January 1983:the Titan launch vehicles

Introduction

During the 1950’s the cold war between the United States and the Soviet Union was at its height. Work had already started on developing the United States’ first 1CBM (Inter¬Continental Ballistic Missile), the Atlas; but progress was slow. Because of the urgent need to acquire a large missile, the United States Air Force (USAF) decided to start work on a new missile. In 1955 the Martin Company was awarded a contract to design and develop a two-stage liquid propellant rocket. Taking its name from Greek Mythology, the giant rocket was named after the children of Uranus and Gaea - Titan.

Titan I

Titan got the go-ahead in 1957, and by late 1958 it was ready for ground tests. Titan I was a 98.4 ton missile, 27 m (88.6 ft) tall and 5.05 m (10 ft) in diameter. It used liquid oxygen and RP-1 (Kerosene) in both stages. The first stage carried two Aerojet-General LR-87 engines, giving a combined thrust of 1361 kT (300,000 lb). The second stage used a single Aerojet- General LR-91 engine, with a thrust of 36 t (80,000 lb).

The first successful attempt at launching Titan I came on 6 January 1959 using an inert second stage. Titan I eventually entered service with the Strategic Air Command in April 1962. However, Titan I saw only three years of service before being replaced by the Titan II.

Titan II

As far back as mid-1959, the disadvantages of using non-storable propellants were being discussed. Like the Atlas, Titan had to be set up from its horizontal before it could be fuelled and launched. This did not meet the requirements for a strategic ICBM. What was required was a retaliatory weapon that could withstand a pre-emptive attack of severe bombardment - an ICBM with storable propellants and launched from an underground silo. Considering these requirements, the decision was made to expand the promising technology of Titan I and use it as a basis for a new version: Titan II. Development began in June 1960.

Titan II was a two stage missile 3.05 m (10 ft) in diameter and 31 m (102 ft) tall, of which 21.5 m (70 ft) was the first stage. Two Aerojet-General YLR-87 rocket motors giving a com¬ bined thrust of 195 t (430,000 lb) were used in the first stage, while a single Aerojet-Ceneral YLR-91 rocket motor, giving a thrust of 45.4 t (100,0001b) was used to power the second stage. These engines ran on storable hypergolic propellants; a blend of hydrazine and unsymmetrical dimethylhydrazine (UDMH) as fuel, with nitrogen tetroxide as oxidizer. Since this combination is hypergolic - fuel and oxidizer ignite on contact - Titan II required no ignition system. Since both fuel and oxidizer can be stored and used at normal temperatures - instead of the supercold liquid oxygen of Atlas and Titan I - Titan II needed no cold storage and handling facilities.

A total of 35 Titan II test flights were conducted, the first on 16 March 1962. After a number of problems, of which longitudinal oscillation was the greatest, Titan II was declared to be operational in December 1963. By 1965 all of the Titan l's had been withdrawn from service and replaced by Titan II and Minuteman. Today there are about 52 Titan II missiles, each carrying nuclear warheads.

Gemini

Early in 1961, at the same time that the Martin Company was developing the Titan II as an ICBM, NASA was working on an improved Mercury manned spacecraft, later to be known as Gemini. NASA began to investigate the possibilities of using the Titan II as a launch vehicle for the two man Gemini spacecraft.

In December 1961 NASA announced Project Gemini and the selection of Titan II as the launch vehicle. The USAF, acting as contractor, took responsibility to ensure that NASA got its Titan II launch vehicles. Titan II was the most logical choice for Gemini because it was the most powerful and advanced rocket the United States had under development at that time and it could also be brought up to manned spacecraft launcher standard. Other factors in Titan's favour were its use of storable propellant,which made it capable of standing for considerable lengths of time on the launch pad; also the Air Force had done considerable work in designing and testing Titan as a launch vehicle for the Dyna-Soar programme.

In order to uprate it into a man-carrying launch vehicle, the USAF had to make a number of modifications. The main modifications were:

(i) a new Malfunction Detection System (MDS) and a backup flight control system,

(ii) an electrical system with backup circuits for guidance, engine shutdown, and staging,

(iii) substitution of radio guidance for inertial guidance.

The first test flight came on 16 March 1962 from the Cape Canaveral Missile Range. One and a half minutes after lift-off, when the first stage engine was still firing, the missile began to vibrate lengthwise at about 11 times a second for about 30 seconds. This trouble would not have been too serious for a missile, but in the case of a manned launcher it was dangerous. Accelerations of two and a half times that of gravity were recorded in this first flight. It took almost two years to analyse and solve the problem. Efforts to solve the Pogo problem had been in progress since early 1962 and the problem of instability in the second-stage engine was being tackled by Aerojet-General. They began in October 1963 and 18 months later their new design for the engine was a complete success. NASA installed the new engines with modified propellant injectors in the last six Gemini launch vehicles; the previous six flew with the old style injectors.

Due to NASA’s pressure, the Air Force began a drive in September 1963 to bring the manufacturing of parts up to the higher standard that NASA required. They spent $11 million on design improvements, improving welding techniques, and better assembly and quality control standards.

By the early spring of 1964, all three major problems that NASA had stated must be reduced to tolerable levels before Titan II could be fully man-rated, had been solved. In fact, the first Cemini flight occurred on 8 April 1964, the day before the Titan II research and development programme ended. It would be another year before Titan carried men. One more Gemini-Titan test flight occurred on 19 January 1965; again it was successful On 23 March 1965 a Titan II orbited the first manned Gemini spacecraft, Gemini 3. Titan proved itself by safely launching all ten manned Gemini spacecraft.

Titan III

In order to follow the development of Titan, we have to return to 1962. The Air Force wanted to develop a national launch capability for a wide variety of manned and unmanned space missions. In August 1962 the Department of Defense (DOD) approved the Titan III standard space launch system.

Titan IIIA

The Titan IIIA consisted of a two stage Titan II strengthened to accommodate a third stage and heavier payload. The new stage (Transtage) used the same type of storable propellants; its diameter was 3.05 m (10 ft) and it was 4.57 m (15 ft) high, with a thrust of 7.1 t (15,600 lb). Transtage had the capability of multiple restart. Titan IIIA stood 38 m (124 ft) tall, 3.05 m (10 ft) in diameter, and could deliver about 2.8 t (6,200 lb) into low Earth orbit. The first IIIA was launched from Cape Canaveral in September 1964. By 6 May 1965 four had been launched, with a fifth cancelled because research and development objectives had already been met. After further development, the IIIA became the central core for the Titan IIIC.

Titan IIIB

In July 1966, the first Titan IIIB was launched from the Vandenberg Air Force Base in California, and it became the USAF standard medium-weight launcher. The IIIB carried an Agena D as third stage with a strengthened Titan II as first and second stages. The total height varied between 44 m (144 ft) and 52.7 m (173 ft), according to payload. It could place up to 3.5 t (8,000 lb) into polar orbit or 450 kg (1,025 lb) into geosynchronous orbit. The Titan IIIB is presently used by the USAF for launching reconnaissance satellites.

Titan IIIC

In 1967 the Air Force introduced the Titan IIIC. Basically, it was a Titan IIIA (as a central core) plus two five-segment strap-on solid propellant boosters (stage 0) attached to the sides of the first stage. This configuration made the IIIC more than 9.1 m (30 ft) wide at the extreme. The IIIC is capable of launching payloads ranging from 13.21 mt (29,000 lb or 12.9 tons) into low Earth orbit; 1.31 my (3,000 lb) into synchronous equatorial orbit; and between 771 kg (1,700 lb) and 1,814 kg (4,000 lb) to Mars or Venus.

Titan IIID

The Titan IIID is essentially a IIIC without the Transtage. Payload capacity is a minimum of 13,600 kg (30,0001b or 13.4 tons) for low Earth orbit, to 10,890 kg (24,0001b or 10.7 tons) for polar orbit. Like the IIIB, the IIID is launched from the Vandenberg Air Force Base and used exclusively for military space operations, launching mainly surveillance and reconnaisance satellites (Big Bird and KH-11 being examples).

Titan IIIE-Centaur

Titan IIIE was developed for use as a civilian space launch vehicle for NASA for launching planetary spacecraft. It is basically a standard Titan IIIC, with a Centaur replacing the Transtage. Its most unusual feature is its top heavy appearance. This is caused by the large payload shroud which covers both the satellite and Centaur. The main Titan “core” has a diameter of 3.05 m (10 ft), while the shroud has a diameter of 4.27 m (14 ft). Total height of the IIIE is 48.8 m (160 ft).

Titan IIIM

In 1964, the Air Force began work on a Manned Orbital Laboratory (MOL). This vehicle consisted of a modified Gemini spacecraft resting on a cylindrical space laboratory. It was an experimental programme to study the use of space for military purposes. By 1966, the total weight was over 13,600 kg (30,000 lb) and it therefore required a more powerful booster than the Titan IIIC. The USAF decided on a modified IIIC design, called the Titan IIIM. The IIIMwas to use a seven segment solid fuel strap-on booster, as opposed to the five segment booster used on the IIIC. First stage engines were to use a new 15 to 1 expansion nozzle. Although an unmanned test flight of a MOL mock-up (reflying the Gemini 2 spacecraft) was launched in November 1966 by a Titan IIIC, the IIIM design was never used. On 10 June 1969, MOL was officially cancelled.

Titan 34D

The Titan 34D is the latest generation of USAF Titan HI launch vehicles. Apart from two main differences, the Titan 34D is basically the same design as the Titan IIIC. These two dissimilarities are that the Titan 34D utilises five and one-half segments solid propellant motors. This extra half segment provides an increased capability for heavy military payloads. It uses a solid propellant Inertial Upper Stage (IUS) instead of the Transtage. The IUS will also be used by NASA’s Space Shuttle in order to take payloads into higher orbits or interplanetary missions. Like the Titan IIIC, the Titan 34D will be used to orbit military satellites for the USAF, using Complex 40 at Cape Canaveral.