Project
320 Flight

Post-flight Analysis

• These two rockets had 34% more power and weighed 14% less than the 228 rockets. They had good acceleration off the pad but seemed to loose momentum very quickly once the engine cut out. The total weight of each rocket was 13.75 lbs.
• 2.6 lbs. of water ballast was used in the forward section of the rockets to add aerodynamic stability and cool the ejection charge. A 17 second time delay, which was way too long, was installed in the ballast tank. The hot exhaust was ducted under water through the tank, then out the side of the rocket casing. Pictures and drawings of the ejection timer construction were accidentally deleted from my computer so will have to be done again next month.
• Because the parachutes were ejected so late, they were ripped off the rocket and the rockets came back down ballisticly.
• Each rocket had a J300 engine which produced 1200 Ns of total impulse. Each engine contained 2.6 lbs. of 60/40 fuel and weighed 5 lbs. total with the nozzle, end cap and igniter.
• 1 lb. of 60/40 fuel was built into the nosecone to burn during flight and act as a smoke tracer. The smoke from the nosecone was not under any pressure other than it's own.
• 2 lbs. less water was put into the second flight due to the first flights lack of momentum but this did not seem to make any difference except for reduced stability.
• Also tested were two engines constructed with schedule 40 PVC and two engines with 25% less 65/35 fuel than the 228 tests in schedule 80 PVC. All of these tests did not perform as well as the current J300 engine configuration.

Construction

• Engine casing was made out of 3" ABS. Both engines were made out of schedule 80 PVC with 16" of 60/40 fuel and a .7" throat.

Pros

• Igniters worked very well.
• Engines worked consistently and reliably.
• Water ballast works well for increasing aerodynamic stability.
• Delay charge and ejection charge worked well.
• Parachutes worked well except for being ripped off the rockets.
• Nosecone smoke worked well.

Cons

• Obviously a chemical delay element is not ideal for recovering the rockets. But in this engine testing phase, it's a lot cheaper than blowing up several event timers.

Pictures

Video

• Flight 01
• Flight 02 with 2 lbs. less water in the ballast tank

Drawings

None

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