Julie Kleinhenz

COMBUSTION OF NOMEX® III FABRIC IN POTENTIAL SPACE HABITAT ATMOSPHERES: CYCLIC FLAME SPREAD PHENOMENON

Abstract Upward flame spread over Nomex® III fabric was tested in enriched oxygen, reduced pressure atmospheres. These are potential conditions for future space habitat environments. Flammability boundaries as a function of oxygen percentage and pressure were determined experimentally. Upward spread is possible at 24% O2 for pressures as low as 7 psia. For most cases, upward spread is cyclic in nature. A cycle consists of flame growth, flame split, blowoff of the downstream “secondary” flame and re-growth of the upstream “primary” flame. This article presents a detailed description of this interesting and unexpected phenomenon, and suggests that a two-stage solid pyrolysis is its cause.

Development of a Reactor for the Extraction of Oxygen and Volatiles From Lunar Regolith

The RESOLVE (Regolith and Environment Science, Oxygen and Lunar Volatiles Extraction) Project, aims to extract and quantify useful resources from lunar soil. The reactor developed for RESOLVE is a dual purpose system, designed to evolve both water, at 150 C and up to 80 psig, and oxygen, using hydrogen reduction at 900 C. A variety of laboratory tests were performed to verify its operation and to explore the properties of the analog site soil. The results were also applied to modeling efforts which are being used to estimate the apparent thermal properties of the soil. The experimental and numerical results, along with the analog site tests, will be used to evolve and optimize future reactor designs.

Solid fuel combustion experiments in microgravity using a continuous fuel dispenser and related numerical simulations

The conventional way of determining the flammability characteristics of a material involves a number of tedious single-sample tests to distinguish flammable from non-flammable conditions. A novel test device and fuel configuration has been developed that permits multiple successive tests for indefinite lengths of thin solid materials. In this device, a spreading flame can be established and held at a fixed location in front of optimized diagnostics while continuous variations of test parameters are made. This device is especially well-suited to conducting experiments in space (e.g. aboard the International Space Station) where the limited resources of stowage, volume, and crew time pose major constraints. A prototype version of this device was tested successfully in both a normal gravity laboratory and during low-gravity aircraft trials. As part of this ongoing study of material flammability behavior, a numerical model of concurrent-flow flame spread is used to simulate the flame. Two and three-dimensional steady-state forms of the compressible Navier-Stokes equations with chemical reactions and gas and solid radiation are solved. The model is used to assist in the design of the test apparatus and to interpret the results of microgravity experiments. This paper describes details of the fuel testing device and planned experiment diagnostics. A special fuel, developed to optimize use of the special testing device, is described. Some results of the numerical flame spread model are presented to explain the three-dimensional nature of flames spreading in concurrent flow and to show how the model is used as an experiment design tool.

Lunar Resource Utilization: Development of a Reactor for Volatile Extraction from Regolith

The extraction and processing of planetary resources into useful products, known as In- Situ Resource Utilization (ISRU), will have a profound impact on the future of planetary exploration. One such effort is the RESOLVE (Regolith and Environment Science, Oxygen and Lunar Volatiles Extraction) Project, which aims to extract and quantify these resources. As part of the first Engineering Breadboard Unit, the Regolith Volatiles Characterization (RVC) reactor was designed and built at the NASA Glenn Research Center. By heating and agitating the lunar regolith, loosely bound volatiles, such as hydrogen and water, are released and stored in the reactor for later analysis and collection. Intended for operation on a robotic rover, the reactor features a lightweight, compact design, easy loading and unloading of the regolith, and uniform heating of the regolith by means of vibrofluidization. The reactor performance was demonstrated using regolith simulant, JSC1, with favorable results.

An Experimental Investigation of the Apparent Thermal Conductivity of Lunar Regolith Simulant

This paper describes a new apparatus and experimental measurements of the apparent thermal conductivity of the lunar regolith simulant. The apparatus consists of a 50.8 mm ID cylinder with an electric cartridge heater on the centerline, and a porous bottom plate. Ten thermocouples are suspended axially in the cylinder and immersed in the simulant particles. The thermocouple junctions are strategically distributed to measure the radial temperature distribution at an axial location where the temperature field is nearly one-dimensional. The simulant is loaded into the cylinder via an opening on the top plate. The measurement conducted was under ambient pressure, but the apparatus, with minor modification, can be used under vacuum or pressurized environments with or without gas flow. The test results of JSC-1A simulant confirmed the one-dimensionality of the temperature field. An analytical heat conduction model and a regression procedure were used to reduce the experimental data and to develop a correlation describing the apparent thermal conductivity as a function of temperature. The results show that the apparent thermal conductivity of the simulant is highly temperature dependent and decreases with temperature.

Design and Implementation of a Reactor for Extracting Resources from Lunar Regolith

The design and operation of reactors to process lunar regolith for extracting solar wind volatiles, polar water, and the production of oxygen present unique engineering challenges. Because of the harsh conditions, Earth-based approaches to reactor design may not be effective in a lunar environment. In this paper, several design decisions will be discussed, using a small-scale terrestrial reactor breadboard unit as an example. The potential effects on reactor design and performance in the lunar environment, including reduced gravity, vacuum, and large ambient temperature variations will be discussed. The effectiveness of initial approaches to lunar relevant design considerations and earth-based hardware testing will be discussed. I. Introduction xtended duration missions to the moon and mars may substantially benefit from the utilization of in-situ resources to reduce dependency on earth-based transport for resupply of mission consumables. Of primary initial concern is oxygen, first for life support systems, then later for vehicle propellant. Oxygen stored in silicate minerals is plentiful in the lunar regolith and can be extracted using processes such as hydrogen reduction, carbothermal reduction, molten regolith electrolysis, molten salt electrolysis and others. The solar wind and lunar polar cold traps may also yield significant useful resources, including hydrogen and water. Extraction of these resources requires processing the lunar regolith in enclosed volumes, or reactors, in which controlled thermal and chemical processes are conducted. Developing reactor systems for chemical processing of regolith for lunar operation is such an extrapolation of terrestrial experience that an iterative process is needed, first with engineering breadboards to identify and attack the most challenging technical obstacles, then prototype units suitable for environmental and endurance testing. Already, several breadboard level units have been built and tested in laboratory and field environments 1,2,3 . The focus of these systems has been to understand small unit operations such as the flow of material in and out of the reactor and transport mechanisms during the processing operations, as well as the ability to explore integration of the reactors with external material handling and instrumentation hardware, and a variety of operational schemes. Where more than one generation of hardware has been built, some attention has been paid to reducing the system mass, volume, and power characteristics. However, the lunar environment will have a profound impact on many aspects of reactor design; such features must be considered in generations of hardware yet to be built before flight hardware development can be undertaken. Managing the evolution of a substantially new technology can be effectively accomplished by a careful and detailed identification of the technical risks to successful and long-duration operation that may arise during the lifetime of the technology. With the spectrum of risks identified and quantified, they can be systematically reduced through a methodical program of hardware functional testing, lifecycle testing, environmental testing plus simulations intended to link the outcome of the testing activities to the operational situation. Ultimately, the product of the systematic risk reduction activity is a well-understood design envelope for utilization in the building of flight hardware, in this case, for lunar operations.