Imperial Star Destroyers'
deflector shields are inadequate in the face of the Rebels' ion cannon,
and
cannot prevent a small ship from physically latching onto them with a
hook; that same small ship presents a real threat to the bridge tower.
In
general, ramming seems an effective tactic.
Deflector shields are highly
effective against turbolaser fire and broadly available, although they
have clear limits.
Large
theater shields are available that can shield against not only incoming
fire, but prevent ships from transiting through, although they have
limits.
We see very
clearly in TESB several tests of an Imperial Star Destroyer's hull
strength.
First, the Falcon makes an attack run at the bridge tower. As noted on
the
STL Travel
Page
, the
Falcon had an incoming velocity of up to 360 m/s while passing by the
bridge tower.
We may reasonably estimate that the Falcon has a mass of 400-4000 tons,
and (at least initially) impacts on a cross-sectional area of 2-6.3 m
2.
Empirical armor penetration formulae show penetration depth is related
to a term that ranges from V
2M/A to VM
1/2/A
1/4,
where V is the velocity, M is the mass, and A the area of impact. As
the armoring plates' thickness would seem to be substantially lower
than the caliber of the large impacting projectiles, the first formula
is strongly suggested.
This suggests comparison of the Falcon with modern day bullets. While
we're at it, we also see two key asteroid impacts; one takes out a
bridge tower, while another harmlessly glances off the hull or shields
of an ISD. Using typical densities and the speeds commonly suggested,
we have the following table: