HEI - Head End Ignition

Please review the HEI Information page to get a general overview. 

For staged rockets, the second stage has to be ignited near Vacuum space. We need a system that can raise the pressure in the chamber while increasing the temperature to reach combustion conditions.

Design Changes and Verification

Forward Closure

With respect to the HEI used in the staging demonstrator, we increased the wall thickness and added a fillet between the base and the wall.

To calculate the MoS we use an ID of 1.375 in, an OD of 1.842 in, and the maximum pressure of the Sustainer with 826 psi.

\sigma_H = \frac{P*r}{t} = \frac{(826 psi)*\frac{1.375 in}{2}}{\frac{1.842in-1.375in}{2}} = 2432.01 psi

6061-T6 Aluminum has a yield stress of 40000 psi.

  MoS = \frac{40000 psi}{2432.01 psi} -1 = 15.4 

Thus, the margin of safety is much more than the required minimum of one, which makes us confident that the wall will not yield.

Nevertheless, we would not decrease the wall thickness since we want to avoid radial tore of the bolts.

Bolts

O - Rings

After finding that the previous O-Ring Configuration had potentially dangerous attributes according to https://www.applerubber.com/oring-gland-calculator/#medium-search-field. I changed the O-rings to yield safe values and uploaded the changes to the repository. I changed the 229 and 228 O-Rings to 230 and 229 respectively, then the 121 and 122 O-Rings to 122 and 123. Below are the images of the O-Rings and the values in the calculator.

O-Rings 1,2:

O-Ring 3: (Best stretch Arrangement I was able to produce without changing the Forward closure groove diameter (Am I allowed to?)

O-Ring 4:

O-Ring 5:

 

Igniter Grain

No Change, show open motor curve and talk about funny canted nozzles

Manufacturing

Forward Retention

hei_fwd_retention.SLDDRW

  • Use the water jet cutter to radially drill the holes for the screws
  • Do not thread the screw holes, because the threads could mismatch with the ones in the forward closure

Igniter Nozzle

ig_nozz.SLDDRW

  • Put two pieces of phenolic on the lathe, use it to get their dimensions right.
  • Hand drill the canted holes in the nozzle
  • Glue the phenolic pieces together

Igniter Grain

bt_igniter_grain.SLDDRW

  • Cut the grain slowly with a drill by hand
  • Extremely important to go slowly so as to not ignite the grain

Igniter Liner

ig_liner.SLDDRW

  • Cut the liner to length with a saw

Phenolic Forward Closure

hei_fwd_closure.SLDDRW

  • Use the water jet cutter to drill the holes
  • Use the lathe for the grooves

Forward Closure

fwd_closure_hei.SLDDRW

  • Use the new digital lathes for the curve because they can do tapers and complex geometries
  • Put the closure on the mill for holes and bolts
  • Thread the scew holes

Phenolic for Forward Closure Insulation

Phenolic for forward closure.SLDDRW

  • Use the water jet cutter for the hole

Integration

Custom E-Matches

  • Use redundant matches to avoid failed ignition

Safety

  • Be extremely careful when working with grains
  • Exercise caution with machining tools

R2E

  • Include R2E between the phenolic forward closure and the forward closure
  • Put it between the igniter nozzle and forward closure
  • Put it between the threaded rods and the phenolic closure

 

 

 

 

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