Our solid propulsion team has been working to create and develop our own solid APCP rocket motor. Specifically, we have been reverse engineering the commercial Cessaroni M1300 motor, as we have modeled the performance of this motor according to our rocket specifications. The APCP motor fits within the competition constraints, is a powerful solid propellant, and is proven as a solid motor by NASA. We also chose the cross symbol as the grain geometry due to the thrust curve and immediate power required to get off the ground initially. We will be ordering our aluminum casing from a commercial site, which will also provide heat shielding and case parts for our motor. We decided to purchase our motor casing commercially due to the fact that creating the propellant is a complex enough task, and creating our own case and case parts would add a drastic amount of unnecessary costs, time, and complexity to our project. We have also put in efforts to locating a test site within the WSU lab spaces and also with the local fire department. In addition, we will be strongly focusing on creating processes and safety during our testing. There has been great progress and work done on our team, as we are trying to overcome one of the greatest innovations for this year’s competition. Here is a breakdown of the progress that we have made.

January: We received our materials for motor manufacturing. This included the ammonium perchlorate, aluminum powder, and iron oxide powder. From there, we went ahead and created our first batch of motors to test. Our goals for the initial tests were to successfully ignite a motor without an explosion. Although we took extra safety precautions, we were still not able to successfully ignite the motor on our first test. This prompted us to go back to the drawing board and re-assess our manufacturing process as this was what we suspected to be the flaw in our motor. By the end of the month, we had created a new batch of motors, modified our manufacturing process, coordinated with the Pullman Fire Department for a test site, and created an updated safety checklist. By the time we tested on January 31st, it was a huge success and we were able to successfully launch all 10 specimens that day. Here are some images of the test site and specimens that day:

Here’s a good picture of the launch site. We used the dirt mound that our team member is standing on in the right side of the picture. This was a good, isolated section that enabled us to be far enough away from the launch.

Here is a simple image of our test stand. It essentially works by inserting an igniter down the circular grain geometry. The ignitor is connected to two alligator clips that lead to our fuse box. The motor is clamped down to a 3D printed mount (the red object) and slid down the centering rods. Once we have equipped ourselves with safety gear, we went a head and ignited the motor.

Here’s a great image of the side profile on our launch set up and our motor once it has been ignited!

February: For this previous month, we went ahead and created a larger scale motor to see the viability of scaling up with our manufacturing process. Our tests were all successful, and we were able to take some learning points away from these tests such as additional safety precautions and further knowledge on grain geometry. Later that month, we also started the process of requesting a data acquisition system to collect data on our motor. The rest of the month was filled with modifications of the data acquisition process and adjustments to our APCP motor composition.

Some of our recent accomplishments include a modified test stand, finalization of our data acquisition process, and the beginning the process of manufacturing out nozzle for more detailed tests.

Aerodynamics has been working on manufacturing the fuselage tube for the past couple of weeks. A mandrel was created to hold the body tube for the layup process. They started out with a single layer of carbon fiber and vacuum bagged it. The result- fantastic layup, no wrinkles, very nice finish.

The 2nd and 3rd layups returned less than ideal results unfortunately. 3-4 layers of CF were used for each. Each of the layers had epoxy run through them and pressed out(similar to a prepreg) before being placed on the aluminum tube. This would allow for less movement of each layer when placed onto the tube. The idea was that this would help reducing wrinkles. Each of the layups were placed into a vacuum bag and into the oven to cure. This step seemed to create the most wrinkles. Even though breather was placed around the tube, there were areas that bunched up when the vacuum sucked out all of the air. Thus, they resulted in veiny tubes. Although these can be sanded down, the process reduces the strength of the tube.

The 4th test was great! The team had a near perfect layup. What changed?! They didn’t use the vacuum bag during the curing process. Instead, after they were done applying epoxy, peel ply was wrapped around the tube and the whole tube went to cure in the oven. The ending result looked spot on. Zero wrinkles and and smooth finish. The thickness with 3 layers was close to .1″.

The Von Kármán nose cone was chosen for its low drag and high volume characteristics from subsonic to supersonic. The Von karma shape is a common nosecone profile in rockets of this size. The nosecone mold has been CNC’d and already had a test layup.

Gelcoat was applied 7 times and sanded and smoothed with each added layer. Now, its so smooth that you can practically see your reflection.

A boat tail is being used to improve the overall aerodynamic shape of the rocket and reduce the amount of drag. The boat tail is also being used to hold the motor casing in the rocket. Initially, the mold started out as turned down foam, was sanded multiple times, filled, and sanded again resulting in a clean smooth surface. The foam plug was covered in layers of fiberglass followed by a carbon fiber sleeve to add strength and match the rest of the rocket.

Fin Profile- The hexagonal airfoil was chosen for its low drag performance, durability, and simplicity. Constructed out of BirchPlywood layered with Carbon Fiber.

Electronics team has been working on the schematic for the internal electronic components consisting of two stratologgers and the ignition system. Their ignition system utilizes a magnetic switch in addition to a physical switch on the outside of the fuselage to easily and safely arm the rocket. The whole system will have a large panel/door for easy access to the electronics while on the ground/launchpad and has removable internal panels to take out the entire electronics bay for more intricate work.

Full Rocket View

Section View

Exploded View of Ground Motor Preparation

Exploded View of Apogee Separation