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Titan is a family of U.S. expendable rockets used between 1959 and 2005. A total of 368 rockets of this family were launched, including all the Project Gemini manned flights of the mid-1960s. Titans were part of the American intercontinental ballistic missile deterrent until the late 1980s, and lifted other American military payloads as well as civilian agency intelligence-gathering satellites. Titans also were used to send highly successful interplanetary scientific probes throughout the Solar System.
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Titan I
The HGM-25A Titan I was the first version of the Titan family of rockets. It began as a backup ICBM project in case the Atlas was delayed. It was a two-stage rocket whose LR-87 engine was powered by RP-1 and liquid oxygen. It was operational from early 1962 to mid-1965. The ground guidance for the Titan was the UNIVAC ATHENA computer, designed by Seymour Cray, based in a hardened underground bunker. Using radar data, it made course corrections during the burn phase.
Unlike decommissioned Thor, Atlas, and Titan II missiles, the Titan I inventory was scrapped and never reused for space launches or RV tests, as all support infrastructure for the missile had been converted to the Titan II/III family by 1965.
Titan II
Most of the Titan rockets were the Titan II ICBM and their civilian derivatives for NASA. The Titan II used the LR-87-5 engine, a modified version of the LR-87, that relied on a hypergolic propellant combination of nitrogen tetroxide for its oxidizer and Aerozine 50 (a 50/50 mix of hydrazine and UDMH) for its fuel instead of the liquid oxygen and RP-1 combination used in the Titan I.
The first Titan II guidance system was built by AC Spark Plug. It used an Inertial measurement unit made by AC Spark Plug derived from original designs from the Charles Stark Draper Laboratory at MIT. The missile guidance computer (MGC) was the IBM ASC-15. When spares for this system became hard to obtain, it was replaced by a more modern guidance system, the Delco Electronics Universal Space Guidance System (USGS). The USGS used a Carousel IV IMU and a Magic 352 computer. The USGS was already in use on the Titan III space launcher when work began in March 1978 to replace the Titan II guidance system. The main reason was to reduce the cost of maintenance by $72 million per year; the conversions were completed in 1981.
The most famous use of the civilian Titan II was in the NASA Gemini program of manned space capsules in the mid-1960s. Twelve Titan II GLVs were used to launch two U.S. unmanned Gemini test launches and ten manned capsules with two-man crews. All of the launches were successes.
Also, in the late 1980s some of the deactivated Titan IIs were converted into space launch vehicles to be used for launching U.S. Government payloads. The final such vehicle launched a Defense Meteorological Satellite Program (DMSP) weather satellite from Vandenberg Air Force Base, California, on 18 October 2003.
Titan III
The Titan III was a modified Titan II with optional solid rocket boosters. It was developed on behalf of the United States Air Force as a heavy-lift satellite launcher to be used mainly to launch American military payloads and civilian intelligence agency satellites such as the Vela Hotel nuclear-test-ban monitoring satellites, observation and reconnaissance satellites (for intelligence-gathering), and various series of defense communications satellites.
The Titan III core was similar to the Titan II, but had a few differences. These included:
The Titan III family used the same basic LR-87 engines as Titan II (with performance enhancements over the years), however SRB-equipped variants had a heat shield over them as protection from the SRB exhaust, also the engines were modified for air-starting.
The Titan IIIA was a prototype rocket booster, which consisted of a standard Titan II rocket with a Transtage upper stage. The Titan IIIB with its different versions (23B, 24B, 33B, and 34B) had the Titan III core booster with an Agena D upper stage. This combination was used to launch the KH-8 GAMBIT series of intelligence-gathering satellites. They were all launched from Vandenberg Air Force Base, California, due south over the Pacific into polar orbits. Their maximum payload mass was about 7,500 lb (3,000 kg).
The powerful Titan IIIC used a Titan III core rocket with two large strap-on solid-fuel boosters to increase its launch thrust, and hence the maximum payload mass capability. The solid-fuel boosters that were developed for the Titan IIIC represented a significant engineering advance over previous solid-fueled rockets, due to their large size and thrust, and their advanced thrust-vector control systems. The Titan IIID was a derivative of the Titan IIIC, without the upper transtage, that was used to place members of the Key Hole series of reconnaissance satellites into low Earth orbits. The Titan IIIE, the one with an additional high-specific-impulse Centaur upper stage, was used to launch several scientific spacecraft, including both of NASA's two Voyager space probes to Jupiter, Saturn and beyond, and both of the two Viking missions to place two orbiters around Mars and two instrumented landers on its surface. The first guidance system for the Titan III used the AC Spark Plug company IMU (inertial measurement unit) and an IBM ASC-15 guidance computer from the Titan II. For the Titan III, the ASC-15 drum memory of the computer was lengthened to add 20 more usable tracks, which increased its memory capacity by 35%.
The more-advanced Titan IIIC used Delco's Carousel VB IMU and MAGIC 352 Missile Guidance Computer (MGC) .
Titan IV
The Titan IV was a "stretched" Titan III with non-optional solid rocket boosters on its sides. The Titan IV could be launched with a Centaur upper stage, the USAF Inertial Upper Stage (IUS), or no upper stage at all. This rocket was used almost exclusively to launch American military or civilian intelligence agency payloads. However, it was also used for a purely scientific purpose to launch the NASA–ESA Cassini / Huygens space probe to Saturn in 1997. The primary intelligence agency that needed the Titan IV's launch capabilities was the National Reconnaissance Office (NRO).
By the time it became available, the Titan IV was the most powerful unmanned rocket produced and used by United States, because the extremely large and powerful Saturn V rocket had not been available for some years. Still, the Titan IV was considered to be quite expensive to manufacture and use. By the time the Titan IV became operational, the requirements of the Department of Defense and the NRO for launching satellites had tapered off due to improvements in the longevity of reconnaissance satellites, and in addition, the declining foreign threat to the security of the United States that followed the internal disintegration of the Soviet Union.
As a result of these events, and improvements in technology, when including the cost of the ground operations and facilities for the Titan IV at Vandenberg Air Force Base for launching satellites into polar orbits, the unit cost of a Titan IV launch was very high. Titan IVs were also launched from the Cape Canaveral Air Force Station in Florida for non-polar orbits.
Rocket fuel
Liquid oxygen is dangerous to use in an enclosed space, such as a missile silo, and cannot be stored for long periods in the booster oxidizer tank. Several Atlas and Titan I rockets exploded and destroyed their silos. The Martin Company was able to improve the design with the Titan II. The RP-1/LOX combination was replaced by a room-temperature fuel whose oxidizer did not require cryogenic storage. The same first-stage rocket engine was used with some modifications. The diameter of the second stage was increased to match the first stage. The Titan II's hypergolic fuel and oxidizer ignited on contact, but they were highly toxic and corrosive liquids. The fuel was Aerozine 50 (a 50/50 mix of hydrazine and UDMH) and the oxidizer was nitrogen tetroxide.
Accidents at Titan II silos
There were several accidents in Titan II silos resulting in loss of life and/or serious injuries. In August 1965, 53 construction workers were killed in Arkansas when hydraulic fluid used in the Titan II caught fire from a welder's torch in a missile silo northwest of Searcy. The liquid fuel missiles were prone to developing leaks of their toxic propellants. At a silo in Kansas outside Rock, an oxidizer transfer line carrying nitrogen tetroxide (NTO) ruptured on August 24, 1978. An ensuing orange vapor cloud forced 200 rural residents to evacuate the area. A staff sergeant of the maintenance crew was killed while attempting a rescue and a total of twenty were hospitalized. Another site at Potwin, leaked NTO oxidizer in April 1980 with no fatalities, and was later closed.
In September 1980, at a Titan II silo (374-7) in Arkansas near Damascus, a technician dropped a 8 lb (3.6 kg) socket that fell 70 ft (21 m), bounced off a thrust mount, and broke the skin of the missile's first stage, over eight hours prior to an eventual explosion. The puncture occurred about 6:30 p.m. and when a leak was detected shortly after, the silo was flooded with water and civilian authorities were advised to evacuate the area. As the problem was being attended to at around 3 a.m., leaking rocket fuel ignited and blew the 8,000 lb (3,630 kg) nuclear warhead out of the silo. It landed harmlessly several hundred feet away. There was one fatality and 21 were injured, all from the emergency response team from Little Rock AFB. The explosion lifted the 740-ton doors off the silo and left a crater 250 feet (76 m) in diameter.
Retirement
The 54 Titan IIs, in Arizona, Arkansas, and Kansas, were replaced in the U.S. arsenal by 50 MX "Peacekeeper" solid-fuel rocket missiles in the mid-1980s, the last Titan II silo was deactivated in May 1987. The 54 Titan IIs had been fielded along with a thousand Minuteman missiles from the mid-1960s through the mid-1980s. Most of the decommissioned Titan II ICBMs were refurbished and used for Air Force space launch vehicles, with a perfect launch success record.
For orbital launches, there were strong advantages to using higher-performance liquid hydrogen or RP-1 (kerosene) fueled vehicles with a liquid oxygen oxidizer; the high cost of using hydrazine and nitrogen tetroxide, along with the special care that was needed due to their toxicity, were a further consideration. Lockheed Martin decided to extend its Atlas family of rockets instead of its more expensive Titans, along with participating in joint-ventures to sell launches on the Russian Proton rocket and the new Boeing-built Delta IV class of medium and heavy-lift launch vehicles. The Titan IVB was the last Titan rocket to remain in service, making its penultimate launch from Cape Canaveral on 30 April 2005, followed by its final launch from Vandenberg Air Force Base on 19 October 2005, carrying the USA-186 optical imaging satellite for the National Reconnaissance Office (NRO).
A number of HGM-25A Titan I and LGM-25C Titan II missiles have been distributed as museum displays across the United States.