The National Aeronautics and Space Administration says the test is a “confidence builder,” The Houston Chronicle reported. The caulk gun and the silicon goo were available for the last Endeavour mission but managers decided a gouge in heat-shield tiles did not need to be repaired.

The gun was developed after the 2003 Columbia explosion.

"We will finally get the ground truth on how this material behaves," Doug Parazynski, one of the Discovery crew set to carry out the test, said Friday.

NASA originally planned the test for next summer before a shuttle mission to the Hubble telescope. Those missions are riskier than the ones to the international space station because astronauts have no place of refuge if anything goes wrong.