DanSTAR is building a rocket engine test stand to enable testing of not only engines, but also the fluid systems, electronics, software and more. The test stand will be used for the demonstration engine as well as any engines developed in the foreseeable future. To ensure it's continued feasibility, we're consciously designing it to be adaptable and ready for engines larger than the demo-engine. On top of this, we're trying to document all aspects of the project to a high standard - not only to allow new and current members of DanSTAR to understand the design choices and all the "behind the scenes" details of how everything works, but also to ensure that we can optimally reuse, modify and build upon the test stand in the future.
On top of actually gathering data about thrust, temperatures, pressures and so forth, being able to test engines will give us a lot of invaluable experience in actually firing rocket engines in practice which will be very important as we approach the SpacePort America Cup. On top of this, it will allow us to test everything that isn't the actual rocket - there are a LOT of components associated with regulating and directing all the various fluids and gasses, and probably as many sensors and control boards that need to perform flawlessly, despite being mounted to a violently vibrating structure. A good understanding of the behavior of all this infrastructure will be just as critical to success as understanding of the actual engine.
There are several important aspects of the test stand:
- Fluid system: The test stand must be able to provide pressurized isopropanol and interface with the N2O cooler to supply the engine.
- Control system: We want to learn as much as possible from our test fires. Therefore, a robust control system is needed which allows us to collect a lot of relevant data about pressures, temperatures, thrust and more. On top of this, it's very important to enable safe firing of the engines, which means the control system must be able to handle as much control functionality as possible.
- Load cell: In order to accurately understand how our engine behaves, we need a reliable load cell to measure the thrust output of the engine. This has to be chosen carefully to enable good resolution on the thrust ranges that are important to us.
- Structure: The test stand is quite a complex unit, and it needs to not only provide resistance to large amounts of thrust, but also hold a bunch of fluid tanks, pipes and electronic equipment. Holding the engine securely in itself is a challenge, since it needs to move freely in one axis to push on the load cell while also being constrained firmly in all other directions.
- Safety: A rocket engine is quite dangerous when everything goes the way it's supposed to; when that doesn't happen, it's very important to not only have a control system that will try to decrease the amount of damage done, but also a way of containing a possible explosion and the potential shrapnel