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Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / Byron W. Jones / Limiting the spread of infectious airborne diseases and airborne pathogens is an important consideration in aircraft environmental control system design. However, when a passenger suspected of having a highly contagious disease or very dangerous disease is identified in flight, it is desirable to further isolate the individual from other passengers. A research project was conducted to explore an isolation system that can be stored in a small space and deployed in flight if needed. This device is referred to as an “Expedient Passenger Isolation System” abbreviated as ISOPASS. The ISOPASS is a portable, negative-pressure isolation system that can be installed over a section of seats quickly by a flight attendant during flight. A prototype proof of concept ISOPASS was evaluated in this study. Measurements were conducted in a full-scale, 11-row mock-up of a wide-body aircraft cabin, as well as a 5-row section of a narrow-body aircraft cabin. Heated mannequins to simulate the thermal load of passengers inside the cabin were seated in the mockup. Carbon dioxide was used as a tracer gas and was mixed with helium to maintain neutral buoyancy in air. The tracer gas was used to simulate airborne pathogen spread and was injected at the breathing level at a seat within the ISOPASS. Tests were conducted with and without the ISOPASS in place. Matched pairs were used to mitigate potential statistical problems. Matched pair tests were completed with gaspers turned on and off. Measurements were repeated three times for each gasper setting and for each ISOPASS condition. Concentration measurements were taken at the breathing level inside the ISOPASS at the seat next to the injection source; at the seat across the aisle adjacent to the ISOPASS; and at a seat far away from the ISOPASS near the front of the cabin. The with- and without-ISOPASS matched pair tests clearly show the ISOPASS prototype is highly effective at providing isolation in each aircraft cabin used in the study. Additionally, it was determined that the use of gaspers makes no measurable difference in the containment effectiveness of the ISOPASS.

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional “validation by test only” mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions. Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must be validated by test data. This research includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available and open source solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT, STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamics model using the iv methodology found in “Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations”. This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System /spacecraft system. Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent, three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions