Airframe Time!

Here’s the dilemma. We need the strongest, lightest skeleton possible for our rocket. The obvious choice for material is aerospace grade aluminum. (6061-T6, duh.) We also need to cut a ton of pieces, and need them done fast. The usual way to do that is with a CNC milling machine, but that can take a while and be very expensive. Also, when you cut a piece of metal with a saw or a milling machine, the metal heats up causing it to anneal and weaken. So what’s the solution?

Waterjet cutting is the solution!! The helpful staff at New Jersey Waterjet were able to take our CAD files and produce 30 perfectly-cut parts in just under a week.

Waterjet cutting uses a high pressure stream of water and abrasive sand to cut through nearly anything. In addition to being fast and precise, waterjet cutting actively cools the parts, preventing them from becoming annealed.

These parts will hold together the whole rocket, so it’s a good thing they’re strong.

Senior Design

Thursdays are a great reminder that this project is rooted in Stevens Senior Design.

Thursday mornings, the team gathers at 11:00am in TG-404-I. “Technogenesis” teaches business aspects co-curricular to the graduating class’s engineering projects. The professor, Sandra Clavijo, leads discussions ranging from market share development to pitch delivery.

Then, we retreat into our cave at CPR HQ to work for hours straight on the most challenging segments of the rocket. Typically.

Once every couple of weeks, we take an hour or two from our Thursday schedules to meet with our Technical Advisory Group (TAG). The day-to-day attendance changes, but TAG members include Stevens professors, industry professionals, and esteemed researchers. Yesterday was one such day.

As an added bonus, yesterday’s TAG meeting doubled as our team’s satisfaction of the Mechanical Engineering “Phase Four” report. Phase Four requires information on alpha prototyping and a testing plan for the integrated system.

The eight members of the team presented 26 slides to the TAG, followed by a period of questions and discussion on various subsystems designs. Most important were the progress made on the circuitry systems and the prototyping being done by our partner companies.

The TAG seemed pleased, which makes us happy, too. Actionable items included sourcing more wire rope for our static fire test and running another heat flow simulation on our injector/engine assembly.

DIY Pressure Test

The tests are evolving! Friday afternoon found Nate, Will, and Abe in the Griffith Lab doing another round of tests on the injector. Despite an injector print with no top and a few construction workers milling about, the test was a success.

The injector hung from a plywood-and-8020 cantilever held together by that giant C clamp. A machined panel of acrylic lay flush to the misprinted top to prevent backspray. Pressurized water ran from a 5-gallon jug (located in the makeshift closet in the back corner) through the tubes and past the acrylic shield. A barrel borrowed from the teaching lab caught the outlet water, and our camera sat a safe 20 feet away to prove we were there.

To avoid the possibility of our water jug exploding, a computer regulated the pressure in the hose and that information was screen-cast to Abe. Will manned the pump and Nathan watched the camera.

When the valves were opened and the pump switched on, Abe stepped us through pressure testing up to 44 psi. The water came whooshing, we only got a little wet, and the injector performed wonderfully.

Chalk this test up as a victory — Nathan analyzed the video file and found appropriate atomization. All without causing a big boom and a gush of water from our tank! After sufficient congratulations, we tore down and cleaned the lab up for classes and other senior design teams over the weekend.

Stay tuned for more exciting injector updates!

Designing a Circuit Board

Over the past few weeks, we have been developing our first version of our Printed Circuit Board (PCB). We chose to use Eagle, a PCB Design Software, as it had an easy learning curve as well as an easily attainable educational license. In Eagle, we had to first design and import all the different electronic components that were going to be used into the rocket. We then had to figure out the correct electrical requirements for each component and how to link up each one correctly to the entire system.

The next step was to design the PCB layout itself. We started off with a circular design so it would fit into the rocket base. We then traced the connections so that they didn’t interfere with each other or cross each other. The blue and red lines below show different “levels” of connection. The red traces are the top copper connections, while the blue traces are the bottom copper connections.

We’ve spent a lot of time on it so far, but this is still only our initial design. It still needs to go under testing and multiple iterations to be ready for launch day.