scope:

Purpose

It is NASA Policy that fracture control be imposed on all human-rated spaceflight systems to promote safety by mitigating the risk of catastrophic failure due to the presence of flaws. This document, Volume 1 of NASA-HDBK-5010A, provides interpretation of fracture control requirements and methodology and approaches that are acceptable to NASA for implementation of fracture control requirements for spaceflight hardware. Following the interpretations and guidelines of Volume 1 for this hardware will satisfy the intent of the applicable NASA fracture control requirements in NASA-STD-5019A, Fracture Control Requirements for Spaceflight Hardware. Volume 2 of NASA-HDBK-5010A, Fracture Control Implementation Handbook for Spaceflight Hardware, Example Applications and Additional Guidelines, provides examples of acceptable methodologies, assessment approaches, and other resources for the implementation of fracture control requirements of spaceflight hardware.

The requirement for imposing fracture control on hardware used in human spaceflight is based upon safety. Any program, human spaceflight or otherwise, may choose to impose fracture control to enhance mission success, although it is not specifically required for that purpose. NASA requires fracture control only to advance the safety of human spaceflight hardware.

In the fracture control concept, it is given that material and manufacturing processes may produce hardware with flaws of a sufficient size that can reduce the strength and life of the hardware. Fracture control is a multi-disciplinary process for accepting the risk associated with flaws that are undetected and may be present in hardware. If flaws are detected, the part will normally be repaired or scrapped. Flight of parts with known flaws is not permitted without specific analysis and approvals as described in section 8.1.5 of NASA-STD-5019A and within this Handbook under the same section numbering.

Fracture control programs can significantly supplement properly designed, high-quality hardware with additional assurance against catastrophic structural failures caused by unexpected or undetected flaws. A viable fracture control program relies on design, analysis, testing, nondestructive evaluation (NDE), and tracking of fracture critical hardware. It is expected that all spaceflight hardware will be manufactured consistent with aerospace standards, practices, and quality. It is beyond the scope, or intent, of fracture control to address technical or quality disciplines that should already exist and be in place regardless of fracture control. Fracture control is not intended to compensate for poor design, analytical errors, misuse, or poor quality.

The purpose of this Handbook is to provide fracture control implementation guidance applicable to a wide range of hardware designs and uses. A variety of fracture control considerations and options are addressed, some of which may not be applicable to a given design. Information is provided to assist the user in the development of an effective Fracture Control Plan (FCP), as well as other fracture control documentation.

Since fracture control deals with what might happen if flaw propagation leads to structural failure, reasonableness and credibility have to prevail. Many bad things can be imagined resulting from chained, unlikely events. Consequently, those who do fracture control and those who judge it should put some restraint on their imaginations and temper them with the likelihood that the events under consideration have a reasonable chance of occurring.

It is recommended that the fracture control analyst become familiar with all portions of this Handbook. This Handbook is organized by section to mirror the corresponding requirements in NASA-STD-5019A. The documents referenced in the Handbook are listed in section 2. Acronyms and definitions are listed in section 3. Section 4 addresses implementation of general requirements and responsibilities in fracture control. Section 5 addresses implementation of exempt fracture control requirements. The implementation of fracture control requirements and methodologies for assessing non-fracture critical hardware and fracture critical hardware are discussed in sections 6 and 7, respectively. Implementation of flaw screening, traceability, and material selection fracture control requirements are discussed in section 8. Section 9 provides information on implementation of verification of fracture control requirements, while section 10 discusses implementation of alternative approaches for fracture control.

Volume 2 of this Handbook provides additional resources such as specific examples, checklists, and approaches for the implementation of fracture control requirements.

Applicability

This Handbook is applicable to all human-rated spaceflight systems.

This Handbook is approved for use by NASA Headquarters and NASA Centers and Facilities. This language applies to the Jet Propulsion Laboratory (a Federally Funded Research and Development Center), other contractors, recipients of grants, cooperative agreements, or other agreements only to the extent specified or referenced in the applicable contracts, grants, or agreements.

References to "this Handbook" refer to NASA-HDBK-5010, Volume 1, Revision A; references to other documents state the specific document information.

This Handbook, or portions thereof, may be referenced in contract, program, and other Agency documents for guidance.

In this Handbook, the terms "may" or "can" denote discretionary privilege or permission, "should" denotes a good practice and is recommended but not required, "will" denotes expected outcome, and "is/are" denotes descriptive material or a statement of fact.

Tailoring

Tailoring of NASA-STD-5019A is allowed and anticipated. The requirements in NASA-STD-5019A are written to provide risk mitigation for catastrophic failure due to flaws for all types of spaceflight hardware. As such, a "one-size-fits-all" approach is used. Many of the requirements may not be applicable for some hardware systems. Alternative approaches are also allowed as discussed in section 10.

Overview

NASA-STD-5019A was written to provide three fundamental updates to the previous edition:

1. Include more detailed requirements for classification of composites or bonded hardware.

2. Organize the requirements to better represent how classification and implementation typically occur.

3. Minimize the number of actual requirements and provide corresponding rationale statements.

NASA-STD-5019A contains 26 requirements, some of which are to be selected from the most appropriate and applicable for each situation. The requirements in sections 5, 6, 7, and 8 are selected for each specific hardware and application. It is expected that the selected methodologies necessary to meet the fracture control requirements be documented in the FCP. The 5019A Fracture Control Diagram is repeated below for convenience in Figure 1-1, NASA-STD-5019A Fracture Control Requirements Diagram. A summary table of the NASA Technical Standards requirements is also included in section 9.2.