The University of Toledo

Transcription

1 The University of Toledo Project Cairo Preliminary Design Review 10/08/2016 University of Toledo UT Rocketry Club 2801 W Bancroft St. MS 105 Toledo, OH 43606

2 Contents 1 Summary of Preliminary Design Review Team Summary Launch Vehicle Summary Size and Mass Statement Motor Choice Recovery System Milestone Review Flysheet Payload Summary Changes Since Proposal Changes to Vehicle Criteria Changes to Payload Criteria Changes to Project Plan Vehicle Criteria Mission Statement Mission Success Criteria Preliminary and Alternative Designs Vehicle Body Recovery Propulsion Recovery Subsystem Alternative Recovery Designs Preliminary Recovery Design Recovery Analysis Mission Performance Predictions Flight Profile Simulations Stability Margin Kinetic Energy at Landing Drift Simulations Safety Overview NAR Code

3 4.2 Failure Modes and Effect Analysis Safety Checklists Rocket Assembly Checklist Construction Checklist Launch Procedures Checklist Payload Criteria Payload Objective Payload System Design Alternative Designs Preliminary Design Active Roll Control Unit (ACRU) Servo and Control System Overview Project Plan Requirement Compliance NASA Student Launch Requirements Timeline Budget Funding Plan

4 Table of Figures Figure 1: Milestone Flysheet... 7 Figure 2: Proposal Rocket Figure 3: Current Rocket Figure 4: K480W-P Motor Figure 5: K700W-P Motor Figure 6: Altimeter Figure 7: Altimeter Figure 8: Flight Profile Simulations Figure 9: K480W-P Flight Profile Figure 10: K700W-P Flight Profile Figure 11: K480W-P Altitude Figure 12: K480W-P Thrust Curve Figure 13: Stability vs. Time Figure 14: Stability, CG, and CP Figure 15: Kinetic Energy at Landing Figure 16: No Wind Drift Figure 17: 5 MPH Wind Drift Figure 18: 10 MPH Wind Drift Figure 19: 15 MPH Wind Drift Figure 20: 20 MPH Wind Drift Figure 21: Drift Table Figure 22: NAR Safety Figure 23: FMEA Table Figure 24: Rocket Assy. Checklist Figure 25: Construction Checklis Figure 26: Risk and Injury Figure 27: Launch Procedure Checklist Figure 28: Four servo layout Figure 29: Preliminary Payload Assembly Figure 30: Payload Exploded View Figure 31: Gearbox Assembly Figure 32: Control Surface Model Figure 33: Control Surface Prototype with 10mm cube for scale Figure 34: Rotation vs. Torque Figure 35: ACRU PCB Schematic Figure 36: Backup Breakout Board Schematic Figure 37: In Circuit Serial Programming (ICSP) Setup Figure 38: Control Loop Overview Figure 39: Timeline Figure 40: Budget Figure 41: Funding

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6 1 Summary of Preliminary Design Review 1.1 Team Summary Team Leader: Michael Blackwood (440) NAR # L2 Certified Safety Officer: Jay Nagy (567) Team Mentor: Art Upton (419) NAR #26255 L3 Certified NAR Section: Jackson Model Rocketry Club Section #620 Team Leadership: Michael Connor Andrew L. Peter L. Jay Patrick Marwan Will Team Lead, Payload System Lead Payload Hardware Lead Vehicle Body Lead, Treasurer Propulsion Lead Safety Officer Recovery Lead Payload Electronics Lead Education/Outreach Lead 5

7 1.2 Launch Vehicle Summary Size and Mass Statement The rocket will weigh roughly 16.6 pounds with the motor and 12 pounds without the motor. This mass accounts for the current motor selection, but may change slightly if a different motor is used on launch days due to availability. The rocket is 84.7 inches tall and 4 inches in diameter in the main body tube Motor Choice The motor choice from the proposal has not changed since the PDR. The team finds the velocity will be safe throughout travel. The vehicle will be powered by an Aerotech K480W-P. This motor will propel the rocket and its payload to an altitude of 5,638 feet in peak conditions. This simulation does not account for the rotation of the rocket. It is expected that with rotation and unaccounted extra weight from construction, that the rocket will not reach 5,638 feet. Peak velocity of the flight is 745 ft/s or 0.67 Mach. The velocity of the rocket will not be near Mach and will not reach transonic speeds. This will provide for a safe flight for the rocket. Similarly, the off the rail speed for a 6 foot rail is projected to be 62 feet per second, well above NASA requirements. As more data is collected, simulations should show the rocket being within the 300 foot window of the target Recovery System The recovery system will be able to slow the vehicle to a safe, low impact velocity to make the vehicle reusable. Velocity considerations for the recovery system will be at main parachute deployment, 139 feet per second, and on impact with the ground after launch, 22.4 feet per second. On deployment of the main parachute the velocity must not be too great for the shock cords or parachute itself and on impact the kinetic energy must not be greater than the prescribed impact energy of 75 foot pounds. The drogue parachute must be able to slow the rocket vehicle enough for main parachute separation and together the main parachute and drogue must be able to slow the vehicle to the proper impact energy requirement. The drogue parachute is to deploy at apogee and the main parachute will deploy at 700 feet above ground as determined by the onboard Stratologer altimeters. The altimeters will trigger the drogue ejection charges when apogee is detected and the main parachute ejection charges at 700 feet. The shock cords will be twice the length of the rocket to ensure proper deployment of the parachutes. A Nomex blanket will protect the parachute from fire damage during the detonation of the 2 gram ejection charges. We will have backup ejection charges that fire at 650 feet, each holding 3 grams to ensure the parachute will be deployed properly. 6

8 1.2.4 Milestone Review Flysheet Milestone Review Flysheet Institution The University of Toledo Milestone Preliminary Design Review Vehicle Properties Motor Properties Total Length (in) Motor Designation AeroTech K480W-P Diameter (in) 4 Max/Average Thrust (lb) / Gross Lift Off Weigh (lb) 16.6 Total Impulse (lbf-s) Airframe Material Fiberglass Mass Before/After Burn 4.58/1.73 Fin Material Fiberglass Liftoff Thrust (lb) Coupler Length 9" Motor Retention RMS 54/2560 Stability Analysis Ascent Analysis Center of Pressure (in from nose) in Maximum Veloxity (ft/s) 745 Center of Gravity (in from nose) in Maximum Mach Number 0.67 Static Stability Margin 1.86 Maximum Acceleration (ft/s^2) Static Stability Margin (off launch rail) 1.86 Target Apogee (From Simulations) 5615 Thrust-to-Weight Ratio 12.4 Stable Velocity (ft/s) 65 Rail Size and Length (in) 72 Distance to Stable Velocity (ft) 6.4 Rail Exit Velocity 65.6 Velocity at Deployment (ft/s) Velocity at Deployment (ft/s) 139 Recovery Harness Material Nylon Recovery Harness Material Nylon Shock Cord Harness Size/Thickness (in) 1/8 in x 1/2 in Harness Size/Thickness (in) 1/8"x1/2" Recovery Harness Length (ft) 10 ft Recovery Harness Length (ft) 10 Harness/Airframe Interfaces Kinetic Energy of Each Section (Ftlbs) Recovery System Properties Dogue Parachute Size 12" Size 72" Altitude at Deployment (ft) 5638 Altitude at Deployment (ft) 700 Terminal Velocity (ft/s) 139 Terminal Velocity (ft/s) 22.4 Eyebolt attached to top of Payload Bay and to the bottom of the recovery bay. Harness/Airframe Interfaces Recovery System Properties Main Parachute Manufacturer/Model LOC Precision Manufacturer/Model LOC Precision Eye bolt attached to top of recovery bay and bulkhead of in the nosecone. Kinetic Section 1 Section 2 Section 3 Section 4 Energy of Section 1 Section 2 Section 3 Section 4 Each N/A N/A Section (Ftlbs) N/A Altimeter(s)/Timer(s) (Make/Model) Redundancy Plan Pad Stay Time (Launch Configuration) Recovery Electonics StrattologgerCF Second StratologgerCF and backup blackpowder charges Up to 8 hours Rocket Locators (Make/Model) Transmitting Frequencies Black Powder Mass Drogue Chute (grams) Black Powder Mass Main Chute (grams) Recovery Electonics TeleGPS MHz 2 g 2 g Figure 1: Milestone Flysheet 7

9 1.3 Payload Summary This year s payload will be Roll Induction and Counter Roll as described in the USLI handbook. This payload will record the natural roll state of the rocket after motor burnout and then proceed to initiate a minimum of two full rotations of the rocket. The induced rotation must then be removed from the rocket so that it returns to its natural roll state before reaching apogee. Sufficient evidence must be provided to verify that the full two rotations were complete. The team intends to accomplish this goal by using small control surfaces acting ahead of the fins to generate a rolling moment. 8

10 2 Changes Since Proposal 2.1 Changes to Vehicle Criteria The originally proposed vehicle body design used a 5 inch diameter rocket to accommodate the four servo design. This has since been reduced to a 4 inch diameter rocket due to the change to a single servo payload. Decreasing the diameter was done to reduce the weight of the rocket and to decrease the cost. 2.2 Changes to Payload Criteria The payload described in the Project Cairo Proposal used a four servo design. The preliminary payload design now uses a single servo utilizing a differential gearbox. The control surfaces have changed from fiberglass to a high strength 3D printed ABS plastic. The electronics package for the payload have undergone several modifications including the removal of the altimeter unit, full USB compatibility, and current sensing devices to monitor the load. General layout of the payload bay has changed slightly to accommodate the aforementioned changes. 2.3 Changes to Project Plan No changes have been made to the project plan since the proposal. The team is continuing to organize with local professors to make use of various testing facilities including a wind tunnel. 9

11 3 Vehicle Criteria 3.1 Mission Statement UT Rocketry s goal is to successfully and safely launch and land a high-powered rocket that is capable of rolling the rocket along with conducting a counter roll along the vertical axis of the rocket through the use of control surfaces. The club will also work to share an interest in space to local students, and accomplish all of these goals while ensuring the safety of team members, students and spectators. 3.2 Mission Success Criteria The requirements to deem the mission a success include following all NASA ULSI requirements which include but are not limited to: The vehicle will deliver a payload to 5280 feet above ground level, it will not exceed 5600 feet Two commercially bought altimeters will accompany the rocket The launch vehicle will be recoverable and reusable with a max of 4 independent sections The launch vehicle will use only a single stage The launch vehicle will utilize a dual deploy system An electronic deployment form must be utilized Team members will complete 100% of the project The team's mission success criteria includes meeting all listed NASA requirements. Assuming all NASA constraints are met, the team will consider the mission a success if the following criteria are met: The rocket achieves a height within 300 feet of the targeted 5280 feet The rocket lands safely and is reusable after reloading a motor and resetting the recovery system. The rocket successfully controls the natural spin, conducts a rotation, and then counteracts the rotation. Assuming the requirements from NASA are met and the mission success criteria are all met in totality, the mission will be declared successful. 10

12 3.3 Preliminary and Alternative Designs Vehicle Body The vehicle body was originally a 5 inch body made out of fiberglass with large fiberglass fins on the bottom of the rocket body, smaller fins near the center of mass, and a 5:1 ogive nose design. That can be seen below: Figure 2: Proposal Rocket We moved away from the 5 inch body design after the payload team decided against a 4 servo design. This allowed us to slim up the body as a whole and move towards a 4 inch diameter rocket body. We are still using fiberglass as our main body material because of its low weight and cheaper price. We have drastically shrank the size of the rear fins bringing the total surface area of the fins from 81 inches squared to inches squared. This greatly reduces material weight and cost while still allowing us for a safe margin of stability in flight. Our nose cone also changed from the 5:1 ogive shape to a 4:1 ogive shape. The 5:1, because it is larger, adds more mass to the rocket thus reducing the overall achievable altitude. Because we are not going transonic we do not need the added aerodynamic effects that the 5:1 offers, allowing us to more to the 4:1 shape to save on weight. The new model of the rocket is shown below. As you can see it has gained a much sleeker look while remaining as utilitarian as possible. Figure 3: Current Rocket 11

13 3.3.2 Recovery The recovery of the rocket currently consists of an initial drogue parachute which will deploy at apogee. This is to initially slow the rocket to prepare for the deployment of the main parachute and to reduce the time till landing along with the drift distance. This drogue parachute will deploy from the Lower Rocket Body. After the deployment of the drogue parachute, the main parachute will deploy at 700 feet. This is the main recovery method and will return the rocket safely to the ground. Other options that were considered were streamers instead of a drogue parachute, multiple parachutes used in conjunction, and a larger main parachute. While each of these options would lead to a safe recovery of the rocket, they have drawbacks including added mass, added cost, and added complexity that reduce their feasibility. A streamer would be used in conjunction with the main parachute to assist in the initial slowing of the rocket. The streamer would replace the usage of a drogue chute and would provide similar results. Some of the benefits to using a streamer would be easier deployment as entanglement and non-deployment would be less of an issue due to the way in which the streamer would be packed. It would also help increase the initial visibility of the rocket at higher altitudes if a reflective material would be used. One notable drawback to using a streamer would be less drag to initially slow the rocket. This would lead to a higher main parachute deployment velocity and more force being exerted on the rocket at the time of deployment. Multiple parachute configurations, such as using two parachutes in conjunction, would allow for a greater decrease in velocity and would help decrease the force exerted on the rocket during descent. This multiple parachute configuration would be used as a replacement to the main parachute or, if smaller parachutes were used, as a replacement for the drogue chute. Some benefits to using the multiple parachute configuration would be a slower descent rate, leading to a safer landing velocity. It would also incorporate a type of redundancy which would help recover the rocket in case one parachute failed to open upon deployment. Some drawbacks to using a multiple parachute configuration would be the increased weight and space required within the rocket to launch a rocket with two parachutes. This would be detrimental to the overall rocket design as the housing volume for the two parachutes is at a premium. It would also require a stronger eyebolt and mounting design to account for the increase in tension with the two parachutes. In addition, multiple chutes are more likely to get tangled during deployment and could result in a total recovery failure if deployed incorrectly. Considering that the payload will rotate the rocket, the increased danger of entanglement is a major detraction from this method. A larger parachute could be used in place of the selected parachute to further reduce the descent speed and reduce the energy at impact. This would lead to less of an environmental impact and further reduce the risk of damage to the rocket body. However, a larger main parachute would increase the drift of the rocket during landing, and could potentially cause the rocket to drift out of the designated landing area. Larger parachutes also cost more, and require more space within the rocket body. This would lead to a larger rocket overall, and 12

14 drive the need for a larger motor to compensate for the increased mass. Further considerations must also be made with respect to the choice of drogue parachute if a large main chute is selected. A larger chute will experience greater acceleration during deployment than a smaller one, thus a larger drogue parachute would also be required in this method. By maintaining the current parachute size, the rocket will land safely with minimal environmental impact, and will allow the team to maintain the current design and budget. The system chosen to provide a safe recovery of the rocket is a drogue chute deployed at apogee and a main parachute deployed at an altitude of 700 feet for a few key reasons. The first key reason is the team's familiarity with the system. The system chosen is similar to the system used last year. This familiarity ensures better preparation and system readiness earlier in the design of the rocket. Another key reason is because of the reliability of the methods. The usage of a main parachute and a deployment of a drogue chute was successfully proven last year and it would seem to be a wise choice to continue the system this year. Finally, the methods for setting up and securing the system are already known and can be improved on during the design phases to help eliminate any problems that may have arisen in the past Propulsion The Aerotech Motor is a NAR certified high power rocket motor. It is expected to function at predetermined levels of thrust, impulse and duration as specified by the manufacturer. The motor is expected to ignite when the ignition signal is sent. The motor should burn for the predetermined amount of time and experience zero anomalies during launch and flight. The launch simulation shows the rocket overshooting the target. The rotation caused by the payload experiment, weight changes due to additional components, and differing wind speeds are anticipated to lower the actual apogee. The AeroTech K480W-P is currently our choice for rocket motor. It will keep our speed out of the transonic range while allowing us to get to the 5280 feet height when extra weight is added and energy robbed by the rotation of the rocket. The AeroTech K700W-P is a second choice that we are considering due to a possible lack of availability of the K480W-P motor. It puts us in a similar range height-wise, but gets us to a slightly higher max velocity, putting the fins in extra danger of ripping off compared to the K480W-P. 13

15 Figure 4: K480W-P Motor Figure 5: K700W-P Motor 14

16 3.4 Recovery Subsystem Alternative Recovery Designs The leading alternative designs mostly focus on the choice of alternative parachute deployments. The electronics subsystem is based on a tried and tested design complete with redundancy. For this reason alternative altimeter bay designs were not considered. Nylon shear pins must be used so that the rocket sections may separate cleanly and given their simplicity no other designs were considered. Alternative drogue systems include streamers and larger or smaller diameter parachutes. Streamers inherently produce significantly less drag than normal parachutes. A streamer deployed at apogee will therefore, not be able to control the descent speed as well as a normal drogue parachute. A sufficiently long or wide streamer could produce enough drag to create a safe decent speed but a streamer of this size is more likely to knot or tangle on deployment. However, the streamer would decrease the weight of the rocket significantly and, due to the increased descent velocity, would decrease the drift of the rocket. This would provide immense benefit on windy days. Unfortunately, the higher decent velocity also means that the main parachute and its attached shock cord would experience significantly more force on deployment. Due to the weight of the rocket a parachute was chosen for the drogue deployment. The size of the drogue parachute is inherently limited by the amount of drift that the rocket can experience. An especially large parachute would mean that the rocket would drift further during descent as the descent time will increase. Therefore the size limits of the drogue parachute are determined by the speed of descent on the lower end and the drift distance on the upper. The maximum drift with the current configuration was found to be near 2000 feet on an especially windy day, this distance is well within the defined flight area. A larger drogue chute is thus a valid option and could reduce the force experienced by the main parachute. However, this option would increase the weight of the rocket which would require a larger motor and could impact the response speed of the payload. Thus the current choice of a 12 inch drogue parachute is still the preferred option. However, further analysis of the main chute deployment is necessary to validate the shock cords will be able to handle the forces caused by the rapid descent. Furthermore, a 20 in. drogue chute is available from last year's rocket and so if a switch is required it is easier to obtain the larger parachute than a smaller one. The main deployment must be a parachute to reduce the rocket velocity to a sufficiently low speed. This safe impact velocity determines the lower bound of the parachutes diameter. Thus the only option is to increase the size of the diameter. The current main parachute at 72 inches is only slightly larger than the minimum required safety diameter and thus has less room for changes to the rocket. A larger parachute would increase the mass of the rocket 15

17 but would also be able to handle the increased weight during descent better. But increasing the size of the main parachute will also increase the forces experienced by the shock cord at the time of deployment. This increased force means a larger drogue is also required in order to prevent damage from occurring to the main parachute. The current parachute is able to handle the current forces and provide a safe descent velocity while using less weight and space making it the better option with the current design Preliminary Recovery Design The current recovery design will consist of two stages: a drogue parachute deployed at apogee and a main parachute deployed at 700ft. This recovery design will provide a safe method of recovery as it will involve a main method of slowing the descent of the rocket along with providing a means of slowing the rocket before the main parachute will deploy to lessen the initial shock exerted on the rocket. The choice of a drogue parachute of over the other previously mentioned alternatives (such as a streamer, or larger parachute) seems logical and will help provide a reliable means of slowing the rocket. This decision came about after analyzing the criteria which the rocket will be descending under. The large mass of the rocket will require a larger drag force to both slow and stop, leading the team to a design that will provide a larger drag. Deploying the drogue parachute at apogee will generate sufficient drag force to properly slow the rocket's descent. The usage of a streamer could be acceptable but, the number of streamers needed to match or exceed the drag force of a drogue parachute would be impractical due to size or weight limitations. For the main recovery, the choice of parachute is logical and efficient for the size and setup of the rocket. The type of main recovery which could have been used did not cover a large extent because, as mentioned above, the amount of drag that will be needed to slow a rocket of this size will require a parachute. The designs which were narrowed down involved the usage of a dual parachute system versus a single parachute system. The choice to go with a single parachute system came about because of practicality and simplicity of the system. It was impractical to have two parachutes within the recovery bay due to size constraint and would have provided a greater chance that the chute lines would have become entangled, causing one or both of the parachutes to fail to deploy, especially considering the payload of choice. The recovery system is a dual-deployment system with redundant ejection charges. Both the drogue and main sides of the recovery system will have two ejection charges. These ejection charges will be linked to two separate altimeters. Using two altimeters ensures a safe recovery of the rocket. If one altimeter were to fail, the other altimeter is still able to deploy the drogue and main parachutes, allowing the rocket to descend as expected. The main altimeter will be set to the determined time and altitude delays. The backup altimeter will be slightly delayed from these presets. Delaying the backup altimeter s settings prevents the parachute bays from being over pressurized and maintains the structural integrity of the rocket. Nomex blankets will be used to protect the parachutes from any damage during the detonation of the blast caps. 16

18 A welded eyebolt will be used to connect the shock cord to the rocket's bulkheads to ensure that the shock cord is securely fashioned. Figures 6 and 7 below show the electronic design of the recovery system. Two separate 9 volt batteries are used to supply power to the two StratoLoggerCf altimeters. Each launch will require the use of new batteries to ensure sufficient power to operate throughout the launch. A TELEGPS unit is mounted in the nose cone of the rocket and can be used to recover the rocket if it goes out of line of sight during descent. This unit can transmit its location in the HAM band and can be received by a nearby ground station to determine the rocket's location. The unit is also capable of transmitting its current altitude and velocity information to the ground station so that it can be monitored during the flight. Figure 6: Altimeter 1 Figure 7: Altimeter Recovery Analysis The primary concern of the recovery system is the kinetic energy of the rocket components when impact occurs. The most massive component will be the one with the largest kinetic energy at impact and, therefore, it can be used to determine a maximum safe falling velocity. This velocity is then used with equation 1 to find the minimum main parachute diameter where C D is the drag coefficient, ρ is the density of air, m is the total rocket mass, and v is the velocity. 17

19 D = 8mg πρc D v 2 Equation 1 In performing this calculation a drag coefficient of.8 was used, typical values of the drag coefficient of a parachute are in the range, however.8 was chosen to produce conservative estimates. In addition, the weight of the depleted K480W-P motor was added to the base weight of the aft section to produce a more accurate value for the weight of the section at impact. The kinetic energy is calculated using equation 2 below. The mass of the aft section including the depleted motor is 8.775lbm, thus the maximum descent velocity is 23.46ft/s. Therefore, the diameter of the parachute shall be determined with a maximum descent velocity of 23ft/s. KE[lbf ft] = 1 2 m[lbm] (v [ft 2 s ]) Equation 2 [lbf] 32.2[ ft s 2] Assuming air density taken at sea level with dry air (.0765lbm/ft^3) the minimum diameter of the main parachute is determined to be 5.9ft or 71in. This number is very close to the actual size of the parachute. However, a less conservative C D of 1.4 would produce a minimum diameter of 54in. The actual velocity of the rocket when using a 72 inch parachute would be 22.6ft/s. The diameter of the drogue parachute is less important in safety calculations. The drogue's main purpose is to slow the descent so the main parachute can safely be deployed while reducing the drift of the rocket due to wind. The size of the drogue parachute was determined primarily by its performance in OpenRocket simulations. 18

20 3.5 Mission Performance Predictions Flight Profile Simulations Component Component Weight Motor 72.6 oz Payload 8.96 oz Recovery Main Parachute 8.96 oz Drogue Parachute 1.2 oz Electronics 17.6 oz Body Nose Cose 7.11 oz Fins Canard Fins 5.08 oz Aft Fins 40.1 oz Body Tubes 76.5 oz Figure 8: Flight Profile Simulations The team is currently choosing between two motors, one being the K480W-P and the K700W-P. Both motors allows us to reach well over the target altitude. As shown in the graph below, the K480W-P gets us to 5530 feet while the K700W-P gets us to 5640 feet so they allow us to reach roughly feet about the target altitude. This was expected to be above the target altitude due to the fact that the mass margins for our components specifically the payload are only approximate as this point in time. The altitude is expected to decrease as design changes that add mass occur in the future. While both motors and their respective altitude simulations have been shown, the K480W-P is the teams primary motor choice due to the fact that the extra 100 feet above the target altitude compared to the K700W-P allows us more room for design changes, unplanned weight, or other unknowns. In the event a components weight is not what is was expected to be, we have a larger margin of error in altitude to play with. In regards to the Flight Profile Simulation Chart shown below, the rapid increase in acceleration due to the main chute ejecting is a cause for concern. Through the simulation it Is shown that the rocket will experience and acceleration of 665m/s^2. This is a big safety concern because it could break the rip cord holding the rocket connected to the parachute, resulting in a potential disastrous situation of losing our main parachute. The rocket also is projected to reach a max velocity of 0.67 Mach, which means the rocket will be close to entering the transonic regime. Thus it will not have to deal with problems like stress added to components such as the fins in that range of airflow speeds. 19

21 Figure 9: K480W-P Flight Profile Figure 10: K700W-P Flight Profile 20

22 Figure 11: K480W-P Altitude Figure 12: K480W-P Thrust Curve 21

23 3.5.2 Stability Margin Figure 13: Stability vs. Time Above is a graph of the stability margin over time. It displays the stability margin specifically during motor cut-out and when the rocket flip at apogee begins. The rocket becomes stable at t=.21s with a stability of >1 caliber. At this point it is traveling at 65 ft/sec and is at an altitude of 6.4 ft, still attached to the launch rod. At t=.61s the rocket reaches average stability during powered flight of 1.86 caliber. After the motor cuts out the stability margin maxes out at 2.62 caliber with an average of 2.55 caliber between motor cutout and flip. The stability margin could further be increased through design modifications to the fins and an addition of ballast in the nose of the rocket. Stability Margin Center of Gravity Center of Pressure (From Nose) 1.86 Caliber Inches Inches Figure 14: Stability, CG, and CP Kinetic Energy at Landing The launch vehicle will have all sections tethered together with no independently moving sections. As such, we may treat the kinetic energy of the three main body sections separately. Using equation XX once again, the kinetic energy for each section can be calculated. The simulated impact velocity was 22.38ft/s as compared to the calculated impact velocity of 22.6ft/s. Property Nose Cone Forward Body Aft Body Mass (lbm) Kinetic Energy Simulation (ft-lbf) Kinetic Energy Calculated (ft-lbf) Figure 15: Kinetic Energy at Landing Note that both the simulation and hand calculation produce less than 75 foot pounds of energy for each section satisfying the mission requirements. 22

24 3.5.4 Drift Simulations Drift calculations for the rocket have been completed using OpenRocket simulations given the current design for the rocket as described. All simulations have been modeled under the assumption of an 8 foot tall rail, a perfectly vertical launch, and with a standard deviation of 0 for the wind speed within each simulation. Figure 16: No Wind Drift For a zero wind option the expected lateral drift for the rocket reached approximately 16 ft from the base of the launch pad. Figure 17: 5 MPH Wind Drift Considering a wind speed of 5 mph, the drift is drastically increased up to approximately 360 feet from the base of the launch pad. 23

25 Figure 18: 10 MPH Wind Drift Considering a wind speed of 10 mph, the drift is again dramatically increased up to now approximately 760 feet from the base of the launch pad. This is greater than double the drift from doubling the wind speed and begins to show a trend of an exponentially increasing drift distance with an increase in wind speed conditions. Figure 19: 15 MPH Wind Drift At 15 mph wind speed, this simulation shows a continued trend toward a rapid increase in drift distance at approximate 1100 feet. 24

26 Figure 20: 20 MPH Wind Drift At 20 mph, this drift simulation shows the upper limit of the proposed recovery system s drift to be approximately 1600 feet from the base of the launch pad. The actuality of the drift will be dependent on the angle of launch and direction of the wind. If launched at an angle into the wind, drift will be less than these simulations describe. If; however, launched with the wind at an angle the drift may be greater than the above simulations describe. Wind Speed (mph) Drift Distance (ft.) Figure 21: Drift Table 25

27 4 Safety 4.1 Overview Within this section is the entirety of the NAR code, along with explanations of how the team intends to follow each tenant of the NAR code. The team has used this as a baseline to better ensure that potential setbacks are mitigated. By understanding and operating with the NAR code in mind, the team will be able to complete the project and successfully launch without injuries, damage to the environment, or other safety-related problems NAR Code 1. Certification "I will only fly high power rockets or possess high power rocket motors that are within the scope of my user certification and required licensing." 2. Materials "I will use only lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction of my rocket." 3. Motors "I will use only certified, commercially made rocket motors, and will not tamper with these motors or use them for any purposes except those recommended by the manufacturer. I will not allow smoking, open flames, nor heat sources within 25 feet of these motors." 4. Ignition System "I will launch my rockets with an electrical launch system, and with electrical motor igniters that are installed in the motor only after my rocket is at the launch pad or in a designated prepping area. My launch system will have a safety interlock that is in series with the launch switch that is not installed until my rocket is ready for launch, and will use a launch switch that returns to the off position when released. The function of onboard energetics and firing circuits will be inhibited except when my rocket is in the launching position." 5. Misfires "If my rocket does not launch when I press the button of my electrical launch system, I will remove the launcher s safety interlock or disconnect its battery, and will wait 60 seconds after the last launch attempt before allowing anyone to approach the rocket." 6. Launch Safety "I will use a 5-second countdown before launch. I will ensure that a means is available to warn participants and spectators in the event of a problem. I will ensure that no person is closer to the launch pad than allowed by the accompanying Minimum Distance Table. When arming onboard energetics and firing circuits I will ensure that no person is at the pad except safety personnel and those required for arming and disarming operations. I will check the stability of my rocket before flight and will not fly it if it cannot be determined to be stable. When conducting a simultaneous launch of more than one high power rocket I will observe the additional requirements of NFPA 1127." 7. Launcher "I will launch my rocket from a stable device that provides rigid guidance until the rocket has attained a speed that ensures a stable flight, and that is pointed to within 20 degrees of vertical. If the wind speed exceeds 5 miles per hour I will use a launcher length that permits the rocket to attain a safe velocity before separation from the launcher. I will use a blast deflector to prevent the motor s exhaust from hitting the ground. I will ensure that dry grass is cleared around each launch pad in accordance with the accompanying Minimum Distance table, and will increase this distance by a factor of 1.5 and clear that 26

28 area of all combustible material if the rocket motor being launched uses titanium sponge in the propellant." 8. Size "My rocket will not contain any combination of motors that total more than 40,960 N-sec (9208 pound-seconds) of total impulse. My rocket will not weigh more at liftoff than one-third of the certified average thrust of the high power rocket motor(s) intended to be ignited at launch." 9. Flight Safety "I will not launch my rocket at targets, into clouds, near airplanes, nor on trajectories that take it directly over the heads of spectators or beyond the boundaries of the launch site, and will not put any flammable or explosive payload in my rocket. I will not launch my rockets if wind speeds exceed 20 miles per hour. I will comply with Federal Aviation Administration airspace regulations when flying, and will ensure that my rocket will not exceed any applicable altitude limit in effect at that launch site." 10. Launch Site "I will launch my rocket outdoors, in an open area where trees, power lines, occupied buildings, and persons not involved in the launch do not present a hazard, and that is at least as large on its smallest dimension as one-half of the maximum altitude to which rockets are allowed to be flown at that site or 1500 feet, whichever is greater, or 1000 feet for rockets with a combined total impulse of less than 160 N-sec, a total liftoff weight of less than 1500 grams, 11. Launcher Location 12. Recovery System and a maximum expected altitude of less than 610 meters (2000 feet)." "My launcher will be 1500 feet from any occupied building or from any public highway on which traffic flow exceeds 10 vehicles per hour, not including traffic flow related to the launch. It will also be no closer than the appropriate Minimum Personnel Distance from the accompanying table from any boundary of the launch site." "I will use a recovery system such as a parachute in my rocket so that all parts of my rocket return safely and undamaged and can be flown again, and I will use only flame-resistant or fireproof recovery system wadding in my rocket." 13. Recovery Safety "I will not attempt to recover my rocket from power lines, tall trees, or other dangerous places, fly it under conditions where it is likely to recover in spectator areas or outside the launch site, nor attempt to catch it as it approaches the ground." Figure 22: NAR Safety Certification The club will only allow those with an adequate level of certification or license. Michael Blackwood has an L2 HPR license and will be present for all launches. We will be using a J, K or L motor or lower which Michael has the training and certification for. The clubs mentor, Art Upton, has and L3 launches and will be there for every launch we do as well Materials The club will be using a fiberglass body tube. This Follows the NAR`s guidelines because they classify fiberglass as an excepted lightweight material. The build team will be using few ductile metals such as eyebolts, and various metal objects that will be used for the roll counter roll experiment, and motor containment parts. These are needed for the rockets experiment and functionality. 27

29 Motors The club plans to use an Aerotech motor. This maker is a certified and a commercial company. The motor will be purchased on the launch site then will be inspected for tampering after purchase. Then inserted into the rocket. The club ran simulations to ensure that the motor is being used for the purposes recommended by the manufacturer. The safety team will ensure that there is no smoking, open flame, or heat sources within 25 feet of the motor Ignition System Misfires The club does not have an electrical launch system, so we will use ones provided at launch sites. The safety team will ensure that the igniter will be installed after the rocket is on the launch pad or at the prepping area if allowed by the launch site owners. The club will refuse to launch on any sight that provides us with an electrical launch system that does not have a safety interlock that returns to the off position after the rocket. The safety team will ensure that the safety interlock remains in the off position until the rocket in launching position. In the event of a misfire the safety team will ensure that the safety interlock is in the off position. Then we will ensure that all spectators, launch site workers, and club members wait at least 60 seconds to approach the rocket Launch Safety The club will alert the spectators with an air horn if there is no public addressing system available at the launch sight. We will then alert the spectators with a countdown from five. The motor to be used has a total impulse of Ns, thus it is required that the minimum clear distance is 75 feet, and the minimum personnel distance must be 200 feet and no complex should be within 300 feet. When arming the onboard recovery systems, the safety team will ensure that every unnecessary personnel is away from the prepping area and disarming area. The club will refuse to launch simultaneously with another high-powered rocket Launcher The club does not have access to a launch rail system so the club will ensure that a launch rail system can be provided at the launch site. With a launch rail length of six feet, the rocket will leave at 60 feet per second which is deemed stable. In the event of winds higher that five miles per hour the rocket will still meet stability requirements when leaving the six foot launch rail system. The club will not launch if the launch system or weather conditions force us to use a launch angle greater than twenty degrees from vertical. The launch rail system that is provided must have a blast deflector to prevent the motors exhaust from hitting the ground. The club will not use a motor that uses titanium sponge in the propellant during the USLI launch in Huntsville Alabama. 28

30 Size The club will be using a Aerotech K480W-P, which has an impulse of Ns. This falls below the maximum impulse of 40,960 N-sec (9208 pound-sec). The rocket will weigh 17.7 pounds. The average thrust of the motor is 545.3N, one third of that is which is greater than the weight of the rocket at lift of 17.7 lb Flight Safety Prior to lift off the safety team will inspect the rocket's expected path for clouds and airplanes. The club will ensure that the rocket`s trajectory is not going be above the spectators at any time nor leaving the boundaries of the launch site by running simulations with various weather conditions. The results of these simulations will be used to determine the best launch rail angle, and determine whether or not launches should be delayed pending inclement weather conditions. The rocket will use a dualdeployment system, and will have controlled ejection charges with the proper amount of black powder. The safety team will ensure no other flammable or explosives are in the rocket. The safety team will measure the wind prior to launch. If the wind is greater than twenty miles per hour the rocket will not be launched. The motor the club is using has a total impulse less than 40,960N-s so the rocket is classified as a class two rocket. The team mentor is L3 certified, and the team lead is L2 certified, so these two members will be responsible for purchasing, storing, and preparing the motor at all launches Launch Site The target altitude for the rocket is 5,280 feet. A 2640-foot radius that is clear of trees, power lines, occupied buildings, and persons to launch is required Launcher Location The club will launch at a rocket launch event. The club will research the event to ensure that the event has the appropriate location. The launching location must be 1500 feet away from any building or public highway. The location must be 200 feet away from the boundaries of the launching sight. Test launches will be conducted at sites utilized by local NAR clubs with current and valid FAA waivers Recovery System The rocket will have a dual-deployment ejection system. A drogue parachute will be ejected at apogee to quickly descend to 700 feet where the main parachute will eject, then the rockets velocity will decelerate to a safe landing velocity. The recovery harnesses will be comprised of rip stop nylon shock cords along with Nomex blankets to protect the parachutes from the black powder charge. Black powder ignites at roughly 350 F and Nylon has a melting temperature of 509 F. 29

31 Recovery Safety The club will measure the wind and predict the path that the rocket will fly. If the rocket`s path exceeds the boundaries of the launch site or will be above the spectators at any time the team will wait for weather conditions to change, adjust the launch angle, or not launch. If the rocket lands in a power line, tall trees, or any other dangerous spot the club will not recover the rocket. The safety team will ensure that no person attempts to catch the rocket. 4.2 Failure Modes and Effect Analysis The FMEA chart stands as one of the most important pieces of the entire preliminary design review. By addressing all known possible modes of failure and analyzing the severity, likelihood, and effect, proper mitigation strategies can be implemented to prevent any setbacks. It also displays to the team what possible failure mode is most severe and most probable so that time and energy can be focused on fixing the more major potential failures. Probability is ranked on a scale of 1-5. A ranking of 1 is an extremely improbable event that most likely would be a result of extreme negligence to procedure or failure of a manufacturer s product. A 2 ranking is a remote possibility. A 3 ranking is an occasional event. A 4 ranking is reasonably probable and at this point should be expected and planned for. A rating of 5 is frequent and should be dealt with promptly with plans created to mitigate or stop said failure. The severity rankings are also on a scale of 1-5. A ranking of 1 would be a negligible concern and would most likely go unnoticed. A ranking of 2 is a marginal failure, which an impact would be felt, it would be easy to handle. A ranking of 3 is a normal failure, at this point safety of people is a concern and effects would be time consuming or unfixable without prior preparation. A ranking of 4 is a critical failure, there is a higher risk of safety to the team and bystanders and most likely a fix could not be implemented once the failure begins. A ranking of 5 is a catastrophic failure, the rocket and payload will be lost and there is a high probability of injury. When comparing these two parameters on a matrix, probability and severity respectively, it is critical to address rankings of 5-5, 5-4, 5-3, 4-5, 4-4, 4-3, 3-5, and 3-4. These are competition ending failures. Any failure mode with one of the previously mentioned rankings will immediately be looked at by the entire team in order to come up with a plan to reduce the severity of probability. The FMEA matrix below outlines the team s possible failures on the scale described above. 30

32 Severity Probability Failure Cause Mission Success Effect Personnel Safety Effect Environmental Effect Mitigation Drogue parachute doesn t deploy at apogee Main parachute does not deploy at 500 feet. Motor CATO Sheering Fins Shock cord failure Old batteries, incorrect wiring or too small ejection charges Black powder charge is too small, bad wiring, old batteries, the more friction from bigger parachute prevents rocket body tube form separating. Motor had a defect or was tampered. Aerodynamic forces exceeding the strength of the fin s mounting mechanism or the fin s strength itself. Overused/ defective shock chord or failure to secure properly 1 5 Rocket falls at too high of a velocity, unable to deploy main and land. 2 3 Rocket falls a higher velocity than intended, may cause damage to electronics and body upon landing. 1 5 Rocket will have catastrophic event and lose control or destruct. 3 5 Rocket control will be lost and could go ballistic or spin to the point of tangling parachutes. 2 4 Rocket will remain on a ballistic trajectory causing loss of the rocket and payload Personnel or spectators under rocket could be injured during high speed landing Personnel or spectators under rocket could be injured during high speed landing Spectators near CATO may be injured by shrapnel or high speed rocket. Personnel or spectators near the launch area could be injured by falling debris or the rocket itself Ballistic rocket could potentially impact a populated area Ground damage at landing place Ground damage at landing place. Ground fire or shrapnel left on the ground. Ground damage at landing place and debris spread over flight path. Ground debris. Use new batteries for each launch. Ground testing of ejection system before all launches. Review wiring Use new batteries for each launch, test ejection system before flight. Use baby powder or other lubrications to ensure ejection. Rocket motors will be bought by trusted motor maker. Motor will be inspected for tampering. Fins will be designed to withstand more force than will be experienced in flight. Tests will be performed before launch. Testing of shock cord load limits and proper attachment 31

33 Onboard fire Construction failure Fire at launch location post lift off. Impact with flying object Electrical shorts or catastrophic battery failure. The rocket is poorly constructed and shatters at max aerodynamic load with no specific failure point identifiable. Exhaust from the launching rocket ignites the area around the launch pad. The rocket collides with another object 2 5 Total loss of rocket expected. Significant internal damage and potential loss of recovery systems. 2 5 Very little data would be obtainable. Mission would be considered a total loss 1 3 The rocket would presumably carry on with the mission unaffected 1 4 The rocket would most likely be able to continue of the launch site. Personnel or spectators near the launch area could be injured by falling debris or the rocket itself. Fire could spread on dry material if not put out during descent putting nearby homes and farmland at risk. Safety personnel may have to approach to contain the fire. Dry landing locations may catch fire and spread rapidly. Loss of recovery systems could result in debris scattering across flightpath and further damage at impact site. procedures. Specifically attached with a welded eye bolt or U-bolt. Ensure proper electrical connections and designs are made. Test extensively before flying. Charge batteries using proper equipment to prevent degradation. Falling debris Ground debris Ensure proper rocket construction techniques are followed using premade instruction manuals and club trained builders. The cleared pad would mean no ground personnel are affected. Safety crew would have to suffocate the fire. Possible rocket flying off course or exploding Launch site would be burned up, potentially a large area if not brought under control Ground Debris Inspect launch pad, check for any dried plant matter or other potentially flammable material and remove it from the area. In the very unlikely event the rocket 32

34 Shear Pins do not shear mid flight Too many shear pins are used or not enough force is applied to break the pins climbing in altitude without explosion but would be dangerously off course 1 4 The rocket would be unable to deploy the recovery system properly and would crash land resulting in loss of mission. Possible falling debris Ground debris impacts a bird, or another rocket, it is no longer under the teams control. The range coordinator would not allow a launch with other objects in flight. Use recommend number of shear pins for rocket body, test forces in a controlled environment. Motor Ignition Failure Loss of safety officer or integral team member on day of launch The motor fails to ignite, either from a faulty motor or igniter. Travel sickness or change in environment. Food poisoning. 2 4 The rocket would be removed from the pad and potentially never fly resulting in mission loss 3 2 Resources would have to be diverted but no single individual is crucial to the success of the launch. Team may accidentally approach an armed rocket An individual with less training may oversee critical safety steps that could limit the team's ability to follow safety protocol. No effect. No effect. Follow proper igniter insertion procedures and should a failure occur, do not panic, follow NAR procedures to approach the failed motor and inspect. Ensure other team members can quickly and competently cover for any other individual (proper documentatio n and training). 33

35 Allergic reaction to epoxy Debris entering eyes during construction Parachute packed improperly Wind alters rocket s flight path Unknown allergies and/or mishandling of epoxy material. Lack of proper eye protection when constructing rocket. Rushing to complete setup, failing to adhere to proper assembly techniques. Unpredictable weather patterns. 2 4 Could result in team member being unable to attend launch. 3 3 Likely to occur well in advance of mission and so should have limited influence on the launch. 3 5 Parachute may fail to deploy making recovery of intact rocket unlikely. 2 3 Fin control may be minimized by high angle of attack. Larger horizontal velocity will reduce the rocket's ability to reach the altitude target. Severe allergic reactions can be lethal to those experiencing them. Other personnel are not likely to be affected. Individual may require immediate medical attention depending on severity. Bystanders near the launch area could be injured by the highspeed landing. Rocket could be carried outside the designated area landing on unwitting onlookers. No effect. No effect. Damage to area around impact. Rocket could end up in environmentall y sensitive area such as a nearby stream. Procure medical supplies in case of any ailments. Begin instructing a redundant safety officer. Follow proper material handling protocols to avoid any safety risks. Follow proper material handling protocols and wear protective eyewear when performing work that could produce debris. Follow launch day procedures carefully. Double check the assembly before taking to launch site. Monitor weather conditions for any sign of potential threats. Call of launch if wind prevents too much of a risk. 34

36 Improper Ventilation of a work area Improper usage of tools and materials Travel injuries Working indoors during Winter months. Failure to maintain work area properly. Unfamiliarity with tools or material. Insufficient safety oversight during assembly. Accidents loading or unloading vehicles. Improperly stored materials, or a car accident. 1 5 Multiple team members may be affected. Loss of crucial manpower or disciplinary actions could slow project development. 3 3 Improper usage of equipment may result in critical damage to the rocket. Various parts may need to be remanufactured or purchased before work can continue. 1 3 Multiple team members or supplies may be injured or damaged. Affected team members may require serious medical attention. Team members may injure themselves or others. Improper usage of especially dangerous equipment (mills, lathes, black powder, etc.) could require serious medical attention and may even result in death. Team members may receive minor injuries while loading and unloading supplies into vehicles, a car accident could potentially be life threatening or minor Work area may become contaminated with dangerous materials. Toxic or otherwise dangerous materials may be released into the environment. Materials may spill onto ground. Ensure work area remains in good condition and handle dangerous materials with extra caution. Observe all safety protocols and requirements for the necessary equipment and materials. Proper use of PPE while handling supplies. All supplies will be securely stored in the vehicles. All team members will abide by traffic laws and wear seatbelts. Travel waivers will be signed in advanced of travel. 35

37 Rocket lands in a tree line Rocket lands on power lines. Educational Outreach students fail to participate safely in a launch of low powered rocket. Change in weather conditions so rocket land in tree line. Change in weather conditions make rocket land on a powerline Inexperienced students attempt to handle and launch a low powered rocketry unsafely Figure 23: FMEA Table 2 3 The rocket will not be recoverable, so all information tested and results from experiments will not be recovered. 2 3 The rocket will not be recoverable, so all information tested and results from experiments will not be recovered. 3 3 Rocket could ignite near people in an off nominal direction, ending the education day If members attempt to recover the rocket they may fall and hurt themselves. If rocket is attempted to be recovered team members may be electrocuted or fall from a high place. Students could be burned or hit by debris Due to the weight of the rocket there may be damage to the tree that it landed on. If not recovered right away chemicals from building and launch may spread onto ground. If rocket is not recovered right away chemicals from building and launch may spread onto ground. Ground debris. Test weather conditions before launch to ensure the rocket is recoverable. Review launch site, launch away from power lines, if not possible, do not attempt recovery. Keep students at a safe distance, only allow handling with proper training on low powered rockets. 36

38 4.3 Safety Checklists Safety during rocket construction and assembly is imperative to a successful launch. The following checklists will be broken into construction safety and assembly safety followed by a list of expected tools to be used and potential injuries associated with them. A launch procedure checklist is listed and is based on the NAR launch procedure checklist Rocket Assembly Checklist Procedural Step Sign Here if Completed Sign Here if Unable to Complete Activate Payload Experiment (Procedure still to be written until payload designed is finalized) Install two fresh 9v batteries into battery clips inside of electronics bay. Apply tape to fasten the clips. Insert batteries into the battery holders and fasten in place with zip ties. Ensure altimeter switches are in off position Connect leads from switches to respective altimeters Connect wires from altimeters to terminal blocks on both ends of electronics bay Final check of all wiring, ensuring wires lead to correct locations Place electronics bay end cap into place and fasten with nuts Cut four e-matches to length and strip ends Insert e-match leads into terminal blocks and tighten Place end of e-matches into charge caps, taping the leads down with electrical tape Place end of e-matches into charge caps, taping the leads down with electrical tape Insert recovery wadding into charge caps and secure with masking tape 37

39 Attach quick links to ends of both shock cords using double overhand knots Attach one shock cord to the motor mount, tighten quick link On other end of shock cord, attach the main parachute and the Nomex blanket through the quick link Attach quick link to main parachute side of electronics bay through the eyebolt and tighten Attach other shock cord to eyebolt on payload bay and tighten quick link On other end of shock cord, attach drogue parachute and Nomex blanket to eyebolt on drogue parachute side of electronics bay and tighten Pack drogue parachute into upper body section of rocket Insert electronics bay into upper body section Insert four nylon shear pins into body of rocket, cover pins with electrical tape Insert electronics bay into lower body section of rocket Check fit of previous connection, lower body should slowly slide when rocket is shook Inspect motor retention, ensure all screws are tight Inspect motor for visual defects Insert motor into rocket body Tighten motor retention ring down Place rocket body together Insert Shear Pins (add masking tape) Rocket is ready to move to launch rail Figure 24: Rocket Assy. Checklist 38

40 4.3.2 Construction Checklist Procedural Step Sign Here if Completed Sign Here if Unable to Complete Verify participants have been trained on equipment to be used and any waivers are signed Clean work area Identify tools to be used and set out proper safety equipment Verify SDS are available Figure 25: Construction Checklis Tool Potential Injuries Risk Mitigation Procedure Drill Skin lesions, electrical shock. Inspect cord and outlet integrity, wear safety gloves Sanders Skin abrasion, dust inhalation Safety gloves and painters mask Epoxy Respiratory irritation and skin Wear rubber gloves, respiration equipment irritation and ensure area is properly ventilated. Paint Inhalation concerns Paint in a properly ventilated area Glue Skin irritation Wear rubber gloves Fiberglass Pliers and Cutters Fiberglass being inhaled, cutting skin or entering eyes Skin lesions when working with pliers or an X-acto Blade Wear a painter s mask if friable, gloves and safety glasses or goggles Wear safety gloves, if unable to perform small tolerance procedures with gloves on ensure careful work with first aid kit on hand Batteries Chemical leak or minor explosion Store batteries at designated temperatures and charge and discharge to manufacturers specifications Figure 26: Risk and Injury Launch Procedures Checklist Launch Procedure Steps Sign If Completed Sign if Unable to complete or incomplete Rocket is placed onto lowered launch rail (verify all launch lugs are engaged) Rail is raised to desired angle based on wind speed and direction Activation of Altimeter with screw based power switch Listen for altimeter power up 39

41 beeps Repeat above steps for second altimeter Connect rocket to ignition source Exit pad safely Verify ground station has GPS lock Inform LOC rocket is ready for launch Recover rocket when given permission from range coordinator Figure 27: Launch Procedure Checklist 40

42 5 Payload Criteria 5.1 Payload Objective The selected payload will be the induction and countering of the rocket's roll during ascension. The roll must be fully controlled by mechanical operations; passive rotation will not be incorporated into the design. The control sequence will be as follows: 1) Motor burns out. 2) On board instrumentation shall account for any natural rotation of the rocket (can be measured at burnout). 3) The roll system shall induce a moment capable of generating at least 2 full rotations. 4) After 2 full rotations, the roll system shall induce a moment to counter rotate. 5) The system shall return the rocket to the initial rotation measured at motor burnout. The roll and counter roll induction must be performed during ascent before the rocket reaches apogee. A successful payload will achieve the required minimum number of rolls and return to the initial roll measured. Assessment of the natural roll shall be performed by the onboard inertial measurement systems; proof of the roll control shall be provided by data from these same measurement systems and stored locally for verification after rocket recovery. 5.2 Payload System Design Alternative Designs Multiple payload designs were considered by the team, focusing on the number and arrangement of servos and methods to attach the control surfaces to their shafts. Various electrical power and control mechanisms were also explored before settling on the preliminary design Four Servos The proposal for Project Cairo presented a payload option utilizing four servo motors to drive the control surfaces. As shown in the initial design in Figure 28, each control surface was mounted directly to a servo. Each servo would be mounted around the longitudinal axis of the rocket. 41

43 Figure 28: Four servo layout This plan was the first design considered by the team. By using one servo for each control surface, the torque requirements of each servo was lower than a single servo design. Additionally, a four servo design allowed each control surface to be connected directly to the servo. Direct connection to the servo removes the need for gearing or other power transfer systems. The design shown above proposed utilizing servo horns as an attachment method. The four servo design did have some negative considerations, however. Four servos require a larger battery which is a significant source of mass. Due to the size of servos, a four servo design necessitated a five inch diameter rocket body, also increasing rocket mass. Another possible issue with four servos is any performance differences in the servos. Using four servos may cause errors induced by accuracy, speed or torque performance differences between the servos used. Due to the above considerations, this design will not be carried forward after the proposal Single Servo A single servo alternative to the original four servo design was proposed after the project Cairo Proposal was submitted. The single servo design continues to rely on four control surfaces in an identical arrangement to the four servo design, however, the control surfaces are powered by a single servo through a four direction bevel gearbox. The single servo design is described in detail in section Preliminary Design. The single servo alternative addresses a number of the negative considerations of the four servo design. The use of a single servo removes any performance or accuracy differences between multiple servos. This allows the payload software to control a 42

44 single servo in order to control the vehicle s roll rather than controlling four independent surfaces while guaranteeing that the surfaces operate synchronously. Another four servo negative aspect that is addressed by a single servo design is the contribution to final vehicle mass. A single servo can utilize a battery that is smaller than what would have been used in a four servo design, which correlates to a lower mass. Additionally, the arrangement of a single servo with gearbox is a smaller profile than the four servo design, allowing the rocket body to be four inches in diameter. The decrease in rocket body diameter reduces the mass and cost of the rocket, and the lower mass improves safety. The negative aspects of the single servo design focus on the torque requirements of the servo motor. In this design, the servo must have the torque to control all four control surfaces at the same time. Additionally, because of the gearbox, there are mechanical losses between the servo and the control surfaces, a consequence that did not exist in the four servo design. These considerations lead to the selection of a high torque servo motor in order to ensure the ability to actuate the control surfaces Control Surface Fastening One of the primary design concerns after what would actuate the control surfaces was the means of fastening the fins to the control device. The external portion of the control surface is proposed to fasten to the external part of the fin above via a pin that will fit the bore diameter of the through hole cut along the leading edge of the surface. However, difficulties arise at the base of the control surface due to the combination of the narrowness of the fin (.25" at the maximum), the size of the shaft coming from the differential, and the machining necessary to fix the two together. Initially, the design called for the shaft from the differential to fit to the internal diameter of the surface's through hole. Fastening would require the use of a set screw or a key. However, numerous concerns developed over the deflection that would be occur in a shaft that fit within the narrow fin. There were also concerns about the machining process itself as the effect of drilling a hole large enough to fit a suitable shaft may reduce the structural integrity of the fiberglass surface. In addition, a coupler would be required in order to fit the differential to a narrow enough shaft since most of the gears considered for the differential fastened to shafts much larger than the surface could reasonably handle. While the above design did provide relative simplicity an alternative design of slotting the shaft itself was proposed. In this design the surface slides into the shaft rather than the other way around. A set screw would fasten the two together. This design further simplifies the mounting but would require significantly more machining. Perhaps, the biggest concern of this option is the wrapping of the shaft on the outside of the control surface, and thus, significantly altering the aerodynamics of these fins. Since the fins are relatively small these aerodynamic effects may significantly alter the surfaces characteristics. Further analysis is still necessary on this aspect of the design. 43

45 Electronic Control To control the complex mechanism used in this project, a microcontroller is a necessity. Initial plans called for the use of a generic Arduino board that would make use of several sensors and peripheral devices each operating on their own breakout board. While this design promises device compatibility, up to date documentation, and a large support community, an initiative was undertaken to begin the design of a custom Printed Circuit Board that would contain the same components on a single board. This approach would reduce the number of individual components required within the rocket and would be streamlined to perform only mission critical operations. Additionally, this option encourages further involvement in the group from Electrical Engineering students whilst simultaneously developing the skills of the team for future competitions. For this reason the design of the Active Roll Control Unit(ACRU) printed circuit board(pcb) was imagined; further details on this design are available in section However, this approach does have a few drawbacks. Much of the manufacturing is proposed to occur outside of established vendors. Any step in the process, from the initial design to the manufacturing, could experience delays and difficulties that prevent the development of the system in time for the competition. Also, while some spare connections have been made available, the ACRU lacks the adaptability of a standard Arduino based system and thus any significant design changes will also require a complete redesign of the PCB itself. In order to skirt some of these issues from occurring a secondary, backup system will also be designed. This design follows the original breakout board design. By developing this backup system in tandem with the ACRU testing can be performed on a stable platform before the final PCB is produced. Compatibility between the two modules guarantees that if the ACRU succeeds the program can be copied from the secondary to the primary system. If the ACRU fails, then a fully functioning electronics bay will still be available Alternative Means of Roll Induction Options other than control surfaces were also considered. The first alternative proposed was a mechanism resembling that of a reaction wheel. In this configuration, an electric motor would spin up or down a disk within the rocket body. Because of the conservation of angular momentum, the rocket body would be forced to roll opposite the direction of the reaction wheel. The major benefit of this design was its simplicity and the lack of external surfaces. However, it was decided that this design would not be pursued due to the significant mass of the reaction wheel that would be required to roll the rest of the body, large delay times between the control and response, and the mechanical and electrical designs that would allow a device to roll at such high speeds without experiencing stability issues or potential catastrophic failure. Another proposed method of initiating roll was a device resembling that of reaction control system (RCS) thrusters. However, this method had few benefits and many significant drawbacks, namely, this mechanism requires on board high pressure storage which presents significant safety concerns as well as large increases in rocket mass; complex control requiring multiple solenoids synchronizing across the rocket's profile; 44

46 and lack of precision as a result of the pulsing nature of this method (the valves would release and uncertain quantity of material at each activation). Only the lack of external control surfaces (although external ports would be necessary) give this design an edge over the control surfaces Preliminary Design Mechanical Design The Mechanical design of the preliminary payload design utilizes the single servo design. A single high torque servo will be used to drive all four of the control surfaces, which are spread radially around the rocket body. Each rigid fin will be attached to an internal tube, similar in construction to a typical fin can assembly. The gearbox utilizes bevel gears to transmit torque from the servo to the shafts the control surfaces are attached to. The electronics are positioned below the gearbox and control surfaces, attached via threaded rods that run the length of the payload assembly. Finally, the fincan section of the rocket will slide over the payload and be screwed into place below the control surfaces. Figure 29: Preliminary Payload Assembly Figure 29 shows the completed assembly of the payload. The payload is comprised of stacked layers that hold electrical components in place. Each colored layer is a 3d printed part. 3D printed allows for parts with relatively high tolerance that are design specifically to accommodate the payload components. The 3D printed parts will have an 45

47 internal lattice structure which will allow the parts to be primarily hollow, while providing structural stability. Fiberglass bulkheads are located in multiple locations inside the payload. Two bulkheads are positioned directly below the gearbox, where the servo will be mounted. Attaching the servo directly to the fiberglass bulkhead ensures any forces that are transferred to the servo will not damage the 3D printed supports. A final bulkhead is located at the aft end of the payload where nuts will clamp the entire assembly together. The lattice structure of the 3D printed parts will provide compressive strength to the payload, however 3D printed parts lack tensile strength. To avoid the delamination of Fused Deposition parts, the threaded rods and fiberglass bulkheads will absorb the tension exerted onto the payload. Figure 30: Payload Exploded View Each layer in the payload assembly helps hold electronics components in position. The 3D printed parts are modeled to allow ease of printing. Overhangs are limited in number and location, to allow the parts to be printed without additional supports. The payload circuit board will be sandwiched between the blue and yellow layers. A lip is modeled into the top of the blue layer, so the circuit board can rest inside. The yellow layer will clamp down around that outside edge of the circuit board, holding it in place without the need for standoffs or screws. This design allows for the easy access to the circuit board. Below the yellow layer is the battery compartment. The battery compartment is straight-forward in design. A cutout will accommodate a two cell LiPo battery, with a hole for wires to be fed to the circuit board. The bottom fiberglass bulkhead will hold the battery in place and cap off the payload assembly. Figure 30 demonstrates how the layers will stack and shows the cutouts and features that will hold components in place. 46

48 A gearbox is used by the payload to transmit torque from the servo to the control surfaces. This gearbox is shown in Figure 31. A servo to shaft coupler will connect the servo to the quarter inch drive shaft. A thirty-two tooth brass bevel gear will be attached to the drive shaft and a set screw will provide a solid connection to the shaft. Above the drive gear, four sixteen tooth gears will mesh in with the drive gear. Each sixteen tooth gear will be attached via set screw to their own quarter inch shaft. These shafts will run through bearing pillow blocks, that will be screwed into the fiberglass bulkhead above them. On the opposite side of the pillow blocks from the gears, a sleeve is attached via a setscrew to prevent the shaft from sliding inwards. The gears will also prevent the shafts from sliding outwards. Figure 31: Gearbox Assembly 47

49 Figure 32: Control Surface Model Four control surfaces will be mounted onto the gearbox shafts located below the rigid payload fins. The shafts will fit inside of a matching cutout in the control surfaces. Set screws will screw into two holes on top of the fin to give each control surface a rigid connection with its shaft, similar to the method of attachment used by the brass gears. The shaft will run through most of the length of the control surface, to counter the moment induced by drag. The control surfaces will be 3D printed using a specialized printer utilizing a high strength ABS plastic. This design allows for ease of attachment, strong structural stability and rapid manufacturing. Prototypes have been printed for validating the design of the control surfaces. Samples printed in the high strength ABS will be produced at a later time for strength testing and final validation. A photo of the printed prototype control surface is in Figure

50 Figure 33: Control Surface Prototype with 10mm cube for scale The torque expected on each fin was calculated in Matlab using equations provided in the OpenRocket technical documentation. Equation 3, originally provided by Barrowman, is used to calculate the normal force coefficient acting on the fins in subsonic flow. (C Nα ) 1 = 2π s2 A Ref βs 1+ 1+( 2 A fin cosγc )2 Equation 3 Where s is the fin s span, A Ref is a given reference are (often the base of the nose cone), β is 1 M 2 with M being the Mach number of the flow, A Fin is the area of the fin, and Γ c is the midchord sweep angle of the fin. Note that this equation is non-dimensional and that the subscript 1 indicates it applies to a single fin. The force can then be found by using equation 4 where q is the dynamic pressure (. 5ρv 2 ) and δ is the deflection angle of the fins. F N = δ(c Nα ) 1 qa Ref Equation 4 49

51 This force will act at the center of pressure (C P ) of the fin. Thus if the center of the fin s axle is at the leading edge of the fin it is only necessary to find the distance from the leading edge to the center of pressure to find the torque exerted on the shaft. The center of pressure is located at one quarter of the mean aerodynamic chord from the leading edge when the velocity of the flow is less than.5 Mach. Above this point the location follows a fifth-degree polynomial and another equation then explains behavior above Mach 2. When calculating the torque acting on the shafts a number of assumptions were made. Namely, the air density was equivalent to air density at the surface; that the velocity of the flow was Mach.8; the fins are trapezoidal; that the angle of attack is determined solely by the deflection of the fins; and that the deflection will be limited to +/- 10 degrees. This speed was chosen as it represents a worst-case scenario as it marks the boundary of transonic flow above which calculations must be drastically altered and sufficient safety concerns are present. Taking these numerical values and the given fin size it is possible to calculate the maximum torque experienced by the shafts. The results are shown in figure 34. Note that the maximum torque on a single fin is around 2kg-cm and thus the total torque required to hold all four fins would be 8kg-cm. Including the differential s 2:1 ratio increases the necessary servo torque to 16kg-cm. To ensure safety an additional factor of safety of two was added on top of the conservative estimate to produce a minimum required torque of 32kg-cm. The selected servo can exceed this torque by an additional 8kg-cm at stall. Figure 34: Rotation vs. Torque 50