The agency has handed off rocket-building to private companies, retired it space shuttles in 2011 and now relies on Russian spaceships to transport American astronauts to and from the space station.

NPR: Space Station To Get $18 Million Balloon-Like Room

The report said that Nasa's space shuttles, designed in the 1970s, were not built to withstand bombardment by orbital debris because such objects were not then recognised as a substantial threat.

BBC: Was Columbia struck by space debris?

In 135 flights, as the five space shuttles collectively circled the Earth more than 20, 000 times, we learned about the physiology of humans in space and about the behavior of substances in near-weightless conditions.

CNN: Space is still the new frontier

The three surviving shuttles returned to space starting in 2005.

CNN: NASA, Texas towns mark Columbia disaster

The air lock installation is the primary objective of the Atlantis mission, with the two-room chamber allowing space station crews to venture from the station in NASA spacesuits without the assistance of visiting shuttles.

CNN: Air lock installed on space station