This thesis aims to simulate previous wind tunnel experiments on the drag-reducing aerospike in order to help validate the accuracy of CFD analysis. Multiple grids were created with the Pointwise grid generation software. The CFD analysis software used was Ansys Fluent, with both planar and axisymmetric cases being tested for the primary rocket in order to compare the differences. The tests with the primary rocket followed how a spike of set length reacted at various speeds. Two additional experiments were duplicated. These helped confirm that the results obtained via Fluent were accurate. One case was a simple transonic spike model, and the other was a more complex hypersonic model. The results from both cases matched well with wind tunnel tests, validating results for the primary rocket. This thesis paves the way for anyone wanting to continue a more in depth study into the flow properties of any type of projectile.

This document describes the design of an axisymmetric aerospike nozzle to replace the conical converging-diverging nozzle of a commercially available hybrid rocket motor. The planar method of characteristics is used with isentropic flow assumptions to design the nozzle wall. Axisymmetric adjustments are made with quasi-one-dimensional flow approximations. Computational Fluid Dynamics (CFD) simulations verify these assumptions, and illustrate viscous effects within the flow. Nozzle truncations are also investigated. Development of a hybrid-rocket-specific data acquisition system is also detailed.

A study of thrust vectoring techniques of annular aerospike nozzles was conducted. Cold-flow blow-down testing along with solid modeling and rapid prototyping technology were used to investigate the effects of slot size, placement, geometry and orientation. The use of slot-type compound nozzles proved to be a feasible approach to thrust vectoring. Previous methods of thrust vectoring have proved to be difficult to implement in a cost effective manner or have had limited effectiveness or durability.

The Multiple Use Plug Hybrid for Nanosats (MUPHyN) prototype thruster incorporates solutions to several major challenges that have traditionally limited the deployment of chemical propulsion systems on small spacecraft. The MUPHyN thruster offers several features that are uniquely suited for small satellite applications. These features include 1) a non-explosive ignition system, 2) non-mechanical thrust vectoring using secondary fluid injection on an aerospike nozzle cooled with the oxidizer flow, 3) a non-toxic, chemically-stable combination of liquid and inert solid propellants, 4) a compact form factor enabled by the direct digital manufacture of the inert solid fuel grain. Hybrid rocket motors provide significant safety and reliability advantages over both solid composite and liquid propulsion systems; however, hybrid motors have found only limited use on operational vehicles due to 1) difficulty in modeling the fuel flow rate 2) poor volumetric efficiency and/or form factor 3) significantly lower fuel flow rates than solid rocket motors 4) difficulty in obtaining high combustion efficiencies. The features of the MUPHyN thruster are designed to offset and/or overcome these shortcomings. The MUPHyN motor design represents a convergence of technologies, including hybrid rocket regression rate modeling, aerospike secondary injection thrust vectoring, multiphase injector modeling, non-pyrotechnic ignition, and nitrous oxide regenerative cooling that address the traditional challenges that limit the use of hybrid rocket motors and aerospike nozzles. This synthesis of technologies is unique to the MUPHyN thruster design and no comparable work has been published in the open literature.

abstract: The aerospike nozzle belongs to the class of altitude compensating nozzles making it a strong candidate for Space Shuttle Main Engines. Owing to their higher efficiency compared to conventional bell nozzles, the aerospike nozzles are being studied extensively and are being used for many Single State to Orbit (SSTO) designs. A rocket engine nozzle with altitude compensation, such as the aerospike, consumes less fuel than a rocket engine with a bell nozzle. Aerospike nozzles are huge and are often difficult to construct and have to be truncated in order to make them feasible for application in a rocket propulsion system. Consequently, truncation of the aerospike leads to pressure loss under the base, which in-turn decreases the overall thrust produced by the rocket nozzle. To overcome this loss, a technique called base bleed is implemented in which a secondary jet is made to flow through the base of the truncated portion. This thesis uses dynamic pressure contour plots to find out the ideal base bleed mass flow rate to avoid base recirculation in 10 %, 20 % and 30 % truncated aerospike nozzles. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2017

In der vorliegenden Arbeit werden die Datenbankmanagementsysteme MongoDB, ScyllaDB, OrientDB, Aerospike und Redis mit dem Yahoo! Cloud Serving Benchmark unter der Verwendung von SSD-Speicher getestet. Dazu werden zuerst die verschiedenen NoSQL-Systemtypen beschrieben. Besonderheiten von SSD-Speicher werden zusammengefasst. Anschließend werden Besonderheiten der ausgewählten Datenbankmanagementsystemen und des Yahoo! Cloud Serving Benchmarks beschrieben, um die durchzuführenden Benchmarks zu planen. Weiterhin wird die verwendete Hardware beschrieben, um eine Replikation dieser Benchmarks zu ermöglichen und ein besseres Bild der zu messenden Performance zu bieten. Nach der Planung der Durchführung der Benchmarks, werden die verschiedenen Datenbankmanagementsysteme auf der oberen Grenze getestet, welche die gegebene Hardware bietet. Mit den Ergebnissen dieser werden weitere Benchmarks unter diversen Bedingungen geplant und durchgeführt. Die Ergebnisse werden jeweils ausgewertet und in dieser Arbeit eingebunden. Diese sind von den gegebenen Umständen stark beeinflusst, sodass allgemeingültige Aussagen nicht möglich sind. Zuletzt wird im Ausblick, welche inhaltliche Lücken und Fragen offen stehen oder weitere zusammenhängende Problemstellungen beschrieben.:1 Einleitung 1.1 Motivation 1.2 Vorgehensweise 2 Gegenstand des Benchmarks 2.1 Modell 2.1.1 Key-Value Store 2.1.2 Document Store 2.1.3 Wide-Column Store 2.1.4 Graph Store 2.1.5 Multi-Model 2.2 Medium 2.2.1 SSD 2.2.2 In-Memory 3 Technische Randbedingungen des Benchmarks 3.1 Ausgewählte Datenbankmanagementsysteme 3.2 Yahoo! Cloud Serving Benchmark 3.3 Genutzte Hardware 3.4 Testlauf des Benchmarks 3.5 Erzielter Vergleich 4 Erste Testreihe: 150GB 21 4.1 Aufgetretene Probleme 4.2 Verwendete Einstellungen 4.3 Ergebnisse: erster Versuch 4.4 Ergebnisse: 150GB 5 Testreihen: Übergreifende Szenarien 5.1 Testreihe 50GB 5.2 Testreihe 10GB 5.3 Testreihe Großes Feld 5.4 Testreihe Sekundärindex 5.5 Testreihe Latenz 5.6 Testreihe Discord 6 Ergebnisse DBMS-intern 6.1 MongoDB 6.2 ScyllaDB 6.3 OrientDB 6.4 Aerospike 6.5 Redis 7 Schlussteil 7.1 Auswertung 7.1.1 YCSB-Tool 7.1.2 MongoDB 7.1.3 ScyllaDB 7.1.4 Aerospike 7.1.5 OrientDB 7.1.6 Redis 7.1.7 SSD-Speicher 7.2 Zusammenfassung 7.3 Ausblick

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A labscale hybrid rocket motor test stand has been developed for research at Cal Poly. The primary focus of research using this rig has been the development of regenerative cooling techniques using nitrous oxide as coolant and oxidizer, as well as validation of technologies relating to the annular aerospike nozzle. In order to prevent undesirable deflection of the cantilevered spike, a structural stiffening web, referred to as “The Spider,” is proposed. The Spider resembles a three-spoked wheel, with the aerospike held by the inner hub and the chamber walls abutting the outer radius. The Spider, placed upstream of the nozzle, is subject to thermal loads due to radiation and convection from the gases, and conduction from the outer annulus, as well as mechanical loads from thermal expansion and gas flow. Simulation tools are developed in three phases to produce an accurate model of the spatio-temporal distribution of these loads. A prototype of the Spider instrumented with thermocouple probes is designed, manufactured, and subjected to a series of hotfire tests. Results from three experimental runs are gathered and compared to simulated results. Good agreement is shown for the most part between the two datasets, with a single noticeable discrepancy for one measured temperature location. The high fidelity in the mean rate of temperature change for all stations indicates that the convective heat load is accurately modeled. The simulation results, confirmed by experiment, indicate that in order for the Spider to survive in the steady-state during an actual burn, an active cooling strategy is necessary. Two actively cooled concept designs are presented and discussed, and future avenues of research are suggested.

Compound aerospike nozzles were designed and tested as part of an ongoing experimental study to determine the feasibility of thrust vectoring an aerospike nozzle with the addition of a secondary port. Earlier phases of the study have indicated that a compound aerospike nozzle could provide sufficient thrust vectoring. The addition of a hole-type secondary port was found to provide effective thrust vectoring. Experiments were carried out to determine the effects of secondary port size, secondary port inlet geometry and compound aerospike nozzle chamber pressure. Results show good predictability, axisymmetric flow, and emphasize the importance of a radius on secondary port inlet geometry.

The emerging and competitive environment in the space technology requires the improvements in the capability of aerodynamic vehicles. This leads to the analysis in drag reduction of the vehicle along with the minimized heat transfer rate. Using forward facing solid aerospike is the simplest way among the existing drag reduction methodologies for hypersonic blunt cone bodies. But the flow oscillations associated with this aerospike makes it difficult to implement. When analyzing this flow, it can be understood that this oscillating flow can be compared to conical cavity flow. Therefore in the spiked flows, it is decided to implement the technique used in reducing the flow oscillation of the cavities. Based on this method the shallow conical cavity flow generated by the aerospike fixed ahead of a 120o blunt cone body is fissured as multiple cavities by so many disks formed from 10o cone. Now the deep conical cavities had the length to mean depth ratio of unity; this suppresses the unnecessary oscillations of the shallow cavity. The total length of the telescopic aerospike is fixed as 100mm. And one another conical tip plain aerospike of same length is designed for comparing the telescopic spike’s performance at hypersonic flow Mach numbers of 5.75 and 7.9. A three component force balance system capable of measuring drag, lift and pitching moment is designed and mounted internally into the skirt of the model. Drag measurement is done for without spike, conical tip plain spiked and telescopic spiked blunt cone body. The three configurations are tested at different angles of attack from 0 to 10 degree with a step of 2. A discrete iterative deconvolution methodology is implemented in this research work for obtaining the clean drag history from the noisy drag accelerometer signal. The drag results showed the drag reduction when compared to the without spike blunt cone body. When comparing to the plain spiked, the telescopic spiked blunt cone body has lesser drag at higher angles of attack. Heat transfer measurements are done over the blunt cone surface using the Platinum thin film gauges formed over the Macor substrate. These results and the flow visualization give better understanding of the flow and the heat flux rate caused by the flow. The enhancement in the heat flux rate over the blunt cone surface is due to the shock interaction. And in recirculation region the heat flux rate is very much lesser when compared to without spike blunt cone body. It is observed that the shock interaction in the windward side is coming closer towards the nose of the blunt cone as the angle of attack increases and the oscillation of the oblique shock also decreases. Schlieren visualization showed that there is dispersion in the oblique shock, particularly in the leeward side. In the telescopic spike there are multiple shocks generated from each and every disk which coalesces together to form a single oblique shock. And the effect of the shock generated by the telescopic spike is stronger than the effect of the shock generated by the conical tip plain spike.