Team Weatherman Completed Design Review

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Team WeathermanCompleted Design Review

• James Banks, Test Engineer
• Katonio Butler, Electrical Specialist
• Alex Cutting, Structural Engineer
• Lori Huberman, Aerodynamic Design Engineer
• Cassandra Roth, Computer Design Specialist

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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.

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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.

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Scale Drawings

• Bottom

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Scale Drawings

• Front

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Scale Drawings

• Side

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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 60o 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.

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Aerodynamic Analysis

• VEHICLE WEIGHT
• Quantity Weight (kg)
• Engine 1 .21
• Engine Batteries 6 .05
• Propeller 1 .0052
• Receiver 1 .027
• Servos 2 .043
• Receiver Battery 1 .094
• Structural Frame 1 .077
• Mylar Sheaf 1 .024
• Balloons 4 .07
• Total 1.10 kg
• Total without balloons 0.823 kg

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Aerodynamic Analysis

• VW/(pair-pHe)g1.05m3
• This corresponds to 10.78N of lift needed.
• L(pair-pHe)gV16.1N

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Aerodynamic Analysis

• Thrust one large engine (9V)1.3N
• VelocityT/(.5Scd)1/22.91m/s
• Drag.5pairv2cd1.03N

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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.

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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.

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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 carpenters 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.

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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!