“The Bascule Access Platform for Mercury Astronauts at Pad 14” by
Joel W. Powell
Quest Volume: 27 #2 (2020)
Look closely at launch photos of the final two Mercury-Atlas test flights conducted in 1961, and something about the umbilical tower does not seem quite right. The configuration of these structures appeared to be different between the launches of Mercury-Atlas 4 and Mercury-Atlas 5. It turns out that the umbilical tower at pad 14 (originally built for the Atlas-Agena/Midas launch vehicle) was heavily modified prior to the launch of Mercury-Atlas 5 in November 1961. There is no mention of the tower renovation in the official NASA history or chronology of Project Mercury, but a careful examination of labeled pre-launch photography by the author confirmed the unacknowledged modification to Launch Complex 14.
Powell, Joel W. “The Bascule Access Platform for Mercury Astronauts at Pad 14.” Quest: The History of Spaceflight Quarterly 27, no. 2 (2020): 49-52.