On Sept. 23, the U.S. Navy fired 47 Tomahawk missiles on targets in Syria, part of the United States' response to the actions of the militant group ISIS.
From his home in Bluffton, Shelby Clark took in the news with a sense of accomplishment.
Although the function and technology of those recently fired Tomahawks have changed, it is still the same missile Clark helped design.
The dimensions are the same -- 20 feet long (18 feet without the booster) and 20 inches wide -- as the original specifications Clark wrote for nuclear-tipped Tomahawks more than 40 years ago.
Clark spent his career working on missile and rocket programs for the U.S. military, but the Tomahawk was one of the most prominent. In addition to outlining its specifications in 1974, Clark wrote the design-to-cost estimates in 1977 when the Navy began taking bids for the project.
Used in almost every major conflict since the Gulf War, Tomahawks were conceived as a long-range nuclear missile to be fired from a submarine.
Clark still has the reports he wrote outlining the Tomahawk. They include the diagram displaying how the missile would use a booster to break through the water upon exiting a submarine's torpedo tube, and how its wings would slide open once it reached a low altitude.
It's just one of many mementos he has from a 45-year career.
A Kentucky native, Clark considered becoming an engineer on the suggestion of his high school geometry teacher. Before that, the only kind of engineer he knew of directed trains, Clark said. At the University of Kentucky, it was a physics class that helped him realize that his future was in rocket engineering.
"On the first day, the professor said, 'Two-thirds of you will fail this class,' " Clark said. "And I aced it. It just flipped a switch in me."
After graduating from Kentucky in 1960, Clark worked for the Martin Co. in Orlando, Fla., on the team refining the Lacrosse, a U.S. Army missile fired from a truck and controlled by a forward observer in a Jeep. He also was on the team that developed the Bullpup, a Navy missile fired from a fighter jet and controlled by the pilot.
In 1963, he was transferred to the Sprint program, designing a short-range antiballistic missile to knock enemy missiles out of the sky.
For the Sprint project, he reviewed equations that would determine whether the missile would survive the stress placed on it at Mach 10. He still has the handwritten pages in a frayed folder in his office cabinet, yellowed by the passage of time.
Clark credits much of his later success to the man he worked under in the Sprint program, Bob Blanning. It was Blanning's review of him that later helped Clark become the civilian leader on the Tomahawk project.
Martin eventually made Clark the head of the Sprint program, and he shuttled between Orlando and Bell Labs in New Jersey, which participated in the missile's development. Clark left Martin for General Dynamics, where he worked for five years as a group leader on several missile projects. He led the operation team for the second Standard ARM missile, which used radiation from enemy radio signals to find targets.
In February 1973, after Blanning's good review, the U.S. Navy contracted with him to join the Tomahawk program. The missile was envisioned to have a range of 1,400 miles, allowing a submarine to fire a nuclear-tipped warhead at targets in the Soviet Union. Clark was brought onboard to determine if it was feasible.
That meant figuring out if the missile could withstand the shock of coming out of a torpedo tube and breaking through the water. It also required finding a tracking system for the missile, since satellites and GPS might be knocked out in a nuclear war, Clark said.
With fellow engineer Owen Holbrook and then-U.S. Navy Capt. Walter Locke, Clark traveled the country meeting with firms to find those answers. A booster solved the problem of generating the force to get the missile out of the water. A turbofan engine, similar to those in jets, could power the missile's flight to its target.
McDonnell-Douglas and General Dynamics both contributed parts for the missile, and Williams International built the turbofan engine.
To solve the tracking system problem, Clark met with a company in Texas that specialized in terrain contour matching. The technology allowed it to fly below radar at low altitudes and avoid obstacles.
In 1977, Clark was asked to write design-to-cost assessments for the missile. He compared them to a previous missile project he worked on, Harpoon, estimating they would cost a few hundred thousand dollars. By comparison, the 47 missiles fired in September cost about $1.5 million, Clark said.
"I wasn't going to overcharge," he said. "I got it back from the captain, and it was all marked up. I thought the captain hated it, that I was going to get fired. He loved it."
Clark's involvement with the Tomahawk program ended soon after he wrote its cost estimates. He joined Holbrook at Bird Engineering after the engineering phase began. With Bird and that company's successor, Technology Services Corp., he worked on software for the AEGIS missile defense system, evaluating the performance of the revolutionary radar program, TSC vice president Rick Siems said.
His biggest contribution to AEGIS was a logistics program called Nautilus that estimated the number of reserve parts needed for repairs, TSC program manager Rick Burnham said. Before Nautilus, those estimates were logged and calculated by hand. Clark was Burnham's mentor, his first employer after a 20-year career in the Navy.
"He taught me a lot about logistics," Burnham said. "As a weapons engineer, that was always on the other end of the spectrum."
Burnham is now working on a new model to replace Nautilus, which is still used today. He's now designing algorithms for the new program, a skill Clark helped teach Burnham when he joined the company.
Clark retired from TSC and permanently moved to Bluffton in 2005.
No longer nuclear, the Tomahawk missile used today has a heavier warhead and requires less fuel, giving it less range than was originally designed, he said.
Since the Gulf War, Tomahawks have been used in opening salvos during Operation Enduring Freedom and the invasion of Iraq and in response to the Bosnian War and the bombing of U.S. embassies in 1998.
"I can't believe it's been used that much," he said.
It wasn't until recently that he realized the impact of his career.
"It wasn't exciting," he said. "It was very boring in a lot of ways. I didn't think of it like that at the time, but now I see it was pretty remarkable."
Follow reporter Matt McNab at twitter.com/IPBG_Matt.