dome of each tank. Stage I airframe The Stage I airframe consists of an interstage structure, oxidizer tank forward skirt, oxidizer tank, inter-tank structure, and fuel tank. The interstage structure, oxidizer tank forward skirt, and inter-tank structure are all fabricated assemblies using riveted skin, stringers and frame. The oxidizer tank is a welded structure consisting of a forward dome, tank barrel, an aft dome and a feedline. The fuel tank, also a welded structure, consists of a forward dome, tank barrel, aft cone, and internal conduit. Stage II airframe The Stage II airframe consists of a transition section, oxidizer tank, inter-tank structure, fuel tank and aft skirt. The transition section, inter-tank structure and aft skirt are all fabricated assemblies using riveted skin, stringers and frame. The oxidizer tank and fuel tank are welded structures consisting of forward and aft domes. Missile characteristics The following data is from publication (Dash 1) Guidance The first Titan II guidance system was built by ACDelco. It used an IMU (inertial measurement unit, a gyroscopic sensor) made by ACDelco derived from original designs from MIT Draper Labs. The missile guidance computer (MGC) was the IBM ASC-15. Stage I contained three gyros and the Autopilot. The Autopilot attempted to keep the missile straight during first stage flight and sent commands to the IMU on the 2nd stage. The IMU would compensate and send steering commands to the engine actuators. When spares for this system became hard to obtain, it was replaced by a more modern guidance system, the Delco Universal Space Guidance System (USGS). The USGS used a Carousel IV IMU and a Magic 352 computer. Launching Titan II missiles were designed to be launched from underground missile silos that were hardened against nuclear attack. This was intended to allow for the United States to ride out a nuclear first strike by an enemy and be able to retaliate with a second strike response. The order given to launch a Titan II was vested exclusively in the US President. Once an order was given to launch, launch codes were sent to the silos from SAC HQ or its backup in California. The signal was an audio transmission of a thirty-five-letter code. The two missile operators would record the code in a notebook. The codes were compared to each other and if they matched, both operators proceeded to a red safe containing the missile launch documents. The