Prediction of Pressurant Mass Requirements for Axisymmetric Liquid Hydrogen Tanks

One of the major technical problems associated with cryogenic liquid propellant systems used to supply rocket engines and their subassemblies and components is the phenomenon of propellant tank pressurant and ullage gas collapse. This collapse is mainly caused by heat transfer from ullage gas to tank walls and interfacing propellant, which are both at temperatures well below those of this gas. Mass transfer between ullage gas and cryogenic propellant can also occur and have minor to significant secondary effects that can increase or decrease ullage gas collapse. Pressurant gas is supplied into cryogenic propellant tanks in order to initially pressurize these tanks and then maintain required pressures as propellant is expelled from these tanks. The net effect of pressurant and ullage gas collapse is increased total mass and mass flow rate requirements of pressurant gases. For flight vehicles this leads to significant and undesirable weight penalties. For rocket engine component and subassembly ground test facilities this results in significantly increased facility hardware, construction, and operational costs. "Collapse Factor" is a parameter used to quantify the pressurant and ullage gas collapse. Accurate prediction of collapse factors, through analytical methods and modeling tools, and collection and evaluation of collapse factor data has evolved over the years since the start of space exploration programs in the 1950's. Through the years, numerous documents have been published to preserve results of studies associated with the collapse factor phenomenon. This paper presents a summary and selected details of prior literature that document the aforementioned studies. Additionally other literature that present studies and results of heat and mass transfer processes, related to or providing important insights or analytical methods for the studies of collapse factor, are presented.

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“…Later work presented in one study 82 provides enhancements to the collapse factor correlation described above. These enhancements include:…”

Section: Semi-empirical Curve-fit Modelsmentioning

confidence: 99%

“…82 investigated the effects of mass transfer between cryogenic liquid propellant and ullage gas. The study concluded that evaporated propellant into the ullage gas region must be less than 26% of the total mass of pressurant gas supplied to the tank for the collapse factor correlation to be valid.…”

Section: Semi-empirical Curve-fit Modelsmentioning

confidence: 99%

A History of Collapse Factor Modeling and Empirical Data for Cryogenic Propellant Tanks

Dequay

Hodge

2010

46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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“…Ideally speaking, the pressurizing gas should not condense or be soluble into the liquid propellants and, thus, the helium gas would be the best choice for pressurizing the propellant tanks. In this way, the pressurization system controls the gas pressure in the gas space of the propellant tanks or ullage and maintains this ullage at a predetermined pressure required by propellant and structural requirements of tanks [10,11].…”

Section: Introductionmentioning

confidence: 99%

Transient thermal analysis of a cryogenic oxidizer tank in the liquid rocket propulsion system during the prelaunch helium gas pressurization

Kim

et al. 2012

J. Engin. Thermophys.

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The transient thermal behavior in the cryogenic oxidizer tank for the liquid propulsion system of the KSLV-I satellite launching space vehicle is theoretically investigated for the pressurization process by gaseous helium injection followed by the readiness check stage. The numerical model is established using the transient mass and energy conservation of oxygen/helium mixtures both in ullage and liquid regions. At the liquid-gas interface, various modes of heat and mass transfer are considered, including the liquid evaporation and the helium absorption. The present study focuses on the effects of the increasing pressurization level on some of important properties that should be considered in the propulsion system design, such as tank pressure, ullage gas temperature, and evaporation of liquid oxygen. Particularly, the tank pressure drop after the pressurization is investigated in the proposed design of propulsion system. Also, the effect of the initial loading of liquid oxygen in the oxidizer tank is studied and discussed. As for the helium absorption into the liquid region, its mass is negligibly small and it should not be the concern in design and operation of the oxidizer tank system.

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“…The correlation to predict the total required pressurant mass for an axisymmetric propellant tank was developed by Epstein and Anderson [3] in 1968 based on the concept of the collapse factor. Then it was revised by Van Dresar [4] in 1997 by comparing with test data obtained from spherical propellant tanks and including the concept of equivalent diameter. However, this correlation had the disadvantage of not being able to predict the pressurant mass flow rate with time during propellant outflow.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Prediction of Helium Mass Requirement for Propellant Tank Pressurization

Kwon

Kim

Kil

et al. 2012

Journal of Spacecraft and Rockets

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A numerical model that predicts the helium mass required for propellant tank pressurization during propellant outflow was developed. The model has the feature of including the effects of the internal hardware of the propellant tank such as baffles, pressurant storage tanks, and other instrumentation. It used a finite volume method that divides the ullage and tank wall one-dimensionally along the propellant tank axis. A series of cryogenic propellant drainage tests were carried out to verify the developed numerical model. The required amount of helium mass predicted by the model showed very good agreement with test data within an accuracy of 2:27% under the operating conditions. The developed model was applied to the pressurization system of Korea Sounding Rocket-III, and the results were compared with the flight-test data. The comparison results showed that the developed model was satisfactory for the prediction of the required helium mass during flight. Additionally, a parametric study was performed to test the sensitivity of the developed model, and the results showed that the heat transfer coefficient between the ullage and the tank wall was the key factor in the accuracy of the model.

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Prediction of Pressurant Mass Requirements for Axisymmetric Liquid Hydrogen Tanks

Cited by 10 publications

References 3 publications

A History of Collapse Factor Modeling and Empirical Data for Cryogenic Propellant Tanks

A History of Collapse Factor Modeling and Empirical Data for Cryogenic Propellant Tanks

Transient thermal analysis of a cryogenic oxidizer tank in the liquid rocket propulsion system during the prelaunch helium gas pressurization

Modeling the Prediction of Helium Mass Requirement for Propellant Tank Pressurization

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