COLORADO SPRINGS, Colo. — By the time United Launch Alliance’s corporate parents, Boeing and Lockheed Martin, tapped Tory Bruno to take over the government launch services provider last July, the handwriting was on the wall: ULA was going to need a new rocket if it hoped to remain in business for the long haul.

Congress by that time had drafted legislation banning future use of the Russian-built RD-180 main engine that powers ULA’s main workhorse, the Atlas 5. The measure, prompted by Russia’s annexation of Crimea from Ukraine, would become law by the end of the year.

Moreover, ULA soon would be facing stiff competition in its core national security market from Hawthorne, California-based SpaceX, the hard-charging rocket-making venture founded by tech billionaire Elon Musk.

By the time he officially replaced Michael Gass as ULA’s president and chief executive on Aug. 12, Bruno had done his homework. On his first day, he had a stark message for his new board of directors, composed of senior Boeing and Lockheed Martin executives: ULA needed a new engine, and needed it quickly.

It was not exactly a revelation. ULA in June announced it had put several companies under contract to study new engine concepts. Those companies, not named at the time, included Blue Origin, the secretive rocket venture owned by Amazon.com founder Jeff Bezos, and U.S. propulsion stalwart Aerojet Rocketdyne, which had been developing a kerosene-fueled, 500,000-pound-thrust concept known as AR-1.

But that meeting set into motion the sequence of events that culminated in ULA’s April 13 announcement that it would develop a rocket dubbed Vulcan using an incremental approach whose first iteration essentially is an Atlas 5 outfitted with a new first stage. The rocket, which has yet to be approved by ULA’s board, is slated to debut in 2019.

During the meeting, Bruno walked through the alternatives Denver-based ULA had studied to date, including the AR-1 and Blue Origin’s BE-4, the latter already being the favorite of one of his key deputies, George Sowers, ULA vice president for advanced concepts and technologies.

The board, which is chaired in turns by Rick Ambrose, executive vice president of Denver-based Lockheed Martin Space Systems, and Craig Cooning, president of Boeing Network and Space Systems of Arlington, Virginia, responded by telling Bruno to thoroughly examine every possible alternative.

In the following weeks, ULA executives examined about a dozen such concepts, including solid boosters, a Ukrainian option that was deemed too risky because of the proximity of its manufacturer to Russia’s border, and ideas from companies that Bruno said he had never heard of. ULA also considered a domestically produced RD-180, the possibility of which helped convince Pentagon skeptics in the 1990s that it was acceptable to have a mainstay military satellite launcher powered by a Russian-heritage engine.

Then there was the question of whether ULA’s other rocket, the Delta 4, could be transformed into a viable competitor to SpaceX’s Falcon 9 rocket. The Delta 4 is powered by an Aerojet Rocketdyne-built main engine and is the only launcher in the U.S. fleet with a certified heavy-lift version, needed to launch some of the Defense Department’s most critical and expensive satellites.

“We wanted to cast a wide net because picking that engine path was just extremely important to the future of the company,” Bruno said in an April 15 interview.

About one month after the meeting, on Sept. 16, ULA unveiled its choice: Blue Origin’s BE-4. The selection, announced by Bruno and Bezos in a Washington press conference, was a stunner, especially for Sacramento, California-based Aerojet Rocketdyne, which had billed the AR-1 as a relatively straightforward replacement for the kerosene-fueled RD-180.

ULA executives liked the AR-1, but “it wasn’t clear how that engine could be funded,” Bruno said, notwithstanding the fact that Congress by that time appeared ready to appropriate substantial money for work on an RD-180 replacement. “Even though it was a kerosene and a closer match to the RD-180 — it didn’t appear to have a timely availability because it hadn’t yet started and it had no funding,” he said.

Aerojet disputes that assertion, saying key AR-1 components and technologies have been in development for some time with a combination of government and corporate funding.

ULA officials nonetheless viewed the BE-4 as well ahead of the AR-1 in development, and the combination of that and the fact that it was funded by Blue Origin made it the clear choice. “We said it’s Blue. It’s clearly Blue. By a far margin,” Bruno said.

The decision still puzzles some industry observers, who note that BE-4 is powered by a different fuel than the RD-180 and thus will require developing a new first stage.

“We did enough work to know if you pick a Blue engine it’s a liquid-natural-gas fuel,” Sowers said. “The basic architecture was part of the trade.”

In the wake of the decision, Aerojet stepped up its internal investment in the AR-1, although company officials concede that U.S. government funding — Congress has allocated $220 million this year for engine development work — will be necessary to complete the project. Aerojet Rocketdyne also made an announcement of its own, saying it was working with ULA on AR-1 development.

ULA says it is keeping the AR-1 option alive in case the BE-4 runs into developmental difficulty.

ULA’s board, meanwhile, informed of the BE-4 selection, approved three months’ worth of investment funding and laid out a series of near-term milestones for ULA to reach.

“When Tory was named CEO, the board was aware of — and continues to support — the government’s goal of fielding an American-made engine as quickly and affordably as possible,” said Robert Sterling, a Boeing spokesman who responded on the board’s behalf to SpaceNews questions. “Tory has moved decisively to determine a strategy for supporting that goal and for meeting the government’s needs for assured access to space.”

Fast forward to ULA’s April 13 announcement, in which the company disclosed details about the Vulcan beyond the BE-4-powered first stage. The major elements of this evolution are a new upper stage, to be phased in in 2023, and first-stage engine reusability, to follow in 2024.

Plans for the Advanced Cryogenic Evolved Stage, or ACES, actually predate ULA’s 2006 creation — officials with Atlas 5 developer Lockheed Martin viewed it as the next step in that vehicle’s evolution. But with Russia’s incursion into Ukraine, “we had to do the [main] booster” first, Sowers said.

Initially, ACES was considered for both the Atlas 5 and Delta 4, but with the emergence of SpaceX as a legitimate rival ULA had to rethink the viability of maintaining two different launchers over the long-term. “You can’t carry two systems into a competitive environment,” Sowers said.

After internal debate, Atlas won out because of its lower cost.

Unlike the Delta 4, however, there is no Atlas 5 heavy-lift variant. “The solution was to put the bigger upper stage on the Atlas so that gave us the heavy capability,” Sowers said.

The ACES-equipped Vulcan, augmented by strap-on boosters, would have 30 percent more lift capacity than the Delta 4 Heavy, currently the largest vehicle in the U.S. fleet, Bruno said.

The Road to Reusability

The final piece of the publicly announced Vulcan architecture is partial reusability.

ULA had long studied reusability — in 2008, the company presented a paper at a conference in San Diego called “Partial Rocket Reuse Using Mid-Air Recovery” that appears to be the foundation for the current Vulcan concept. “Using helicopter mid-air recovery as the engine module descends under a parafoil is a low-development-cost approach which brings back the booster engine with exposure to only benign environments,” the paper said.

ULA refers to its engine reusability concept as Sensible Modular Autonomous Return Technology. After first-stage burnout, the two BE-4 engines would be severed from the fuel tank and deploy an inflatable heat shield to slow their descent. They then would deploy steerable parachutes, which would further slow their descent so they could be plucked out of midair by helicopter.

The reusability feature is especially important as engines make up about two-thirds of the rocket’s cost, ULA officials said.

“I felt it was going to take people a certain amount of time to understand the approach,” Bruno said. “We took a radically approach than the other guys.”

SpaceX also plans to reuse the first stage of its operational Falcon 9 and planned Falcon Heavy rocket, but its concept has the stages coming in for a powered vertical landing on a platform after launch.

During the interview, Bruno said the Vulcan roadmap actually runs through 2035 and includes several more iterations. Those steps, he said, are less firm than the new engines and reusability concept.

Of course, ULA still must convince skeptics that the Vulcan architecture as outlined April 13 is more than just a paper rocket. The push by ULA and its corporate parents for a relaxation of the RD-180 ban so that the company can continue to use the Atlas 5 — the Delta 4 is now designated for retirement — until the Vulcan is ready has only fueled that skepticism.

During Vulcan’s unveiling, Bruno said ULA is counting in part on the willingness of Boeing and Lockheed Martin to allow the company to use some of its profits, which currently go to the bottom lines of the corporate parents, to fund the rocket’s development.

So far, ULA’s board has limited its approval of Vulcan-related investments to quarterly increments. “We have made no long-term commitments on the funding of a new rocket, and are currently assessing all options,” said Sterling, the Boeing spokesman. “The board is actively evaluating continued investment in the new rocket engine program and will continue to do so.”