Re: [FT] Hull strength and Stress

Jared wrote:

> One aspect of the design system that bugs me, though, is the hull 
> strength issue.  Basically, for any given Mass, there are 5 hull
strengths > you can have (10-50% at 10% increments.  For extremely
small ships, 
> some of these levels may actually be the same due to rounding 
> concerns.)  So a mass 100 ship can have 10,20,30,40 or 50 hull
points.  > Why not 35?	Is there some magic in the breakpoints where
they are.

It can, but those 5 extra points are usually called "armour" <g> And
yes, I know it isn't identical. Allowing any ship to have between 10%
(FRU) and 50% (FRD) of its TMF for hull boxes works just as well as the
current system.

> ** Hull Stress Ratings **

[Entire section snipped; I don't agree at all with the premises]

The hull integrity doesn't have very much to do with withstanding
acceleration stresses IMO. Even a Fragile-hulled ship is designed to
survive its own engines without falling apart. (Count the necessary
reinforcements into the Mass used for engines if you like!)

Instead, the hull integrity measures how much of the hull structure you
can *remove* - how many bulkheads can be breached, how many struts torn
off etc - before the ship no longer is able to survive the stresses
caused by its own engines, etc. Indeed, some of the "engine damage"
results may well be structural results instead - the hull takes such a
bad hit that the captain doesn't dare to use his engines for fear that
the ship be torn apart until the DCPs have assessed the damage.

My solid mechanics professor did a rather fascinating demonstration of
this in the first course I read for him. He is a rather big man - 90+
kilos judging from his looks - and he put an empty soft drink can on
its end and stepped on it. Stepped *up onto* it and stood there for
almost a minute, because the can didn't buckle or get crushed. He then
stepped down, made a very minor dent in the (cylindric) side of the
can, put it back down and stepped on it again - and the can was
immediately flattened. The small dent was enough to reduce the can's
"hull integrity" to less than it needed to survive the stresses put on
it.

I imagine spaceships to work in a rather similar way. As long as the
stresses *and the hull structure* are within the design parameters all
is well, but when you remove enough of the hull structure that it drops
outside the parameters... things tend to go pear-shaped.

Regards,

Oerjan Ohlson
oerjan.ohlson@telia.com

"Life is like a sewer.
  What you get out of it, depends on what you put into it."
- Hen3ry