Using Rockets To Unify Topics In An Electro Mechanical Engineering Technology Instrumentation Course

Model rockets are being used at Penn State Berks to unify topics in an electro-mechanical engineering technology instrumentation course. Model rockets provide an exciting platform on which to carry many types of devices and sensors. Throughout the semester, several types of sensors and transducers are introduced and studied. Sensors include thermistors, micromachined accelerometers and integrated pressure transducers. The physics, construction and characteristics of these sensors are discussed in the course lectures. The students also receive hands-on experience with many of the sensors through the course’s laboratory experiments. Analog to digital conversion techniques and data acquisition systems are also studied in this course. To help pull together the topics and concepts discussed in class, a rocket payload data acquisition system is employed. As each device is studied, its application to the payload system is presented and discussed. A thermistor is used to measure the air temperature at various altitudes. A micromachined accelerometer is used to measure the acceleration of the rocket during launch and throughout the mission. Integrated silicon pressure transducers are used to measure both altitude and speed of the rocket. The axial speed of the rocket is determined by using the body of the rocket as a Pitot tube together with a differential pressure transducer. The timing, power management, control, measurement and data storage for the entire payload is handled by an embedded PICTM microcontroller. A rocket launch date is set near the end of the semester with a well-publicized formal countdown commenced well in advance of the launch to help promote interest and build excitement for the event. The students are active participants in the launch and recovery operations. The raw data collected during the flight is uploaded from the payload memory for interpretation and analysis by the students. A flight performance report based on the data is submitted by each student. This paper presents and discusses the details of the rocket system, the role of the project in the course and feedback from the students involved. Introduction The use of model rockets in engineering education is well documented 1-4 Students generally find working with model rockets an exciting way to learn engineering concepts. The experience usually takes the class out of the classroom and, due to the nature of model rocketry, this experience usually occurs on days of nice weather. The anticipation of a countdown and the thrill of watching the launch is an added bonus to the experience. Besides the pure enjoyment of a launch, the model rocket also makes an excellent platform on which to attach a plethora of useful educational payloads. The work presented here puts an emphasis on the sensor payload but also exploits the inherent fun as the catalyst to learning. As part of a junior-level instrumentation and measurement theory course at Penn State Berks, a model rocket packed with sensors is used to help unify the concepts of the course. This course is part of the electromechanical engineering technology program. In this course, the theory of temperature, pressure, fluid flow, displacement, velocity, and acceleration measurement are P ge 11408.2 covered in detail. Simultaneously, the laboratory component of the course provides the students the opportunity to get their hands on many of the sensors and transducers used to measure these physical quantities. To have a bit of fun with some of the sensors and help give the students a bigger picture of how they can be used, a portable data acquisition and logging system has been designed and implemented as a model rocket payload. Throughout the semester, as the theory and characteristics of various sensors are studied, the application of each to the rocket payload system is also discussed. Using the datasheets for each of the sensors, the students convert the raw data into the desired measured quantity. The students also determine the relationship between the quantities measured by each sensor (if there is any) to help collaborate and substantiate the recorded data. The significance of the data derived from each sensor in determining part of the rocket mission performance is also an important concept of the exercise. A formal mission performance report is submitted by each student containing their interpretation of the flight data. The model rocket launch date is scheduled near the end of the semester. This allows time for study of the pertinent devices and techniques prior to launch while still affording enough time for preparation of the flight report by the end of the semester. The countdown time is announced during each class meeting and is also displayed on the class webpage. This practice provides a cadence or metronome-like pace for the course which helps to keep a high level of student interest by providing a goal to work towards (or a light at the end of the tunnel?). System Overview: Hardware The physical layout is designed around the EZ Payloader model rocket manufactured by Quest Aerospacet. A diagram of the rocket is shown in Appendix A at the end of this paper. This rocket was chosen because of its unique payload section which is separate from the parachute stowing area. In model rocketry the parachute is deployed by the, “Ejection charge” that is produced by the rocket engine after the thrust charge is depleted. The ejection charge effectively forces the rocket stages to separate and propels the parachute(s) out of the storage chamber. By having a separate payload section, the sensors can be shielded from the violent pressure effects of the ejection charge. The diameter and length of the combined payload and hollow nose cone sections place constraints on the physical design. A two-sided printed circuit board (PCB) was designed to hold the control and data storage electronics. The PCB was designed with free software from ExpressPCB. The sensors are located within the payload and nose sections but not directly on the main circuit board. This arrangement allows for different types and packages of sensors to be used in future projects without changing the circuit board design. A block diagram of the data acquisition system hardware is shown in Figure 1. Power for the system is provided by a small 12V battery. The regulated 5V power supply for the electronics is controlled by the linear voltage regulator. An integrated circuit accelerometer is used to measure the acceleration of the rocket during launch and throughout the mission. An integrated silicon absolute pressure transducer is used to determine the altitude of the rocket by measuring the difference in atmospheric pressure during flight. The axial speed of the rocket is determined by P ge 11408.3 using the body of the rocket as a Pitot tube together with a differential (gauge) pressure transducer. A nominal 3kΩ thermistor is used to measure the air temperature at various altitudes. Sensor data is stored in a non-volatile 64kbit CMOS EEPROM memory device. The timing, power management, control, measurement and data storage for the entire payload is handled by an embedded microcontroller. A momentary contact switch, blue LED and serial port connections are located on the exterior of the rocket and are used for operator intervention, status and data retrieval respectively as described later.