Today’s report into the decisions that led to Nasa’s Columbia shuttle disaster will not pull any punches, officials warned.

A chunk of foam insulation fired at shuttle wing parts blew open a gaping 16 inch hole, yielding what one member of the Columbia investigation team said was the “smoking gun” that proves what brought down the spaceship.

A computer model that convinced Nasa the Columbia astronauts were in no danger from damage done to the shuttle by a piece of falling debris was outdated and lacked the right information, accident investigators said.

Nasa is making plans to return the space shuttle to orbit as early has the autumn and has instructed engineers to be prepared to make any “corrective actions” recommended by the board now investigating the Columbia tragedy.