HOUSTON - Army Colonel Mark Vande Hei, a 1989 graduate of Saint John's University, is preparing for a trip of a lifetime.

After years of hard world and training, Vande Hei got news last summer of his assignment to take off for the International Space Station in March, 2017. It's his first trip to space.

"I still have this sense of disbelief that this is really going to happen. I'm just a normal person getting a lot of great opportunities. I think the first time I'll actually believe I'm being launched into space is when the rocket starts up."

He's assigned to International Space Station Expeditions 51 and 52 and is expected to remain in space for five to six months.

Vande Hei got a Bachelor of Science in Physics at Saint John's University, before getting a Master of Science in Applied Physics from Stanford in 1999. The thought of becoming an astronaut first popped into his mind 25 years ago, when he first joined the army. His boss noticed that he met the criteria and urged him to apply.

Vande Hei says he was excited at the time to chase the opportunity, but was sometimes unsure if he would make the final cut.

"It was very much an emotional roller coaster. There were times where I thought 'wow this could actually happen' and there were other times I thought there was no way they could give me this job."

He ended up making the final cut and was selected in June 2009 as a member of the 20th NASA astronaut class. He was one of nine selected out of thousands of applicants. Vande Hei completed astronaut candidate training in June 2011 to qualify for space assignments.

Since then, he's put in countless hours of training and preparation. Anything from underwater space suit training for six hours at a time, to learning the Russian language, so he can communicate with Russian counterparts (The total crew will be six people on board a Russian Soyuz capsule).

His main responsibilities on the Space Station will include maintenance and crew support, along with noting how his body reacts to being in space for almost half a year.

"We are really part of the experiment as well. There's a lot of questions about how to keep someone healthy in space. I'm also serving as the hands and eyes for some investigators on the ground who want to get some research accomplished."

Vande Hei says he's not sure if he'll get a chance, but that he'd love to do a spacewalk during his trip.

"Just to have nothing between me and the earth 240 miles below me, I think that would be an incredible experience."

You can follow Mark Vande Hei on his journey on his Twitter profile (click here).