Mercury-Atlas was the first US manned launch to orbit built by Convair and Operated by NASA as part of Project Mercury that included the most launches with 9 missions the most famous being Mercury-Atlas 6 or Friendship 7.
The model I've made here is not built to scale, though the length is based on two Rockomax X200-32 Fuel Tanks and one C7 Brand Adapter - 2.5m to 1.25m.
One of the hardest part of this build was the 1.5 stage built with two pairs of 8 flags and with the booster section separated with a TD-18 Decoupler with a tiny space between booster section and main tank to allow for clean and reliable separation.
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https://kerbalx.com/AmARocketMan/Mercury-Atlas
Craft built in the VAB with 111 parts weighing at 50.4 tons combined and Mercury weighing 2.6 tons