Editing STS-6 (section)

== Mission background ==
The new orbiter was rolled out to [[Kennedy Space Center Launch Complex 39A|LC-39A]] in December 8, 1982. On December 18, 1982, ''Challenger'' was given a PFRF (Pre Flight Readiness Firing) to verify the operation of the main engines. The PFRF lasted for 16{{nbsp}}seconds. Although engine operation was generally satisfactory, telemetry data indicated significant leakage of [[liquid hydrogen]] in the thrust section. However, it was not possible to determine the location of the leak with certainty, so program directors decided on a second PFRF with added telemetry probes. It was known that during the test run on December 18, 1982, that recirculated exhaust gases and vibration leaked into the thrust section and this was considered a potential cause of the leak. Therefore, the original planned launch in late January 1983 had to be postponed.

On January 25, 1983, a second PFRF was conducted which lasted 23 seconds and exhibited more hydrogen leaks. Eventually, it was found that low pressure ducting in the No. 1 engine was cracked. The engine was replaced by a spare, which was found to also have leaks. A third engine had to be ordered from [[Rocketdyne]], and after thorough testing, turned out to be in proper operating condition. The No. 2 and No. 3 engines turned out to have leaks as well, and were taken out of the orbiter for repairs. By mid-March, the engine problems had been completely resolved.<ref>{{cite web|url=http://www.americaspace.com/?p=33504 |title=30 Years Since STS-6: The Rise of the Challenger (Part 1)|date=April 6, 2013}}</ref>

While the engine repairs were underway on February 28, 1983, a severe storm caused contamination of the mission's primary cargo, the first [[U.S. tracking and data relay satellite|Tracking and Data Relay Satellite-A]] ([[TDRS-1]]), while it was in the [[Kennedy Space Center Launch Complex 39|Payload Changeout Room]] on the [[Service structure|Rotating Service Structure]] at the launch pad. Consequently, the satellite had to be taken back to its checkout facility, where it was cleaned and rechecked. The Payload Changeout Room and the payload bay also had to be cleaned. All of these events pushed the launch back from March 26, 1983, to early April 1983.<ref>{{cite book|last=Evans|first=Ben|title=Space Shuttle Challenger: Ten Journeys into the Unknown|year=2007|publisher=Praxis Publishing|isbn=978-0-387-46355-1|page=26}}</ref>