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After several decades of human spaceflight, the community of space-faring nations has accumulated a diverse and sometimes harrowing history of toxicological events that have plagued human space endeavors almost from the very beginning. Some lessons have been learned in ground-based test beds and others were discovered the hard way - when human lives were at stake in space. From such lessons one can build a risk-management framework for toxicological events to minimize the probability of a harmful exposure, while recognizing that we cannot predict all possible events. Space toxicologists have learned that relatively harmless compounds can be converted by air revitalization systems into compounds that cause serious harm to the crew.

NASA's proposed lunar lander, Altair, will be exposed to vastly different external temperatures following launch till its final destination on the moon. In addition, the heat rejection is lowest at the lowest environmental temperatures (0.5 kW @ 4K) and highest at the highest environmental temperature (4.5 kW @ 215K). This places a severe demand on the radiator design to handle these extreme turn-down requirements. A radiator with digital turn-down capability is currently under study at JPL as a robust means to meet the heat rejection demands and provide freeze protection while minimizing mass and power consumption. Turndown is achieved by independent control of flow branches with isolating latch valves and a gear pump to evacuate the isolated branches. A bench-top test was conducted to characterize the digital radiator concept. Testing focused on the demonstration of proper valve sequencing to achieve turn-down and recharge of flow legs.

In the air conditioning system, flow-induced noise is very disturbing, including the noise generated in the expansion device and the heat exchangers. In the past few decades, most researches related to flow-induced noise focused on the relationship between the flow regimes near the expansion device and the amplitude of flow-induced noise when the measurements are not synched. In this paper, an experimental approach is used to explore the simultaneous relationships between flow-induced noise characteristics and flow regimes at the inlet of TXV of evaporators used in automobiles. A pumped R134a loop with microphones and transparent visualization sections is used to simulate the vapor compression system. Also, the paper evaluates the severity of flow-induced noise from not only the amplitude of noise but also the frequency of noise with a parameter called psychoacoustic annoyance (PA).

This article presents basic separation mechanisms with coalescing/impinging separators studied as the add-on to current popular centrifugal designs. The coalescence and impingement of oil on wire mesh and wave-plates are visualized and tested to investigate the impact of geometry and flow conditions on oil separation efficiency. Re-entrainment phenomenon is explained based on the mass balance. Oil mist flow at the swashplate reciprocating compressor discharge is quantified by video processing method to provide detailed information of the oil droplets. The physics behind oil separator is illustrated by visualization and measurement in this study, which gives useful guidelines for oil separator design and operation. The flow visualization shows the details of oil passing through different oil separation structures. Videos are quantified to provide information like droplet size distribution and liquid volume fraction.

Carbon dioxide (CO2 or R744) is a promising next-generation refrigerant for mobile air-conditioning applications (MAC), which has the advantages of good heating performance in cold climates and environmental-friendly properties. This paper presents a simulation model of an integrated internal heat exchanger (IHX) and accumulator (Acc) using the finite volume method. The results are validated by a group of experimental data collected with different transcritical R744 mobile air-conditioner and heat pump (MHP) systems, and the error was within ±10%. The impacts of refrigerant mass flow rate and operating temperatures on the heat transfer rate of the IHX, improvement on refrigeration capacity and the liquid level in the Acc were studied. Results show that the net benefits of IHX are significant in AC mode, while it helps preventing flooding of the compressor in MHP mode.

Hydrogen fuel is a future energy to solve the problems of energy crisis and environmental pollution. Hydrogen internal combustion engines can combine the advantage of hydrogen without carbon pollution and the main basic structure of the traditional engines. However, the power of the port fuel injection hydrogen engines is smaller than the same volume gasoline engine because the hydrogen occupies the volume of the cylinder and reduces the air mass flow. The turbocharger can increase the power of hydrogen engines but also increase the NOx emission. Hence, a comprehensive controlling strategy to solve the contradiction of the power, BTE and NOx emission is important to improve the performance of hydrogen engines. This paper shows the controlling strategy for a four-stroke, 2.3L hydrogen engine with a turbocharger. The controlling strategy divides the operating conditions of the hydrogen engine into six parts according to the engine speeds and loads.

During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment, the load from the electrical components and incident radiation. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Radiators have no moving parts and are thus simple and highly reliable. However, past freezable radiators have been too heavy.

This paper discusses an advanced computer-based process simulation model to predict cutting forces and surface error (also referred to as the lack of cylindricity) for the cylinder boring process. The model takes into consideration several enhanced features including dual and multiple-cylinder boring, back-boring, boring in the presence of windows/cavities, etc.. The model makes use of a Finite Element product model and the cutting force process model to generate a surface error profile at any axial level in the cylinder bore. A design of experiment approach is employed to study the influence of various process variables on bore surface error. The enhanced process simulation model may be used as a valuable tool in enhancing the simultaneous engineering of products and manufacturing processes.

A system performance study on a portable life support system being developed for use in the Weightless Environment Training Facility (WETF) and the Neutral Buoyancy Laboratory (NBL) has been completed. The Neutral Buoyancy Portable Life Support System (NBPLSS) will provide life support to suited astronauts training for extravehicular activity (EVA) under water without the use of umbilicals. The basic configuration is characterized by the use of medium pressure (200 - 300 psi) cryogen (liquid nitrogen/oxygen mixture) which provides cooling within the Extravehicular Mobility Unit (EMU), the momentum which enables flow in the vent loop, and oxygen for breathing. NBPLSS performance was analyzed by using a modified Metabolic Man program to compare competing configurations. Maximum sustainable steady state metabolic rates and transient performance based on a typical WETF metabolic rate profile were determined and compared.

This paper describes the simulation model of a backhoe excavator. The model uses a prescribed motion cycle and the objective of the program is to determine the power requirements for each of the cylinders as well as the total engine power requirement. Most computer simulations are developed by expressing the differential equations of motion for the system being studied. The known force inputs to the system are applied and the time response of the system is then obtained by numerically integrating the governing differential equations. This paper on the other hand develops the reverse of this. Utilizing a prescribed geometry and trajectory cycle for a linkage system as the input, the program solves for the types of force inputs that are required to achieve that trajectory. With the time dependence of the trajectory known, the total power required and the power required of each cylinder is also evaluated. A typical excavator linkage is shown in Fig. 1.

The presence and distribution of liquid fuel within an engine cylinder at cold start may adversely affect the hydrocarbon emissions from port-injected, spark ignition engines. Therefore, high speed videos of the liquid fuel entry into the cylinder of an optical engine were recorded in order to assess the effect of various engine operating parameters on the amount of liquid fuel inducted into the cylinder, the sizes of liquid drops present and the distribution of the fuel within the cylinder. A 2.5L, V-6, port-injected, spark ignition engine was modified so that optical access is available throughout the entire volume of one of the cylinders. A fused silica cylinder is sandwiched between the separated block and head of the engine and a “Bowditch-type” piston extension is mounted to the production piston. The Bowditch piston has a fused silica crown so that visualization is possible through the top of the piston as well as through the transparent cylinder.

Drop size measurements were performed in the intake port of a motoring engine using a laser diffraction particle sizing technique. The experimental parameters which were varied include number of injection cycles, start of injection timing, engine speed and manifold pressure. Two injectors having different atomization and dispersion characteristics were used in the study, a production dual jet injector which produced Sauter Mean Diameters (SMDs) in the range of 250 to 400 μm and an air assist injector which had a line-of-sight SMD of 39 μm. In measurements with the dual jet injector, after initial injection, the quantity of fuel present in the intake port was observed to increase with each subsequent injection event, reaching a steady state value after 6 to 10 injection cycles. The SMD produced by the back-flow atomization was independent of the number of injection events and independent of engine speed over a range of 750 to 1500 RPM.

The NASA-wide CEV Smart Buyer Team (SBT) was assembled in January 2006 and was tasked with the development of a NASA in-house design for the CEV Crew Module (CM), Service Module (SM), and Launch Abort System (LAS). This effort drew upon over 250 engineers from all of the 10 NASA Centers. In 6 weeks, this in-house design was developed. The Thermal Systems Team was responsible for the definition of the active and passive design architecture. The SBT effort for Thermal Systems can be best characterized as a design architecting activity. Proof-of-concepts were assessed through system-level trade studies and analyses using simplified modeling. This nimble design approach permitted definition of a point design and assessing its design robustness in a timely fashion. This paper will describe the architecting process and present trade studies and proposed thermal designs

In preparation for the contract award of the Crew Exploration Vehicle (CEV), the National Aeronautics and Space Administration (NASA) produced two design reference missions for the vehicle. The design references used teams of engineers across the agency to come up with two configurations. This process helped NASA understand the conflicts and limitations in the CEV design, and investigate options to solve them.

An EVA simulation with a medical contingency scenario was conducted in 2006 with the NASA Haughton-Mars and EVA Physiology System and Performance Projects, to develop medical contingency management and evacuation techniques for planetary surface exploration. A rescue/evacuation system to allow two rescuer astronauts to evacuate one incapacitated astronaut was evaluated. The rescue system was utilized effectively to extract an injured astronaut up a slope of15-25° and into a surface mobility rover for transport to a simulated habitat for advanced medical care. Further research is recommended to evaluate the effects of reduced gravity and to develop synergies with other surface systems for carrying out the contingency procedures.

High costs and extreme risks prevent the life testing of NASA hardware. These unavoidable limitations prevent the determination of sound reliability bounds for NASA hardware; thus the true risk assumed in future missions is unclear. A simulation infrastructure for determining these risks is developed in a configurable format here. Positive preliminary results in preparation for validation testing are reported. A stochastic filter simulates non-deterministic output from the various unit processes. A maintenance and repair module has been implemented with several levels of complexity. Two life testing approaches have been proposed for use in future model validation.

Spacecraft radiators reject heat to their surroundings. Radiators can be deployable or mounted on the body of the spacecraft. NASA's Crew Exploration Vehicle is to use body mounted radiators. Coatings play an important role in heat rejection. The coatings provide the radiator surface with the desired optical properties of low solar absorptance and high infrared emittance. These specialized surfaces are applied to the radiator panel in a number of ways, including conventional spraying, plasma spraying, or as an appliqué. Not specifically designed for a weathering environment, little is known about the durability of conventional paints, coatings, and appliqués upon exposure to weathering and subsequent exposure to solar wind and ultraviolet radiation exposure. In addition to maintaining their desired optical properties, the coatings must also continue to adhere to the underlying radiator panel.

For NASA's Constellation Program, an Intravehicular Activity (IVA) and Extravehicular Activity (EVA) Life Support Umbilical System (LSUS) will be required to provide environmental protection to the suited crew during Crew Exploration Vehicle (CEV) cabin contamination or depressurization and contingency EVAs. The LSUS will provide the crewmember with ventilation, cooling, power, communication, and data, and will also serve as a crew safety restraint during contingency EVAs. The LSUS will interface with the Vehicle Interface Assembly (VIA) in the CEV and the Suit Connector on the suit. This paper describes the effort performed to develop concept designs for IVA and EVA umbilicals, universal multiple connectors, handling aids and stowage systems, and VIAs that meet NASA's mission needs while adhering to the important guiding principles of simplicity, reliability, and operability.

BioSim is a simulation tool which captures many basic life support functions in an integrated simulation. Conventional analyses can not efficiently consider all possible life support system configurations. Heuristic approaches are a possible alternative. In an effort to demonstrate efficacy, a validating experiment was designed to compare the configurational optima discovered by heuristic approaches and an analytical approach. Thus far, it is clear that a genetic algorithm finds reasonable optima, although an improved fitness function is required. Further, despite a tight analytical fit to data, optimization produces disparate results which will require further validation.

During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Last year we reported on the design and initial operational assessment tests of a novel radiator designated the Radiator And Freeze Tolerant heat eXchanger (RAFT-X).