Editing Safety engineering (section)

==Preventing failure==
[[File:Survival redundancy.svg|thumbnail|A [[NASA]] graph shows the relationship between the survival of a crew of astronauts and the amount of [[redundancy (engineering)|redundant]] equipment in their spacecraft (the "MM", Mission Module).]]

Once a failure mode is identified, it can usually be mitigated by adding extra or redundant equipment to the system. For example, nuclear reactors contain dangerous [[radiation]], and nuclear reactions can cause so much [[heat]] that no substance might contain them. Therefore, reactors have emergency core cooling systems to keep the temperature down, shielding to contain the radiation, and engineered barriers (usually several, nested, surmounted by a [[containment building]]) to prevent accidental leakage. [[Safety-critical system]]s are commonly required to permit no [[single point of failure|single event or component failure]] to result in a catastrophic failure mode.

Most [[biology|biological]] organisms have a certain amount of redundancy: multiple organs, multiple limbs, etc.

For any given failure, a fail-over or redundancy can almost always be designed and incorporated into a system.

There are two categories of techniques to reduce the probability of failure:
Fault avoidance techniques increase the reliability of individual items (increased design margin, de-rating, etc.).
Fault tolerance techniques increase the reliability of the system as a whole (redundancies, barriers, etc.).<ref>
Tommaso Sgobba.
[http://www.spacesafetymagazine.com/spaceflight/commercial-spaceflight/commercial-space-safety-standards-lets-not-re-invent-wheel/ "Commercial Space Safety Standards: Let’s Not Re-Invent the Wheel"].
2015.
</ref>