Case End Closure Configuration

The motor case end-closure (dome) configurations for cylindrical pressure vessels in general use are the hemispherical, ellipsoidal (refs. 69 and 70), torispherical (ref. 70), and Cassinian dome (ref. 71). The selection of the optimum design configuration is based on the need for or the desirability of one or more of the following minimum weight, maximum enclosed volume, minimum depth (envelope constraint), cost (including all aspects of fabrication and tooling), and cylindrical diameter with...

Structural Analysis

The capability of the case structure to withstand all the loads encountered in storage, shipping, handling, launch, and flight is evaluated and verified by a variety of analytical techniques. The use of any combination of the various methods of structural analysis is usually determined on the basis of the needs of the particular application and the cost effectiveness of the analysis. Nearly all analyses of rocket motor cases rely on computer programs to evaluate the elastic stresses in...

Case Attachment Fittings

Solid Rockets Images

Attachment fittings may be required as part of the case design for three basic purposes (1) to provide for assembly of segments of a segmented motor configuration, (2) to provide for the attachment of other components to the motor, and (3) to provide for attachment of the motor itself to a given structure. Various kinds of bolted, shear pin, lockwire, snap ring, and threaded attachments used to satisfy the first two functions are shown in figure 5 however, it is not intended to imply that these...

Nondestructive Testing Inspection Plan

The inspection master plan shall incorporate inspection processes for use from initial material procurement through case final acceptance to the extent necessary to maintain a specified reliability level. Inspection processes (NDT) should be used throughout the motor case program beginning with material procurement and continuing through fabrication, process control, and final acceptance. Each phase can use different inspection techniques with different acceptance or rejection standards. For...

Environmental Considerations

One of the most important aspects of case design for environmental conditions is a detailed review of all possible harmful environments and chemicals that may be encountered during the life history of the motor case from production of the structural materials through final service use, followed by a conscientious endeavor to minimize or eliminate these encounters. Such potentially harmful exposures are too numerous to cite however, some limited examples include (1) the use of dye-penetrant...

General Case Design

The basic principles of solid rocket motor case design and analysis are essentially the same as those of the plate-and-shell approach that has been used for many years in the design and analysis of boiler-type, pressure-containing structures and aircraft-type structures. As compared to the boiler-type pressure-vessel design, however, the motor case design is involved with a complex interplay and tradeoff among overall vehicle performance, compatibility with all other vehicle systems and...

Motor Case Loads

The case-loading profile shall include all individual design loads or the worst combination of design loads. The loading profile shall be determined by evaluation of any and all of the following loads. All axisymmetric and local design loads for definition of design load, see sec. 2.3.1.1 , including dynamic loads sec. 3.3.7 , should be resolved into membrane loads to determine the critical design loading condition. The critical case loading condition, or worst critical combination loading,...

Material Properties

A summary of the properties of some of the alloys commonly used in the aerospace industry is provided in table I. A more complete treatment of material properties including fracture toughness , forming characteristics, and weldability may be found in references 51 and 52. The commonly accepted sources of property data for some metals used in motor case design are reference 51 and references 52 to 55. These documents also provide the designer with general information on both heat-treatment...

Case Configuration Considerations

The motor case configuration can have a significant influence on material selection. For instance, the size of existing quench and temper heat-treating facilities with controlled atmosphere limits their use to motor cases of 140-in. diameter or less. Therefore, the material for cases above this size limit is selected from materials that can be fabricated without a final quench and temper heat treatment. See table I. Also, the number and location of case welds are influenced by the relation of...

Design Safety Factor

The case shall have the minimum design safety factor required to obtain the specified reliability. A design safety factor should be used in the design of rocket motor cases to account for contingencies e.g., underestimation of case loading, underestimation of case stresses, undetected variations in material properties, and undetected manufacturing deviations . The design safety factor should not be used for accumulation of conditions where variables are expected to occur. For example, the limit...

References

Cost and Performance Considerations in the Selection of Structural Materials for Ultra-Large-Size Booster Motors. J. Spacecraft Rockets, vol. 1, no. 1, Jan.-Feb. 1964, pp. 62-67. 2. Alexander, R. V. Apodaca, A. R. and Fournier, C. A. Cost and Performance Considerations in the Selection of Structural Materials and Propellants for Multi-Stage Solid Rocket Vehicles. Preprint 2415-62. ARS Structural Materials Conference, April 1962. 3. Alexander, R. V. and Fournier, C. A. A...

Structural Dynamics

The case shall withstand all transient and steady-state dynamic loads, or the worst combination of dynamic loads and critical static loads. Detailed dynamic analysis of the particular stage and the vehicle should be performed to insure that the motor case design is adequate for all imposed transient and steady-state dynamic loads. The dynamic loads imposed on the motor case as determined from the individual dynamic analysis should be integrated into the case structural analysis sec. 3.3.6 . The...

Design Optimization

Motor case design is governed by the motor and vehicle requirements, such as performance characteristics including motor propellant grain design , envelope constraints, mission profile, and other components within the individual stage and the vehicle. These factors are interdependent in their influence on the case design. In some programs, the basic case design parameters, including length-to-diameter ratio, external constraints, internal pressure, motor case flight loads, and propellant mass...

Rocket Motor Case

Solid Rocket Motor Design

The objectives of the motor case design are to establish the case configuration, select the structural material, and establish a case structure that results in either optimum performance or optimum cost effectiveness, depending on the specific program objectives and design requirements. Generally, the optimum case design is the least expensive one that satisfies all the mission objectives while not violating any imposed constraints i.e., the most cost effective . Typical solid rocket motor and...