Those are the last of the major countermeasures developed to keep the first forces of gravity from causing them to black out as the shuttle rolls to a stop on the runway.
(Those; are; the last of the major countermeasures) (the shuttle; rolls; to a stop on the runway) (the major countermeasures; developed; )
Those the shuttle the major countermeasures
are rolls developed
the last of the major countermeasures
to a stop on the runway