Titan I

The Martin Marietta SM-68A/HGM-25A Titan I was the United States' first multistage intercontinental ballistic missile (ICBM), in use from 1959 until 1962. Though the SM-68A was operational for only three years, it spawned numerous follow-on models that were a part of the U.S. arsenal and space launch capability. The Titan I was unique among the Titan models in that it used liquid oxygen and RP-1 as propellants; all subsequent versions used storable propellants instead.

Originally designed as a backup in case the U.S. Air Force's SM-65 Atlas missile development ran into problems, the Titan was ultimately beaten into service by Atlas. Deployment went ahead anyway to more rapidly increase the number of missiles on alert and because the Titan's missile silo basing was more survivable than Atlas.

The succeeding LGM-25C Titan II served in the U.S. nuclear deterrent until 1987 and had increased capacity and range in addition to the different propellants.

History

By January 1955, the size of nuclear weapons had been shrinking dramatically, allowing the possibility of building a bomb that could be carried by a missile of reasonable size. The Titan I program began on the recommendation of the Scientific Advisory Committee. The committee presented to the United States Air Force (USAF) their findings of the technical feasibility to develop weapons (bombs) and their delivery systems (intercontinental range ballistic missiles) that were completely invulnerable to "surprise" attack.

The reduction in the mass of nuclear warheads allowed full coverage of the entire Sino-Soviet land mass, and the missile control capabilities were also upgraded. The Titan I would be fully independent in controlled flight from launch to the ballistic release of the warhead, which would descend to its target by the combination of gravity and air resistance alone. In May 1955 the Air Materiel Command invited contractors to submit proposals and bids for the two stage Titan I ICBM, formally beginning the program. In September 1955, The Martin Company was declared the contractor for the Titan missile. In early October the Air Force's Western Development Division was ordered to start work. The Titan was developed in parallel with the Atlas (SM-65/HGM-16) ICBM, serving as a backup with potentially greater capabilities and an incentive for the Atlas contractor to work harder. Martin was selected as the contractor due to its proposed organizationGreen, Warren E., The Development of the SM-68 Titan, Wright-Patterson Air Force Base: Air Force Systems Command, 1962, AFSC Historical Publications Series 62-23-1, p. 17. and method of igniting a liquid fueled engine at high altitude.

The Titan I was initially designated as a bomber aircraft (B-68), but was later designated SM-68 Titan and finally HGM-25A in 1962.

Program management

The previous strategic missile programs of the Air Force had been administered using the "single prime contractor concept" (later called the weapon system concept). This had resulted in three badly botched programs; the programs of the Snark, Navaho and RASCAL missiles had slipped an average of 5 years and had cost overruns of 300 per cent or more. In response, the Teapot Committee was tasked with evaluating requirements for ballistic missiles and methods of accelerating their development. As a result of the ensuing recommendations, the USAF established the Western Development Division and Brigadier General Bernard Schriever was detailed to command it. Schriever devised an entirely new organization for program management. The Air Force was to act as "prime contractor," the Ramo-Woolridge Corporation was contracted to provide systems engineering and technical direction of all ballistic missiles. The airframe contractor also would assemble the sub-systems provided by other Air Force contractors. At the time, this new organization was very controversial.

The Titan I represented an evolution of technology when compared to the Atlas missile program, but shared many of the Atlas' problems. The liquid oxygen oxidizer could not be stored for long periods of time, increasing the response time as the missile had to be raised out of its silo and loaded with oxidizer before a launch could occur. The main improvements of the Titan I over the first Atlas's deployed were vertical storage in a fully underground silo and an improved fully internal inertial guidance system. Later Atlas E/F models were equipped with what would have been the Titan I's guidance system The Titan I would be deployed with the Bell Labs radio-inertial guidance system.

Budgetary problems

The Titan, proposed as a fallback in case the Atlas failed, was by December 1956 accepted by some as a "principal ingredient of the national ballistic missile force." At the same time, others pushed for the cancellation of the Titan program almost from the beginning, arguing that it was redundant.Green, Warren E., The Development of the SM-68 Titan, Wright-Patterson Air Force Base: Air Force Systems Command, 1962, AFSC Historical Publications Series 62-23-1, p. 37. Despite counterarguments that the Titan offered greater performance and growth potential than the Atlas as a missile and space launch vehicle, the Titan program was under constant budgetary pressure. In the summer of 1957 budget cuts led Secretary of Defense Wilson to reduce the Titan production rate from the proposed seven per month to two a month, which left the Titan as a research and development program only. However, the Sputnik crisis, which started 5 October 1957, ended any talk of canceling Titan. Priority was restored, and 1958 saw increases in funding and plans for additional Titan squadrons.Divine, Robert A., The Sputnik Challenge, New York: Oxford University Press, 1990, , p. xv.

Flight testing

The Titan I flight testing consisted of the first stage only Series I, the cancelled Series II, and Series III with the complete missile.Green, Warren E., The Development of the SM-68 Titan, Wright-Patterson Air Force Base: Air Force Systems Command, 1962, AFSC Historical Publications Series 62-23-1, p. 91.

A total of 62 flight test missiles were constructed in various numbers. The first successful launch was on 5 February 1959 with Titan I A3, and the last test flight was on 29 January 1962 with Titan I M7. Of the missiles produced, 49 launched and two exploded: six A-types (four launched), seven B-types (two launched), six C-types (five launched), ten G-types (seven launched), 22 J-types (22 launched), four V-types (four launched), and seven M-types (seven launched). Missiles were tested and launched in Florida at Cape Canaveral Air Force Station from Launch Complexes LC15, LC16, LC19, and LC20.Cleary, Mark, The 6555th Missile and Space Launches Through 1970, 45th Space Wing History Office, Patrick Air Force Base, Florida, Chapter III Section 6

The four A-type missile launches with dummy second stages all occurred in 1959 and were carried out on 6 February, 25 February, 3 April, and 4 May. The guidance system and stage separation all performed well, and aerodynamic drag was lower than anticipated. Titan I was the first program to have a new missile succeed on the initial attempt, which left launch crews unprepared for the series of failures that followed. Missile B-4 exploded from a LOX pump failure during a static firing at Martin's Denver test stand in May and assorted other mishaps occurred in the following two months.Green, Warren E., The Development of the SM-68 Titan, Wright-Patterson Air Force Base: Air Force Systems Command, 1962, AFSC Historical Publications Series 62-23-1, p. 93.

Missile B-5 was intended to launch from LC-19 as the first flight article Lot B missile, incorporating most Titan I missile systems but with a dummy warhead. A planned launch on July 31 was scrubbed due to fuel system problems. At about noon on August 5, B-5 was launched. The missile rose about ten feet before the engines shut down and it fell back onto LC-19 in a fiery explosion. Postflight investigation found that the hold-down bolts released prematurely, causing B-5 to lift before full thrust rise had been achieved. A still-attached umbilical sent a shutdown command to the engines. LC-19 was badly damaged and would not be used again for six months.

Further problems occurred over the next several months. Missiles continued to be damaged through careless personnel mistakes and General Osmond Ritland sent Martin an angry letter calling their handling of the Titan program "inexcusable." Ritland's disciplinary blast had little effect for the time being. On December 10, the first attempt was made to launch a Lot C missile, which would be a complete Titan I with all systems and a detachable warhead. Missile C-3 was prepared for launch but much like with B-5, a premature shutdown command was sent due to failure of an umbilical to detach, fortunately the missile had not been released from the pad. The umbilical was quickly repaired but any relief at having avoided near-disaster was short-lived.

At 1:11 PM EST on December 12, Missile C-3 launched from LC-16. The engines started, but the missile almost immediately disappeared in a fireball. The mishap was quickly traced to the Range Safety destruct charges on the first stage inadvertently going off. Martin technicians had moved the activator relay into a vibration-prone area during repair work on the missile and testing confirmed that the shock from the pad hold-down bolts firing was enough to set off the relay. The pad was not as badly damaged as LC-19 had been from the B-5 mishap as C-3 had not actually lifted and it was repaired in only two months.Green, Warren E., The Development of the SM-68 Titan, Wright-Patterson Air Force Base: Air Force Systems Command, 1962, AFSC Historical Publications Series 62-23-1, p. 94.

On 2 February 1960, LC-19 returned to action as Missile B-7A marked the first successful flight of a Titan with a live upper stage—this was a composite missile as B-7's original upper stage was damaged months earlier in an accident and it was replaced with the upper stage from Missile B-6 which had had its first stage damaged in another accident. On 5 February, LC-16 returned to action by hosting Missile C-4. The second attempt at a Lot C Titan failed at T+52 seconds when the guidance compartment collapsed, causing the RVX-3 reentry vehicle to separate. The missile pitched down and the first stage LOX tank ruptured from aerodynamic loads, blowing the stage to pieces. After the first stage destroyed itself, the second stage separated and began engine ignition, sensing that normal staging had taken place. With no attitude control, it began tumbling end-over-end and quickly lost thrust. The stage plummeted into the Atlantic Ocean some 30–40 miles downrange After the successful flight of Missile G-4 on 24 February, Missile C-1's second stage failed to ignite on 8 March due to a stuck valve preventing the gas generator from starting. The last Lot C missile was C-6 which flew successfully on April 28. The Lot G missiles incorporated several design improvements to correct problems encountered on previous Titan launches. On 1 July, the newly opened LC-20 hosted its first launch when Missile J-2, an operational prototype, was flown. Unfortunately, a broken hydraulic line caused the Titan's engines to gimbal hard left almost as soon as the tower was cleared.Green, Warren E., The Development of the SM-68 Titan, Wright-Patterson Air Force Base: Air Force Systems Command, 1962, AFSC Historical Publications Series 62-23-1, p. 96. The missile pitched over and flew onto a near-horizontal plane when Range Safety sent the destruct command at T+11 seconds. The burning remains of the Titan impacted 300 meters from the pad in an enormous fireball. The piece of plumbing responsible for the missile failure was retrieved—it had popped out of its sleeve resulting in loss of first stage hydraulic pressure. The sleeve was not tight enough to hold the hydraulic line in place, and the pressure being imparted into it at liftoff was enough to pop it loose. Examination of other Titan missiles found more defective hydraulic lines, and the Missile J-2 debacle caused a wholesale review of manufacturing processes and improved parts testing.

The next launch at the end of the month (Missile J-4) suffered premature first stage shutdown and landed far short of its planned impact point. Cause of the failure was a LOX valve closing prematurely, which resulted in the rupture of a propellant duct and thrust termination. Missile J-6 on 24 October set a record by flying 6100 miles. The J series resulted in minor changes to alleviate the second stage shutting down prematurely or failing to ignite.

The string of failures during 1959–60 led to complaints from the Air Force that Martin–Marietta weren't taking the Titan project seriously (since it was just a backup to the primary Atlas ICBM program) and displayed an indifferent, careless attitude that resulted in easily avoidable failure modes such as Missile C-3's range safety command destruct system relays being placed in a vibration-prone area.

In December, Missile V-2 was undergoing a flight readiness test in a silo at Vandenberg Air Force Base, California. The plan was to load the missile with propellant, raise it up to firing position, and then lower it back into the silo. Unfortunately, the silo elevator collapsed, causing the Titan to fall back down and explode. The blast was so violent that it ejected a service tower from inside the silo and launched it some distance into the air before coming back down.See, Earl, Titan Missile Memoirs, Huntington Beach, California: American Aviation Historical Society Journal, Summer 2014, p. 118.

A total of 21 Titan I launches took place during 1961, with five failures. On 20 January 1961, Missile AJ-10 launched from LC-19 at CCAS. The flight ended in failure when an improper disconnect of a pad umbilical caused an electrical short in the second stage. The Titan performed well through the first stage burn, but after second stage separation, the fuel valve to the gas generator failed to open, preventing engine start. Missiles AJ-12 and AJ-15 in March were lost due to turbopump problems. Missile M-1's second stage lost thrust when the hydraulic pump failed. Missile SM-2 experienced early first stage shutdown; although the second stage burn was successful, it had to run to propellant depletion instead of a timed cutoff. The added stress of this operation apparently resulted in a failure of either the gas generator or turbopump, as the vernier solo phase ended prematurely. Missile M-6's second stage failed to start when an electrical relay malfunctioned and reset the ignition timer.Stumpf, David K., Titan II, p 276, The University of Arkansas Press, Fayetteville, Arkansas, 2000

With attention shifting to the Titan II, there were only six Titan I flights during 1962, with one failure, when Missile SM-4 (21 January) experienced an electrical short in the second stage hydraulic actuator, which gimbaled hard left at T+98 seconds. Staging was performed successfully, but the second stage engine failed to start.

Twelve more Titan Is were flown in 1963–65, with the finale being Missile SM-33, flown on 5 March 1965. The only total failure in this last stretch of flights was when Missile V-4 (1 May 1963) suffered a stuck gas generator valve and loss of engine thrust at liftoff. The Titan fell over and exploded on impact with the ground.

Although most of the Titan I's teething problems were worked out by 1961, the missile was already eclipsed not only by the Atlas, but by its own design successor, the Titan II, a bigger, more powerful ICBM with storable hypergolic propellants. The launch pads at Cape Canaveral were quickly converted for the new vehicle. Vandenberg Launch Complex 395 continued to provide for operational test launches. The last Titan I launch was from LC 395A silo A-2 in March 1965. After a brief period as an operational ICBM, it was retired from service in 1965 when Defense Secretary Robert McNamara made the decision to phase out all first generation cryogenically fueled missiles in favor of newer hypergolic and solid-fueled models. While decommissioned Atlas (and later Titan II) missiles were recycled and utilized for space launches, the Titan I inventory were stored and eventually scrapped.

Characteristics

Produced by the Glenn L. Martin Company (which became "The Martin Company" in 1957), Titan I was a two-stage, liquid-fueled ballistic missile with an effective range of 6,101 nautical miles (11,300 km). The first stage delivered 300,000 pounds (1,330 kN) of thrust, the second stage 80,000 pounds (356 kN). The fact that Titan I, like Atlas, burned Rocket Propellant 1 (RP-1) and liquid oxygen ( LOX) meant that the oxidizer had to be loaded onto the missile just before launch from an underground storage tank, and the missile raised above ground on the enormous elevator system, exposing the missile for some time before launch. The complexity of the system combined with its relatively slow reaction time – fifteen minutes to load, followed by the time required to raise and launch the first missile. Following the launch of the first missile the other two could reportedly be fired at -minute intervals.Hoselton, Gary A., Titan I Guidance System, Brekenridge, Colorado: Association of Air Force Missileers, Volume 6, Number 1, March, 1998, p. 4. Titan I utilized radio-inertial command guidance. The inertial guidance system originally intended for the missile was instead eventually deployed in the Atlas E and F missiles. Less than a year later the Air Force considered deploying the Titan I with an all-inertial guidance system but that change never occurred. (The Atlas series was intended to be the first generation of American ICBMs and Titan II (as opposed to Titan I) was to be the second generation deployed). The Titan 1 was controlled by an autopilot which was informed of the missile's attitude by a rate gyro assembly consisting of 3 gyroscopes. During the first minute or two of the flight a pitch programmer put the missile on the correct path. From that point the AN/GRW-5 guidance radar tracked a transmitter on the missile. The guidance radar fed missile position data to the AN/GSK-1 (Univac Athena) missile guidance computer in the Launch Control Center. The guidance computer used the tracking data to generate instructions which were encoded and transmitted to the missile by the guidance radar. Guidance input/output between the guidance radar and guidance computer occurred 10 times a second. Guidance commands continued for the stage 1 burn, the stage 2 burn and the vernier burn ensuring the missile was on the correct trajectory and terminating the vernier burn at the desired velocity. The last thing the guidance system did was to determine if the missile was on the right trajectory and pre-arm the warhead which then separated from the second stage. In case of the failure of the guidance system at one site, the guidance system at another site could be used to guide the missiles of the site with the failure.

Titan I also was the first true multi-stage (two or more stages) design. The Atlas missile had all three of its main rocket engines ignited at launch (two were jettisoned during flight) due to concerns about igniting rocket engines at high altitude and maintaining combustion stability. Martin, in part, was selected as the contractor because it had "recognized the 'magnitude of the altitude start problem' for the second stage and had a good suggestion for solving it." Titan I's second-stage engines were reliable enough to be ignited at altitude, after separation from the first stage booster. The first stage, besides including heavy fuel tanks and engines, also had launch interface equipment and the launch pad thrust ring with it. When the first stage had finished consuming its propellant, it dropped away, thereby decreasing the mass of the vehicle. Titan I's ability to jettison this mass prior to the ignition of the second stage meant that Titan I had a much greater total range (and a greater range per pound of second-stage fuel) than Atlas, even if the total fuel load of Atlas had been greater. As North American Aviation's Rocketdyne Division was the only manufacturer of large liquid propellent rocket engines the Air Force Western Development Division decided to develop a second source for them. Aerojet-General was selected to design and manufacture the engines for the Titan. Aerojet produced the LR87-AJ-3 (booster) and LR91-AJ-3 (sustainer). George P. Sutton wrote "Aerojet's most successful set of large LPRE was that for the booster and sustainer stages of the versions of the Titan vehicle".Sutton, George P, History of Liquid Propellent Rocket Engines, Reston Virginia: American Institute of Aeronautics and Astronautics, 2006, , p. 380

The warhead of the Titan I was an AVCO Mk 4 re-entry vehicle containing a W38 thermonuclear warhead with a yield of 3.75 megatons which was fuzed for either air burst or contact burst. The Mk 4 RV also deployed penetration aids in the form of mylar balloons which replicated the radar signature of the Mk 4 RV.

Specifications

*Liftoff thrust: 1,296 kN
*Total mass: 105,142 kg
*Core diameter: 3.1 m
*Total length: 31.0 m
*Development cost: $1,643,300,000 in 1960 dollars.
*Flyaway cost: $1,500,000 each, in 1962 dollars.
*Total production missiles built: 163 Titan 1s; 62 R&D Missiles – 49 launched & 101 Strategic Missiles (SMs) – 17 launched.
*Total deployed strategic missiles: 54.
*Titan base cost: $170,000,000 (US$ B in )

First Stage:
*Gross mass: 76,203 kg
*Empty mass: 4,000 kg
*Thrust (vac): 1,467 kN
*Isp (vac): 290 s (2.84 kN·s/kg)
*Isp (sea level): 256 s (2.51 kN·s/kg)
*Burn time: 138 s
*Diameter: 3.1 m
*Span: 3.1 m
*Length: 16.0 m
*Propellants: liquid oxygen (LOX), kerosene
*Number of engines: two Aerojet LR87-3

Second Stage:
*Gross mass: 28,939 kg
*Empty mass: 1,725 kg
*Thrust (vac):356 kN
*Isp (vac): 308 s (3.02 kN·s/kg)
*Isp (sea level): 210 s (2.06 kN·s/kg)
*Burn time: 225 s
*Diameter: 2.3 m
*Span: 2.3 m
*Length: 9.8 m
*Propellants: liquid oxygen (LOX), kerosene
*Number of engines: one Aerojet LR91-3

Athena guidance computer

The UNIVAC Athena computer calculated ground commands to transmit to the Titan missile as part of Western Electric's missile guidance system. The Athena was the "first transistorized digital computer to be produced in numbers." It consisted of ten cabinets plus console on a 13.5 by 20 foot (4.1 by 6 m) floor plan. It used radar tracking of the missile to compute Titan flight data to the necessary burn-out point to start a ballistic trajectory toward the target. On-board Titan attitude control rolled the missile to maintain the missile antenna aligned to the ground antenna. Computer commands were transmitted to the missile from a ground transmitter a "quarter mile out" (). Completed in 1957, the Athena weighed .

The Athena computer used a Harvard architecture design with separate data and instruction memories by Seymour Cray