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Ed Kyle

Titan23B-08.jpg (19956 bytes)TITAN:  FLOWN VARIANTS
by Ed Kyle

Titan 23B-08 Launched Gambit-3 KH-8 1730 from VAFB SLC 4W on January 21, 1971.  Titan 3B was the most-flown, but least-known, Titan orbital variant.

"Baseball Card" type details of most of the flown Titan variants are provided in the following links, listed in approximate chronological order.

1.  TITAN 1

Titan 1, originally just "Titan", was developed as a back-up ICBM to Atlas. The Martin Company built a new factory and new static test stands for the struturally stable, RP/LOX fueled Titan in the Rocky Mountain foothills at Waterton Canyon, Colorado. Aerojet of Sacramento, California developed the first and second stage engines.

Titan 1 testing began in 1959 at Cape Canaveral. The first flight from VAFB was thwarted during a December 3, 1960 fueling test at the Operational Silo Test Facility when the missile elevator failed and the fully fueled Titan plummeted to the bottom of the silo, destroying all in a giant explosion. Redemption came on May 3, 1961 when Missile VS-1 performed the first successful launch directly from an underground silo at VAFB Silo Launch Test Facility, proving plans for Titan 2 deployment.

During 1962, 54 Titan 1 elevator-lift silos entered service in Colorado, Idaho, California, Washington, and South Dakota. One silo and Titan were destroyed in a 1962 explosion at Beale AFB. The remaining silos were taken off alert during the first two months of 1965.

Martin built a total of 163 Titan 1 missiles, including 101 operational types. A total of 67 test flights took place, including 20 from VAFB. Only about half were fully successful. I view Titan 1 mostly as a costly educational exercise for Martin Co. and the USAF.

A typical operational-type Titan 1 flight included a roughly 3.2 second ground run of the two LR87-AJ-3 LOX/RP-1 engines before liftoff, followed by a 137-ish second first stage burn. About 7 seconds before Stage 1 shutdown, the Stage 2 gas generator started. Its exhaust would travel through the four vernier nozzles, providing 642 pounds of thrust. The verniers were swiveled by servo motors for attitude control.

Staging involved the firing of four separation bolts and a 3 second burn by the two solid fuel separation motors. The LR91-AJ-3 Stage 2 "sustainer" engine started about 11 seconds after the gas generator started. Sustainer burn time was usually about 159 seconds (all burn times varied depending on target distance, etc.). After shutdown, the verniers thrusted for another 20 to 40 seconds, depending on the needed velocity trim. After vernier shutdown, the Mk 4 reentry vehicle separated, being spun up as it separated by a torsion spring.

Initial portions of the flight were controlled by the autopilot. A Bell Telephone Lab radio guidance system located in the forward adapter provided trajectory adjustments during the second stage of flight.

2.  TITAN 2

Titan 2 was a liquid fueled, storable propellant intercontinental ballistic missile. Capable of lofting a 3,800 kg Mk 6 RV with a roughly 9 Mt thermonuclear warhead nearly 10,200 km, it was the largest, heaviest, most-powerful, and probably most frightening, ICBM ever developed by the United States. The W-53 warhead was 7.5 times more powerful than today's most-powerful U.S. weapon.

Aerojet modified its Titan 1 engines to create more-powerful, but simplified engines that burned nitrogen tetroxide and Aerozine 50, a 50-50 mix of hydrazine and unsymmetrical dimethylhydrazine. These were hypergolic, storable propellants that were loaded into on-alert missiles for months at a time. Titan 2 missiles stood fueled and ready in underground silos, from which they could directly launch unlike Atlas and Titan 1.

Unlike Titan 1, the Titan 2 LR91-AJ-5 second stage "sustainer" engine only had one gas generator nozzle, which swiveled to provide roll control. Vernier thrust was provided after sustainer shutdown by two small solid motors in the propulsion section, which together provided 2,100 lbf thrust for up to 20 seconds. When commanded by the all-inertial guidance system, the vernier nozzles were cut to terminate thrust. Other small solid motors helped separate the second stage from the reentry vehicle.

First and second stage separation was the "fire-in-the-hole" type, with the second stage engine igniting immediately at stage separation. Blowout vents in the interstage provided a path for exhaust gases.

Martin manufactured 141 Titan 2 missiles at its Waterton plant during 1962-1967. Eighty-one Titan 2 ICBMs were tested between 1962 and 1987, with a higher success rate than Titan 1 had achieved. The program kept as many as 54 missiles on ready-to-fire alert in underground silos for more than 20 years.

Accidents involving Titan 2 silos or missiles killed at least 58 individuals, including 53 in a single 1965 silo fire near Little Rock, Arkansas that was the USA's "Nedelin Disaster" (though it did not involve the missile or its propellants). A 1980 explosion near Damascus, Arkansas destroyed a missile and its silo, tossing the 740 ton silo door 600 feet and throwing the W-53 warhead outside the complex fence line.


Titan 2 served as the Gemini Launch Vehicle, boosting 10 two-man crews into orbit during NASA's adventurous, fascinating, whirlwind Gemini program. Martin Company assembled 12 GLV's in its Baltimore plant, although the tanks were manufactured in Denver. NASA contemplated a "Titan 2.5" that would have used stretched tanks, but ended up using near-ICBM copies. Changes included a Malfunction Detection System, radio guidance replacing the heavier inertial guidance system, elimination of retro and vernier solid motors, addition of redundant flight control, electrical, and hydraulic systems, a new avionics truss inside the second stage, and a new Forward Skirt Assembly atop Stage 2. The first stage carried nearly 13,000 lbs more propellant on GLV than it did on 5,500 nmi ICBM flights, but tank size was unchanged.

NASA and the Air Force also made changes to fix a Stage 1 "Pogo" problem, a Stage 2 "hard start" issue, and a Stage 2 thrust reduction issue that appeared during the first two years of ICBM testing. The effort paid off with 12 successful GLV launches during 1964-1966. The first unmanned flight went to orbit with a spacecraft that was not designed to separate from the second stage. The second unmanned flight was a suborbital heat shield test. The subsequent manned flights pioneered in-space maneuvering, long flights, EVA (for the U.S.), rendezvous, and docking - with Agena targets launched the same day on the same range. They also tested 16 astronauts (4 flew twice) who were all subsequently assigned to Apollo. Six of them walked on the Moon.

4.  TITAN 3A

Titan 3 originated in part from a series of USAF "Phoenix" launch vehicle studies in 1960-61. An idea to add large solid motors to modified Titan 2 missiles quickly gained favor and was approved as "Titan 3" on October 13, 1961.

Titan 3 would be "standardized" and "flexible" and "low cost", using all of the McNamara era buzz words. The modified Titan 2 core (Titan 3A) could be topped by an Agena third stage (Titan 3B) and, on heavy-lift missions, would be launched by twin 120 inch diameter segmented solid motors (Titan 3C without Agena, Titan 3D with Agena).

After detailed study, Agena was dropped from the plan in March 1962 in favor of a new Transtage powered by two Aerojet AJ10-138 pressure-fed engines. Nomenclature changed as Titan 3A became a three-stage test vehicle topped by Transtage and Titan 3C became a Titan 3A with a twin solid motor first stage. Launch Complex 20 was modified to support core-only Titan 3A tests, which were to precede Titan 3C flights.

The Titan 3A core stages were nearly the same dimensions as the Titan 2 stages, but used thicker, heavier tank walls and skirts. Interstage fire-in-the-hole exhaust ports were expanded. The second stage fuel tank stretched to carry more propellant. It expanded a few inches into the between-tanks space that had formerly housed the avionics truss, eliminating a need to actually "stretch" the stage. Avionics moved to the top of Transtage. The Titan engines were similar to those on Titan 2, but the first stage was set up to support air-starting on Titan 3C.

Transtage was a skin and stringer aluminum shell supporting two titanium propellant tanks, the two engines, an attitude control system module, and a control module with the guidance system. It was designed to restart at least three times. The stage was tested on the Denver stands and in Arnold Research Center's vacuum chamber.

Four Titan 3A launches took place during 1964-65 from LC 20, even as early Gemini Titan 2 missions were flying from LC 19. Transtage failed during the first flight when a "bang-bang" solenoid controlled helium pressurization system valve failed 15 seconds before the planned 391 second long direct ascent burn was to end, preventing orbit. The remaining missions were successful. The third launch by 3A-3 performed the first 3-burn upper stage mission in history to reach a 1,500 nmi orbit with LES-1. Transtage is still up there, though apparently now in pieces.

After the successes, a fifth planned Titan 3A test was canceled and the core reassigned to the Titan 3C program. Titan 3A never flew again, but its first two stages, and its LC 20 launcher equipment, were reassigned to a new "Titan 3B" program at Vandenberg AFB. Titan 3B reverted back to the original Agena upper stage idea that was more efficient and lower cost for its payload class.

5.  TITAN 3C

Two UTC 1205 five-segment solid rocket motors added to a Titan 3A core created Titan 3C, the R&D version of what would become the USAF workhorse. The solid motors acted as a "zero stage", with the core air-starting shortly before the solids burned out and separated. A "boat tail" and thermal protection covers were added to the base of the first stage and its engines to handle solid motor plume re-circulation. From 1965 through 1969, 13 R&D Titan 3C launches were performed from the vastly overbuilt ITL complex at Cape Kennedy. A 14th Titan 3C flew operationally in April 1970, still using the original LR87-AJ-9 and LR91-AJ-9 engines. Subsequent Titan 23C vehicles used improved LR87-AJ-11 first stage engines and, later, L91-AJ-11 second stage engines.

Three of the first five Titan 3C flights ended in failure (two Transtage and one payload fairing), but design changes were made and the remaining launches succeeded. Titan 3C-9, the memorable sixth flight, carried a Manned Orbiting Laboratory (MOL) simulator and three small satellites to low earth orbit in 1966, but not before dropping off a Gemini capsule (refurbished Gemini 2) on a suborbital "Heat Shield Qualification" reentry test to Ascension. The MOL simulator, built around a Titan 1 first stage oxidizer tank, remained attached to Transtage during its three-burn, four-orbit mission.

The final three Titan 3C vehicles used operational-type tri-sector fairings. Note that the numbers given on this card are mostly from a 1968 guide. Masses and performance varied during the development phase as mass reductions occurred.

Titan 3C-7, the first Titan 3C, launched on June 18, 1965 from LC 40, carried the-then heaviest-ever payload to orbit - a 9,694 kg mass, after a single burn by the Transtage. The Apollo boilerplate/Pegasus combinations orbited by Saturn I by that time only weighed around 6,500 kg. Proton had yet to fly.

Titan 3C-11, launched on June 16, 1966 from LC 41, was the first to achieve three good Transtage firings on a long-coast mission that put seven IDSCP satellites into near-GEO. Advanced Vela missions also used three burns to reach roughly 16,700 x 111,100 km orbits. No other upper stage of this time could perform such complex and varied missions, with Transtage able to live for up to 6.5 hours. The USAF gave up performance when it chose a pressure-fed, hypergolic propellant upper stage, but it gained function and reliability.

At first, Titan 3C/Transtage could only lift 544 kg to GEO, but by the end of the R&D program the vehicle could lift 896 kg. The number would pass 1,000 kg with early Titan 23C/Transtage vehicles, and keep rising to 1,460 kg before Titan 34D took over.


In early 1960, Martin Company studied Titan 1/Agena as a potential MIDAS launch vehicle. By mid-year focus shifted to the then-conceptual Titan 2 and the yet-to-fly Agena B. Study showed that Titan 2/Agena B might be able to lift 4,000 kg to LEO from Cape Canaveral or 3,650 kg to near-polar orbit from California. The faltering MIDAS program squelched the idea, but Titan/Agena remained a Titan 3 program baseline until March 1962 when Transtage was approved instead.

In mid-1964, the U.S. Air Force Systems Command, Space Systems Division (AFSC/SSD) defined Titan 3X/Agena D to launch National Reconnaissance Office Gambit-3 (KH-8) spy satellites. General Dynamics Convair Division, loath to loose its Atlas Agena Gambit launching business, proposed an Atlas SLV-3X alternative. SSD determined that SLV-3X would cost less than Titan 3X, but went with Titan 3X for its Titan 3C/3M synergy and for its low-risk development.

By year's end, Titan 3X/Agena D was specified to use the first two stages of Titan 3A topped by an Agena adapter and an Agena D/Gambit-3 spacecraft. Inertial guidance was replaced by radio guidance, On January 8, 1965, 24 Titan 3X/Agena D launch vehicles were ordered from Martin and Lockheed.

The program soon took on the name "Titan 3B/Agena D". Development proceeded quickly. Point Arguello LC 2-3 (today's VAFB SLC 4W, built to handle Atlas Agena beginning in 1963) was modified for launches using equipment stripped from the mothballed Titan 3A pad at Cape Canaveral LC 20. Martin completed its first Titan 3B core at Denver on Janaury 19, 1966. The company finished structural testing on the skirt and Agena adapter by March. On May 8, the booster arrived at VAFB. The Agena, or "Satellite Control Section", was mated two days later for development testing.
The Gambit-3 "Photographic Payload Section" was then mated and tested.

On July 29, 1966, the first Titan 3B/Agena D successfully reached a 158 x 250 km x 94.1 deg orbit - the first Titan launch to orbit from Vandenberg AFB. Agena fired once on the way up, then remain attached as a satellite bus, providing periodic orbit adjustments with its secondary propulsion system. Payload mass is typically listed at 3,000 kg for these missions, but orbited mass was probably 3,600-3,700 kg including the Agena and propellant for orbit maneuvers. These early "Block 1" Gambit-3 battery-powered satellites exposed film for about 10 days before the single Satellite Recovery Vehicle (SRV) jettisonned, fired its retrorocket, and reentered with film for air recovery. Agena would then fly solo for a few days before firing its engine to reenter.

Twenty-two Gambit-3 launches took place during the next three years. Only one, the fifth launch onApril 26, 1967, failed to reach orbit. That one suffered low thrust during second stage flight,possibly due to a blocked fuel line. The sixth flight lost part of its second stage engine's ablative skirt about 60 seconds into its burn, but the engine kept firing. Gambit-3 made it to an orbit with a lower than planned apogee. Several days later, Agena made up the difference and the mission continued.

Titan 3B was replaced by Titan 23B, which used upgraded engines, before the end of 1969.


Titan 23B was a Titan 3B with upgraded engines. LR87-AJ-11, developed for the soon canceled Titan 3M MOL program launcher, replaced LR87-AJ-9 on the first stage. LR91-AJ-11 replaced LR91-AJ-9 on the second stage (though there are hints that AJ-9 engines may have flown on some of the 23B second stages). The slight liftoff thrust increase, and more importantly the ISP increase, allowed Titan 23B/Agena D to boost the first nine "double-bucket" Gambit-3 missions during 1969-71. In addition to a second SRV, these Block 2 Gambit-3 satellites had more reserve attitude control propellant and an extra battery, allowing them to orbit for up to 19 days.

The big ablative engine skirts added nearly 20 inches to the engine length compared to the AJ-9 engines. The second SRV, in turn, added nearly 20 inches to the top of the payload. Otherwise, Titan 23B/Agena D shared the Titan 3B/Agena D dimensions.

8.  TITAN 23C

Titan 23C was a Titan 3C with upgraded core stage engines, operational payload fairings, and other changes. The air-lit core first stages were all powered by LR87-AJ-11 engines, with 15:1 ablative skirts added to improve efficiency. The same engines powered the Titan 23B first stage, but with slightly shorter 12:1 skirts to improve sea-level efficiency. Improved LR91-AJ-11 second stage engines began flying in 1973, helping to improve GEO performance to 1,461 kg (3,220 lb). The solid motors used an improved, lighter blow-down TVC system, with shorter TVC fluid cylinders. The Transtage attitude control system was modified to a blowdown hydrazine monopropellant system using 12 Rocket Research Corporation MR-3A 120N thrusters mounted in six clusters. The guidance system was improved. These and other changes gradually slashed Transtage dry mass. Improved performance eliminated the need for Transtage to fire to reach the initial parking orbit on GEO missions.

During 1970-1982, 22 Titan 23C vehicles flew from Cape Canaveral (Cape Kennedy 1963-73) Launch Complex 40. They launched ten Defense Support Program (DSP) early warning, fourteen Defense Satellite Communications System 2 (DSCS 2), and three Chalet/Vortex signals intelligence satellites toward planned geosynchronous or near-geosynchronous orbits. One flight boosted two Lincoln Experimental Satellites to GEO along with two Solrad satellites that subsequently lifted themselves to 118,000 km orbits. Another flight placed NASA's landmark Advanced Technology Satellite 6 (ATS 6) into GEO in 1974.

Three launches failed. DSP 1 was left in a subsynchronous orbit after the Transtage guidance system was misaligned, causing improper attitudes during its burns on the 3C-19 mission on November 6, 1970. Four DSCS satellites were lost in pairs when 3C-25 suffered a guidance platform power loss at Transtage staging on May 20, 1975 and when the 3C-35 second stage had a hydraulic pump failure on March 25, 1978.

The Chalet/Vortex SIGINT satellites flew beginning in 1978. They likely rode in 40 foot long fairings.


Titan 33B and its Ascent Agena stage remain a bit mysterious. Three flew, with two successes, during 1971-73 from VAFB SLC 4W. Two successfully injected payloads into Molniya orbits. The failure likely involved the Agena stage. Ascent Agena, whose development was funded in 1968, was a light-weight, stripped down Agena D, shorn of systems needed for extended Gambit-3 missions among other changes. It was used as a third stage from which its spooky payload separated upon orbital insertion, likely after two burns.

Agena and its payload were housed inside a really long shroud built by Lockheed or Martin, a completely different animal than the McDonnell Douglas shrouds built for Titan 23C. Some 45 years later only one night launch photo is publically available. It shows only hints of the shroud, which looks to be probably more than 58 feet long including the part that housed Agena.

The payload or payloads was likely a SIGINT, possibly named Jumpseat, apparently from NRO Program AFP-711. Given the big shroud, it probably had a really big antenna, or antennas. Hughes Aircraft was the likely builder of what was likely a spin-stabilized satellite based on the HS-318 bus, first flown as TACSAT.

10.  TITAN 3D

Titan 3D (23D) was essentially a two-stage Titan 23B launched by a 2 x UTC 1205 solid motor "zero stage". Like 23B, it sprang from the "Titan 3X" studies. Like 23B, it used BTL/WECO radio guidance from a ground station that was about 13 miles north of Space Launch Complex 4. SLC 4 East, which shared a launch control center with 23B's SLC 4 West, was rebuilt from Atlas-Agena Gambit service for Titan 3D.

Like the Titan 3B vehicles, Titan 3D was enigmatic, with few vehicle photos available even today. The reason was that 3D was built to launch one of the nation's biggest (though worst-kept) secrets - the National Reconnaissance Office's HEXAGON KH-9 "Big Bird" film-return reconnaissance satellites. These bus-sized satellites, assembled by Lockheed, carried nearly 60 miles of film that was exposed in Perkin-Elmer cameras and returned in four McDonnell Douglas reentry vehicles on missions that lasted up to 9 months. Ground resolution was better than 2 feet. An Itek mapping camera with a dedicated fifth GE RV was present on some flights. With Martin Marietta and UTC building the launch vehicle, many of the nation's aerospace contractors were involved in this big program that may have cost $15-20 billion in today's dollars.

Titan 3D launched 17 HEXAGON missions into low sun synchronous orbits during 1971-1982. Lockheed built the big, more than 54 foot tall two-piece shroud that housed the satellites at launch, and that also housed them during the final stages of ground processing. A few years ago, when HEXAGON was partially declassified, we learned that part of the satellite itself, the five foot tall "Satellite Control Section", was visible at the base of the shrouds during launch. I've shown a "Big Bird" in my drawing but I'm not sure about the orientation, with now-updated orientation.

Beginning in 1976, Titan 3D also launched the first five KH-11 KENNEN electro-optical reconnaissance satellites, the start of a program that ultimately replaced HEXAGON. KENNEN is still classified.

Titan 3D was 100% successful in 22 launches, as far as we know.


After Manned Orbiting Laboratory (MOL) and its Titan 3M launch vehicle were cancelled in 1969, parts of the nearly ready-to-fly rocket were adapted by other Titans. The 7-segment SRBs, test fired four times, would end up powering Titan 4A during the 1990s. The AJ-11 series core stage engines saw use much sooner when they began powering Titan 23 series vehicles in 1969.

Then, on August 12, 1971, the stretched Titan 3M first stage itself flew, powering the first Titan 24B/Agena D from VAFB SLC 4W with the 32nd Gambit-3 reconnaissance satellite. Twenty two more similar Titan 24B launches took place from the same pad through 1984. The stage, stretched about 71 inches, could carry 15-20 more tonnes of propellant to exploit the higher thrust engines. Accounts of liftoff thrust vary from 437 Klbf to 463 Klbf. I suspect that thrust and propellant loading grew over time, as Gambit-3 progressed from Block 2 to Block 3 and Block 4. I also suspect that the first stage never flew fully loaded on these "core only" launches. The second stage remained largely unchanged.

On its third flight, the Titan 24B Agena stage began using High Density Acid (HDA) to improve specific impulse. This and other changes boosted payload by about 160 kg. The stretched first stage would eventually add another roughly 550 kg. Gambit-3 exploited the capability by adding batteries, solar panels, and more film, along with more Agena on-orbit propellant to stretch the two-bucket missions from 20 to nearly 120 days, with one of the final missions attempting "dual mode" work in low and high orbits [Edited Feb 24, 2016].

On May 20, 1972, the fourth mission suffered an Agena pneumatic regulator failure during ascent that caused loss of control gas. A stable orbit was not achieved. Pieces of the highly classified satellite were subsequently found in England. The eighth launch on June 26, 1973 ended in much more dramatic fashion when a Titan propellant tank ruptured only 12 seconds after liftoff. Debris fell into the Pacific Ocean. For decades, the cause of this failure was hidden. To this day, no photos or videos have been released.

Then again, Titan 24B's numerous successes were also hidden. After the 1973 failure, 15 of them flew true before the program ended on April 17, 1984. Gambit-3's ground resolution, rumored to be the best ever achieved by the United States, remains classified.

The Titan 24/34B vehicles used the same umbilical tower as the shorter 23/33B rockets thanks to a shorter launch mount that lowered the engines that 70-ish inch distance, allowing the upper stages to maintain their stations.

12.  TITAN 3E

Titan 3E, NASA's "mighty Titan/Centaur", symbolized U.S. aerospace at its best during the 1970s. Here was a relatively cost-efficient marriage of storable USAF missile and NASA high-energy cryogenics that managed to create a high-performance, eye-pleasing rocket. Here were most of the big contractors working together under NASA's prodding to create a complex, but successful launch vehicle that made history.

In mid-1967, NASA began studying Titan 3/Centaur for deep space missions. At the time, Titan 3C was under development and Titan 3D was under study. Both were U.S. Air Force programs. The Agency decided on Titan during 1968, after budget cuts forced the end of NASA's Saturn programs. Lewis Research Center was given oversight. Contracts were awarded to Martin Marietta and General Dynamics/Convair by the end of 1969. Around the same time, NASA bought a Titan 3C for its Applications Technology Satellite (ATS), a mission that would fly in 1974.

By mid-1970, the new rocket was named "Titan 3E". It was a Titan 3D with a Centaur D-1T fourth stage and, on some missions, a TE-M-364-4 (Star 37E) fifth stage. Both the payload and Centaur were enclosed in a 58.48 foot long, 14 foot diameter, two-piece, Lockheed-built "Centaur Standard Shroud" (CSS). A "Titan/Centaur Interstage Adapter" tied Titan, Centaur, and CSS together. Lewis hosted a series of full-scale tests at Plum Brook to make certain that CSS would survive the ascent and jettison cleanly.

Centaur guidance replaced Titan 3D's radio guidance. Centaur was modified to provide long coasts and four or more restarts. Launch Complex 41 was modified to support Titan 3E. For a few years during the post-Apollo 1970s, LC 41 served as NASA's symbolic home-base.

The first Titan 3E (TC-1) rolled out to LC 41 on September 24, 1973. Its February 11, 1974 "Proof Flight" with a Viking mass simulator and a SPHINX research satellite failed when Centaur failed to start. RSO initiated destruct about 12.5 minutes after liftoff. An investigation found that the Centaur LOX boost pump failed to start when moisture froze in its turbine during LOX loading on the pad. The fix was to spin the boost pump turbines with cold-gas during cryogenic propellant loading.

All six subsequent Titan 3E launches, during 1974-77, succeeded, boosting two Helios satellites on sun-grazing 0.29 AU x 1.0 AU missions, the two Viking Mars orbiter/landers, and Voyagers 1 and 2 on historic missions to the outer planets. The Viking and Voyager pairs were impressively launched within 2-3 weeks from the same pad, which is an interesting story all by itself. Sadly, NASA's early plans for more Titan 3E flights were squashed by Shuttle.

Titan 3E's missions were landmark beyond measure. Two of those missions, the Voyagers, continue still, nearly four decades later.

Years after the final Titan 3E launch, by TC-6 of Voyager 1 on September 5, 1977, JPL's Bruce Murray and others disclosed that the launch had resulted in a "close call". The Titan 2nd stage had shut down a few seconds early due to a propellant management problem. Something like 1,200 lbs of propellant "outage" occurred versus the goal of less than 534 lbs at most. Centaur had to make up the velocity difference to the parking orbit. It then consumed nearly all of its propellant during its final burn to reach its planned velocity. In the end, Centaur had 3.4 seconds of propellant (less than 220 lbs) left in its tanks.

In the re-telling since, this story seems to have drifted a bit. Some versions blame a Titan propellant leak. Others say that the 1,200 lbs was the extra Centaur propellant burned. Murray's book and NASA SP-2004-4230 both say it was 1,200 lbs left in the Titan tank and neither mention a leak.

The Titan storable engines were "hydraulically balanced" and did not use active propellant utilization systems. Propellant management was by statistical analysis that determined how much fuel and oxidizer should be loaded for given ambient temperatures and expected system performance (mixture ratios and tank pressures especially). The goal was usually to run to oxidizer depletion with only 100 or 200 lbs of usable second stage fuel left as "outage". The expected second stage propellant burn rate was 323.42 lbs/second, but this usually varied a bit. Perhaps the TC-6 propellant loading was off for the conditions, or the engine mixture ratio shifted, or tank pressurization (autogenous) shifted. Only an official flight report could confirm the cause.


Titan 34B used the stretched Titan 3M first stage like Titan 24B and the 10 foot diameter shroud like Titan 33B. Titan 34B also used Ascent Agena inertial guidance, after flying in open-loop mode during the first 135 seconds, rather than the previous radio guidance. From 1975 through 1987 it flew 11 times, launching Jumpseat and Quasar (SDS) satellites toward Molniya orbits. There is uncertainty about which satellites were which, since they went generally to the same orbit type. SDS used shorter shrouds than Jumpseat, but launch photos are rare. Analysts, Space Track, NASA, etc.,
show competing satellite assumptions.

The April 24, 1981 Titan 34B launch (3B-60) is often, but not always, listed as a failure. Some records state that the satellite failed to separate from Agena. Others show a lower than planned apogee. Others show a good orbit and a successful launch.

Satellite Data System was used to transfer data from "low altitude photographic intelligence satellites" and ground control stations. These launches, which likely began in 1976, coincided with the appearance of the first KH-11 Kennen electroptical reconnaisannce satellites. Like Jumpseat, these first SDS craft were likely Hughes spinners.

Jumpseat and SDS masses are typically given as 630-700 kg, which is what that era's Hughes satellites weighed in GEO. Titan 34B with Ascent Agena was, however, capable of boosting perhaps 1,200 kg to Molniya orbit.

The final Titan 34B, 3B-66 launched on February 12, 1987, was the last flight of a Lockheed Agena stage. With something like 362 launch attempts, Agena remains the USA's most often-flown upper stage. It was also the 68th and final Titan 3B, the end of what seems to have been a very successful launch vehicle. A total of 69 Titan 3B cores were apparently built, which makes one wonder where that last one ended up.

14.  TITAN 34D

If Titan 3E symbolized U.S. aerospace at its best during the 1970s, Titan 34D came to represent the troubled 1980s.

Developed as a gap-filler until DoD Shuttle caught up, Titan 34D added one-half segment to the previously 5-segment solid motors and a stretched Titan 3M first stage. AJ10-138A ITIP (Improved Transtage Injector Program) engines powered the Transtage. Titan 34D could also use the new two-stage solid motor Interim/Inertial Upper Stage (IUS) that was being developed for Shuttle. Both upper stages provided inertial guidance for Cape Canaveral launches to GEO or near-GEO, replacing Titan 3C. A radio-guided No Upper Stage Titan 34D version replaced Titan 3D out of Vandenberg.

The first 34D boosted two Defense Satellite Communication Constellation (DSCS) birds to GEO from the Cape using the first IUS on October 30, 1982. It would be the last IUS on a 34D. The new Titan performed well at first with seven perfect flights, including three from VAFB. The Titan 34D-13 DSP 12 launch on December 22, 1984 was the 22nd consecutive Titan 3C/3D/3E/34D success.

Then Titan 34D-7 astonished by failing on August 28, 1985, losing a Kennen satellite from VAFB. One of the first stage engines shut down about 104 seconds after igniting. A propellant leak that began at SRM separation was suspected, but the cause was never pinpointed with certainty. Five months later, Shuttle Challenger failed. Then, on April 18, 1986 Titan 34D-9 blew itself to shreds above SLC 4E a few seconds after liftoff with the final Hexagon satellite. An insulation void in one of the solid rocket motors was blamed. Two weeks later, on May 3, Delta 178 failed with GOES G in the skies above Cape Canaveral. People wondered if the U.S. had forgotten how to launch rockets.

Procedures were added to X-ray all solid motor segments before stacking. After 18 months, Titan 34D returned to service with a successful Kennen launch, followed by a good DSP launch, but failure returned on September 2, 1988 when Transtage failed to restart at apogee, stranding a Vortex satellite in a useless transfer orbit. The pressure-fed stage had suffered a Helium pressurant leak that began even before its first burn.

The final three 34D launches were successful, with the last, 34D-2, orbiting a DSCS pair from the Cape on September 4, 1989. By then, Titan 4 had begun to fly.

Titan production had ended during the early 1980s. The Pentagon won authority to start what became Titan 4 during 1984, awarding contracts in early 1985. Still, there was a gap. It was a production and, likely, knowledge gap. This gap may explain the surge of mid-1980s failures. Another possibility is that complex Titan, with its multiple stages and contractor chains, was just randomly suffering a cluster of failures. What is certain is that three of 15 Titan 34D launches failed, which compares unfavorably to 15 failures in 123 launches by all of the solid-boosted Titans.

Titan 34D-2 was the last flight of a Transtage. A total of 47 flew on Titan 3A, 3C, 23C, and 34D during 1965-89. Six failed. Five of the failures were on the solid-boosted Titans, accounting for one-third of their total failures. On the other hand, Transtage accounted for six of the eight launch vehicle failures that occurred during the stage's 47 flights.


After Challenger, the U.S. Air Force moved payloads from STS to expendable launch vehicles. In late 1986, McDonnell Douglas, Martin Marietta, General Dynamics and Hughes Aircraft bid for the contract to launch the GPS constellation. Martin Marietta proposed an updated version of Titan 34D, confusingly named "Titan 3", that would presumably have launched two GPS satellites on each flight, the way they would have flown on Shuttle. Solid fuel perigee kick motors (PKM's) similar to those planned for the Shuttle launches would have boosted the GPS satellites from low earth orbit into transfer orbits. Martin Marietta also proposed a "Titan 3T" option that would have used Transtage.

The "Titan 3" design used the 5.5-segment Titan 34D solid boosters and first stage and a stretched (17 inch stretch) Titan 4 second stage with an attitude control system added to its forward skirt. Higher thrust Titan 4 "-11A" series engines powered the Titan stages. An inertial guidance system was installed in the Stage 2 forward skirt. An Ariane 4 type, 4-meter diameter Contraves payload fairing set up to carry single or dual payloads topped the rocket.

In mid-August 1986, President Reagan banned future commercial satellite launches on Shuttle. Martin Marietta, the only U.S. company with a then-active ELV production line (it was launching Titan 34D and developing Titan 4) soon offered "Titan 3" for commercial work. Before long the company had five firm launch contracts and options for a dozen more. But McDonnell Douglas's Delta 2 won the GPS (MLV) contract on January 21, 1987. "Titan 3" lost again a year later during bidding for the "MLV-2" contract won by General Dynamics Atlas 2.

"Titan 3", soon renamed "Commercial Titan 3", was left standing as the Pentagon game of musical chairs ended. The USAF wanted Titan 4, not Titan 3. Martin Marietta honored its commercial contracts regardless. Plans for a mid-1989 flight slid to year's end as the Titan 4 inaugural took precedence. The Commercial Titan 3 inaugural flight, from Cape Canaveral LC 40 on December 31, 1989, was highly successful, boosting JCSat 2/Orbus-7S and Skynet 4A/PAM-D2 into low earth orbit. The spin-stabilized PKM's took over from there, successfully powering both satellites to GTO. It would be the only dual-payload launch.

The second flight on March 14, 1990 was an embarrassing failure. The Titan second stage reached LEO, but the Intelsat 603/Orbus 21S combination would not separate from the stage due to incorrect deployment system wiring. It was the first single payload flight. The harness design error meant that the separation command went to a satellite that wasn't there rather than to Intelsat/Orbus. The 4,215 kg Hughes HS-393 satellite subsequently separated from the Orbus 21S motor and boosted itself into a safe low earth orbit. In May, 1992, the STS-49 crew captured the satellite and attached it to a new PKM, which boosted it to GTO. Intelsat 603 finally made it to GEO, where it served for 23 years before being decommissioned.

The third Commercial Titan 3 successfully launched Intelsat 604/Orbus 21S on June 23, 1990. It was the third Commercial Titan 3 flight in less than six months, hinting at what might have been. After the launch, LC 40 was closed for two years to be rebuilt for Titan 4. While Commercial Titan waited, the Cold War ended and the earth beneath the U.S. aerospace industry irrevocably shifted. When "CT-4" finally flew on September 25, 1992 with Mars Observer, which was successfully boosted toward Mars by its Transfer Orbit Stage, everyone knew it was the last Commercial Titan 3.

The idea of Commercial Titan 3 going head-to-head with Ariane 4 for commercial satellite business was compelling, but in the end Martin Marietta didn't have its heart in the fight. Titan 4 paid the bills, and Ariane 4, with its near-equatorial launch site, had orbital mechanics on its side.

16.  TITAN 23G

After Challenger, 14 recently decommissioned Titan 2 ICBMs were refurbished for use as orbital launch vehicles. More accurately, 14 sets of Titan 2 stages were harvested from the roughly 55 remaining missiles. Titan 2 modifications included replacement of the reentry vehicle adapter atop the second stage with a payload fairing adapter, the addition of a new 10 foot diameter payload fairing, refurbishment and upgrading of the inertial guidance system, and refurbishment of the first and second stage engines. The missile's solid motor vernier was replaced by four solid spacecraft separation retro motors.

A blowdown hydrazine monopropellant attitude control system (ACS) kit, similar to the Transtage system, was added to the second stage between-tank section. It was used on some launches to provide an orbit-insertion impulse at first apogee. On at least seven flights, Star 37-series apogee kick motors provided the insertion burn after the first two Titan stages performed a suborbital ascent. On these missions, the spacecraft (Landsat, DMSP, NOAA) provided attitude control during the coast and velocity trim after the solid motor burn.

Space Launch Complex 4 West at Vandenberg AFB, finished with Titan 34B in 1987, was modified to support launches. The first three launches during 1988-92 were classified. These are believed to have been P-11 5100 series Lockheed-built ELNIT satellites. Two ended up in 790 km x 85 deg orbits, but the second, launched September 6, 1989, failed to raise its orbit and decayed after one week. These Titans likely used ACS to inject satellites into roughly 250 x 800 km insertion orbits.

Landsat 6, launched on October 5, 1993, failed to reach orbit after the satellite's attitude control system hydrazine manifold ruptured, leading to a tumble during the Star 37 AKM burn. This was a suborbital Titan 23G ascent, with the AKM firing at the 740 km apogee.

The remaining nine Titan 23G missions went off without a hitch. Clementine 1/ISAS, launched January 25, 1994, was a highlight. Titan put the payload into a 255 x 299 km x 67 deg parking orbit. Eight days later, a Star 37 motor fired to boost the mission to a 168 x 128,095 km x 66.8 deg orbit. The spent motor and attached ISAS (Interstage Adapter Subsystem) separated to collect Earth radiation data for several months. Clementine 1 performed two Earth flybys to reach the Moon, where it fired its liquid motor to enter lunar orbit - the first U.S. lunar orbiter in more than a decade.

The final Titan 23G launch on October 18, 2003 came nearly 42 years after the first Titan 2 missile test and nearly four decades after the launch stages were manufactured. In 2005, the 14th, unused Titan 23G (tail number 23G-10) was donated to The Evergreen Aviation Museum in McMinnville, Oregon.

17.  TITAN 4A

The Titan 4A program began in 1985, when the U.S. Air Force won funding to develop a "Complementary Expendable Launch Vehicle" (CELV) as a back up to the space shuttle. General Dynamics proposed a 200 inch diameter Atlas "2"/Centaur G-Prime. NASA proposed SRB-X. Alliant Techsystems proposed a mostly solid motor family with a new high energy upper stage. In the end, Martin Marietta's Titan 34D-7 (later Titan 4) design won the contract.

The initial CELV contract, awarded during 1985, called for 10 launches from Cape Canaveral SLC 40. After the Challenger disaster the program was expanded to 41 launch vehicles to be launched from two pads at the Cape and from SLC 4E at Vandenberg AFB.

Titan 4A used, essentially, the seven-segment SRMs orignally developed for Titan 3M. The first stage was stretched 95 inches and the second stage 17 inches, compared to Titan 34D. Upgraded LR87/91-AJ-11A engines powered the core stages. All versious used inertial guidance. 

Multiple Titan 4 versions were developed. Transtage was replaced by IUS and Centaur T (G-Prime) on Cape launches. Three "No Upper Stage" (NUS) versions flew from Vandenberg and from Canaveral. Enormous 200 inch diameter payload fairings extended up to 86 feet, making the tallest Titan 4 stand nearly 62 meters (203.35 feet). With Centaur T, Titan 4A could put nearly 4.55 tonnes into GEO. Titan 4A NUS could loft 17.6 tonnes to LEO from the Cape or 14 tonnes to low near-polar orbit from California.

Titan 4A flew 22 times, with 20 successes, during 1989-1998, orbiting numerous high-priority national defense satellites, numbers of which had been designed to fly on Shuttle. It would be replaced by Titan 4B with upgraded solid rocket motors.

Titan 404 was a "No Upper Stage" (NUS) version that used a special mounting system for payloads that were originally designed to fly in the Shuttle payload bay.   This was called the Titan Payload Adapter (TPA).  It consisted of the boattail and base of the hammerhead section and was topped by a 50 ft fairing.  Titan 403   was a Vandenberg AFB NUS version that actually typically did fly with an upper stage that was considered part of the payload.  Titan 405 was 403's Cape Canaveral counterpart.  The differences between the two versions were due to the different arrangements of the launch pads.

There were detail variations for each Titan 4 version. The core stage thrust level differed for each version and solid motor propellant details may have varied.  Titan was straining to meet the Shuttle-type payload requirements at this point in time.

18.  TITAN 4B

From the beginning there were plans for advanced Titan 4 solid rocket motors. Hercules Aerospace won the SRMU (Solid Rocket Motor Upgrade) contract in 1987, beginning an odyssey that would see tragedy, explosions, delays, lawsuits, and the creation of the most advanced U.S. solid rocket motor yet to fly.

SRMU replaced the SRM steel cases with longer graphite composite cases. It used three segments rather than seven, with improved joints. Its internal propellant diameter increased from 120 to 126 inches. A hydraulic TVC system replace the older, less efficient fluid injection system. HTPB propellant replaced PBAN. Propellant loading increased. Dry mass fell. Specific impulse and thrust and burn time increased. With SRMU, Titan 4B could lift nearly 24% more payload to low earth orbit than Titan 4A.

Development was troubled. A September 1990 crane accident at Edwards AFB during a qualification segment lift killed a worker and started a fire that caused damage. When the preliminary qualification motor test was finally attempted on April 1, 1991, a violent explosion destroyed the motor and heavily damaged the test stand. After a design change and test stand rebuild, a successful test finally occurred on June 12, 1992. Four additional qualification motor tests then took place by September 1993.

Flight termination system development delays and other issues pushed back the first launch. It finally took place on February 23, 1997. In the end, only 17 Titan 4B launches occurred before the program ended in 2005. Two suffered upper stage failures (one IUS and one Centaur), but the SRMU and Titan stages worked every time. Titan 401B launched Milstar 2 and Orion satellites and sent Cassini to Saturn. Titan 402B orbited DPS early warning satellites. Titans 403B and 405B boosted big Lacrosse satellites to orbit from each coast. Titan 404B lifted KH-11s and something mysterious that may have been named Misty 2.

Hercules and Martin Marietta ended up suing each other in a fight over SRMU development cost recovery. The root issue was that far fewer SRMUs ended up flying than originally planned because far fewer Titan 4s flew than originally planned. All of this helped drive up Titan 4 per launch costs. Meanwhile, Alliant Techsystems merged Hercules Aerospace in 1994.

Titan 4B, the ultimate Titan, closed out 46 years of Titan flight history with a KH-11 launch from Vandenberg AFB on October 19, 2005. It was the 368th Titan launch, the 39th Titan 4, and the 123rd solid motor-boosted Titan.