This article originally appeared in the Oct. 8, 2018 issue of SpaceNews magazine.

Despite its reputation as a reliable workhorse, every Delta 2 launch campaign was unique.

“I can’t recall there ever being an attitude of complacency on Delta 2; be it at the factories or the launch site, not once,” Elizabeth Jones, Aerojet Rocketdyne program manager for the Delta 2’s RS-27A and AJ10 engines, said by email. “The commitment to continuous improvement and taking our time to get it right has always been at forefront.”

Before every launch, the Delta 2 rocket team would welcome the spacecraft team.

“It’s an interesting relationship,” said Bill Cullen, the ULA launch director who worked on Delta 2 throughout his career. “Collectively, we become one for the launch campaign.”

Cullen vividly remembers conversations engineers had with the scientists who devised NASA spaceflight experiments.

“Some of them worked for decades on the raw physics of their experiments,” Cullen said. “For some, it started as a thesis in graduate school that won research grants and finally led to a whole satellite experiment. It was exciting to be part of that.”

Cullen has been associated with the Delta 2 since he graduated from the University of Illinois in 1985. Then, it wasn’t Delta 2. It was simply McDonnell Douglas’ proposal for a Medium Launch Vehicle.

Many people worked on Delta 2 and its predecessor for decades. When Delta 2 flew for the first time in 1989, McDonnell Douglas had decades of experience building Delta rockets, said Tim Dunn, NASA launch director who worked as a Boeing Delta 2 guidance engineer in 1997. The experienced workforce and Delta rocket heritage contributed to Delta 2’s impressive track record, he added.

“Here they had a slightly larger vehicle, slightly larger strap-on solid rocket motors, a slightly more capable second stage engine and a larger fairing, but it was all incremental and evolutionary improvements to the existing processes and procedures that had been in place for almost 30 years,” Dunn said. “You had a tremendous amount of the same team, performing the same process. That was the entire backbone Delta 2 came into: an established launch team, established practices.”