This project began in fall 2016 as the SOAR team started to work on a new more complicated rocket compared to the smaller simpler rockets the team had worked with in previous years. This new rocket was named Atlantis 1 and featured a Student Researched And Developed (SRAD) hybrid rocket engine and fully custom designed airframe structure. We planned to take Atlantis 1 to compete in the 2017 Intercollegiate Rocket Engineering Competition (IREC). 

My initial primary role was to design all non-aerodynamic airframe parts, which included the structural body tubes, all internal structural components, and the tooling used to make the body tubes. 

We decided that filament wound tubes would be a good option because our team has access to an industrial filament winder through a local company. However, the filament wound tubes would be the item with the longest lead time so these drawings were started first. The drawings for these parts were some of the first custom drawings I learned to make. They are shown below. 

The next design was for a part needed to provide a structural hard point to attach the parachute link to. This part would need to withstand potentially enormous forces during parachute deployment. With an assumed acceleration upper bound of 20 times gravity and an estimated rocket weight of 100kg the upper bound for deployment force was found. It was determined that an eyebolt meant for lifting applications was sufficient for linking to the parachute cord. The height of the bulkhead was determined through Solidworks FEA by varying it until a 2+ factor of safety was achieved using a structural epoxy interface between the bulkhead. This bulkhead was affixed to the inside of the rocket's upper body tube (above the rocket's nitrous oxide pressure vessel) using Loctite 9460 structural epoxy. 

These next parts depended on the finalized designs for the rocket's hybrid engine. The first part, known as the Motor Retainer Flange, was meant to provide a surface for the engine to transfer its thrust into and transfer that force to the rocket. There were three primary loading conditions of concern. First, the deformation of the flange by the motor during peak thrust. Second, bolt shearing on the flange's radial bolts. And third, damage to the carbon fiber filament wound tube that the motor is inside of during flight. The motor retainer flange dimensions were determined using Solidworks FEA and requiring a 2+ factor of safety on all loading conditions caused by the engine's estimated upper bound thrust of 1000 lbs. A Motor Retainer Bondplate was used to reinforce the carbon fiber tube against damage and was attached to the inside of the tube using structural epoxy. 

In talking with the university's machine shop, it was deemed infeasible to add a shallow (~1 degree) taper to the mandrel tube. So, an alternative method was required for removing the filament wound carbon fiber tube from the mandrel. The strategy used involved adding extra rings of carbon fiber filament on the ends (shown in picture 1 below) that would create a protruding "nub" in the final tube (nub can be faintly seen in pictures 2 and 3 below). Those nubs would allow us to establish a grip on the tube as the tube is pulled off of the mandrel. 

After the filament wound tube cured, the next step was removal. We brought the tube and mandrel to a local creamery that let us store our tube and mandrel in their freezer overnight. The next day the mandrel has shrunk in size compared to the carbon fiber, as expected. This made sliding the tube off of the mandrel orders of magnitude easier. 

As the 2017 IREC approached and the bulk of the remaining airframe structural components were being manufactured, I took on creating a manufacturing method for our rocket's fins. 

The design that was decided on was a balsa wood core wrapped in carbon fiber and a higher temperature epoxy system (Glass transition temperature of approximately 120 degrees C). The core was broken down into 3/16" layers so that a stackup of pieces could be cut with a laser cutter and glued together. There were two rods in the core to help with assembly and reinforcement. 

Some tooling was made out of MDF for the fins during curing under a vacuum. Each fin was clamped between two pieces of MDF tooling that "hugged" the shape of the fin. The idea was to have the upper and lower MDF tooling pinch the  carbon fiber together at the fin's leading and trailing edges. This was to allow for easier trimming of excess carbon fiber after curing. 

The layup started with making what is sometimes referred to as "poor man's prepreg". This involves laying down a plastic (polyethylene) sheet, followed by a layer of carbon fiber. Then, we spread epoxy over the surface of the carbon fiber until the carbon fiber is fully saturated. Another layer of plastic sheet is then placed on top, and air pockets are ejected using scrapers. The result is an easy way of drawing a predefined template and cutting already-impregnated carbon fiber pieces to the exact outline specified by the template. 

The carbon fiber cutouts are places into the MDF tooling pieces followed by the balsa wood cores. The fins are then pinched between two halves of the MDF tooling and put under vacuum and left to cure. 

The result is a fin with a reasonably (but  not perfectly) smooth outer surface, and two protruding pins allowing for easy alignment with corresponding holes in the rocket's body tube. 

The fins have structural epoxy spread along their bottom surfaces before aligning the fin's rods with the corresponding holes in the body tube. After they're aligned and oriented properly, we press down on the fin so it contacts the body tube and stays in place. Next, we spready more structural epoxy to create fillets between the fins and the body tubes. Finally, the fins are clamped inside a 3D printed jig to ensure even angular spacing during the cure.  

To address the issue of surface smoothness as well as further structural rigidity of the fins, three layers of carbon fiber are added to each of the three gaps between the three fins. Below is shown epoxy being spread onto the gap surface, followed by layers of carbon fiber. 

The result is a reasonably smooth and very strong fin can assembly. 

Below is a picture of the "fin can" (otherwise known as the "lower body tube" or "engine bay") and the "upper body tube" with the nosecone inserted. 

Upon arriving to IREC 2017 there were two large events that had all of the competing teams in one place. One was for an exhibition of the team's projects, and the second was for a photo in front of the main hangar at Spaceport America.

Below are picture work that was done at the 2017 IREC competition. The first two picture are of airframe components being installed into the body tubes in preparation for a final assembly. The second two pictures are of the hybrid rocket engine being installed into the "fin can". 

Our rocket was not able to launch this year due to a few small issues. However, our team took home 3rd place in our category of hybrids-and-liquids going to 30,000 ft altitude. This ranking was based on our high quality technical report and effective design implementation. Atlantis 1 had its first successful flight in the summer of 2017.