How can a supersonic cruise missile be intercepted?

Question

• India fires missile into Pakistan after ‘technical malfunction’

The above news says that India accidentally fired a supersonic missile, most probably a BrahMos cruise missile, into Pakistan. The most probable reason would be a technical malfunction. Luckily, the missile was not carrying any warhead i.e was unarmed, and the Indian Foreign Office (FO) also apologized for the error.

However, Pakistan's social media is very upset regarding the Pakistan military's incapability to intercept this missile.

Pakistan has LY-80 and FD2000 SAM systems from China.

Are these systems capable of intercepting BrahMos like supersonic cruise missiles?

If YES, what was the possible reason for not intercepting the missile?

If NOT, which systems can?

Answer 1

Yes, intercepting incoming supersonic cruise missiles is possible. There are several ways:

1. Anti-Missile Missile: If the missile is detected early enough, you can launch an anti-missile missiles. Examples for such missile systems are the patriot system, or the one you asked about LY-80/HQ-16. A lot of these systems are designed as anti-ballistic missiles (ABM), but because of the similar task and generally lower intercept requirements (less speed, lower altitude compared to a ballistic missile), ABM systems are generally capable of intercepting a supersonic missile as well. For example the LY-80/HQ-16 can intercept targets as low as 15m above ground level. They can also be used against similar flying targets such as helicopters, aircrafts and even drones (although that might be costly). The Brahmos flies up to Mach 4 but in cruise flight most likely slower, the LY-80/HQ-16 has a similar top speed. This makes intercept more difficult e.g. you have less time to launch the intercept missile or the anti-missile system must be located in a more favourable spot.
2. Close-in weapons systems: If you spot the missile very late or if the missile penetrated your outer defense for example because it uses terrain masking or sea skimming tactics, you can also use Close-in weapons systems (CIWS), which are simply very rapid firing machine guns which try to hit the incoming missile at close distances (<1km). These weapons are however primarily used to defend one point in space, for example a ship or a military base.
3. Energy Weapons: Until now in very experimental stages are energy weapons. Because of atmospheric disturbances and other technical challenges, these are however not (yet?) used for defense against missiles. However some systems or this one against "low-end threat" are now coming into existence.

Coming back to your question: What the exact reason is, will very likely remain a secret of the pakistani army simply because this information could be exploited by an agressor, therefore the things that might have gone wrong are endless. Some of the top of my head.

• The missile was not detected: Reasons might be because it successfully used sea skimming or terrain masking tactics, or because it is stelthier then anticipated, or because the intercept radar malfunctioned or because the radar operator was asleep.
• Unfavourable defending position: If your defending missile is far away from the incoming missile, it has to fly for longer. Also if the incoming missile is very fast you have a shorter time to react and also you have to fly faster to consumate the intercept. Perhaps the combination of these factors was just not in favor for the Pakistanis. However normally the defender very closely analyzes where to station his forces in order to avoid exactly such a situation.
• Technical problems with consuming intercept: Anti-missiles do not always hit, there is a intercept probability, this is why often several anti-missiles are started to counter one incoming threat. Perhaps the Pakistanis were just unlucky.
• The intercept was deemed unnecessary: Missiles are not cheap. If it was deemed that an intercept was unnecessary, because the projected target area is uninhabitated/unimportant, then perhaps someone decided that it is just not worth the cost.
• Human factor problems: This could include miscommunications, conflicting area of responsibility and so forth and so on.

Answer 2

Cruise missiles are possible, but difficult to intercept.

The interception rate against cruise missiles is unknown, but generally lower than against aircraft. Take all figures as relative comparisons and all numbers as just orders of magnitude. In general, a kill probability of 50-90% is considered effective.

This paper includes some math. This is for a point target being specifically defended, against an expected attack. There are multiple factors that can break the kill chain, and you can see how 50% can quickly turn into 5% if the missile is considerably more advanced.

Speed complicates interception in several ways. It gives less time to detect, identify, prepare to fire, and engage the target. It also multiplies the effect of error in tracking and targeting. Overall, the difficulty of interception scales approximately with speed squared. The paper above is for guns, but the math for missiles works in similar ways.

As can be seen from these sources, key factors that affect missile interception difficulty include:

• Speed
• Maneuverability
• Countermeasures
• Jamming

The Brahmos missile represents the mid-upper tier of ~2010 Russian missile technology, augmented with Indian-developed software on Western hardware. It's been designed to defeat medium and large warships of modern navies, including the USN. Such ships are protected with at least 3 tiers of missile defense: SM-2 at a long range, ESSM within 30 nmi, and Phalanx CIWS at close range.

Given such targets, the Brahmos missile includes the widest range of electronic countermeasures among modern missiles, the highest speed, and is capable of various maneuvering profiles. In comparison, the Chinese systems employed in Pakistan are closely based on 1980s Soviet SAM systems.

The HQ-16 is inadequate against missiles such as Brahmos, lacking in both range and speed. The missile is outside its engagement envelope.
The FD2000 is more sophisticated, being based on a still highly sought-after system. But it's likely to only include the basic anti-aircraft tier the S-300, not the newer anti-missile tier that the market is after.

It would've been unexpected if a 2010 missile designed against warships got intercepted by a 1980s SAM on low alert. That said, every interception has a chance of success - stealth bombers have been hit and downed by outdated SAM. The difference is, the Serbs were expecting attacks in their successful F/A-117 hits, the Pakistani weren't.

As for what systems are needed to intercept such a missile, it all depends on the required kill probability. Nothing would give 100%. But to rely on a steady kill rate above 50%, one would have to employ a modern system with specialized anti-missile capability such as SM-3, MEADS, or S-400.

To bring the kill rate up further, to where 90% can be talked about, one would have to step up to Integrated Air Defense Systems - a combination of long-range radars, combat air patrols, EAW/AWACS, fighters ready to scramble, and, then, layered long-range, medium-range and short-range SAM systems. 4 to 6 separate interception events, each with an independent chance to kill the target.

The technology would also have to be state of the art, such as S-500, modern jets like the F-35, Typhoon or Su-30, with new missiles like Meteor or latest versions of R-77 or AMRAAM, plus modern local air defense systems. The fighters can be older, though, as long as they get upgraded radars.

The US can afford to protect its major cities with such measures, and would, if it perceived a risk of a cruise missile strike. Russia only protects Moscow and near-frontline cities to this extent. USN carrier strike groups are shielded against missile attack to this level.

It's also critical that these systems have their electronics upgraded to the latest versions on a regular basis, to have the upper hand in electronic warfare. So a missile shield across a lot of territory is among the most expensive defenses to maintain.

The biggest factor not mentioned above is foreknowledge. If you know you're going after a missile flying from point A to point B at time HH:MM, very high Pk above 90% can be achieved. If you're not actively looking for cruise missiles, even the best systems can be ineffective. And if it's unexpected to the point of disbelief, one can land a Cessna on the Red Square.