2 week water propelled rocket

Transcription

1 week water propelled rocket INTRODUCTION A few minutes on the web turns up a lot of information on water propelled rockets which students will inevitably access. In assessing the students work therefore we need to concentrate on their ability to work things out for themselves rather than simply copying ideas from the web. The rocket The week rocket will consist of a plastic drinks bottle. The students will be able to choose between 0.5, 0.33, 0.5,,.5 and litre bottles. The cap can be fitted with a length of plastic tubing (the nozzle) with a diameter of????? (check on available sizes). Students will be expected to produce calculations supporting their chice of bottle size and nozzle diameter. Fins and a nose cone may be added, but at this stage it is unlikely that supporting calculations will have been performed. The optimum volume of water to add will also have been established through calculation. The week rocket will include the addition of a fins for stabilisation and a nose cone to reduce drag and to enclose a battery powered altimeter which will also be ed and built. The launcher An O ring on the bottle forms a seal with the launcher tube. The bottle is restrained by cable ties located on the bottle flange and held in place by an outer release ring. When the release ring is pulled downwards, the cable ties deflect outwards releasing the bottle. The cable ties are fixed using a jubilee clip. A similar arrangement is used at the other end of the launcher tube to hold the neck of a bottle in place, but in this case the outer ring is fixed in place. The launcher tube is mounted on a frame made from mm plywood.

2 OBJECTIVES Week ) To and build a launcher and simple rocket propelled rocket. ) To establish a safe working pressure for the pressure vessel (PET plastic drinks bottle) through calculation and experiment. 3) Identify parameters and make informed decisions on their values. (Size of pressure vessel, working pressure, initial volume of water, nozzle diameter). 4) To undertake calculations to predict the rocket. Performance will be measured as the maximum height achieved. 5) To a launcher using the construction materials available. 6) To build the launcher and rocket. 7) To test the rocket and compare predicted and measured. 8) To write a report and make an oral presentation on the work. Week ) To use the prediction model to optimise the. ) To undertake stability calculations and fins to improve stability in flight whilst minimising drag. 3) To minimise aerodynamic drag by the addition of a suitable nose cone. 4) To make the necessary alterations to the rocket. 5) To and build an altimeter and install it in the nose cone of the rocket. 6) To test the rocket and compare predicted and measured. 7) To write a full report and make an oral presentation on the work. ORGANISATION Ideally I would like to provide only four deadlines for the students (the two rocket test times and deadlines for the report and oral). We would also inform them of the lecture times and the availability of each facility. We would use a timetable (see below) as a guide to what we would expect students to be doing when. In the first year of operation we may want to ensure success by being more presciptive by ensuring students stick to the timetable. FACILITIES e-lectures (Powerpoint presentations with recorded commentary on VITAL). Available 4/7. ) Thermodynamics for adiabatic expansion of air ) Fluid Mechanics of flow through a nozzle to determine thrust 3) Stresses in a cylindrical pressure vessel 4) Trajectory of a projectile with thrust 5) Optimisation 6) Stability 7) Altimeter 8) Drag Workroom Room with tables and chairs, preferably with one table to accommodate each student group of 5. Room 308 or the DO in Civil Engineering would be suitable. The room will need to be available 9-5, but supervision may not be needed during the whole of that period.

3 The bottles used for the pressure vessel will require pressure testing to at least.5 times the working pressure. This will be done in a ated area of the workroom. The bottles will be full of water to minimise the stored energy once pressurised using the workshop cycle pumps. Safety goggles will need to be worn. Material and tool requirements are given in Appendix. Staff advice Students will need to consult with staff at specified times during the day. I would suggest perhaps 4 staff for an hour (i.e. about 0 minutes per student team per day). We can do this in a number of different ways ) Staff members are available for a fixed period and students consult with them as necessary. ) Each group has a fixed appointment to meet with a staff member. 3) Students book an appointment with a member of staff. This would hopefully lead to students asking specific questions rather than we don t know what to do. 4) Staff act as facilitators at the student team meetings. (This would require more staff if they are to be present throughout). Test site Available test mornings only The university sports fields, which are reasonably close to the Halls of Residence, would seem to be a good choice. Testing will need to be undertaken during daylight (mornings) in December/February. Access to a club room or similar would be advantageous if the weather is very cold or wet. Access to a water tap is also necessary. ASSESSMENT Common format agreed for ENG00 and ENG0 modules. A report and oral presentation will be required after week and week. The orals will take place during the first semester examination period and in weeks or 3 of the second semester. 3

4 Suggested Timetable Monday Tuesday 9-0 Lecture Introduction to TWR. Milestones. 9-0 Lecture Defining parameters. Available hardware. 0- Team Team organisation. Initial task assignment. 0- Team Discuss plans for predicting -.30 Activity Initial research on water powered rockets -.30 Activity Destructive pressure testing of bottles Team Initial ideas for Team Decision on pressure vessel and working pressure e-lectures on Development of model. Initial development of model Performance model and initial calculations Wednesday Thursday Friday 9-0 Lecture 9-0 Lecture Practical considerations Travel to test site 0- Team Agree strategy for establishing parameters Team Agree on final Rocket testing Xmas/Exam break Oral presentation during first semester exam period -.30 Activity Design calculations Activity Assembly Lecture Safety and launch procedures -3 Team Post mortem Final assembly and working pressure test. 3-5 Activity Collect and share and prediction data within group. Finalise Write element of individual report Complete report to hand in first day back after Xmas break. 4

5 Monday Tuesday Wednesday Thursday Friday 9-0 Lecture Recap. Revised objectives. 9-0 Lecture 9-0 Lecture 9-0 Team Progress check Travel to test site 0- Teams Allocation of tasks to meet new objectives. 0- Team Discuss strategies for meeting objectives. 0- Team Agree final Activity Assembly Rocket testing -.30 Activity Initial research on stability, optimisation and altimeters Activity Design calculations for fins, nose cone and altimeter Activity Initial construction Team Share results of research Team Progress check Lecture Recap on safety and launch procedures -3 Team Post mortem e-lectures on stability, drag, optimisation and altimeters. Optimisation calculations Final assembly and working pressure test 3-5 Activity Preparation for oral presentation Establish strategy to meet objectives. Complete Write element of individual final report. Complete final report to hand in start of semester week. 5

6 APPENDIX. Materials and tools Materials (Recurrent cost) Description Bottles 300mm 34mm plastic pipe 00mm 40mm plastic pipe 00mm cable ties 5-35mm jubilee clips 34mm pipe clips mm plywood O rings x8 woodscrews Valve and valve stem / x6 woodscrews Elastic bands String PTFE tape Wood glue Altimeter components TOTAL (per group) Quantity per group 0 approx 0. m 6 4 m 0.5m x500ml shared between groups Comments Pressure vessel and launch tube end/nose cone Launch tube Release ring and launch tube end retainer To hold rocket and launch tube end To hold cable ties To hold launch tube Launch stand rocket and launch tube end Launch stand Complete inner tube For pipeclips useful during assembly remote release to seal O ring leaks launch base To obtain flight history Supplier Sainsbury s Stationery Cost for bottles (0.5, 0.33, 0.5,,.5 or litre) ~

7 Tools (Capital cost) Description Large screwdriver Medium pozidrive screwdriver Battery operated drill Drill bit set mm Tenon saw Scissors Pliers Adjustable Spanner 5w Soldering iron Electronic Scales + battery 8 bar workshop cycle pump litre plastic measuring jug Safety goggles 0 litre water container TOTAL per group Quantity per group /5 /5 /3 /3 /3 /5 5/5 /5 Comments To tighten jubilee clips To tighten woodscrews To drill holes To drill valve hole To cut wood and pipe To cut bottle To hold valve stem To tighten valve stem nut To assemble altimeter For weighing components to within gram To pressurise rocket To measure water volume Protection during pressure testing To carry water at launch site Supplier Argos Argos Sainsbury Blacks Cost / 5.99 / / / 3.99 / / / /