Tech Briefs

Film/Adhesive Processing Module for Fiber-Placement Processing of Composites

Films, foils, or adhesives may be interleaved while fiber-placing composite material structures.

An automated apparatus has been designed and constructed that enables the automated lay-up of composite structures incorporating films, foils, and adhesives during the automated fiberplacement process. This apparatus, denoted a film module, could be used to deposit materials in film or thin sheet form either simultaneously when laying down the fiber composite article or in an independent step. Examples of materials that may be processed with this device include structural core and joining adhesives, permeation barrier films/foils, surfacing films, lightning-strike materials and IVHM (Integral Vehicle Health Monitoring) arrays. The use of this technology will reduce composite fabrication time and will allow for new concepts/ designs to be considered for fiber-placed composite structures.

Posted in: Briefs, Manufacturing & Prototyping, Adhesives and sealants, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Composite materials

Radiation-Shielding Polymer/Soil Composites

Radiation shields could be fabricated in situ at relatively low cost.

It has been proposed to fabricate polymer/soil composites primarily from extraterrestrial resources, using relatively lowenergy processes, with the original intended application being that habitat structures constructed from such composites would have sufficient structural integrity and also provide adequate radiation shielding for humans and sensitive electronic equipment against the radiation environment on the Moon and Mars. The proposal is a response to the fact that it would be much less expensive to fabricate such structures in situ as opposed to transporting them from Earth.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Soils, Composite materials, Polymers, Radiation protection

Statistical Model of Evaporating Multicomponent Fuel Drops

This model overcomes a deficiency of a prior statistical model.

An improved statistical model has been developed to describe the chemical composition of an evaporating multicomponent- liquid drop and of the mixture of gases surrounding the drop. The model is intended for use in computational simulations of the evaporation and combustion of sprayed liquid fuels, which are typically mixtures of as many as hundreds of different hydrocarbon compounds. Since an exact model providing a detailed account of all of the compounds would be computationally intractable, the present statistical model is an approximation designed to afford results that are accurate enough to contribute to understanding of the simulated physical and chemical phenomena, without imposing an unduly large computational burden.

Posted in: Briefs, TSP, Physical Sciences, Computational fluid dynamics, Statistical analysis, Chemicals, Gases, Fuel injection

Electrochemical Disposal of Hydrazines in Water

This method offers advantages of safety, economy, and scalability.

An electrochemical method of disposal of hydrazines dissolved in water has been devised. The method is applicable to hydrazine (N2H4), to monomethyl hydrazine [also denoted by MMH or by its chemical formula, (CH3)HNNH2], and to unsymmetrical dimethyl hydrazine [also denoted UDMH or by its chemical formula, (CH3)2NNH2]. The method involves a room-temperature process that converts the hydrazine to the harmless products N2, H2O, and, in some cases, CO2. In comparison with prior methods of disposing of hydrazines, the present method is safer and less expensive.

Posted in: Briefs, Physical Sciences, Water treatment, Hydrazines, Chemicals

Resistively Heated SiC Nozzle for Generating Molecular Beams

This nozzle is more durable and efficient relative to its predecessors.

An improved nozzle has been developed to replace nozzles used previously in an apparatus that generates a substantially unidirectional beam of molecules passing through a vacuum at speeds of several kilometers per second. The need to replace the previous nozzles arose from a complex set of causes that can be summarized as follows:

The previous nozzles had short operational lifetimes because it was necessary to fabricate them from components made of several different materials that, when used together, do not last long at the high operating temperatures needed to generate the requisite high molecular speeds and To protect the vacuum chamber from excessive heating, it was necessary to surround the operating nozzle with a cooling shroud that robbed the nozzle of reflected heater power and thereby contributed to energy inefficiency.
Posted in: Briefs, TSP, Physical Sciences, Nozzles

Modeling Evaporation of Drops of Different Kerosenes

One model applies to all three classes of hydrocarbon constituents.

A mathematical model describes the evaporation of drops of a hydrocarbon liquid composed of as many as hundreds of chemical species. The model is intended especially for application to any of several types of kerosenes commonly used as fuels. Like evaporating- multicomponent- fuel-drop models described in several previous NASA Tech Briefs articles, the present model invokes the concept of continuous thermodynamics, according to which the chemical composition of the evaporating multicomponent liquid is described by use of a probability distribution function (PDF). However, as described below, the present model is more generally applicable than is its immediate predecessor.

Posted in: Briefs, TSP, Information Sciences, Computational fluid dynamics, Mathematical models, Hydrocarbons, Thermodynamics, Thermodynamics, Gases

A Robustly Stabilizing Model Predictive Control Algorithm

The algorithm can be applied to industrial and automotive systems.

A model predictive control (MPC) algorithm that differs from prior MPC algorithms has been developed for controlling an uncertain nonlinear system. This algorithm guarantees the resolvability of an associated finite-horizon optimal-control problem in a recedinghorizon implementation. Given a feasible solution to the finite-horizon optimal control problem at an initial time, resolvability implies the ability to solve the optimal control problem at subsequent times.

Posted in: Briefs, TSP, Information Sciences, Mathematical models

Development of Vapor-Phase Catalytic Ammonia Removal System

A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars. The VPCAR process is implemented by a system of highly integrated design in which some power consumption is accepted as a cost of minimizing the volume and mass of a wastewater-processing system and eliminating the need to resupply water. The core of the system is a wiped-film rotating-disk (WFRD) evaporator, which removes inorganic salts and nonvolatile organic compounds from the wastewater stream and concentrates these contaminants into a recycle-and-bleed stream. The WFRD evaporator is also part of a subsystem that distills water from the wastewater stream. This subsystem operates in a vacuum-vapor/compression distillation configuration in the temperature range from 20 to 65 °C. Volatile organic compounds and ammonia, distilled along with water, are oxidized to CO2, H2O, and N2O in a packed-bed, hightemperature catalytic reactor placed at the outlet of the vapor-phase compressor of the distillation subsystem. A VPCAR engineering demonstration unit is expected to be included in a humanrated simulation of a mission to Mars.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Waste management, Water pollution, Water treatment, Spacecraft

Several Developments in Space Tethers

Five reports address different aspects of development of tethers to be deployed from spacecraft in orbit around the Earth. The first report discusses proposed optoelectronic tracking of retroreflective objects located at intervals or of retroreflective coats along the entire length of a tether to measure lateral motions. The second report describes digitally controlled spooling machinery that retracts or extends a tape tether at controlled speed and tension in the spool isolated from uncontrolled tension on the outside. The third report discusses part of this machinery that pivots to accommodate misalignments between the deployed and spooled portions of the tether and contains rollers used to exert tension and speed control. The fourth report discusses aspects of designs of proposed electrodynamic tethers, which would be electrically conductive and would interact with the magnetic field of the Earth to exert forces to modify orbits of deploying spacecraft. The fifth report discusses electrical aspects of designs of electrodynamic tape tethers, including the use of solar cells or motional electromagnetic force to generate currents in tethers and the use of electron emitters and electron and ion collectors at opposite ends of tethers to make electrical contact with the thin plasma in surrounding space.

Posted in: Briefs, Mechanical Components, Mechanics, Spacecraft

Design Concept for a Nuclear Reactor-Powered Mars Rover

A report presents a design concept for an instrumented robotic vehicle (rover) to be used on a future mission of exploration of the planet Mars. The design incorporates a nuclear fission power system to provide long range, long life, and high power capabilities unachievable through the use of alternative solar or radioisotope power systems. The concept described in the report draws on previous rover designs developed for the 2009 Mars Science laboratory (MSL) mission to minimize the need for new technology developments.

Posted in: Briefs, TSP, Mechanical Components, Mechanics, Design processes, Nuclear energy, Robotics, Autonomous vehicles

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