CAPE CANAVERAL, Fla. -- After building its new Orbital Space Plane (OSP) to ferry astronauts to Earth orbit and back, NASA very well may turn to its aging space shuttle fleet for continuing service as the nation's heavy-lifting, cargo-only launch vehicle.

"It's an area that we are looking at," Gary Martin, NASA's space architect in Washington, told SPACE.com. "But it's not the only one."

In the wake of the shuttle Columbia tragedy there is renewed debate about the future direction NASA will take, and what hardware the space agency needs to take it there.

Although not completely set in stone, it is extremely likely that any future launch vehicles NASA develops will divide the roles of lifting people and cargo into Earth orbit.

"It's always up for debate," Martin said, noting that launch vehicles such as the Atlas 5 and Delta 4 seem ideal to carry into orbit an OSP with astronauts aboard, while shuttle derived hardware might best solve the larger cargo needs.

"We are poised to make a much safer system now, a much more reliable system, based on new technologies. And at the same time bring down the overall costs," Martin said of the OSP specifically and NASA's space transportation needs in general.

Exactly how much any of these ideas will cost to build or operate hasn’t been determined yet, and support in Congress for programs such as the OSP is facing some challenges these days.

Martin said it’s likely that NASA isn't "articulating the vision very well. I think that what Congress is asking is how does (OSP) fit within the larger picture, and we're developing that."

"The United States, if it’s going to be a spacefaring nation, and it’s going to continue exploring the solar system, is going to need a reliable, upgraded system. The next step, past what the shuttle was in technology in order to keep moving forward," Martin said.

But if the OSP is adopted as the next piloted spaceship -- whether it's a winged vehicle or shaped like an Apollo-era capsule -- NASA still will need a way to lift large amounts of cargo into Earth orbit.

How much cargo?

Martin said some studies completed regarding a return to the Moon mission would require launching 265,000 to 440,000 pounds (120 to 200 metric tons) just to get the project started. The goal would be to launch that weight in as few missions as possible hoping to minimize risk and cost -- but there's no easy answer.

"We're looking all across the board. And shuttle derivatives are a very important part of that because, quite frankly, the shuttle has quite a lot of up lift capability," Martin said.

The space shuttle as it is today is designed to carry up to 65,000 pounds (29,480 kilograms) to a low inclination, low Earth orbit. That number quickly shrinks when flying into the higher inclination orbit where the International Space Station circles the planet.

By comparison, the most powerful version of the Atlas 5 is advertised as being able to lift 45,238 pounds (20,520 kilograms) to low Earth orbit.

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