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A.5.2.7 Tank Mounting
A.5.2.7 Tank Mounting
The tanks and solid motor casings form the outside of the launch vehicle. There is no external skin and the tanks do not sit inside the vehicle. The tanks are the external structure, thus no extra mounting of the tanks and engines are necessary. The tanks are designed with the propulsion requirements, and then the rest of the rocket is sized. Extra support structures, such as rings and stringers, are designed to go inside the tanks as opposed to around the tanks.
Initially, we did research and preliminary design with the idea that support came from outside the tank. Research of similar launch vehicles, such as the Vanguard2, led to our initial design model shown in Fig. A.5.2.7.1.
Fig. A.5.2.7.1: Initial tank mounting design model.
(Steven Izzo)
In this model, the tank fits securely into the launch vehicle’s external body. The sides of the tank presses right onto the vehicle skin, with no extra space and no fastening devices such as riveting or welding. Securing the tank vertically in the launch vehicle are support rings. These rings are riveted to the external body, not the tank, and fitted above and below the tank to both secure the tank in place and assist in structural support for the entire launch vehicle.
The advantages we see in this model are that the tank could be designed independently of the external body, and then the dimensions could be simply input for the body. Also with this model, the tank could be completely supported without having to fasten it to the launch vehicle directly. Riveting and bolting a tank directly could not be possible, as the tank would lose pressure immediately, and welding is a more expensive process. With the model in Fig. A.5.2.7.1, it is possible to hold the tank in place by riveting or bolting and not interfering with the tank itself.
The design of the ring shown in the model is a simple rectangular cross section, which may have been the least expensive option in the design of the ring because the simplicity means a much smaller manufacturing cost.3 However, more complex structures were going to be looked at and code was going be developed to determine the exact design of the support rings. This design model was similar to other small payload launch vehicles such as the Vanguard.2 A portion of the Vanguard’s tank mounting system is shown in Fig. A.5.2.7.2.
Fig. A.5.2.11.2: Tank mounting system for the Vanguard vehicle.
(The Martin Company2)
Later it was determined that this model should be changed. The more practical and efficient method of launch vehicle design is to have the tanks and solid motor casings be the body of the launch vehicle itself. Having two external structures of different materials is inefficient when it can be replaced by one skin slightly thicker. The support for both the pressure and the stresses on the launch vehicle can be designed inside the tanks. While support on the inside of the tank requires welding, the pressure of the tank actually aides in support against the stresses on the vehicle.1 Thus, less inert structure is necessary. The new design is shown in Fig. A.5.2.7. From this, design began on the support for the stresses on the tanks and the launch vehicle as a whole.
Fig. A.5.2.7.3: New tank design model.
(Steven Izzo)
References
1. Boddy, J., Mitchell, J., and Harris, L., “Systems Evaluation of Advanced Structures and Materials in Future Launch Vehicles,” AIAA Journal no. 1103-391, 1967.
2. Klemans, B., “The Vanguard Satellite Launching Vehicle,” The Martin Company, Engineering Report No.11022, April 1960.
3. McMaster Carr Online Catalog, URL: [cited 23 January 2008].
Author: Steven Izzo