Editing Ranger 3 (section)

===Preparation for launch===
Preparation for Ranger&nbsp;3 was complicated by developmental issues with the Agena&nbsp;B stage, which had failed to operate correctly on Rangers&nbsp;1-2. Agena was primarily the domain of the [[U.S. Air Force]], who intended to use it for military payloads, and NASA had originally assumed it would begin flying in late 1960 or early 1961 by which time any developmental issues with the stage could be weeded out. However, Agena&nbsp;B ended up taking longer to put into service than originally anticipated and its performance also turned out to be somewhat less than expected, which forced some of the planned experiments on the [[Ranger program|Block&nbsp;II]] Rangers to be cancelled.

While the Thor-Agena&nbsp;B had begun flying in October&nbsp;1960, the Atlas-Agena&nbsp;B did not make its maiden voyage until July&nbsp;1961, meaning that Ranger&nbsp;1 was only the second time this launch vehicle combination had been flown. This delay was explained by the fact that Air Force programs such as [[Midas (satellite)|MIDAS]] were taking much longer to develop than Ranger. In addition, as 1961 ended, Agena&nbsp;Bs had malfunctioned no less than seven times (the two Ranger launches and five Thor-Agena launches).

Major General [[Osmond J. Ritland]], Commander of the Air Force Space Systems Division in [[Inglewood, California]], promised NASA that all problems with Agena would be corrected and, because they also affected [[United States Department of Defense|DoD]] programs, the issue was being taken "quite seriously". Among other changes made would be a thorough review of all Lockheed field operating equipment and procedures. In addition, an effort would be made to ensure that checkout procedures on [[U.S. Air Force]] and NASA Agenas were identical and any differences in them eliminated.
[[File:Erection of Missile 121D.jpg|thumb|Erection of Atlas 121D on 12/21/1961]]
In mid-December&nbsp;1961, Atlas&nbsp;121D and Agena&nbsp;6003 arrived at [[Cape Canaveral]] and were erected on [[Cape Canaveral Air Force Station Launch Complex 12|LC-12]]. On January 18, 1962, Ranger&nbsp;3 was stacked atop the booster, but the following day attempted fueling of the Atlas went awry when a tear was found in the intermediate bulkhead separating the LOX and RP-1 tanks. This would mean that the launch vehicle would have to be taken down from the pad for repairs, delaying the launch an entire month. However, Air Force and Convair officials instead suggested the novel solution of doing the repairs right there on LC-12. The Atlas's sustainer engine was removed and lowered into the flame deflector pit and wooden scaffolding installed so that technicians could go up into the RP-1 tank, remove the damaged intermediate bulkhead, and replace it. By January&nbsp;26, repairs were completed.