scope:

Description of Driving Event:

The SSME design verification specifications are evaluated by analysis, laboratory testing, subsystem testing, and/or engine hot fire testing. Tests are planned to expose problems early and consist of overstress tests, off limits tests, and malfunction tests. The ground test program prior to the STS 51-L accident was questionable. The number of tests per month had decreased during a two year period prior to the accident. The SSME development program specifies a ground hot fire test program that includes multiple engines of the flight configuration, with maintenance and inspections, that demonstrates hot fire operational time far in excess of the orbiter fleet leader engine. It also pursues engine hot fire tests that demonstrate the limits of the engine operational parameters and margins or over-stress tests to verify the full engine capability. Further, margin tests should be conducted to the extent that they reasonably represent potential engine operation in a degraded state.