Countermeasures for hypersonic weapons

[nsaspook]

What's the target profile of a hypersonic weapon? It's high-value, very well defended target like an nuclear aircraft carrier far at sea surrounded by multi-layered defenses so weapons like an advanced CIWS with nearly free fire capability on any tracked target are possible without worrying about duds and Collateral damage. It's basically a dooms-day first-strike weapon (even conventionally armed hypersonic weapons would still be seen as a strategic if they could sink carriers) because if we can track where the weapon came from you can bet your last dollar something heavy will be headed in that direction if 5000+ people were dead from a destroyed ship.

The actual usage of a hypersonic weapons on high-value targets is IMO suicidal.

 

[Vanadium 50]

Some thoughts on CIWS, because it doesn't work the way people seem to think it does. Most of my experience is with the Phalanx.

It has a range of 6000 yards. It does not decide there is a target, carefully aim, and fire a single bullet at it, like a sniper. Ever try and hit a stationary target with a rifle at even 1000 yards? I can tell you, it's real damn hard. Now imagine something six times farther out, moving, and from a platform that is not only moving, but also pitching.

No, the way the Phalanx works is it sprays as much lead as it can in the general direction of the target. Most of the time, the lead density isn't high enough to make a hit on the target until it is substantially closer. Like maybe 1000 yards. Sometimes less. Indeed, it normally does not fire at its maximum range, preferring that the target get closer. It takes luck to take out the target at 4000 yards, but not as much as at 6000 yards.

Once the Phalanx starts firing, missile speed is of no advantage. Think of it as walking through a (land) minefield. If you ran instead, the risk is exactly the same. ("But...I'm only spending half as much time in it!")

Targets are usually tracked for many tens of seconds before the Phalanx fires. It is true that a faster missile reduces this time. However, there are other ways to reduce this - fly low and slow and stay out of the target's radar horizon for as long as you can, and stay close to the surface clutter. If you do it with speed, you build in a disadvantage: just as the target has less time to respond to the missile, the missile has less time to respond to the target: it was fired where its operators thought the target would be by the time the missile got there. It might be there. It might be somewhere else.

 

[nsaspook]

Flak as a countermeasure as been around since the beginning of aviation.


Modern Flak example:

 

[boneh3ad]

What's the target profile of a hypersonic weapon? It's high-value, very well defended target like an nuclear aircraft carrier far at sea surrounded by multi-layered defenses so weapons like an advanced CIWS with nearly free fire capability on any tracked target are possible without worrying about duds and Collateral damage. It's basically a dooms-day first-strike weapon (even conventionally armed hypersonic weapons would still be seen as a strategic if they could sink carriers) because if we can track where the weapon came from you can bet your last dollar something heavy will be headed in that direction if 5000+ people were dead from a destroyed ship.

The actual usage of a hypersonic weapons on high-value targets is IMO suicidal.

This is all conjecture, of course, and defends on the nature of the weapon. The US Department of Defense, for example, has expressed a desire for tactical type hypersonics weapons (as opposed to strategic) and in numbers where they aren't super special to actually use. The idea would be to be able to hit SAM sites prior to a larger scale air assault or heavily defended targets like mobile ballistic missile launchers before they can launch.

These are not necessarily doomsday first strike weapons (at least as the US envisions them). They're more like Tomahawk missiles, only considerably faster. Of course there will be strategic systems as well, but not exclusively.

 

[boneh3ad]

To address the OP's original question a bit more, have a look at the field of aero-optics. It has to do with the optical path distortion (OPD) created by aerodynamic flow features (e.g., shocks and expansion fans, turbulent boundary layers and wakes, wakes and shear layers, separation bubbles). At high speed these all involve density fluctuations and sometimes chemistry that will set up gradients in the index of refraction. This obviously has important implications on the ability to hit something with directed energy, but also the ability to see out from or communicate with said vehicle.

Most work in this field is in the transonic regime intended to characterize OPD around, for example, radomes. In hypersonics flows it's all relatively new and/or hidden behind a black curtain.

 

[nsaspook]

This is all conjecture, of course, and defends on the nature of the weapon. The US Department of Defense, for example, has expressed a desire for tactical type hypersonics weapons (as opposed to strategic) and in numbers where they aren't super special to actually use. The idea would be to be able to hit SAM sites prior to a larger scale air assault or heavily defended targets like mobile ballistic missile launchers before they can launch.

These are not necessarily doomsday first strike weapons (at least as the US envisions them). They're more like Tomahawk missiles, only considerably faster. Of course there will be strategic systems as well, but not exclusively.

Sure, it's all conjecture, just like WW3 hopefully always will be.

I'm looking at it from the standpoint of US defenses from Russian and Chinese hypersonic weapons. The US can't really find a rational reason to deploy conventional tactical versions of these weapons and our military advisories know that nukes will be necessary for the desired effects on hardened targets because of limited warhead size.

 

[FactChecker]

A hypersonic, low-altitude, maneuvering missile would be extremely hard to stop. That is what the current use of the term "hypersonic missile" is referring to. It is no more a waste of money than any other weapon system we have. It represents a future weapon system upon which a war may be won or lost. It is the kind of thing that can slaughter an unprepared opponent.

 

[boneh3ad]

Sure, it's all conjecture, just like WW3 hopefully always will be.

I'm looking at it from the standpoint of US defenses from Russian and Chinese hypersonic weapons. The US can't really find a rational reason to deploy conventional tactical versions of these weapons and our military advisories know that nukes will be necessary for the desired effects on hardened targets because of limited warhead size.

What are you talking about? The US is only developing conventional versions of these (at least for now). By only having conventional versions, it makes it more feasible to actually use without someone assuming it's nuclear. The whole idea is to have thousands of conventionally armed, tactical hypersonic stand-off weapons. That's assuming you believe what the DoD says publicly, of course.

 

[nsaspook]

What are you talking about? The US is only developing conventional versions of these (at least for now). By only having conventional versions, it makes it more feasible to actually use without someone assuming it's nuclear. The whole idea is to have thousands of conventionally armed, tactical hypersonic stand-off weapons. That's assuming you believe what the DoD says publicly, of course.

Let's just say I'm seeing little indication potential users are sold on the tactical hypersonic side past the R&D stage. IMO the driving rational for these weapons are nuclear.

https://media.defense.gov/2019/Sep/25/2002187108/-1/-1/0/59HYPERSONICWEAPONS.PDF

The Russian creation, deployment of this weapon system is a direct consequence of the 2002 ABM treat withdrawal. It's a counter-force weapon to regain, from their point of view, strategic nuclear balance with the USA.

https://www.airforcemag.com/article/1005counterforce/

 

[FactChecker]

Let's just say I'm seeing little indication potential users are sold on the tactical hypersonic side past the R&D stage. IMO the driving rational for these weapons are nuclear.

Taking out radar systems, fuel depots, communications systems, naval facilities, runways, etc., etc., etc. We used a lot of cruise missiles in the initial phase of the latest wars. They may not get to the target in the future if they are not hypersonic.

 

[nsaspook]

Taking out radar systems, fuel depots, communications systems, naval facilities, runways, etc., etc., etc. We used a lot of cruise missiles in the initial phase of the latest wars. They may not get to the target in the future if they are not hyper-sonic.

Most of those cruise missile flew Nap-of-the-earth, highly maneuverable paths, below land-based radar and defensive targeting systems to lightly defended targets. It's unlikely that will change even if we have effective hypersonic attack systems and defenses for high-value targets. Sub-sonic cruise missiles can be very dim to sensors using modern technology.

Anti-ship weapons is a sweet spot for hypersonics and as usual the best defense is “attacking the archers before they launch their arrows.” like we did with Japanese kamikazes in World War II.

https://www.history.navy.mil/browse...5/battle-of-okinawa/antiaircraft-problem.html

Another tactic, the “big blue blanket,” emphasized offensive action against Japanese airpower. In the lead-up to Operation Detachment, the invasion of Iwo Jima, Task Force 58 raided airfields in the Japanese home islands. Between 16–17 February 1945, 11 fleet and five light aircraft carriers flew 2,761 sorties which claimed the destruction of 500 enemy aircraft on the ground and in the air.[21] The Japanese managed only one kamikaze raid on forces supporting the subsequent Iwo Jima landings. On 21 February 1945, they struck six ships, sinking the escort carrier Bismarck Sea (CVE-95), killing 318 Sailors; and damaging fleet carrier Saratoga (CV-3), leaving 123 dead; and inflicting minor damage on Lunga Point (CVE-94) and three smaller vessels.[22]

TF 58 again raided Japanese airfields on Kyushu on 18–19 March 1945, in preparation for Operation Iceberg, destroying an estimated 528 enemy aircraft in the air and on the ground. It was joined by TF 57, a British carrier force, which attacked Japanese airbases in Formosa in late March and early April, and later joined TF 58 off Okinawa

 

[jim mcnamara]

Loud rifle reports are from hypersonic projectiles - sometimes called bullets. There are hunting rifles with muzzle velocities out of the box, using standard cartridges that exceed Mach 2.
First produced in 1938, the Swift 220:
https://en.wikipedia.org/wiki/.220_Swift

@Dr. Courtney likely knows more about hypersonic cartidge hand weapons.

The primary premise of this discussion is not well founded or fit for PF discussion - see @boneh3ad post above. Please stop making up stuff or the thread will be closed. We want specific scientific research, not hypothetical suppositions. Fair warning. This is directed at the OP, but applies to all of us.

 

[FactChecker]

Loud rifle reports are from hypersonic projectiles - sometimes called bullets. There are hunting rifles with muzzle velocities out of the box, using standard cartridges that exceed Mach 2.

Hypersonic is Mach 5 and higher. The Concord could fly at Mach 2.

 

[jim mcnamara]

Thanks for the correction. I learned the term incorrectly obviously.
https://www.dictionary.com/browse/hypersonic

 

[Vanadium 50]

Hypersonic is Mach 5 and higher.

Not according to the OP.

hypersonic weapons? These are missiles that travel in excess of 1.5 km/s.

Again, this is part of why it's important we know what the OP is talking about so we're all on the same page.

 

[FactChecker]

Not according to the OP.

He is within the ballpark. Mach changes with altitude, so there is no simple conversion.

 

[Vanadium 50]

It seems confusing to say that Mach 2 is "hypersonic" and yet Mach 4 is not.

 

[hutchphd]

The problem exists. It's kind of silly pretending it doesn't. If you want a hypothetical weapon, maybe the Chinese DF-17. Or the Russian Tsirkon. Or myriad others in development. The precise system hardly matters for this discussion because, at the moment, no one can effectively defend against any of them.

To be worried about defending against these hypersonic weapons, one would need to assume a viable ABM system exists or is even near-term feasible.
If you believe that I have a bridge for you. I fear Northrop-Grumman is making a similar pitch.

The debate should be where to spend our money. Let's give ten percent of it to Elon. More bang fewer bucks.

 

[FactChecker]

It seems confusing to say that Mach 2 is "hypersonic" and yet Mach 4 is not.

I don't see the statement that Mach 2 is hypersonic in the OP. The speed of 1.5 km/s is given. That is about Mach 4.4 at sea level (about Mach 5 at 30,000 ft., standard atmosphere)

 

[boneh3ad]

I don't see the statement that Mach 2 is hypersonic in the OP. The speed of 1.5 km/s is given. That is about Mach 4.4 at sea level (about Mach 5 at 30,000 ft., standard atmosphere)

It's also important to note that the line between supersonic and hypersonic is not a hard cutoff like to he difference between subsonic and supersonic. The characteristic features of hypersonics flow emerge slowly over a range of Mach numbers. Depending on which aspects are germane to a given discussion, you could reasonably say hypersonic starts anywhere from Mach 4ish to 10ish.

 

[shjacks45]

Two reasons really:
1. Unless you are able to put interceptors everywhere, you want your interceptors to be fast so that a few launch sites can cover a wider area.
2. Incoming hypersonic missiles would themselves be highly agile, which means your interceptors must be able to do large course corrections at short notice.

@boneh3ad: Not looking for specifics but broad "coffee break physics" discussions. I note there are many articles in the public domain that discuss hypersonic weapons as a disruptive technology.

The speed of hypersonic attack vehicles would warrant a point defense not umbrella defense.
For a given turn rate, higher speed gives a wider turn. Larger turning radius equals less agile. Faster turns could lead to spin which is destructive at hypersonic speeds. ICBMs are hypersonic on reentry from space. The threatened low altitude hypersonic anti ship missile (Russian and Chinese tests) is short range and like most missiles, it won’t sink a ship. (Ships only sink if damaged below the waterline. )

The problem exists. It's kind of silly pretending it doesn't. If you want a hypothetical weapon, maybe the Chinese DF-17. Or the Russian Tsirkon. Or myriad others in development. The precise system hardly matters for this discussion because, at the moment, no one can effectively defend against any of them.

Also, citing examples about F-5s evading SAMs over Vietnam is hardly relevant. It was 50+ years ago and missiles have advances substantially since then.

Right now all US missile defenses publicly released are designed for either the terminal phase of a fast but non-manuevering weapon or the midcourse phase when it's still pretty vulnerable in space. All of our tracking systems are designed for that, too. A weapon that flies under our midcourse defenses and can maneuver in the terminal phase is currently undefendable and we are effectively relying on deterrence.

See: https://fas.org/sgp/crs/weapons/R45811.pdf

You quote the same arguments as 1950s supersonic bomber ‘low and fast and maneuverable’ belief.

 

[shjacks45]

Loud rifle reports are from hypersonic projectiles - sometimes called bullets. There are hunting rifles with muzzle velocities out of the box, using standard cartridges that exceed Mach 2.
First produced in 1938, the Swift 220:
https://en.wikipedia.org/wiki/.220_Swift

@Dr. Courtney likely knows more about hypersonic cartidge hand weapons.

The primary premise of this discussion is not well founded or fit for PF discussion - see @boneh3ad post above. Please stop making up stuff or the thread will be closed. We want specific scientific research, not hypothetical suppositions. Fair warning. This is directed at the OP, but applies to all of us.

The question invited hypothetical solutions. There are a lot of “what if” (“suppose ...”) questions in the forums. But much of Physics is hypotheses based, so I don’t think a blanket prohibition on hypothetical questions is possible.

 

[shjacks45]

This is all conjecture, of course, and defends on the nature of the weapon. The US Department of Defense, for example, has expressed a desire for tactical type hypersonics weapons (as opposed to strategic) and in numbers where they aren't super special to actually use. The idea would be to be able to hit SAM sites prior to a larger scale air assault or heavily defended targets like mobile ballistic missile launchers before they can launch.

These are not necessarily doomsday first strike weapons (at least as the US envisions them). They're more like Tomahawk missiles, only considerably faster. Of course there will be strategic systems as well, but not exclusively.

Tomahawk missiles can be used against ships.

 

[shjacks45]

The problem exists. It's kind of silly pretending it doesn't. If you want a hypothetical weapon, maybe the Chinese DF-17. Or the Russian Tsirkon. Or myriad others in development. The precise system hardly matters for this discussion because, at the moment, no one can effectively defend against any of them.

Also, citing examples about F-5s evading SAMs over Vietnam is hardly relevant. It was 50+ years ago and missiles have advances substantially since then.

Right now all US missile defenses publicly released are designed for either the terminal phase of a fast but non-manuevering weapon or the midcourse phase when it's still pretty vulnerable in space. All of our tracking systems are designed for that, too. A weapon that flies under our midcourse defenses and can maneuver in the terminal phase is currently undefendable and we are effectively relying on deterrence.

See: https://fas.org/sgp/crs/weapons/R45811.pdf

There was a vid of a Air to Air missile test where the (Mach ~3.5) missile disintegrated after a hard course change. Hypersonic maneuverability doesn’t seem promising until some new unknown properties of aerodynamics are discovered.

 

[Doug H]

Why? The interceptor doesn't chase the target from behind, it intercepts the target from ahead of its path. A football player who intercepts a pass does not have to run faster than the football flies.

Exactly, an interceptor need only release a cloud of dense objects in the hypersonic missile's path, only one of which would destroy the missile. Thus the very speed of the missile would be a weakness leading to it's demise.

 

[Doug H]

It is. If you listen to any stories from Vietnam War fighter pilots, many had to dodge dozens of SAMs, and it was possible precisely because being fast made them less manoeverable; a 400kt fighter jet can out-maneuver a machine 3 missile.

It has everything to do with the wing-loading [pounds of lift per square foot of wing area]. Jets have relatively much larger wings for their size than missiles, so they can maneuver out of it\s way and the missile can't follow the arc of the aircraft's turn.

Well think about it. When you design a missle for hypersonic flight, the larger the control surfaces the higher the drag (and the lower the speed). Hypersonic missles would typically have very small/sleek control fins at the rear...

View attachment 275031

Plus what V50 said ^^^^^^

 

[boneh3ad]

The speed of hypersonic attack vehicles would warrant a point defense not umbrella defense.
For a given turn rate, higher speed gives a wider turn. Larger turning radius equals less agile. Faster turns could lead to spin which is destructive at hypersonic speeds. ICBMs are hypersonic on reentry from space. The threatened low altitude hypersonic anti ship missile (Russian and Chinese tests) is short range and like most missiles, it won’t sink a ship. (Ships only sink if damaged below the waterline. )

You quote the same arguments as 1950s supersonic bomber ‘low and fast and maneuverable’ belief.

The speed of such an attack is exactly why a point defense would be a last ditch effort if there are other options available. Kinetic energy alone is considerable at the relevant speeds, so even if you disabled the missile, the simply impact of it can do substantial damage.

The 1950s arguments aren't exactly relevant here. Many bombers went the way of the dodo due to the advent of intercontinental ballistic missiles. They were a game changer. Sure, some tech may sneak up on us, but at the moment, it isn't clear what that would be.

Tomahawk missiles can be used against ships.

What's your point? My point was that the way the DoD envisions these systems is as a heavily used asset in a mostly tactical role. Essentially, they want a very fast Tomahawk; something that can be deployed at scale from multiple platforms and with multiple mission profiles.

There was a vid of a Air to Air missile test where the (Mach ~3.5) missile disintegrated after a hard course change. Hypersonic maneuverability doesn’t seem promising until some new unknown properties of aerodynamics are discovered.

The idea of "unknown properties of aerodynamics" is kind of absurd. We know the important aerodynamic details. There are still some of the smaller bits that warrant further study, of course, but we have been flying things at hypersonic speeds (including with a human pilot) without them disintegrating for nearly three quarters of a century now. The issue is not discovering unknown aerodynamics. Materials and propulsion have been the long poles in the tent for a while.

Exactly, an interceptor need only release a cloud of dense objects in the hypersonic missile's path, only one of which would destroy the missile. Thus the very speed of the missile would be a weakness leading to it's demise.

In principle, this would make some sense. The problem is the part about releasing the objects into the missile's path. How do you predict the path? This isn't a ballistic trajectory; it's a maneuvering, comparatively low altitude trajectory. In other words, not only can it zig and zag out of the way, but it also spends a great deal of time in a zone where no one currently has a great deal of radar coverage. By the time you acquire it, track it, and launch, you've got maybe one shot at a kill, and with current systems, that's a real shot in the dark.

It has everything to do with the wing-loading [pounds of lift per square foot of wing area]. Jets have relatively much larger wings for their size than missiles, so they can maneuver out of it\s way and the missile can't follow the arc of the aircraft's turn.

The SA-2/S-75 entered into service in 1957. Technology has advanced considerably since then in terms of aerodynamics, materials, and guidance, navigation and control (GNC). At this point, missiles are far more maneuverable than they one were. While the limit of maneuverability for a missile is based largely on the materials and GNC limits, the maneuverability of a manned aircraft is fundamentally limited by the human body.

Of course that isn't really germane to the discussion of defending against hypersonic missiles. They don't need to be able to maneuver in a way that they can chase a plane. They just need to be able to avoid being predictable, avoid countermeasures, and then hit a stationary target (or nearly stationary compared to a plane). It's a considerably easier problem.

 

[boneh3ad]

Let's just say I'm seeing little indication potential users are sold on the tactical hypersonic side past the R&D stage. IMO the driving rational for these weapons are nuclear.

https://media.defense.gov/2019/Sep/25/2002187108/-1/-1/0/59HYPERSONICWEAPONS.PDF

The Russian creation, deployment of this weapon system is a direct consequence of the 2002 ABM treat withdrawal. It's a counter-force weapon to regain, from their point of view, strategic nuclear balance with the USA.

https://www.airforcemag.com/article/1005counterforce/

And let's just say that my experience with potential users are that they are very much excited about these systems. The first paper you link does discuss a frequently-cited issue with the current arms race in this realm: namely that there seemingly hasn't been much publicly-released information on what considerations (if any) DoD has given to the geopolitical implications of these weapons and how our own strategy fits into that. That's a conversation that desperately needs to be had (if it isn't already), but the actual users are chomping at the bit to add this into the arsenal, even if the implications could stand to have a lot more debate.

Having said that, it's clear that the US is taking a different strategy than the Chinese and Russians, at least at this point. Some of the first weapons likely to be fielded are the hypervelocity projectile and ARRW, the first of which is basically a fancy (and really cool) artillery shell and the second of which is seemingly an extremely fast stand-off missile (as opposed to a large, silo-launched strategic weapon). At least at this point, there are no public indications that any nuclear variant is in development.

Of course that raises another issue, namely how do you convince the other side that everything is non-nuclear, which opens a whole new can of worms about the value of keeping your word in international diplomacy. Ultimately, there needs to be a new discussion around strategic arms control between the major players that includes these types of systems. Now I am veering way out of the realm of physics, though...

 

[Doug H]

There was a vid of a Air to Air missile test where the (Mach ~3.5) missile disintegrated after a hard course change. Hypersonic maneuverability doesn’t seem promising until some new unknown properties of aerodynamics are discovered.

Conceivably a hypersonic missile could maneuver by slightly tilting it's nose cone, rather than using fins. If fins are to be used they would best be forward, rather than aft. High clock rate computer control what ever control surfaces are used. Triangular cross section, as opposed to circular, missile can "surf" on it's widest flat side for lift in any direction. To evade defenses the angle of course change is not as important as the amount of sideways acceleration. Thus a slower defensive missile would need an inversely proportionally greater "wing area" to effect sufficient course correction to match course changes of the incoming.
A defensive missile would probably more resemble a UAV. Probably have a solid propellant rocket motor. It need not collide with a hydpersonic incoming, but merely be able to release a cloud of shrapnel
in it's path. Thus it could return to base, or to the vicinity of ships which can recover it from the sea.

Going on the offensive is always applicable. Weapons are the tip of the spear, there is a lot of infrastructure to support any weapons operation even if you can't directly target the weapon. You kill the builders of the weapon, kill the operators, then bomb the logistics, crater the roads, etc.. This all has an effect on the amount of defensive countermeasures needed at the targeted end. Thinking one directional, in a defensive position, is how you lose in a fight to the death.

This raises the question of: would we want to attack the Chinese mainland and risk killing innocent civilians, just because the missile defense operations are located within or close to coastal cities, towns, etc? I can't imagine our prez-to-be warning the head of the CCP that his civilians are at risk if he attacks our Navy or our allies navies. [if I have crossed the line of acceptable subject matter, just say so]
Of course naval vessels deploying such missiles are permissible targets, and the occupied islands in the South China Sea.

 

[nsaspook]

This raises the question of: would we want to attack the Chinese mainland and risk killing innocent civilians, just because the missile defense operations are located within or close to coastal cities, towns, etc? I can't imagine our prez-to-be warning the head of the CCP that his civilians are at risk if he attacks our Navy or our allies navies. [if I have crossed the line of acceptable subject matter, just say so]
Of course naval vessels deploying such missiles are permissible targets, and the occupied islands in the South China Sea.

The simple answer to that historically was 'Yes' per the SIOP from the Kennedy era moving forward.
https://en.wikipedia.org/wiki/Single_Integrated_Operational_Plan