STRUCTURES

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STRUCTURES
Primary Material Downselection

• Mass Estimating Generator for Structural
  Components (MEGSc)
• Excel based software package
• Internal to TBA
• Allows for quick relative mass comparisons
  between various
• aerospace materials as applied within
  particular launch
• environments

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STRUCTURES
Primary Material Downselection

• Mass Estimating Generator for Structural
  Components (MEGSc)
• Idealizes the spacecraft within the launch
  vehicle fairing as a
• cantilevered cylinder whose mass is evenly
  distributed
• Capable of computing the minimum thickness of
  the
• cylindrical monocoque to meet all given
  conditions
• Leading to a 1st order approximation of
  structural mass

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STRUCTURES
Primary Material Downselection
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STRUCTURES
Primary Material Downselection

• Aluminum 7075
• Readily available
• Relatively inexpensive
• Weldable
• Easily machined and formed
• High strength
• Low density

Ideal Material For Constructing Spacecraft Bus
and Necessary Support Structure
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STRUCTURES
Bus Structure

• Initial Estimates
• Diameter 3 m
• Length 3 m
• Thickness 0.6 cm
• Mass 475 kg

Insert CAD of main spacecraft
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STRUCTURES
Bus Structure Sandwich Construction
A
C
B
12-cm
12-cm
12-cm
0.5-cm
3.33-cm
1-cm
3.0-cm
0.5-cm
(Core Does Not Contribute)
A) Thin face sheets have little bending
stiffness, as indicated by the small value of I.
B) The bending stiffness is increased by
separating the faces with a low density core.
C) A monocoque wall thickness of 3.33-cm is
required to obtain bending stiffness equal to the
sandwich panel at three times the mass.
Provides 10 Reduction, Optimizing Bus System
Mass at 425 kg
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STRUCTURES

• Other Considerations
• Interstage Adapter
• 3 m diameter by 2 m sandwich constructed shell
• MEGSc software used to estimate mass at 285 kg
• Thrust Structure
• Approximated based upon percentage of total
  vacuum thrust
• provided by the seven NTRs
• Assuming 0.25 of total stage vacuum thrust,
  mass is
• estimated at 25 kg.