X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=core%2Fdoc%2Ftechdoc%2Fchapter-introduction.tex;fp=core%2Fdoc%2Ftechdoc%2Fchapter-introduction.tex;h=d756d990b142a741e6f53b8f221840ad32b87185;hb=84094f3e8b4e8d27310532c092ec9738156417d3;hp=0000000000000000000000000000000000000000;hpb=fc3d9fa48747ea14f7d77e573df16386c9fdf89e;p=debian%2Fopenrocket diff --git a/core/doc/techdoc/chapter-introduction.tex b/core/doc/techdoc/chapter-introduction.tex new file mode 100644 index 00000000..d756d990 --- /dev/null +++ b/core/doc/techdoc/chapter-introduction.tex @@ -0,0 +1,168 @@ + +\chapter{Introduction} + +Model rocketry is a sport that involves designing, constructing and +launching self-made rockets. Model rockets vary greatly in size, +shape, weight and construction from detailed scale models of +professional rockets to lightweight and highly finished competition +models. The sport is relatively popular and is often cited as a +source of inspiration for children to become engineers and +scientists. + +The hobby started as amateur rocketry in the 1950's when hobbyists +wanted to experiment their skill with building rockets. Designing, +building and firing self-made {\it motors} was, however, extremely dangerous, +and the American Rocket Society (now the American Institute of +Aeronautics and Astronautics, AIAA) has estimated that about one in seven +amateur rocketeers during the time were injured in their hobby. This +changed in 1958 when the first commercially-built model rocket +motors became available. Having industrially-made, reasonably-priced +and safe motors available removed the most dangerous aspect of amateur +rocketry. This along with strict guidelines to the design and +launching of model rockets formed the foundation for a safe and +widespread hobby.~\cite[pp.~1--3]{stine} + +Since then model rocketry has spread around the globe and among all +age groups. Thousands of rockets ranging from 10~cm high miniatures +to large models reaching altitudes in excess of 10~km are launched +annually. Model rocket motors with thrusts from a few Newtons up to +several kilo-Newtons are readily available. Since its forming in +1957, over 90\s000 people have joined the National Association of +Rocketry (NAR) in the U.S. alone. +% Model rocketry is used as an +%educational device in numerous of schools and by many youth +%organizations. + +In designing rockets, the {\it stability} of a rocket is of central +priority. A stable rocket corrects its course if some outside +force disturbs it slightly. A disturbance of an unstable rocket +instead increases until the rocket starts spinning in the +air erratically. As shall be discussed in +Section~\ref{sec-stability}, a rocket is deemed +{\it statically stable} if its center of pressure (CP) is aft of its +center of gravity (CG)\footnote{An alternative term would be + {\it center of mass}, but in the context of model rocketry, we are + interested in the effect of gravity on the rocket. Thus, the term + center of gravity is widely used in model rocketry texts, and this + convention will be followed in this thesis.}. +The center of gravity of a rocket can be easily calculated in advance +or determined experimentally. The center of pressure, on the other +hand, has been quite hard to determine either analytically or +experimentally. In 1966 James and Judith Barrowman developed an +analytical method for determining the CP of a slender-bodied rocket at +subsonic speeds and presented their results as a research and +development project at the 8th National Association of Rocketry Annual +Meeting (NARAM-8)~\cite{barrowman-rd}, and later as a part of James +Barrowman's Master's thesis~\cite{barrowman-thesis}. This method has +become known as the {\it Barrowman method} of determining the CP of a +rocket within the model rocketry community, and has a major role in +determining the aerodynamic characteristics of model rockets. + +Another important aerodynamic quantity of interest is the +{\it aerodynamic drag} of a rocket. Drag is caused by the flow of air +around the rocket and it can easily reduce the maximum altitude of a +rocket by 50--80\% of the otherwise theoretical maximum. Estimating +the drag of a model rocket is a rather complex task, and the effects +of different design choices are not always very evident to a +hobbyist. + +Knowing the fundamental aerodynamic properties of a rocket allows one +to simulate its free flight. This involves numerically integrating +the flight forces and determining the velocity, rotation and position +of the rocket as a function of time. This is best performed by +software designed for the purpose of model rocket design. + +RockSim~\cite{rocksim} is one such piece of software. It is a +commercial, proprietary program that allows one to define the geometry +and configuration of a model rocket, estimate its aerodynamic +properties and simulate a launch with different rocket motors. It has +become the {\it de facto} standard software for model rocket +performance estimation. However, as a proprietary program, it is +essentially a ``black-box'' solution. Someone wishing to study or +validate the methods will not be able to do so. Similarly extending +or customizing the functionality or refining the calculations methods +to fit ones needs is impossible. The software is also only available +on select operating systems. Finally, the cost of the software may be +prohibitive especially for younger hobbyists, voluntary organizations, +clubs and schools. + +Open Source software, on the other hand, has become an increasingly +competitive alternative to proprietary software. Open Source allows +free access to the source code of the programs and encourages +users with the know-how to enhance the software and share their +changes~\cite{oss-principles}. Success stories such as the Linux +operating system, the OpenOffice.org office suite, the Firefox web +browser and countless others have shown that Open Source software can +often achieve and even exceed the quality of expensive proprietary +software. + + +\section{Objectives of the thesis} + +The objectives of this thesis work are to: +% +\begin{enumerate} +\item Develop and document relatively easy, yet reasonably accurate + methods for the calculation of the fundamental aerodynamic + properties of model rockets and their numerical simulation; + +\item Test the methods developed and compare the results with other + estimates and actual experimental data; and + +\item Implement a cross-platform, Open Source model rocket design and + simulation software that uses the aforementioned methods, is at the + same time easy to use and yet versatile, and which is easily + extensible and customizable for user requirements, new types of rocket + components and new estimation methods. +\end{enumerate} + +The methods presented will largely follow the methods developed by +Barrowman~\cite{barrowman-rd,barrowman-thesis}, since these are +already familiar to the rocketry community. Several extensions to the +methods will be added to allow for more accurate calculation at larger +angles of attack and for fin shapes not accounted for in the original +paper. The emphasis will be on subsonic flight, but extensions will +be made for reasonable estimation at transonic and low supersonic +velocities. + +The software developed as part of the thesis is the OpenRocket +project~\cite{openrocket}. It is an Open Source rocket development +and simulation environment written totally in Java. The program +structure has been designed to make full use of object oriented +programming, allowing one to easily extend its features. The software +also includes a framework for creating user-made +{\it listener components} (discussed in Section~\ref{sec-listeners}) +that can listen to and interact with the simulation while it is +running. This allows a powerful and easy way of interacting with the +simulation and allows simulating for example guidance systems. + +One possible future enhancement that has also specifically been +considered throughout the development is calculating the aerodynamic +properties using computational fluid dynamics (CFD). CFD calculates +the exact airflow in a discretized mesh around the rocket. This would +allow for even more accurate calculation of the aerodynamic forces for +odd-shaped rockets, for which the methods explained herein do not +fully apply. + +It is anticipated that the software will allow more hobbyists the +possibility of simulating their rocket designs prior to building them +and experimenting with different configuration, thus giving them a +deeper understanding of the aerodynamics of rocket flight. It will +also provide a more versatile educational tool since the simulation +methods are open and everyone will be able to ``look under the hood'' +and see how the software performs the calculations. + +In Chapter~\ref{chap-basics} a brief overview of model rocketry and +its different aspects will be given. Then in +Chapter~\ref{chap-aerodynamics} methods for calculating the +aerodynamic properties of a general model rocket will be presented. +In Chapter~\ref{chap-simulation} the aspects of simulating a rocket's +flight are considered. Chapter~\ref{chap-software} then explains how +the aerodynamic calculations and simulation are implemented in the +OpenRocket software and presents some of its features. In +Chapter~\ref{chap-experimental} the results of the software simulation +are compared with the performance of constructed and launched rockets. +Chapter~\ref{chap-conclusion} then presents a summary of the +achievements and identifies areas of further work. + +