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Liquid-Propellant Injection System
Published in D.P. Mishra, Fundamentals of Rocket Propulsion, 2017
As mentioned earlier, the stored gas pressurizing system is used extensively due to its higher level of reliability, in which gas is generally stored in tank at initial high pressure as high as 60 MPa, although, this gas is supplied at regulated pressure to the propellant tank through pressure regulator, valves, and so on. In early systems like the V2 rocket engines, nitrogen/air was used for logistic reason. But in recent times, helium gas is being routinely used as pressurizing gas due to its ready availability, and lower molecular weight, leading to reduced total weight of pressurized gas. Generally, some of the important design requirements for gas pressure feed system are low molecular weight of the gas, high gas density at storage condition, minimum residual gas weight, and high allowable stress-to-density ratio of the propellant tank materials.
Additive Manufacturing for the Space Industry
Published in Amit Bandyopadhyay, Susmita Bose, Additive Manufacturing, 2019
Next let us focus on the propellant tank, which is a thin-walled pressure vessel, typically made of a metallic alloy. Here we cannot implement the infill approach used on the structure, so the next step in reducing mass is to highly engineer the shape of the tank for optimal mass. Highly coupled CAD, structural, and thermal analysis tools must be employed to determine how to shape the part for maximum strength, stiffness, and mass. The addition of goal-seeking tools, such as genetic algorithms, capable of developing non-intuitive designs could enable highly engineered parts with reduced non-recurring costs. The same tools could be used to engineer subtractively manufactured parts; however, the resulting designs would likely be too expensive to produce using subtractive manufacturing alone making the additive manufacturing community the likely driver of development of these advanced tools. The result of this design philosophy might include areas of thicker or thinner solid material coupled to areas with low infill or complex open-cell shapes. Alternatively, we might find that it is best to implement a thin-walled vessel with an exoskeleton. In this case, merging the structure with the propellant tank may reduce parts count and eliminate areas that would typically carry extra material for attachment between the two system elements. All of the above processes can be applied using single material processes, but as we move into consideration of multi-material additive manufacturing we can expect to see tools that enable the blending or transitioning of materials along our tank wall to optimize mass. Complex algorithms that take into account variables of shape, strength, mass, temperature, alloy, and cost would need to be employed to optimize material systems throughout the part. New alloys are likely to be designed during this process that enable continuous transitions from one metal to another enabling even more highly engineered designs.
Decoding Mission Design Problem for NTP Systems for Outer Planet Robotic Missions
Published in Nuclear Technology, 2022
Saroj Kumar, L. Dale Thomas, Jason T. Cassibry
The sizing of the NTP injection stage involved calculation of the LH2 propellant tank estimation. The tank volume was determined based on the total propellant requirement along with an added ullage volume of 3%, which gives the required tank to be 9.6 m in length and 5.2 m in width. The analysis of the propellant tank mass is performed using the methods described in the published study.28 The total NTP injection stage length is 16.73 m, which includes a 6.63-m-long NTP engine and a 9.6-m-long LH2 tank and an interstage between the NTP engine and the LH2 tank of about 0.5 m. The dimensions of the spacecraft are estimated to be 3.5 m in width and 3.5 m in length. Table IV provides the detailed mass breakdown of the NTP injection and spacecraft.
Effects of cryogenic environment on strength properties of double-lap composite bonded joints
Published in Advanced Composite Materials, 2022
Hisashi Kumazawa, Hiroki Nakagawa, Tomohiro Saito, Takeshi Ogawa
The effects of extreme environments, such as high-temperature environments for aerospace engine structures and cryogenic environments for liquified hydrogen tank structures, on bonded joints have also been investigated. Shimoda et al. [12] conducted fracture tests of single-lap composite bonded joints at room and cryogenic temperature and found that the strength of the joints decreased at low temperature. Yoshimura et al. [13] designed bonded structures in which the composite wall of a cryogenic propellant tank was bonded to a metallic mouthpiece (boss) to reduce the thermal stress at the bond between dissimilar materials. The design was experimentally demonstrated to be effective for thermal stress reduction in the cryogenic composite tank structures. Yoshimura et al. [14,15] examined the fracture toughness of a bonded joint interface at cryogenic temperature and clarified the effects of crack mitigation in an adhesive layer on the fracture toughness. Bang et al. [16] and Kim et al. [17] investigated the strength of an adhesively bonded joint between an aluminum alloy sheet and stainless-steel foil at cryogenic temperature for liquefied natural gas tanks and attempted to improve the cryogenic strength of the bonded joint.
Numerical Investigation of Coaxial GCH4/LOx Combustion at Supercritical Pressures
Published in Combustion Science and Technology, 2021
Sindhuja Priyadarshini, Malay K Das, Ashoke De, Rupesh Sinha
In the last few years, there has been an increasing interest in numerical modeling of combustion phenomenon in cryogenic engines due to its complex nature. The combination of liquid hydrogen (fuel) with liquid oxygen (oxidizer) has been widely utilized as rocket fuel and oxidizer for various liquid propulsion systems. Liquid hydrogen (fuel) has multiple advantages like non-toxicity, clean combustion, and the highest specific impulse. But, the low density of H2 (liq.) leads to a large vehicle, a larger tank volume, and higher aerodynamic drag. Moreover, high cost and handling difficulties of H2 (liq.) have prohibited the widespread use of H2 (liq.)-LOx combination in liquid rocket engines (LRE’s) (Sutton 2005). Lately, it has been widely recognized that hydrocarbons are the most effective alternate propellants due to their high-density characteristics resulting in minimization of the propellant tank size and overall operational cost. The lowest hydrocarbon, liquid methane, has inherent properties like higher specific impulse and better cooling capabilities. The various advantages of liquid methane over other higher hydrocarbons have made it the most competitive fuel in combination with the liquid oxygen. Due to its soft cryogenic like characteristics, the GCH4/LOx combination can easily be operated at a cryogenic arrangement.