Michael J. Brooks

An Integrated Six Degree-of-Freedom Trajectory Simulator for Hybrid Sounding Rockets

In this paper a set of mathematical models of a generic hybrid rocket mission is developed for flight performance prediction purposes. This includes a hybrid rocket physical model, recovery system model, accurate atmospheric and gravitational models, a CFD based aerodynamics database and a hybrid motor combustion model. The integration of these mathematical models within a 6-DOF numerical trajectory simulation code based on Newtonian rigid-body dynamics results in a useful hybrid rocket design and evaluation tool, the Six Degree-of-freedom Performance Simulator (SDPS). This software tool is used to swiftly predict relevant flight performance parameters and perform Monte Carlo dispersion analyses on key design parameters. Variations to rocket geometric and physical parameters are then performed to improve performance. As a test case, flight performance uncertainties due to aerodynamics and wind variations on a small hybrid rocket were predicted and analysed. Results suggest that it is possible to measure and quantify uncertainties in general flight performance.

Performance Modeling of a Paraffin Wax / Nitrous Oxide Hybrid Rocket Motor

This paper describes the development of a one-dimensional, non-steady flow predictive performance model for hybrid rocket motors. The analysis relies on basic thermodynamic and gas dynamic assumptions. The analytical model was programmed in MATLAB and uses the NASA-CEA equilibrium chemistry code to determine gas combustion properties. An empirical regression rate correlation is employed in the model with ballistic coefficients found in the literature. The predictive model implements conservation of mass and the ideal gas equation of state to compute changes in chamber pressure. Instantaneous performance parameters such as theoretical thrust and specific impulse can be analyzed for different operating conditions defined by the user. To validate the analytical model, a laboratory-scale motor has been designed and manufactured using a paraffin wax and nitrous oxide propellant combination. Hot-fire test data are compared with the predictive modeling.

Introduction to the University of KwaZulu-Natal Hybrid Sounding Rocket Program

A hybrid rocket research program has been initiated in the School of Mechanical Engineering at the University of KwaZulu-Natal (UKZN), South Africa. This paper gives an overview of the program, including a description of the aims, design of test equipment, modeling tools and proposed flight vehicle. The program is defined by a series of goals, including the launch of a 10 km apogee vehicle powered by paraffin wax and nitrous oxide by the end of 2011, and a subsequent 100 km attempt within three years.

The Phoenix Hybrid Sounding Rocket Program: A Progress Report

The University of KwaZulu-Natal’s Phoenix Program aims to develop a hybrid sounding rocket capable of reaching 100 km apogee by 2016. The first stage of the program is the development of the Phoenix-1A low altitude vehicle, capable of delivering a 1 kg payload to an altitude of 10 km. The vehicle’s aerodynamic and structural designs have been optimized for transonic flight and the manufacture of structural components has commenced. This paper outlines the geometric design, computational analyses and manufacturing techniques associated with critical structural components of the vehicle. These include the composite airframe and fins, internal bulkheads, oxidizer tank, injector bulkhead, combustion chamber casing, and motor nozzle assembly. The integration of the payload and recovery system is also discussed. The effects of various design solutions on the simulated vehicle performance have been investigated using the custom-developed Hybrid Rocket Performance Simulation or HYROPS software. The immediate objectives of the program are to begin static testing of the Phoenix-1A flight motor by October 2011 and to start flight testing of the vehicle in early 2012.

Establishment of a broadband radiometric ground station on the South African east coast

A radiometric monitoring program for solar irradiance has been initiated on the Howard College campus of the University of KwaZulu-Natal (UKZN) in Durban, South Africa. This paper describes the establishment of the broadband ground station which employs conventional radiometers and a new type of pyranometer shadow band. The ZEBRA (Zonal Exposure to Broadband RAdiation) band consists of a perforated metal strip that permits the separation of direct normal and diffuse irradiance from global data with a single pyranometer. In this paper a time-based model of the new bands shading mask is described. The model is derived from a ray tracing exercise that accounts for ZEBRA geometry and solar position throughout a generic 365-day year. The UKZN facility lies at 29.9° South latitude and is part of a larger test initiative for the new shadow band that includes the NREL Solar Radiation Research Laboratory in Colorado. Data from northern and southern hemisphere test sites are to be used to characterize performance of the band under a range of conditions and for comparison with output from the newly developed model.

Pulse -Driven Refrigeration: Progress and Challenges

A v arian t of the pulse thermal loop is proposed for use in terrestrial and space thermal management systems. The two -phase device is driven by a pair of constant volume boilers feeding an ejector which entrains secondary flow from an evaporator. A high -temperature load from battery -packs or onboard electronics can be used to pressurize the boilers while the evaporator draws heat from a cooling load in the vapor compression loop . Two configurations of the hybrid prototype are described , both running on R 134a . A uniq ue feature of the system is unsteady flow through the ejector, which leads to challenges in entraining working fluid from the vapor compression branch. Preliminary test data suggest that secondary flow entrainment is possible under pulsatile flow condition s, although pressure drop through the ejector negatively affects operation of the outer driving loop. An alternate configuration is proposed to overcome operational challenges, and preliminary results from a numerical simulation of unsteady flow through th e ejector are presented .

Parametric Control of a Two-Phase Thermal Management System for Space Applications

As spacecraft increase in complexity, greater power is required to drive their onboard systems. The resulting generation of waste heat demands efficient thermal control, especially for electrical components emitting heat at high flux densities. Weislogel proposed a passive two-phase heat transport system for space application, driven by constant volume boilers, called the pulse thermal loop (PTL). This paper describes four methods of operating a PTL using real-time pressure data as the control parameter. Preliminary results are presented from an experimental loop using R-134a as the working fluid. Control is exercised through algorithm-based schemes implemented in LabVIEW. Results suggest that stable operation of the loop is best achieved by actuating flow control valves in response to a preset pressure difference between the boilers. Control schemes based on absolute pressure, set pulse frequency, and a combination of absolute and differential pressures are also described. Performance data are presented, and some of the challenges faced during PTL operation are discussed, including start-up and asymmetrical pressurization of the boilers.Copyright

Flight Test of the Phoenix-1A Hybrid Rocket

The Phoenix-1A hybrid rocket is a low-altitude demonstrator developed by the Aerospace Systems Research Group (ASReG) at the University of KwaZulu-Natal (UKZN). In August 2013 the hybrid motor was successfully fired in a static ground test to determine its performance. Thereafter, the vehicle airframe and onboard systems were completed and the rocket was transported to Denel Overberg Test Range in the Western Cape where it was flight-tested in 2014. The launch campaign encompassed three technical objectives: to test the Phoenix program’s ground support equipment, to evaluate the launch countdown procedures and to test the vehicle itself. In addition, the campaign served to benefit ASReG’s human capital development program through the inclusion of former and current graduate students as part of the launch team. This paper describes the Phoenix-1A flight test which was monitored by an extensive array of tracking cameras and radars. The vehicle achieved an apogee of 2.5 km but suffered damage to its nozzle during launch. The probable cause of the damage is discussed, along with the outcome of each of the test objectives.

Structural Performance of Large Scale Paraffin Wax Based Fuel Grains

Paraffin wax has been identified as a high regression rate, liquefying fuel that can be used with nitrous oxide and other oxidizers as the solid component of a hybrid rocket propellant combination. The low viscosity and low surface tension of certain liquefying fuels allows for the development of small surface wave formations, and droplet entrainment into the oxidizer stream during the combustion process. This is the main contributing factor to the increased regression rate when compared to commonly used hybrid fuels such as HTPB and HDPE . Although significant work has been conducted in the field of combustion analysis of liquefying fuels, little investigation has been done on the structural performance of large scale grains. This paper investigates the structural performance of a pure paraffin wax fuel grain on the Phoenix-1A hybrid rocket and the proposed grain design of the larger Phoenix-2A vehicle. UKZN’s in-house Hybrid Rocket Performance Simulator software, HYROPS, is used to facilitate loading and regression rate predictions. Flight data from the Phoenix-1A launch is also considered along with an analysis of unconsumed grain that remained after motor burnout.

Preliminary Design of the Phoenix-1B Hybrid Rocket

Following the launch of UKZN’s Phoenix-1A hybrid rocket in August 2014, a revised vehicle design is now under consideration to replace the P-1A technology demonstrator. Designated P-1B, the 13 km apogee workhorse is to be less expensive and easier to manufacture so as to provide a reliable launch system for ongoing research into hybrid propulsion technology and to promote human capital development in aerospace design and launch operations. Using UKZN’s in-house tools (the Hybrid Rocket Performance Simulator (HYROPS) and Hybrid Rocket Performance Code (HRPC)), the rocket will be designed to take into account the lessons learnt in the P-1A program. This paper outlines the progress made to date in the design of Phoenix-1B’s nitrous oxide/aluminum-paraffin wax hybrid motor.