Overview
The feed system is responsible for delivering the propellants from their respective storage tanks to the engine. On the oxygen side, a manual valve is opened, which allows oxygen from the high-pressure tank to pass through a pressure regulator. Once the test engineers retreat to a safe distance, a solenoid valve is remotely opened to allow the oxygen to flow to the engine. A check valve, directly upstream of the injector, prevents backflow. Since the methanol fuel is liquid, nitrogen is used to create the pressure that forces methanol through the system. The nitrogen passes through a regulator, then through a check valve, and then flows into the fuel tank. The fuel then flows through a regulator and another remotely controlled solenoid valve. The fuel line also contains a manual shutoff valve and a check valve. A nitrogen line that splits off before the fuel tank and bypasses the solenoid valve. This is a purge line that will be used to clear out any residual propellants at the conclusion of the test fire. This line can also be used in the event of a failure that requires the test to be aborted.
Tanks
All three tanks are custom manufactured and are designed to handle pressures multiple times higher than those that will be used for RL-36. The high-pressure nitrogen tank and the oxygen tank are composites. The methanol tank is steel.
Valves
The valves used for RL-36 come from multiple manufacturers. This is not ideal; however, due to the Launch Initiative’s budget, low cost is a priority. Most of the valves were purchased years ago for a hybrid engine project, and they are still in good condition. The decision to use already-purchased saves thousands of dollars. Fortunately, because of their size and pressure ratings, these valves can be reused for feed systems of engines that are up to 100 times more powerful than RL-36. Most valves are manufactured by Swagelok, but other manufacturers include McMaster-Carr, Jamesbury, and Matheson.
The fuel side contains eight valves, and the oxygen side contains four. A pressure loss occurs across each valve. These losses are accounted for when determining tank pressurization. The fuel side consists of redundant solenoid valves downstream of the fuel tank. This way, if one of the valves fails to remain closed before testing or remains open after the test is complete, fuel will still be prevented from flowing through the injector and burning up in the combustion chamber. A check valve is placed upstream of each of the three tanks to ensure that fluid from one tank does not make its way into one of the other tanks. Each propellant line consists of a manual shutoff valve in case the solenoid valves fail when the system is in storage in the days leading up to a test. These valves are opened right before a test begins and are closed after the test is over.
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