CARLOS CEDEÑO DSES /04/2008 Reliability of the Three Main Engines of Space Shuttle

Introduction Objective  Determine the reliability of the NASA Space Shuttle’s three main engines. Problem  The flight readiness of the three Main Engines of the space shuttle to launch safely has been argued to be between 80% – 85% during the program early stages.  After the 2003 Columbia accident NASA took on the initiative of improving the Space Shuttle system. The new improvements included to make the three main engines more reliable. In 2008 the Shuttle three Main Engines are 40% more reliable during ascent than the old ones, with an ascent risk of 1 in 2,123 flights (failure rate ~.0004).  The Space Shuttle can still perform with 2 out of the 3 main engines working.

Reliability Functions It was assumed that the three engines have the following cumulative probability distribution:  F = 1-exp(-.0004*t) Using Maple, the reliability functions were calculated for a system that fails when 2 out of the 3 components fail.  MTTFs2oo3 = 2083 flights

Reliability Plots

Monte Carlo Simulation A Monte Carlo Simulation using a 1000 runs was performed to get the Reliability that 2 out of the 3 Main Engines still work under any given time.

Conclusion The new improvements to the Shuttle Main Engines makes the Shuttle very reliable and safe.

Reliability Block Diagram of Space Shuttle three Main Engine Engine μ= Engine μ= Engine μ= Computer μ=.001 Computer μ=.001 Computer μ=.001

Space Shuttle Crash Unresponsiv e Space shuttle Loss of Lift Force Engine Over-heated High Temperature Reading Fault Tree Analysis Shuttle Three Main Engines Without Computer Engine failure Loss of Lift Force Engine Over- heated High Temperature Reading Engine failure Loss of Lift Force Engine Over-heated High Temperature Reading Engine failure

Event Tree Analysis Shuttle Three Main Engines Without computer High Temperature Reading True Uncontrolled Landing, with Possible loss of vehiche Initial EventEngine Over-heatedLoss of LiftOutcome False Normal Operation Of Engine Mission aborted with Controlled Landing