Kiwinning

Kiwi pulled off another successful static fire on Saturday, February 23. We had originally planned to fire three grains, but actually used only 10% oxamide, due to a combination of grain curing problems and an intense sandstorm. Our data acquisition system performed well again, including three pressure transducers (two at the head end and one at the aft end), load cell, and thermocouple.

We had a much smaller crew of RPLers at this firing, due to midterms - about 12 people in all. One benefit of this was that more people got experience preparing the motor.

The main way in which this firing was different from the previous series (besides the propellant composition) was the nozzle and forward motor bulkhead. We remade the nozzle out of steel, with a shorter graphite insert. Both the nozzle and the new aluminum bulkhead had face O-ring grooves to seal a leak path for combustion gases and thereby protect the inside of the motor case.

The nozzle, showing the face O-ring grooves and pressure transducer stems.
Integration went smoothly, apart from having to apply a little more force than usual to compress the motor stack longitudinally due to the face O-rings. After Kiwi was on the stand, the DAQ equipment was hooked up:

Tim and John working on DAQ.

The beginning of the sandstorm.
The wind had been building up during the day, and by 1400 it was quite strong. We armed the cameras and everyone packed into the blockhouse. The head-end igniter, made from an Estes motor, did light on the first try, but did not burn long or hot enough to ignite the grain. (We're currently experimenting with other materials for Texas Two Step's igniter.) We installed a composite igniter instead, which lit the grain after some chuffing. The burn was very long, about 13 seconds, as expected from using so much oxamide. The sandstorm was very harsh by that point, as bad as any at Black Rock, so we packed up as quickly as possible.





Post-processing of the data occurred during the next several days. The results were similar to what we predicted in simulations. This graph shows the thrust profiles for all four Kiwi firings this semester:


As the nozzle throat on this firing was designed for a higher burning rate, the chamber pressure stayed low, around 300 psi, so it would be possible to get higher performance by using a throat designed around this propellant's burning rate.

Kiwi has now fired a grand total of five times, demonstrating the robustness of our composite case technology. It will not be used again this semester; we're fully involved in preparations for the launch of Texas Two Step on April 27, as well as firing Tim's GOX/GH2 aerospike the weekend after. We might slip in something else before finals ... stay tuned.