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320 records · Page 18

RoboLab and virtual environments

A useful adjunct to the manned space station would be a self-contained free-flying laboratory (RoboLab). This laboratory would have a robot operated under telepresence from the space station or ground. Long duration experiments aboard RoboLab could be performed by astronauts or scientists using telepresence to operate equipment and perform experiments. Operating the lab by telepresence would eliminate the need for life support such as food, water and air. The robot would be capable of motion in three dimensions, have binocular vision TV cameras, and two arms with manipulators to simulate hands. The robot would move along a two-dimensional grid and have a rotating, telescoping periscope section for extension in the third dimension. The remote operator would wear a virtual reality type headset to allow the superposition of computer displays over the real-time video of the lab. The operators would wear exoskeleton type arms to facilitate the movement of objects and equipment operation. The combination of video displays, motion, and the exoskeleton arms would provide a high degree of telepresence, especially for novice users such as scientists doing short-term experiments. The RoboLab could be resupplied and samples removed on other space shuttle flights. A self-contained RoboLab module would be designed to fit within the cargo bay of the space shuttle. Different modules could be designed for specific applications, i.e., crystal-growing, medicine, life sciences, chemistry, etc. This paper describes a RoboLab simulation using virtual reality (VR). VR provides an ideal simulation of telepresence before the actual robot and laboratory modules are constructed. The easy simulation of different telepresence designs will produce a highly optimum design before construction rather than the more expensive and time consuming hardware changes afterwards.

Giarratano, Joseph C.↗

A Flight Examination of Operating Problems of V/STOL Aircraft in STOL-Type Landing and Approach

A flight investigation has been conducted using a large twin-engine cargo aircraft to isolate the problems associated with operating propeller-driven aircraft in the STOL speed range where appreciable engine power is used to augment aerodynamic lift. The problems considered would also be representative of those of a large overloaded VTOL aircraft operating in an STOL manner with comparable thrust-to-weight ratios. The study showed that operation at low approach speeds was compromised by the necessity of maintaining high thrust to generate high lift and yet achieving the low lift-drag ratios needed for steep descents. The useable range of airspeed and flight path angle was limited by the pilot's demand for a positive climb margin at the approach speed, a suitable stall margin, and a control and/or performance margin for one engine inoperative. The optimum approach angle over an obstacle was found to be a compromise between obtaining the shortest air distance and the lowest touchdown velocity. In order to realize the greatest low-speed potential from STOL designs, the stability and control characteristics must be satisfactory.

Innis, Robert C.↗

Ares Launch Vehicles Development Awakens Historic Test Stands at NASA's Marshall Space Flight Center

This paper chronicles the rebirth of two national rocket testing assets located at NASA's Marshall Space Flight Center: the Dynamic Test Stand (also known as the Ground Vibration Test Stand) and the Static Test Stand (also known as the Main Propulsion Test Stand). It will touch on the historical significance of these special facilities, while introducing the requirements driving modifications for testing a new generation space transportation system, which is set to come on line after the Space Shuttle is retired in 2010. In many ways, America's journey to explore the Moon begins at the Marshall Center, which is developing the Ares I crew launch vehicle and the Ares V cargo launch vehicle, along with managing the Lunar Precursor Robotic Program and leading the Lunar Lander descent stage work, among other Constellation Program assignments. An important component of this work is housed in Marshall's Engineering Directorate, which manages more than 40 facilities capable of a full spectrum of rocket and space transportation technology testing - from small components to full-up engine systems. The engineers and technicians who operate these test facilities have more than a thousand years of combined experience in this highly specialized field. Marshall has one of the few government test groups in the United States with responsibility for the overall performance of a test program from conception to completion. The Test Laboratory has facilities dating back to the early 1960s, when the test stands needed for the Apollo Program and other scientific endeavors were commissioned and built along the Marshall Center's southern boundary, with logistics access by air, railroad, and barge or boat on the Tennessee River. NASA and its industry partners are designing and developing a new human-rated system based on the requirements for safe, reliable, and cost-effective transportation solutions. Given below are summaries of the Dynamic Test Stand and the Static Test Stand capabilities, along with an introduction to the new missions that these sleeping giants will be fulfilling as NASA readies the Ares I for service in the 2015 timeframe, and plans the development work for fielding the Ares V late next decade (fig. 1). Validating modern computer design models and techniques requires the sorts of data that can only be generated by these one-of-a-kind facilities.

Dumbacher, Daniel L.↗

Microbial contamination of spacecraft

Spacecraft and space habitats supporting human exploration contain a diverse population of microorganisms. Microorganisms may threaten human habitation in many ways that directly or indirectly impact the health, safety, or performance of astronauts. The ability to produce and maintain spacecraft and space stations with environments suitable for human habitation has been established over 40 years of human space flight. An extensive database of environmental microbiological parameters has been provided for short-term (< 20 days) space flight by more than 100 missions aboard the Space Shuttle. The NASA Mir Program provided similar data for long-duration missions. Interestingly, the major bacterial and fungal species found in the Space Shuttle are similar to those encountered in the nearly 15-year-old Mir. Lessons learned from both the US and Russian space programs have been incorporated into the habitability plan for the International Space Station. The focus is on preventive measures developed for spacecraft, cargo, and crews. On-orbit regular housekeeping practices complete with visual inspections are essential, along with microbiological monitoring. Risks associated with extended stays on the Moon or a Mars exploration mission will be much greater than previous experiences because of additional unknown variables. The current knowledge base is insufficient for exploration missions, and research is essential to understand the effects of space flight on biological functions and population dynamics of microorganisms in spacecraft. Equally important is a better understanding of the immune response and of human-microorganism-environment interactions during long-term space habitation.

Mir Project↗

Trash to Gas: Converting Space Waste into Useful Supply Products

The cost of sending mass into space with current propulsion technology is very expensive, making every item a crucial element of the space mission. It is essential that all materials be used to their fullest potential. Items like food, packaging, clothing, paper towels, gloves, etc., normally become trash and take up space after use. These waste materials are currently either burned up upon reentry in earth's atmosphere or sent on cargo return vehicles back to earth: a very wasteful method. The purpose of this project was to utilize these materials and create useful products like water and methane gas, which is used for rocket fuel, to further supply a deep space mission. The system used was a thermal degradation reactor with the configuration of a down-draft gasifier. The reactor was loaded with approximately 100g of trash simulant and heated with two external ceramic heaters with separate temperature control in order to create pyrolysis and gasification in one zone and incineration iri a second zone simultaneously. Trash was loaded into the top half of the reactor to undergo pyrolysis while the downdraft gas experienced gasification or incineration to treat tars and maximize the production of carbon dioxide. Minor products included carbon monoxide, methane, and other hydrocarbons. The carbon dioxide produced can be sent to a Sabatier reactor to convert the gas into methane, which can be used as rocket propellant. In order to maximize the carbon dioxide and useful gases produced, and minimize the unwanted tars and leftover ashen material, multiple experiments were performed with altered parameters such as differing temperatures, flow rates, and location of inlet air flow. According to the data received from these experiments, the process will be further scaled up and optimized to ultimately create a system that reduces trash buildup while at the same time providing enough useful gases to potentially fill a methane tank that could fuel a lunar ascent vehicle or other deep space mission.

Tsoras, Alexandra↗

Control and Non-Payload Communications Links for Integrated Unmanned Aircraft Operations

Technology for unmanned aircraft has advanced so rapidly in recent years that many new applications to public and commercial use are being proposed and implemented. In many countries, emphasis is now being placed on developing the means to allow unmanned aircraft to operate within non-segregated airspace along with commercial, cargo and other piloted and passenger-carrying aircraft.In the U.S., Congress has mandated that the Federal Aviation Administration reduce and remove restrictions on unmanned aircraft operations in a relatively short time frame. To accomplish this, a number of technical and regulatory hurdles must be overcome. A key hurdle involve the communications link connecting the remote pilot located at a ground control station with the aircraft in the airspace, referred to as the Control and Non-Payload Communications (CNPC) link. This link represents a safety critical communications link, and thus requires dedicated and protected aviation spectrum as well as national and international standards defining the operational requirements the CNPC system. The CNPC link must provide line-of-site (LOS) communications, primarily through a ground-based communication system, and beyond-line-of-sight (BLOS) communication achieved using satellite communications. In the U.S., the National Aeronautics and Space Administration (NASA) is charged with providing the technical body of evidence to support spectrum allocation requirements and national and international standards development for the CNPC link. This paper provides a description of the CNPC system, an overview of NASA's CNPC project, and current results in technology assessment, air-ground propagation characterization, and supporting system studies and analyses will be presented.

Kerczewski, Robert J.↗

Flight Testing of the TWiLiTE Airborne Molecular Doppler Lidar

In September, 2009 the TWiLiTE (Tropospheric Wind Lidar Technology Experiment) direct detection Doppler lidar was integrated for engineering flight testing on the NASA ER-2 high altitude aircraft. The TWiI,iTE Doppler lidar measures vertical profiles of wind by transmitting a short ultraviolet (355 nm) laser pulse into the atmosphere, collecting the laser light scattered back to the lidar by air molecules and measuring the Doppler shifted frequency of that light. The magnitude of the Doppler shift is proportional to the wind speed of the air in the parcel scattering the laser light. TWiLiTE was developed with funding from the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (11P). The primary objectives of the TWiLiTE program are twofold: 1) to advance the development of key technologies and subsystems critical for a future space based Global 3-1) Wind Mission, as recommended by the National Research Council in the recent Decadal Survey for Earth Science [1] and 2) to develop, for the first time, a fully autonomous airborne Doppler lidar and to demonstrate tropospheric wind profile measurements from a high altitude downward looking, moving platform to simulate spaceborne measurements. In this paper we will briefly describe the instrument followed by a discussion of the results from the 2009 engineering test flights

Gentry, Bruce↗

Smoldering News From STS-77 Endeavour

The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour for its second flight in May 1996, as part of the STS-77 mission. This experiment is part of a series of studies focused on the smolder characteristics of porous combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of this study is to provide a better understanding of the controlling mechanisms of smoldering in microgravity and normal Earth gravity (1g). As with other forms of combustion, gravity affects the availability of air and transport of heat, and therefore, the rate of combustion. The results of the microgravity experiments will be compared with identical ones carried out in 1g. In addition, they will be used to verify present theories of smolder combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvements in fire safety practices. Two smoldering combustion tests with polyurethane foam were successfully accomplished during the STS-77 mission. The tests investigated smoldering combustion in a quiescent (no-flow) enriched oxygen environment, and in an air environment with a 2-mm/sec airflow through the fuel sample. The primary data from the tests are the ignition characteristics, spread rate, smolder reaction temperature, and products of combustion (solid and gas). On both the first mission on STS-69 and the second mission on STS-77, a smolder front propagated the length of the forced-flow samples, with the spread rate between the corresponding upward and downward 1g smolder rates. Neither of the quiescent cases propagated combustion (the first case was due in part to a problem with the experiment electronics). These results show a dramatic difference from the normal gravity results, where smolder propagation is very rapid and complete for both of these conditions. The experiment was conceived by Prof. A. Carlos Fernandez-Pello at the University of California-Berkeley. The MSC hardware was designed and built at the NASA Lewis Research Center by a team of civil servants and contractors from NYMA, Inc., and Aerospace Design & Fabrication, Inc. (ADF). The hardware consists of two sealed aluminum combustion chambers (each being a half a cylinder). The chambers hold the MSC test section, data acquisition electronics, power distribution electronics, and instrumentation. The hardware is fitted into a 5-ft(sup 3) Get-Away-Special (GAS) canister that is mounted in the shuttle cargo bay. The test section consists of a quartz cylinder that contains the polyurethane foam sample and an igniter. This igniter, which is an electrically heated wire sandwiched between two porous ceramic disks, is mounted in contact with the end of the foam sample. An array of 12 thermocouples placed axially and radially along the foam sample provide temperature histories, which are used to determine the rate of smolder propagation, and the characteristics of the reaction.

Koudelka, John M.↗

Hybrid Electric Turboprop Commercial Freighter Opportunity

As the era of electric and hybrid electric aviation is dawning, we have the opportunity to reduce cost, energy use, and emissions of air transportation. In this paper, the case is made for the potential efficiency benefits that can be gained with hybrid electric propulsion. Initial economic, mission profile, and propulsion system concepts for a large turboprop aircraft we designate as the Hybrid Electric Turboprop Commercial Freighter (HETCOF) are presented. Market analysis shows HETCOF has the potential to serve a large market share, but the cost requirements for a new purpose built are challenging relative to the repurposed narrow body aircraft currently operating in the market. Comparing HETCOF to a genericized large turboprop freighter the payload capacity is reduced by 40% for the TRL 5+ configuration but is equivalent to the baseline for the TRL 1-2 configuration. All HETCOF configurations result in increased efficiency and subsequent block fuel, block energy, and block emissions reductions. An integrated power/thermal/and energy storage system is presented and analyzed using key performance parameters to estimate weights and losses at three technology readiness levels. Analysis shows that for a concept like this to have economic and energy benefits, many TRL 1-2 level technologies would be needed. Relevant ARPA-E programs and NASA technologies being developed to enable the benefit are also described. The most significant result of this paper is that the HETCOF concept can close with reduced fuel burn, energy use, and emissions while retaining some or all of the cargo capability of the baseline aircraft across TRL level assumptions, which enables this platform to be used for near term introduction with increasing benefits as technology matures.

Ralph H Jansen↗

NASA Advanced Explorations Systems: Advancements in Life Support Systems

The NASA Advanced Exploration Systems (AES) Life Support Systems (LSS) project strives to develop reliable, energy-efficient, and low-mass spacecraft systems to provide environmental control and life support systems (ECLSS) critical to enabling long duration human missions beyond low Earth orbit (LEO). Highly reliable, closed-loop life support systems are among the capabilities required for the longer duration human space exploration missions assessed by NASA's Habitability Architecture Team (HAT). The LSS project is focused on four areas: architecture and systems engineering for life support systems, environmental monitoring, air revitalization, and wastewater processing and water management. Starting with the international space station (ISS) LSS systems as a point of departure (where applicable), the mission of the LSS project is three-fold: 1. Address discrete LSS technology gaps 2. Improve the reliability of LSS systems 3. Advance LSS systems towards integrated testing on the ISS. This paper summarized the work being done in the four areas listed above to meet these objectives. Details will be given on the following focus areas: Systems Engineering and Architecture- With so many complex systems comprising life support in space, it is important to understand the overall system requirements to define life support system architectures for different space mission classes, ensure that all the components integrate well together and verify that testing is as representative of destination environments as possible. Environmental Monitoring- In an enclosed spacecraft that is constantly operating complex machinery for its own basic functionality as well as science experiments and technology demonstrations, it's possible for the environment to become compromised. While current environmental monitors aboard the ISS will alert crew members and mission control if there is an emergency, long-duration environmental monitoring cannot be done in-orbit as current methodologies rely largely on sending environmental samples back to Earth. The LSS project is developing onboard analysis capabilities that will replace the need to return air and water samples from space for ground analysis. Air Revitalization- The air revitalization task is comprised of work in carbon dioxide removal, oxygen generation and recovery and trace contamination and particulate control. The CO2 Removal and associated air drying development efforts under the LSS project are focused both on improving the current SOA technology on the ISS and assessing and examining the viability of other sorbents and technologies available in academia and industry. The Oxygen Generation and Recovery technology development area encompasses several sub-tasks in an effort to supply O2 to the crew at the required conditions, to recover O2 from metabolic CO2, and to recycle recovered O2 back to the cabin environment. Current state-of-the-art oxygen generation systems aboard space station are capable of generating or recovering approximately 40% of required oxygen; for exploration missions this percentage needs to be greatly increased. A spacecraft cabin trace contaminant and particulate control system serves to keep the environment below the spacecraft maximum allowable concentration (SMAC) for chemicals and particulates. Both passive (filters) and active (scrubbers) methods contribute to the overall TC & PC design. Work in the area of trace contamination and particulate control under the LSS project is focused on making improvements to the SOA TC & PC systems on ISS to improve performance and reduce consumables. Wastewater Processing and Water Management- A major goal of the LSS project is the development of water recovery systems to support long duration human exploration beyond LEO. Current space station wastewater processing and water management systems distill urine and wastewater to recover water from urine and humidity condensate in the spacecraft at a approximately 74% recovery rate. For longer, farther missions into deep space, that recovery rate must be greatly increased so that astronauts can journey for months without resupply cargo ships from Earth.

Shull, Sarah A.↗

NASA: 60 Years and Counting...

Sputnik launched on 4 Oct 1057. On July 29, 1958, Eisenhower signed the National Aeronautics and Space Act, the creation of NASA. The Soviets launched the first human into orbit, Yuri Gagarin, on April 12, 1961. On 5 May 1961, Alan Shepard's Freedom 7 Mercury capsule lifted off at 9:34 a.m. from Launch Complex 5 at Cape Canaveral Air Force Station, and flew a suborbital trajectory lasting 15 minutes and 22 seconds, America's first man in space. On 25 May 1961, Kennedy delivered a speech to a joint session of Congress. In that speech, he stated "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth." The rest, as they say, is history. Project Mercury, the first U.S. program to put humans in space, made 25 flights, six of which carried astronauts between 1961 and 1963. The Gemini program primarily tested equipment and mission procedures and trained astronauts and ground crews for future Apollo missions to the Moon. Exactly eight years, one month and 26 days after President Kennedy challenged Americans to reach for the Moon, Project Apollo landed the first humans on the lunar surface and returned them safely to Earth. In 1973, Skylab expeditions paved the way for the International Space Station. Over 30 years, NASA's space shuttle fleet, ”Columbia, Challenger, Discovery, Atlantis and Endeavour,” flew 135 missions and carried 355 different people to space. The space shuttle carried people into orbit repeatedly; launched, recovered and repaired satellites; conducted cutting-edge research; and built the largest structure in space, the International Space Station. Tragically, NASA lost two crews of seven in the 1986 Challenger accident and the 2003 Columbia accident. The International Space Station is a model for global cooperation and scientific advancements that is enabling growth of private industry in low-Earth orbit and development of new technologies to advance human space exploration. Built between 1998 and 2011, the space station has housed humans continuously since Nov. 2, 2000. NASA has contracted with commercial companies SpaceX, Orbital ATK, and Sierra Nevada Corporation to deliver science investigations, cargo, and supplies to the crews living in space, and soon Boeing and SpaceX will transport astronauts to and from the station. Today, NASA is working on many fronts to advance man's presence in space. NASA's Exploration Campaign will establish U.S. preeminence in cislunar space through the operations and the deployment of a U.S.-led Lunar Orbital Platform-Gateway (LOPG). Together with the Orion and SLS Programs, the LOPG is central to advancing and sustaining human space exploration goals, and is the unifying single stepping off point for human cislunar operations, lunar surface access and missions to Mars. As one might expect, EMC for all this activity is challenging, to say the least. In the next half-hour or so, I will talk about some of those challenges and how the different programs are meeting them.

Scully, Bob↗

Experiments Advance Gardening at Home and in Space

Aeroponics, the process of growing plants suspended in air without soil or media, provides clean, efficient, and rapid food production. Crops can be planted and harvested year-round without interruption, and without contamination from soil, pesticides, and residue. Aeroponic systems also reduce water usage by 98 percent, fertilizer usage by 60 percent, and eliminate pesticide usage altogether. Plants grown in aeroponic systems have been shown to absorb more minerals and vitamins, making the plants healthier and potentially more nutritious. The suspended system also has other advantages. Since the growing environment can be kept clean and sterile, the chances of spreading plant diseases and infections commonly found in soil and other growing media are greatly reduced. Also, seedlings do not stretch or wilt while their roots are forming, and once the roots are developed, the plants can be easily moved into any type of growing media without the risk of transplant shock. Lastly, plants tend to grow faster in a regulated aeroponic environment, and the subsequent ease of transplant to a natural medium means a higher annual crop yield. For example, tomatoes are traditionally started in pots and transplanted to the ground at least 28 days later; growers using an aeroponic system can transplant them just 10 days after starting the plants in the growing chamber. This accelerated cycle produces six tomato crops per year, rather than the traditional one to two crop cycles. These benefits, along with the great reduction in weight by eliminating soil and much of the water required for plant growth, illustrate why this technique has found such enthusiastic support from NASA. Successful long-term missions into deep space will require crews to grow some of their own food during flight. Aeroponic crops are also a potential source of fresh oxygen and clean drinking water, and every ounce of food produced and water conserved aboard a spacecraft reduces payload weight, decreasing launch costs and freeing room for other cargo.

Source record↗

Exploration Systems Development Mission Directorate: Moon to Mars Architecture Definition Document

The National Aeronautics and Space Administration (NASA) explores the unknown in air and space, innovates for the benefit of humanity, and inspires the world through discovery. Extending the reach of humanity through the human exploration of the Moon, Mars, and beyond is key to that mission. NASA’s Moon to Mars Strategy and Objectives document establishes long-term goals and objectives for crewed deep space exploration; however, satisfying NASA’s Moon to Mars Objectives requires an innovative approach to the definition, management, and execution of NASA’s Moon to Mars Architecture. An architecture offers a high-level unifying structure and defines a system. It provides rules, guidelines, and constraints that define a cohesive and coherent framework that identifies constituent parts, relationships, and connections and establishes how those parts fit and work together. This Architecture Definition Document (ADD) establishes the process for the decomposition of objectives empowers the agency’s success in achieving human exploration of the cosmos. NASA updates this document annually to reflect the maturation of the architecture and the progress NASA and partners make toward achieving exploration objectives. The ADD is not a manifest or requirements document. Instead, it serves as a tool for the programs, projects, and engineers who will implement and execute NASA’s bold ambitions for crewed exploration of deep space. As established in the Moon to Mars Strategy and Objectives, “Why” we explore encompasses three pillars: Science, Inspiration, and National Posture. Ensuring success in all three areas requires an architectural approach that incorporates innovation, collaboration, and partnerships that can be sustained across a multi-decadal effort. This second revision (Rev-B) of the ADD, developed to support NASA’s 2024 Architecture Concept Review (ACR), incorporates several key updates to support the continued evolution of the architecture. Since the last revision of the ADD, NASA has significantly improved the clarity of the objective decomposition, which distills exploration objectives into the characteristics and needs and use cases and functions needed to achieve them. The updated decomposition incorporates findings from internal studies and diverse stakeholder feedback. A model-based systems engineering approach ensures coherence and consistency, removing inconsistency and repetition. Revision B also incorporates advancements to NASA’s Mars architecture, including insight into initial capabilities, systems, and operations necessary to support the Humans to Mars segment. Updates to objective decomposition for Mars add significant detail to the ADD and hint at areas of forward work and future study. An appendix adds greater depth in the future decisions needed for Mars that will drive lunar needs. They are not the only decisions to be made, but they will have huge effects on subsequent decisions. NASA continues to introduce new exploration systems into the architecture. Two new elements — initial surface habitat and lunar surface cargo lander—successfully passed mission concept review in 2024 as a result of extensive analysis, concept refinement, and studies. These elements and their respective reference missions appear in this revision. NASA also continues to apply architecture processes to cross-agency efforts and coordination with external stakeholders by including definitions of architecture technology gaps — essential areas for engagement across and beyond the agency. The technology gaps appendix identifies areas that need attention and innovation to enable future exploration. In publishing this information, NASA communicates the technologies and capabilities that may benefit from partnership with industry, academia, other U.S. government agencies, and international space agencies. Ultimately, NASA established the Moon to Mars Architecture approach to communicate and facilitate humanity’s journey into the universe according to the principles and recurring tenets of NASA’s Moon to Mars Strategy and Objectives. The NASA architecture team thanks their many stakeholders, participants, and partners for their efforts to review and provide feedback. Their support has been critical to the success of this approach.

Elements↗

Combined Experimental and Modeling Study of the Interactions of Acid Gas with Common Spacecraft Surfaces for Fire Safety Applications

A fire in a spacecraft poses detrimental consequences and risks mission success in addition to crew safety. This is compounded during long-duration missions when the crew has limited options to recover from a fire. A common spacecraft fire concern is the smoldering of wire insulation, typically made from Polyvinyl chloride (PVC) or Polytetrafluoroethylene (PTFE). This creates acid gases such as Hydrogen Chloride (HCl), Hydrogen Fluoride (HF) and Hydrogen Cyanide (HCN). These poisonous gases are hazardous to the crew. They also interact with common surfaces within the spacecraft more than dominant combustion products such as CO2 and H2O. This makes them more difficult to track for potential fire detection techniques, or for postfire clean-up. It is imperative to be able to understand and predict the fate of these poisonous species in a microgravity environment in order to design a safe vehicle. HCl interacts with a number of materials inside a spacecraft. Primary among these materials is aluminum, which is abundantly used due to its strong and light weight nature. Aluminum has a natural oxide layer that protects it from corrosion but is typically treated to enhance this oxide layer. Among these treatments is a chromate conversion coating (CCC), which provides a thin enough protective oxide layer to still conduct electricity, and a traditional anodized material that has a thicker oxide layer that does not conduct electricity. Nomex is another common material found inside a spacecraft. It is a flame-resistant woven polymer that is related to nylon. This commercially available material is used for cargo storage bags and as a fire barrier. Physics-based models were developed to predict the uptake of HCl by these materials. The ultimate objective of these models is to predict the fate of HCl within the spacecraft so that sensors can be placed in meaningful locations in future missions based on the model predictions. To support these modeling efforts, experiments were performed in a cast acrylic test cell that measured the difference between the inlet and outlet concentration of HCl after inserting a sample rod of the test material. Different uptake capacities were realized for each type of sample tested. A computational fluid dynamics model (CFD) model of the reactor was then constructed that used a one-step global reaction rate with calibratable reaction (or kinetic) constants. These constants were calibrated to match the HCl uptake on the CCC aluminum samples, and the same kinetic constants were then tested for the stock and anodized aluminum samples. Model predictions matched the experimental data for the stock aluminum, and to a much lesser extent, the anodized aluminum. The model was additionally validated at different flow rates, sample surface areas, and inlet concentrations, and showed good agreement for all stock and CCC samples. The model did not accurately predict the HCl uptake in the anodized samples compared to the other two types of aluminum. Adjusting the kinetic constants and transport properties did little to improve the prediction. X-Ray Photoelectron Spectroscopy (XPS) was used to determine that the oxide layer thickness of anodized aluminum is approximately 5,000 nm, compared to 250 nm for CCC and 50 nm for stock. XPS also revealed presence of chlorine further down in the aluminum oxide layer in anodized samples than CCC and stock samples after the samples were saturated with HCl, indicating that accounting for diffusion of HCl into the oxide layer is important for accurate prediction of HCl uptake onto anodized aluminum. Consequently, a multi-scale model was developed and tested. First, a single pore inside the anodized aluminum oxide layer was modeled and is referred to as the pore-scale model. In this model, HCl diffused through the pore and reacted with the aluminum oxide pore wall to create aluminum chloride. The sample was then saturated when the mass transfer resistance through the growing aluminum chloride layer became too large for the HCl to reach the aluminum oxide wall and continue the reaction. This pore-scale model was coupled to the reactor-scale model using a concentration-dependent diffusion coefficient, resulting in much more accurate predictions (approximately half the sum square error of the aforementioned reactor-scale model that produced good agreement for stock and CCC) for a variety of operating conditions. The amount of water vapor or relative humidity (RH) in the flow during a reactor experiment was determined to influence HCl uptake. Experiments were performed to understand the interaction of gaseous HCl with aluminum surfaces in the presence of water vapor. The results show that increasing levels of RH increased the capacity of aluminum to adsorb HCl but decreased the capacity of Nomex to uptake HCl. A series of tests were performed on individual aluminum samples after they had been saturated with a fixed concentration of HCl in dry air conditions with the goal of determining how their HCl uptake capacity changes after various treatments with water relative to the original saturation tests. HCl-saturated aluminum samples subjected to a second dry air flow at the same HCl concentration as the original test had an uptake of 23.5% of the original sample with no treatment in between. Saturated aluminum samples subjected to an air flow with a RH of 90% in between tests had an uptake of 35.6% of the original. Saturated aluminum samples submerged in distilled water for 12 hours in between tests had an uptake of 82.2% of the original sample. Previously saturated aluminum tested with HCl and a 50% RH air flow resulted in similar uptake characteristics in multiple repeated tests. The experiments show the profound effect water vapor has on HCl uptake onto aluminum surfaces. In the samples subjected to water vapor or liquid water, capillary condensation and capillary diffusion alters the transport of HCl significantly. A model was proposed that developed a relationship between RH and the coefficient of HCl diffusion in aluminum chloride. This produced an “S-shaped” curve with diffusion coefficient as a function of RH, with 45% RH represented as the point where the diffusion coefficient is halfway between no water saturation and 100% water saturation in the aluminum chloride product layer. No difference in uptake characteristics for the experiment or model were realized between 50% and 62% RH. The results from the large-scale microgravity experiment, Saffire, are discussed as they pertain to the fate of HCl throughout a spacecraft. HCl was released, both as a standalone event, and in concurrence with the burning of a structured cloth. These events only produced a small response in the far field HCl sensor, while a PMMA burn that did not produce HCl had a significantly greater response. A ground-based large-scale facility was constructed to flow acid gas at the scale and configuration realized in the Saffire experiments. A CFD model of this duct was constructed to test kinetic parameters developed in this work at a larger scale and different geometric configuration and to predict the results of the large-scale facility. The models developed in this work were used to interpret the results of the microgravity tests and lead the discussion on what further experiments and models are needed in order to predict the fate of acid gas in a spacecraft environment. To summarize, the major contributions of this work are as follows: the capacity to uptake HCl, with and without the presence of water vapor, was measured for a variety of real spacecraft surfaces. Several different models (single reactor-scale, multiscale, spacecraft-scale) were developed and with the aid of modeling, the rate of uptake for those surfaces was also predicted and validated. The kinetic parameters determined from the small-scale reactor experiments and models were used to predict large-scale and microgravity tests. Conclusions from this research will be used in the design of spacecraft vehicles and large-scale microgravity fire safety experiments. The models built by this work will aid designers in sensor placement and could be used to predict acid gas transport from fires in partial gravity, as would be seen in Lunar and Martian habitats.

fire safety↗