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Since the mid 1980s, NASA has developed advanced waste management technologies that collect and process waste. These technologies include incineration, hydrothermal oxidation, pyrolysis, electrochemical oxidation, activated carbon production, brine dewatering, slurry bioreactor oxidation, composting, NOx control, compaction, and waste collection. Some of these technologies recover resources such as water, oxygen, nitrogen, carbon dioxide, carbon, fuels, and nutrients. Other technologies such as the Waste Collection System (WCS - the commode) collect waste for storage or processing. The need for waste processing varies greatly depending upon the mission scenario. This paper reviews the waste management technology development activities conducted by NASA since the mid 1980s and explores the drivers that determine the application of these technologies to future missions.

Waste management is a critical component of life support systems for manned space exploration. Human occupied spacecraft and extraterrestrial habitats must be able to effectively manage the waste generated throughout the entire mission duration. The requirements for waste systems may vary according to specific mission scenarios but all waste management operations must allow for the effective collection, containment, processing, and storage of unwanted materials. NASA's Crew Exploration Vehicle usually referred to as the CEV, will have limited volume for equipment and crew. Technologies that reduce waste storage volume free up valuable space for other equipment. Waste storage volume is a major driver for the Orion waste compactor design. Current efforts at NASA Ames Research Center involve the development of two different prototype compactors designed to minimize trash storage space.

Activated carbons have a unique capability of strongly absorbing a great variety of species, ranging from SO2 and NOx, to trace organics, mercury, and other heavy metals. Activated carbons can also be used for gas storage and gas separations, including systems of practical interest to NASA (e.g., CO2/N2/O2), and even for the purification of liquids. No single activated carbon is suitable for all applications, but appreciable control over sorbent properties can be exercised in the process of carbon preparation. Since activated carbons can be produced from a wide range of organic materials, including waste streams, the preparation of activated carbons on board spacecraft should involve a limited amount of additional resources, help manage on-board waste, and reduce the weight of materials to be launched from earth. The feasibility of producing waste-derived activated carbons suitable for SO2 and NO control was the subject of the current study.

Previous research has shown that the homogeneous charge compression ignition (HCCI) combustion concept holds promise for reducing pollutants (i.e. NOx, soot) while maintaining high thermal efficiency. However, it can be difficult to control the operation of the HCCI engines even under steady state running conditions. Power density may also be limited if high inlet air temperatures are used for achieving ignition. A methodology using a small pilot quantity of diesel fuel injected during the compression stroke to improve the power density and operation control is considered in this paper. Multidimensional computations were carried out for an HCCI engine based on a CAT3401 engine. The computations show that the required initial temperature for ignition is reduced by about 70 K for the cases of the diesel pilot charge and a 25∼35% percent increase in power density was found for those cases without adversely impacting the NOx emissions.

Clutches are commonly utilised in passenger type and off-road heavy-duty vehicles to disconnect the engine from the driveline and other parasitic loads. In off-road heavy-duty vehicles, along with fuel efficiency start-up functionality at extended ambient conditions, such as low temperature and intake absolute pressure are crucial. Off-road vehicle manufacturers can overcome the parasitic loads in these conditions by oversizing the engine. Caterpillar Inc. as the pioneer in off-road technology has developed a novel clutch design to allow for engine downsizing while vehicle’s performance is not affected. The tribological behaviour of the clutch will be crucial to start engagement promptly and reach the maximum clutch capacity in the shortest possible time and smoothest way in terms of dynamics. A multi-body dynamics model of the clutch system is developed in MSC ADAMS. The flywheel is introducing the same speed and torque as the engine (represents the engine input to the clutch).

The effects of thermal and chemical aging on the performance of cordierite-based and high-porosity mullite-based diesel particulate filters (DPFs), were quantified, particularly their filtration efficiency, pressure drop, and regeneration capability. Both catalyzed and uncatalyzed core-size samples were tested in the lab using a diesel fuel burner and a chemical reactor. The diesel fuel burner generated carbonaceous particulate matter with a pre-specified particle-size distribution, which was loaded in the DPF cores. As the particulate loading evolved, measurements were made for the filtration efficiency and pressure drop across the filter using, respectively, a Scanning Mobility Particle Sizer (SMPS) and a pressure transducer. In a subsequent process and on a different bench system, the regeneration capability was tested by measuring the concentration of CO plus CO2 evolved during the controlled oxidation of the carbonaceous species previously deposited on the DPF samples.

Mandated pollutant emission levels are shifting light-duty vehicles towards hybrid and electric powertrains. Heavy-duty applications, on the other hand, will continue to rely on internal combustion engines for the foreseeable future. Hence there remain clear environmental and economic reasons to further decrease IC engine emissions. Turbocharged diesels are the mainstay prime mover for heavy-duty vehicles and industrial machines, and transient performance is integral to maximizing productivity, while minimizing work cycle fuel consumption and CO2 emissions. 1D engine simulation tools are commonplace for “virtual” performance development, saving time and cost, and enabling product and emissions legislation cycles to be met. A known limitation however, is the predictive capability of the turbocharger turbine sub-model in these tools.

Fuel properties impact the engine-out emission directly. For some geographic regions where diesel engines can meet emission regulations without aftertreatment, the change of fuel properties will lead to final tailpipe emission variation. Aftertreatment systems such as Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) are required for diesel engines to meet stringent regulations. These regulations include off-road Tier 4 Final emission regulations in the USA or the corresponding Stage IV emission regulations in Europe. As an engine with an aftertreatment system, the change of fuel properties will also affect the system conversion efficiency and regeneration cycle. Previous research works focus on prediction of engine-out emission, and many are based on chemical reactions. Due to the complex mixing, pyrolysis and reaction process in heterogeneous combustion, it is not cost-effective to find a general model to predict emission shifting due to fuel variation.

Equivalent System Mass (ESM) is used by the Advanced Life Support (ALS) community to quantify mission costs of technologies for space applications (Drysdale et al, 1999, Levri et al, 2000). Mass is used as a cost measure because the mass of an object determines propulsion (acceleration) cost (i.e. amount of fuel needed), and costs relating to propulsion dominate mission cost. Mission location drives mission cost because acceleration is typically required to initiate and complete a change in location. Total mission costs may be reduced by minimizing the mass of materials that must be propelled to each distinct location. In order to minimize fuel requirements for missions beyond low-Earth orbit (LEO), the hardware and astronauts may not all go to the same location. For example, on a Lunar or Mars mission, some of the hardware or astronauts may stay in orbit while the rest of the hardware and astronauts descend to the planetary surface.

This project is a Phase III SBIR contract between NASA and Water Reuse Technology (WRT). It covers the redesign, modification, and construction of the Wiped-Film Rotating-Disk (WFRD) evaporator for use in microgravity and its integration into a Vapor Phase Catalytic Ammonia Removal (VPCAR) system. VPCAR is a water processor technology for long duration space exploration applications. The system is designed as an engineering development unit specifically aimed at being integrated into NASA Johnson Space Center's Bioregenerative Planetary Life Support Test Complex (BIO-Plex). The WFRD evaporator and the compressor are being designed and built by WRT. The balance of the VPCAR system and the integrated package are being designed and built by Hamilton Sundstrand Space Systems International, Inc. (HSSSI) under a subcontract with WRT. This paper provides a description of the VPCAR technology and the advances that are being incorporated into the unit.

Homogeneous Charge Compression Ignition (HCCI) has been proposed for natural gas engines in heavy duty stationary power generation applications. A number of researchers have demonstrated, through simulation and experiment, the feasibility of obtaining high gross indicated thermal efficiencies and very low NOx emissions at reasonable load levels. With a goal of eventual commercialization of these engines, this paper sets forth some of the primary challenges in obtaining high brake thermal efficiency from production feasible engines. Experimental results, in conjunction with simulation and analysis, are used to compare HCCI operation with traditional lean burn spark ignition performance. Current HCCI technology is characterized by low power density, very dilute mixtures, and low combustion efficiency. The quantitative adverse effect of each of these traits is demonstrated with respect to the brake thermal efficiency that can be expected in real world applications.

A steady-state system mass balance calculation was performed to investigate design issues regarding the storage and/or processing of solid waste. In the initial stages of BIO-Plex, only a certain percentage of the food requirement will be satisfied through crop growth. Since some food will be supplied to the system, an equivalent amount of waste will accumulate somewhere in the system. It is a system design choice as to where the mass should accumulate in the system. Here we consider two approaches. One is to let solid waste accumulate in order to reduce the amount of material processing that is needed. The second is to process all of the solid waste to reduce solid waste storage and then either resupply oxygen or add physical/chemical (P/C) processors to recover oxygen from the excess carbon dioxide and water that is produced by the solid waste processor.

A slipstream of exhaust from a Caterpillar 3126B engine was diverted into a plasma-catalytic NOx control system in the space velocity range of 7,000 to 100,000 hr-1. The stream was first fed through a non-thermal plasma that was formed in a coaxial cylinder dielectric barrier discharge reactor. Plasma treated gas was then passed over a catalyst bed held at constant temperature in the range of 573 to 773 K. Catalysts examined consisted of γ-alumina, indium-doped γ-alumina, and silver-doped γ-alumina. Road and rated load conditions resulted in engine out NOx levels of 250 - 600 ppm. The effects of hydrocarbon level, catalyst temperature, and space velocity are discussed where propene and in one case ultra-low sulfur diesel fuel (late cycle injection) were the reducing agents used for NOx reduction. Results showed NOx reduction in the range of 25 - 97% depending on engine operating conditions and management of the catalyst and slipstream conditions.

For high-load applications, natural gas represents a clean burning, readily available, and relatively inexpensive alternative to number 2 Diesel fuel. However, the fuel’s poor ignitability has previously limited implementation to spark ignited and dual-fueled engines. These approaches suffer from reduced peak load and high engine-out particulate emissions, respectively, requiring lean operation and expensive aftertreatment to meet regulatory standards. A high-temperature combustion strategy can overcome the difficult ignitibility, allowing for true Diesel-style combustion of pure methane-the least ignitable and least sooting component of natural gas. In order to achieve this result, a compression system was designed to supply fuel at pressures suitably high to achieve good mixing and short injection durations, and a solenoid-actuated Diesel fuel injector was modified to function at these pressures with a gaseous fuel.

Pyrolysis is a very versatile waste processing technology which can be tailored to produce a variety of solid, liquid and/or gaseous products. The pyrolysis processing of pure and mixed solid waste streams has been under investigation for several decades for terrestrial use and a few commercial units have been built for niche applications. Pyrolysis has more recently been considered for the processing of mixed solid wastes in space. While pyrolysis units can easily handle mixed solid waste streams, the dependence of the pyrolysis product distribution on the component composition is not well known. It is often assumed that the waste components (e.g., food, paper, plastic) behave independently, but this is a generalization that can usually only be applied to the overall weight loss and not always to the yields of individual gas species.

Diesel engine downsizing aimed at reducing fuel consumption while meeting stringent exhaust emissions regulations is currently in high demand. The boost system architecture plays an essential role in providing adequate air flow rate for diesel fuel combustion while avoiding impaired transient response of the downsized engine. Electric Turbocharger Assist (ETA) technology integrates an electric motor/generator with the turbocharger to provide electrical power to assist compressor work or to electrically recover excess turbine power. Additionally, a variable geometry turbine (VGT) is able to bring an extra degree of freedom for the boost system optimization. The electrically-assisted turbocharger, coupled with VGT, provides an illuminating opportunity to increase the diesel engine power density and enhance the downsized engine transient response. This paper assesses the potential benefits of the electrically-assisted turbocharger with VGT to enable heavy-duty diesel engine downsizing.

This paper describes work that has begun at Ames Research Center on development of a heat melt compactor that can be used on near term and future missions. The heat melt compactor can handle wastes with a significant plastic composition and minimize crew interaction. The current solid waste management system employed on the International Space Station (ISS) consists of compaction, storage, and disposal. Wastes such as plastic food packaging and trash are compacted manually and wrapped in duct taped “footballs” by the astronauts. Much of the waste is simply loaded into the empty Russian Progress spacecraft that is used to bring supplies to ISS. The progress spacecraft and its contents are intentionally burned up in the earth's atmosphere during reentry. This manual method of trash management on ISS is a wasteful use of crew time and does not transition well to far term missions.

This paper describes two independent studies on γ-alumina as a plasma-activated catalyst. γ-alumina (2.5 - 4.3 wt%) was coated onto the surface of mesoporous silica to determine the importance of aluminum surface coordination on NOx conversion in conjunction with nonthermal plasma. Results indicate that the presence of 5- and 6- fold aluminum coordination sites in γ-alumina could be a significant factor in the NOx reduction process. A second study examined the effect of changing the reducing agent on NOx conversion. Several hydrocarbons were examined including propene, propane, isooctane, methanol, and acetaldehyde. It is demonstrated that methanol was the most effective reducing agent of those tested for a plasma-facilitated reaction over γ-alumina.

On-road comparisons were made between a federal reference method mobile emissions laboratory (MEL) and a portable emissions measurement system (PEMS) to support validation of the engine “Not To Exceed” (NTE) emissions design and to evaluate the accuracy of PEMS. Three different brake specific emissions calculation equations (methods) were used as part of this research, with method one directly using engine speed and torque, and methods two and three including ECM fuel consumption and carbon balance fuel consumption. The brake specific NOx emissions for the particular PEMS unit utilized in this program were consistently higher than those for the MEL. The brake specific (bs) NOx NTE deltas were +0.63±0.31 g/kW-h (0.47±0.23 g/hp-h), +0.55±0.17 g/kW-h (0.41±0.13 g/hp-h), and +0.54±0.17g/kW-h (0.40±0.13g/hp-h) for methods one, two, and three respectively.

Gasoline direct-injection (GDI) engine technology improves vehicle fuel economy while decreasing CO2 emissions. The main drawback of GDI technology is the increase in particulate emissions compared to the commonly used port fuel injection technologies. Today’s adopted strategy to limit such emissions relies upon the use of aftertreatment gasoline particulate filters (GPFs). GPFs reduce particulates resulting from fuel combustion. Soot oxidation (also known as regeneration) is required at regular intervals to clean the filter, maintain a consistent soot trapping efficiency, and avoid the formation of soot plugs in the GPF channels. In this paper, starting from a multiphysics GPF model accounting for mass, momentum, and energy transport, a sensitivity analysis is carried out to choose the best mesh refinement, time step, and relative tolerance to ensure a stable numerical solution of the transport equations during regeneration while maintaining low computational time.