FORT CARSON, Colo. -- How many lifetimes does it take to become a Soldier, pilot, doctor, and astronaut? For Maj. (Dr.) Francisco Rubio, the battalion surgeon assigned to 3rd Battalion, 10th Special Forces Group (Airborne), it only takes one.Rubio recently took his place as one of only 12 Americans selected to begin NASA astronaut candidate training in August 2017."It's a dream come true," Rubio said.Rubio's desire to become an astronaut began after he attended a briefing on the NASA program during medical school more than a decade ago. Then, in 2015, he saw his chance. "NASA posted a Facebook release that they were going to be taking applications," he said.And with that, his journey to becoming an astronaut began.Rubio says he was a little daunted by the sheer number of applicants he was up against in the process. This selection cycle saw more than 18,000 applications from all over the country, an unprecedented amount. Historically, the typical number of applicants is around 8,000."If you're picking 10 out of 8,000 or 18,000, the odds are pretty slim anyways," said Rubio.During the selection process, Rubio reminded himself to temper his expectations."Honestly, you don't expect it," he said, "even at the very end... mostly because you look at the people around you and you're kind of amazed by them, too. You hope and hope, but you don't really expect it."As to what ultimately set Rubio apart from more than 18,000 other people, your guess is as good as his."That's the million-dollar question," he said.He explained that, although he felt his personality and teamwork experience played a big part, it really came down to what NASA needed from a new astronaut class at this particular time. He pointed out the incredible diversity among the twelve selectees, and that they all bring different, yet vital, skills and talents to the team.One thing is certain, however -- Rubio is immensely qualified for the job.Rubio graduated from West Point in 1998 and entered the Army, where he became a UH-60 Black Hawk pilot and flew more than 1,100 hours over the course of eight years. Of these flight hours, more than 600 were combat or imminent danger flight hours during deployments to Bosnia, Afghanistan, and Iraq.Rubio furthered his education and experience by attending and graduating from the Uniformed Services University of the Health Sciences in Bethesda, Maryland in 2006, and has served in the Army as a surgeon and physician since then.Rubio is looking forward to the next step on his journey by beginning his astronaut candidate training, which starts in August.The program is expected to last two years, during which time Rubio will take part in an academically-rigorous training focusing on spacewalks, robotics, international space stations, rocket systems, flying jet aircrafts, and Russian language courses."It's a once in a lifetime opportunity," he said.Rubio, who will retain his status in the Army and will become just the third member of the Army Astronaut Corps, acknowledges that the road to space is still a long one for him. After he becomes an astronaut, it will still be another five to eight years before he actually has the chance to go into space. But he's still energized to go through the process."It's going to be a really cool experience," he said. "The most inspiring thing about it is that it's almost universally supported in our country... you know you're kind of inspiring other people."In all, Rubio says he's proud and humbled to represent the nation doing something this spectacular. When looking back at all he's accomplished over the last 19 years in the Army, he attributes his success to good fortune, good timing, and seeking out opportunities for continued growth."I've been incredibly blessed," he said. "They [were] amazing opportunities... If it weren't for the Army, I wouldn't have had any of those opportunities. We're in an organization that lets you succeed."Asked to provide advice to Soldiers who are also looking to make the most of their Army experience, he says that the first and most important step is to apply for training or programs that interest them."There's a lot of people that have dreams and hopes," he said, "and they'll talk about them, but sometimes they just don't go through with finishing the application process. You never know unless you apply."The second piece of advice is to prepare to make mistakes -- and learn from them."As much as it sounds like I've had some great success," he explained, "I've also had some failures and I've fallen on my face. And sometimes that's the hardest part, and the part where you learn the most."Embracing success and failure equally as a part of the learning process has allowed Rubio to persevere and earn the accomplishments of several lifetimes.Now Rubio, already a soldier, already a pilot, and already a doctor, is on track to take his place as one of only 350 Americans ever to earn the title of astronaut.