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The
measure of shields, hull armor, and the structural durability of
starships, armored vehicles, etc., is difficult in most cases. A shield
(or armor plate) resists different types of weapons differently,
depending on what kind of armor, shield, and the type of weapon.
It may be highly vulnerable to a particular kind of attack - and
sometimes, there are holes or weak spots in shields or armor, making it
particularly difficult to quantify how much of a beating shields can
take.
Will a small fast projectile with the same energy hurt more than a
large slow projectile? Would you be better off trying to melt the hull,
or smash it?
We have many methods of examining shield and hull toughness:
- Examining the temperature the hull may be heated to.
- When a ship flies near or in a star, estimating the
radiation it is subject to.
- Estimating the relationship between weapon energies and
damage to the shielding of a ship, or the hull of an unshielded ship.
- Examining the relationship between weapon power over time.
- Analysis of impacts of physical objects on starship hulls.
Endurance against weapons is our most frequent form of measurement.
Methodology is relatively simple; the power or energy seen overwhelming
shields or penetrating the hull, or vaporizing/destroying some volume
of starship, or that a ship can survive, is calculated as an upper
limit, approximate estimate, or lower limit.
All the problems about the consistency of weapon power are multiplied
by the uncertainty in the angle of impact, number of attacks employed,
and open questions about what type of attack the shields or armor are
best suited to block.
The last item on the list, though, happens to be a matter of
considerable study. The study of ballistic impacts on armor has been a
matter of pressing concern since the invention of tanks and warships
with enough armor to resist modern guns.
Although the penetration of shaped charges on armor is fairly complex,
simple ballistic impacts by well-designed shells has been exhaustively
formulated. The depth of armor that a projectile can penetrate depends
on its mass, radius, and speed.
All things being equal, a narrower and denser projectile penetrates
better. In most cases, penetration is directly proportional to kinetic
energy, but in others, penetration may be proportional to the square
root.
The original penetration formulae generalize over all shells of a
certain shape by measuring penetration in calibers. On these pages, we
somewhat abuse the empirical armor penetration formulae, pretending
that ships, asteroids, logs, etc., are as well shaped for hull
penetration - and as solidly constructed - as bullets. This may tend to
produce overestimates.
However, the formulae available give us very good estimations for the
equivalent thickness of steel armor needed to match the resistance to
physical impact displayed in Star Wars and Star Trek.
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An article on empirical armor
penetration formulae by noted expert Nathan Okun.
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