12.6 The tubular casing of a solid rocket booster (SRB) for the space shuttle has a mean radius of 71.76" and a wall thickness of 0.479". The maximum working pressure it has to contain is 6.303 MN m. What is the hoop stress at this pressure? The casing is made from D6AC steel with a yield strength of 1244 MN m². What is the safety factor S for the casing? Answers 944 MN m² 1.32