gh GASES IN ROCKET PROPELLANT: INERT GASES DO NOT MEAN INVISIBLE ONES

Researchers from the Moscow “Khimavtomatika” Scientific Production Association have developed an original method for identifying the nitrogen and helium concentration in rocket propellant. Instead of traditional gas chromatography, the authors suggest a completely different approach, which is based on measuring physical characteristics not of the propellant itself but of its vapor. Or more precisely – of its balanced gas-vapor phase.

It should be noted that it is very difficult to determine both nitrogen and helium – the chemically inert and therefore “hardly perceptible” substances no matter where, and particularly in the rocket propellant, the components of which (for example, asymmetrical dimethyl hydrazine), are on the contrary, extremely reactive. This is necessary, because these gases that partly get into rocket propellant when the engine is being filled up with fuel (with their help the fuel is “pressure-forced” into the fuel tank), can influence the engine performance. Therefore, their content in the fuel should be strongly regulated.

The traditional approach tells to use gas chromatography – the method is not cheap, it is rather cumbersome and requires working in laboratory conditions. It means that the fuel sample (which is highly chemically aggressive) should be delivered to the laboratory, and then the sample or a specimen of balanced vapor-gas mixture above it should be introduced into the gas chromatograph, where the components are first segregated in a special post, and then the contents of each is measured. It is obvious that the posts have a short service life when handling such aggressive analyzable substances, and the posts have to be regenerated after each determination. Moreover, preparation of a balanced vapor-gas mixture sample in the classical variant is a lengthy procedure, at the beginning of it is necessary to perform the fuel component sample extraction into a container where the air has been preliminary pumped out.

The method developed by the specialists of the “Khimavtomatika” Scientific Production Association allows to avoid all these complications because it is based rather not on chemical but on physical and mathematical analysis of the vapor-gas mixture above fuel which is in equilibrium with fuel components.

The essence is that in the gas-liquid equilibrium system, the gas quantity above the liquid (in the vapor-gas mixture) is in proportion to the quantity of gas dissolved in this liquid. And the vapor-gas mixture thermal conductivity will also depend on its content, i.e. on components ratio, thermal conductivities of which is naturally different. The authors have made use of that. They have deduced an equations set, which allows to calculate (based on measurable parameters - temperature, pressure and thermal conductivity) the concentration of each of the components first of the gas phase, and then of the liquid phase in the sample, and in the long un to determine the nitrogen and helium concentration in rocket propellant, without splitting it into components.

It is now clear that the nitrogen and helium content in the liquid rocket propellant components can be controlled not only in the laboratory but directly in the course filling the samples of space-system machinery, at that, this can be done efficiently, safely and more importantly automatically. The only thing remaining to be done is to produce a respective device. The foundations for its establishment have been laid thanks to developments by researchers’ from the “Khimavtomatika” Scientific Production Association.

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