaw angles. From this data sets of recommended guidelines parameters were developed for autonomous and manual impact docking tolerances, non-impact grasping/berthing tolerances (end effectors), berthing contact conditions, and alignment tolerances after rigidizing. Also, detailed requirements were developed for mechanical design interface features, as well as latching, unlatching, and separation tolerances. This data was drafted in the form of a proposed ANSI Standard guideline, reviewed, and added to by members of the committee representing several spacecraft manufacturers, NASA, and the USAF, and a consensus was reached

Guideline requirements for serviceable spacecraft grasping/berthing/docking interfaces based on simulations and flight experience

The described efforts support a NASA Space Assembly and Servicing Working Group activity to draft guideline interface standards. The general requirements are to provide a simple, reliable, and durable system. Interface requirements developed include lateral position offset, axial and lateral velocities, and angular misalignment. A survey of concepts and simulation studies of spacecraft docking, existing docking/end effector performance criteria, and space proven, qualified docking data was conducted and evaluated, in order to provide recommended mechanical interface guidelines and interface tolerances for manual and autonomous capture operations. The criterion for the selection of the guidelines was maximum capability to handle malfunctions. Originally the guidelines for a zero velocity docking were considered to be covered within the grasping/berthing definition. It is acknowledged that perhaps a separate category needs to be established for this operation. The draft standard was delivered to the AIAA for review, revision, and issuance as the first U.S. national standard guideline on interfaces. The intent is to develop the guidelines into an International Standards Organization standard

Welfare Reform: The View from New Hampshire and Massachusetts

As he promised during his election campaign, President Carter has proposed a major overhaul of the welfare system. Under the Better Jobs and Income Act, unveiled in August 1977, the major components of the current welfare system would be replaced by a program combining cash assistance and job opportunities. This paper evaluates the Carter proposal based on the experience under existing employment, training and welfare programs and then assesses its potential impact on the states of New Hampshire and Massachusetts. In the course of the discussion, we deal with the following questions: (1) Does the proposal effectively address the weaknesses in the current welfare system? (2) Can the proposal achieve its stated goals? (3) Will the impact of the program vary in states with different characteristics? (4) How do state administrators charged with implementing the program respond to its various components? Although the answers to these questions are seldom conclusive, the weight of the evidence leads us to conclude that there are serious weaknesses in the Carter proposal. Major changes are necessary in order for the program to become a viable alternative to the current system which both improves the status quo and achieves sufficient support to be enacted

Manpower Training and Public Sector Job Creation Under CETA: The Experience in Maine and New Hampshire

On December 28, 1973 President Nixon signed Public Law 93-203, the Comprehensive Employment and Training Act (CETA). The new law represents a significant shift in the roles played by federal, state, and local officials in the expenditure of federal money for manpower services. The key characteristics of CETA are often described as decentralization and decategorization. Prior to the passage of CETA the manpower system was almost exclusively under the control of federal officials. Under CETA, authority has, to some extent, been decentralized as state and local governments have been given block grants of money to be spent on manpower services in accord with locally determined priorities. In addition, CETA has made it possible for states and localities to escape the restrictive categorical programs of the past and to develop programs of a more flexible and more comprehensive nature. In this paper we examine the experience under CETA in Maine and New Hampshire. We will identify some of the problems which have emerged in the experience to date, evaluate the impact that CETA has had on the unemployed, underemployed, and economically disadvantaged, and assess the potential and possibilities which exist for making CETA a truly effective system for solving manpower problems

Recreational Use of Six Prairie Wetlands in Eastern South Dakota

A recreational use survey was conducted at 6 public wetlands in eastern South Dakota from August 9, 1981 through August 8, 1982. Four hundred and fifty-eight postcard questionnaires were placed on vehicles encountered at these marshes during random time periods. Two hundred and thirty-five were voluntarily returned for a response rate of 51.3%. Approximately 10, 020 people made 4,778 trips to these wetlands and spent 63, 093 man-hours. Thirty-one different activities were observed or reported. Hunting accounted for 96.0% of all fall trips and 89.1% of yearly visits. Over 89% of all visits occurred during fall and over 50% of the trips were multiple use. Duck hunting occurred during 83. 8% of all fall trips; goose hunting, 4-g. 5%; and pheasant hunting, 23.0%. Users came from 25 South Dakota counties and several other states. Seventy-two percent of all users lived within an hour drive of the marshes. The average user of the study sites made 19.4 trips for consumptive activities and 4.1 trips for non-consumptive activities per year to South Dakota public marshes. Marsh usage during the opening week of waterfowl season was significantly greater (F = 3. 81, P = 0. 002) than all other weekly totals. Opening weeks for pheasant and trapping seasons also showed peak usage, although trapping accounted for just 2. 7% of all fall trips. It appeared that high goose concentrations also contributed to greater usage by hunters. Both holidays and weekends received more use than weekdays. Fifty-five percent of the total use was in the morning. Most duck hunters used the sunrise to 0900 period and goose hunters the 0900 to noon period. There was no significant difference (F = 0. 28, P =0.885) among time periods used by pheasant hunters. The net present value of these wetland study sites is $653 per hectare for hunting alone when infinitely discounted into the future using the social discount rate of 7. 875$123, 279 for the 198 1 hunting season. In addition, wetlands provide other recreational benefits that cannot be recorded through on-site studies

Shepherding Church Staff: Stakeholders\u27 perceptions of a Useful Leadership Development Plan

As leadership demands grow, churches need a way to develop more effective leaders. Many pastors have received limited training in how to develop leaders and may not be aware of stakeholders’ expectations for leadership development. This thesis project reveals the importance of intentional leadership development of those who have answered the calling to work in the local church. The researcher believes the current shortage of lay leaders as well as consistent burnout rates among staff and volunteers can be altered with the correct plan and people in place. The researcher conducted open ended semi-structured interviews for those currently working in full-time church leadership capacity to gain knowledge about what would be helpful in their development. The responses should help those in high-level leadership positions understand what people are craving from their leaders. The central finding from this study was that if stakeholders are involved in developing a useful Leadership Development Plan (LDP), they recommend one that strengthens relationships, develops more leaders, grows individuals, and aligns the team with the mission of the church

The relationship between induced fluid structure and boundary slip in nanoscale polymer films

The molecular mechanism of slip at the interface between polymer melts and weakly attractive smooth surfaces is investigated using molecular dynamics simulations. In agreement with our previous studies on slip flow of shear-thinning fluids, it is shown that the slip length passes through a local minimum at low shear rates and then increases rapidly at higher shear rates. We found that at sufficiently high shear rates, the slip flow over atomically flat crystalline surfaces is anisotropic. It is demonstrated numerically that the friction coefficient at the liquid-solid interface (the ratio of viscosity and slip length) undergoes a transition from a constant value to the power-law decay as a function of the slip velocity. The characteristic velocity of the transition correlates well with the diffusion velocity of fluid monomers in the first fluid layer near the solid wall at equilibrium. We also show that in the linear regime, the friction coefficient is well described by a function of a single variable, which is a product of the magnitude of surface-induced peak in the structure factor and the contact density of the adjacent fluid layer. The universal relationship between the friction coefficient and induced fluid structure holds for a number of material parameters of the interface: fluid density, chain length, wall-fluid interaction energy, wall density, lattice type and orientation, thermal or solid walls.Comment: 33 pages, 14 figure