NASA is reportedly taking part in a new project where it will employ two firms in the United States to create space taxis that will be used to transport astronauts to and from the International Space Station, according to program managers from the organization.

The space agency is looking to invest $300 million to $500 million in order to acquire these vehicles. The firms will be employed by NASA for 21-months under new partnership agreements, according to Ed Mango, manager of NASA's Commercial Crew program.

This program for building these space taxis is an attempt by NASA to build on investments already made in order to develop spacecraft specifically designed to transport commercial passengers.

Russia has been frequently sending out flying crews to the space station since the U.S. retired from doing so last year. The International Space Station is a hub for medical research. Russia charges NASA $60 million to fly a person out to the station.

The nation's spacecraft normally flies 240 miles above the Earth and carries a staff of six astronauts from various places including the U.S., Japan, China, Canada and Europe.

The firms who would be selected by NASA for the task would have to complete their designs for the taxis by May 2014. If the designs are approved, NASA plans to get the spacecraft off the ground for testing by 2015. They also must be made to carry four passengers.

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NASA has invested over $300 million in private companies that includes Boeing, Sierra Nevada Corp. and Space Exploration Technologies.

Sierra Nevada is currently developing a vehicle that features wings and is being called the Dream Chaser. Boeing is also working on a spacecraft known as the CST-100 which is actually a capsule made to fly around the Atlas 5 rocket already selected by NASA to fly cargo to the station.