MTTF (mean time to failure) is used to evaluate non-repairable items. While MTTF is not computed by a prediction, it is important to understand the difference between MTTF and MTBF. For a non-repairable item, no repair is performed. Once a failure occurs in a non-repairable system, the system has failed. A typical example of a non-repairable system is a telecommunications satellite that is in orbit around the Earth. If this satellite fails, no one is sent to repair it. Instead, a new satellite is launched to replace the failed one. MTTF represents the average time until a failure of a non-repairable item occurs.