Stealth for Dummies

Continuing the highly acclaimed (according to ComNavOps' brother-in-law) “Dummies” series, we turn our attention to stealth in warship design.  Just as there was (there isn’t now since they’ve all read the Armor for Dummies post and have been educated !) a group of people who, misguidedly, believed that armor was pointless because it couldn’t totally stop every weapon in existence, so too, there is a group of people (probably the same group) who believes that stealth is pointless since it can’t make a warship completely invisible.  Such a belief could not be more wrong and we’ll now see why.

Most people believe that the purpose of stealth is to conceal the location of a ship – if you can’t find it you can’t attack it.  That’s great except that the naysayers will point out, correctly, that it’s not possible to completely hide a ship with stealth measures.  You can reduce the radar (or visible, or infrared, or electromagnetic) signature to some degree but any ship can be detected.  Let’s face it, we can’t completely mask aircraft and ships are many times larger.  Further, some aspects of ship design just don’t lend themselves to enhanced stealth.  The hull just plain has to be a big vertical chunk of metal.  We can slope the sides somewhat but the hull is still a big radar return.  The same goes for the superstructure.  The various sensors and weapons offer large radar returns and their signatures can’t really be reduced all that much without adversely impacting their function.  Ships need cranes, boats, and deck gear all of which increases the ship’s signature.  So, there’s no getting around the fact that a ship can’t be made invisible.

So, why do we even bother with stealth?  Well, we can reduce the ship’s signature and every bit of reduction makes the ship just that much harder to find.  For a ship attempting to penetrate an enemy A2/AD zone, every hour it can avoid detection is an hour less time the enemy has to attack it or reposition assets to deal with it.  Every hour undetected is an hour of safety making it more likely that the ship will be able to carry out its mission. 

Further, in order to overcome stealth, the enemy will be forced to employ more subs, patrol boats, AEW, and search assets in attempt to increase the density of their search coverage.  This soaks up assets that might otherwise be employed offensively.  So, stealth requires the enemy to assume a larger, more defensive posture than they would prefer.



Enough of a Good Thing or Too Much?



Sooner or later, though, the ship will be found.  What then?  Well, this is where stealth serves its second purpose - a purpose most people overlook.  When a ship is found, what is required to attack it?  The location is, by definition, now known but modern weapons require more than that.  They require a target lock for terminal guidance of the weapon.  That lock may take the form of radar returns, infrared, or whatever.  If the weapon can’t achieve a lock, it won’t strike its target.  It’s that simple.  We could park a ship ten miles off an enemy’s coast, broadcast its location, and, if the stealth measures were good enough, the ship would be invulnerable because the enemy weapons couldn’t lock on.

Is warship stealth that good?  Not hardly! 

So, again, what’s the point of stealth if we can’t totally prevent target lock?  Consider a group of missiles launched towards our ship whose location is reasonably accurately known.  The missiles will be spread out and some will approach the ship on the fringe of the missile’s detection radius.  Stealth reduces that detection radius so that some of the missiles that might otherwise have locked on will miss, never having seen a target.  Of course, some of the missiles will approach dead on and will achieve target lock.  Bad day to be on our ship, huh?  Not necessarily.  Even those missiles that achieve a target lock will have the strength of that lock reduced due to the ship’s stealth.  That allows the ship’s passive defenses such as chaff, flares, and ECM to be more effective.  In other words, a missile with a weak lock is more susceptible to being decoyed than one with a strong lock.  Of course, some missiles will still maintain a sufficient lock for a terminal attack and that’s why ships carry point defense weapons.  Nothing, including stealth, is perfect!

We see, then, that stealth serves not one, but two purposes:  making detection more difficult and degrading weapon locks.  It’s the second purpose, degrading weapon locks, that strikes me as the more important.  In combat, ships will be found.  It’s what happens after that that really matters.  Will the ship survive the inevitable combat to carry out its mission and, hopefully, return home?  Stealth increases the chances of survival.  The notion that stealth must completely hide a ship in order to be worthwhile is just as silly as the idea that armor must completely stop all weapons. 

Like armor, which carries a weight penalty, stealth carries a cost penalty.  Stealth designs are more complex, a bit harder to build, require some additional equipment, and, most significantly, reduce available deck space (look at any stealth warship and compare it to a WWII conventional ship and you’ll see what I mean – the LCS is an extreme example of a stealthy ship that has very little horizontal deck space for mounting weapons, sensors, and gear).  Still, the penalties are well worth it and can be compensated for.  Of course, there’s a balance point in the stealth cost-benefit relationship.  Where that point is, I don’t know.  Has the Zumwalt gone too far?  Only time will tell.

Clearly, stealth enhances the survivability of warships and does so at relatively little cost.  Hey, throw in some armor and you’re on your way to a good ship design!