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The objective of this study is to evaluate ventilation efficiency regarding to the International Space Station (ISS) cabin ventilation during the ISS assembly mission 1J. The focus is on carbon dioxide spatial/temporal variations within the Node 2 and attached modules. An integrated model for CO2 transport analysis that combines 3D CFD modeling with the lumped parameter approach has been implemented. CO2 scrubbing from the air by means of two ISS removal systems is taken into account. It has been established that the ventilation scheme with an ISS Node 2 bypass duct reduces short-circuiting effects and provides less CO2 gradients when the Space Shuttle Orbiter is docked to the ISS. This configuration results in reduced CO2 level within the ISS cabin.

The paper presents the results of a CFD study for predictions of ventilation characteristics and convective heat transfer within the Shuttle Orbiter middeck cabin in the presence of seven suited crewmember simulation and Individual Cooling Units (ICU). For two ICU arrangements considered, the thermal environmental conditions directly affecting the ICU performance have been defined for landing operation. These data would allow for validation of the ICU arrangement optimization.

Estimates of the effectiveness of the high-hydrogen containing materials, sodium alanate and ammonia borane, are made by calculating dose and dose equivalent for the 1977 solar minimum and 1970 solar maximum galactic cosmic ray spectra and for the large solar particle event spectra from the space era event of August 1972 and comparing their shielding effectiveness with that of polyethylene.

Solar proton events (SPEs) represent the single-most significant source of acute radiation exposure during space missions. Historically, an exponential in rigidity (particle momentum) fit has been used to express the SPE energy spectrum using GOES data up to 100 MeV. More recently, researchers have found that a Weibull fit better represents the energy spectrum up to 1000 MeV (1 GeV). In addition, the availability of SPE data extending up to several GeV has been incorporated in analyses to obtain a more complete and accurate energy spectrum representation. In this paper we discuss the major SPEs that have occurred over the past five solar cycles (~50+ years) in detail - in particular, Aug 1972 and Sept & Oct 1989 SPEs. Using a high-energy particle transport/dose code, radiation exposure estimates are presented for various thicknesses of aluminum. The effects on humans and spacecraft systems are also discussed in detail.

Statistical Energy Analysis (SEA) is a very powerful tool in its ability to guide noise control package design in automobile, airplane and architectural systems. However transmission loss modeling in an SEA frame work has more to do with modeling of sound propagation through foam and fiber noise control materials than classical SEA power flow between groups of resonant modes. The transmission loss problem is reviewed in an SEA frame work with a focus on key paths and input parameter variations on predicted noise control package performance.

The Carbon Dioxide Removal Assembly (CDRA) is a part of the International Space Station (ISS) Environmental Control and Life Support (ECLS) system. The CDRA provides carbon dioxide (CO2) removal from the ISS on-orbit modules. Currently, the CDRA is the secondary removal system on the ISS, with the primary system being the Russian Vozdukh. Within the CDRA are two Desiccant/Adsorbent Beds (DAB), which perform the carbon dioxide removal function. The DAB adsorbent containment approach required improvements with respect to adsorbent containment. These improvements were implemented through a redesign program and have been implemented on units on the ground and returning from orbit. This paper presents a DAB design modification implementation description, a hardware performance comparison between the unmodified and modified DAB configurations, and a description of the modified DAB hardware implementation into the on-orbit CDRA.

Both humans and onboard radiosensitive systems (electronics, materials, payloads and experiments) are exposed to the deleterious effects of the harsh space radiations found in the space environment. The purpose of this paper is to present the space radiation environment extended to deep space based on environment models for the moon, Mars, Jupiter, and Saturn and compare these radiation environments with the earth's radiation environment, which is used as a comparative baseline. The space radiation environment consists of high-energy protons and electrons that are magnetically “trapped” in planetary bodies that have an intrinsic magnetic field; this is the case for earth, Jupiter, and Saturn (the moon and Mars do not have a magnetic field). For the earth this region is called the “Van Allen belts,” and models of both the trapped protons (AP-8 model) and electrons (AE-8 model) have been developed.

Protecting astronauts from space radiation exposure is an important challenge for mission design and operations for future exploration-class and long-duration missions. Crew members are exposed to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR). If sufficient protection is not provided the radiation risk to crew members from SPEs could be significant. To improve exposure risk estimates and radiation protection from SPEs, detailed evaluations of radiation shielding properties are required. A model using a modern CAD tool ProE™, which is the leading engineering design platform at NASA, has been developed for this purpose. For the calculation of radiation exposure at a specific site, the cosine distribution was implemented to replicate the omnidirectional characteristic of the 4π particle flux on a surface.

Excessive impact pressures can develop when an evacuated system is filled with liquid. Such a process is usually highly chaotic, especially when the system geometry is complex. Available computational methods by themselves cannot provide the necessary answers. The International Space Station (ISS) heat exchanger has a complex flow system, and a synthesis of computational and experimental methods was necessary to design the system. The FLOW-NET two-phase flow program was used to determine the range of loss coefficients and the liquid-vapor interface mass and energy transfer that would fit the measured impact pressures. These loss coefficients could then be used to compute the impact pressures for a design configuration similar to the one tested at a range of operating conditions.

The temperature and humidity of the air within the habitable areas of the International Space Station are controlled by a set of hardware and software collectively referred to as the Temperature and Humidity Control (THC) subassembly. This subassembly 1) controls the temperature of the cabin air based on a crew selected temperature, 2) maintains humidity within defined limits, and 3) generates a ventilation air flow which circulates through the cabin. This paper provides descriptions of the components of the THC subassembly, their performance ranges, and the control approach of the hardware. In addition, the solutions of the design challenges of maintaining a maximum case radiated noise level of NC 45, controlling the cabin air temperature to within ±2°F of a setpoint temperature, and providing a means of controlling microbial growth on the heat exchanger surfaces are described.

Modern aircraft are aerodynamically designed at the edge of flight stability and therefore require high-response-rate flight control surfaces to maintain flight safety. In addition, to minimize weight and eliminate aircraft thermal cooling requirements, the actuator systems have increased power-density and utilize high-temperature components. This coupled with the wide operating temperature regimes experienced over a mission profile may result in detrimental performance of the actuator systems. Understanding the performance capabilities and power draw requirements as a function of temperature is essential in properly sizing and optimizing an aircraft platform. Under the Air Force Research Laboratory's (AFRL's) Integrated Vehicle and Energy Technology (INVENT) Program, detailed models of high performance electromechanical actuators (HPEAS) were developed and include temperature dependent effects in the electrical and mechanical actuator components.

The International Space Station (ISS) uses high efficiency particulate air (HEPA) filters to remove particulate matter from the cabin atmosphere. Known as Bacteria Filter Elements (BFEs), there are 13 elements deployed on board the ISS's U.S. Segment. The pre-flight service life prediction of 1 year for the BFEs is based upon performance engineering analysis of data collected during developmental testing that used a synthetic dust challenge. While this challenge is considered reasonable and conservative from a design perspective, an understanding of the actual filter loading is required to best manage the critical ISS Program resources. Thus testing was conducted on BFEs returned from the ISS to refine the service life prediction. Results from this testing and implications to ISS resource management are discussed. Recommendations for realizing significant savings to the ISS Program are presented.

The Lithium Hydroxide (LiOH) management plan to control carbon dioxide (CO2) for the Shuttle while docked to the International Space Station (ISS) reduces the mass and volume needed to be launched. For missions before Flight UF-1/STS-108, the Shuttle and ISS each removed their own CO2 during the docked time period. To control the CO2 level, the Shuttle used LiOH canisters and the ISS used the Vozdukh or the Carbon Dioxide Removal Assembly (CDRA) with the Vozdukh being the primary ISS device for CO2 removal. Analysis predicted that both the Shuttle and Station atmospheres could be controlled using the Station resources with only the Vozdukh and the CDRA. If the LiOH canisters were not needed for the CO2 control on the Shuttle during the docked periods, then the mass and volume from these LiOH canisters normally launched on the Shuttle could be replaced with other cargo.

The International Space Station (ISS) IATCS (Internal Active Thermal Control System) includes two internal coolant loops that use an aqueous based coolant for heat transfer. A silver salt biocide was used initially as an additive in the coolant formulation to control the growth and proliferation of microorganisms in the coolant loops. Ground-based and in-flight testing has demonstrated that the silver salt is rapidly depleted and not effective as a long-term biocide. Efforts are now underway to select an alternate biocide for the IATCS coolant loop with greatly improved performance. An extensive evaluation of biocides was conducted to select several candidates for test trials.

The Carbon Dioxide Removal Assembly (CDRA) is the primary carbon dioxide removal system located in the United States On-Orbit Segment (USOS) Laboratory module ‘Destiny’ and Node 3 on the International Space Station (ISS). CDRA is housed in a standard ISS rack defined as the Atmosphere Revitalization (AR) rack consisting of the CDRA, Trace Contaminant Control Subassembly and Major Constituent Analyzer. The AR subsystem operation and failure detection are controlled automatically using software that has provisions for override control. This paper will present the blower failure that was experienced during AR rack level and Laboratory ECLS integrated testing. The failure description, failure investigation findings and steps taken to return CDRA to flight will be covered.

In order to conserve mass and volume, it was proposed that the International Space Station (ISS) control the level of carbon dioxide (CO2) in the Space Shuttle Orbiter while the Orbiter is docked to the ISS. If successful, this would greatly reduce the number of lithium hydroxide (LiOH) canisters required for each ISS-related Orbiter mission. Because of the impact on the Orbiter Environmental Control and Life Support Subsystem (ECLSS), as well as on the Orbiter flight manifest, a Space Shuttle Program (SSP) analysis was necessary. STS-108 (ISS UF1) pre-flight analysis using the Personal Computer Thermal Analyzer Program (PCTAP) predicted that the ISS would be able to control the level of CO2 in the Orbiter (and throughout the stack) under nominal conditions with no supplemental LiOH required. This analysis assumed that the Carbon Dioxide Removal Assembly (CDRA) located in the U.S.

Out-of-round holes are formed as a result of tool motion during drilling. Tool vibration is driven by radial and tangential forces on the primary and secondary cutting edges. These forces in turn depend on the chip loads on each cutting edge, which in turn depend on the position of the tool at the current time and at the time of the previous tooth passage. A preliminary analysis based on balancing the cutting forces and the bending forces on the tool, shows that the characteristic frequencies of motion of the tool in the tool frame are near 3/rev, 5/rev, 7/rev etc. (corresponding to 2/rev, 4/rev, 6/rev) in the workpiece frame. These motions are consistent with the tool motion and hole form errors commonly observed on the shop floor. We will describe procedures for measuring the dependence of cutting forces on chip load, the development of simple equations for lateral motion of the tool, and solutions for the tool's behavior.

Since flight requirements often necessitate last-minute re-analysis, it became crucial to develop flexible and comprehensive transport phenomena analysis software that would quickly ensure all vehicle and payload requirements would be satisfied. The software would replace various mainframe-based software, such as the Thermal Radiation Analyzer System (TRASYS) and the Systems Improved Numerical Differencing Analyzer (SINDA). The software would need to have the flexibility to employ models that could be developed and modified as vehicle systems change. By use of event files which contain simple, intuitive commands, the characteristics of individual missions could be built as inputs to the model. By moving the Environmental Control & Life Support (ECLS) system model to the PC environment, each analyst would have execution, storage, and processing management control. And of course, software portability would be greatly increased.

This paper summarizes the first 5 plus years of on-orbit operation for the Major Constituent Analyzer (MCA). The MCA is an essential part of the International Space Station (ISS) Environmental Control and Life Support System (ECLSS). The MCA is a mass spectrometer instrument in the US Destiny Laboratory Module of the International Space Station. The MCA provides critical monitoring of six major atmospheric constituents (nitrogen (N2), oxygen (O2), hydrogen (H2), carbon dioxide (CO2), methane (CH4) and water vapor (H2O)) sampled continuously and automatically in all United States On-Orbit Segment (USOS) modules via the Sample Distribution System (SDS). Sample lines have been routed throughout the U.S. modules with valves to facilitate software-automated sequential sampling of the atmosphere in the various modules.

A flex hose assembly containing aqueous coolant from the International Space Station (ISS) Internal Active Thermal Control System (IATCS) consisting of a 2 foot section of Teflon hose and quick disconnects (QDs) and a Special Performance Checkout Unit (SPCU) heat exchanger containing separate channels of IATCS coolant and iodinated water used to cool spacesuits and Extravehicular Mobility Units (EMUs) were returned for destructive analyses on Shuttle return to flight mission STS-114. The original aqueous IATCS coolant used in Node 1, the Laboratory Module, and the Airlock consisted of water, borate (pH buffer), phosphate (corrosion control), and silver sulfate (microbiological control) at a pH of 9.5 ± 0.5.