The first space launch era is quickly drawing to a close. The final "heritage" U.S. ICBM-based (Titan) launch vehicle lifted off from its Vandenberg AFB launch pad on October 19, 2005. The last heritage Atlas flew on August 31, 2004. (See launch list below).  Only Boeing's Thor-based Delta 2 remains, and its days appear to be numbered.

"Heritage" launch vehicles are the final derivatives of the original Cold War ballistic missiles developed by the United States and the Soviet Union during the late 1950s and early 1960s. These rockets, which carried names like Semyorka (R-7), Vanguard, Jupiter, Redstone, Atlas, Thor, Titan, Kosmos (R-12 and R14), and Tsyklon (R-36), were the original "space-age" machines. A few faded into history years ago, but 2004/2005 saw two significant departures - Atlas and Titan.

Thor

The departure of Atlas and Titan left only one remaining Heritage launcher: Boeing's Thor-based Delta 2. The U.S. Air Force plans to end use of Delta 2 after 2008, and United Launch Alliance has begun to restructure the program for lower flight rates.  One of the two active Cape Canaveral Delta II pads will be decommissioned after 2008.  NASA will continue to use Delta 2 for awhile, but the sturdy, reliable launcher is living on borrowed time. The U.S. Air Force has pressured NASA to shift Delta 2 payloads to the new EELVs.  According to Spaceflightnow.com, only 20 Delta II launch vehicles remained in inventory by the end of March 2008.   Seven more were expected to fly by the end of 2008, followed by an average of only four per year in 2009 and 2010. 

Titan

Titan closed out the heritage U.S. ICBM-based booster era. Titan, the second ICBM-based space launcher, was also used to orbit NASA astronauts during project Gemini. As with Atlas, the vast majority of Titan missions were unheralded unmanned flights. Unlike Atlas, which often worked for NASA or for commercial customers, most Titan launches carried secret defense-related payloads. The final Titan IVB variant used of a pair of massive Solid Rocket Motors (Upgraded) to boost a two-stage core Titan vehicle off the pad.

Titan 4B began flying in 1997.  It was boosted off the pad by two Alliant upgraded three-segment Solid Rocket Motors (SRMUs) that produced up to 770.98 tons of thrust each in vacuum.  The SRMUs attached to a two-stage, liquid propelled Titan core that retained the original Titan ICBM tank diameter.   The Titan core first stage was powered by an Aerojet LR87-AJ-11A engine, consisting of two independently operated sets of turbopump/thrust chambers mounted on a common frame.  The engines burned nitrogen tetroxide (N2O4) oxidizer with unsymmetrical dimethyl hydrazine (UDMH) fuel to produce a total of 249.98 tons of thrust in vacuum.  Gas generators drove the turbopumps.  The thrust chambers were gimbaled for pitch, yaw, and roll control.
 
The second stage used a single gimbaled Aerojet LR91-AJ-11A engine, with a single turbopump/thrust chamber.  Its main thrust chamber provided pitch/yaw control.  Turbopump exhaust passed through a rotating nozzle to provide roll control.   

The final Cape Canaveral Titan IVB launch occurred from Space Launch Complex (SLC) 40 on April 30, 2005.  SLC 41 formerly hosted Titan IV launches, but was converted for use by Atlas V in the late 1990s.  SLC 40/41 were part of Cape Canaveral's far flung "integrate-transfer-launch" (ITL)" system that was originally built during the early 1960s to handle Titan III.   Titan core vehicles were first assembled at the south end of the ITL complex in the four-bay Vertical Integration Building (VIB).  The vehicles were built up on one of several rail-mobile launch platforms, which straddled a pair of side-by-side standard gauge railroad tracks.  The platforms were pulled and pushed about ITL by twin diesel electric locomotives.  

When the core was assembled, it would be pulled from the VIB onto the ITL "main line".  After switches were thrown, the vehicle would then be pushed to the Solid Motor Assembly Building (SMAB), where the twin SRMs were added.  For the Titan IV program, SMAB was replaced by a new building, the Solid Motor Assembly and Readiness Facility (SMARF), that was designed to handle the new SRMU boosters. Finally, the vehicle would be pushed to one of the two launch pads, where it would be enshrouded by a massive Mobile Service Tower to allow payload installation.

During 2007, some of the old ITL facilities began to disappear while others were assigned new duties.  The VIB was dismantled, piece by piece, and reduced to a pile of scrap steel by year's end.  Meanwhile, SLC 40 and the SMARF were licensed for five-year use by SpaceX for its Falcon 9 launch vehicle.  The SLC mobile service tower was "imploded" with explosive charges for this purpose during on April 27, 2008, the umbilical tower having been previously removed.   The launch complex itself was being extensively refurbished for Falcon 9, which was not expected to fly until 2009 or later.

The very last Titan, Titan IVB-26, flew from Vandenberg Air Force Base on October 19, 2005. It was the 39th Titan IV launch and the 368th Titan flight overall. B-26 flew from a traditional fixed pad (SLC 4E) at Vandenberg.

The moniker "Titan", like "Atlas" a great name for a big rocket, has now been retired. Lockheed Martin choose to stick with "Atlas" for its new-generation Evolved Expendable Launch Vehicle (EELV).

Atlas

Atlas was the first big U.S.launcher derived from an intercontinental ballistic missile. Atlas was best known for boosting NASA's original Mercury orbital missions, but its most frequent duties were unmanned flights that involved use of Agena or Centaur upper stages. Atlas was the "balloon tank" missile. Its stainless steel propellant tank walls were as thin as a dime in some areas and had no internal structural support. Instead, the walls were supported by internal pressure, much like an unopened soda pop bottle.

Atlas was powered by a unique stage-and-a-half propulsion system that consisted of a jettisonable "booster package" with two powerful Rocketdyne (Y)LR89-NA5(7) engines positioned on each side of a less-powerful, but more fuel efficient at altitude, Rocketdyne (Y)LR-105-NA5(7) sustainer engine. Two small verniers, mounted on the side of the vehicle above the booster package, provided roll control and trajectory tuning. All five engines ignited on the pad.

Atlas III and Atlas V replaced the Atlas IIA Rocketdyne powerplants with a much more powerful and efficient RD-180 engine built in Moscow by Energomash. Atlas III, which itself was phased out with a final launch on February 5, 2005 (see list below), retained the balloon tanks, but Atlas V, with an all-new structurally stable first stage, is truly an "Atlas" in name only.

AC-164, launched December 2, 2003, was the last heritage Atlas of 284 launched from Vandenberg AFB/Point Arguello since 1959.  On May 14, 2004, Lockheed Martin rolled rolled out AC-167, the final Atlas IIAS, from its production facility near Denver. The rocket was shipped to Cape Canaveral on May 16. On August 31, AC-167 closed out the heritage Atlas program with a successful launch from Space Launch Complex 36A with a National Reconnisance Office satellite.

If my counts (based on Jonathan's Space Report Launch Vehicle Database at "http://www.planet4589.org/space/lvdb/index.html") are correct, AC-167, the last Atlas IIAS, was the 293rd heritage Atlas to fly from the Cape, and the 577th overall since 1957. It was also the 142nd Rocketdyne-boosted Atlas Centaur. I don't include Atlas III or Atlas V in these numbers, nor do I count non-launch on-pad or in-silo accidents, which destroyed five Atlas vehicles during the 1960s.

These missions spelled the end for both Rocketdyne MA-5A propulsion and for Cape Canaveral Space Launch Complex 36A, site of the first attempted and first successful launch of a hydrogen fueled upper stage on May 8, 1962 and November 27, 1963, respectively.

Pad 36A hosted the successful Atlas Centaur AC-10/Surveyor 1 launch in 1966, but was also the site of the Cape's biggest on-pad explosion on March 2, 1965.

That was when AC-5 suffered an improper RP-1 pre-valve closing two seconds after lift off, causing the booster engines to shut down. The 149 ton rocket then fell back through the launch stand into the flame trench, creating a huge fireball that put the pad out of commission for more than a year.

SLC 36B, unlike SLC 36A was modified to support Atlas III.  As a result, the "B" pad supported the final ballon tank Atlas launch on February 3, 2005. 

The umbilical and mobile service towers at both pads were scrapped in 2007.  Both mobile service towers were toppled by explosives demolition experts within a one hour period on April 16, 2007.  The concrete pad structures and the central blockhouse remain, but Altlas launch support hardware has been removed from them.  The future of this site is uncertain.   During the 2005-2006 period, SpaceX corporation investigated the site for its Falcon 5, but the company subsequently decided not to develop that launch vehicle.   Orbital Sciences was thought to have considered SLC 36 for its new Taurus II launch vehicle, but when NASA awarded COTS funding for Taurus II, Orbital announced that two-stage rocket would fly from Wallops Island.

The final heritage countdown list is presented below.

Heritage Atlas/Titan List

[1] SRMU segments expended at Hill AFB, Utah during 2006.  B-37 Titan core to be transferred to the U.S. Air Force Museum at Wright-Patterson AFB, Ohio.
[2] Transferred to Evergreen Aviation Museum in McMinnville, Oregon (home of the Hughes "Spruce Goose") for public display in 2005. Titan 23G-10, former Titan ICBM No. B-108, was refurbished during the 1980s for use as a space launcher. It was never assigned to a mission.

Atlas III

CC = Cape Canaveral, FL
VA = Vandenberg, CA