Criticality-One is NASA-speak
for a Space Shuttle point of failure
that is single point catastrophic
. In other words, a failure for which there is (and perhaps can be) no backup
or emergency plan. For example, a Solid Rocket Booster explosive bolt
failing to fire leaves one of the SRB
s attached (likely badly) to the External Tank
. This will unbalance the Shuttle at the least, and the small thrusters
on the nose of the SRB
may fire their plumes into the External Tank
, damaging it and/or detonating the hydrogen
In other words, Criticality-One is bad.
One step below this is Crit-One-R.