Browsing by Author "Pitot de la Beaujardiere, Jean-Francois Philippe."

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Analysis of potential small satellite launch operations at the Denel Overberg test range.
(2022) Arunakirinathar, Aravind.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
One of the primary objectives of the South African First Integrated Rocket Engine (SAFFIRE) programme of UKZN’s Aerospace System Research Group (ASReG) is to develop the capacity for orbital injection missions to Low Earth Orbits (LEOs) from South Africa. The most likely launch site for these missions is the Denel Overberg Test Range (OTR) near Cape Agulhas in the Western Cape. In order to determine the suitability of OTR as a launch site, it is imperative to gain an understanding of the performance, mechanics and structural loads of a vehicle entering orbit. The goal of this dissertation is to analyse the performance of a variety of modern two-stage launch vehicles as they travel along orbital injection trajectories into LEOs from OTR. This study considers solutions for the ascent-to-orbit trajectory for various launch vehicles. The primary method was to utilise trajectory optimisation methods and this was achieved by developing an optimal control solver, which makes use of direct Hermite-Simpson collocation methods, and a sequential quadratic programming solver. In order to improve the robustness and speed of the solver, formulae for the first order analytical derivative information of direct Hermite-Simpson collocation were developed. The optimal control solver was then validated using various linear and nonlinear examples from literature. The optimal control solver was used to analyse the performance of various hypothetical missions conducted by the following established launch vehicles: Rocket Lab’s Electron, SpaceX’s Falcon 1, SpaceX’s Falcon 9, and ASReG’s proposed small satellite launch vehicle, CLV. As a baseline comparison, all vehicles were launched from OTR into various LEOs. The payloads, trajectories, control histories and structural loads of these vehicles for injection were investigated. Finally, the effect of perigee altitude, inclination, and eccentricity of orbits on the extracted results was studied. The payload performance of the launch vehicles considered were relatively similar to that provided by each vehicle’s corresponding payload user guide. On all missions, the altitude of the Electron, Falcon 9 and CLV would constantly increase with range, however the Falcon 1 would tend to rise, dip, and then rise once more on missions to orbits with a perigee altitude of 200 km. Such trajectories are referred to as lofted trajectories and are common among vehicles with a low upper stage thrust to weight ratio (Patton and Hopkins, 2006), such as the Falcon 1. The tangent yaw and pitch of the thrust direction was highly linear for all analysed missions. This result allows for a reasonable control law which can be used to determine trajectory solutions using indirect optimal control methods. This study demonstrates the viability of the Denel Overberg Test Range as a competitive base of operation for space launch missions to LEO.
Closed-loop throttle control of a hybrid rocket motor.
(2018) Velthuysen, Timothy Johnathan.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
Hybrid rocket motors produce thrust by reacting a solid fuel with a liquid oxidizer inside a combustion chamber. This approach has certain advantages over conventional solid propellant rockets including improved safety and the potential for thrust control, while also being less expensive than liquid propellant engines. Liquefying hybrid fuels, such as paraffin wax, regress at a faster rate than the conventional solid fuels like HTPB that are dominated by vaporization at the solid-gas interface. Non-classical theory is still in its infancy, however, and more work is required to validate performance models experimentally, especially where throttling of the oxidizer mass flowrate is incorporated. While hybrid motor throttlabilty remains a subject of considerable interest, there has been little investigation of throttling in motors that use high regression rate, liquefying fuels such as paraffin wax. This study proposes a closed-loop thrust control scheme for paraffin wax/nitrous oxide hybrid rocket motors using a low-cost ball valve as the controlling hardware element. There are a number of advantages to throttling hybrid rocket motors but the most important is to enforce a constant thrust curve throughout the burn. A test facility and laboratory scale hybrid rocket motor utilizing paraffin wax as fuel and nitrous oxide as oxidiser were used for experimental testing. Using a mathematical model of a laboratory-scale hybrid rocket motor, the controller constants for a PID controller were obtained and tested through experimental testing. Open-loop testing was first done in order to determine the control authority of the ball valve over the oxidiser mass flowrate, as well as characterize the oxidiser mass flowrate in relation to each valve angle value. Closed-loop testing was undertaken to verify and refine the controller constants obtained via the laboratory-scale model. The tests prompted a redesign of the injector and additions to the LabVIEW™ controller regime. Using results from the open-loop tests a feed-forward lookup table was developed to allow for the controller to move to a specified angle quickly and thereby remove nonlinearities present in flow control using ball valves. Three successful closed-loop tests were done where the controller causes the thrust of the motor to track a predetermined thrust or chamber pressure set point with a reasonable degree of accuracy. The set-point profile of the first test was a constant thrust throughout the burn while the second test had a ramp set-point profile. The final test used chamber pressure as the feedback variable and had a step-down set-point profile. This study demonstrates that thrust control can be exercised over a paraffin wax/nitrous oxide hybrid rocket motor, using a low-cost ball valve as the control element to modulate the oxidiser mass flowrate.
Design and performance simulation of a hybrid sounding rocket.
(2012) Chowdhury, Seffat Mohammad.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Roberts, Lancian Willett.
Sounding rockets find applications in multiple fields of scientific research including meteorology, astronomy and microgravity. Indigenous sounding rocket technologies are absent on the African continent despite a potential market in the local aerospace industries. The UKZN Phoenix Sounding Rocket Programme was initiated to fill this void by developing inexpensive medium altitude sounding rocket modeling, design and manufacturing capacities. This dissertation describes the development of the Hybrid Rocket Performance Simulator (HYROPS) software tool and its application towards the structural design of the reusable, 10 km apogee capable Phoenix-1A hybrid sounding rocket, as part of the UKZN Phoenix programme. HYROPS is an integrated 6–Degree of Freedom (6-DOF) flight performance predictor for atmospheric and near-Earth spaceflight, geared towards single-staged and multi-staged hybrid sounding rockets. HYROPS is based on a generic kinematics and Newtonian dynamics core. Integrated with these are numerical methods for solving differential equations, Monte Carlo uncertainty modeling, genetic-algorithm driven design optimization, analytical vehicle structural modeling, a spherical, rotating geodetic model and a standard atmospheric model, forming a software framework for sounding rocket optimization and flight performance prediction. This framework was implemented within a graphical user interface, aiming for rapid input of model parameters, intuitive results visualization and efficient data handling. The HYROPS software was validated using flight data from various existing sounding rocket configurations and found satisfactory over a range of input conditions. An iterative process was employed in the aerostructural design of the 1 kg payload capable Phoenix-1A vehicle and CFD and FEA numerical techniques were used to verify its aerodynamic and thermo-structural performance. The design and integration of the Phoenix-1A‟s hybrid power-plant and onboard electromechanical systems for recovery parachute deployment and motor oxidizer flow control are also discussed. It was noted that use of HYROPS in the design loop led to improved materials selection and vehicle structural design processes. It was also found that a combination of suitable mathematical techniques, design know-how, human-interaction and numerical computational power are effective in overcoming the many coupled technical challenges present in the engineering of hybrid sounding rockets.
Development of a composite oxidiser tank for the Phoenix-1B Mk. II hybrid rocket.
(2020) Williams, Dylan Roy.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
Abstract available in PDF.
Development of a comprehensive energy model to simulate the energy efficiency of a battery electric vehicle to allow for prototype design optimisation and validation.
(2017) Woods, Matthew Allan Ray.; Bemont, Clinton Pierre.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
This dissertation describes the development of an energy model of a battery electric vehicle (BEV) to assist designers in evaluating the impact of overall energy efficiency on vehicle performance. Energy efficiency is a crucial metric for BEVs as it defines the driving range of the vehicle and optimises the limited amount of energy available from the on-board battery pack, typically the most expensive component of the vehicle. Energy modelling also provides other useful information to the designer, such as the range of the vehicle according to legislative drive cycles and the maximum torque required from the motor. An accurate, fast and efficient model is therefore required to simulate BEVs in the early stages of design and for prototype validation. An extensive investigation into BEV modelling and the mechanisms of energy losses within BEVs was conducted. Existing literature was studied to characterise the effect of operating conditions on the efficiency of each mechanism, as well as investigating existing modelling techniques used to simulate each energy loss. A complete vehicle model was built by considering multiple domain modelling methods and the flow of energy between components in both mechanical and electrical domains. Simscape™, a MathWorks MATLAB™ tool, was used to build a physics based, forward facing model comprising a combination of custom coded blocks representing the flow of energy from the battery pack to the wheels. The acceleration and speed response of the vehicle was determined over a selected drive cycle, based on vehicle parameters. The model is applicable to normal driving conditions where the power of the motor does not exceed its continuous rating. The model relies on datasheet or non-proprietary parameters. These parameters can be changed depending on the architecture of the BEV and the exact components used, providing model flexibility. The primary model input is a drive cycle and the primary model output is range as well as the dynamic response of other metrics such as battery voltage and motor torque. The energy loss mechanisms are then assessed qualitatively and quantitatively to allow vehicle designers to determine effective strategies to increase the overall energy efficiency of the vehicle. The Mamba BEV, a small, high-power, commercially viable electric vehicle with a 21 kWh lithium-ion battery was simulated using the developed model. As the author was involved in the design and development of the vehicle, required vehicle parameters were easily obtained from manufacturers. The range of the vehicle was determined using the World-Harmonised Light Duty Vehicles Test Procedure and provided an estimated range of 285.3 km for the standard cycle and 420.8 km for the city cycle.
Development of a high concentration solar flux mapping system.
(2018) Van Bakel, Brandon Luke.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
The Group for Solar Energy Thermodynamics (GSET) is in the process of commissioning the Solar Energy Research Amplified Flux Facility (SERAFF), which is South Africa’s first solar furnace facility. SERAFF is situated at the University of KwaZulu-Natal’s Howard College campus and assumes an on-axis optical configuration, comprising a 9 m2 non-focusing heliostat reflector, a 3 m diameter paraboloidal dish concentrator and a test article platform. The facility was designed to aid research in the fields of high temperature materials testing, concentrating solar energy and solar thermochemistry. The concentrated radiative energy output of a solar furnace establishes the energy input to prototype receivers, reactors or materials that aim to be tested using the facility. The challenge is compounded by the temporal and spatial variation of SERAFF’s radiative energy output, influenced by weather-related and geometric factors. In this study, an indirect spatial flux mapping system is developed to characterise SERAFF’s spatial radiative energy output. SERAFF’s theoretical spatial radiative energy output is estimated through Monte Carlo ray-tracing techniques to provide benchmark performance parameters including total thermal power output, peak concentration ratio and focal spot size. The indirect system uses optical measurement techniques, in which spatial solar flux is measured via diffuse reflection off a Lambertian target using a digital CMOS camera through a neutral density filter and lens. Pixel intensities are calibrated against reference measurements acquired from a circular-foil Gardon gauge heat flux transducer. The calibrated CMOS camera can be used to measure values of radiative flux, incident at the focal plane from 0 kW/m2 - 468.19 kW/m2. Measurements were restricted to a brief testing period and are not representative of SERAFF’s peak operating conditions. Spatial flux measurements indicated a thermal power output of 3.83 kW, with a corresponding peak solar flux of 227.8 kW/m2 within a focal diameter of 250 mm. The study demonstrated successful integration of an indirect spatial flux mapping system into the SERAFF solar furnace.
Development of a hybrid sounding rocket motor.
(2013) Bernard, Geneviève.; Brooks, Michael John.; Roberts, Lancian Willett.; Pitot de la Beaujardiere, Jean-Francois Philippe.
This work describes the development of a hybrid rocket propulsion system for a reusable sounding rocket, as part of the first phase of the UKZN Phoenix Hybrid Sounding Rocket Programme. The programme objective is to produce a series of low-to-medium altitude sounding rockets to cater for the needs of the African scientific community and local universities, starting with the 10 km apogee Phoenix-1A vehicle. In particular, this dissertation details the development of the Hybrid Rocket Performance Code (HRPC) together with the design, manufacture and testing of Phoenix-1A’s propulsion system. The Phoenix-1A hybrid propulsion system, generally referred to as the hybrid rocket motor (HRM), utilises SASOL 0907 paraffin wax and nitrous oxide as the solid fuel and liquid oxidiser, respectively. The HRPC software tool is based upon a one-dimensional, unsteady flow mathematical model, and is capable of analysing the combustion of a number of propellant combinations to predict overall hybrid rocket motor performance. The code is based on a two-phase (liquid oxidiser and solid fuel) numerical solution and was programmed in MATLAB. HRPC links with the NASA-CEA equilibrium chemistry programme to determine the thermodynamic properties of the combustion products necessary for solving the governing ordinary differential equations, which are derived from first principle gas dynamics. The combustion modelling is coupled to a nitrous oxide tank pressurization and blowdown model obtained from literature to provide a realistic decay in motor performance with burn time. HRPC has been validated against experimental data obtained during hot-fire testing of a laboratory-scale hybrid rocket motor, in addition to predictions made by reported performance modelling data. Development of the Phoenix-1A propulsion system consisted of the manufacture of the solid fuel grain and incorporated finite element and computational fluid dynamics analyses of various components of the system. A novel casting method for the fabrication of the system’s cylindrical single-port paraffin fuel grain is described. Detailed finite element analyses were performed on the combustion chamber casing, injector bulkhead and nozzle retainer to verify structural integrity under worst case loading conditions. In addition, thermal and pressure loading distributions on the motor’s nozzle and its subsequent response were estimated by conducting fluid-structure interaction analyses. A targeted total impulse of 75 kNs for the Phoenix-1A motor was obtained through iterative implementation of the HRPC application. This yielded an optimised propulsion system configuration and motor thrust curve.
Development of a solar furnace heliostat.
(2016) Perumall, Preyen Agasthian.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
The Solar Energy Research Amplified Flux Facility (SERAFF) is the flagship project of University of KwaZulu-Natal’s Group for Solar Energy Thermodynamics (GSET). SERAFF will assume an on-axis optical configuration, common in solar furnaces around the world, comprising a flat, non-imaging heliostat reflector and a paraboloidal primary concentrator. At design-point conditions, a thermal power output of approximately 5 kW is expected with a peak flux in the region of 3 MW/m2. The facility will provide the University of KwaZulu-Natal with a platform to undertake wide-ranging research in disciplines including concentrating solar power, materials testing and processing, and solar thermochemistry, amongst others. The primary goal of this research was to design and fabricate a flat heliostat which will enable SERAFF to meet the specified thermal requirements. The first phase of this study was to characterise the available solar resource for Durban, South Africa, where SERAFF will be installed. A statistical algorithm was developed that processes historical ground-based solar measurements to generate a continuous function that estimates clear-sky direct normal irradiance (DNI) as a function of solar time and day number over a typical year. The three-dimensional surface that results from this function is termed a temporal DNI topograph (TDT) and can be used to define solar flux input for the modelling of concentrator systems. The heliostat dimensions are dependent on the size of the concentrator aperture it is tasked with illuminating. As such, sizing the concentrator was key. A geometrically based approximation of the maximum theoretical power output of a parabolic primary concentrator was developed. This model was used to calculate the diameter of the parabolic concentrator needed to achieve SERAFF’s specified power output. The model was validated against real solar furnaces around the world and it was found that the model approximated the power output for these solar furnaces within 12% of their published power output values. Following an optical analysis and illumination study, and after taking into consideration the practical and financial constraints placed on the project, it was decided that 3 m x 3 m was the most suitable size for SERAFF’s heliostat. A finite element analysis was used in the design process to assess the survivability (under load from a worst-case wind speed of 100 km/hr) and the rigidity (under load from an operational wind speed of 20 km/hr) for the different heliostat design concepts considered. After analyses of the FEA results it was decided that a classical T-shape design with an aluminium mirror backing frame would be employed. Fabrication of the structural components was undertaken at the department of Mechanical Engineering’s workshop and assembled at a temporary site in close proximity. Consideration was given to the effect the fabrication process would have on the tracking and optical accuracy of the heliostat. The total cost of fabrication was R91,655, exceeding the budget of R85,000 by R6,655. This was due to high import taxes paid on the slewing drive actuator and polished aluminium mirror facets. The actual cost of materials and components was R70,353 excluding the import taxes.
Development of liquid propellant tanks for a suborbital launch vehicle.
(2022) Mchunu, Vulinhlanhla Salvation.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.
Having developed several hybrid sounding rockets, the Aerospace Systems Research Group (ASReG) at the University of KwaZulu-Natal is currently investigating the development of an indigenous launch vehicle for micro satellites. As part of this effort, a liquid propellant rocket engine called the South African First Integrated Rocket Engine (SAFFIRE) is in the advanced design phase. SAFFIRE combusts liquid oxygen and kerosene propellants to generate thrust. Following ground tests, the first version of the SAFFIRE engine will be incorporated into a single-stage launch vehicle to test its flight performance during the suborbital flight. This study aimed to develop a design procedure and subsequent engineering designs for propellant tanks suitable for use by this launch vehicle, known as the Suborbital Test Vehicle (STEVE). The liquid oxygen and kerosene propellant tanks were designed according to NASA propellant tank design guidelines based on the mechanical properties of half-hard 301L stainless steel – the alloy selected as the material of construction for both tanks. This material has various advantageous characteristics, including its compatibility with liquid oxygen, its high strength once work-hardened and its increased strength and ductility at cryogenic temperatures. As part of the study, comprehensive material testing was conducted to establish a suitable tank welding procedure and to evaluate the achievable weld efficiency. For the best performing welding procedure assessed, mean weld efficiencies with respect to yield strength and tensile strength were determined to be 70 % and 81 %, respectively. A trial propellant tank was fabricated using the selected welding procedure and subsequently subjected to a destructive hydrostatic pressure test. The outcomes of this test provided a clear indication of the modes and progression of tank failure and served to inform final design work. In terms of propellant tank layout, a tandem configuration with the liquid oxygen tank positioned above the kerosene tank was selected, in order to improve the stability characteristics of the vehicle and to minimise total feedline length. To reduce vehicle drag and mitigate aerodynamic heating effects, the liquid oxygen feedline was configured to pass coaxially through the kerosene tank via a tunnel tube. The incorporation of elliptical tank ends in both tank designs was dictated by pre-existing tooling made available by the tank end manufacturer. Based on these design characteristics, the anticipated tank loading conditions and the mechanical properties of the as-welded 301L stainless steel alloy, a minimum wall thickness requirement of 2 mm was determined for both tanks via finite element analysis.
Independent assessment and benchmarking of no/low cost finite element analysis software for linear and non/linear static structural analysis.
(2016) Rugdeo, Saien Bemont.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Bemont, Clinton Pierre.
The aim of this research was to determine if the development of low-cost (less than 500 USD) or no-cost analysis software, specifically in the area of computational structural mechanics through finite element analysis (FEA), has advanced to the point where it can be used in place of trusted commercial FEA software packages for linear and non-linear static structural analyses using isotropic materials. This was done by conducting an initial market research study and identifying a range of available no-cost/low-cost FEA packages. Eighteen suitable packages were identified and a preliminary analysis was done to identify analysis capabilities, presence of internal modules, extent of available user documentation, and end user support. The packages underwent a process of systematic elimination from the preceding phases of the research if they were unable to meet the minimum imposed criteria. Six packages were deemed suitable and were further investigated. From these, three packages were chosen to be subjected to performance benchmarking, namely: Code_Aster/Salome Meca; Mecway and Z88 Aurora. SimScale, a browser-based analysis package was included as well because it met all the baseline criteria and has the potential to offer a completely cloud-based approach to computer aided engineering, potentially reshaping the way an engineering business views its operational capabilities. Performance benchmarking assessed the ability of a package to generate a model and obtain accurate solutions relative to industry accepted benchmark publications, trusted analytical solutions found in reputable engineering text, as well as experimental results obtained in this work. The benchmarking process was also done on commercial FEA packages so that a comparison can be made between the no-cost/low-cost packages and those considered to be the premium FEA software packages available. It was found that the no-cost/low-cost options were able to perform adequately for most of the test cases. SimScale and Z88 Aurora had difficulties with generating suitable meshes which meant that compromises in model generation approaches needed to be made. Overall, the results yielded by the low-cost/no-cost options showed good correlation with test case target values as well as exhibiting many capabilities and tools found in the high-cost, trusted commercial packages investigated. It is therefore concluded that there are no-cost/low-cost FEA packages that can be used in place of high-cost commercial packages for linear and non-linear static structural analyses of isotropic materials.
Numerical simulation of the structural response of a composite rocket nozzle during the ignition transient.
(2009) Pitot de la Beaujardiere, Jean-Francois Philippe.; Bright, Glen.; Morozov, Evgeny.
The following dissertation describes an investigation of the structural response behaviour of a composite solid rocket motor nozzle subjected to thermal and pressure loading during the motor ignition period, derived on the basis of a multidisciplinary numerical simulation approach. To provide quantitative and qualitative context to the results obtained, comparisons were made to the predicted aerothermostructural response of the nozzle over the entire motor burn period. The study considered two nozzle designs – an exploratory nozzle design used to establish the basic simulation methodology, and a prototype nozzle design that was employed as the primary subject for numerical experimentation work. Both designs were developed according to fundamental solid rocket motor nozzle design principles as non-vectoring nozzles for deployment in medium sized solid rocket booster motors. The designs feature extensive use of spatially reinforced carbon-carbon composites for thermostructural components, complemented by carbon-phenolic composites for thermal insulation and steel for the motor attachment substructures. All numerical simulations were conducted using the ADINA multiphysics finite element analysis code with respect to axisymmetric computational domains. Thermal and structural models were developed to simulate the structural response of the exploratory nozzle design in reference to the instantaneous application of pressure and thermal loading conditions derived from literature. Ignition and burn period response results were obtained for both quasi-static and dynamic analysis regimes. For the case of the prototype nozzle design, a flow model was specifically developed to simulate the flow of the exhaust gas stream within the nozzle, for the provision of transient and steady loading data to the associated thermal and structural models. This arrangement allowed for a more realistic representation of the interaction between the fluid, thermal and structural fields concerned. Results were once again obtained for short and long term scenarios with respect to quasi-static and dynamic interpretations. In addition, the aeroelastic interaction occurring between the nozzle and flow field during motor ignition was examined in detail. The results obtained in the present study provided significant indications with respect to a variety of response characteristics associated with the motor ignition period, including the magnitude and distribution of the displacement and stress responses, the importance of inertial effects in response computations, the stress response contributions made by thermal and pressure loading, the effect of loading condition quality, and the bearing of the rate of ignition on the calculated stress response. Through comparisons between the response behaviour predicted during the motor ignition and burn periods, the significance of considering the ignition period as a qualification and optimisation criterion in the design of characteristically similar solid rocket motor nozzles was established.
Performance modelling and simulation of a 100km hybrid sounding rocket.
(2013) Leverone, Fiona Kay.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Roberts, Lancian Willett.
The University of KwaZulu-Natal (UKZN) Phoenix Hybrid Sounding Rocket Programme was established in 2010. The programme’s main objective is to develop a sounding rocket launch capability for the African scientific community, which currently lacks the ability to fly research payloads to the upper atmosphere. In this dissertation, UKZN’s in-house Hybrid Rocket Performance Simulator (HYROPS) software is used to improve the design of the Phoenix-2A vehicle, which is intended to deliver a 5 kg instrumentation payload to an apogee altitude of 100 km. As a benchmarking exercise, HYROPS was first validated by modelling the performance of existing sub-orbital sounding rockets similar in apogee to Phoenix-2A. The software was found to approximate the performance of the published flight data within 10%. A generic methodology was then proposed for applying HYROPS to the design of hybrid propellant sounding rockets. An initial vehicle configuration was developed and formed the base design on which parametric trade studies were conducted. The performance sensitivity for varying propulsion and aerodynamic parameters was investigated. The selection of parameters was based on improving performance, minimising cost, safety and ease of manufacturability. The purpose of these simulations was to form a foundation for the development of the Phoenix-2A vehicle as well as other large-scale hybrid rockets. Design chamber pressure, oxidiser-to-fuel ratio, nozzle design altitude, and fin geometry were some of the parameters investigated. The change in the rocket’s propellant mass fraction was the parameter which was found to have the largest effect on performance. The fin and oxidiser tank geometries were designed to avoid fin flutter and buckling respectively. The oxidiser mass flux was kept below 650 kg/m2s and the pressure drop across the injector relative to the chamber pressure was maintained above 15% to mitigate the presence of combustion instability. The trade studies resulted in an improved design of the Phoenix-2A rocket. The propellant mass of the final vehicle was 30 kg less than the initial conceptual design and the overall mass was reduced by 25 kg. The Phoenix-2A vehicle was 12 m in length with a total mass of 1006 kg. The fuel grain length of Phoenix-2A was 1.27 m which is approximately 3 times that of Phoenix-1A. The benefit of aluminised paraffin wax as a fuel was also investigated. The results indicated that more inert mass can be delivered to the target apogee of 100 km when using a 40% aluminised paraffin wax.
Preliminary design considerations for a commercial launch vehicle upper stage.
(2021) Gyasi-Agyei, Phillip Kwabena Konadu.; Brooks, Michael John.; Pitot de la Beaujardiere, Jean-Francois Philippe.
The African small satellite industry (micro and nano satellites in particular) continues to grow with developments in the miniaturization of satellite technology. However, the costs and delays involved with the traditional “piggy backing” satellite launch method is unsustainable for small sat developers and has thus created a niche market for dedicated small satellite launch services. Notably, there is no satellite launch capability whatsoever in Africa, meaning all of the continent’s launch requirements are serviced by foreign providers, incurring additional cost. As its primary objective, the University of KwaZulu-Natal’s (UKZN’s) Aerospace Systems Research Group (ASReG) seeks to enable the establishment of an indigenous small satellite launch capability in alignment with the South African Government’s goals. To this end, ASReG is currently developing the LOX/Kerosene SAFFIRE (South African First Integrated Rocket Engine) to propel a hypothetical two-stage orbital launch vehicle, termed Commercial Launch Vehicle 1 (CLV). The upper stage of the launch vehicle will use a vacuum-expanded variant of SAFFIRE called SAFFIRE-V. The upper stage for both cases must meet the design constraints of a 0.85 mass fraction and a 1.2 m outer diameter. CLV has been envisaged to deliver a 75kg payload to 400 km sun synchronous orbit. This thesis presents a high level analysis focusing on the upper stage of CLV, which intends to guide design decisions by comparing design options based on mass, and develop a methodology for upper stage vehicle design. One of the major design decisions is the type of propellant feed system the vehicle should use; in this regard, the analysis compares an electric pump feed system to a pressure fed system. Another is the selection of propellant tank material, given that the propellant tanks constitute most of the mass of a rocket. Stainless steel (301 and Duplex), aluminium alloy (7075), aluminium-lithium (2195), carbon fibre reinforced plastic (T700/Epoxy), as well as combinations of materials were compared. To perform the preliminary mass analysis, each of the major components/systems of the CLV upper stage were independently designed and the various design options available for each of the components/systems were compared based on mass. These systems and components include: fuel and oxidiser propellant tanks, the propellant pressurization system and the reaction control system. After the individual analyses of the variations of each component, the best suited architectures were modelled in SolidWorks CAD software. The components were then assembled, in CAD. The analysis found that, on a preliminary basis, the Lithium ion (Li-Ion) based electric pump fed upper stages did not meet the mass requirements while Lithium polymer (Li-Po) based upper stages achieved the mass requirements. An upper stage employing stainless steel propellant tanks was found to meet the mass requirements, but only for a pressure fed upper stage. Overall, pressure fed upper stages had lower masses compared to electric pump vehicles. The mass reduction of thin walled, low pressurized, propellant tanks (resulting from using electric pumps) was offset by the mass of the battery packs required to power the pumps.
Structural analysis of a composite monocoque chassis for use in a high performance electric vehicle.
(2018) Witteveen, Nicholas Tjebbe.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Brooks, Michael John.; Bemont, Clinton Pierre.
The adoption of electric vehicle technology is becoming more prevalent, as society strives to reduce the negative impact of greenhouse gas emissions and focuses on a sustainable future. This thesis details the design and structural analysis of a carbon composite monocoque chassis for application in a light-weight, high-performance electric vehicle for a South African market, based on the fundamental principles of automotive vehicle design. Handling characteristics and the design impacts they have on the decisions made in developing a vehicle chassis were explored. The two-dimensional geometry of the chassis structure was developed in the Siemens NX design environment, taking into account the spatial requirements of the mechanical and electrical system components, as well as occupant ergonomics. A zonedbased approach was taken in defining the composite layup for the chassis panels, using material data for locally obtained fabrics and epoxy resin. The chassis’ composite lay-up configuration was developed using several static load cases, simulating operational loading, as well as extreme loading arising in certain accident scenarios. The composite structure was analysed, with the first ply composite failure criterion being used to predict failure in the constituent materials. Design refinement was undertaken until the failure criterion predicted structural survivability for all the extreme loading cases considered.
Structural characterisation and response modelling of paraffin-based hybrid rocket motor fuel grains.
(2020) Veale, Kirsty Lynn.; Adali, Sarp.; Pitot de la Beaujardiere, Jean-Francois Philippe.; Bemont, Clinton Pierre.
Abstract available in PDF.