3, 2, 1, Launch!
R. de Kat and G.N. Saunders-Smits
Faculty of Aerospace Engineering, Delft University of Technology, Delft, the Netherlands,
R.deKat@tudelft.nl, G.N.Saunders@tudelft.nl
Abstract
It is important that young people who chose to pursue a degree in engineering stick with their choice. Unfortunately students often loose their motivation during their first year. This paper gives an example of how the Faculty of Aerospace Engineering of Delft University in The Netherlands manages to keep a large number of freshmen motivated and at the same time acquaint them with the wonderful world of aerospace engineering through the design, build, launch and analysis of PET bottle based water-rockets.
Keywords: project education, water-rocket, aerospace engineering, freshmen retention
1. INTRODUCTION
Motivating young people to pursue a degree in engineering is the start, but once they have made their choice it becomes important to keep these engineering students motivated. It is from this point-of-view that from day one in the BSc degree programme at the Faculty of Aerospace Engineering of Delft University of Technology in Delft, The Netherlands, students are exposed to the realities of engineering life through a set of challenging and motivating projects that they have to complete [1]. These projects, in which students become more and more independent, are very successful and are in a large part responsible for the continued large enrolment of freshmen at the Faculty of Aerospace Engineering.
The project described in this paper is one of these projects. Started in 2001 this project has evolved into a mature project where students are able to experience first hand the reality of their lectures in aerodynamics, calculus, mechanics and space technology by taking part in the design, build, launch and analysis of a water rocket. The project has a study load of 3 ECTS (84 hours) and the typical enrolment of students in this project exceeds 400 freshmen each year. The project is part of a set of 7 projects in the first year at the Faculty of Aerospace Engineering. These projects have an overall workload of 280 hours that accounts for 16% of the overall workload in the first year. The aim of the projects is to have students apply the knowledge they gained during the lectures of aerodynamics, aeronautical and space engineering, and mechanics. The students apply the knowledge by solving problems on and acquiring insight into these subjects. Next to this the students learn how to work in teams, get an introduction on the use of laboratory equipment, and get insight into the challenges of performing measurements. Finally, students will discover the essential difference between theory and practice, a challenge professional engineers face on a daily basis.
The sheer number of freshmen taking part poses some serious organisational and logistical challenges for the lecturers involved. This paper describes the educational and organizational challenges of the project and how are they are met head on. This paper also hopes to inspire other lecturers to have, design, build, and operate educational projects that have serious engineering and science contents.
2. EDUCATIONAL BACKGROUND AND ORGANIZATION
To classify different educational projects Kolmos [2] and later De Graaff and Longmuss [3] distinguish three types of projects with an increasing ‘ownership’ by the students:
Assignment projects (AP) – Projects characterised by considerable planning and control by teachers/supervisors, where problem, methods and subject are chosen beforehand.
Subject projects (SP) – Projects where the teachers define the subject beforehand. Students have a free choice among a number of described methods.
Problem projects (PP) – Projects in which a problem is the starting point. The problem will determine the choice of disciplines and methods. The problem is chosen within a wider frame set by the teachers The water-rocket project is a typical assignment project that consists of fourteen project sessions. Each project session corresponds to a different chapter in the accompanying project reader [4]. The core subject of the project is a water-rocket that is made out of a PET soda bottle. Ten of the fourteen sessions are dedicated to discovering the theory about, build, test, and launch the water rocket. The four remaining sessions serve to write a report on the findings during the project and to perform two general wind tunnel experiments to further enhance the students’ understanding of the basics of aerodynamics.
Project education is traditionally characterised by a higher staff effort than traditional lectures. This is however offset by a higher pass rate as students learn more when they are more motivated to learn. At the Faculty of Aerospace Engineering in Delft with its high number of freshmen the organisation is not without challenges. The project is typically done in groups of ten students. A third year BSc or first year MSc student, who also acts as an academic mentor for this group of new students, supervises two groups to lighten the staff work load. This leads to a total of 36-44 project groups supervised by 18-22 teaching assistants. Each group will act as a team throughout the project. Only for the general wind tunnel experiments is the group split into two smaller groups this due to the wind tunnel size. An Aerodynamics lecturer and a Space Design lecturer have designed the academic content of the project with the support of a number of PhD and MSc students. The organisation and running of the project itself is done by an experienced PhD student, who is supported by a variety of technicians, non-academic instructors and of course the teaching assistants. The teaching assistants will act as role models to the students. To ensure quality the teaching assistants are familiarized with the material and practices covered during the project. They are prepared for these tasks by dedicated instructions for global affairs and for each separate project session [5]. This approach seriously reduces the traditionally high workload (for staff) associated with project education without a loss of quality.
During the project the students have a variety of resources at their disposal. The resources consist of wind tunnels, laboratories, and workshop for the practical work and 25 project rooms of 5 by 10 meters, each equipped with 8 PCs with Internet access, a whiteboard, a cupboard, a meeting table, and chairs for the literature surveys, theoretical assignments, and analysis of the experimental data. During the scheduled hours students have access to these rooms.
The design, build, launch and analysis of the water rocket have to be done in a certain order. This results in a total number of typically 40x14 sessions need to be planned in specific order in a period of seven weeks. An additional challenge is the availability of the resources: the wind tunnels, the laboratories, and the project rooms cannot be used simultaneously by all groups, which means that not all groups can work at the same time. Adding to the problems, the general schedule of the bachelor programme allows the project to be held in a limited number of blocks, possibly differing from week to week. However, so far it has been possible to adequately handle the scheduling issue.
3. PROJECT CONTENT
In this section the structure of the project sessions dedicated to the water-rocket will be described, followed by a short description of the contents of each session. Next the deliverables the students have to provide are described. Finishing with the description of the general wind tunnel experiments.
3.1 Structure of the project
The ten sessions of the project (and reader) dedicated to the water rocket each have their own theme and are listed in order below:
• Introduction to the water rocket part & General aspects of rockets. • Rocket engine performance.
• Thrust measurements.
• Design of the water rocket & Rocket stability. • Drag of the rocket.
• Production of the water rocket. • Testing and verifying the design. • Flight performance.
After the last session the students will have two additional four-hour project sessions to complete a final report. The project finishes with an evaluation with their direct teaching assistant and peer-evaluations by their fellow students. The two wind tunnel tests are scheduled where logistically possible.
3.2 Description of the Project Sessions
In this section a description of each session is given, briefly explaining its purpose, the main activities the students employ and the desired outcomes.
3.2.1 Project kick-off and Introduction
The project is started with a short introduction lecture (one hour) dealing with the general dos and don’ts during the project, followed the same day with an introduction covering general aspects of rockets. In this part the students are asked to do a literature study to answer a few simple questions dealing with rocket principles, in-flight stability, and performance issues. In this way the students will get familiar with the benefits of different rocket propellants, parameters to describe energy density of propellant, and principles of rocket propulsion.
3.2.2 Rocket Engine Performance
For the rocket engine performance session the students have to combine the law of conservation of momentum with Bernoulli’s principle and the continuity equation to formulate a theoretical expression for the thrust generated by the water rocket. The students use this expression to predict the thrust the water rocket will deliver. The prediction is put to the test in the thrust experiments.
3.2.3. Thrust Measurements
An experimental setup (figure 1) is used to determine water rocket thrust. The setup consists of a support where the bottle is mounted; a cork retainer; a force transducer; conditioning amplifier; oscilloscope and finally a computer for data storage and processing. The experiments give the students a direct comparison of theory with practice. First they will see and hear the difference between shooting with or without water. Then the students get the measurement data from their experiment and process the data to compare it with theory. This will be the first time they will be directly confronted with the fact that theory doesn’t need to match practice. The Bernoulli equation and law of conservation of momentum are not the correct way to describe the thrust phase, e.g. the assumptions for the Bernoulli equation don’t hold. However, the theory gives a good qualitative description and gives the correct trend in the thrust curve, so it will be used to investigate the influence of different parameters.
b a
FIGURE 1. Thrust measurements. (a) Action photograph of a bottle expelling water (b) Typical result from the measurements compared with theory
3.2.4 Design of the water rocket & Rocket stability.
After being impressed by the sonic boom from the thrust experiments the students have to make a preliminary design of the water rocket. This is a creative exercise, the boundaries being that the students have to design two water rockets that differ only in their nose cone design and that the design accounts for the physical space available on the launch platform. These preliminary designs will be used as guide for a theoretical survey of the rocket stability and drag.
FIGURE 2. Two very simple and practical ways to determine the centre of mass and the centre of pressure [6]
The rocket stability is assessed for different shapes of fins and nose cones. A literature study covers passive aerodynamic stability, weather-cocking, determining the centre of mass (figure 2), and two different methods for determining the centre of pressure, e.g. the Cut-out method (figure 2) and the Barrowman method [6].
3.2.5 Drag
The drag of the rocket is investigated by looking into pressure drag, skin-friction drag, and induced drag. The students are asked to look into the influences of the different drag contributions and investigate whether other forms of drag play a role in water rocket flight. After this the students make their final design based on the findings from their theoretical investigations. This design will be the blueprint for the rockets they will build.
3.2.6 Production
The production is the part where the students build their designs under supervision of their teaching assistant and the technician. They are supplied with the necessary materials and are even allowed to bring more exotic materials from home. After this project part they should have built two rockets differing only in the nose cone design. . b a d c
FIGURE 3. Drag & stability setups & results.
(a) Drag measurement setup with Dobbinga-balance in the M-tunnel (b) Stability setup in the W-tunnel
(c) Typical drag curve
3.2.7 Testing and Verifying of the Design
r stability and drag at the aerodynamics laboratory. Two low-speed
.2.8. Flight Performance
y data, like drag coefficients and stability estimates from experiment and theory the The rockets the students built are tested fo
wind tunnels are used with two dedicated setups (figure 3). The students acquire data for drag calculation and determine whether their rockets are stable (a mandatory safety check, not stable means no launch)
3
After obtaining the necessar
students estimate the trajectory of the rockets using Tsiolkovsky and WaRP. WaRP is a computer program created at Aerospace Engineering to give students insight in the different parameters that affect the trajectory of the water rocket. Typical output from WaRP is shown in figure 4. With these estimates the students make a prediction on the difference in apogee height the rocket will achieve to compete for the challenge.
FIGURE 4. Typi al WaRP result
.2.9 Launch and Trajectory determination
eck the predictions and the measurement skills of the students. The
.2.10 Report
aken and findings during the water rocket part have to be condensed into a report. During the
.2.11 Wind Tunnel Experiments
rts that cover general wind tunnel experiments. These experiments are done c
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With the gauntlet thrown down it is time to ch
boots, warm jacket, gloves are put on (the launch takes place in December) and on a launch field the students will shoot their rockets, measure the height the rockets achieve and compete in a challenge for the best influence prediction. From three observation stations elevation and azimuth angles are measured. The azimuth angles can be used to determine the distance “z” in figure 5 and with the elevation angle the height of the apogee “ha” can
be determined. The angles can also be used with some more geometry to determine “ha” in more than one way.
3
All the steps t
project the students write a report for each project part. The teaching assistants check these sub-reports and give feedback to the students on what to improve. The last two project parts are correcting and improving the sub-reports and make them into one final report on the water rocket.
3
During the project there are two pa
when the schedule allows it. The two experiments are the flow through a convergent-divergent channel and the flow around a bend. In these experiments the students get in touch with a simple wind tunnel and some basic measurement equipment, like a water-manometer, pressure-tubes, and pressure taps. The students are asked to measure the flow and to check whether the measured velocities match theory in form of the Bernoulli equation. The students write two separate measurement reports on their findings during these experiments.
a b
FIGURE 5. Launch!
(a) Actual launch of a rocket (N15C Dec. 2008) (b) Altitude measurement
4. RESULTS AND CONCLUSIONS
Launching water-rockets is often considered child’s play and many universities employ it either as a recruiting tool or the first attempt for students at design. At Delft University of Technology water-rockets have become serious business and with great success.
Over the years this project has shown to motivate first year students whilst at the same time letting them experience all pillars of an engineering degree: science, design, and practical application and their limitations. Students also get their first experience in teamwork. Unfortunately the Dutch educational system doesn’t allow for accurate tracking of the progress of students within the BSc programme. Therefore, to evaluate the project, student-questionnaires are held. Table 1 shows the results of one of these evaluation-questionnaires held in the academic year of 2005/2006. Overall it shows that the project has a positive effect on the students’ motivation and understanding. Next to the students, the staff is also very enthusiastic about the project, as the project motivates students and their enthusiasm motivates the teaching assistants, the PhD students and the staff. This common enthusiasm enhances the students’ motivation for their degree and therefore improves retention.
This paper shows that the traditional high staff work load associated with project education can be reduced through organisation and making use of motivated and trained teaching assistant and PhD students. Students, teaching assistants, PhD students and staff are motivated by each other during the project. This all shows that by using relatively simple means it is possible to keep students motivated throughout their degree resulting in higher retention of all those young people who are attracted to engineering.
Question: Blank + + + 0 - - - n/a Grade Rating
The project has .. in %
improved my understanding of aerodynamics
9 8 55 22 10 4 1 3.2 +
increased my motivation for aerodynamics
11 10 38 40 9 2 1 3.1 +
improved my understanding of space technology & engineering
13 3 36 36 19 5 2 2.7 0
increased my motivation for space technology & engineering
11 5 29 47 15 3 2 2.7 0
improved my ability to work in a team
14 20 60 17 2 1 0 3.7 +
Acknowledgments
The authors would like to give a special thanks to all the people who made it possible to run the project described in this paper (in random order): M. Kotsonis, J. Kreeft, G. Mignoli, L. Kram, H. Werges, P. den Dulk, E. Roessen, R. van der List, H. Weerheim, P. Duyndam, F. Donker-Duyvis, L. Boermans, L. Veldhuis, P. Lucas, F. Bos, B. Horsten, J. Saathoff, D. Passchier, B. Zandbergen, B. Boonstra, A. van Foreest, J. Koeleman, N. Konijnedijk, F. Koppenaal, H. Nyugen, J.-B. van der Steen, P. Zaal, E. van Breukelen, C. Brinkerink, R. Hamann, M. Jas, J. Morel, and all the teaching assistants.
References
[1] Saunders-Smits, G.N. and De Graaff, E., The development of integrated professional skills in aerospace, through problem-based learning in design projects, Proceedings of the 2003 American Society of Engineering Education, Session 2125, June 2003.
[2] Kolmos A., 1995, Reflections on project work and project based learning. Unpublished manuscript.
[3] Graaff, E. de and Longmuss, J. Learning from Project work: individual learning results versus learning in the group In A. Hagström (ed.) Engineering education: rediscovering the centre. Proceedings SEFI Annual conference 1999 (hochschulverlag AG an der ETH Zürich), pp. 129-134.
[4] de Kat, R. – Reader AE1-005AER Aerodynamics Project, Faculty of Aerospace Engineering, Delft University of Technology, Delft, 2008.
[5] Andernach, T. and Saunders-Smits, G.N., The use of Teaching-Assistants in Project Based Learning at Aerospace Engineering, Proceedings of the 36th ASEE/IEEE Frontiers in Education Conference, San Diego, 2006
