Critical analysis of helium gas bottle inflation systems for rocket engine fuel tanks

Abstract

As is known, the pressurization systems (PS) of the fuel tanks of rocket propulsion units (RPU) are intended to provide the necessary pressures of fuel components at the entrances to the engines and intake devices (for their continuous operation). Their second purpose is to create the required gas pressure levels in thin-walled fuel tanks for their stability on the active flight trajectory of the carrier rocket (CR) [1, 2].

PS are part of the pneumatic-hydraulic fuel supply systems (PHFSS). They are the most expensive, complex, and scientifically intensive parts of the CR [3] after the liquid rocket engines (LRE).

Currently, liquid oxygen and hydrocarbon fuel (RG-1, T-1, methane, synthetic, hereinafter referred to as gas) are the most widely used and planned for use in the near future as RRE fuels. Examples include the RRE CRs "Zenit," "Cyclone-4M," "Mayak" (Ukraine), Antares (USA and Ukraine), Atlas-V, Falcon 9 (USA), "Changzheng-7" and "Changzheng-9" (China), KSLV-I, KSLV-II (South Korea), and others.

For the pressurization of the fuel tanks of all the listed modern RPUs on the specified fuel components, helium has found the widest application as a working fluid [4]. Prior to launching the RPU, special balloons of the flight pressurization system are filled with cooled helium (for example, on the "Zenit" CR, ~113K). These balloons are placed in the fuel tanks of modern RPUs with liquid oxygen. Helium is used for pre-launch tank pressurization.

It is necessary to note such an interesting fact, which requires an explanation. All liquid intercontinental ballistic missiles of the Soviet Union, the USA, and China, even of the latest generation, did not use helium, not even for the operation of automation units. Most CRs for space missions also managed without helium. Generator, steam, mixed, and "chemical" PS were widely used [5].