1. Team Weatherman Completed Design Review James Banks, Test Engineer Katonio Butler, Electrical Specialist Alex Cutting, Structural Engineer Lori Huberman, Aerodynamic Design Engineer Cassandra Roth, Computer Design Specialist

2. Objective To design a lighter-than-air vehicle that not only meets all design requirements, but is also original and as light as possible, using a cyclical design process.

3. Introduction to Final Design We decided that the decisive factor in the LTA design is the amount of drag created. We opted not to pursue the one balloon design due to its lack of stability. The triangular three balloon design was eliminated because of the extreme amount of drag and the weight of the truss that would be required. We chose the in-line, four balloon, airfoil-like design due to its low drag and creativity, with the single motor mounted in the front, which controls the pitch and yaw of the LTA.

4. Scale Drawings Bottom: Bottom:

5. Scale Drawings Front: Front:

6. Scale Drawings Side: Side:

7. Control Systems The shape of our LTA vehicle utilizes drag to stabilize the vehicle when in motion. We eliminated control surfaces to simplify the vehicle because of this. Our large single motor has a range of 60 o both vertically and horizontally to control pitch and yaw. Also instrumental in our decision was that the vehicle can be controlled even at low speeds.

8. Aerodynamic Analysis VEHICLE WEIGHT QuantityWeight (kg) Engine1.21 Engine Batteries6.05 Propeller1.0052 Receiver1.027 Servos2.043 Receiver Battery1.094 Structural Frame1.077 Mylar Sheaf1.024 Balloons4.07 Total: 1.10 kg Total without balloons:0.823 kg

9. Aerodynamic Analysis V=W/(p air -p He )g=1.05m 3 This corresponds to 10.78N of lift needed. L=(p air -p He )gV=16.1N

10. Aerodynamic Analysis Thrust – one large engine (9V)=1.3N Velocity=T/(.5Sc d ) 1/2 =2.91m/s Drag=.5p air v 2 c d =1.03N

11. Design Evolution and Analysis Relative Importance of Various Design Specifications Much of the early portion of the design process was spent debating what design specifications were most important. Half of the group felt that the aerodynamics were most important, while the other half felt that the weight was most important. The group that tended toward decreasing the amount of drag felt that drag would significantly slow the vehicle down, thus rendering the vehicle non-competitive. The group that felt that weight was most important, felt that the heavier the vehicle was, the less payload we could have, thus also rendering the vehicle non-competitive. We quickly realized that we need to take both ideas under consideration and made a design that is very light, but still aerodynamic.

12. Design Evolution and Analysis Motor Control We decided that the motor should definitely go in the front of the vehicle, but there was much debate over how many motors there should be and how they should be used to control the vehicle. Some people felt that there should be multiple motors to generate greater thrust. This was eliminated to decrease the amount of weight. Other people wanted to go with a one motor design, but simply use the motor to generate thrust and use control surfaces for stability. Eventually, we decided on a single motor that controls everything. Since there are less parts, there are less chances for things to go wrong. This decreases weight and increases maneuverability of the LTA.

13. Design Evolution and Analysis Main Body Structure The structure of our design centers around a single long truss down the center of the balloons. Balsa wood does not come in long enough sizes, so our group debated how to connect pieces, as well as what size balsa wood to use. Following several hours of testing, the group concluded that carpenter’s glue along with the addition of tiny structural balsa wood supports would be enough for our purposes. We also chose the thicker piece of balsa wood, after realizing how flimsy the thinner versions would be. Due to the fact that we cannot test until Trials, we opted to create a backup truss, heavier, but stronger, in the event that this truss is not strong enough.

14. Conclusion After much discussion and time spent in the lab, we have finalized our design. We have, what we believe is the lightest, strongest truss we can build for our main structure. The mylar sheaf along with the shape that the balloons create will make our LTA as aerodynamic as possible. The control system has as few moving parts as possible, but we believe that it will still be adept at maneuvering the LTA. Our in- line, four balloon, tapered design should be the simplest, yet fastest design in the competition!