Originally Posted by
tdracer
You can protect for low energy debris - blade fragments and the like. But when you start talking 1/3rd disc from an engine operating at high power, it's simply not feasible. You're talking inches of armor plate to do any good (and you can't assume a perfect tangential trajectory - I think the range was 5 degrees for high energy debris - so you need to protect a rather large area). I used to work with a couple guys that had worked in the old Boeing turbine division (that's right, Boeing used to make small turbine engines back in the 1960s) that showed me pictures of the damage to their test cell due to a rotor burst - went through armor plate and a brick wall - and that was just a little APU sized turbine.
Probably yet more thread drift, for which apologies. But I recall that an industrial turbine (which really are not that different from their aircraft-mounted cousins, and in this case was a derivative for the 'other role') has a disk 'go' when in use on an oil rig. The disk fragment went through the entire oil rig, doing the "hot knife through butter" thing as it went, and disappeared off the side. How much equivalent armour plating it went through, who knows. But it hardly slowed down.