The Reusable Solid Rocket Booster (RSRB) - an Booster System

The Reusable Solid Rocket Booster Project consists of the solid rocket motor and integration of all the subsystems needed for ascent flight, entry, and recovery. Two papers are presented, one for the large solid rocket motor, and one describing the subsystems needed for the integrated booster system. The Reusable Solid Rocket Motor represents the largest solid rocket motor ever flown and the only human rated solid motor. Each Reusable Solid Rocket Motor (RSRM) provides nearly 3 million pounds of thrust to lift the integrated Space Shuttle vehicle from the launch pad. The integrated booster subsystems include the thrust vector control, auxiliary power unit, avionics, pyrotechnic, range safety system, parachutes, thermal protection, forward and aft structures, and water recovery systems. This represents the only recoverable and refurbishable solid rocket ever developed and flown. Challenges included subsystem integration and severe loads including water impact, sometimes resulting in hardware attrition. The post flight assessment process was quite detailed and a significant portion of flight operations. The unique challenges for these systems will be discussed in the following papers. 1 Reusable Solid Rocket Motor Chief Engineer, Space Shuttle Propulsion Chief Engineers Office, Marshall Space Flight Center, Huntsville, AL. 35812/EE02, Nonmember. 2 Reusable Solid Rocket Motor Deputy Chief Engineer, Space Shuttle Propulsion Chief Engineers Office, Marshall Space Flight Center, Huntsville, AL. 35812/EE02, Nonmember. 3 SRB Chief Engineer, Chief Engineer’s Office, EE02. 4 Assistant Chief Engineer, Chief Engineer’s Office, EE02. 5 Assistant Chief Engineer, Chief Engineer’s Office, USK-800, and Senior Member, AIAA. 6 Manager, Flight Systems Assessment, USK-384. 7 SRB Flow Manager, Flight Systems Assessment, USK-800. AIAA SPACE 2011 Conference & Exposition 27 29 September 2011, Long Beach, California AIAA 2011-7156 Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. American Institute of Aeronautics and Astronautics 1 Reusable Solid Rocket Motor—Accomplishments, Lessons, and a Culture of Success Dennis R. Moore and Jack Phelps Marshall Space Flight Center, Huntsville, State, AL, 35812 Abstract: The Reusable Solid Rocket Motor represents the largest solid rocket motor ever flown and the only human-rated solid motor. Each reusable solid rocket motor (RSRM) provides approximately 3-million lbf of thrust to lift the integrated Space Shuttle vehicle from the launch pad. The motors burn out approximately 2 minutes later, separate from the vehicle, and are recovered and refurbished. The size of the motor and the need for high reliability were challenges. Thrust shaping, via shaping of the propellant grain, was needed to limit structural loads during ascent. The motor design evolved through several block upgrades to increase performance and to increase safety and reliability. A major redesign occurred after STS-51L with the redesigned solid rocket motor (SRM). Significant improvements in the joint sealing systems were added. Design improvements continued throughout the program via block changes with a number of innovations including development of low temperature o-ring materials and incorporation of a unique carbon fiber rope thermal barrier material. Recovery of the motors and post flight inspection improved understanding of hardware performance, and led to key design improvements. Because of the multidecade program duration material obsolescence was addressed, and requalification of materials and vendors was sometimes needed. Thermal protection systems and ablatives were used to protect the motor cases and nozzle structures. Significant understanding of design and manufacturing features of the ablatives was developed during the program resulting in optimization of design features and processing parameters. The project advanced technology in eliminating ozone-depleting materials in manufacturing processes and the development of an asbestos-free case insulation. Manufacturing processes for the large motor components were unique and safety in the manufacturing environment was a special concern. Transportation and handling approaches were also needed for the large hardware segments. The RSRM achieved significant reliability via process control, ground test programs, and postflight assessment. Process control is mandatory for an SRM, because an acceptance test of the delivered product is not feasible. Process control included process failure modes and effects analysis, statistical process control, witness panels, and process product integrity audits. Material controls and inspections were maintained throughout the sub tier vendors. Material fingerprinting was employed to assess any drift in delivered material properties. The RSRM maintained both full-scale and subscale test articles. These enabled continuous improvement of design and evaluation of process control and material behavior. Additionally RSRM reliability was achieved through attention to detail in post flight assessment to observe any shift in performance. The postflight analysis and inspections provided invaluable reliability data as it enables observation of actual flight performance, most of which would not be available if the motors were not recovered. These unique challenges, features of the RSRM, materials and manufacturing issues, and design improvements will be discussed in the paper. The Reusable Solid Rocket Motor represents the largest solid rocket motor ever flown and the only human-rated solid motor. Each reusable solid rocket motor (RSRM) provides approximately 3-million lbf of thrust to lift the integrated Space Shuttle vehicle from the launch pad. The motors burn out approximately 2 minutes later, separate from the vehicle, and are recovered and refurbished. The size of the motor and the need for high reliability were challenges. Thrust shaping, via shaping of the propellant grain, was needed to limit structural loads during ascent. The motor design evolved through several block upgrades to increase performance and to increase safety and reliability. A major redesign occurred after STS-51L with the redesigned solid rocket motor (SRM). Significant improvements in the joint sealing systems were added. Design improvements continued throughout the program via block changes with a number of innovations including development of low temperature o-ring materials and incorporation of a unique carbon fiber rope thermal barrier material. Recovery of the motors and post flight inspection improved understanding of hardware performance, and led to key design improvements. Because of the multidecade program duration material obsolescence was addressed, and requalification of materials and vendors was sometimes needed. Thermal protection systems and ablatives were used to protect the motor cases and nozzle structures. Significant understanding of design and manufacturing features of the ablatives was developed during the program resulting in optimization of design features and processing parameters. The project advanced technology in eliminating ozone-depleting materials in manufacturing processes and the development of an asbestos-free case insulation. Manufacturing processes for the large motor components were unique and safety in the manufacturing environment was a special concern. Transportation and handling approaches were also needed for the large hardware segments. The RSRM achieved significant reliability via process control, ground test programs, and postflight assessment. Process control is mandatory for an SRM, because an acceptance test of the delivered product is not feasible. Process control included process failure modes and effects analysis, statistical process control, witness panels, and process product integrity audits. Material controls and inspections were maintained throughout the sub tier vendors. Material fingerprinting was employed to assess any drift in delivered material properties. The RSRM maintained both full-scale and subscale test articles. These enabled continuous improvement of design and evaluation of process control and material behavior. Additionally RSRM reliability was achieved through attention to detail in post flight assessment to observe any shift in performance. The postflight analysis and inspections provided invaluable reliability data as it enables observation of actual flight performance, most of which would not be available if the motors were not recovered. These unique challenges, features of the RSRM, materials and manufacturing issues, and design improvements will be discussed in the paper. 1 Reusable Solid Rocket Motor Chief Engineer, Space Shuttle Propulsion Chief Engineers Office, Marshall Space Flight Center, Huntsville, AL. 35812/EE02, Nonmember. 2 Reusable Solid Rocket Motor Deputy Chief Engineer, Space Shuttle Propulsion Chief Engineers Office, Marshall Space Flight Center, Huntsville, AL. 35812/EE02, Nonmember.