The military's miniature space shuttle could pave the way for ships to fly cargo and crew to the space station.
The X-37B spaceplane, which is on its second flight, resembles a miniature space shuttle.
The vehicle could be used for cargo runs to the International Space Station.
The X-37B could be scaled up to accommodate five to seven astronauts.
The Air Force's secret miniature space shuttle sure has staying power. The spacecraft, known as X-37B, on Wednesday will surpass its 270-day orbital design life, with no sign of an imminent homecoming.
But could it have a new purpose as well?
The military won't say exactly what it's doing with the X-37B, which has been in orbit since March 5. The overall goal of the winged spaceplane is to give new technologies a test run in orbit.
Manufacturer Boeing has some other ideas. The company has been studying how to spin off the X-37B, also known as the Orbital Test Vehicle, into cargo ships and space taxis to service the International Space Station.
Unlike Boeing's CST-100 capsule -- one of four commercial space taxi designs backed by NASA -- the X-37B spinoff could make runway landings like the now-retired space shuttles.
"These vehicles could transport a mix of astronauts and cargo to the (space station) and offer a much gentler return to a runway landing for the space tourism industry," Arthur Grantz, Boeing's chief engineer for the X-37B, wrote in a paper obtained by Discovery News.
The report outlines two versions of the X-37B. The first would be the same size as the military's 29-foot vehicle and could be used to fly "high value" payloads to and from the space station.
"No new technology is required to build an X-37B customized to the (space station) cargo mission," Grantz wrote.
Larger versions of the spaceplane could be used to fly both cargo and crew to the station, as well as to other proposed orbital outposts, such as Bigelow Aerospace's inflatable habitats.
"The preferred size is approximately 160 percent to 180 percent of the current X-37B," the paper said.
The vehicles would carry between five and seven astronauts.
For now, X-37B managers are focused on the current flight.
"We are learning new things about the vehicle every day, which makes the mission a very dynamic process," Tom McIntyre, the Air Force's X-37 systems program director, wrote in an email to Discovery News. "We initially planned for a nine-month mission … but we will continue to extend the mission as circumstances allow."
The X-37B's debut mission ended with a touchdown at Vandenberg Air Force Base in California on Dec. 3, 2010, after a 224-day flight. That vehicle is in the process of being refurbished and is scheduled to launch again. A target date for the launch has not yet been released, an Air Force spokeswoman said.