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The importance of interdisciplinary education is increasingly prominent. The production and launch of water rockets are closely related to multiple disciplines, making it suitable to design them as interdisciplinary education projects. This article reviews the current research status of water rockets and deeply explores their educational value. Based on the characteristics and limitations of traditional water rockets, an innovative design and development of a low-cost “smart water rocket” aimed at interdisciplinary education is proposed, providing case references and experience for the innovative development of interdisciplinary education projects.
Innovative Design and Development of Smart Water Rockets for Interdisciplinary Education
Written by | Gong Jiaxin, Zhong Baichang
The trend of comprehensive interdisciplinary development has brought interdisciplinary education into people’s view. The term interdisciplinary is not unfamiliar to people; whether it is “cultivating well-rounded individuals” or “the integration of five educations”, the shadow of interdisciplinary education is subtly present. Interdisciplinary education refers to the integration and learning of concepts from multiple disciplines to form a major interdisciplinary concept, using this major interdisciplinary concept to solve interdisciplinary problems that cannot be solved or thoroughly addressed by a single discipline. In the process of solving interdisciplinary problems, students’ interdisciplinary thinking is gradually cultivated, thereby promoting the development of students’ innovative abilities. As an educational activity that breaks the boundaries of disciplines, interdisciplinary education has increasingly become the focus of educational reform and development. The Ministry of Education’s “Compulsory Education Curriculum Program and Curriculum Standards (2022 Edition)” frequently mentions the term interdisciplinary and adds interdisciplinary thematic learning activities in various subject curricula to strengthen the interconnection between subjects and promote the comprehensive implementation of curricula. It can be said that interdisciplinary education has become an important direction and a powerful tool for curriculum reform in the new era.
Currently, there are many outstanding teaching projects emerging in interdisciplinary practical activities, typically represented by STEM education. Water rockets are models designed using mass ratios and air pressure, easy to make, highly exploratory, and creative. As a classic teaching case in physics, they can be designed from various angles, possessing rich interdisciplinary educational value. The “Compulsory Education Physics Curriculum Standards (2022 Edition)” clearly states that water rockets are suitable materials for interdisciplinary education. Unfortunately, current teaching projects based on water rockets are mostly limited to the explanation of production steps and methods, and their functional designs are singular, with low reuse rates. Essentially, they still belong to experiential learning activities and fail to fully reflect the practice-oriented innovative interdisciplinary education concept, which is not conducive to the formation of students’ interdisciplinary thinking or the cultivation of their innovative abilities. Therefore, deeply exploring the interdisciplinary educational value of water rockets and innovatively designing water rocket projects aimed at interdisciplinary education has significant research value.
1. Research Exploration of Traditional Water Rockets
Currently, educational research and practice on water rockets mainly focus on two categories: production modification and launch exploration, both aiming to optimize the flight trajectory of water rockets to make them fly higher and further. The production modification category aims to use different materials and production methods to achieve the highest possible launch speed and the lowest possible air resistance for the water rockets. The launch exploration category focuses on the factors affecting the flight of water rockets and finds the optimal launch methods and angles through multiple experiments.
The research directions for modifying water rockets are quite diverse. For instance, to increase the acceleration of the water rocket, Wang Hai and students used bicycle valve cores and hoses to connect two cola bottles in series, creating a two-stage pressurized water rocket. After launch, a pressure difference was generated between the first and second stages, allowing the hose between the two rocket bodies to detach and achieve secondary acceleration of the water rocket. At the same time, a parachute was made for the water rocket, utilizing the different air resistances experienced by light and heavy objects, causing the rocket body to naturally flip after launch, thus deploying the parachute. Moreover, Li Jiang and others improved a multi-stage single-body three-boost water rocket based on the Long March 3 carrier rocket design, bundling three boosters next to the main rocket body, with four nozzles spraying downwards simultaneously. When the water in the boosters is exhausted, they automatically detach, allowing the main rocket to continue ascending, achieving a range of up to 500 meters. Considering the poor stability of gravity-deployed parachutes, they used a time-delay relay to automatically deploy the parachute. Additionally, Jiang Tao and others stepped outside the physical modification discussion of water rockets, replacing the water in the water rocket with hydrogen peroxide (H2O2) solution, guiding students to try adding different catalysts to generate a large amount of gas inside the rocket body through the reaction between the catalyst and hydrogen peroxide, observing changes in internal pressure. Experiments found that using hydrogen peroxide and potassium iodide (KI) as catalysts significantly improved the flight performance of the water rocket.
Compared to the modification of water rockets, the research on launch exploration is more concentrated, mainly focusing on four influencing factors: launch angle, water quality, launch pressure, and rocket body shape. For example, Yang Huidi and others explored the impact of these four factors on the flight distance of water rockets from both theoretical and experimental perspectives. They used the control variable method to explore the flight effects of water rockets under the influence of each factor and conducted theoretical analysis of the experimental data processing results, revealing the flight states and force relationships at each stage of the water rocket’s flight. Furthermore, to cultivate students’ engineering thinking and creative abilities, Zhu Shengyan designed the water rocket as a teaching project in the general technology subject, allowing students to independently produce water rockets and explore the factors affecting their flight. They cleverly used the water rocket target shooting experiment to stimulate students’ inquiry awareness, guiding students to try different production methods and optimal launch techniques for water rockets.
Overall, whether modifying water rockets or experimenting with flight factors, many scholars have conducted thorough explorations in this area, with some creative structural modifications and experimental designs. However, existing research mostly remains limited to how to enhance the launch performance and effectiveness of water rockets. Undoubtedly, this is an important part of water rocket research, but as a material for interdisciplinary education that emphasizes learning through doing, the educational value of water rockets cannot be overlooked. Simply pursuing how to improve the performance of water rockets without considering their educational aspect may lead water rocket research astray. High costs and specialization have turned water rockets into research tools for a small group of enthusiasts rather than teaching tools, hindering the popularization and promotion of water rockets and overshadowing their rich educational significance. Therefore, analyzing the current characteristics and limitations of water rockets and innovatively designing water rockets suitable for interdisciplinary education is an urgent task for the value shift of water rocket research.
2. The Interdisciplinary Educational Value of Water Rockets
It is undeniable that the launch principle of water rockets is highly related to the mechanics content in physics, so interdisciplinary teaching projects based on water rockets cannot do without physics knowledge. However, the close relationship between the launch principle of water rockets and physics has led to the current teaching forms often being dominated by physics alone, neglecting the roles of other subjects in this project. In this regard, exploring innovative designs for water rockets from the perspective of interdisciplinary education is an important entry point to transcend existing teaching designs.
Water rocket projects based on an interdisciplinary perspective require organic integration of knowledge from science, technology, engineering, and mathematics in both design and production stages. During the launch process, it will also involve physics and chemistry-related knowledge such as rocket launch principles and liquid fuels. Therefore, the production and launch of water rockets belong to the category of interdisciplinary fields, representing a broader range of subjects and stronger applicability in interdisciplinary education, as shown in Table 1.
Table 1: Subjects Involved in Water Rockets and Their Educational Content
3. Innovative Design of the Smart Water Rocket
(1) Limitations of Traditional Water Rocket Design
From an educational perspective, the limitations of traditional water rocket design mainly manifest in the following three aspects.
1. Focus on Physics, Failing to Break Out of Conventional Thinking
When it comes to water rockets, teachers and students have implicitly agreed that they belong to the realm of physics. The main purpose of producing water rockets is to experience the interactions of forces and other physics knowledge. Students tend to stay at the stage of making and testing simple water rockets, showing low creativity and having a shallow understanding of knowledge from subjects outside physics, making it difficult to achieve optimal learning outcomes. In previous studies, some researchers have attempted to explore the educational value of water rockets in chemistry, mathematics, general technology, and other subjects, implementing water rocket teaching projects and achieving certain results, which is undoubtedly a good start for interdisciplinary teaching of water rockets. However, the aforementioned subjects still have a strong connection with water rockets, which can be seen as part of traditional educational research on water rockets and have not broken out of conventional thinking to explore the educational potential of water rockets in combination with other subjects.
2. Experimental Exploration is Similar, Lacking Vertical Height Data
Currently, researchers only consider the horizontal range of water rockets when exploring the factors affecting their flight, without incorporating the vertical height of the water rocket into the experimental exploration. Most of the research on influencing factors is limited, leading to highly similar experimental designs. In teaching, competitions based on water rockets are almost always about comparing their longest flight distance, making it impossible to compare their maximum launch height. On one hand, the absence of water rocket launch height data inevitably prevents effective exploration of some key influencing factors on water rocket flight (such as air resistance); on the other hand, comparing the launch distance of water rockets requires a large and open launch site, which is difficult for some small-sized middle and primary schools to conduct water rocket teaching project experiments.
3. High Difficulty in Recovering Components, Difficult to Open Parachutes Steadily and Accurately
In previous studies, some researchers equipped the main body of the water rocket with parachutes but did not consider the recovery needs of separated rocket bodies or boosters in the air. After detaching from the main body, the falling speed of the separated components is high, making it difficult to control the landing point, which is not conducive to protecting students’ safety and also difficult to reuse, hindering cost control. A deeper issue is that even if the main body of the rocket is equipped with a parachute, the gravity-deployed parachute device has randomness; the opening of the parachute is affected by various factors, making this opening method unstable and prone to failure. Although the automatic parachute opening device using a time-delay relay can greatly improve the success rate of opening, the timing of the delay cannot be accurately set, potentially leading to situations where the parachute opens before reaching the highest point or fails to open even after landing.
(2) Innovative Highlights of the Smart Water Rocket
To address the above issues, the key lies in obtaining the launch height of the water rocket. If knowledge and technology from other subjects can be combined to accurately record the launch height of the water rocket while optimizing the parachute opening method, the problems faced by traditional water rockets can be easily resolved, and new research space for water rockets can be expanded. Following this innovative design idea, the innovative design of the “smart water rocket” aimed at interdisciplinary education emerged, characterized by the following features.
1. Combining Information Technology to Use Sensors for Height Acquisition
To obtain the launch height of the water rocket, there are no good methods for traditional water rockets, often relying on rough visual estimates with significant errors. The information technology subject can guide students to use information technology tools to deeply integrate the physical world with the digital world, using information technology to acquire and process information, thereby creatively solving problems. To obtain the launch height of the water rocket, teachers and students can combine sensor knowledge and technology involved in the information technology subject to equip the “smart water rocket” with a sensor module, using state changes such as air pressure, temperature, and altitude during the water rocket’s flight to obtain the launch height. This not only expands the educational value of water rockets in the information technology subject but also represents a creative innovation of traditional water rocket design.
2. Recording Real-Time Height to Provide Data Support for Experiments
One of the important reasons for the similarity of water rocket exploration experiment designs is that it is impossible to explore the changes in flight height during the launch process, limiting the analysis of the flight state of the water rocket from limited angles. To explore the influencing factors of water rocket flight more accurately, based on the previous use of the sensor module to provide flight height data for the water rocket, students can record the real-time height of the water rocket obtained from the sensor measurements, using data storage modules or other technical means to save the information. After the water rocket launch is completed, combining other easily measurable and obtainable flight data, teachers can guide students to conduct comprehensive data processing, providing a more comprehensive and detailed data support for exploring the flight factors of water rockets, filling the data gap in important observational dimensions of water rocket research and enhancing the scientificity of the research conclusions.
3. Optimizing Descent Method with Automatic Parachute Opening During Descent
Traditional water rockets often descend at high speeds, which can be dangerous. Both gravity-deployed and time-delay parachute opening methods reduce the descent speed to some extent but sacrifice the launch performance of the water rocket. The gravity-deployed method increases the mass of the water rocket by placing heavy objects in the nose cone; the time-delay method often opens the parachute later in the descent to avoid affecting the upward trajectory, at which point the water rocket is descending quickly and close to the ground, rendering the parachute’s effect minimal. The optimization plan is to automatically open the parachute during the early to middle stages of the water rocket’s descent, which not only does not affect the launch of the water rocket but also greatly slows down the descent speed, making the landing point controllable. This ensures student safety while protecting the water rocket intact and reducing expenses.
4. Iterative Development of the Smart Water Rocket
(1) From Water Rocket to Smart Water Rocket
Based on the analysis above, combined with the basic structure of traditional water rockets, the specific development plan for the “smart water rocket” is shown in Figure 1. Based on the development plan, Figure 2 outlines the entire launch process of the “smart water rocket”.
Figure 1: Development Plan of the Smart Water Rocket
Figure 2: Launch Process of the Smart Water Rocket
Unlike the integrated design of traditional water rockets, the “smart water rocket” divides the rocket body into two parts: the propulsion compartment and the equipment compartment. The propulsion compartment, based on the structural design of traditional water rockets, is connected to the tail of the rocket and is mainly used to store the water needed for launching the “smart water rocket”. The propulsion compartment must ensure a closed environment and pressure requirements for the water rocket launch. Its lower part is also equipped with four tail fins to maintain the flight stability of the “smart water rocket”.
The equipment compartment is used to store the functional components required for the “smart water rocket” and cannot be connected to the propulsion compartment, maintaining the airtightness of the propulsion compartment and preventing functional components from being damaged by water. The equipment compartment also needs to have some openings to facilitate the operation of sensors and other components. To effectively utilize the space in the nose cone, the parachute is placed inside the nose cone. This decision is based on two considerations: first, if the parachute is placed in the equipment compartment, it may get tangled with the sensor’s cords; second, if a dedicated space is designed for the parachute, the size of the “smart water rocket” would need to be increased, reducing the performance of the water rocket.
2. Function Implementation
Figure 3 illustrates the connection diagram of the functional components of the “smart water rocket”. Compared to traditional water rockets, the “smart water rocket” is equipped with a height measurement module, data recording module, and servo, enabling height data acquisition and recording for the water rocket, while also controlling the automatic opening of the parachute during descent. The entire set of components is controlled and powered by an Arduino UNO control board and a lithium battery. The height measurement module uses a BMP388 barometric height sensor, which can calculate the current altitude of the water rocket based on changes in air pressure at different heights, ensuring high accuracy. The data recording module records the data measured by the sensor at regular intervals, facilitating data processing and analysis after launch.
Figure 3: Connection Diagram of Functional Components of the Smart Water Rocket
The automatic parachute opening device mainly consists of a servo and two rubber bands. One end of each rubber band is fixed to the nose cone, while the other end of the front rubber band hooks onto the servo’s arm, and the back rubber band is fixed to the equipment compartment. The two rubber bands pull the nose cone from both sides to keep it balanced. When the control board detects that the height measured by the height sensor has decreased compared to the last measurement, it sends a signal to the servo, causing it to rotate the arm, releasing the front rubber band while the back rubber band remains taut, thereby tilting the nose cone backward and allowing the parachute to fly out and open.
(2) Iterative Improvement of the Smart Water Rocket
1. Initial Version of the Smart Water Rocket
Based on a detailed development plan, the research team completed the initial version of the “smart water rocket” using environmentally friendly low-cost materials (as shown in Figure 4a). The initial version is primarily made by connecting two 1.25 L beverage bottles. A partition is used in the equipment compartment and nose cone to separate the parachute from various functional components. As shown in Figure 4b, the control board is vertically placed inside the equipment compartment, with its switch button exposed through a small hole for easy activation of functional components. The height sensor is fixed externally to the equipment compartment, and the servo arm extends vertically from the equipment compartment to hook onto the front rubber band. The equipment compartment also contains an OBLOQ IoT module and a micro lithium battery. The IoT module can be regarded as a data recording module, which can directly send the acquired height data to the server terminal for viewing after logging in. The parachute is made from a garbage bag, and when the parachute is laid flat, it is circular, with several cotton threads evenly fixed around the edge as parachute strings.
Figure 4: Initial Version of the Smart Water Rocket and Details of the Equipment Compartment
After completing the initial version, the research team tested its flight performance in an open space. During vertical test launches, it was found that the performance was not ideal. Firstly, the flight height was insufficient. As shown in Figure 5, the data reported by the IoT module indicated that the altitude of the water rocket changed by about 11 meters during the launch process. Secondly, the parachute opened too late and was affected. On one hand, the time interval for the “smart water rocket” to record data and determine whether to open the parachute was 0.8 seconds, which was too long, causing the water rocket to have already descended a significant height between two judgments; on the other hand, the current from the IoT sending messages interfered with the servo controlling the parachute opening, leading to instances where the parachute did not open during the descent. Finally, the parachute’s ability to slow down was inadequate. Due to the size limitation of the garbage bag, the diameter of the circular parachute was constrained, resulting in a small force area and poor deceleration effect.
Figure 5: Initial Version Height Data
2. Final Version of the Smart Water Rocket
In response to the issues encountered during the launch of the initial version, the project research team gradually sought solutions and iteratively improved the design, culminating in the final version of the “smart water rocket” (as shown in Figure 6). Compared to the initial version, the final version underwent four main improvements.
Figure 6: Final Version of the Smart Water Rocket and Details of the Equipment Compartment
First, the 1.25 L beverage bottles were replaced with 2 L bottles. The increased volume of the beverage bottle enhanced the propulsion of the water rocket, while allowing the control board to be placed horizontally inside, reducing the height of the equipment compartment and effectively increasing the launch height of the water rocket.
Second, the measurement interval was shortened to 0.5 seconds, and the height difference for determining descent was reduced to 0.8 meters. After multiple tests, the measurement interval and descent height difference were adjusted to a suitable range, minimizing judgment time and error.
Third, the data recording module was changed from the original IoT module to an EEPROM data storage module. This change eliminated the interference from the IoT feedback signal on the servo, allowing the main control board to be connected to a computer after launch to display or export flight data conveniently.
Fourth, the circular parachute was replaced with a rectangular parachute. The rectangular parachute could more effectively utilize the shape of the garbage bag, increasing the force area of the parachute and effectively reducing the descent speed of the water rocket.
The research team conducted launch experiments on the final version of the “smart water rocket”. As shown in Figure 7, the improved “smart water rocket” achieved a launch height of 43 meters. Meanwhile, the height measurement module recorded accurate data, clearly showing the flight states of the water rocket at various stages, providing reliable evidence for subsequent research.
Figure 7: Flight Height Curve of the Smart Water Rocket
Based on this analysis, the “smart water rocket” can serve as a relatively complete and educationally valuable material for interdisciplinary education, around which rich interdisciplinary teaching projects can be designed. For example, the reverse engineering teaching model proposed by my team can briefly outline the basic teaching process of the “smart water rocket” teaching project. First, teachers prepare relevant materials about water rockets or create simple water rockets for students to test, allowing them to perceive the launch process and principles of water rockets. Next, teachers guide students to explore the flaws of simple water rockets, such as the inability to accurately measure flight height, encouraging them to carefully observe the structure of the water rockets and comprehensively consider feasibility and innovation to design solutions, using materials at hand to create and test their water rockets, iterating improvements based on test results. Finally, teachers need to evaluate students’ works, potentially organizing a height competition for water rockets while using launch data to explore the influencing factors of water rocket flight, allowing students to learn through play, doing, and competition, continuously enhancing their innovative capabilities and interdisciplinary practical skills. If conditions permit, additional teaching content related to language and art can be integrated into the teaching project, guiding students to appreciate related poetry or beautify their own water rockets, cultivating their patriotic spirit and aesthetic ability.
5. Conclusion and Insights
Currently, there is a lack of interdisciplinary teaching projects in primary and secondary schools that are both interesting and challenging, while some STEM courses are costly and difficult to implement. This article, based on the actual teaching needs of primary and secondary schools, focuses on the field of interdisciplinary education and designs a low-cost “smart water rocket” that can record height. This not only makes knowledge explicit and broadens the data dimensions of water rocket exploration experiments but also achieves a deep integration of information technology with other subjects, uncovering the interdisciplinary educational value of water rockets combined with information technology. The “smart water rocket” serves as a vivid example of developing interdisciplinary teaching projects and provides references and insights for subsequent interdisciplinary teaching projects. The research team offers the following suggestions.
(1) Choose Appropriate Interdisciplinary Educational Materials
The ultimate goal of interdisciplinary education is to promote students to connect theory and practice through the implementation of interdisciplinary teaching projects, thereby enhancing their interdisciplinary innovative abilities. To make students interested and engaged, the educational materials must stimulate their curiosity, allowing them to learn while playing. Only by fully utilizing students’ learning enthusiasm and integrating education with entertainment can good results be achieved. Therefore, when selecting interdisciplinary educational materials, it is essential to focus on real-life situations, choosing issues that are common, interesting, and closely related to students’ lives and studies.
(2) Discover the Interdisciplinary Educational Value of Projects
The characteristic of interdisciplinary education lies in the integration of knowledge concepts from multiple disciplines, enabling students to combine clearly defined knowledge and techniques from different subjects into a unified whole, applying what they have learned to solve real-world problems. When developing interdisciplinary teaching projects, it is crucial not to mechanically overlay knowledge from various subjects but to deeply explore the educational value of the project in each subject, innovatively designing interdisciplinary teaching projects based on the actual situation of the project.
(3) Focus on Effectively Conducting Interdisciplinary Educational Practices
When developing interdisciplinary teaching projects, it is also necessary to consider whether they can effectively conduct interdisciplinary educational practices. First, consider the difficulty level of project practices; they should not be too difficult or too easy. Second, consider the teaching costs of the project; the materials and components required should be easy to obtain and low-cost, ideally reusable. Finally, the significant value of interdisciplinary educational practices lies not only in enabling students to grasp interdisciplinary concepts but also in helping them form problem-solving mindsets and innovative abilities during interdisciplinary learning.
Overall, the “smart water rocket” utilizes water rockets as interdisciplinary educational materials, integrating information technology to give water rockets “intelligence,” making it suitable for practical implementation as a low-cost interdisciplinary teaching project in primary and secondary schools, representing an effective attempt at innovative design and development of interdisciplinary teaching projects.
Note: This article is a research achievement of the 2022 Guangdong Province Graduate Education Reform Research Key Project “Research on the 4C Teaching Model for Cultivating Interdisciplinary Innovative Abilities of Master’s Students”.
(Authors: Gong Jiaxin is a master’s student at the College of Educational Information Technology, South China Normal University; Zhong Baichang is a professor and doctoral supervisor at the College of Educational Information Technology, South China Normal University, and the corresponding author of this article.)
Source | “Digital Teaching in Primary and Secondary Schools” 2022, Issue 9
WeChat Editor | Li Zhonghua, Fu Yuqing (Intern)
WeChat Supervisor | Zhao Manshu
