Static test of N2O liquid / solid hybrid rocket motor. December-2011
There data below were taken from a static test of a N2O/PVC hybrid rocket motor.
PRV. The active pressure release valve (PRV) worked, enabling
the hybrid rocket motor to work correctly at a blustery 30 degF
Igniter In previous tests a section of thermalite cord was
glued onto a slice of APCP propellant. I believe the glue inhibited
ignition of the thermalite. (strange) This time, a small hole was cut
through the APCP slug and the thermalite was jammed into the hole with no
glue. Ignition worked fine.
Horizontal test stand A new test stand was built. See pictures
Despite the tilted setup (due to simple laziness), the test stand
was solid and the horizontal orientation did not seem to affect the
results. This test stand weighs much less than the vertical test stand
used in previous tests, and it is simpler to setup.
Chamber pressure In the past, the sensor connected to the
combustion chamber would routinely burn-up ($$$). A 6 inch standoff was
added between the combustion chamber and its sensor. In addition a T and a
plug were put in-line so a 1/2" layer of oil could be added to protect the
sensor. This seemed to work.
18" length x 3" diameter N2O tank (5 lbs)
18" length x 2.75" OD x 2.25" ID PVC grain
Graphite nozzle, 1" throat, 15 degree egress, 60 degree ingress
Tank pressure actively regulated to 400 PSI
Target size baby "M"
Unfortunately the connector to the load cell amplifier/conditioner was
broken. The connection allowed a sane impedance reading during setup, but
no data were received during the test.
Approximately 1 pound of PVC burned and 5 pounds of N2O. Most likely the
motor was a baby "M."
Internal chamber pressure was approximately 100 PSI which is too low. A
smaller nozzle throat will raise the pressure. I see no signs of
combustion instability even at this low pressure.
Small wisps of vapor can be seen from the bottom of the N2O tank. One of
the fittings must have been loose.
Test Stand Output Test 1
(notice the orange wires crossing behind the motor in lower right. They
aren't there anymore!)