Michael L. Tinker

Damping phenomena in a wire rope vibration isolation system

A study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators is presented. Emphasis is placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase trajectories and frequency response curves were obtained. A semi-empirical model having non-linear stiffness, nth-power velocity damping and variable Coulomb friction damping is developed, and results are compared to experimental data. Conclusions about dynamic phenomena in the wire rope system are made on the basis of the experimental and semi-empirical results.

Evacuation Planning via Evolutionary Computation

According to the Life Safety Codereg, the geometry of a building, the location of exits, and the number of exits dictate the means of egress for all people occupying a building. In this paper we show how evolutionary computations in the form of Genetic Algorithms and Estimation of Distribution Algorithms are used to evolve the placement of exits in order to optimize overall evacuation time. In particular, a generational GA, a steady-state GA, and an elitist EDA are used to evolve the placement of exits for two practical design problems. The algorithms are evaluated in terms of success rate, number of function evaluations, and best fitness. For both problems, the steady-state GA outperformed the other algorithms in all evaluation categories.

Trade Studies for a Manned High -Power Nuclear Electric Propulsion Vehicle

Nuclear electric propulsion (NEP) vehicles will be needed for future manned missions to Mars and beyond. Candidate vehicles must be identified through trade studies for further detailed design from a large array of possibilities. Genetic algorithms have proven their utility in conceptual design studies by effectively searching a large design space to pinpoint unique optimal designs. This research combines analysis codes for NEP subsystems with genetic algorithm-based optimization. Trade studies for a NEP reference mission to the asteroids were conducted to identify important trends, and to determine the effects of various technologies and subsystems on vehicle performance. It was found that the electric thruster type and thruster performance have a major impact on the achievable system performance, and that significant effort in thruster research and development is merited.

Evolving High-Performance Evolutionary Computations for Space Vehicle Design

The nuclear electric vehicle optimization toolset (NEVOT) optimizes the design of all major nuclear electric propulsion (NEP) vehicle subsystems for a defined mission within constraints and optimization parameters chosen by a user. The tool currently uses a number of evolutionary computations (ECs) for designing NEP vehicles. Since evaluating candidate vehicle designs is computationally expensive, it is important that a set of robust control parameters be discovered. In order to accomplish this, a meta-genetic algorithm (meta-GA) was developed to discover control parameters for generational, steady-state, and steady-generational GAs as well as for particle swarm optimizers (PSOs) with ring, star, and random topologies. Our results show that the high-performance GAs are more efficient than the high-performance PSOs on a NASA asteroid mission problem.

Preliminary Design of a Manned Nuclear Electric Propulsion Vehicle Using Genetic Algorithms

Nuclear electric propulsion (NEP) vehicles will be needed for future manned missions to Mars and beyond. Candidate designs must be identified for further detailed design from a large array of possibilities. Genetic algorithms have proven their utility in conceptual design studies by effectively searching a large design space to pinpoint unique optimal designs. This research combined analysis codes for NEP subsystems with a genetic algorithm. The use of penalty functions with scaling ratios was investigated to increase computational efficiency. Also, the selection of design variables for optimization was considered to reduce computation time without losing beneficial design search space. Finally, trend analysis of a reference mission to the asteroids yielded a group of candidate designs for further analysis.

Thermal Analysis and Shape Optimization of an In‐Space Radiator Using Genetic Algorithms

Future space exploration missions will require the development of more advanced in‐space radiators. These radiators should be highly efficient and lightweight, deployable heat rejection systems. Typical radiators for in‐space heat mitigation commonly comprise a substantial portion of the total vehicle mass. A small mass savings of even 5–10% can greatly improve vehicle performance. The objective of this paper is to present the development of detailed tools for the analysis and design of in‐space radiators using evolutionary computation techniques. The optimality criterion is defined as a two‐dimensional radiator with a shape demonstrating the smallest mass for the greatest overall heat transfer, thus the end result is a set of highly functional radiator designs. This cross‐disciplinary work combines shape optimization and thermal analysis design by means of a genetic algorithm. The proposed design tool consists of the following steps; design parameterization based on the exterior boundary of the radiator,...

Germinating the 2050 cis-lunar econosphere

In early 2013, Marshall Space Flight Centers upper management chartered a diverse team for a six-week “sprint” to speculate (in a disciplined manner) and paint (with broad brush strokes) a picture of how earth, space, and public/private entities might be operating and relating to each other... in the year 2100. Two 12-person groups of civil servants, one with members having 15 years or less of NASA experience and the other with more senior members, worked independently and then compared and integrated their conclusions. In 2014, the “Space 2100” team, with some new team members and different group boundaries, ran a longer sprint to a) develop more detailed estimates of the operations and economics of space activities in the vicinity of the Earth and Moon in the 2050 time frame, b) identify evolutionary paths, barriers, and opportunities, and c) suggest actions and philosophies to enable and invigorate progress towards the vision. This paper explores Space 2100s first two sprints and their projections of NASAs role in what will likely be a highly networked, international space industry and cis-lunar infrastructure.

COMPARISON OF METHODS FOR MODAL TESTING OF A SPACE STATION ELEMENT SIMULATOR

Verification of a dynamic model of a constrained structure requires a modal survey test of the physical structure and subsequent modification of the model to obtain the best agreement possible with test data. Constrained-boundary or fixed-base testing has historically been the most common approach for verifying constrained mathematical models, since the boundary conditions of the test article are designed to match the actual constraints in service. However, there are difficulties involved with fixed-base testing, in some cases making the approach impractical. This paper addresses some of those difficulties, and some successes, related to testing the Space Station TestBed Calibration Beam. It also includes an emphasis on the Residual Flexibility Approach.