In rocketry, structural engineers design the “bones and muscles” that create the form and shape of a rocket and, in order to successfully do so, they usually work in cooperation with an aerodynamics team. Structural engineers need to understand and calculate the weight, strength, and rigidity of the rocket that is going to be manufactured.
A rocket is divided into two main parts, the airframe and the internal components. The first one consists of the nose cone, fins, and rocket body, while the latter of the motor bay, the Payload, Avionics, Recovery, and GPS Bay.
To begin with, before proceeding with the final HYPERION model, Rocketry’s members had already designed, manufactured and tested in flight 2 other model rockets, Hyperion 1 and Hyperion 2, which were 1:3 scale models of HYPERION. These two models provided considerable experience in designing and manufacturing model rockets. With this experience in mind, and after extended research to gather extra information and data needed, the team proceeded with the final HYPERION model.
The designing process of the last HYPERION model started back in February 2019 and lasted for about three months. During that period, the Structural sub-system had to design, first of all, the components of the rocket in a 3D CAD software, SOLIDWORKS. The next steps included the materials’ selection, the model’s weight estimation and the manufacturing method of the structural components. The materials that were chosen were composite materials, for the airframe, and aluminum 6061 – T6, for all the internal parts. The reason the sub-system used composite materials was that they provide high strength for low weight. Additionally, static analyses were conducted for these components under all the imposed loads during a flight, to ensure the rigidity of the vehicle, using the software of BETA CAE Systems, ANSA and META.
HYPERION’s rocket airframe consists of its tube, fins, and nose cone. All these three components were designed by Rocketry’s Structural sub-system and two of them, the fins and the nosecone, were also manufactured by the members of this sub-system in our laboratory.
HYPERION’s fins have a core of polyurethane foam, which is then laminated with 2 layers of carbon fiber. Then, a third carbon fiber layer is used to connect the fins with the rocket’s body, using the tip-to-tip method, thus creating a monolithic connection. For the lamination process, the sub-system used the vacuum resin infusion method.
Moving on to the nose cone, it is made in-house from fiberglass and, for its structure, the sub-system followed the vacuum resin infusion method, this time using two female MDF molds.
The airframe tube of the rocket is divided into two parts, which are connected with an aluminum joint. The airframe tube is made of eight layers of carbon fiber, oriented in that way in order to withstand the compressive and tensile loads of the motor and the parachute deployment.
Inside HYPERION’s body, every component is secured on aluminum bulkheads, which are attached to the airframe. The two major bulkheads that require attention in the design are the motor bulkhead and the recovery bulkhead. The motor bulkhead is where the rocket motor is secured and receives the thrust of the motor and then takes the load to the airframe. On the other hand, the recovery bulkhead has to withstand the loads that are produced during the parachute deployment.
In terms of numbers, the airframe tube is about two meters long and has an interior diameter of 12.5 cm. Both the tube and the motor bulkhead are designed to withstand a max thrust of 2400N and the recovery bulkhead a force of 1700N.
Our team has already designed a new high power rocket PEGASUS. As we finished the design process of HYPERION, we were ready to continue with PEGASUS, which is an one stage rocket with a total length equal to 2.5 meters and weight of 17 kilograms. Three carbon fiber tubes were used in order to achieve an easier assembly of the rocket as well as the internal components are mainly made out of Al6061-T6. The outer diameter of the tubes is 149mm and the thickness is 2mm. Four fins of 3.5mm thickness were selected by the Aerodynamics sub-system. The fins are about to be attached on the lower tube using the tip-to-tip method, a process that was applied in the HYPERION rocket.
The nosecone will be manufactured by fiberglass, which, in comparison to carbon fiber, offers lower cost and greater capability of radio waves emission, thus enabling the use of GPS. The vacuum resin infusion method will be applied for its construction, using MDF female molds. At the top of the nosecone a metal nosecone tip will be places, as there is a high concentration of external loads.
Our team, due to COVID-19, decided not to proceed to the construction of Pegasus, although it is a significant step for the design process, as we had the opportunity to correct design problems that occurred during the construction of HYPERION.