Icarus is BURPG's latest flight vehicle; the rocket uses a nitrous oxide/IPA bipropellant rocket engine called Iron Lotus. This engine puts out 2500 lbf of thrust and is currently the most powerful liquid bipropellant rocket engine developed by a university in the United States. 

Over this summer, I was tasked with designing a thrust structure that would not only withstand the 2500 lbf of thrust generated during flight but also survive the 3000 lbf startup transient.  Furthermore, this thrust structure must also be relatively cheap, easy to manufacture, and easy to integrate with other systems. I was also tasked with integrating the fluid system in the thrust structure to adapt a ground-configurated ox plenum for flight.

Early designs consisted of a "thrust plate and rods" system instead of a clevis and pin system. A clevis and pin system would require more machining and would cost more than the plate and rods design.

To increase increase torsion resistance, I created stiffeners that would be placed at different locations on the rods. One of the stiffeners was turned into a transition stage to adapt from a 8" OD to a 9.25" of the thrust plate. 

The thrust plate is a 3/8" plate made out of 6061 aluminum that handles the expected forces and mounts the engine to the rest of the rocket. There are also holes drilled out to make room for instrumentation and fluid routing. 

Unfortunately, analysis revealed that this design concept was fundamentally flawed. The structure was very susceptible to buckling and it was unconstrained in 2 DOF.  Furthermore, it was not very resistant to twisting caused by moments on the fins. 

Scrapping the previous design, I decided to proceed with a  clevis and pin design. Usually in clevis and pin designs, all the beams start at a central point and protrude outwards so it can transfer the axial force of the engine thrust from the central axis to the fuselage of the vehicle. 

However, due to space constraints, this design was not possible. Thus, I had to offset the beams a certain distance away from the central axis. Although this design was not as structural efficient as I wanted, I solved for the deflection of the thrust plate and conducted a buckling analysis of the thrust beams and determined that this structure could withstand all the anticipated axial loads.

To withstand twisting forces generated by the fins, the fin can would mount to an updated transition stage. The transition stage was now thicker and would withstand both the axial loads transferred from the engine to the thrust beams and the twisting forces from the fins. 

A major issue that arose during the design of the thrust structure was the routing of the fluid system. On the oxidizer side, there is a raceway that extended from the outside of the vehicle to deliver the oxidizer. On the fuel side, there is a fuel inlet that was designed specifically for ground operations that needed to be adapted for flight. In addition, there needed to be space considerations for the purge lines and pilot lines for the pneumatic valves. 

Over the course of three months, several routing configurations were tried which included flipping a pneumatic ball valve sideways and creating strange looking U-bends with pipe fittings. Eventually, I decided that trying to recess the fuel side of the fluid system inside the rocket was a fake requirement.

 First, I decided to route the piping for the fuel side outside of the vehicle using a small number of raceways. Next, I used a series of tee-connectors to split the flow from one stream to four individual streams. After completing a structural analysis of the system and creating a manufacturing plan, I presented the design with a team at a critical design review.