The probability of damage from this was low, but it is possible that the fill line assembly was loose and made worse by the fall. After some retesting (which did not include filling the tank with liquid oxygen), in November 1968 the shelf was re-installed in SM-109, intended for Apollo 13, which was shipped to KSC in June 1969. The Countdown Demonstration Test took place with SM-109 in its place near the top of the Saturn V and began on March 16, 1970. During the test, the cryogenic tanks were filled, but Oxygen Tank 2 could not be emptied through the normal drain line, and a report was written documenting the problem. After discussion among NASA and the contractors, attempts to empty the tank resumed on March 27. When it would not empty normally, the heaters in the tank were turned on to boil off the oxygen. The thermostatic switches were designed to prevent the heaters from raising the temperature higher than , but they failed under the 65-volt power supply applied. Temperatures on the heater tube within the tank may have reached , most likely damaging the Teflon insulation. The temperature gauge was not designed to read higher than , so the technician monitoring the procedure detected nothing unusual. This heating had been approved by Lovell and Mattingly of the prime crew, as well as by NASA managers and engineers. Replacement of the tank would have delayed the mission by at least a month. The tank was filled with liquid oxygen again before launch; once electric power was connected, it was in a hazardous condition. The board found that Swigert's activation of the Oxygen Tank2 fan at the request of Mission Control caused an electric arc that set the tank on fire. The board conducted a test of an oxygen tank rigged with hot-wire ignitors that caused a rapid rise in temperature within the tank, after which it failed, producing telemetry similar to that seen with the Apollo 13 Oxygen Tank 2. Tests with panels similar to the one that was seen to be missing on SM Sector4 caused separation of the panel in the test apparatus. Changes in response For Apollo 14 and subsequent missions, the oxygen tank was redesigned, the thermostats being upgraded to handle the proper voltage. The heaters were retained since they were necessary to maintain oxygen pressure. The stirring fans, with their unsealed motors,