McGREGOR - The Marines have a saying that translates to the fast-paced work of developing rockets and forging a path toward colonizing other planets. Semper Gumby: Always flexible.

For one thing, the launch pad is an unpredictable place, with fires like one two weeks ago a concern. Then there's the technical challenge of achieving liftoff and propelling a rocketship through the heavens. And always, astronauts must be protected from radiation and other deep-space hazards.

As the commercial space industry assumes a larger role in the evolving national space race, one of its top private companies is finding military veterans an integral part of its workforce. At the SpaceX test facility in McGregor, a third of more than 550 full-timers have military backgrounds. Employees say they are used to mission-driven tasks.

"What more compelling mission is there than to make humanity an interplanetary species, right?" said Zachary Ledford, a former Army field-artillery officer who now works with SpaceX's human resources' data and automation team. "There's nothing else going on in the world right now that's more exciting and more compelling."

SpaceX, the Hawthorne, Calif.-based brainchild of a boundary-pushing billionaire, Elon Musk, and Blue Origin, founded by Jeff Bezos of Amazon.com fame, are among the biggest players working on powerful rockets for the next generation of space travel. Both have operations in this state, with SpaceX rooted in the Central Texas prairie.

Since 2003, Musk's company has steadily increased the size and workload at its McGregor test site, where it brings every one of its engines for testing. Technicians and engineers build and maintain 14 test stands that secure rocket engines for testing, diverting the flames into a concrete trench. They work with their counterparts in Hawthorne to turn big-picture ideas into feats of modern science.

"We're where the action is at," said Michael Adams, a Navy Reserve officer and a SpaceX build-reliability engineer. "There's a lot of test ops out here. We're firing off engines. We're firing off stages. There's a lot to be done out here."

Co-worker Joel Fecke likens the work to his critical high-tempo job in the Army overseeing maintenance of vehicles, weapons and equipment of a cavalry scout squadron.

"The way we work together as a team, it's really what speaks to the veterans," said Adams, who served aboard a nuclear-powered fast-attack submarine.

Dozens of missions

SpaceX has successfully launched 45 missions since 2008, when it made history by getting the first privately developed liquid-fuel rocket into orbit.

The rockets carry cargo into space for NASA, place satellites into orbit for commercial customers and complete national security missions for the U.S. government. First-stage boosters have successfully landed on drone ships or solid ground 19 times - another history-making feat for SpaceX - and three missions have reused one of the previously flown boosters.

"It is an optimistic time to be in the space industry," said Bill Ostrove, space market analyst for Forecast International, which provides consulting for aerospace and other industries. "There is a lot of capital and talent flowing into the industry right now. We're definitely seeing a lot of advances that haven't been made in a long time."

RELATED: After explosion, much is riding on SpaceX launch

The space industry received more than $2 billion in equity investment through the first nine months of this year, according to a report from Space Angels, a network of angel investors focused on early-stage commercial space investments. That includes personal investments from individuals in the business like Bezos, Musk, Robert Bigelow and Richard Branson.

A handful of commercial companies are launching payloads into orbit or developing rockets. Orbital ATK used a medium-lift rocket earlier this week to deliver cargo to the International Space Station as part of its contract with NASA. Blue Origin recently completed a hot-fire test of its BE-4 engine, which is capable of producing 550,000 pounds of thrust at sea level.

The BE-4 engine will be used to power Blue Origin's New Glenn rocket. The first-stage booster will have seven reusable liquid-oxygen, liquefied natural gas engines generating 3.85 million pounds of thrust.

SpaceX is developing a heavy-lift and super-heavy-lift rocket of its own. The Falcon Heavy will have 27 Merlin first-stage engines, three times more than the Falcon 9 that SpaceX is currently flying, fueled by liquid oxygen and rocket-grade kerosene. The engines combine for a total of 5.13 million pounds of thrust at liftoff.

"There's a lot of interest and a lot of excitement in this area right now," Ostrove said of overall launch vehicle development.

Musk is targeting Mars, ultimately. SpaceX is developing an even heavier-lift rocket, with new Raptor engines, that could one day reach the Red Planet. The vehicle is being called "BFR." With 31 Raptor engines on the BFR booster, it's expected to be more powerful than the Saturn V rocket that NASA used to propel astronauts to the moon.

The Raptor engines will be fueled by liquid oxygen and liquid methane, the latter being available on the surface of Mars for the return journey to Earth. Raptor engines have been tested for a total of more than 1,200 seconds of firing across more than 40 main engine tests.

SpaceX, Blue Origin and NASA are the main U.S. players developing heavy- and super-heavy-lift rockets, Ostrove said. The commercial companies, however, are taking opposite approaches to rocket development.

SpaceX has less powerful engines but is building more of them. The rationale is that more practice will accelerate learning and bring down costs, Ostrove said. Blue Origin is putting fewer, more powerful engines on its rockets. Its rationale, he added, is that fewer working pieces will make it easier to integrate the various rocket elements.

Blue Origin declined to comment for this article.

Ostrove said the big question moving forward is whether the market can sustain both companies. That will largely depend on their pricing to carry payloads to the moon, Mars or beyond.

"I think it's still very far out there, but we're a lot closer to have, sort of, an economy around these heavy-lift launch vehicles," he said. "We're probably closer to that now than we've ever been."

Quiet prominence

McGregor, near Waco, has quietly fulfilled an essential role for SpaceX over the past 14 years, becoming the company's second-largest location in terms of employees. Testing all those engines in preparation for their less-than-three-minute journey into orbit keeps employees at attention.

"We had a phrase in the Marine Corps that we used to use called Semper Gumby, which means 'always flexible,' " said Steve Fuchs, who used reverse-osmosis equipment to create clean drinking water for troops. "That's very much the same here at SpaceX. ... You may come to work thinking you're going to do a certain job, and that may change three times by the end of the day."

Fuchs, currently director of fabrication and support in McGregor, started working for SpaceX in 2005. He was living on the Kwajalein Island, in the Pacific Ocean between Hawaii and Australia, when the young company arrived with plans to launch rockets. Fuchs worked as a civilian contractor for the island's Army base, but he was immediately intrigued by SpaceX.

He soon got a job preparing the launch pad and helping integrate the rocket. But "everyone did everything" in those days, so Fuchs also captained the 40-foot catamaran that ferried employees to and from the smaller island where launches would occur.

He witnessed two liftoffs - neither completely successful - before moving to Texas in 2007. In the early days, most of McGregor's SpaceX employees worked out of an underground bunker, a vestige of the site's extensive history developing explosives and missiles.

The bunker had one restroom, a kitchen and offices. Fuchs recalled technicians working from two shipping containers pushed together. It was common for vehicles to get stuck in the mud and for the power to go out.

Much has changed. The original test stand, left behind by Beal Aerospace, has been augmented with one more closely resembling a launch pad. Multiple buildings spread across more than 4,000 acres house desks, work areas for technicians and rocket stages awaiting testing. That underground bunker is now a test control center.

Ups and downs

Complex systems are celebrated in the SpaceX Hall of Flame, with pictures depicting different iterations of engines undergoing testing. Employees' cubicles are adorned with mission patches of successful launches.

One notable Texas monument is the Grasshopper. Used to test guidance, navigation and control systems for landing a rocket booster vertically, the prototype's namesake comes from large, insect-like landing gear. The Grasshopper started with hops of only a matter of inches, but ultimately it flew half a mile into the air.

The celebrations of such successes also come with the recognition of setbacks. On Nov. 4, an engine caught fire during a qualification test that occurred before ignition. One test cell was damaged. No one was injured, and SpaceX doesn't expect the incident to affect its launch schedule.

The engine being tested was a Block 5 Merlin, and SpaceX rockets are currently using the Block 4 Merlin.

Testing of Block 4 Merlin and other engines has continued as planned. Such testing generally occurs twice a day, six days a week, so frequent that many employees hardly notice the noise. Yet some still go outside to watch. Fuchs can tell the type of engine and where it's being tested by simply listening to the sounds reverberating through his workspace.

Adams can watch second-stage tests from the window near his desk.

"I do take about 15 seconds," he said. "I lean back and I look at it. And I'm like, 'Yeah, that's cool. We do this for a living.' "

Adams was transitioning to the Navy Reserve and working on his master's degree in aerospace engineering when he stumbled across SpaceX. He had been interviewing with the more established space organizations and planned to be a company man.

"That's what space was. Space was the pencil ties and the pocket protectors," he said.

But as government funding dried up, the established aerospace players weren't able to pay for his level of experience. Adams stumbled across a SpaceX booth at a career fair. His quality assurance experience with high-risk submarine systems fit nicely with his current role of minimizing and eliminating risk while testing second-stage rocket boosters.

RELATED: Private firm leading new space pioneers

SpaceX recruits employees with the skills and drive for making humans a multiplanetary species, said Brian Bjelde, vice president of human resources. In a statement, he described veterans as "smart, passionate and driven individuals who are committed to achieving that mission and they bring a wide array of skills that can be deployed in so many of our roles."

Ledford, the former artillery officer, was recruited via LinkedIn while earning his MBA at Baylor University. His grandfather worked at Vandenberg Air Force Base, where SpaceX launches some of its rockets. As a kid, Ledford read books on solar systems and built rockets out of Legos.

"I really couldn't believe it," he recalled of the cold call from SpaceX. "I was trying to hold back excitement."

Fuchs said he can find himself talking about his job for hours with friends and family.

"I didn't join the company knowing we're going to get this far," he said. "So to be part of that journey, to see what we've done so far and then to know the potential of what we have to go, is just incredibly exciting."