Michael P. SanSoucie

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.

Containerless Processing Studies in the MSFC Electrostatic Levitator

Levitation or containerless processing represents an important tool in materials research. Levitated specimens are free from contact with a container, which permits studies of deeply undercooled melts, and high-temperature, highly reactive materials. Containerless processing provides data for studies of thermophysical properties, phase equilibria, metastable state formation, microstructure formation, undercooling, and nucleation. Levitation techniques include: acoustic, aero-acoustic, electromagnetic, and electrostatic. In microgravity, levitation can be achieved with greatly reduced positioning forces. Microgravity also reduces the effects of buoyancy and sedimentation in melts. The European Space Agency (ESA) and the German Aerospace Center (DLR) jointly developed an electromagnetic levitator facility (MSL-EML) for containerless materials processing in space. The MSL-EML will be accommodated in the European Columbus Facility on the International Space Station (ISS). The electrostatic levitator (ESL) facility at the Marshall Space Flight Center provides support for the development of containerless processing studies for the ISS. The capabilities of the facility and recent results will be discussed.

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.

Rapid Quench in an Electrostatic Levitator

The Electrostatic Levitation (ESL) Laboratory at the NASA Marshall Space Flight Center (MSFC) is a unique facility for investigators studying high-temperature materials. The ESL laboratory’s main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy, as a quench medium. Thereby allowing rapid quenching of undercooled liquid metals. Up to eight quench vessels can be loaded into a wheel inside the chamber that is indexed with control software. The system has been tested successfully with samples of zirconium, iron-cobalt alloys, iron-chromium-nickel, titanium-zirconium-nickel alloys, and a silicon-cobalt alloy. This new rapid quench system will allow materials science studies of undercooled materials and new materials development. The system is described and some initial results are presented.

Advancements of the Lightweight Integrated Solar Array and Transceiver (LISA-T) Small Spacecraft System

This paper describes recent advancements of the Lightweight Integrated Solar Array and Transceiver (LISA-T) currently being developed at NASAs Marshall Space Flight Center. The LISA-T array comprises a launch stowed, orbit deployed structure on which thin-film photovoltaic (PV) and antenna devices are embedded. The system provides significant electrical power generation at low weights, high stowage efficiency, and without the need for solar tracking. Leveraging high-volume terrestrial-market PVs also gives the potential for lower array costs. LISA-T is addressing the power starvation epidemic currently seen by many small-scale satellites while also enabling the application of deployable antenna arrays. Herein, an overview of the system and its applications are presented alongside sub-system development progress and environmental testing plans.

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,...

Faraday forcing of high-temperature levitated liquid metal drops for the measurement of surface tension

In this work, a method for the measurement of surface tension using continuous periodic forcing is presented. To reduce gravitational effects, samples are electrostatically levitated prior to forcing. The method, called Faraday forcing, is particularly well suited for fluids that require high temperature measurements such as liquid metals where conventional surface tension measurement methods are not possible. It offers distinct advantages over the conventional pulse-decay analysis method when the sample viscosity is high or the levitation feedback control system is noisy. In the current method, levitated drops are continuously translated about a mean position at a small, constant forcing amplitude over a range of frequencies. At a particular frequency in this range, the drop suddenly enters a state of resonance, which is confirmed by large executions of prolate/oblate deformations about the mean spherical shape. The arrival at this resonant condition is a signature that the parametric forcing frequency is equal to the drop’s natural frequency, the latter being a known function of surface tension. A description of the experimental procedure is presented. A proof of concept is given using pure Zr and a Ti39.5Zr39.5Ni21 alloy as examples. The results compare favorably with accepted literature values obtained using the pulse-decay method.Surface tension: picking up good vibrationsA novel method for measuring the surface tension of droplets of liquid metal is developed by researchers in the USA and Japan. Many of the techniques used to investigate the properties of an interface between liquid and air are not applicable to very high temperature fluids. The method now demonstrated by Nevin Brosius, Kevin Ward, and Ranga Narayanan from the University of Florida and collaborators from NASA and Japanese Aerospace Exploration Agency (JAXA), which they call Faraday forcing, employs a continuous periodic electrostatic force that causes a levitating drop to vibrate. The amplitude of these vibrations reaches a maximum when the driving frequency equals the natural frequency of the drop. This value can then be used to calculate the surface tension. The team demonstrate the viability of their technique with pure zirconium and an alloy of titanium, zirconium, and nickel.

Influence of Oxygen on Surface Tension of Zirconium

Zirconium samples with different oxygen concentrations were tested using a ground-based electrostatic levitator at NASA Marshall Space Flight Center. The surface tension of liquid zirconium samples was measured in both undercooled and superheated conditions. The effect of oxygen on surface tension was determined: oxygen in zirconium samples decreases the surface tension of liquid samples, with only a small change in the temperature dependence.