Booster and Sustainer Case Dimensions

Design pressure: 1500 psi

Sustainer:

Aluminum Case: OD: 4", ID": 3.75" (thickness 1/8")

Phenolic Liner: OD: 3.75", ID: 3.5" (thickness 1/8")

Casting Tube: OD: 3.5", ID: 3.375" (thickness 1/16")

Booster:

Aluminum Case: OD: 6", ID: 5.625" (thickness 3/16")

Phenolic Liner: OD 5.625", ID: 5.375" (thickness 1/8")

Casting Tube: OD: 5.375", ID: 5.25" (thickness 1/16")

Medusa Booster

Constraints:

  • Manufacturing capability
    • Lathes can machine up to 6" diameter
  • Available liners' specs (lengths)
    • 48", 53.1", 59.1", 65"
  • Need for a casting tube within liner
    • Unless multicast in one liner is feasible
      • While potentially feasible, many have told us it is better practice to use a casting tube with each grain in sections with o-rings in between each ring
  • Available tube size
  • Tolerances of the tubes are not within rocketry tolerance (+-.001")
    • Solution: Use a simulator piece while machining the parts to achieve as good of a seal as possible
      • Simulator piece is a cut piece of the case stock. Get part to nominal diameter then test fit with simulator until it fits by hand
      • Use 300 or 400 series o-rings to hold a better seal.

Design Specs:

  • 6" OD
  • Internal pressure expected to be around 1000 psi max
  • Safety factor 1.5
  • Thickness: 3/16"

Phenolic Tubes:

  • Order from Franklin Fibres (lengths: 48", 53.1", 59.1", 65")
  • 1/8" thick for liner
    • ID: 5.375.", OD: 5.625"
  • 1/16" thick for casting tube
    • ID: 5.25", OD: 5.375"
  • long lead times, order in bulk this semester

Bolts:

2 rows of 16x 1/4-20 bolts.

Total of 64 bolts on the booster.

 

 

Medusa Sustainer

Constraints:

  • available liners' specs (lengths)
    • 48", 53.1", 59.1", 65"

Design Specs:

  • 4" OD, 3.75" ID
  • Internal pressure expected to be around 300 psi max
  • Safety factor 3
  • Thickness: 1/8"

Motor Case:

  • Order from Online Metals
  • 1/8" thick
  • ID: 3.75', OD: 4'

Phenolic Tubes:

  • Order from Franklin Fibres (lengths: 48", 53.1", 59.1", 65")
  • 1/8" thick for liner
    • ID: 3.5", OD: 3.75"
  • 1/16" thick for casting tube
    • ID: 3.375", OD: 3.5"
  • long lead times, order in bulk this semester

Bolts:

1 rows of 8x 10-20 bolts.

Total of 16 bolts on the sustainer.


 

Case Spec Calculations

Case calcs done using 1800 psi as internal pressure

Thin vs Thick Case Assumption: thin case assumption can be used if   \frac{Diameter}{thickness} < 20

Booster

Booster thin case assumption if t < 0.3"

Calculated with thin case assumption -> safety factor = 1.5, case thickness = 0.191"

 

Sustainer

Sustainer thin case assumption if t < 0.2"

Calculated with thin case assumption -> safety factor = 2, case thickness = 0.229"

Calculated with thick case assumption -> safety factor = 2, case thickness = 0.241"


MATLAB file for case calculations: case calcs.m

Python file for case calculations: case_calcs.py

 

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