This paper focused on two significant space forces that can affect the success of a spacecraft: the radiation and micrometeoroid environments. Both are looked at in the context of the region of space between Earth and Mars. The goal was create reference environments, to provide context to results of environmental modeling, and to provide recommendations to assist in early design decisions of interplanetary spacecraft. The radiation section of this report used NASA's OLTARIS program to generate data for analysis. The area of focus was on the radiation effects for crewed missions, therefore effective dose equivalent was the metric used to compare different models of radiation and shielding. Test spheres with one, two, or three different materials layers were compared, along with modifiers such as alloys or weight vs. thickness emphasis. Results were compared to limits set by the European and Russian Space Agencies to provide context. The results hinged heavily on the intensity of the Solar Particle Events (SPEs), with testing using additional temporary radiation shielding proving to be a requirement for feasible shielding masses. Differences in shield material effectiveness were found to be negligible for thin Galactic Cosmic Rays (GCRs) and thick SPEs. Thick shields were found to perform better when the more efficient shield was on the outside of the test sphere. The micrometeoroid section used equations and programs from multiple sources to generate state vectors, flux, and finally impact models for four different case studies. Impacts v were generated with mass, velocity, and impact angle/location statistics. The mass and velocity results were run through statistical software to generate information such as mean and standard deviation with confidence intervals. Also looked at were higher mass impacts, limited to above 10-3 grams as opposed to above 10-6 for the regular case. The results of this show that very thin monolithic shields (0.1 cm-0.25 cm) could protect against the average 10-6 impact. The Ram, Nadir, and Anti-sun faces received the highest quantity of impacts and Wake received the least. When looking at the worst cases average mass and velocity for the high mass impacts significantly higher shielding was required to prevent penetration (up to 5 cm for some cases). However, the test cases had probabilities of no high mass impacts greater than 46% of the time, with shorter mission having greater chances of no high mass impacts.

An important consideration for spacecraft material selection is the space environment that the spacecraft will be operating in. Two features of the space environment that drive material selection are material outgassing and the presence of atomic oxygen in low Earth orbit (LEO). Materials that are considered for use in space are tested to be able to understand how they’ll outgas on orbit and how they’ll respond to interactions with atomic oxygen. However, testing to understand how atomic oxygen interaction with a material will affect how the material will outgas is rare and not standardized. This thesis used a vacuum chamber intended to determine the outgassing properties of materials using ASTM E595 and another vacuum chamber intended to determine how materials are affected by atomic oxygen using ASTM E2089 to determine how atomic oxygen affects outgassing of silicones, which are of interest as atomic oxygen can alter the chemical composition of the surface of silicones. CV-2500, CV2-2289- 1, and SCV2-2590, three silicone elastomers that are products of NuSil Technology LLC, were tested. Significant trends in atomic oxygen reducing the amount of matter outgassed from these three materials were observed. This can be explained by the conversion of the surface of silicone to silica, which was confirmed using Fourier Transform Infrared (FTIR) spectroscopy. Retesting of these three materials in a chamber designed for ASTM E595 with a temperature measurement system capable of adhering to ASTM E595 to confirm the results of this thesis with more confidence in uniform temperature exposure is recommended.

This report presents an investigation and development of the methods for orbital object identification. Two goals were accomplished in this master’s thesis; the development of a method of inverting material proportions from an object’s combined spectrum, and the investigation of methods and initialization of measurement of space environment effects on spectral features of common spacecraft materials. A constrained least squares approach was chosen for inverting spectral proportions from the combined spectra. The final results fall within 1 - 15% of the original spectrum, depending on the quality and noise levels of the original spectrum. Additionally, the effects of outgassing and atomic oxygen erosion were measured using the vacuum chamber facilities at California Polytechnic State University and are to be used as a basis for future identification of orbital debris. To have a fully functional model for accurately identifying space objects, both parts are needed: a set of space environment effect measurements as a basis for the identification model (for use on objects exposed to the space environment), and the identification model to mathematically determine the best fit set of materials.

Additive manufacturing (AM) is a rapidly developing manufacturing method utilized in fields such as the aerospace industry. In-space AM is a technology of interest for the future of spaceflight, including on-orbit manufacturing. However, AM materials are subject to defects that may impact their performance in space-based applications. How these defects change the material’s reaction to the space environment, specifically atomic oxygen (AO), has only recently been explored. AO is a highly corrosive, dominant constituent in low Earth orbit that causes continuous erosion of spacecraft surfaces. The effect of AO on various AM materials is investigated in this thesis. Stainless steel, aluminum, ULTEM™, and titanium samples made using differing AM techniques were exposed to 24 hours of AO in order to calculate material susceptibility in the form of erosion yield. Additionally, reflectance spectra were collected to detect changes in material at the surface. Over 24 hours, samples were exposed to an average fluence of 9.10 × 1020 atoms cm−2, equating to about 200 times the naturally occurring AO flux at International Space Station altitudes. The statistical significance of effects from AO exposure were determined. Comparisons were drawn between the AM materials tested and conventionally manufactured materials. It was found that mass loss due to AO erosion was significant for ULTEM™, powder bed fusion titanium, and directed energy deposition titanium. The ULTEM™ tested in this thesis had significantly higher erosion yield when compared to ULTEM™ tested by NASA, while all other material comparisons had insufficient evidence to draw similar conclusions. Reflectance spectra did not reveal unexpected differences before and after exposure.

Over the past century, great strides have been made in the advancement of mine fire knowledge since the 1909 Cherry Mine Fire Disaster, one of the worst in U.S. history. However, fire hazards remain omnipresent in underground coal mines in the U.S. and around the world. A precise fire numerical analysis (simulation) before any fire events can give a broad view of the emergency scenarios, leading to improved emergency response, and better health and safety outcomes. However, the simulation cost of precise large complex dynamical systems such as fire in underground mines makes practical and even theoretical application challenging. This work details a novel methodology to reduce fire and airflow simulation costs in order to make simulation of complex systems around fire and mine ventilation systems viable. This study will examine the development of a Reduced Order Model (ROM) to predict the flow field of an underground mine geometry using proper orthogonal decomposition (POD) to reduce the airflow simulation cost in a nonlinear model. ROM proves to be an effective tool for approximating several possible solutions near a known solution, resulting in significant time savings over calculating full solutions and suitable for ensemble calculations. In addition, a novel iterative methodology was developed based on the physics of the fluid structure, turbulent kinetic energy (TKE) of the dynamical system, and the vortex dynamics to determine the interface boundary in multiscale (3D-1D) fire simulations of underground space environments. The proposed methodology was demonstrated to be a useful technique for the determination of near and far fire fields, and could be applied across a broad range of flow simulations and mine geometries. Moreover, this research develops a methodology to analyze the tenable limits in a methane fire event in an underground coal mine for bare-faced miners, mine rescue teams, and fire brigade teams in order to improve safety and training of personnel trained to fight fires. The outcomes of this research are specific to mining although the methods outlined might have broader impacts on the other fields such as tunneling and underground spaces technology, HVAC, and fire protection engineering industries. / Ph. D. / With the rapid advancement of technology, the mine fire knowledge has progressed significantly. Atmospheric monitoring and early sensing of heating has improved; the numerical analysis has been expedited with the usage of supercomputers, and more regulations and standards have been set to increase health and safety of miners. In spite of advancements in these areas, fire hazards remain a critical hazard in underground mines. Developing an emergency plan for the safe escape and for fighting the fire is one of the most important issues during a fire event in underground space environments such as mines. A precise fire numerical analysis (simulation) before any fire events can give a broad view of the emergency situation that leads to improving the health and safety issues in the mining industry. Unfortunately, the precise simulation of the large complex dynamical system such as a fire in underground spaces is costly. This work details a cutting edge approach to reduce the fire and airflow simulation costs in order to make simulation of complex systems around fire and mine ventilation systems viable. The main focus of this proposal is to develop novel methodologies to decrease the time of the fire and airflow simulations. The developed methodologies prove to be useful techniques for the reduction of fire simulation and airflow simulation costs. In addition, this study will examine the development of a comprehensive methodology to analyze the tenable limits in a fire event in an underground coal mine in order to improve safety and training of personnel trained to fight fires. These simulations, applied to training, will result in more efficient evacuations (e.g., the decision to leave can be made quickly and with less delay), as well as safe and effective firefighting under certain situations. The target of this research is specific to mining industry although the methods outlined might have broader impacts on the other fields such as tunneling and underground spaces technology, HVAC, and fire protection engineering industries. Therefore, this research may have an immense contribution on the improvement of health and safety associated with firefighting.

This thesis evaluates the suitability of silicon-germanium technology for electronic systems intended for extreme environments, such as ambient temperatures outside of military specification (-55 degC to 125 degC) range and intense exposures to ionizing radiation. Silicon-germanium devices and circuits were characterized at cryogenic and high-temperatures (up to 300 degC) and exposed to ionizing radiation, providing empirical evidence that silicon-germanium is an excellent platform for terrestrial and space-based electronic applications.