Gallery arm

Meanwhile, total communication devices are much more complex designs than start baskets, because they are required to ensure commimication between propellant and outlet during all phases of a mission. As shown in Figure 2.15, total communication screen channel LADs, or gallery arms, run the full length of the propellant tank. These LADs... 

FIGURE 2.19 Fluid Acquisition and Resupply Experiment-1 Gallery Arm. 

The design concept, basic flow physics, principle of operation, and advantages and disadvantages of vanes, sponges, and screen channel LADs (gallery arms) were outlined previously in Chapter 2. Sponges are not considered in this trade study because it was not desired to control the location of the ullage bubble. 

To determine how the IADs scale with flow rates, in order to compare performance with the vane PMD, simulations were also run at multiple flow rates between 1 x 10 and 2.76 x 10 kg/s for a 325 x 2300 screen in LH2 at a fixed liquid and pressurant gas temperature of 20.3 K each and a tank pressure of 101 kPa. Table 14.4 presents the resultant expulsion efficiencies and PMD mass for the screen channel LAD cases at different demand flow rates. The results show that up to a mass flow rate of 0.0049 kg/s, the LAD can achieve a maximum expulsion efficiency of 98.1% of the small-scale LH2 tank. This upper limit is due to the fact that the gallery arm cannot access the small residual propellant pool in between consecutive arms at very low fill levels due to the closed flow... 

Figure 14.14 compares the expulsion efficiency of the vanes and gallery arms across the flow rate range. At lower flow rates, the vanes can deliver higher expulsion efficiencies at a... 

Figures 14.14 and 14.15 can be used to determine the range of flowrates for which vtines are the optimal choice and the range over which gallery arm IADs are the more appropriate choice. The optimal PMD recommendation for a small-scale LH2 storage tank in low gravity is summarized in Figure 14.17. Based on the expulsion efficiency analysis, at flow rates less...

Although added complexities with modeling vanes and sponges with cryogenic liquids are anticipated, due to added evaporation and condensation, model improvements are not recommended for those PMDs yet. Surface Evolver can only be used for static or quasi-static L/V interfaces and is thus not recommended for transient environments. For gallery arms,... 

If gallery arms are the only solution that satisfies mission requirements, then updated models developed here can be used for cryogenic or storable propellants. An optimal screen can be chosen by trading the primary influential factors such as bubble point and FTS pressure drop, as well as secondary influential factors, such as wicking rate, screen compliance, material compatibility, and pressurant gas type. Once the optimal screen is chosen which meets all mission requirements, the LAD channel dimensions can be sized based on logic presented in Chapter 14. An optimal screen channel LAD is one that delivers the desired demand flow rate, against the specified adverse acceleration level, to the desired expulsion efficiency, using the least amount of LAD mass. 

---