P1: Nitrous at Balls in '09


Fourth Hot Fire Test

Last Update, 12/13/08 by Stephen Daniel


Summary of Results

Tests 8 and 9 failed. In both cases the pyro-valve let go before ignition.

Test Plan

Goals for this test:

  • Reliable ignition.
  • Achieve stable, burn at something close to design performance.
  • Gather accurate data.

Based on analysis of our last test, we've made these decisions.

  • For now we will stick with using commercially available sparklers as the ignition source. At some point in the future we'll experiment with adding magnesium chips to the pyro-valve to see if that is sufficient to ignite the motor. However that optimization remains low on our priority list.
  • We have tweaked the pyro-valve design. We are now up to version 3. See the design page for more details.
  • We'd really like to get away from PVC as a fuel. However we don't have the time to develop PBAN grains. Plan for this test is to use a 12" piece of 3" ABS pipe as the fuel grain.
  • We have worked with Mike to machine the injector and forward bulkheads for easier assembly and disassembly.

Weights and Measures

  • We will run off Mike's 15 lb Nitrous tank for this test. Tank currently holds 13.9 lbs. Ullage is estimated at 2.5 lb.
  • Pyro-valve material was measured at 0.43" thick on both valves.
  • Fuel grains were made by cutting pipe stock to 11.75" long (all 3 grains). Grains were shimmed with felt stick-ons designed to make furniture not mar hardwood floor.
    • ABS #1 is 337.0g
    • ABS #2 is 339.3g
    • PVC is 454.2g
  • Nitrous tank is 7.35" from forward end of injector bulkhead to aft edge for forward snap-ring groove. This gives an estimated tank volume of 1.094 liters. This is based on measured 1483 ml of volume with a 9.5" grain and a .7" thick pyro-valve. We are using a 11.75" grain and a .7" valve.
  • Simulation predicts a 2 second burn, K-1000.


Cold Nitrous Flow

Pyro-valve failure during test 8.

Test 8

Began loading nitrous at 11:30. Filled until we were venting liquid. While waiting for the tank to chill the pyro-valve popped, dumping all of the nitrous.

The pyro-valve material apparently hit the forward edge of the nozzle, chipping a chunk out of the nozzle. This damage appears to be mostly cosmetic.

A 12 second movie of test 8 is available here (4 MB download size).