Five years after the last manned NASA mission, the American space agency is preparing its astronauts for a mission to the International Space Station (ISS) once more. This time, they will be using a private spacecraft.

The last time NASA sent astronauts to the ISS on a manned mission was in 2011 when the Atlantis spacecraft lifted off from the Kennedy Space Center's launch pad in Florida. At present, NASA is either outsourcing its supply mission or paying Russia to fly their astronauts to the ISS.

The American space agency plans to keep outsourcing some of their space tasks. Doing so enables them to focus on sending astronauts beyond the Earth's orbit and eventually to Mars and other planets.

For these longer space journeys, NASA is currently building the Space Launch System and the Orion spacecraft. But at the same time, they are planning to send astronauts to the ISS onboard a private shuttle.

Sunita Williams and Eric Boe, NASA veteran astronauts, practiced docking the CST-100 Starliner spacecraft using touch-screen simulators. The private shuttle was made by Boeing Co.

"This is the next really exciting chapter for our country and our space program. It refocuses on what I think is really important - planning for the next generations and thinking of their future," said Williams.

The flight simulator, called the Crew Part-Task Trainer, helps teams prepare for several aspects of a manned mission such as flight conditions and ISS docking sequence. Williams and Boe's training on April 26 took place near the Lambert-St. Louis International Airport.

"Here [with the CPTT] you're not learning the full-up, if you will, muscle memory of where every switch is [located] and what each is going to feel like, but you're learning what the switches are, what the displays are, what they look like and what they do," said Boeing's space vehicle training programs manager Pete Meisinger.

Everything that an astronaut in space can hear, look and press is represented in the devices used in training, added Meisinger.

In terms of cost, it appears that taking the private route is cheaper. Shuttling astronauts through Russia costs $76 million for every ride. As for the American-operated private space shuttle, it costs only $58 million for every ride.