NASA is considering attaching a Bigelow Aerospace inflatable module to the International Space Station, in a return to a concept the agency had more than a decade ago.

In 1997 the US space agency examined the possible attachment of its Transhab inflatable module to the ISS, but abandoned the technology project. Transhab would have been used for crew quarters.

Bigelow took the NASA Transhab technology and developed it for its own orbital complex concept and launched two technology demonstrators, Genesis I and II, which were successfully launched using Russian rockets in 2006 and 2007.

From 2012 Bigelow wants to lease to governments, companies and tourists the use of its private space stations for research and recreation.

In 2007 Bigelow Aerospace founder Robert Bigelow announced an $11.9 million price tag for four weeks at his space station in 2007 dollars, excluding the cost of transport.

However, internal NASA documents passed to Flightglobal show the US space agency is now interested in attaching a Bigelow module, but neither the company or NASA were available for comment.

The interest in the Bigelow technology follows NASA's decision to permanently attach its Italian-designed and built Raffaello multipurpose logistics module to the ISS.

Raffaello, expected to arrive in September 2010 on the final Space Shuttle mission, will be filled with spares to overcome problems with station logistics once the Shuttle fleet is retired.

In the Johnson Space Center's 8 September edition of its 8th Floor newsletter it is stated that Raffaello will be attached at the space station's Node 1 nadir port, which faces the Earth's surface.

The next major module for the ISS, Node 3, will be delivered in February 2010 and that is also to be attached to Node 1, also known as Unity.

Node 1 has six ports. Five are already in use, for the Z1 truss, the US laboratory module called Destiny, an airlock and two pressurised mating adaptors.

One of the adaptors links Unity to Russia's Zarya module while the other docks the Shuttle. Node 3, also known as Tranquility, will be docked to Node 1 and the Node 1 pressurised mating adaptor used for docking Shuttle will be attached to it instead.

Arriving in September 2010 Raffaello will take up the sixth port, which will be the nadir.