Reserves and Safety Margin

Engines that have long service lives typically are overdesigned initially. An example from 
the RL-10 is that the original engine had a chamber pressure of 300 psi. That pressure has 
doubled in subsequent revisions of the engine. Mr. Tabata strongly advocates designing more 
safety margins into new engines even though it adds to costs. He also spoke of arbitrary or 
inconsistent safety margins that sometimes occur. As an example, he cited new standards for 
proof and burst pressures on the RL-10 (see qualification) of:

1.5 x max pressures for proof on valves
2.5 X max pressures for burst on valves

If the other components are still at 1.2x and 1.5x max pressure, the new standard for the 
valves makes no sense.