The STS-121 mission is still considered a test flight after trouble with the last flight that included heat-deflecting tile damage and the loss of foam off the external fuel tank. Engineers have since also replaced many of the gap fillers between tiles on the shuttle's belly. One of those gap fillers came loose during the 2005 mission and had to be removed during a space walk. This is Space Shuttle Orbiter Projects Office manager Steve Poulos.
"We ended up removing and replacing a little over 5000 gap fillers prior to this upcoming flight, and that's 5000 out of a little over 16,000."
Engineers have also replaced more than 240 of the heat tiles and 44 of the thermal protection blankets that shield parts of the shuttle from intense heat. In addition, a new, stronger tile, known as a BRI tile, is being used to protect crucial parts.
"This particular tile has a significant, and I would underscore significant improvement in terms of its damage tolerance, both for debris liberated by the vehicle as well as MMOD, on-orbit debris sources. Now what we were able to do on this flight was to replace nine of the tiles around the nose-landing gear door."
Another concern has been foam debris that comes off the external fuel tank during launch. Space Shuttle External Tank Project manager John Chapman says despite modifications, foam will still come off the tank.
"It's the very nature of the material itself and the way that we use it and the way that we apply it. It is an expected event. Our role in the external tank project, and of course across all of NASA, is to understand as much as we can about the foam any it behaves the way it does and then to take steps to minimize the loses of foam."
Dozens of cameras on the ground and on both the shuttle and the fuel tank will record thousands of images that can be studied by mission controllers after launch and during the mission. A new, high-fidelity digital camera has also been added to the shuttle's orbitor boom. Again, Steve Poulos.
"Its pixel resolution, for those who are part-time photographers, is 1920x1080 pixels. The smallest damage of concern that we have is on the order of .080 of an inch concern and that camera is certified to be able to show us that level of damage."
The window of opportunity for launch begins July 1st. You can find out more about the next shuttle mission through a link on our website, KUHF.org.