Is "space junk" a potential problem for the shuttle in orbit?
The Flight Dynamics Officers (FDOs) in the MCC work with the US Space Command to ensure that the Space Shuttle does not have a close proximity pass with any trackable object in space. Since there are many objects in Earth orbit (including operational satellites, spent rocket bodies, and actual pieces of debris), this is a large task. Debris in space is a problem that has received a great deal of attention over the past few years and has resulted in design and operational philosophy changes to the Space Station program.
How often have shuttles been hit by debris and what was the most significant damage?
Debris hits occur on almost every flight. Usually these are very small microscopic particles that pose little or no danger to the spacecraft. The most significant damage to date has been impacts to the windows. After some flights, several windows have been replaced. There have also been impacts to the orbiter's radiator surfaces, although no coolant has been lost. On STS-79, for instance, there was a 1/8 inch diameter crater in one of the radiator panels. Even small particles pose a risk to the shuttle systems. To minimize this risk, the orbiter is placed in attitudes that protect critical systems whenever possible.