Vast:
Nitrous Blowdown Simulation
Embedded Files
Introduction
Introduction
Another project I had at Vast in the summer of 2023 was to analyze nitrous blowdown to characterize flow for thruster development. Nitrous is becoming a popular choice as a new green propellant in both the commercial industry and amateur rocketry, because of its safety, storability, and self-pressurizing properties. In a sealed container at room temperature, nitrous exists as both a liquid and high-pressure gas. This means that a tank filled with nitrous can provide a continuous high-pressure oxidizer while being emptied.
*Due to NDA, I can only include a limited amount of technical details
Methods
Methods
To analyze nitrous blowdown, I created a Python simulation. This model took in initial nitrous mass, tank volume, and temperature and gave the mass flow rate, nitrous vapor and liquid mass, and pressure as a function of time. To determine all of these values, an iterative approach was taken where for each incremental time step, a small mass of nitrous left the tank. This in turn freed up space in the tank, which reduced the pressure of the nitrous vapor below its natural vapor pressure at a certain temperature. In response, a small amount of nitrous vaporizes to bring the vapor (tank) pressure back up. However, since boiling is an endothermic process, that small amount of nitrous takes heat away from the larger liquid mass of nitrous, which leads to the overall temperature of the tank decreasing. This temperature decrease in turn decreases the nitrous vapor pressure and thus tank pressure and performance.
To increase the fidelity of this model, heat transfer through conduction and convection was calculated. Additionally, the ideal gas law with a compressibility factor and the latent heat of vaporization were used.
Results
Results
My nitrous blowdown model was used to validate the Impulse Space nitrous propulsion and feed system for the Haven-1. One specific issue that came up during our discussions was the use of heaters to increase the pressure of nitrous past the supercritical point. There were concerns about the overpressurization of tanks, but I determined that was not possible.
In addition, I aided in the testing campaign of Vast's own nitrous thruster using our test stand, pressure transducers, flowmeters, thermocouples, and load cells.
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