Accuracy and repeatability in valve leak test stands are key to space exploration

Alicat has the opportunity to work with all kinds of engineers and scientists pushing the boundaries of science and technology in aerospace applications. Projects include improving pilot safety, putting satellites into space, launching rockets, and much more.

Our goal is to understand each customer’s distinct application requirements and find the perfect mass flow or pressure solution to keep important projects moving quickly and smoothly. In this article, we discuss an application where a customer-developed leak test stands for rocket engines.

Challenge: Valve leak test stands and characterization for rocket engines

Leak testing takes place in a lab environment on Earth, designed to simulate conditions in space. These test stands must detect even the smallest of leak rates, requiring high-accuracy mass flow and pressure instrumentation.

One challenge encountered when selecting test stand equipment is the high operating pressures. Because testing rockets requires such high operating pressures, it can be challenging to find suitable equipment.

A standard pressure controller is unlikely to meet these pressure requirements. Dome-loaded regulators can handle high pressures and high flow rates and are therefore often used to control pressure in testing rocket components. However, these dome-loaded regulators experience significant hysteresis which can result in a non-repeatable process.

Solution: Repeatable pressure control and near-atmospheric flow measurement

To avoid hysteresis and guarantee repeatability, the team used high-pressure-rated dual valve pressure controllers (PCDs). These repeatably control pressures up to 3,000 PSI with a proportional control valve optimized using onboard PID tuning. The pressure controllers were additionally paired with Whisper low pressure drop flow meters.

The PCD was used to control pressure at the inlet port of the valve under test, and the flow meter was installed downstream to measure the leak rate through the valve. This setup enabled the detection of even the smallest of leaks at near-atmospheric pressures.

Pre-loaded multi-gas calibrations allowed for easy switching between the two most common leak-testing gases – nitrogen and helium – with no change in accuracy or need for recalibration. Finally, all Alicat pressure and mass flow devices were configured with AS5202 ports for easy system integration.

More aerospace projects
  • Ensuring the oxygen masks in military and commercial airplanes flow the correct amount of gas and meet safety regulations – bidirectional mass flow controllers simulate human breathing while monitoring system pressure.
  • Flowing water to support and monitor cooling systems in pressure suits and propulsion systems – liquid flow instruments were customized to be lightweight and compatible with space suits.
  • Controlling the lift of high-altitude balloons used in experiments to study and understand weather patterns and various aspects of the upper atmosphere – mass flow meters measure hydrogen or helium used to fill the balloon.
  • Assisting with the pitch, roll, and yaw on a rocket launch delivering an astronomical telescope satellite – pressure controllers with high-resolution control and smooth ramping aim the scope and prevent image blurring.
  • Testing instrument performance in harsh Martian conditions – mass flow and pressure controllers replicate the atmosphere on Mars.

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