Verification (spaceflight)

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Verification in the field of space systems engineering covers two verification processes: Qualification and Acceptance

Contents

Overview

In the field of spaceflight verification standards are developed by DoD, NASA and the ECSS, among others. Large aerospace corporations may also developed their own internal standards. These standards exist in order to specify requirements for the verification of a space system product, such as: [1]

Verification or qualification, is one main reason that costs for space systems are high. All data are to be documented and to stay accessible for potential, later failure analyses. In previous times that approach was executed down to piece-parts level (resistors, switches etc.) whereas nowadays it is tried to reduce cost by usage of "CAM (Commercial, Avionics, Military) equipment" for non-safety relevant units.

Qualification and Acceptance

Qualification is the formal proof that the design meets all requirements of the specification and the parameters agreed in the Interface Control Documents (ICD) requirements with adequate margin, including tolerances due to manufacturing imperfections, wear-out within specified life-time, faults, etc. The end of the qualification process is the approval signature of the customer on the Certificate of Qualification (CoQ), or Qualification Description Document (QDD) agreeing that all the requirements are met by the product to be delivered under the terms of a contract.

Acceptance is the formal proof that the product identified is free of workmanship defects and meets preset performance requirements with adequate margin. Acceptance is based on the preceding qualification by reference to the used design / manufacturing documentation. The end of the acceptance process is the approval signature of the customer on the CoA, or QDD, agreeing that all the requirements are met by the product to be delivered under the terms of a contract.

There are four generally accepted Qualification methods:

Being qualified means demonstrating with margin that the design, and the implementation of the design, meets the intended preset requirements. There are many different Qualification strategies in order to reach the same goals. It consists of designing hardware (or software) to qualification requirements (including margin), testing dedicated hardware (or software) to qualification requirements to verify the design, followed by acceptance testing of flight hardware to screen workmanship defects. There are other strategies as well, the Proto-Qualification strategy for instance. Proto-Qualification consists of testing the first flight hardware to Proto-Qualification requirements to verify design, and testing subsequent flight hardware to acceptance levels to screen workmanship defects. This first Proto-Qualification unit is flight-worthy.

There are three generally accepted Acceptance methods:

If a deviation against the qualified item is detected (higher tolerances, scratches etc.) a Non-Conformance is to be processed; to justify that this item can be used despite this deviation an Analysis might be required.

See also

Related Research Articles

Acceptance testing

In engineering and its various subdisciplines, acceptance testing is a test conducted to determine if the requirements of a specification or contract are met. It may involve chemical tests, physical tests, or performance tests.

Software testing is an investigation conducted to provide stakeholders with information about the quality of the software product or service under test. Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation. Test techniques include the process of executing a program or application with the intent of finding software bugs, and verifying that the software product is fit for use.

Configuration management process for maintaining consistency of a product attributes with its design

Configuration management (CM) is a systems engineering process for establishing and maintaining consistency of a product's performance, functional, and physical attributes with its requirements, design, and operational information throughout its life. The CM process is widely used by military engineering organizations to manage changes throughout the system lifecycle of complex systems, such as weapon systems, military vehicles, and information systems. Outside the military, the CM process is also used with IT service management as defined by ITIL, and with other domain models in the civil engineering and other industrial engineering segments such as roads, bridges, canals, dams, and buildings.

Verify or verification may refer to:

Engineering tolerance permissible limit or limits of variation in value or dimension

Engineering tolerance is the permissible limit or limits of variation in:

  1. a physical dimension;
  2. a measured value or physical property of a material, manufactured object, system, or service;
  3. other measured values ;
  4. in engineering and safety, a physical distance or space (tolerance), as in a truck (lorry), train or boat under a bridge as well as a train in a tunnel ;
  5. in mechanical engineering the space between a bolt and a nut or a hole, etc.

In software project management, software testing, and software engineering, verification and validation (V&V) is the process of checking that a software system meets specifications and that it fulfills its intended purpose. It may also be referred to as software quality control. It is normally the responsibility of software testers as part of the software development lifecycle. In simple terms, software verification is: "Assuming we should build X, does our software achieve its goals without any bugs or gaps?" On the other hand, software validation is: "Was X what we should have built? Does X meet the high level requirements?"

V-Model

The V-model is a graphical representation of a systems development lifecycle. It is used to produce rigorous development lifecycle models and project management models. The V-model falls into three broad categories, the German V-Modell, a general testing model and the US government standard.

A test plan is a document detailing the objectives, resources, and processes for a specific test for a software or hardware product. The plan typically contains a detailed understanding of the eventual workflow.

Reliability engineering is a sub-discipline of systems engineering that emphasizes dependability in the lifecycle management of a product. Reliability describes the ability of a system or component to function under stated conditions for a specified period of time. Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time.

NEBS(Network Equipment-Building System) describes the environment of a typical United States RBOC Central Office. NEBS is the most common set of safety, spatial and environmental design guidelines applied to telecommunications equipment in the United States. It is an industry requirement, but not a legal requirement.

DO-178B, Software Considerations in Airborne Systems and Equipment Certification is a guideline dealing with the safety of safety-critical software used in certain airborne systems. Although technically a guideline, it was a de facto standard for developing avionics software systems until it was replaced in 2012 by DO-178C.

Environmental stress screening (ESS) refers to the process of exposing a newly manufactured or repaired product or component to stresses such as thermal cycling and vibration in order to force latent defects to manifest themselves by permanent or catastrophic failure during the screening process. The surviving population, upon completion of screening, can be assumed to have a higher reliability than a similar unscreened population.

Software project management is an art and science of planning and leading software projects. It is a sub-discipline of project management in which software projects are planned, implemented, monitored and controlled.

Production Part Approval Process(PPAP) is used in the automotive supply chain for establishing confidence in suppliers and their production processes. Actual measurements are taken from the parts produced and are used to complete the various test sheets of PPAP.

"All customer engineering design record and specification requirements are properly understood by the supplier and that the process has the potential to produce product consistently meeting these requirements during an actual production run at the quoted production rate." Version 4, 1 March 2006

Verification and validation are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. These are critical components of a quality management system such as ISO 9000. The words "verification" and "validation" are sometimes preceded with "independent", indicating that the verification and validation is to be performed by a disinterested third party. "Independent verification and validation" can be abbreviated as "IV&V".

Software quality control is the set of procedures used by organizations to ensure that a software product will meet its quality goals at the best value to the customer, and to continually improve the organization’s ability to produce software products in the future.

A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard.

Worst-case circuit analysis is a cost-effective means of screening a design to ensure with a high degree of confidence that potential defects and deficiencies are identified and eliminated prior to and during test, production, and delivery.

In a manufacturing environment, a request for waiver (RFW) is a request for authorization to accept an item which, during manufacture or after inspection, is found to depart from specified requirements, but nevertheless is considered suitable for use as is or after repair by an approved method.

Protoflight is a portmanteau of "prototype" and "flight hardware". As defined by NASA Technical Standard NASA-STD-7002A, it refers to a strategy where no test-dedicated qualification article exists and all production (flight) hardware is intended for flight. An example of a program using protoflight methods is the Mars Orbiter Laser Altimeter project.

References

  1. Space Engineering Verification, ECSS-E-10-02A, 17 November 1998, p.11.

Further reading