The payload environment of a rocket is random and dynamic during liftoff and flight, with acoustic noise, vibration, and acceleration falling under its definition. Characterization of this environment is important to finalize payload design requirements and insure mission completion. This report will focus on the study and measurement of acoustic noise using a low-cost microphone. Various spectral analysis techniques were utilized to characterize acoustic intensities and frequency content. Effects of vibration and acceleration, ground reflection, atmospheric absorption, and nonlinear propagation were investigated. Noise data were obtained from a rocket launch and several vertical, staticired hybrid motors. The propulsion system acoustic loads were compared to prediction methods from NASA SP-8072.

In this thesis, the design and particularities of a unique and revolution- ary scalable propulsion system are presented. A spacecraft mechanical design is included together with a mission definition, aiming to provide a context for a technology demonstration in space of an Hybrid Rocket Motor (HRM) as satellite thruster. Rocket motors have been around for many decades, with their use mainly focused on launch vehicles and large satellites, thus restricting the access to space to institutions with big budgets. To overcome this limitation, the application of a cost-effective type of rocket motor without a heritage of space utilization is explored. This is the implementation of an HRM as satellite thruster. In Chapter 2, the characteristics of this particular case of chemical rocket motor are presented in detail. The HRM applied for the present mission is a particular case of an in- house developed motor design method. As presented in Chapter 7, a scalable and versatile mechanical and propulsion design have been elab- orated following the maturation of a scalability software (Appendix A). The combination of these constitute a valuable tool allowing for a fast and accurate motor design for the desired scenario. Taking advantage of this straightforward tool, an attractive mission was defined to provide a meaningful context for the maiden use of an HRMin space. A micro satellite deep space mission, defined in Chapter 3, was chosen to validate the tool and prove Hybrid Rocket Motors (HRMs) capabilities, showing the benefits of its use over other propulsion systems already available, specifically in the small satellite family. The spacecraft design was tackled aiming to support the motor’s scalable concept while complying with the mission requirements and space standards. The out- come is an easily adaptable satellite design, justified in Chapter 8. The performed structural simulations are outlined in Appendix C to validate the developed design. Ultimately, this thesis work intends to provide the space community with a noteworthy product, opening the access to interplanetary missions provided the reduced mission costs of small satellites mounted with anHRM as propulsion system. Arising from the thesis content, research papers (Part v) have been published and presented in distinguished congresses, contributing to space development.

Using the Debye-Huckle approximation, the effects of Coulomb interactions on the equilibrium, frozen, and nonequilibrium flow of an ionized gas have been investigated. The gas is assumed to be monatomic, electrically neutral, and thermal equilibrium (i.e., a one temperature fluid); but the composition of the gas is arbitrary, that is, multiple ionization of any degree is allowed. The thermodynamic variables are derived starting from the appropriate expression for the Helmholtz free energy. Using Boltzmann statistics and assuming that the velocity distribution functions are given by their Maxwellian values, the rate of ionization is derived for atom-atom, atom-ion, and atom-electron collisions. The resulting expressions are then employed in solving the quasi-one-dimensional flow in a converging-diverging nozzle for the equilibrium, frozen, and nonequilibrium cases. Numerical examples, using argon as the working substance, are discussed and the results presented graphically. The results of these calculations indicate that, for single ionization, the effect of Coulomb interactions on the performance of rocket engines is negligible; but that data obtained from hypersonic arc jet wind-tunnels can be significantly influenced by the presence of the interactions. / Ph. D.

The analysis and redesign of a centrifugal impeller for a rocket pump is presented in this thesis. A baseline impeller was designed by Rocketdyne for the NASA Marshall Pump Consortium. Initially, the objective was to reduce the circumferential exit flow distortion of the baseline impeller. Later in the study, the objective became raising the head coefficient of the impeller. The study presented in this thesis was also undertaken to demonstrate current CFD capabilities for impeller design. A literature review includes an overview of centrifugal impeller geometries and configurations. Centrifugal impeller performance and secondary flows are discussed, and a summary of studies on the effects of impeller exit and diffuser inlet velocity distortion on diffuser performance is also presented. The flow calculation details and the results of the baseline impeller flow calculations are described. Fourteen redesigned impeller geometries were analyzed using the Moore Elliptic Flow Program, and the results were compared to the baseline geometry in terms of head rise, losses, and exit flow distortions. A final geometry was chosen; this geometry will be built and tested by Rocketdyne. The results show that backward blade lean can be effective in red using the exit flow distortion of the impeller. Tip slots or holes were not beneficial because of the large inlet boundary layer. Also, it appears possible to raise the head coefficient of the baseline impeller without creating excessive flow distortion. The planned testing is necessary to verify the predictions of the flow code. / Master of Science

In 2023, the U.S. House of Representatives, newly under Republican control, sought to limit federal spending, creating a potentially dangerous situation for American space exploration and NASA. Given the budget situation, it may be beneficial for NASA to look to its existing geographic footprint for areas of deeper support to provide elected leaders with an electoral justification to support NASA missions. The areas with the greatest chance of generating support for NASA are spaceports due to the rocket launches they support serving as focusing events for NASA. Rather than focusing as past scholars have on specific regions, this research examines driving distance from the Kennedy Space Center to provide more detail about the possible relationship between geographic proximity to spaceports and views of NASA. To test for the existence of this proximal relationship and the impact of viewing rocket launches on opinions of NASA, the study fielded an original online survey to gather U.S. residents' opinions about NASA, as well as information on where they lived and on how frequently they view rocket launches. Employing bivariate and multivariate regression models, the responses were analyzed to explore the relationship between geographic proximity to the primary spaceport and exposure to rocket launches on respondents' reported views of NASA. This study found that as respondents' distance from the Kennedy Space Center increased, positive views of NASA decreased. Additionally, respondents who viewed the launch of NASA's Space Launch System (SLS) rocket had more positive views of the agency than others. Overall, these results indicate that direct exposure to NASA activities, facilitated either by living near the Kennedy Space Center or by viewing the SLS launch is associated with more positive perceptions of NASA. The hypothesis that rocket launches can impact views of space exploration was supported based on analyses of reported online and in-person viewership that suggested notable relationships with opinions of commercial launch providers. Yet, even though the models found support for this relationship, they suggested that other factors likely are also important to fully understanding the relationship. NASA's future public engagement strategies evidently should focus on narrowing the awareness gap of NASA activities for those further away from spaceports and do not have direct exposure to the agency. / Master of Arts / In 2023, the U.S. House of Representatives, newly under Republican control, sought to limit federal spending, creating a potentially dangerous situation for American space exploration and NASA. Given the budget situation, it may be beneficial for NASA to look to its existing geographic footprint for areas of deeper support to provide elected leaders with an electoral justification to support NASA missions. The areas with the greatest chance of generating support for NASA are spaceports due to the rocket launches they support serving as potential advertisements for NASA. Rather than focusing as past scholars have on specific regions, this research examines driving distance from the Kennedy Space Center to provide more detail about the possible relationship between geographic proximity to spaceports and views of NASA. Additionally, given that the impact of rocket launches on support for NASA has not been measured this study can help quantify support for NASA's most visible public events. To test for the existence of this relationship and the impact of viewing rocket launches on opinions of NASA, the study fielded an original online survey to gather U.S. residents' opinions about NASA, as well as information on where they lived and on how frequently they view rocket launches. Regression analyses are used to determine the impact of distance from the Kennedy Space Center and different modes of viewership of rocket launches on opinions of NASA. This study found that as respondents' distance from the Kennedy Space Center increased positive views of NASA decreased. Additionally, respondents who viewed the launch of NASA's Space Launch System (SLS) rocket had more positive views of the agency. Overall, these results indicate that direct exposure to NASA activities facilitated either by living near the Kennedy Space Center or by viewing the SLS launch can increase positive perceptions of NASA. NASA's future public engagement strategies evidently should focus on narrowing the awareness gap of NASA activities for those further away from spaceports and do not have direct exposure to the agency.

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The adoption of 5G mobile networks is changing the way we connect our world. Now, it is not just phones that are connected to the network, it is everything - smart homes, self-driving cars, factory equipment, and anything in between. Because of this, there has been a large increase in the volume and complexity of mobile network traffic in recent years. As 5G becomes more widely adopted, this trend will continue moving forward. This presents a problem for mobile network operators. To account for this increase in traffic volume and complexity, the network must be optimized to handle it. However, the only way to do this is to better understand the traffic sent over the network. As such, the companies building and operating these networks rely on models that can define a set of traffic profiles from real-world network data. This thesis presents a novel method of identifying traffic profiles from 5G network data by analyzing the network traffic as unstructured time series data. Using two datasets containing TCP and UDP traffic data with 10 million time series apiece, clusters were defined for each using time series clustering techniques. Specifically, the ROCKET family of algorithms was adapted for clustering purposes, applying k-means clustering on top of the ROCKET feature transformations. The resulting clusters were analyzed and compared to another clustering model - one based on summary statistics from each time series. Overall, the ROCKET models appeared to produce more coherent traffic profiles compared to the baseline clustering model, and the proposed framework shows great promise - not just in network traffic clustering, but any analysis of unstructured time series data.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Grain regression analysis forms an essential part of solid rocket motor simulation. In this thesis a numerical grain regression analysis module is developed as an alternative to cumbersome and time consuming analytical methods. The surface regression is performed by the level-set method, a numerical interface advancement scheme. A novel approach to the integration of the surface area and volume of a numerical interface, as defined implicitly in a level-set framework, by means of Monte-Carlo integration is proposed. The grain regression module is directly coupled to a quasi -1D internal ballistics solver in an on-line fashion, in order to take into account the effects of spatially varying burn rate distributions. A multi-timescale approach is proposed for the direct coupling of the two solvers. / AFRIKAANSE OPSOMMING: Gryn regressie analise vorm ’n integrale deel van soliede vuurpylmotor simulasie. In hierdie tesis word ’n numeriese gryn regressie analise model, as ’n alternatief tot dikwels omslagtige en tydrowende analitiese metodes, ontwikkel. Die oppervlak regressie word deur die vlak-set metode, ’n numeriese koppelvlak beweging skema uitgevoer. ’n Nuwe benadering tot die integrasie van die buite-oppervlakte en volume van ’n implisiete numeriese koppelvlak in ’n vlakset raamwerk, deur middel van Monte Carlo-integrasie word voorgestel. Die gryn regressie model word direk en aanlyn aan ’n kwasi-1D interne ballistiek model gekoppel, ten einde die uitwerking van ruimtelik-wisselende brand-koers in ag te neem. ’n Multi-tydskaal benadering word voorgestel vir die direkte koppeling van die twee modelle.

The present research project is carried out at the von Karman Institute for Fluid Dynamics (Rhode-Saint-Genèse, Belgium) with the financial support of the European Space Agency. The first stage of spacecrafts (e.g. Ariane 5, Vega, Shuttle) generally consists of large solid propellant rocket motors (SRM), which often consist of segmented structure and incorporate a submerged nozzle. During the combustion, the regression of the solid propellant surrounding the nozzle integration part leads to the formation of a cavity around the nozzle lip. The propellant combustion generates liquefied alumina droplets coming from chemical reaction of the aluminum composing the propellant grain. The alumina droplets being carried away by the hot burnt gases are flowing towards the nozzle. Meanwhile the droplets may interact with the internal flow. As a consequence, some of the droplets are entrapped in the cavity forming an alumina puddle (slag) instead of being exhausted through the throat. This slag reduces the performances. The aim of the present study is to characterize the slag accumulation process in a simplified model of the MPS P230 motor using primarily optical experimental techniques. Therefore, a 2D-like cold-gas model is designed, which represents the main geometrical features of the real motor (presence of an inhibitor, nozzle and cavity) and allows to approximate non-dimensional parameters of the internal two-phase flow (e.g. Stokes number, volume fraction). The model is attached to a wind-tunnel that provides quasi-axial flow (air) injection. A water spray device in the stagnation chamber realizes the models of the alumina droplets, which are accumulating in the aft-end cavity of the motor. To be able to carry out experimental investigation, at first the the VKI Level Detection and Recording(LeDaR) and Particle Image Velocimetry (PIV) measurement techniques had to be adapted to the two-phase flow condition of the facility. A parametric liquid accumulation assessment is performed experimentally using the LeDaR technique to identify the influence of various parameters on the liquid deposition rate. The obstacle tip to nozzle tip distance (OT2NT) is identified to be the most relevant, which indicates how much a droplet passing just at the inhibitor tip should deviate transversally to leave through the nozzle and not to be entrapped in the cavity. As LeDaR gives no indication of the driving mechanisms, the flow field is analysed experimentally, which is supported by numerical simulations to understand the main driving forces of the accumulation process. A single-phase PIV measurement campaign provides detailed information about the statistical and instantaneous flow structures. The flow quantities are successfully compared to an equivalent 3D unsteady LES numerical model. Two-phase flow CFD simulations suggest the importance of the droplet diameter on the accumulation rate. This observation is confirmed by two-phase flow PIV experiments as well. Accordingly, the droplet entrapment process is described by two mechanisms. The smaller droplets (representing a short characteristic time) appear to follow closely the air-phase. Thus, they may mix with the air-phase of the recirculation region downstream the inhibitor and can be carried into the cavity. On the other hand, the large droplets (representing a long characteristic time) are not able to follow the air-phase motion. Consequently, a large mean velocity difference is found between the droplets and the air-phase using the two-phase flow measurement data. Therefore, due to the inertia of the large droplets, they may fall into the cavity in function of the OT2NT and their velocity vector at the level of the inhibitor tip. Finally, a third mechanism, dripping is identified as a contributor to the accumulation process. In the current quasi axial 2D-like set-up large drops are dripping from the inhibitor. In this configuration they are the main source of the accumulation process. Therefore, additional numerical simulations are performed to estimate the importance of dripping in more realistic configurations. The preliminary results suggest that dripping is not the main mechanism in the real slag accumulation process. However, it may still lead to a considerable contribution to the final amount of slag.

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