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Testing ANCP motors

A total of 5 ANCP motors were produced and tested.  A full test video is available here:  


These are all conventional Ammonium Nitrate composite propellants that use Magnesium to increase temperature and HTPB as a binder.  

The 5 motors manufactured are as follows:
  • Motor 1:  250 PSI regressive (5.5 s burn time)
  • Motor 2: 350 PSI regressive (5.0 s burn time)
  • Motor 3: 350 PSI progressive (4.5 s burn time)
  • Motor 4: 400 PSI regressive (4.5 s burn time)
  • Motor 5: 400 PSI progressive (4s burn time)

The chart show below shows safety factors for PVC motors (at 70 degrees F) with Pressure shown vertically and burn time shown horizontally.  There is  low overall confidence in this model. The case failure as a function of pressure based on the tensile strength of the PVC is well understood, but PVC changes strength rapidly with temperature.  As the burn time increases, there is heat transported to the PVC case which causes its strength to drop rapidly.  An exponential model of heat transport into the PVC has been implemented, but again there is low confidence in the results. The following table is presented as only a first take on appropriate pressures and burn times for 2" PVC motors. 


Looking at the motors tested compared to predictions gives the following results:

  • Motor 1:  Actual pressure 205 PSI burn time 5.5 s  Safety factor 1.77 Success
  • Motor 2: Actual pressure 360 PSI burn time 5 s Safety factor 1.25 Failure
  • Motor 3:  Actual pressure 352 PSI burn time 4.5 s Safety factor 1.39 Success
  • Motor 4: Actual pressure 410 PSI burn time 4.5 s Safety factor 1.09 Failure
  • Motor 5: Actual pressure 402 PSI burn time 4 s Safety factor 1.21 Success

In the next post, there will be detailed analysis of motor 3. 

Comments

  1. adelaidetestandtaggingFebruary 11, 2021 at 2:00 AM

    After reading the above posts, I got some useful knowledge which is really informative. Thanks for posting it. Test and tagging 

    ReplyDelete

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