Testing

Hydrostatic Testing

To verify that the rocket will not explode while the SystemsGo team fills the oxidizer tank, they require a hydrostatic test to 1200 psi (1.5 safety factor of 800 psi). For us, that meant heading over to MMI to have them fill the tank with pressurized water and let it sit for thirty minutes. Once we got rid of all of the sharp bends in the nylon tubing and tightened a few of the NPT threads, it worked perfectly.

The boys chillin' after successfully testing a very strong tube.

Injector Testing

Like we said in the propulsion section, we tried out a new kind of injector this year - a hollow cone spray injector instead of the impinging ones that we have always used in the past. The spray was pretty easy to test just by hooking it up to a power washer, and we found very good atomization with a spray angle around 40º.

You can read more about the injector spray here

Nylon Tubing Testing

To test the strength of the nylon tubing that we used in the rocket's fill system, we did a few simple hydrotests with a handpump from Rice Hydro. We used adapters to attach the outlet hose of the pump to our injector, then connected the nylon tubing to the DOT fittings on the injectors, and another injector, adapter, and NPT plug were attached to the opposite end of the tubing. Using a nearly complete system for hydrotesting meant that we tested the nylon tubing, NPT fittings, and DOT fittings at the same time. After repeated testing, we found that the originally-planned nylon tubing was too weak to handle our expected pressures (i.e. the rocket would not have worked), bursting at around 600 psi. As a result, thicker nylon tubing was purchased (3/8" OD 1/2" ID) that could withstand the high pressure. Read more about the testing of the injectors and tubing here.

This tube burst at 600 psi, so we had to get a thicker style of nylon tubing.

Ablative Testing

On either end of the fuel grain are the pre and post-combustion chambers, designed to improve atomization and combustion efficiency respectively. However, the air is still quite hot there, so we have an ablative mixture to prevent the combustion from burning through our phenolic.

Building off of Melanie Markham's experiments from a previous Goddard team, we tested different proportions of a mixture of Epsom salt, Kevlar fiber, and epoxy. When we burned a .45” puck with an oxyacetylene torch for 25 seconds, only 5ish percent ablated. Those test results held up for the flight, where the 1/2" wall looked almost unscathed (apart from the black layer where a teeny bit burnt off).

Detailed diagrams of the force path that unfortunately does not include the knot that broke.

Recovery Testing

Recovery tested the amount of black powder required to blow the nose cone off and release the parachute, which ended up being about 3g. Unfortunately, we were not able to test the snatch force, the opening force of the parachute, or the strength of the knot of nylon tube. One of those things ultimately caused the recovery to fail (probably the cord strength).

Injector Spray Cones

A cool picture of the excess water being pressured out of the ox tank after the hydro test. This shows the impressive atomization of the vortex injectors

Test Fuel Burn Setup

Josh and Kyle set up the new test stand to do a test burn of a small-scale fuel grain. This process utilizes a load cell to measure the force produced from the burning of oxygen and HTPB/ABS fuels

Burn test of the U/C burn valve

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The Nylon tubing is attached to an injector and an APCP piece is wrapped around the base. At the base of this is a small pyrodex pellet used for ignition of the solid fuel. This test was to ensure that the nylon tubing burned away. It did.