1. Requirements

3.5.5 If a software component is determined to be safety critical software then software component classification shall be Software Class D or higher.

1.1 Notes

NPR 7150.2, NASA Software Engineering Requirements, does not include any notes for this requirement.

1.2 Applicability Across Classes


2. Rationale

The level of rigor required to develop and assure safety-critical software requires that safety-critical software be classified at a sufficiently high level that the minimum set of applicable requirements help ensure the appropriate level of rigor is applied.

3. Guidance

Safety critical software is any condition, event, operation, process, equipment, or system that could cause or lead to severe injury, major damage, or mission failure if performed or built improperly, or allowed to remain uncorrected.  All safety-critical software development programs are to have a minimal set of required software engineering development requirements.

Once a software component is determined to be safety-critical (see SWE-133), the minimum software classification for that component is Class D.  There are no exceptions.  If the software is safety critical software, then the software development is expected to meet the requirements for Class D, at a minimum. 

Engineering Technical Authorities (ETA) check the accuracy of the project’s classification of software components, so they ensure this requirement is met. The Center ETA can also waive or tailor specific requirements if the project provides adequate justification (see SWE-126). 

During the software development life cycle, periodic re-evaluations of safety-criticality and classification occur (see SWE-021), so the project and Center ETA need to keep this classification “rule” in mind as those reviews occur.

Additional guidance related to safety critical classification may be found in the following related requirement in this Handbook:

SWE-021 - Transition to a Higher Class
SWE-126 - Waiver and Deviation Considerations
SWE-133 - Software Safety Determination

4. Small Projects

No additional guidance is available for small projects.

5. Resources


6. Lessons Learned

There are currently no Lessons Learned identified for this requirement.