LGM-25C Titan II
The Titan II was an intercontinental ballistic missile developed by the Glenn L. Martin Company from the earlier Titan I missile. Titan II was originally designed and used as an ICBM, but was later adapted as a medium-lift space launch vehicle to carry payloads to Earth orbit for the United States Air Force, National Aeronautics and Space Administration and National Oceanic and Atmospheric Administration. Those payloads included the USAF Defense Meteorological Satellite Program, NOAA weather satellites, and NASA's Gemini crewed space capsules. The modified Titan II SLVs were launched from Vandenberg Air Force Base, California, up until 2003.
Titan II missile
Part of the Titan rocket family, the Titan II ICBM was the successor to the Titan I, with double the payload. Unlike the Titan I, it used hydrazine-based hypergolic propellant which was storable and reliably ignited. This reduced time to launch and permitted it to be launched from its silo. Titan II carried the largest single warhead of any American ICBM.LGM-25C missile
The missile consists of a two-stage, rocket engine powered vehicle and a re-entry vehicle. Provisions are included for in-flight separation of Stage II from Stage I, and separation of the RV from Stage II. Stage I and Stage II vehicles each contain propellant and pressurization, rocket engine, hydraulic and electrical systems, and explosive components. In addition, Stage II contains the flight control system and missile guidance system. 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 Inertial Measurement Unit on the 2nd stage. The IMU would compensate and send steering commands to the engine actuators.Airframe
The airframe is a two-stage, aerodynamically stable structure that houses and protects the airborne missile equipment during powered flight. The missile guidance system enables the shutdown and staging enable relay to initiate Stage I separation. Each stage is in diameter and has fuel and oxidizer tanks in tandem, with the walls of the tanks forming the skin of the missile in those areas. External conduits are attached to the outside surface of the tanks to provide passage for the wire bundles and tubing. Access doors are provided on the missile forward, aft and between-tanks structure for inspection and maintenance. A removable cover for tank entry is located on the forward 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| Component | Dimension |
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| Stage I engine thrust | |
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| Vernier thrust |
Guidance
The first Titan II guidance system was built by ACDelco. It used an IMU made by ACDelco derived from original designs from MIT Draper Labs. The missile guidance computer 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. 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 survive a nuclear first strike by an enemy and be able to retaliate with a second strike response.The authority to order the launch of 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 safe featured a separate lock for each operator, who unlocked it using a combination known only to themself.The safe contained a number of paper envelopes with two letters on the front. Embedded in the thirty-five letter code sent from HQ was a seven-letter sub-code. The first two letters of the sub-code indicated which envelope to open. Inside was a plastic "cookie", with five more letters written on it. If the cookie matched the remaining five digits in the sub-code, the launch order was authenticated.
The message also contained a six-letter code that unlocked the missile. This code was entered on a separate system that opened a butterfly valve on one of the oxidizer lines on the missile engines. Once unlocked, the missile was ready to launch. Other portions of the message contained a launch time, which might be immediate or might be any time in the future.
File:Mk 6 reentry vehicle on display at National Atomic Museum.jpg|thumb|left|150px|Mark 6 re-entry vehicle which contained the W-53 nuclear warhead, fitted to the Titan II.
When that time was reached, the two operators inserted keys into their respective control panels and turned them to launch. The keys had to be turned within two seconds of each other, and had to be held for five seconds. The consoles were too far apart for one person to turn them both within the required timing.
Successfully turning the keys would start the missile launch sequence. First, the Titan II's batteries would be charged up completely and the missile would disconnect itself from silo power. Then the silo doors would slide open, giving a "SILO SOFT" alarm inside the control room. The guidance system of the Titan II would then configure itself to take control of the missile and ingest data to guide the missile to the target. Subsequently, main engine ignition would occur. Thrust would be allowed to build for a few seconds, then the supports holding the missile in place inside the silo would be released using pyrotechnic bolts, allowing the missile to lift off.
Development
The Titan rocket family was established in October 1955, when the Air Force awarded the Glenn L. Martin Company a contract to build an intercontinental ballistic missile. It became known as the Titan I, the nation's first two-stage ICBM and first underground silo-based ICBM. The Martin Company realized that the Titan I could be further improved and presented a proposal to the U.S. Air Force for an improved version. It would carry a larger warhead over a greater range with better accuracy and could be launched more quickly. The Martin company received a contract for the new missile, designated SM-68B Titan II, in June 1960. The Titan II was 50% heavier than the Titan I, with a longer first stage and a larger diameter second stage. The Titan II also used storable propellants: Aerozine 50 fuel, which is a 1:1 mixture of hydrazine and unsymmetrical dimethylhydrazine, and dinitrogen tetroxide oxidizer. The Titan I, whose liquid oxygen oxidizer had to be loaded immediately before launching, had to be raised from its silo and fueled before launch. The use of storable propellants enabled the Titan II to be launched within 60 seconds directly from within its silo. Their hypergolic nature made them dangerous to handle; a leak could lead to explosions, and the fuel was highly toxic. However, it allowed for a rapid launch once the order was received, a significant advantage vs earlier cryogenic ICBMs which could not remain fueled indefinitely and had to be fueled before launch.The first flight of the Titan II was in March 1962 and the missile, now designated LGM-25C, reached initial operating capability in October 1963. The Titan II contained one W-53 nuclear warhead in a Mark 6 re-entry vehicle with a range of. The W-53 had a yield of 9 megatons. This warhead was guided to its target using an inertial guidance unit. The 54 deployed Titan IIs formed the backbone of America's strategic deterrent force until the LGM-30 Minuteman ICBM was deployed en masse during the early to mid-1960s. Twelve Titan IIs were flown in NASA's Gemini crewed space program in the mid-1960s.
The Department of Defense predicted that a Titan II missile could eventually carry a warhead with a 35 megaton yield, based on projected improvements. However, that warhead was never developed or deployed. This would have made this warhead one of the most powerful ever, with almost double the power-to-weight ratio of the B41 nuclear bomb.