The U.S. Air Force’s last Titan rocket successfully launched from Vandenberg Air Force Base, Calif., Oct. 19, deploying a classified spy satellite and closing the book on a program whose history dates back half a century.

The first Titans were ICBMs, but the vehicle evolved into a space launcher, the Titan 2, whose cargo ranged from early Gemini astronauts to weather satellites. The Titan 4, representing the end of the evolutionary line, was used almost exclusively for launching the biggest and most expensive national U.S. security payloads, including top secret imaging and signals-intelligence satellites operated by the U.S. National Reconnaissance Office (NRO) and Air Force missile warning satellites.

The Titan 4 was a choice target of critics at times due to its high price tag and a rash of failures in the late 1990s, but the rocket is remembered primarily as the workhorse for the U.S. government’s national security space program. Standing more than 60 meters tall, the Titan 4 was capable of lofting more than 21,000 kilograms to low Earth orbit, and more than 5,700 kilograms to geostationary orbit, according to Lockheed Martin, the Titan prime contractor.

“The space age would not have been possible without it,” said John Pike, director of, a nonprofit group here that tracks defense programs . “All of your big reconnaissance satellites. All of your big [signals intelligence] payloads. Milstar. How can we think about the space age without it?”

Like most Titan 4 payloads, the last satellite carried aloft by the vehicle is shrouded in secrecy. But Lt. Gen. Michael Hamel, director of Air Force Space and Missile Systems Center, which procures military satellites and rockets, characterized it recently as “perhaps the most important” U.S. national security payload in the past 30 years.

The Titan 4 was conceived during the 1980s as an alternative to NASA’s space shuttle, which at the time was the U.S. government’s officially sanctioned space transportation system for all payloads. Then-Air Force Secretary and NRO Director Edward “Pete” Aldridge is widely credited for initiating the Titan 4 program.

Uncomfortable with the U.S. government’s reliance on a single vehicle for launching its national security satellites, Aldridge in 1985 ordered 10 Titan 4 vehicles — derived from the Titan 3 — from Martin Marietta Corp., now part of Bethesda, Md.-based Lockheed Martin. The next year, the Space Shuttle Challenger exploded upon liftoff, grounding the fleet for two years and resulting in a new policy that, in effect, dictated that operational military payloads fly on expendable rockets.

Peter B. Teets, who retired in April as undersecretary of the Air Force and NRO director, said Aldridge showed “remarkable foresight” in getting the program started.

“The fact is, after the Challenger disaster occurred, were it not for Aldridge’s desire for 10 Titan 4s, our national security space program would have ground to a halt,” said Teets, who pushed to keep two sources of rockets available for military satellite launches during his tenure as Air Force undersecretary .

Teets, who was at Vandenberg to witness the final launch, called the end of the Titan era “bittersweet,” noting that he worked on the Titan program following his freshman year of college. He crunched numbers on a calculator for engineers on the Titan 3 project, a job for which he was paid $2.10 an hour. Teets would go on to become president and chief operating officer of Lockheed Martin, a job he stepped down from following three Titan 4 failures in 1998 and 1999.

Of the 40 Titan 4s ordered by the Air Force, 39 were launched and four of those missions ended in failure. In part because of the huge investment in the payloads and the vehicles themselves, the failures made the Titan 4 a lightning rod for criticism. The Titan 4 also took heat because it was by far the most expensive expendable rocket in the U.S. fleet.

Cathy Bowers, an NRO spokeswoman, said the agency’s experience with the Titan program was “a great ride,” but added that the vehicle ultimately “became obsolete” due to its cost.

Pike said the Titan 4’s price tag soared in the 1990s following the end of the Cold War, as production rates fell to two per year amid a sharp decline in overall Pentagon spending.

The Titan 4’s high price tag was a major impetus behind the Air Force’s Evolved Expendable Launch Vehicle (EELV) program, which was intended to cut costs by using common hardware to launch all but the smallest of payloads. Before the EELV program, the Air Force relied on completely different rockets to launch its medium, intermediate and heavy payloads. The EELV program’s greatest cost savings were supposed to come at the heavy end.

Another factor in the Titan 4’s high cost was the nature and cost of its mainly classified payloads. Because these payloads were so complex and expensive, the NRO would take whatever time was necessary to iron out any technical issues that arose on the launch pad, often leading to costly delays.

An independent investigation into the failures of the late 1990s — the failures were not limited to the Titan 4 — led to a program designed to retain skilled Titan 4 workers as the vehicle’s retirement approached.

Jimmie Hill, a former deputy NRO director, praised those who stayed until the end. “It’s awfully tempting to want to bail out, and we owe them a lot,” he said.

Success on the final two launches was critical as the intelligence community moves to new generations of satellites and the Air Force begins using Boeing Co.’s Delta 4 heavy-lift rocket developed under the EELV program , Hill said. The level of risk rises any time the military begins using a new system, he said.

Thomas Marsh, executive vice president of Denver-based Lockheed Martin Space Systems, called the Oct. 19 launch “a fitting way to say goodbye to Titan.”

“The Lockheed Martin employees who have given their utmost efforts to the program over the years join with our Air Force and NRO customers, and the many other organizations that make up the Titan team, in expressing our great pride in this service to our country’s space program,” Marsh said in a company news release.