Problem Animation
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Delta 2 Rocket (US)
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Mu-3SII Rocket (Japan)
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The lead engineer on the new Starfinder rocket must determine the force in each member of the inter-stage truss structure. If the load is too high, the first-stage thrust will buckle the truss members.

What is known:

  • The base ring radius is 1 m.
  • The top ring radius is 0.75 m.
  • The base and top ring are 1 m apart.
  • The total thrust of the first-stage main engine is 2,400 kN (300 kN per joint).


Dimension Diagram


Space Shuttle (US)
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What is the force in each of the truss members of the truss structure between the second- and third-stage rockets when the first-stage main engine is firing?


  • Sum all forces at a joint (method of joints).

         ΣF = 0

  • Find the 3D unit vectors for all forces at the joint. Find the unknown magnitudes of the member forces.