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ENG File: P2.eng
Discussion
Timeline
Liner Splice Failure
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Observations
•Erosive burning spike was observed in thrust curve, then progresses with normal BATES thrust profile until nozzle failed
•Nozzle cracked at phenolic interface
•Casting tube was likely ejected at +3 seconds around the same time the nozzle cracked, corresponding to the burnout of the aft grain
•Liner surrounding aft grain was ejected at +6 seconds
•Leak path at nozzle crack led to significant loss of pressure and thrust
What caused this?
•Increased Al combustion in high L/D motor raised temperature and interacted with other compounds to enter an uncharacterized combustion regime
•Nonlinearity in burn rate law (r = aP^n) unrelated to Al combustion
•Burning on outside of grains (inside of casting tubes)
Reconstruction of Events
•T-0: The igniter actually works and motor ignites
•T+.5: Erosive burning spike settles down, but motor is now burning at a much higher pressure than expected due to higher Al combustion effect on burn rate law
•T+.5 - 2.9: Thrust curve follows typical BATES profile
•T+2.9: Aft grain burns out, casting tube is ejected
•T+2.9: Interaction with casting tube event along with elevated thermal and mechanical stresses causes nozzle failure
•T+2.9-6.2: Motor continues to burn at lower pressure/thrust due to fewer grains, leakage at nozzle break
•T+6.2: Second grain from aft end burns out, unprotected liner at aft end is ejected due to high velocity gas passing over it
•T+7.8: Motor shuts down
Where do we go now?
•Option 1: Build the same motor again for SAC and reconsider the vehicle’s structure to handle higher loads
•Option 2: Redesign the motor for combustion in the “aggressive” regime, static test it, and then rebuild it for SAC
•Option 3: Redesign the motor for the “aggressive” regime, but don’t static test it before SAC
•Option 4: Descope to 4G motor
How much additional money would the team need to spend to complete each option?
•Option 1: $690 (not including structural redesign)
•Option 2: $1,137
•Option 3: $690
•Option 4: $0