Characterizing SF propellant part 2

Additional tests were performed on August 15th,2020 on the SF propellant.

The 3 additional tests were performed with the following changes:

Graphite nozzles replaced plastic nozzle
Grains were accurately weighed prior to each firing
Pressure transducer piping was completely packed with high temperature lithium grease.

Run 1: 21/64 throat straight nozzle

Pressure vs. Time data

Pressure Data 21/64" throat

Force vs time data

Force Data 21/64" throat

Results:

Peak pressure 1026 PSI +- 8PSI
Average Pressure 816 PSI +- 7 PSI
Peak Force 95.5 lb +- 3 lbs
Average Force 75 lb +- 3 lbs
Burn time: 2s +- .1 s

Run 2: 22/64 throat straight nozzle

Pressure vs. Time data

Pressure Data 22/64" throat

Force vs time data

Force Data 22/64" throat

Results:

Peak pressure 886 PSI +- 7PSI
Average Pressure 638 PSI +- 7 PSI
Peak Force 88.4 lb +- 3 lbs
Average Force 64 lb +- 3 lbs
Burn time: 2.3s +- .1 s

Run 3: 23/64 throat straight nozzle

Pressure vs. Time data

Pressure Data 23/64" throat

Force vs time data

Force Data 23/64" throat

Results:

Peak pressure 691 PSI +- 6PSI
Average Pressure 543 PSI +- 5 PSI
Peak Force 79 lb +- 3 lbs
Average Force 61 lb +- 3 lbs
Burn time: 2.4s +- .1 s

Comments

Characterizing 38mm PVC motors

A previous article described fabricating PVC motors using couplings and endcaps to secure the bulkheads. Figure 1: PVC fitting used to retain grains in 2" diameter PVC motor with cork liner. In an effort to make the motors more flyable, the motors have been redesigned without those elements. First attempts consisted of drilling a series of 4-6 radial holes and casting the rockite into the holes. This provide insufficient to retain the bulkheads in 4/6 tests, and none of the successful tests exceeded 150 psi. Figure 2: Note the forward bulkhead and nozzle bulkheads are extruded out from the pvc. The next attempt was to cut a 0.25" section 1 1/4" PVC pipe, slit it and glue it into the end of the 1 1/2" pipe. The Rockite was cast with this lip retaining it. This was successful in 1/4 tests, but the successful test did hold 380 psi, and the other tests failed at above 300psi. Here is the data from the...

Low pressure temperature performance of KNSb propellant

Tests were performed on the temperature effect on burn rate for KNSb as follows: Four grains were prepared as follows: 3" Diameter grain 5.5" long 1" Core 3.5" Diameter casting tube 1040 grams propellant +- 50 grams Humidity controlled to < 10% The grains were placed into a low pressure test motor .85" nozzle throat - .02" 98mm phenolic liner KN 65 Single Grain motor from Rick Maschek Notes: Four tests were performed with one failing due to an improperly seated snap ring. Force data was measured directly and the pressure was obtained basd on the nozzle throat and Cf value for the motor. Test 1: Grain Temperature 55oF +- 5 Data: Peak Pressure 6.7 PSI +-7 Average Pressure 5.5 PSI +- 6 Peak Force 5 lbs +- 3 Average Force 4 +- 2 Burn Time: 18.3s +- 1.8s Note: The low pressure of this burn makes it difficult to estimate burn time. The original estimate was on the order of 16 seconds. Test 2:...

New website to track projects

For over a decade profmason.com was a repository of over 200 electronics and robotics projects that I completed between 2004-2014. In 2016, my web provider disappeared along with all access to the website. After spending 2 years and 9 months trying to get the domain back from the Panamanian domain squatter who had bulk purchased my domain when it came up at the registry, I have decided to start a new blog to document my projects new and old.

Robotics and Rockets

Search This Blog