A.2.2.1 Component Ratings*
A.2.2.1 Component Ratings
According to the NASA Electronics Parts Assurance Group, there are 3 basic ratings of electrical components. They are:
Level 1: parts are inherently low risk and are suitable for use in all applications including life support and mission critical systems. Level 1 active parts should be reviewed for radiation hardness.
Level 2: parts have inherently higher risk than level 1 and are considered moderate risk. Level 2 parts are suitable for most general purpose space flight applications but are not recommended for life support or mission critical applications unless there is on-orbit reparability. Level 2 active parts need to be evaluated for radiation hardness.
Level 3: parts are inherently high risk because there is little dependable data or history available for them and changes in their materials, designs, and processes may occur continuously without notification. Level 3 parts are intended for mission applications where the use of high risk parts is acceptable. Level 3 parts should not be used in single-point failure or single-string applications unless a very high risk for failure or malfunction is acceptable. Level 3 parts must be evaluated for radiation hardness and radiation testing is recommended.
Level 1 parts are commonly called ‘space-rated’ or ‘S-Class’. The term ‘Class-B’ is synonymous with level 2 parts and level 3 components are also known as ‘commercial’ electronics. Each different class has specified requirements for testing procedures. Table A.2.2.1.1 outlines a few of these parameters.
Table A.2.2.1.1Electronic component rating comparisonCommercial requirements / S-Class requirements
Infinite production lot size / Built one at a time
No burn-in testing / Extended burn-in time (up to 240 hours)
No detailed failure analysis / Extended failure analysis
No product lifetime testing / 1,000 hour product lifetime testing on every lot
Production method allows for no traceability / Traceable to raw material selection
>1% failure per 1,000 hours is considered acceptable / 0.0001% failure rate per 1,000 hours is considered acceptable
The difference in testing procedures and type-ratings accounts for a large price difference in electronic devices. The avionics group has decided upon the use of non-space-rated (commercial) electronics with the goal of keeping the overall cost of the vehicle as low as possible.
*NEEDS REFERENCES!!
Author: Nicole Bryan