The Titan III and its successor, the Titan IV, served the heavy-lift launch requirements of not only the Department of Defense but also for NASA especially after the retirement of the Saturn launch vehicles. Over the course of four decades and numerous upgrades, the Titan III and IV launched everything from constellations of spy satellites in Earth orbit to probes that have explored every planet from Mars to Neptune and beyond. Replaced almost a decade ago by modernized versions of the Atlas and Delta that are less expensive to fly, the Titan III still stands as one of the iconic American launch vehicles of the 20th century. And 50 years ago today, the first of almost two hundred Titan III and IV launches took place.

The Titan III Family

During the late 1950s and early 1960s, the USAF and Martin Marietta (one of the corporate antecedents of today’s aerospace giant, Lockheed Martin) performed a series of studies on the feasibility of adapting Martin’s Titan II ICBM for use as a satellite launch vehicle. One of the fruits of this effort was NASA’s selection of the Titan II as the Gemini Launch Vehicle (GLV) in October 1961 for their follow on to the Mercury program (see “The Mission of Gemini 1“). The USAF also sought to develop its own independent launch capability to orbit a growing list of defense-related payloads. On October 13, 1961 the Titan III was officially selected as the launch vehicle for the USAF.

The Titan III launch vehicle concept was based on a modular approach that could lift payloads into a variety of orbits and included a heavy lift capability that was, for political reasons, independent of NASA’s Saturn family of launch vehicles. Literally at the core of all versions of the Titan III was a modified two-stage Titan II ICBM that was structurally reinforced to handle heavier payloads and extra stages. Like the Titan II ICBM and GLV, the 3-meter in diameter Titan III core used nitrogen tetroxide as an oxidizer and a blend of hydrazine and unsymmetrical dimethyl hydrazine (UDMH) known as Aerozine-50 as a fuel. In addition to being storable (theoretically enabling the Titan III to remain fueled on the pad for a quick-response launch option), this toxic propellant combination is hypergolic or ignites spontaneously on contact thus simplifying engine design in the process.

The engines in the first two stages of the initial models of the Titan III were slightly modified versions of the ones originally employed by the Titan II ICBM and possessed the same performance characteristics. The 22.3-meter long first stage used a pair of LR-87-9 engines built by Aerojet (now part of Aerojet Rocketdyne) to generate 1,910 kilonewtons (kN) of thrust at sea level (the Titan II ICBM and GLV used LR-87-3 and LR-87-5 engines, respectively). The 7.9-meter long second stage employed an Aerojet LR-91-9 engine generating 445 kN of thrust. These two stages were employed in the first version of the Titan IIIB which was used primarily to orbit the KH-8 Gambit 3 spy satellites starting in 1966. The KH-8, whose design incorporated an Agena D upper stage for orbit insertion and in-orbit maneuvering, was too heavy for the Atlas and Thor rockets used to lift earlier Agena-based spy satellites and required the more powerful Titan IIIB.

While the Titan IIIB was capable of meeting USAF medium-class payload needs for low Earth orbit, an additional upper stage was required for higher altitude missions. To meet this requirement, a restartable third stage was developed by Martin Marietta called the Transtage. Like the first two stages of the Titan III, the 7.6-meter long Transtage employed Aerozine-50 and nitrogen tetroxide as propellants for a pair of Aerojet AJ10-138 engines. Similar in design to the larger AJ10-137 engine being developed by Aerojet at this time for the Apollo Service Module, this pair of gimbaled, pressure-fed engines had ablatively cooled thrust chambers and radiatively cooled nozzle assemblies generating a total of 71 kN of thrust. The Transtage carried a modified Titan II inertial guidance system to control not only itself but also the other Titan III stages during ascent. The Transtage was designed for up to 6.5 hours of autonomous operation in orbit with multiple engine restarts. The Transtage gave the Titan III flexibility in placing payloads in low, medium or high-earth orbits or even on escape trajectories. The launch vehicle consisting of the modified Titan II core with the new Transtage was designated the Titan IIIA. Theoretically the Titan IIIA, which was almost 38 meters tall, was capable of placing up to about four metric tons into low orbit or about a metric ton into a geosynchronous transfer orbit.

The largest member of the original Titan III family was the Titan IIIC. Added to the sides of the Titan IIIA were a pair of 3-meter in diameter solid rocket motors manufactured by United Technology Corporation. Consisting of five-segments each that were assembled near the launch pad, this pair of solid rocket motors made up “Stage 0” of the Titan IIIC and generated a total of 10,500 kN of thrust at lift off making the Titan IIIC the most powerful rocket flown at the time of its first flight in 1965. These solid motors would lift the Titan III core so that its first stage could ignite at altitude after Stage 0 burnout. The Titan IIIC offered the USAF a heavy-lift capability that could outperform NASA’s Saturn I by placing 13 metric tons of payload into low orbit (see “The Largest Launch Vehicles Through History“). In practice, the Titan IIIC, with its adaptable Transtage, was typically used to place lighter payloads into medium to high-altitude Earth orbits including up to about 1,600 kilograms into geosynchronous orbit.

The Titan IIIA Missions

The first member of the Titan III family to fly was the Titan IIIA. While the Titan IIIA could have been used as a medium-class launch vehicle in its own right, in the end it was flown only to support development of the Titan III rocket family. Just five flights of the Titan IIIA were initially planned in order to test the Titan III core and the performance of the new Transtage. After these test flights, the Titan IIIA would be retired and the focus would turn towards making the Titan IIIB and IIIC operational.

The first Titan IIIA test flight had the simple goal of placing a 1,700-kilogram cylindrical dummy payload into low Earth orbit – roughly the same mass as the Transtage would handle for typical Titan IIIC missions destined for high Earth orbit. For all five Titan IIIA test flights, Launch Complex 20 at Cape Canaveral, Florida was used. LC-20 had earlier supported 16 test flights down the Atlantic Missile Range of the Titan I ICBM (the antecedent of the Titan II ICBM) before it was transferred to space mission duties in 1962.

At 10:00:05 EST on September 1, 1964, Titan IIIA number 3A-2 successfully lifted off from LC-20. While the first and second stages operated as expected, the Transtage propellant tanks failed to pressurize as planned. As a result, the pair of pressure-fed engines on the Transtage shutdown 391 seconds into a planned 406-second burn. Because of this shortfall, the Transtage and the dummy payload failed to reach low orbit and arced back to Earth. Despite the failure to reach orbit, officials at the time stated that the first Titan IIIA mission had been “95% successful”.

The objective of the second flight of the Titan IIIA was identical to the first: test the core of the Titan III and the Transtage to orbit a 1,700-kilogram dummy payload. Upgrades were made to launch vehicle number 3A-1 including to the plumbing of the Transtage propellant tanks which were modified with a redundant set of helium pressurization valves. The second test flight lifted off from LC-20 at 11:52:33 EST on December 10, 1964. This time all three stages of the Titan IIIA operated as planned with the Transtage successfully placing its dummy payload into a 137-by-146-kilometer orbit inclined 32° to the equator. With its goals accomplished, the low orbit of the payload and Transtage quickly decayed and they fell to Earth three days later.

The next test flight of the Titan IIIA, using vehicle number 3A-3, would perform a more thorough test of the Transtage including its restart capability to deploy a satellite into a medium-altitude orbit. Instead of just a nonfunctioning dummy payload, this flight also carried an experimental communication satellite developed by the Massachusetts Institute of Technology’s Lincoln Laboratory located in Lexington, Massachusetts. The Lincoln Experimental Satellite 1 (LES 1) was a 26-sided polyhedron 61 centimeters across with a mass of 31 kilograms (a microsatellite by today’s definition). Its 18 square faces were covered with solar cells that generated 26 watts to recharge the batteries that powered the satellite while the other 8 triangular faces supported Earth sensors and antennas. Built by TRW, its mission was to test X-band communication technologies being considered for future DoD applications. Designed for a two-year mission, the LES 1 payload also included a Star 13A solid rocket motor manufactured by Thiokol that generated 6.2 kN of thrust to boost the satellite into its final orbit after being deployed from the Transtage.

The third Titan IIIA lifted off from LC-20 at 10:19:05 EST on February 11, 1965. The first burn of the Transtage successfully placed itself and its payload into a low parking orbit. After a coast of 90 minutes, the Transtage’s pair of Aerojet engines successfully reignited to raise the apogee of its orbit to 2,795 kilometers. After coasting for another orbit and a half, the Transtage reignited its engines again to circularize its orbit to 2,779-by-2,785 kilometers with an inclination of 32°. LES 1 was then deployed but its rocket motor failed to fire as intended because of an ordinance wiring error. Instead of being injected into an elliptical orbit with a 18,500-kilometer apogee, LES 1 was stranded in a lower 2,777-by-2,806 kilometer orbit. Since the rocket motor failure was a payload issue, this flight of the Titan IIIA was considered to be a complete success.

Despite the failure of Star 13A rocket motor to fire, LES 1 was able to gather some useful communication experiment data including voice transmissions. With the rocket motor still attached, the initial spin about the long axis of the combination eventually evolved into a end-over-end tumble that terminated normal communications experiments a few days after launch. Even though the on board timer ended all communications in 1967, transmissions from LES 1 were unexpectedly detected by radio amateurs in early 2013. After being silent for 46 years, apparently some component failure on the old satellite allowed power to reach its 237 MHz transmitter directly from the solar cells when LES 1 was in sunlight.

The fourth Titan IIIA test flight would provide the most thorough test yet of the Transtage capabilities this time carrying two payloads. The first was LES 2 which, with a mass of 37 kilograms, was a modified version of LES 1. Like its predecessor, LES 2 also carried an injection motor but this time a lower apogee of 14,800 kilometers was planned. The second payload, also built by Lincoln Laboratory, was called LCS 1 (Lincoln Calibration Sphere 1). The LCS 1 was a hollow aluminum sphere 1.13 meters across with a mass of 34 kilograms. The purpose of the LCS was to provide a passive orbiting target with a cross section of one square meter for radio and L-band radar system sensitivity calibrations.

Vehicle number 3A-4 lifted off at 10:00:03 EST on May 6, 1965. After the Transtage entered a low parking orbit, its engines reignited a total of three more times to place itself and its payloads into a nearly circular 2,780-kilometer orbit. Afterwards, LES 2 was deployed and this time its injection motor successfully fired to place the experimental communication satellite into a 2,782-by-15,067 kilometer orbit with an inclination of 31°. Next LCS 1 was deployed into a 2,779-by-2,795 kilometer orbit with an estimated lifetime of 30,000 years. The Transtage then continued coasting in orbit for another three hours to successfully test its 6.5 hour in-orbit lifetime.

With the successful completion of this fourth flight, all the objectives of the Titan IIIA test program were met. The modifications to the Titan II and the new Transtage all worked as intended. As a result, the USAF cancelled a fifth planned Titan IIIA flight and modified the remaining rocket for use as a core in a future Titan IIIC mission. Attention and resources now shifted towards the important first flight of the Titan IIIC which, for a time, would be the largest launch vehicle in the world (see “The First Missions of the Titan IIIC“).

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Related Reading

“The First Missions of the Titan IIIC”, Drew Ex Machina, June 18, 2015 [Post]

“The Largest Launch Vehicles Through History”, Drew Ex Machina, February 18, 2018 [Post]

“The History of American Rocket Engine Development”, Drew Ex Machina, June 9, 2014 [Post]

General References

David Baker, The Rocket: The History and Development of Rocket & Missile Technology, Crown Publishing, 1978

N. Cornwall, “American satellite starts transmitting after being abandoned in 1967”, Southgate Amateur Radio News, February 26, 2013 [Post]

J.D. Hunley, U.S. Space-Launch Vehicle Technology: Viking to Space Shuttle, University Press of Florida, 2008

William W. Ward and Franklin W. Floyd, “Thirty Years of Space Communications Research and Development at Lincoln Laboratory”, in Beyond the Ionosphere: The Development of Satellite Communications, SP-4217, NASA, 1997

“Lincoln Experimental Satellite”, TRW Space Log, Vol. 5, No. 2, pp. 39-41, Summer 1965