Editing Space Shuttle Atlantis (section)

===Composite overwrapped pressure vessels===
NASA announced in 2007 that 24 helium and nitrogen gas tanks in ''Atlantis'' were older than their designed lifetime. These [[composite overwrapped pressure vessel]]s (COPV) were designed for a 10-year life and later cleared for an additional 10 years; they exceeded this life in 2005. NASA said it could not guarantee any longer that the vessels on ''Atlantis'' would not burst or explode under full [[pressure]]. Failure of these tanks could have damaged parts of the orbiter and even wound or kill ground personnel. An in-flight failure of a pressure vessel could have even resulted in the loss of the orbiter and its crew. NASA analyses originally assumed that the vessels would [[Pressure vessel#Leak before burst|leak before they burst]], but new tests showed that they could in fact burst before leaking.

Because the original vendor was no longer in business, and a new manufacturer could not be qualified before 2010, when the shuttles were scheduled to be retired, NASA decided to continue operations with the existing tanks. Therefore, to reduce the risk of failure and the cumulative effects of load, the vessels were maintained at 80 percent of the operating pressure as late in the launch countdown as possible, and the launch pad was cleared of all but essential personnel when pressure was increased to 100 percent. The new launch procedure was employed during some of the remaining launches of ''Atlantis'',<ref name="aging">{{Cite web|url=http://www.space.com/news/ft_070604_aging_orbiters.html|title=Orbiters Feel Pains of Aging |access-date=November 6, 2007|publisher=Space.com|year=2007|first1=Todd|last1=Halvorson|first2=John|last2=Kelly|work=[[Florida Today]]}}</ref> but was resolved when the two COPVs deemed to have the highest risk of failure were replaced.<ref name="copv">{{Cite web|url=http://www.nasaspaceflight.com/2010/07/nasa-reviews-copv-for-final-program-flights/|title=NASA Reviews COPV Reliability Concerns for Final Program Flights|access-date=July 19, 2010|website=NASASpaceflight.com|first=Chris|last=Gebhardt|date=July 18, 2010}}</ref>