The LOR method had the advantage of allowing the lander spacecraft to be used as a "lifeboat" in the event of a failure of the command ship. Some documents prove this theory was discussed before and after the method was chosen. A 1964 MSC study concluded, "The LM [as lifeboat] ... was finally dropped, because no single reasonable CSM failure could be identified that would prohibit use of the SPS." Ironically, just such a failure happened on Apollo 13 when an oxygen tank explosion left the command ship without electrical power. The Lunar Module provided propulsion, electrical power and life support to get the crew home safely.
What was the advantage that the LOR method produced in the event of a spacecraft failure? What Apollo mission was this LOR method used and needed? What did the Lunar Module provide to help get the Apollo 13 home safely? In what year was the Lunar Module (LM) dropped because it wasn't seen as useful?