<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The limiting factor is normally Lithium hydroxide cannisters for removing CO2 from the cabin air. After undocking from the ISS the number of extra days the orbiter can stay up and keep the crew alive is usually 4 or 5 days. MCC never uses up all of the contingency days. As I recall the most contingency time used was on STS-3 as they were not using the KSC runway yet since this was the third flight, Dryden was rained out (the lake bed was a lake and the program was not ready to land on a hard surface runway), we diverted to White Sands and scrubbed a landing day due to a dust storm. <br />Posted by shuttle_guy</DIV><br /><br />Thanks SG. is there some kind of manadated ruled that says thaat there should be two or three days operational reserve for each shuttle mission? How does this compared with Apollo, Gemini and Mercury?</p><p>Thanks</p><p>Jon</p> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em> Arthur Clarke</p> </div>