Hamza Khan

hkhanbox@gmail.com

Theseus Flight Vehicle

  • Built, tested, and iterated the fluids system for a bi-propellant LOx/Kero rocket that produced 650 pounds of thrust at launch. First launch for the CSULB Beach Launch Team since 2019.

  • Validated system performance ahead of launch by performing a hot-fire, resulting in 525 lbs of thrust. 

  • Ensured fluid system could survive cryogenic conditions by performing cryo flows through the system.

  • Calculated the systems flow coefficent utilizing empirical data collected during water flows, and theoretical data using the Darcy-Weisbach equation. 

Skills Gained: 

  • Handling of Kerosene, Liquid Oxygen, and Nitrogen
  • Proficiency in fluid system routing, assembly with Swagelok, AN, NPT, and ORB fittings
  • Precision cleaning methods for oxygen and fuel sensitive hardware
  • Leak testing, hydrostatic testing, flow characterization, and cryogenic operations

 

Building Theseus

The fluid system of Theseus was dictated by the engine that was being used, in this case, the Rocketdyne LR-101. The fluid system's job is to make sure the engine inlet is seeing a constant pressure, which was done via spring and dome regulators. The system also had various solenoid valves so that pressure could be vented from the system at any point. Also part of the system includes various ball valves for propellant loading operations; Fuel Fill, Fuel Spill, LOx Fill, and LOx Spill. The main valves are also ball valves but they are operated through a pneumatic setup connecting to a linear actuator. 

 

The fluid system itself was constructed with various tubing that required special tools. The pipes were all routed via a tube bender and some pre-stressing. The pipes were either -4 or -8 diameter and utilizede various fittings. AN and Swagelok fittings were predominantly used, as well as some NPTs and ORBs. The former were used for the piping and the latter were used for some of the actual instruments.

To make sure that the fluid system performs nominally during launc, a rigorous test campaign has to occur leading up to the launch.

  1. Water Flow
  2. Cryo Flow
  3. Hot Fire
Testing Theseus
Water Flow

It is incredibly important that the engine inlet sees a constant pressure through all 9 seconds of the burn. To maintain that constant pressure, the change in pressure through the system has to be found. As fluid travels, it loses pressure. 

 

To calculate the change in pressure (dP), the flow coefficent (Cv) of the system is found. The flow coefficent tells us how well the system allows for fluid flow and it is based mostly on the geomtry of the system. Water is flown through each side of the rocket at different pressures. This is to make sure the data is accurate, as the varying pressures should not have an effect on the Cv. This Cv can then be backplugged into the equation to find the dP of your fluid, provided you know its specifc gravity. This dP is then added to your inital tank pressures to account for the loss as the fluid flows. 

 

Empirical data from the water flow as well as theoretical data found from using the Darcy-Weisbach equation on the system showed that the LOX tank required 485 psig and the fuel tank required 535 psig. 

 

Cryo Flow

Ahead of any firing, the system must be validated under cryogenic conditions. This is done via a cryo flow, which is flowing a cyrogenic fluid through the LOx side. This let's the system be tested in conditions similar to reality. Once the system passes cryo flow, then an actual hot fire may happen. The Pass/No Pass requirements vary with systems but for Theseus there had to be no leaks and no damage. While there were some icing problems and some pipes had to be remade, the cryo flow was mostlty successful. For redundancy it was performed again, after the fixes, passing with flying colors.

Hot Fire

The final, and arguably, most important test ahead of launch is the actual hot fire of the fluid system. This is to verify the fluid system works as designed and actually produces thrust. The Theseus Flight Vehicle was hot fired on December 1st, 2025 and produced a maximum thrust of 525 lbf. This was lower than what the system was designed for but still a huge step forward. 

 

The aforementioned icing problems changed the calibration on the regulators and provided less pressure to the engine. However, it was still at a  consant pressure as a stable 525 lbf of thrust was produced.

Launch

The Theseus Flight Vehicle ultimately launched on April 19th, 2026. A series of anomalies occured during flight, resulting in an apogee of about 4000 feet.

 

The biggest problem was that the vehicle simply didn't have enough LOx in it. Lox loading operations were rushed and there was a large time delay between Lox loading and launch. Another issue discovered later was a blown O-ring in the LOx manifold on the engine. This resulted in a loss of pressure at the LOx inlet of the engine and a fuel rich burn. Combined with the lack of enough LOx, the engine only fired for 3 seconds. This is what ultimately caused the sub-optimal apogee. 

 

It should be mentioned however, that upon ignition, the engine produced 650 pounds of thrust. A big improvement from the hot fire.