Characterizing SF propellant V4

Tests were performed on Jan 16th,2021 on a new variant of the SF propellant (SF 4).

Graphite nozzles had a 45 degree converging element and 15 degree diverging element. These were nozzles that had previously been fired.
Pressure transducer piping was completely packed with high temperature lithium grease.
Identical force and pressure transducers were used to previous tests
Tests carried out in collaboration with Davie Bauld and Andrew Irvine. SF and SF 4 formulations are developed by Jerry Irvine. For custom propellant formulation and a wide variety of launch services, contact US Rockets at usrockets.com

Run 1: 22/64 throat

Pressure vs. Time data

Force vs time data

Results:

Peak pressure 526 PSI +- 8PSI
Average Pressure 444 PSI +- 7 PSI
Peak Force 39.1 lb +- 3 lbs
Average Force 32.7 lb +- 3 lbs
Burn time: 2.9s +- .1 s

Notes: A. Irvine noted from video observation that there was an ejecta at approximately the 1/2 s point. On final inspection of the nozzle, the nozzle showed signs that the throat had been eroded.

Run 2: 19/64 throat

Pressure vs. Time data

Force vs time data

Results:

Peak pressure 552 PSI +- 7PSI
Average Pressure 465 PSI +- 7 PSI
Peak Force 45.4 lb +- 3 lbs
Average Force 35 lb +- 3 lbs
Burn time: 2.7s +- .1 s

This propellant appears to have a lower pressure exponent then the previously characterized SF propellant.

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